SL-20546: Merge branch 'DRTVWR-588-maint-W' into sl-20546.

58 files changed, 5113 insertions, 1877 deletions

diff --git a/indra/llcommon/CMakeLists.txt b/indra/llcommon/CMakeLists.txt
index ef4899978e..5f4ed2fffa 100644
--- a/indra/llcommon/CMakeLists.txt
+++ b/indra/llcommon/CMakeLists.txt
@@ -16,7 +16,10 @@ include(Tracy)
 
 
 set(llcommon_SOURCE_FILES
+    apply.cpp
+    commoncontrol.cpp
     indra_constants.cpp
+    lazyeventapi.cpp
     llallocator.cpp
     llallocator_heap_profile.cpp
     llapp.cpp
@@ -114,11 +117,16 @@ set(llcommon_SOURCE_FILES
 set(llcommon_HEADER_FILES
     CMakeLists.txt
 
+    always_return.h
+    apply.h
     chrono.h
     classic_callback.h
+    commoncontrol.h
     ctype_workaround.h
     fix_macros.h
+    function_types.h
     indra_constants.h
+    lazyeventapi.h
     linden_common.h
     llalignedarray.h
     llallocator.h
@@ -172,6 +180,7 @@ set(llcommon_HEADER_FILES
     llinitdestroyclass.h
     llinitparam.h
     llinstancetracker.h
+    llinstancetrackersubclass.h
     llkeybind.h
     llkeythrottle.h
     llleap.h
@@ -245,6 +254,7 @@ set(llcommon_HEADER_FILES
     stdtypes.h
     stringize.h
     threadpool.h
+    threadpool_fwd.h
     threadsafeschedule.h
     timer.h
     tuple.h
@@ -288,9 +298,11 @@ if (LL_TESTS)
 
   #set(TEST_DEBUG on)
   set(test_libs llcommon)
+  LL_ADD_INTEGRATION_TEST(apply "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(bitpack "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(classic_callback "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(commonmisc "" "${test_libs}")
+  LL_ADD_INTEGRATION_TEST(lazyeventapi "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(llbase64 "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(llcond "" "${test_libs}")
   LL_ADD_INTEGRATION_TEST(lldate "" "${test_libs}")
diff --git a/indra/llcommon/always_return.h b/indra/llcommon/always_return.h
new file mode 100644
index 0000000000..6b9f1fdeaf
--- /dev/null
+++ b/indra/llcommon/always_return.h
@@ -0,0 +1,124 @@
+/**
+ * @file   always_return.h
+ * @author Nat Goodspeed
+ * @date   2023-01-20
+ * @brief  Call specified callable with arbitrary arguments, but always return
+ *         specified type.
+ * 
+ * $LicenseInfo:firstyear=2023&license=viewerlgpl$
+ * Copyright (c) 2023, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_ALWAYS_RETURN_H)
+#define LL_ALWAYS_RETURN_H
+
+#include <type_traits>              // std::enable_if, std::is_convertible
+
+namespace LL
+{
+
+#if __cpp_lib_is_invocable >= 201703L // C++17
+    template <typename CALLABLE, typename... ARGS>
+    using invoke_result = std::invoke_result<CALLABLE, ARGS...>;
+#else  // C++14
+    template <typename CALLABLE, typename... ARGS>
+    using invoke_result = std::result_of<CALLABLE(ARGS...)>;
+#endif // C++14
+
+    /**
+     * AlwaysReturn<T>()(some_function, some_args...) calls
+     * some_function(some_args...). It is guaranteed to return a value of type
+     * T, regardless of the return type of some_function(). If some_function()
+     * returns a type convertible to T, it will convert and return that value.
+     * Otherwise (notably if some_function() is void), AlwaysReturn returns
+     * T().
+     *
+     * When some_function() returns a type not convertible to T, if
+     * you want AlwaysReturn to return some T value other than
+     * default-constructed T(), pass that value to AlwaysReturn's constructor.
+     */
+    template <typename DESIRED>
+    class AlwaysReturn
+    {
+    public:
+        /// pass explicit default value if other than default-constructed type
+        AlwaysReturn(const DESIRED& dft=DESIRED()): mDefault(dft) {}
+
+        // callable returns a type not convertible to DESIRED, return default
+        template <typename CALLABLE, typename... ARGS,
+                  typename std::enable_if<
+                      ! std::is_convertible<
+                          typename invoke_result<CALLABLE, ARGS...>::type,
+                          DESIRED
+                      >::value,
+                      bool
+                  >::type=true>
+        DESIRED operator()(CALLABLE&& callable, ARGS&&... args)
+        {
+            // discard whatever callable(args) returns
+            std::forward<CALLABLE>(callable)(std::forward<ARGS>(args)...);
+            return mDefault;
+        }
+
+        // callable returns a type convertible to DESIRED
+        template <typename CALLABLE, typename... ARGS,
+                  typename std::enable_if<
+                      std::is_convertible<
+                          typename invoke_result<CALLABLE, ARGS...>::type,
+                          DESIRED
+                      >::value,
+                      bool
+                  >::type=true>
+        DESIRED operator()(CALLABLE&& callable, ARGS&&... args)
+        {
+            return { std::forward<CALLABLE>(callable)(std::forward<ARGS>(args)...) };
+        }
+
+    private:
+        DESIRED mDefault;
+    };
+
+    /**
+     * always_return<T>(some_function, some_args...) calls
+     * some_function(some_args...). It is guaranteed to return a value of type
+     * T, regardless of the return type of some_function(). If some_function()
+     * returns a type convertible to T, it will convert and return that value.
+     * Otherwise (notably if some_function() is void), always_return() returns
+     * T().
+     */
+    template <typename DESIRED, typename CALLABLE, typename... ARGS>
+    DESIRED always_return(CALLABLE&& callable, ARGS&&... args)
+    {
+        return AlwaysReturn<DESIRED>()(std::forward<CALLABLE>(callable),
+                                       std::forward<ARGS>(args)...);
+    }
+
+    /**
+     * make_always_return<T>(some_function) returns a callable which, when
+     * called with appropriate some_function() arguments, always returns a
+     * value of type T, regardless of the return type of some_function(). If
+     * some_function() returns a type convertible to T, the returned callable
+     * will convert and return that value. Otherwise (notably if
+     * some_function() is void), the returned callable returns T().
+     *
+     * When some_function() returns a type not convertible to T, if
+     * you want the returned callable to return some T value other than
+     * default-constructed T(), pass that value to make_always_return() as its
+     * optional second argument.
+     */
+    template <typename DESIRED, typename CALLABLE>
+    auto make_always_return(CALLABLE&& callable, const DESIRED& dft=DESIRED())
+    {
+        return
+            [dft, callable = std::forward<CALLABLE>(callable)]
+            (auto&&... args)
+            {
+                return AlwaysReturn<DESIRED>(dft)(callable,
+                                                  std::forward<decltype(args)>(args)...);
+            };
+    }
+
+} // namespace LL
+
+#endif /* ! defined(LL_ALWAYS_RETURN_H) */
diff --git a/indra/llcommon/apply.cpp b/indra/llcommon/apply.cpp
new file mode 100644
index 0000000000..417e23d3b4
--- /dev/null
+++ b/indra/llcommon/apply.cpp
@@ -0,0 +1,29 @@
+/**
+ * @file   apply.cpp
+ * @author Nat Goodspeed
+ * @date   2022-12-21
+ * @brief  Implementation for apply.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "apply.h"
+// STL headers
+// std headers
+// external library headers
+// other Linden headers
+#include "stringize.h"
+
+void LL::apply_validate_size(size_t size, size_t arity)
+{
+    if (size != arity)
+    {
+        LLTHROW(apply_error(stringize("LL::apply(func(", arity, " args), "
+                                      "std::vector(", size, " elements))")));
+    }
+}
diff --git a/indra/llcommon/apply.h b/indra/llcommon/apply.h
index 7c58d63bc0..cf6161ed50 100644
--- a/indra/llcommon/apply.h
+++ b/indra/llcommon/apply.h
@@ -12,8 +12,11 @@
 #if ! defined(LL_APPLY_H)
 #define LL_APPLY_H
 
+#include "llexception.h"
 #include <boost/type_traits/function_traits.hpp>
+#include <functional>               // std::mem_fn()
 #include <tuple>
+#include <type_traits>              // std::is_member_pointer
 
 namespace LL
 {
@@ -54,20 +57,67 @@ namespace LL
         },                                                          \
         (ARGS))
 
-#if __cplusplus >= 201703L
+/*****************************************************************************
+*   invoke()
+*****************************************************************************/
+#if __cpp_lib_invoke >= 201411L
 
 // C++17 implementation
-using std::apply;
+using std::invoke;
+
+#else  // no std::invoke
+
+// Use invoke() to handle pointer-to-method:
+// derived from https://stackoverflow.com/a/38288251
+template<typename Fn, typename... Args, 
+         typename std::enable_if<std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto invoke(Fn&& f, Args&&... args)
+{
+    return std::mem_fn(std::forward<Fn>(f))(std::forward<Args>(args)...);
+}
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<!std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto invoke(Fn&& f, Args&&... args)
+{
+    return std::forward<Fn>(f)(std::forward<Args>(args)...);
+}
+
+#endif // no std::invoke
+
+/*****************************************************************************
+*   apply(function, tuple); apply(function, array)
+*****************************************************************************/
+#if __cpp_lib_apply >= 201603L
+
+// C++17 implementation
+// We don't just say 'using std::apply;' because that template is too general:
+// it also picks up the apply(function, vector) case, which we want to handle
+// below.
+template <typename CALLABLE, typename... ARGS>
+auto apply(CALLABLE&& func, const std::tuple<ARGS...>& args)
+{
+    return std::apply(std::forward<CALLABLE>(func), args);
+}
 
 #else // C++14
 
 // Derived from https://stackoverflow.com/a/20441189
 // and https://en.cppreference.com/w/cpp/utility/apply
-template <typename CALLABLE, typename TUPLE, std::size_t... I>
-auto apply_impl(CALLABLE&& func, TUPLE&& args, std::index_sequence<I...>)
+template <typename CALLABLE, typename... ARGS, std::size_t... I>
+auto apply_impl(CALLABLE&& func, const std::tuple<ARGS...>& args, std::index_sequence<I...>)
 {
+    // We accept const std::tuple& so a caller can construct an tuple on the
+    // fly. But std::get<I>(const tuple) adds a const qualifier to everything
+    // it extracts. Get a non-const ref to this tuple so we can extract
+    // without the extraneous const.
+    auto& non_const_args{ const_cast<std::tuple<ARGS...>&>(args) };
+
     // call func(unpacked args)
-    return std::forward<CALLABLE>(func)(std::move(std::get<I>(args))...);
+    return invoke(std::forward<CALLABLE>(func),
+                  std::forward<ARGS>(std::get<I>(non_const_args))...);
 }
 
 template <typename CALLABLE, typename... ARGS>
@@ -81,6 +131,8 @@ auto apply(CALLABLE&& func, const std::tuple<ARGS...>& args)
                       std::index_sequence_for<ARGS...>{});
 }
 
+#endif // C++14
+
 // per https://stackoverflow.com/a/57510428/5533635
 template <typename CALLABLE, typename T, size_t SIZE>
 auto apply(CALLABLE&& func, const std::array<T, SIZE>& args)
@@ -88,28 +140,92 @@ auto apply(CALLABLE&& func, const std::array<T, SIZE>& args)
     return apply(std::forward<CALLABLE>(func), std::tuple_cat(args));
 }
 
+/*****************************************************************************
+*   bind_front()
+*****************************************************************************/
+// To invoke a non-static member function with a tuple, you need a callable
+// that binds your member function with an instance pointer or reference.
+// std::bind_front() is perfect: std::bind_front(&cls::method, instance).
+// Unfortunately bind_front() only enters the standard library in C++20.
+#if __cpp_lib_bind_front >= 201907L
+
+// C++20 implementation
+using std::bind_front;
+
+#else  // no std::bind_front()
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<!std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto bind_front(Fn&& f, Args&&... args)
+{
+    // Don't use perfect forwarding for f or args: we must bind them for later.
+    return [f, pfx_args=std::make_tuple(args...)]
+        (auto&&... sfx_args)
+    {
+        // Use perfect forwarding for sfx_args because we use them as soon as
+        // we receive them.
+        return apply(
+            f,
+            std::tuple_cat(pfx_args,
+                           std::make_tuple(std::forward<decltype(sfx_args)>(sfx_args)...)));
+    };
+}
+
+template<typename Fn, typename... Args, 
+         typename std::enable_if<std::is_member_pointer<typename std::decay<Fn>::type>::value,
+                                 int>::type = 0 >
+auto bind_front(Fn&& f, Args&&... args)
+{
+    return bind_front(std::mem_fn(std::forward<Fn>(f)), std::forward<Args>(args)...);
+}
+
+#endif // C++20 with std::bind_front()
+
+/*****************************************************************************
+*   apply(function, std::vector)
+*****************************************************************************/
 // per https://stackoverflow.com/a/28411055/5533635
 template <typename CALLABLE, typename T, std::size_t... I>
 auto apply_impl(CALLABLE&& func, const std::vector<T>& args, std::index_sequence<I...>)
 {
+    return apply(std::forward<CALLABLE>(func),
+                 std::make_tuple(args[I]...));
+}
+
+// produce suitable error if apply(func, vector) is the wrong size for func()
+void apply_validate_size(size_t size, size_t arity);
+
+/// possible exception from apply() validation
+struct apply_error: public LLException
+{
+    apply_error(const std::string& what): LLException(what) {}
+};
+
+template <size_t ARITY, typename CALLABLE, typename T>
+auto apply_n(CALLABLE&& func, const std::vector<T>& args)
+{
+    apply_validate_size(args.size(), ARITY);
     return apply_impl(std::forward<CALLABLE>(func),
-                      std::make_tuple(std::forward<T>(args[I])...),
-                      I...);
+                      args,
+                      std::make_index_sequence<ARITY>());
 }
 
-// this goes beyond C++17 std::apply()
+/**
+ * apply(function, std::vector) goes beyond C++17 std::apply(). For this case
+ * @a function @emph cannot be variadic: the compiler must know at compile
+ * time how many arguments to pass. This isn't Python. (But see apply_n() to
+ * pass a specific number of args to a variadic function.)
+ */
 template <typename CALLABLE, typename T>
 auto apply(CALLABLE&& func, const std::vector<T>& args)
 {
+    // infer arity from the definition of func
     constexpr auto arity = boost::function_traits<CALLABLE>::arity;
-    assert(args.size() == arity);
-    return apply_impl(std::forward<CALLABLE>(func),
-                      args,
-                      std::make_index_sequence<arity>());
+    // now that we have a compile-time arity, apply_n() works
+    return apply_n<arity>(std::forward<CALLABLE>(func), args);
 }
 
-#endif // C++14
-
 } // namespace LL
 
 #endif /* ! defined(LL_APPLY_H) */
diff --git a/indra/llcommon/commoncontrol.cpp b/indra/llcommon/commoncontrol.cpp
new file mode 100644
index 0000000000..81e66baf8c
--- /dev/null
+++ b/indra/llcommon/commoncontrol.cpp
@@ -0,0 +1,106 @@
+/**
+ * @file   commoncontrol.cpp
+ * @author Nat Goodspeed
+ * @date   2022-06-08
+ * @brief  Implementation for commoncontrol.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "commoncontrol.h"
+// STL headers
+// std headers
+// external library headers
+// other Linden headers
+#include "llevents.h"
+#include "llsdutil.h"
+
+LLSD LL::CommonControl::access(const LLSD& params)
+{
+    // We can't actually introduce a link-time dependency on llxml, or on any
+    // global LLControlGroup (*koff* gSavedSettings *koff*) but we can issue a
+    // runtime query. If we're running as part of a viewer with
+    // LLViewerControlListener, we can use that to interact with any
+    // instantiated LLControGroup.
+    LLSD response;
+    {
+        LLEventStream reply("reply");
+        LLTempBoundListener connection = reply.listen("listener",
+                     [&response] (const LLSD& event)
+                     {
+                         response = event;
+                         return false;
+                     });
+        LLSD rparams{ params };
+        rparams["reply"] = reply.getName();
+        LLEventPumps::instance().obtain("LLViewerControl").post(rparams);
+    }
+    // LLViewerControlListener responds immediately. If it's listening at all,
+    // it will already have set response.
+    if (! response.isDefined())
+    {
+        LLTHROW(NoListener("No LLViewerControl listener instantiated"));
+    }
+    LLSD error{ response["error"] };
+    if (error.isDefined())
+    {
+        LLTHROW(ParamError(error));
+    }
+    response.erase("error");
+    response.erase("reqid");
+    return response;
+}
+
+/// set control group.key to defined default value
+LLSD LL::CommonControl::set_default(const std::string& group, const std::string& key)
+{
+    return access(llsd::map("op", "set",
+                            "group", group, "key", key))["value"];
+}
+
+/// set control group.key to specified value
+LLSD LL::CommonControl::set(const std::string& group, const std::string& key, const LLSD& value)
+{
+    return access(llsd::map("op", "set",
+                            "group", group, "key", key, "value", value))["value"];
+}
+
+/// toggle boolean control group.key
+LLSD LL::CommonControl::toggle(const std::string& group, const std::string& key)
+{
+    return access(llsd::map("op", "toggle",
+                            "group", group, "key", key))["value"];
+}
+
+/// get the definition for control group.key, (! isDefined()) if bad
+/// ["name"], ["type"], ["value"], ["comment"]
+LLSD LL::CommonControl::get_def(const std::string& group, const std::string& key)
+{
+    return access(llsd::map("op", "get",
+                            "group", group, "key", key));
+}
+
+/// get the value of control group.key
+LLSD LL::CommonControl::get(const std::string& group, const std::string& key)
+{
+    return access(llsd::map("op", "get",
+                            "group", group, "key", key))["value"];
+}
+
+/// get defined groups
+std::vector<std::string> LL::CommonControl::get_groups()
+{
+    auto groups{ access(llsd::map("op", "groups"))["groups"] };
+    return { groups.beginArray(), groups.endArray() };
+}
+
+/// get definitions for all variables in group
+LLSD LL::CommonControl::get_vars(const std::string& group)
+{
+    return access(llsd::map("op", "vars", "group", group))["vars"];
+}
diff --git a/indra/llcommon/commoncontrol.h b/indra/llcommon/commoncontrol.h
new file mode 100644
index 0000000000..07d4a45ac5
--- /dev/null
+++ b/indra/llcommon/commoncontrol.h
@@ -0,0 +1,75 @@
+/**
+ * @file   commoncontrol.h
+ * @author Nat Goodspeed
+ * @date   2022-06-08
+ * @brief  Access LLViewerControl LLEventAPI, if process has one.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_COMMONCONTROL_H)
+#define LL_COMMONCONTROL_H
+
+#include <vector>
+#include "llexception.h"
+#include "llsd.h"
+
+namespace LL
+{
+    class CommonControl
+    {
+    public:
+        struct Error: public LLException
+        {
+            Error(const std::string& what): LLException(what) {}
+        };
+
+        /// Exception thrown if there's no LLViewerControl LLEventAPI
+        struct NoListener: public Error
+        {
+            NoListener(const std::string& what): Error(what) {}
+        };
+
+        struct ParamError: public Error
+        {
+            ParamError(const std::string& what): Error(what) {}
+        };
+
+        /// set control group.key to defined default value
+        static
+        LLSD set_default(const std::string& group, const std::string& key);
+
+        /// set control group.key to specified value
+        static
+        LLSD set(const std::string& group, const std::string& key, const LLSD& value);
+
+        /// toggle boolean control group.key
+        static
+        LLSD toggle(const std::string& group, const std::string& key);
+
+        /// get the definition for control group.key, (! isDefined()) if bad
+        /// ["name"], ["type"], ["value"], ["comment"]
+        static
+        LLSD get_def(const std::string& group, const std::string& key);
+
+        /// get the value of control group.key
+        static
+        LLSD get(const std::string& group, const std::string& key);
+
+        /// get defined groups
+        static
+        std::vector<std::string> get_groups();
+
+        /// get definitions for all variables in group
+        static
+        LLSD get_vars(const std::string& group);
+
+    private:
+        static
+        LLSD access(const LLSD& params);
+    };
+} // namespace LL
+
+#endif /* ! defined(LL_COMMONCONTROL_H) */
diff --git a/indra/llcommon/function_types.h b/indra/llcommon/function_types.h
new file mode 100644
index 0000000000..3f42f6d640
--- /dev/null
+++ b/indra/llcommon/function_types.h
@@ -0,0 +1,49 @@
+/**
+ * @file   function_types.h
+ * @author Nat Goodspeed
+ * @date   2023-01-20
+ * @brief  Extend boost::function_types to examine boost::function and
+ *         std::function
+ * 
+ * $LicenseInfo:firstyear=2023&license=viewerlgpl$
+ * Copyright (c) 2023, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_FUNCTION_TYPES_H)
+#define LL_FUNCTION_TYPES_H
+
+#include <boost/function.hpp>
+#include <boost/function_types/function_arity.hpp>
+#include <functional>
+
+namespace LL
+{
+
+    template <typename F>
+    struct function_arity_impl
+    {
+        static constexpr auto value = boost::function_types::function_arity<F>::value;
+    };
+
+    template <typename F>
+    struct function_arity_impl<std::function<F>>
+    {
+        static constexpr auto value = function_arity_impl<F>::value;
+    };
+
+    template <typename F>
+    struct function_arity_impl<boost::function<F>>
+    {
+        static constexpr auto value = function_arity_impl<F>::value;
+    };
+
+    template <typename F>
+    struct function_arity
+    {
+        static constexpr auto value = function_arity_impl<typename std::decay<F>::type>::value;
+    };
+
+} // namespace LL
+
+#endif /* ! defined(LL_FUNCTION_TYPES_H) */
diff --git a/indra/llcommon/lazyeventapi.cpp b/indra/llcommon/lazyeventapi.cpp
new file mode 100644
index 0000000000..028af9f33f
--- /dev/null
+++ b/indra/llcommon/lazyeventapi.cpp
@@ -0,0 +1,72 @@
+/**
+ * @file   lazyeventapi.cpp
+ * @author Nat Goodspeed
+ * @date   2022-06-17
+ * @brief  Implementation for lazyeventapi.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "lazyeventapi.h"
+// STL headers
+// std headers
+#include <algorithm>                // std::find_if
+// external library headers
+// other Linden headers
+#include "llevents.h"
+#include "llsdutil.h"
+
+LL::LazyEventAPIBase::LazyEventAPIBase(
+    const std::string& name, const std::string& desc, const std::string& field)
+{
+    // populate embedded LazyEventAPIParams instance
+    mParams.name = name;
+    mParams.desc = desc;
+    mParams.field = field;
+    // mParams.init and mOperations are populated by subsequent add() calls.
+
+    // Our raison d'etre: register as an LLEventPumps::PumpFactory
+    // so obtain() will notice any request for this name and call us.
+    // Of course, our subclass constructor must finish running (making add()
+    // calls) before mParams will be fully populated, but we expect that to
+    // happen well before the first LLEventPumps::obtain(name) call.
+    mRegistered = LLEventPumps::instance().registerPumpFactory(
+        name,
+        [this](const std::string& name){ return construct(name); });
+}
+
+LL::LazyEventAPIBase::~LazyEventAPIBase()
+{
+    // If our constructor's registerPumpFactory() call was unsuccessful, that
+    // probably means somebody else claimed the name first. If that's the
+    // case, do NOT unregister their name out from under them!
+    // If this is a static instance being destroyed at process shutdown,
+    // LLEventPumps will probably have been cleaned up already.
+    if (mRegistered && ! LLEventPumps::wasDeleted())
+    {
+        // unregister the callback to this doomed instance
+        LLEventPumps::instance().unregisterPumpFactory(mParams.name);
+    }
+}
+
+LLSD LL::LazyEventAPIBase::getMetadata(const std::string& name) const
+{
+    // Since mOperations is a vector rather than a map, just search.
+    auto found = std::find_if(mOperations.begin(), mOperations.end(),
+                              [&name](const auto& namedesc)
+                              { return (namedesc.first == name); });
+    if (found == mOperations.end())
+        return {};
+
+    // LLEventDispatcher() supplements the returned metadata in different
+    // ways, depending on metadata provided to the specific add() method.
+    // Don't try to emulate all that. At some point we might consider more
+    // closely unifying LLEventDispatcher machinery with LazyEventAPI, but for
+    // now this will have to do.
+    return llsd::map("name", found->first, "desc", found->second);
+}
diff --git a/indra/llcommon/lazyeventapi.h b/indra/llcommon/lazyeventapi.h
new file mode 100644
index 0000000000..e36831270b
--- /dev/null
+++ b/indra/llcommon/lazyeventapi.h
@@ -0,0 +1,205 @@
+/**
+ * @file   lazyeventapi.h
+ * @author Nat Goodspeed
+ * @date   2022-06-16
+ * @brief  Declaring a static module-scope LazyEventAPI registers a specific
+ *         LLEventAPI for future on-demand instantiation.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_LAZYEVENTAPI_H)
+#define LL_LAZYEVENTAPI_H
+
+#include "apply.h"
+#include "lleventapi.h"
+#include "llinstancetracker.h"
+#include <boost/signals2/signal.hpp>
+#include <string>
+#include <tuple>
+#include <utility>                  // std::pair
+#include <vector>
+
+namespace LL
+{
+    /**
+     * Bundle params we want to pass to LLEventAPI's protected constructor. We
+     * package them this way so a subclass constructor can simply forward an
+     * opaque reference to the LLEventAPI constructor.
+     */
+    // This is a class instead of a plain struct mostly so when we forward-
+    // declare it we don't have to remember the distinction.
+    class LazyEventAPIParams
+    {
+    public:
+        // package the parameters used by the normal LLEventAPI constructor
+        std::string name, desc, field;
+        // bundle LLEventAPI::add() calls collected by LazyEventAPI::add(), so
+        // the special LLEventAPI constructor we engage can "play back" those
+        // add() calls
+        boost::signals2::signal<void(LLEventAPI*)> init;
+    };
+
+    /**
+     * LazyEventAPIBase implements most of the functionality of LazyEventAPI
+     * (q.v.), but we need the LazyEventAPI template subclass so we can accept
+     * the specific LLEventAPI subclass type.
+     */
+    // No LLInstanceTracker key: we don't need to find a specific instance,
+    // LLLeapListener just needs to be able to enumerate all instances.
+    class LazyEventAPIBase: public LLInstanceTracker<LazyEventAPIBase>
+    {
+    public:
+        LazyEventAPIBase(const std::string& name, const std::string& desc,
+                         const std::string& field);
+        virtual ~LazyEventAPIBase();
+
+        // Do not copy or move: once constructed, LazyEventAPIBase must stay
+        // put: we bind its instance pointer into a callback.
+        LazyEventAPIBase(const LazyEventAPIBase&) = delete;
+        LazyEventAPIBase(LazyEventAPIBase&&) = delete;
+        LazyEventAPIBase& operator=(const LazyEventAPIBase&) = delete;
+        LazyEventAPIBase& operator=(LazyEventAPIBase&&) = delete;
+
+        // capture add() calls we want to play back on LLEventAPI construction
+        template <typename... ARGS>
+        void add(const std::string& name, const std::string& desc, ARGS&&... rest)
+        {
+            // capture the metadata separately
+            mOperations.push_back(std::make_pair(name, desc));
+            // Use connect_extended() so the lambda is passed its own
+            // connection.
+
+            // apply() can't accept a template per se; it needs a particular
+            // specialization. Specialize out here to work around a clang bug:
+            // https://github.com/llvm/llvm-project/issues/41999
+            auto func{ &LazyEventAPIBase::add_trampoline
+                       <const std::string&, const std::string&, ARGS...> };
+            // We can't bind an unexpanded parameter pack into a lambda --
+            // shame really. Instead, capture all our args as a std::tuple and
+            // then, in the lambda, use apply() to pass to add_trampoline().
+            auto args{ std::make_tuple(name, desc, std::forward<ARGS>(rest)...) };
+
+            mParams.init.connect_extended(
+                [func, args]
+                (const boost::signals2::connection& conn, LLEventAPI* instance)
+                {
+                    // we only need this connection once
+                    conn.disconnect();
+                    // apply() expects a tuple specifying ALL the arguments,
+                    // so prepend instance.
+                    apply(func, std::tuple_cat(std::make_tuple(instance), args));
+                });
+        }
+
+        // The following queries mimic the LLEventAPI / LLEventDispatcher
+        // query API.
+
+        // Get the string name of the subject LLEventAPI
+        std::string getName() const { return mParams.name; }
+        // Get the documentation string
+        std::string getDesc() const { return mParams.desc; }
+        // Retrieve the LLSD key we use for dispatching
+        std::string getDispatchKey() const { return mParams.field; }
+
+        // operations
+        using NameDesc = std::pair<std::string, std::string>;
+
+    private:
+        // metadata that might be queried by LLLeapListener
+        std::vector<NameDesc> mOperations;
+
+    public:
+        using const_iterator = decltype(mOperations)::const_iterator;
+        const_iterator begin() const { return mOperations.begin(); }
+        const_iterator end()   const { return mOperations.end(); }
+        LLSD getMetadata(const std::string& name) const;
+
+    protected:
+        // Params with which to instantiate the companion LLEventAPI subclass
+        LazyEventAPIParams mParams;
+
+    private:
+        // true if we successfully registered our LLEventAPI on construction
+        bool mRegistered;
+
+        // actually instantiate the companion LLEventAPI subclass
+        virtual LLEventPump* construct(const std::string& name) = 0;
+
+        // Passing an overloaded function to any function that accepts an
+        // arbitrary callable is a PITB because you have to specify the
+        // correct overload. What we want is for the compiler to select the
+        // correct overload, based on the carefully-wrought enable_ifs in
+        // LLEventDispatcher. This (one and only) add_trampoline() method
+        // exists solely to pass to LL::apply(). Once add_trampoline() is
+        // called with the expanded arguments, we hope the compiler will Do
+        // The Right Thing in selecting the correct LLEventAPI::add()
+        // overload.
+        template <typename... ARGS>
+        static
+        void add_trampoline(LLEventAPI* instance, ARGS&&... args)
+        {
+            instance->add(std::forward<ARGS>(args)...);
+        }
+    };
+
+    /**
+     * LazyEventAPI provides a way to register a particular LLEventAPI to be
+     * instantiated on demand, that is, when its name is passed to
+     * LLEventPumps::obtain().
+     *
+     * Derive your listener from LLEventAPI as usual, with its various
+     * operation methods, but code your constructor to accept
+     * <tt>(const LL::LazyEventAPIParams& params)</tt>
+     * and forward that reference to (the protected)
+     * <tt>LLEventAPI(const LL::LazyEventAPIParams&)</tt> constructor.
+     *
+     * Then derive your listener registrar from
+     * <tt>LazyEventAPI<your LLEventAPI subclass></tt>. The constructor should
+     * look very like a traditional LLEventAPI constructor:
+     *
+     * * pass (name, desc [, field]) to LazyEventAPI's constructor
+     * * in the body, make a series of add() calls referencing your LLEventAPI
+     *   subclass methods.
+     *
+     * You may use any LLEventAPI::add() methods, that is, any
+     * LLEventDispatcher::add() methods. But the target methods you pass to
+     * add() must belong to your LLEventAPI subclass, not the LazyEventAPI
+     * subclass.
+     *
+     * Declare a static instance of your LazyEventAPI listener registrar
+     * class. When it's constructed at static initialization time, it will
+     * register your LLEventAPI subclass with LLEventPumps. It will also
+     * collect metadata for the LLEventAPI and its operations to provide to
+     * LLLeapListener's introspection queries.
+     *
+     * When someone later calls LLEventPumps::obtain() to post an event to
+     * your LLEventAPI subclass, obtain() will instantiate it using
+     * LazyEventAPI's name, desc, field and add() calls.
+     */
+    template <class EVENTAPI>
+    class LazyEventAPI: public LazyEventAPIBase
+    {
+    public:
+        // for subclass constructor to reference handler methods
+        using listener = EVENTAPI;
+
+        LazyEventAPI(const std::string& name, const std::string& desc,
+                     const std::string& field="op"):
+            // Forward ctor params to LazyEventAPIBase
+            LazyEventAPIBase(name, desc, field)
+        {}
+
+    private:
+        LLEventPump* construct(const std::string& /*name*/) override
+        {
+            // base class has carefully assembled LazyEventAPIParams embedded
+            // in this instance, just pass to LLEventAPI subclass constructor
+            return new EVENTAPI(mParams);
+        }
+    };
+} // namespace LL
+
+#endif /* ! defined(LL_LAZYEVENTAPI_H) */
diff --git a/indra/llcommon/llapr.cpp b/indra/llcommon/llapr.cpp
index 69466df2d1..575c524219 100644
--- a/indra/llcommon/llapr.cpp
+++ b/indra/llcommon/llapr.cpp
@@ -528,6 +528,7 @@ S32 LLAPRFile::seek(apr_file_t* file_handle, apr_seek_where_t where, S32 offset)
 //static
 S32 LLAPRFile::readEx(const std::string& filename, void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	//*****************************************
 	LLAPRFilePoolScope scope(pool);
 	apr_file_t* file_handle = open(filename, scope.getVolatileAPRPool(), APR_READ|APR_BINARY); 
@@ -572,6 +573,7 @@ S32 LLAPRFile::readEx(const std::string& filename, void *buf, S32 offset, S32 nb
 //static
 S32 LLAPRFile::writeEx(const std::string& filename, void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	apr_int32_t flags = APR_CREATE|APR_WRITE|APR_BINARY;
 	if (offset < 0)
 	{
diff --git a/indra/llcommon/llassettype.cpp b/indra/llcommon/llassettype.cpp
index 4c84223dad..6492d888c1 100644
--- a/indra/llcommon/llassettype.cpp
+++ b/indra/llcommon/llassettype.cpp
@@ -96,6 +96,7 @@ LLAssetDictionary::LLAssetDictionary()
 	addEntry(LLAssetType::AT_WIDGET,            new AssetEntry("WIDGET",            "widget",   "widget",           false,      false,      false));
 	addEntry(LLAssetType::AT_PERSON,            new AssetEntry("PERSON",            "person",   "person",           false,      false,      false));
 	addEntry(LLAssetType::AT_SETTINGS,          new AssetEntry("SETTINGS",          "settings", "settings blob",    true,       true,       true));
+	addEntry(LLAssetType::AT_MATERIAL,          new AssetEntry("MATERIAL",          "material", "render material",  true,       true,       true));
 	addEntry(LLAssetType::AT_UNKNOWN,           new AssetEntry("UNKNOWN",           "invalid",  NULL,               false,      false,      false));
     addEntry(LLAssetType::AT_NONE,              new AssetEntry("NONE",              "-1",		NULL,		  		FALSE,		FALSE,		FALSE));
 
diff --git a/indra/llcommon/llassettype.h b/indra/llcommon/llassettype.h
index 652c548d59..e8df8574f7 100644
--- a/indra/llcommon/llassettype.h
+++ b/indra/llcommon/llassettype.h
@@ -127,8 +127,9 @@ public:
         AT_RESERVED_6 = 55,
 
         AT_SETTINGS = 56,   // Collection of settings
-            
-		AT_COUNT = 57,
+        AT_MATERIAL = 57,   // Render Material
+
+		AT_COUNT = 58,
 
 			// +*********************************************************+
 			// |  TO ADD AN ELEMENT TO THIS ENUM:                        |
diff --git a/indra/llcommon/llcallstack.h b/indra/llcommon/llcallstack.h
index 5acf04a49f..d5a2b7b157 100644
--- a/indra/llcommon/llcallstack.h
+++ b/indra/llcommon/llcallstack.h
@@ -79,9 +79,9 @@ struct LLContextStatus
 
 LL_COMMON_API std::ostream& operator<<(std::ostream& s, const LLContextStatus& context_status);
 
-#define dumpStack(tag) \
-    if (debugLoggingEnabled(tag)) \
-    { \
-        LLCallStack cs; \
-        LL_DEBUGS(tag) << "STACK:\n" << "====================\n" << cs << "====================" << LL_ENDL; \
-    }
+#define dumpStack(tag)                          \
+    LL_DEBUGS(tag) << "STACK:\n"                \
+                   << "====================\n"  \
+                   << LLCallStack()             \
+                   << "===================="    \
+                   << LL_ENDL;
diff --git a/indra/llcommon/llcommon.cpp b/indra/llcommon/llcommon.cpp
index d2c4e66160..6e988260a9 100644
--- a/indra/llcommon/llcommon.cpp
+++ b/indra/llcommon/llcommon.cpp
@@ -37,12 +37,13 @@ thread_local bool gProfilerEnabled = false;
 
 #if (TRACY_ENABLE)
 // Override new/delete for tracy memory profiling
-void *operator new(size_t size)
+
+void* ll_tracy_new(size_t size)
 {
     void* ptr;
     if (gProfilerEnabled)
     {
-        LL_PROFILE_ZONE_SCOPED_CATEGORY_MEMORY;
+        //LL_PROFILE_ZONE_SCOPED_CATEGORY_MEMORY;
         ptr = (malloc)(size);
     }
     else
@@ -57,12 +58,22 @@ void *operator new(size_t size)
     return ptr;
 }
 
-void operator delete(void *ptr) noexcept
+void* operator new(size_t size)
+{
+    return ll_tracy_new(size);
+}
+
+void* operator new[](std::size_t count)
+{
+    return ll_tracy_new(count);
+}
+
+void ll_tracy_delete(void* ptr)
 {
     TracyFree(ptr);
     if (gProfilerEnabled)
     {
-        LL_PROFILE_ZONE_SCOPED_CATEGORY_MEMORY;
+        //LL_PROFILE_ZONE_SCOPED_CATEGORY_MEMORY;
         (free)(ptr);
     }
     else
@@ -71,6 +82,16 @@ void operator delete(void *ptr) noexcept
     }
 }
 
+void operator delete(void *ptr) noexcept
+{
+    ll_tracy_delete(ptr);
+}
+
+void operator delete[](void* ptr) noexcept
+{
+    ll_tracy_delete(ptr);
+}
+
 // C-style malloc/free can't be so easily overridden, so we define tracy versions and use
 // a pre-processor #define in linden_common.h to redirect to them. The parens around the native
 // functions below prevents recursive substitution by the preprocessor.
diff --git a/indra/llcommon/llcoros.cpp b/indra/llcommon/llcoros.cpp
index 191c1a9037..3deed2e199 100644
--- a/indra/llcommon/llcoros.cpp
+++ b/indra/llcommon/llcoros.cpp
@@ -278,6 +278,7 @@ std::string LLCoros::launch(const std::string& prefix, const callable_t& callabl
     catch (std::bad_alloc&)
     {
         // Out of memory on stack allocation?
+        printActiveCoroutines();
         LL_ERRS("LLCoros") << "Bad memory allocation in LLCoros::launch(" << prefix << ")!" << LL_ENDL;
     }
 
diff --git a/indra/llcommon/llerror.cpp b/indra/llcommon/llerror.cpp
index 05e719b494..414515854a 100644
--- a/indra/llcommon/llerror.cpp
+++ b/indra/llcommon/llerror.cpp
@@ -1603,20 +1603,6 @@ namespace LLError
     }
 }
 
-bool debugLoggingEnabled(const std::string& tag)
-{
-    LLMutexTrylock lock(getMutex<LOG_MUTEX>(), 5);
-    if (!lock.isLocked())
-    {
-        return false;
-    }
-
-    SettingsConfigPtr s = Globals::getInstance()->getSettingsConfig();
-    LLError::ELevel level = LLError::LEVEL_DEBUG;
-    bool res = checkLevelMap(s->mTagLevelMap, tag, level);
-    return res;
-}
-
 void crashdriver(void (*callback)(int*))
 {
     // The LLERROR_CRASH macro used to have inline code of the form:
diff --git a/indra/llcommon/llerror.h b/indra/llcommon/llerror.h
index 624a5fb37a..05dd88ee51 100644
--- a/indra/llcommon/llerror.h
+++ b/indra/llcommon/llerror.h
@@ -82,9 +82,11 @@ const int LL_ERR_NOERR = 0;
 
 #ifdef SHOW_ASSERT
 #define llassert(func)			llassert_always_msg(func, #func)
+#define llassert_msg(func, msg)	llassert_always_msg(func, msg)
 #define llverify(func)			llassert_always_msg(func, #func)
 #else
 #define llassert(func)
+#define llassert_msg(func, msg)
 #define llverify(func)			do {if (func) {}} while(0)
 #endif
 
@@ -462,8 +464,31 @@ typedef LLError::NoClassInfo _LL_CLASS_TO_LOG;
 		LLError::CallSite& _site(_sites[which]);                        \
 		lllog_test_()
 
-// Check at run-time whether logging is enabled, without generating output
+/*
+// Check at run-time whether logging is enabled, without generating output.
+Resist the temptation to add a function like this because it incurs the
+expense of locking and map-searching every time control reaches it.
 bool debugLoggingEnabled(const std::string& tag);
+
+Instead of:
+
+if debugLoggingEnabled("SomeTag")
+{
+    // ... presumably expensive operation ...
+    LL_DEBUGS("SomeTag") << ... << LL_ENDL;
+}
+
+Use this:
+
+LL_DEBUGS("SomeTag");
+// ... presumably expensive operation ...
+LL_CONT << ...;
+LL_ENDL;
+
+LL_DEBUGS("SomeTag") performs the locking and map-searching ONCE, then caches
+the result in a static variable.
+*/ 
+
 // used by LLERROR_CRASH
 void crashdriver(void (*)(int*));
 
diff --git a/indra/llcommon/lleventapi.cpp b/indra/llcommon/lleventapi.cpp
index ff5459c1eb..3d46ef1034 100644
--- a/indra/llcommon/lleventapi.cpp
+++ b/indra/llcommon/lleventapi.cpp
@@ -35,6 +35,7 @@
 // external library headers
 // other Linden headers
 #include "llerror.h"
+#include "lazyeventapi.h"
 
 LLEventAPI::LLEventAPI(const std::string& name, const std::string& desc, const std::string& field):
     lbase(name, field),
@@ -43,6 +44,13 @@ LLEventAPI::LLEventAPI(const std::string& name, const std::string& desc, const s
 {
 }
 
+LLEventAPI::LLEventAPI(const LL::LazyEventAPIParams& params):
+    LLEventAPI(params.name, params.desc, params.field)
+{
+    // call initialization functions with our brand-new instance pointer
+    params.init(this);
+}
+
 LLEventAPI::~LLEventAPI()
 {
 }
diff --git a/indra/llcommon/lleventapi.h b/indra/llcommon/lleventapi.h
index 5991fe8fd5..25f6becd8b 100644
--- a/indra/llcommon/lleventapi.h
+++ b/indra/llcommon/lleventapi.h
@@ -35,6 +35,11 @@
 #include "llinstancetracker.h"
 #include <string>
 
+namespace LL
+{
+    class LazyEventAPIParams;
+}
+
 /**
  * LLEventAPI not only provides operation dispatch functionality, inherited
  * from LLDispatchListener -- it also gives us event API introspection.
@@ -65,19 +70,6 @@ public:
     std::string getDesc() const { return mDesc; }
 
     /**
-     * Publish only selected add() methods from LLEventDispatcher.
-     * Every LLEventAPI add() @em must have a description string.
-     */
-    template <typename CALLABLE>
-    void add(const std::string& name,
-             const std::string& desc,
-             CALLABLE callable,
-             const LLSD& required=LLSD())
-    {
-        LLEventDispatcher::add(name, desc, callable, required);
-    }
-
-    /**
      * Instantiate a Response object in any LLEventAPI subclass method that
      * wants to guarantee a reply (if requested) will be sent on exit from the
      * method. The reply will be sent if request.has(@a replyKey), default
@@ -150,16 +142,20 @@ public:
          * @endcode
          */
         LLSD& operator[](const LLSD::String& key) { return mResp[key]; }
-		
-		 /**
-		 * set the response to the given data
-		 */
-		void setResponse(LLSD const & response){ mResp = response; }
+
+         /**
+         * set the response to the given data
+         */
+        void setResponse(LLSD const & response){ mResp = response; }
 
         LLSD mResp, mReq;
         LLSD::String mKey;
     };
 
+protected:
+    // constructor used only by subclasses registered by LazyEventAPI
+    LLEventAPI(const LL::LazyEventAPIParams&);
+
 private:
     std::string mDesc;
 };
diff --git a/indra/llcommon/lleventdispatcher.cpp b/indra/llcommon/lleventdispatcher.cpp
index cd0ab6bc29..da96de18f7 100644
--- a/indra/llcommon/lleventdispatcher.cpp
+++ b/indra/llcommon/lleventdispatcher.cpp
@@ -40,71 +40,13 @@
 // other Linden headers
 #include "llevents.h"
 #include "llerror.h"
+#include "llexception.h"
 #include "llsdutil.h"
 #include "stringize.h"
+#include <iomanip>                  // std::quoted()
 #include <memory>                   // std::auto_ptr
 
 /*****************************************************************************
-*   LLSDArgsSource
-*****************************************************************************/
-/**
- * Store an LLSD array, producing its elements one at a time. Die with LL_ERRS
- * if the consumer requests more elements than the array contains.
- */
-class LL_COMMON_API LLSDArgsSource
-{
-public:
-    LLSDArgsSource(const std::string function, const LLSD& args);
-    ~LLSDArgsSource();
-
-    LLSD next();
-
-    void done() const;
-
-private:
-    std::string _function;
-    LLSD _args;
-    LLSD::Integer _index;
-};
-
-LLSDArgsSource::LLSDArgsSource(const std::string function, const LLSD& args):
-    _function(function),
-    _args(args),
-    _index(0)
-{
-    if (! (_args.isUndefined() || _args.isArray()))
-    {
-        LL_ERRS("LLSDArgsSource") << _function << " needs an args array instead of "
-                                  << _args << LL_ENDL;
-    }
-}
-
-LLSDArgsSource::~LLSDArgsSource()
-{
-    done();
-}
-
-LLSD LLSDArgsSource::next()
-{
-    if (_index >= _args.size())
-    {
-        LL_ERRS("LLSDArgsSource") << _function << " requires more arguments than the "
-                                  << _args.size() << " provided: " << _args << LL_ENDL;
-    }
-    return _args[_index++];
-}
-
-void LLSDArgsSource::done() const
-{
-    if (_index < _args.size())
-    {
-        LL_WARNS("LLSDArgsSource") << _function << " only consumed " << _index
-                                   << " of the " << _args.size() << " arguments provided: "
-                                   << _args << LL_ENDL;
-    }
-}
-
-/*****************************************************************************
 *   LLSDArgsMapper
 *****************************************************************************/
 /**
@@ -156,19 +98,26 @@ void LLSDArgsSource::done() const
  * - Holes are filled with the default values.
  * - Any remaining holes constitute an error.
  */
-class LL_COMMON_API LLSDArgsMapper
+class LL_COMMON_API LLEventDispatcher::LLSDArgsMapper
 {
 public:
     /// Accept description of function: function name, param names, param
     /// default values
-    LLSDArgsMapper(const std::string& function, const LLSD& names, const LLSD& defaults);
+    LLSDArgsMapper(LLEventDispatcher* parent, const std::string& function,
+                   const LLSD& names, const LLSD& defaults);
 
-    /// Given arguments map, return LLSD::Array of parameter values, or LL_ERRS.
+    /// Given arguments map, return LLSD::Array of parameter values, or
+    /// trigger error.
     LLSD map(const LLSD& argsmap) const;
 
 private:
     static std::string formatlist(const LLSD&);
+    template <typename... ARGS>
+    [[noreturn]] void callFail(ARGS&&... args) const;
 
+    // store a plain dumb back-pointer because we don't have to manage the
+    // parent LLEventDispatcher's lifespan
+    LLEventDispatcher* _parent;
     // The function-name string is purely descriptive. We want error messages
     // to be able to indicate which function's LLSDArgsMapper has the problem.
     std::string _function;
@@ -187,15 +136,18 @@ private:
     FilledVector _has_dft;
 };
 
-LLSDArgsMapper::LLSDArgsMapper(const std::string& function,
-                               const LLSD& names, const LLSD& defaults):
+LLEventDispatcher::LLSDArgsMapper::LLSDArgsMapper(LLEventDispatcher* parent,
+                                                  const std::string& function,
+                                                  const LLSD& names,
+                                                  const LLSD& defaults):
+    _parent(parent),
     _function(function),
     _names(names),
     _has_dft(names.size())
 {
     if (! (_names.isUndefined() || _names.isArray()))
     {
-        LL_ERRS("LLSDArgsMapper") << function << " names must be an array, not " << names << LL_ENDL;
+        callFail(" names must be an array, not ", names);
     }
     auto nparams(_names.size());
     // From _names generate _indexes.
@@ -218,8 +170,7 @@ LLSDArgsMapper::LLSDArgsMapper(const std::string& function,
         // defaults is a (possibly empty) array. Right-align it with names.
         if (ndefaults > nparams)
         {
-            LL_ERRS("LLSDArgsMapper") << function << " names array " << names
-                                      << " shorter than defaults array " << defaults << LL_ENDL;
+            callFail(" names array ", names, " shorter than defaults array ", defaults);
         }
 
         // Offset by which we slide defaults array right to right-align with
@@ -256,23 +207,20 @@ LLSDArgsMapper::LLSDArgsMapper(const std::string& function,
         }
         if (bogus.size())
         {
-            LL_ERRS("LLSDArgsMapper") << function << " defaults specified for nonexistent params "
-                                      << formatlist(bogus) << LL_ENDL;
+            callFail(" defaults specified for nonexistent params ", formatlist(bogus));
         }
     }
     else
     {
-        LL_ERRS("LLSDArgsMapper") << function << " defaults must be a map or an array, not "
-                                  << defaults << LL_ENDL;
+        callFail(" defaults must be a map or an array, not ", defaults);
     }
 }
 
-LLSD LLSDArgsMapper::map(const LLSD& argsmap) const
+LLSD LLEventDispatcher::LLSDArgsMapper::map(const LLSD& argsmap) const
 {
     if (! (argsmap.isUndefined() || argsmap.isMap() || argsmap.isArray()))
     {
-        LL_ERRS("LLSDArgsMapper") << _function << " map() needs a map or array, not "
-                                  << argsmap << LL_ENDL;
+        callFail(" map() needs a map or array, not ", argsmap);
     }
     // Initialize the args array. Indexing a non-const LLSD array grows it
     // to appropriate size, but we don't want to resize this one on each
@@ -369,15 +317,14 @@ LLSD LLSDArgsMapper::map(const LLSD& argsmap) const
     // by argsmap, that's a problem.
     if (unfilled.size())
     {
-        LL_ERRS("LLSDArgsMapper") << _function << " missing required arguments "
-                                  << formatlist(unfilled) << " from " << argsmap << LL_ENDL;
+        callFail(" missing required arguments ", formatlist(unfilled), " from ", argsmap);
     }
 
     // done
     return args;
 }
 
-std::string LLSDArgsMapper::formatlist(const LLSD& list)
+std::string LLEventDispatcher::LLSDArgsMapper::formatlist(const LLSD& list)
 {
     std::ostringstream out;
     const char* delim = "";
@@ -390,23 +337,44 @@ std::string LLSDArgsMapper::formatlist(const LLSD& list)
     return out.str();
 }
 
-LLEventDispatcher::LLEventDispatcher(const std::string& desc, const std::string& key):
-    mDesc(desc),
-    mKey(key)
+template <typename... ARGS>
+[[noreturn]] void LLEventDispatcher::LLSDArgsMapper::callFail(ARGS&&... args) const
 {
+    _parent->callFail<LLEventDispatcher::DispatchError>
+        (_function, std::forward<ARGS>(args)...);
 }
 
+/*****************************************************************************
+*   LLEventDispatcher
+*****************************************************************************/
+LLEventDispatcher::LLEventDispatcher(const std::string& desc, const std::string& key):
+    LLEventDispatcher(desc, key, "args")
+{}
+
+LLEventDispatcher::LLEventDispatcher(const std::string& desc, const std::string& key,
+                                     const std::string& argskey):
+    mDesc(desc),
+    mKey(key),
+    mArgskey(argskey)
+{}
+
 LLEventDispatcher::~LLEventDispatcher()
 {
 }
 
+LLEventDispatcher::DispatchEntry::DispatchEntry(LLEventDispatcher* parent, const std::string& desc):
+    mParent(parent),
+    mDesc(desc)
+{}
+
 /**
  * DispatchEntry subclass used for callables accepting(const LLSD&)
  */
 struct LLEventDispatcher::LLSDDispatchEntry: public LLEventDispatcher::DispatchEntry
 {
-    LLSDDispatchEntry(const std::string& desc, const Callable& func, const LLSD& required):
-        DispatchEntry(desc),
+    LLSDDispatchEntry(LLEventDispatcher* parent, const std::string& desc,
+                      const Callable& func, const LLSD& required):
+        DispatchEntry(parent, desc),
         mFunc(func),
         mRequired(required)
     {}
@@ -414,22 +382,21 @@ struct LLEventDispatcher::LLSDDispatchEntry: public LLEventDispatcher::DispatchE
     Callable mFunc;
     LLSD mRequired;
 
-    virtual void call(const std::string& desc, const LLSD& event) const
+    LLSD call(const std::string& desc, const LLSD& event, bool, const std::string&) const override
     {
         // Validate the syntax of the event itself.
         std::string mismatch(llsd_matches(mRequired, event));
         if (! mismatch.empty())
         {
-            LL_ERRS("LLEventDispatcher") << desc << ": bad request: " << mismatch << LL_ENDL;
+            callFail(desc, ": bad request: ", mismatch);
         }
         // Event syntax looks good, go for it!
-        mFunc(event);
+        return mFunc(event);
     }
 
-    virtual LLSD addMetadata(LLSD meta) const
+    LLSD getMetadata() const override
     {
-        meta["required"] = mRequired;
-        return meta;
+        return llsd::map("required", mRequired);
     }
 };
 
@@ -439,17 +406,27 @@ struct LLEventDispatcher::LLSDDispatchEntry: public LLEventDispatcher::DispatchE
  */
 struct LLEventDispatcher::ParamsDispatchEntry: public LLEventDispatcher::DispatchEntry
 {
-    ParamsDispatchEntry(const std::string& desc, const invoker_function& func):
-        DispatchEntry(desc),
+    ParamsDispatchEntry(LLEventDispatcher* parent, const std::string& name,
+                        const std::string& desc, const invoker_function& func):
+        DispatchEntry(parent, desc),
+        mName(name),
         mInvoker(func)
     {}
 
+    std::string mName;
     invoker_function mInvoker;
 
-    virtual void call(const std::string& desc, const LLSD& event) const
+    LLSD call(const std::string&, const LLSD& event, bool, const std::string&) const override
     {
-        LLSDArgsSource src(desc, event);
-        mInvoker(boost::bind(&LLSDArgsSource::next, boost::ref(src)));
+        try
+        {
+            return mInvoker(event);
+        }
+        catch (const LL::apply_error& err)
+        {
+            // could hit runtime errors with LL::apply()
+            callFail(err.what());
+        }
     }
 };
 
@@ -459,23 +436,62 @@ struct LLEventDispatcher::ParamsDispatchEntry: public LLEventDispatcher::Dispatc
  */
 struct LLEventDispatcher::ArrayParamsDispatchEntry: public LLEventDispatcher::ParamsDispatchEntry
 {
-    ArrayParamsDispatchEntry(const std::string& desc, const invoker_function& func,
+    ArrayParamsDispatchEntry(LLEventDispatcher* parent, const std::string& name,
+                             const std::string& desc, const invoker_function& func,
                              LLSD::Integer arity):
-        ParamsDispatchEntry(desc, func),
+        ParamsDispatchEntry(parent, name, desc, func),
         mArity(arity)
     {}
 
     LLSD::Integer mArity;
 
-    virtual LLSD addMetadata(LLSD meta) const
+    LLSD call(const std::string& desc, const LLSD& event, bool fromMap, const std::string& argskey) const override
+    {
+//      std::string context { stringize(desc, "(", event, ") with argskey ", std::quoted(argskey), ": ") };
+        // Whether we try to extract arguments from 'event' depends on whether
+        // the LLEventDispatcher consumer called one of the (name, event)
+        // methods (! fromMap) or one of the (event) methods (fromMap). If we
+        // were called with (name, event), the passed event must itself be
+        // suitable to pass to the registered callable, no args extraction
+        // required or even attempted. Only if called with plain (event) do we
+        // consider extracting args from that event. Initially assume 'event'
+        // itself contains the arguments.
+        LLSD args{ event };
+        if (fromMap)
+        {
+            if (! mArity)
+            {
+                // When the target function is nullary, and we're called from
+                // an (event) method, just ignore the rest of the map entries.
+                args.clear();
+            }
+            else
+            {
+                // We only require/retrieve argskey if the target function
+                // isn't nullary. For all others, since we require an LLSD
+                // array, we must have an argskey.
+                if (argskey.empty())
+                {
+                    callFail("LLEventDispatcher has no args key");
+                }
+                if ((! event.has(argskey)))
+                {
+                    callFail("missing required key ", std::quoted(argskey));
+                }
+                args = event[argskey];
+            }
+        }
+        return ParamsDispatchEntry::call(desc, args, fromMap, argskey);
+    }
+
+    LLSD getMetadata() const override
     {
         LLSD array(LLSD::emptyArray());
         // Resize to number of arguments required
         if (mArity)
             array[mArity - 1] = LLSD();
         llassert_always(array.size() == mArity);
-        meta["required"] = array;
-        return meta;
+        return llsd::map("required", array);
     }
 };
 
@@ -485,11 +501,11 @@ struct LLEventDispatcher::ArrayParamsDispatchEntry: public LLEventDispatcher::Pa
  */
 struct LLEventDispatcher::MapParamsDispatchEntry: public LLEventDispatcher::ParamsDispatchEntry
 {
-    MapParamsDispatchEntry(const std::string& name, const std::string& desc,
-                           const invoker_function& func,
+    MapParamsDispatchEntry(LLEventDispatcher* parent, const std::string& name,
+                           const std::string& desc, const invoker_function& func,
                            const LLSD& params, const LLSD& defaults):
-        ParamsDispatchEntry(desc, func),
-        mMapper(name, params, defaults),
+        ParamsDispatchEntry(parent, name, desc, func),
+        mMapper(parent, name, params, defaults),
         mRequired(LLSD::emptyMap())
     {
         // Build the set of all param keys, then delete the ones that are
@@ -532,18 +548,27 @@ struct LLEventDispatcher::MapParamsDispatchEntry: public LLEventDispatcher::Para
     LLSD mRequired;
     LLSD mOptional;
 
-    virtual void call(const std::string& desc, const LLSD& event) const
+    LLSD call(const std::string& desc, const LLSD& event, bool fromMap, const std::string& argskey) const override
     {
-        // Just convert from LLSD::Map to LLSD::Array using mMapper, then pass
-        // to base-class call() method.
-        ParamsDispatchEntry::call(desc, mMapper.map(event));
+        // by default, pass the whole event as the arguments map
+        LLSD args{ event };
+        // Were we called by one of the (event) methods (instead of the (name,
+        // event) methods), do we have an argskey, and does the incoming event
+        // have that key?
+        if (fromMap && (! argskey.empty()) && event.has(argskey))
+        {
+            // if so, extract the value of argskey from the incoming event,
+            // and use that as the arguments map
+            args = event[argskey];
+        }
+        // Now convert args from LLSD map to LLSD array using mMapper, then
+        // pass to base-class call() method.
+        return ParamsDispatchEntry::call(desc, mMapper.map(args), fromMap, argskey);
     }
 
-    virtual LLSD addMetadata(LLSD meta) const
+    LLSD getMetadata() const override
     {
-        meta["required"] = mRequired;
-        meta["optional"] = mOptional;
-        return meta;
+        return llsd::map("required", mRequired, "optional", mOptional);
     }
 };
 
@@ -552,9 +577,9 @@ void LLEventDispatcher::addArrayParamsDispatchEntry(const std::string& name,
                                                     const invoker_function& invoker,
                                                     LLSD::Integer arity)
 {
-    mDispatch.insert(
-        DispatchMap::value_type(name, DispatchMap::mapped_type(
-                                    new ArrayParamsDispatchEntry(desc, invoker, arity))));
+    mDispatch.emplace(
+        name,
+        new ArrayParamsDispatchEntry(this, "", desc, invoker, arity));
 }
 
 void LLEventDispatcher::addMapParamsDispatchEntry(const std::string& name,
@@ -563,25 +588,25 @@ void LLEventDispatcher::addMapParamsDispatchEntry(const std::string& name,
                                                   const LLSD& params,
                                                   const LLSD& defaults)
 {
-    mDispatch.insert(
-        DispatchMap::value_type(name, DispatchMap::mapped_type(
-                                    new MapParamsDispatchEntry(name, desc, invoker, params, defaults))));
+    // Pass instance info as well as this entry name for error messages.
+    mDispatch.emplace(
+        name,
+        new MapParamsDispatchEntry(this, "", desc, invoker, params, defaults));
 }
 
 /// Register a callable by name
-void LLEventDispatcher::add(const std::string& name, const std::string& desc,
-                            const Callable& callable, const LLSD& required)
+void LLEventDispatcher::addLLSD(const std::string& name, const std::string& desc,
+                                const Callable& callable, const LLSD& required)
 {
-    mDispatch.insert(
-        DispatchMap::value_type(name, DispatchMap::mapped_type(
-                                    new LLSDDispatchEntry(desc, callable, required))));
+    mDispatch.emplace(name, new LLSDDispatchEntry(this, desc, callable, required));
 }
 
-void LLEventDispatcher::addFail(const std::string& name, const std::string& classname) const
+void LLEventDispatcher::addFail(const std::string& name, const char* classname) const
 {
     LL_ERRS("LLEventDispatcher") << "LLEventDispatcher(" << mDesc << ")::add(" << name
-                                 << "): " << classname << " is not a subclass "
-                                 << "of LLEventDispatcher" << LL_ENDL;
+                                 << "): " << LLError::Log::demangle(classname)
+                                 << " is not a subclass of LLEventDispatcher"
+                                 << LL_ENDL;
 }
 
 /// Unregister a callable
@@ -596,48 +621,105 @@ bool LLEventDispatcher::remove(const std::string& name)
     return true;
 }
 
-/// Call a registered callable with an explicitly-specified name. If no
-/// such callable exists, die with LL_ERRS.
-void LLEventDispatcher::operator()(const std::string& name, const LLSD& event) const
+/// Call a registered callable with an explicitly-specified name. It is an
+/// error if no such callable exists.
+LLSD LLEventDispatcher::operator()(const std::string& name, const LLSD& event) const
 {
-    if (! try_call(name, event))
-    {
-        LL_ERRS("LLEventDispatcher") << "LLEventDispatcher(" << mDesc << "): '" << name
-                                     << "' not found" << LL_ENDL;
-    }
+    return try_call(std::string(), name, event);
 }
 
-/// Extract the @a key value from the incoming @a event, and call the
-/// callable whose name is specified by that map @a key. If no such
-/// callable exists, die with LL_ERRS.
-void LLEventDispatcher::operator()(const LLSD& event) const
+bool LLEventDispatcher::try_call(const std::string& name, const LLSD& event) const
 {
-    // This could/should be implemented in terms of the two-arg overload.
-    // However -- we can produce a more informative error message.
-    std::string name(event[mKey]);
-    if (! try_call(name, event))
+    try
     {
-        LL_ERRS("LLEventDispatcher") << "LLEventDispatcher(" << mDesc << "): bad " << mKey
-                                     << " value '" << name << "'" << LL_ENDL;
+        try_call(std::string(), name, event);
+        return true;
+    }
+    // Note that we don't catch the generic DispatchError, only the specific
+    // DispatchMissing. try_call() only promises to return false if the
+    // specified callable name isn't found -- not for general errors.
+    catch (const DispatchMissing&)
+    {
+        return false;
     }
 }
 
+/// Extract the @a key value from the incoming @a event, and call the callable
+/// whose name is specified by that map @a key. It is an error if no such
+/// callable exists.
+LLSD LLEventDispatcher::operator()(const LLSD& event) const
+{
+    return try_call(mKey, event[mKey], event);
+}
+
 bool LLEventDispatcher::try_call(const LLSD& event) const
 {
-    return try_call(event[mKey], event);
+    try
+    {
+        try_call(mKey, event[mKey], event);
+        return true;
+    }
+    catch (const DispatchMissing&)
+    {
+        return false;
+    }
 }
 
-bool LLEventDispatcher::try_call(const std::string& name, const LLSD& event) const
+LLSD LLEventDispatcher::try_call(const std::string& key, const std::string& name,
+                                 const LLSD& event) const
 {
+    if (name.empty())
+    {
+        if (key.empty())
+        {
+            callFail<DispatchError>("attempting to call with no name");
+        }
+        else
+        {
+            callFail<DispatchError>("no ", key);
+        }
+    }
+
     DispatchMap::const_iterator found = mDispatch.find(name);
     if (found == mDispatch.end())
     {
-        return false;
+        // Here we were passed a non-empty name, but there's no registered
+        // callable with that name. This is the one case in which we throw
+        // DispatchMissing instead of the generic DispatchError.
+        // Distinguish the public method by which our caller reached here:
+        // key.empty() means the name was passed explicitly, non-empty means
+        // we extracted the name from the incoming event using that key.
+        if (key.empty())
+        {
+            callFail<DispatchMissing>(std::quoted(name), " not found");
+        }
+        else
+        {
+            callFail<DispatchMissing>("bad ", key, " value ", std::quoted(name));
+        }
     }
+
     // Found the name, so it's plausible to even attempt the call.
-    found->second->call(STRINGIZE("LLEventDispatcher(" << mDesc << ") calling '" << name << "'"),
-                        event);
-    return true;                    // tell caller we were able to call
+    const char* delim = (key.empty()? "" : "=");
+    // append either "[key=name]" or just "[name]"
+    SetState transient(this, '[', key, delim, name, ']');
+    return found->second->call("", event, (! key.empty()), mArgskey);
+}
+
+template <typename EXCEPTION, typename... ARGS>
+//static
+[[noreturn]] void LLEventDispatcher::sCallFail(ARGS&&... args)
+{
+    auto error = stringize(std::forward<ARGS>(args)...);
+    LL_WARNS("LLEventDispatcher") << error << LL_ENDL;
+    LLTHROW(EXCEPTION(error));
+}
+
+template <typename EXCEPTION, typename... ARGS>
+[[noreturn]] void LLEventDispatcher::callFail(ARGS&&... args) const
+{
+    // Describe this instance in addition to the error itself.
+    sCallFail<EXCEPTION>(*this, ": ", std::forward<ARGS>(args)...);
 }
 
 LLSD LLEventDispatcher::getMetadata(const std::string& name) const
@@ -647,26 +729,243 @@ LLSD LLEventDispatcher::getMetadata(const std::string& name) const
     {
         return LLSD();
     }
-    LLSD meta;
+    LLSD meta{ found->second->getMetadata() };
     meta["name"] = name;
     meta["desc"] = found->second->mDesc;
-    return found->second->addMetadata(meta);
+    return meta;
+}
+
+std::ostream& operator<<(std::ostream& out, const LLEventDispatcher& self)
+{
+    // If we're a subclass of LLEventDispatcher, e.g. LLEventAPI, report that.
+    // Also report whatever transient state is active.
+    return out << LLError::Log::classname(self) << '(' << self.mDesc << ')'
+               << self.getState();
 }
 
-LLDispatchListener::LLDispatchListener(const std::string& pumpname, const std::string& key):
-    LLEventDispatcher(pumpname, key),
-    mPump(pumpname, true),          // allow tweaking for uniqueness
-    mBoundListener(mPump.listen("self", boost::bind(&LLDispatchListener::process, this, _1)))
+std::string LLEventDispatcher::getState() const
 {
+    // default value of fiber_specific_ptr is nullptr, and ~SetState() reverts
+    // to that; infer empty string
+    if (! mState.get())
+        return {};
+    else
+        return *mState;
 }
 
-bool LLDispatchListener::process(const LLSD& event)
+bool LLEventDispatcher::setState(SetState&, const std::string& state) const
 {
-    (*this)(event);
+    // If SetState is instantiated at multiple levels of function call, ignore 
+    // the lower-level call because the outer call presumably provides more
+    // context.
+    if (mState.get())
+        return false;
+
+    // Pass us empty string (a la ~SetState()) to reset to nullptr, else take
+    // a heap copy of the passed state string so we can delete it on
+    // subsequent reset().
+    mState.reset(state.empty()? nullptr : new std::string(state));
+    return true;
+}
+
+/*****************************************************************************
+*   LLDispatchListener
+*****************************************************************************/
+std::string LLDispatchListener::mReplyKey{ "reply" };
+
+bool LLDispatchListener::process(const LLSD& event) const
+{
+    // Decide what to do based on the incoming value of the specified dispatch
+    // key.
+    LLSD name{ event[getDispatchKey()] };
+    if (name.isMap())
+    {
+        call_map(name, event);
+    }
+    else if (name.isArray())
+    {
+        call_array(name, event);
+    }
+    else
+    {
+        call_one(name, event);
+    }
     return false;
 }
 
-LLEventDispatcher::DispatchEntry::DispatchEntry(const std::string& desc):
-    mDesc(desc)
-{}
+void LLDispatchListener::call_one(const LLSD& name, const LLSD& event) const
+{
+    LLSD result;
+    try
+    {
+        result = (*this)(event);
+    }
+    catch (const DispatchError& err)
+    {
+        if (! event.has(mReplyKey))
+        {
+            // Without a reply key, let the exception propagate.
+            throw;
+        }
+
+        // Here there was an error and the incoming event has mReplyKey. Reply
+        // with a map containing an "error" key explaining the problem.
+        return reply(llsd::map("error", err.what()), event);
+    }
 
+    // We seem to have gotten a valid result. But we don't know whether the
+    // registered callable is void or non-void. If it's void,
+    // LLEventDispatcher returned isUndefined(). Otherwise, try to send it
+    // back to our invoker.
+    if (result.isDefined())
+    {
+        if (! result.isMap())
+        {
+            // wrap the result in a map as the "data" key
+            result = llsd::map("data", result);
+        }
+        reply(result, event);
+    }
+}
+
+void LLDispatchListener::call_map(const LLSD& reqmap, const LLSD& event) const
+{
+    // LLSD map containing returned values
+    LLSD result;
+    // cache dispatch key
+    std::string key{ getDispatchKey() };
+    // collect any error messages here
+    std::ostringstream errors;
+    const char* delim = "";
+
+    for (const auto& pair : llsd::inMap(reqmap))
+    {
+        const LLSD::String& name{ pair.first };
+        const LLSD& args{ pair.second };
+        try
+        {
+            // in case of errors, tell user the dispatch key, the fact that
+            // we're processing a request map and the current key in that map
+            SetState(this, '[', key, '[', name, "]]");
+            // With this form, capture return value even if undefined:
+            // presence of the key in the response map can be used to detect
+            // which request keys succeeded.
+            result[name] = (*this)(name, args);
+        }
+        catch (const std::exception& err)
+        {
+            // Catch not only DispatchError, but any C++ exception thrown by
+            // the target callable. Collect exception name and message in
+            // 'errors'.
+            errors << delim << LLError::Log::classname(err) << ": " << err.what();
+            delim = "\n";
+        }
+    }
+
+    // so, were there any errors?
+    std::string error = errors.str();
+    if (! error.empty())
+    {
+        if (! event.has(mReplyKey))
+        {
+            // can't send reply, throw
+            sCallFail<DispatchError>(error);
+        }
+        else
+        {
+            // reply key present
+            result["error"] = error;
+        }
+    }
+
+    reply(result, event);
+}
+
+void LLDispatchListener::call_array(const LLSD& reqarray, const LLSD& event) const
+{
+    // LLSD array containing returned values
+    LLSD results;
+    // cache the dispatch key
+    std::string key{ getDispatchKey() };
+    // arguments array, if present -- const because, if it's shorter than
+    // reqarray, we don't want to grow it
+    const LLSD argsarray{ event[getArgsKey()] };
+    // error message, if any
+    std::string error;
+
+    // classic index loop because we need the index
+    for (size_t i = 0, size = reqarray.size(); i < size; ++i)
+    {
+        const auto& reqentry{ reqarray[i] };
+        std::string name;
+        LLSD args;
+        if (reqentry.isString())
+        {
+            name = reqentry.asString();
+            args = argsarray[i];
+        }
+        else if (reqentry.isArray() && reqentry.size() == 2 && reqentry[0].isString())
+        {
+            name = reqentry[0].asString();
+            args = reqentry[1];
+        }
+        else
+        {
+            // reqentry isn't in either of the documented forms
+            error = stringize(*this, ": ", getDispatchKey(), '[', i, "] ",
+                              reqentry, " unsupported");
+            break;
+        }
+
+        // reqentry is one of the valid forms, got name and args
+        try
+        {
+            // in case of errors, tell user the dispatch key, the fact that
+            // we're processing a request array, the current entry in that
+            // array and the corresponding callable name
+            SetState(this, '[', key, '[', i, "]=", name, ']');
+            // With this form, capture return value even if undefined
+            results.append((*this)(name, args));
+        }
+        catch (const std::exception& err)
+        {
+            // Catch not only DispatchError, but any C++ exception thrown by
+            // the target callable. Report the exception class as well as the
+            // error string.
+            error = stringize(LLError::Log::classname(err), ": ", err.what());
+            break;
+        }
+    }
+
+    LLSD result;
+    // was there an error?
+    if (! error.empty())
+    {
+        if (! event.has(mReplyKey))
+        {
+            // can't send reply, throw
+            sCallFail<DispatchError>(error);
+        }
+        else
+        {
+            // reply key present
+            result["error"] = error;
+        }
+    }
+
+    // wrap the results array as response map "data" key, as promised
+    if (results.isDefined())
+    {
+        result["data"] = results;
+    }
+
+    reply(result, event);
+}
+
+void LLDispatchListener::reply(const LLSD& reply, const LLSD& request) const
+{
+    // Call sendReply() unconditionally: sendReply() itself tests whether the
+    // specified reply key is present in the incoming request, and does
+    // nothing if there's no such key.
+    sendReply(reply, request, mReplyKey);
+}
diff --git a/indra/llcommon/lleventdispatcher.h b/indra/llcommon/lleventdispatcher.h
index 9e1244ef5b..a82bc7a69b 100644
--- a/indra/llcommon/lleventdispatcher.h
+++ b/indra/llcommon/lleventdispatcher.h
@@ -27,55 +27,26 @@
  * 
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
- *
- * The invoker machinery that constructs a boost::fusion argument list for use
- * with boost::fusion::invoke() is derived from
- * http://www.boost.org/doc/libs/1_45_0/libs/function_types/example/interpreter.hpp
- * whose license information is copied below:
- *
- * "(C) Copyright Tobias Schwinger
- *
- * Use modification and distribution are subject to the boost Software License,
- * Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt)."
  */
 
 #if ! defined(LL_LLEVENTDISPATCHER_H)
 #define LL_LLEVENTDISPATCHER_H
 
-// nil is too generic a term to be allowed to be a global macro. In
-// particular, boost::fusion defines a 'class nil' (properly encapsulated in a
-// namespace) that a global 'nil' macro breaks badly.
-#if defined(nil)
-// Capture the value of the macro 'nil', hoping int is an appropriate type.
-static const auto nil_(nil);
-// Now forget the macro.
-#undef nil
-// Finally, reintroduce 'nil' as a properly-scoped alias for the previously-
-// defined const 'nil_'. Make it static since otherwise it produces duplicate-
-// symbol link errors later.
-static const auto& nil(nil_);
-#endif
-
-#include <string>
-#include <boost/shared_ptr.hpp>
-#include <boost/function.hpp>
-#include <boost/bind.hpp>
-#include <boost/iterator/transform_iterator.hpp>
-#include <boost/utility/enable_if.hpp>
+#include <boost/fiber/fss.hpp>
+#include <boost/function_types/is_member_function_pointer.hpp>
 #include <boost/function_types/is_nonmember_callable_builtin.hpp>
-#include <boost/function_types/parameter_types.hpp>
-#include <boost/function_types/function_arity.hpp>
-#include <boost/type_traits/remove_cv.hpp>
-#include <boost/type_traits/remove_reference.hpp>
-#include <boost/fusion/include/push_back.hpp>
-#include <boost/fusion/include/cons.hpp>
-#include <boost/fusion/include/invoke.hpp>
-#include <boost/mpl/begin.hpp>
-#include <boost/mpl/end.hpp>
-#include <boost/mpl/next.hpp>
-#include <boost/mpl/deref.hpp>
+#include <boost/hof/is_invocable.hpp> // until C++17, when we get std::is_invocable
+#include <boost/iterator/transform_iterator.hpp>
+#include <functional>               // std::function
+#include <memory>                   // std::unique_ptr
+#include <string>
 #include <typeinfo>
+#include <type_traits>
+#include <utility>                  // std::pair
+#include "always_return.h"
+#include "function_types.h"         // LL::function_arity
 #include "llevents.h"
+#include "llptrto.h"
 #include "llsdutil.h"
 
 class LLSD;
@@ -89,15 +60,27 @@ class LLSD;
 class LL_COMMON_API LLEventDispatcher
 {
 public:
+    /**
+     * Pass description and the LLSD key used by try_call(const LLSD&) and
+     * operator()(const LLSD&) to extract the name of the registered callable
+     * to invoke.
+     */
     LLEventDispatcher(const std::string& desc, const std::string& key);
+    /**
+     * Pass description, the LLSD key used by try_call(const LLSD&) and
+     * operator()(const LLSD&) to extract the name of the registered callable
+     * to invoke, and the LLSD key used by try_call(const LLSD&) and
+     * operator()(const LLSD&) to extract arguments LLSD.
+     */
+    LLEventDispatcher(const std::string& desc, const std::string& key,
+                      const std::string& argskey);
     virtual ~LLEventDispatcher();
 
     /// @name Register functions accepting(const LLSD&)
     //@{
 
-    /// Accept any C++ callable with the right signature, typically a
-    /// boost::bind() expression
-    typedef boost::function<void(const LLSD&)> Callable;
+    /// Accept any C++ callable with the right signature
+    typedef std::function<LLSD(const LLSD&)> Callable;
 
     /**
      * Register a @a callable by @a name. The passed @a callable accepts a
@@ -109,27 +92,54 @@ public:
     void add(const std::string& name,
              const std::string& desc,
              const Callable& callable,
-             const LLSD& required=LLSD());
+             const LLSD& required=LLSD())
+    {
+        addLLSD(name, desc, callable, required);
+    }
 
-    /**
-     * The case of a free function (or static method) accepting(const LLSD&)
-     * could also be intercepted by the arbitrary-args overload below. Ensure
-     * that it's directed to the Callable overload above instead.
-     */
+    template <typename CALLABLE,
+              typename=typename std::enable_if<
+                  boost::hof::is_invocable<CALLABLE, LLSD>::value
+             >::type>
     void add(const std::string& name,
              const std::string& desc,
-             void (*f)(const LLSD&),
+             CALLABLE&& callable,
              const LLSD& required=LLSD())
     {
-        add(name, desc, Callable(f), required);
+        addLLSD(
+            name,
+            desc,
+            Callable(LL::make_always_return<LLSD>(std::forward<CALLABLE>(callable))),
+            required);
     }
 
     /**
      * Special case: a subclass of this class can pass an unbound member
      * function pointer (of an LLEventDispatcher subclass) without explicitly
-     * specifying the <tt>boost::bind()</tt> expression. The passed @a method
+     * specifying a <tt>std::bind()</tt> expression. The passed @a method
      * accepts a single LLSD value, presumably containing other parameters.
      */
+    template <typename R, class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(const LLSD&),
+             const LLSD& required=LLSD())
+    {
+        addMethod<CLASS>(name, desc, method, required);
+    }
+
+    /// Overload for both const and non-const methods. The passed @a method
+    /// accepts a single LLSD value, presumably containing other parameters.
+    template <typename R, class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(const LLSD&) const,
+             const LLSD& required=LLSD())
+    {
+        addMethod<CLASS>(name, desc, method, required);
+    }
+
+    // because the compiler can't match a method returning void to the above
     template <class CLASS>
     void add(const std::string& name,
              const std::string& desc,
@@ -150,6 +160,128 @@ public:
         addMethod<CLASS>(name, desc, method, required);
     }
 
+    // non-const nullary method
+    template <typename R, class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)())
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const nullary method
+    template <typename R, class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)() const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // non-const nullary method returning void
+    template <class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)())
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const nullary method returning void
+    template <class CLASS>
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)() const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // non-const unary method (but method accepting LLSD should use the other add())
+    // enable_if usage per https://stackoverflow.com/a/39913395/5533635
+    template <typename R, class CLASS, typename ARG,
+              typename = typename std::enable_if<
+                  ! std::is_same<typename std::decay<ARG>::type, LLSD>::value
+             >::type>    
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(ARG))
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const unary method (but method accepting LLSD should use the other add())
+    template <typename R, class CLASS, typename ARG,
+              typename = typename std::enable_if<
+                  ! std::is_same<typename std::decay<ARG>::type, LLSD>::value
+             >::type>    
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(ARG) const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // non-const unary method returning void
+    // enable_if usage per https://stackoverflow.com/a/39913395/5533635
+    template <class CLASS, typename ARG,
+              typename = typename std::enable_if<
+                  ! std::is_same<typename std::decay<ARG>::type, LLSD>::value
+             >::type>    
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)(ARG))
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const unary method returning void
+    template <class CLASS, typename ARG,
+              typename = typename std::enable_if<
+                  ! std::is_same<typename std::decay<ARG>::type, LLSD>::value
+             >::type>    
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)(ARG) const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // non-const binary (or more) method
+    template <typename R, class CLASS, typename ARG0, typename ARG1, typename... ARGS>    
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(ARG0, ARG1, ARGS...))
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const binary (or more) method
+    template <typename R, class CLASS, typename ARG0, typename ARG1, typename... ARGS>    
+    void add(const std::string& name,
+             const std::string& desc,
+             R (CLASS::*method)(ARG0, ARG1, ARGS...) const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // non-const binary (or more) method returning void
+    template <class CLASS, typename ARG0, typename ARG1, typename... ARGS>    
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)(ARG0, ARG1, ARGS...))
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
+    // const binary (or more) method returning void
+    template <class CLASS, typename ARG0, typename ARG1, typename... ARGS>    
+    void add(const std::string& name,
+             const std::string& desc,
+             void (CLASS::*method)(ARG0, ARG1, ARGS...) const)
+    {
+        addVMethod<CLASS>(name, desc, method);
+    }
+
     //@}
 
     /// @name Register functions with arbitrary param lists
@@ -159,51 +291,43 @@ public:
      * Register a free function with arbitrary parameters. (This also works
      * for static class methods.)
      *
-     * @note This supports functions with up to about 6 parameters -- after
-     * that you start getting dismaying compile errors in which
-     * boost::fusion::joint_view is mentioned a surprising number of times.
-     *
      * When calling this name, pass an LLSD::Array. Each entry in turn will be
      * converted to the corresponding parameter type using LLSDParam.
      */
-    template<typename Function>
-    typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function>
-                               >::type add(const std::string& name,
-                                           const std::string& desc,
-                                           Function f);
+    template <typename CALLABLE,
+              typename=typename std::enable_if<
+                  ! boost::hof::is_invocable<CALLABLE, LLSD>()
+             >::type>
+    void add(const std::string& name,
+             const std::string& desc,
+             CALLABLE&& f)
+    {
+        addV(name, desc, f);
+    }
 
     /**
      * Register a nonstatic class method with arbitrary parameters.
      *
-     * @note This supports functions with up to about 6 parameters -- after
-     * that you start getting dismaying compile errors in which
-     * boost::fusion::joint_view is mentioned a surprising number of times.
-     *
      * To cover cases such as a method on an LLSingleton we don't yet want to
      * instantiate, instead of directly storing an instance pointer, accept a
      * nullary callable returning a pointer/reference to the desired class
-     * instance. If you already have an instance in hand,
-     * boost::lambda::var(instance) or boost::lambda::constant(instance_ptr)
-     * produce suitable callables.
+     * instance.
      *
      * When calling this name, pass an LLSD::Array. Each entry in turn will be
      * converted to the corresponding parameter type using LLSDParam.
      */
-    template<typename Method, typename InstanceGetter>
-    typename boost::enable_if< boost::function_types::is_member_function_pointer<Method>
-                               >::type add(const std::string& name,
-                                           const std::string& desc,
-                                           Method f,
-                                           const InstanceGetter& getter);
+    template<typename Method, typename InstanceGetter,
+             typename = typename std::enable_if<
+                 boost::function_types::is_member_function_pointer<Method>::value &&
+                 ! std::is_convertible<InstanceGetter, LLSD>::value
+             >::type>
+    void add(const std::string& name, const std::string& desc, Method f,
+             const InstanceGetter& getter);
 
     /**
      * Register a free function with arbitrary parameters. (This also works
      * for static class methods.)
      *
-     * @note This supports functions with up to about 6 parameters -- after
-     * that you start getting dismaying compile errors in which
-     * boost::fusion::joint_view is mentioned a surprising number of times.
-     *
      * Pass an LLSD::Array of parameter names, and optionally another
      * LLSD::Array of default parameter values, a la LLSDArgsMapper.
      *
@@ -211,21 +335,17 @@ public:
      * an LLSD::Array using LLSDArgsMapper and then convert each entry in turn
      * to the corresponding parameter type using LLSDParam.
      */
-    template<typename Function>
-    typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function>
-                               >::type add(const std::string& name,
-                                           const std::string& desc,
-                                           Function f,
-                                           const LLSD& params,
-                                           const LLSD& defaults=LLSD());
+    template<typename Function,
+             typename = typename std::enable_if<
+                 boost::function_types::is_nonmember_callable_builtin<Function>::value &&
+                 ! boost::hof::is_invocable<Function, LLSD>::value
+             >::type>
+    void add(const std::string& name, const std::string& desc, Function f,
+             const LLSD& params, const LLSD& defaults=LLSD());
 
     /**
      * Register a nonstatic class method with arbitrary parameters.
      *
-     * @note This supports functions with up to about 6 parameters -- after
-     * that you start getting dismaying compile errors in which
-     * boost::fusion::joint_view is mentioned a surprising number of times.
-     *
      * To cover cases such as a method on an LLSingleton we don't yet want to
      * instantiate, instead of directly storing an instance pointer, accept a
      * nullary callable returning a pointer/reference to the desired class
@@ -233,6 +353,8 @@ public:
      * boost::lambda::var(instance) or boost::lambda::constant(instance_ptr)
      * produce suitable callables.
      *
+     * TODO: variant accepting a method of the containing class, no getter.
+     *
      * Pass an LLSD::Array of parameter names, and optionally another
      * LLSD::Array of default parameter values, a la LLSDArgsMapper.
      *
@@ -240,42 +362,96 @@ public:
      * an LLSD::Array using LLSDArgsMapper and then convert each entry in turn
      * to the corresponding parameter type using LLSDParam.
      */
-    template<typename Method, typename InstanceGetter>
-    typename boost::enable_if< boost::function_types::is_member_function_pointer<Method>
-                               >::type add(const std::string& name,
-                                           const std::string& desc,
-                                           Method f,
-                                           const InstanceGetter& getter,
-                                           const LLSD& params,
-                                           const LLSD& defaults=LLSD());
+    template<typename Method, typename InstanceGetter,
+             typename = typename std::enable_if<
+                 boost::function_types::is_member_function_pointer<Method>::value &&
+                 ! std::is_convertible<InstanceGetter, LLSD>::value
+             >::type>
+    void add(const std::string& name, const std::string& desc, Method f,
+             const InstanceGetter& getter, const LLSD& params,
+             const LLSD& defaults=LLSD());
 
     //@}    
 
     /// Unregister a callable
     bool remove(const std::string& name);
 
-    /// Call a registered callable with an explicitly-specified name. If no
-    /// such callable exists, die with LL_ERRS. If the @a event fails to match
-    /// the @a required prototype specified at add() time, die with LL_ERRS.
-    void operator()(const std::string& name, const LLSD& event) const;
+    /// Exception if an attempted call fails for any reason
+    struct DispatchError: public LLException
+    {
+        DispatchError(const std::string& what): LLException(what) {}
+    };
+
+    /// Specific exception for an attempt to call a nonexistent name
+    struct DispatchMissing: public DispatchError
+    {
+        DispatchMissing(const std::string& what): DispatchError(what) {}
+    };
+
+    /**
+     * Call a registered callable with an explicitly-specified name,
+     * converting its return value to LLSD (undefined for a void callable).
+     * It is an error if no such callable exists. It is an error if the @a
+     * event fails to match the @a required prototype specified at add()
+     * time.
+     *
+     * @a event must be an LLSD array for a callable registered to accept its
+     * arguments from such an array. It must be an LLSD map for a callable
+     * registered to accept its arguments from such a map.
+     */
+    LLSD operator()(const std::string& name, const LLSD& event) const;
 
-    /// Call a registered callable with an explicitly-specified name and
-    /// return <tt>true</tt>. If no such callable exists, return
-    /// <tt>false</tt>. If the @a event fails to match the @a required
-    /// prototype specified at add() time, die with LL_ERRS.
+    /**
+     * Call a registered callable with an explicitly-specified name and
+     * return <tt>true</tt>. If no such callable exists, return
+     * <tt>false</tt>. It is an error if the @a event fails to match the @a
+     * required prototype specified at add() time.
+     *
+     * @a event must be an LLSD array for a callable registered to accept its
+     * arguments from such an array. It must be an LLSD map for a callable
+     * registered to accept its arguments from such a map.
+     */
     bool try_call(const std::string& name, const LLSD& event) const;
 
-    /// Extract the @a key value from the incoming @a event, and call the
-    /// callable whose name is specified by that map @a key. If no such
-    /// callable exists, die with LL_ERRS. If the @a event fails to match the
-    /// @a required prototype specified at add() time, die with LL_ERRS.
-    void operator()(const LLSD& event) const;
-
-    /// Extract the @a key value from the incoming @a event, call the callable
-    /// whose name is specified by that map @a key and return <tt>true</tt>.
-    /// If no such callable exists, return <tt>false</tt>. If the @a event
-    /// fails to match the @a required prototype specified at add() time, die
-    /// with LL_ERRS.
+    /**
+     * Extract the @a key specified to our constructor from the incoming LLSD
+     * map @a event, and call the callable whose name is specified by that @a
+     * key's value, converting its return value to LLSD (undefined for a void
+     * callable). It is an error if no such callable exists. It is an error if
+     * the @a event fails to match the @a required prototype specified at
+     * add() time.
+     *
+     * For a (non-nullary) callable registered to accept its arguments from an
+     * LLSD array, the @a event map must contain the key @a argskey specified to
+     * our constructor. The value of the @a argskey key must be an LLSD array
+     * containing the arguments to pass to the callable named by @a key.
+     *
+     * For a callable registered to accept its arguments from an LLSD map, if
+     * the @a event map contains the key @a argskey specified our constructor,
+     * extract the value of the @a argskey key and use it as the arguments map.
+     * If @a event contains no @a argskey key, use the whole @a event as the
+     * arguments map.
+     */
+    LLSD operator()(const LLSD& event) const;
+
+    /**
+     * Extract the @a key specified to our constructor from the incoming LLSD
+     * map @a event, call the callable whose name is specified by that @a
+     * key's value and return <tt>true</tt>. If no such callable exists,
+     * return <tt>false</tt>. It is an error if the @a event fails to match
+     * the @a required prototype specified at add() time.
+     *
+     * For a (non-nullary) callable registered to accept its arguments from an
+     * LLSD array, the @a event map must contain the key @a argskey specified to
+     * our constructor. The value of the @a argskey key must be an LLSD array
+     * containing the arguments to pass to the callable named by @a key.
+     *
+     * For a callable registered to accept its arguments from an LLSD map, if
+     * the @a event map contains the key @a argskey specified our constructor,
+     * extract the value of the @a argskey key and use it as the arguments map.
+     * If @a event contains no @a argskey key, use the whole @a event as the
+     * arguments map.
+     */
     bool try_call(const LLSD& event) const;
 
     /// @name Iterate over defined names
@@ -285,22 +461,26 @@ public:
 private:
     struct DispatchEntry
     {
-        DispatchEntry(const std::string& desc);
+        DispatchEntry(LLEventDispatcher* parent, const std::string& desc);
         virtual ~DispatchEntry() {} // suppress MSVC warning, sigh
 
+        // store a plain dumb back-pointer because the parent
+        // LLEventDispatcher manages the lifespan of each DispatchEntry
+        // subclass instance -- not the other way around
+        LLEventDispatcher* mParent;
         std::string mDesc;
 
-        virtual void call(const std::string& desc, const LLSD& event) const = 0;
-        virtual LLSD addMetadata(LLSD) const = 0;
+        virtual LLSD call(const std::string& desc, const LLSD& event,
+                          bool fromMap, const std::string& argskey) const = 0;
+        virtual LLSD getMetadata() const = 0;
+
+        template <typename... ARGS>
+        [[noreturn]] void callFail(ARGS&&... args) const
+        {
+            mParent->callFail<LLEventDispatcher::DispatchError>(std::forward<ARGS>(args)...);
+        }
     };
-    // Tried using boost::ptr_map<std::string, DispatchEntry>, but ptr_map<>
-    // wants its value type to be "clonable," even just to dereference an
-    // iterator. I don't want to clone entries -- if I have to copy an entry
-    // around, I want it to continue pointing to the same DispatchEntry
-    // subclass object. However, I definitely want DispatchMap to destroy
-    // DispatchEntry if no references are outstanding at the time an entry is
-    // removed. This looks like a job for boost::shared_ptr.
-    typedef std::map<std::string, boost::shared_ptr<DispatchEntry> > DispatchMap;
+    typedef std::map<std::string, std::unique_ptr<DispatchEntry> > DispatchMap;
 
 public:
     /// We want the flexibility to redefine what data we store per name,
@@ -323,12 +503,58 @@ public:
 
     /// Retrieve the LLSD key we use for one-arg <tt>operator()</tt> method
     std::string getDispatchKey() const { return mKey; }
+    /// Retrieve the LLSD key we use for non-map arguments
+    std::string getArgsKey() const { return mArgskey; }
+
+    /// description of this instance's leaf class and description
+    friend std::ostream& operator<<(std::ostream&, const LLEventDispatcher&);
 
 private:
-    template <class CLASS, typename METHOD>
+    void addLLSD(const std::string& name,
+                 const std::string& desc,
+                 const Callable& callable,
+                 const LLSD& required);
+
+    template <class CLASS, typename METHOD,
+              typename std::enable_if<
+                  std::is_base_of<LLEventDispatcher, CLASS>::value,
+                  bool
+              >::type=true>
     void addMethod(const std::string& name, const std::string& desc,
                    const METHOD& method, const LLSD& required)
     {
+        // Why two overloaded addMethod() methods, discriminated with
+        // std::is_base_of? It might seem simpler to use dynamic_cast and test
+        // for nullptr. The trouble is that it doesn't work for LazyEventAPI
+        // deferred registration: we get nullptr even for a method of an
+        // LLEventAPI subclass.
+        CLASS* downcast = static_cast<CLASS*>(this);
+        add(name,
+            desc,
+            Callable(LL::make_always_return<LLSD>(
+                         [downcast, method]
+                         (const LLSD& args)
+                         {
+                             return (downcast->*method)(args);
+                         })),
+            required);
+    }
+
+    template <class CLASS, typename METHOD,
+              typename std::enable_if<
+                  ! std::is_base_of<LLEventDispatcher, CLASS>::value,
+                  bool
+              >::type=true>
+    void addMethod(const std::string& name, const std::string& desc,
+                   const METHOD&, const LLSD&)
+    {
+        addFail(name, typeid(CLASS).name());
+    }
+
+    template <class CLASS, typename METHOD>
+    void addVMethod(const std::string& name, const std::string& desc,
+                    const METHOD& method)
+    {
         CLASS* downcast = dynamic_cast<CLASS*>(this);
         if (! downcast)
         {
@@ -336,38 +562,85 @@ private:
         }
         else
         {
-            add(name, desc, boost::bind(method, downcast, _1), required);
+            // add() arbitrary method plus InstanceGetter, where the
+            // InstanceGetter in this case returns 'this'. We don't need to
+            // worry about binding 'this' because, once this LLEventDispatcher
+            // is destroyed, the DispatchEntry goes away too.
+            add(name, desc, method, [downcast](){ return downcast; });
         }
     }
-    void addFail(const std::string& name, const std::string& classname) const;
 
-    std::string mDesc, mKey;
+    template <typename Function>
+    void addV(const std::string& name, const std::string& desc, Function f);
+
+    void addFail(const std::string& name, const char* classname) const;
+    LLSD try_call(const std::string& key, const std::string& name,
+                  const LLSD& event) const;
+
+protected:
+    // raise specified EXCEPTION with specified stringize(ARGS)
+    template <typename EXCEPTION, typename... ARGS>
+    [[noreturn]] void callFail(ARGS&&... args) const;
+    template <typename EXCEPTION, typename... ARGS>
+    [[noreturn]] static
+    void sCallFail(ARGS&&... args);
+
+    // Manage transient state, e.g. which registered callable we're attempting
+    // to call, for error reporting
+    class SetState
+    {
+    public:
+        template <typename... ARGS>
+        SetState(const LLEventDispatcher* self, ARGS&&... args):
+            mSelf(self)
+        {
+            mSet = mSelf->setState(*this, stringize(std::forward<ARGS>(args)...));
+        }
+        // RAII class: forbid both copy and move
+        SetState(const SetState&) = delete;
+        SetState(SetState&&) = delete;
+        SetState& operator=(const SetState&) = delete;
+        SetState& operator=(SetState&&) = delete;
+        virtual ~SetState()
+        {
+            // if we're the ones who succeeded in setting state, clear it
+            if (mSet)
+            {
+                mSelf->setState(*this, {});
+            }
+        }
+
+    private:
+        const LLEventDispatcher* mSelf;
+        bool mSet;
+    };
+
+private:
+    std::string mDesc, mKey, mArgskey;
     DispatchMap mDispatch;
+    // transient state: must be fiber_specific since multiple threads and/or
+    // multiple fibers may be calling concurrently. Make it mutable so we can
+    // use SetState even within const methods.
+    mutable boost::fibers::fiber_specific_ptr<std::string> mState;
+
+    std::string getState() const;
+    // setState() requires SetState& because only the SetState class should
+    // call it. Make it const so we can use SetState even within const methods.
+    bool setState(SetState&, const std::string& state) const;
 
     static NameDesc makeNameDesc(const DispatchMap::value_type& item)
     {
         return NameDesc(item.first, item.second->mDesc);
     }
 
+    class LLSDArgsMapper;
     struct LLSDDispatchEntry;
     struct ParamsDispatchEntry;
     struct ArrayParamsDispatchEntry;
     struct MapParamsDispatchEntry;
 
-    // Step 2 of parameter analysis. Instantiating invoker<some_function_type>
-    // implicitly sets its From and To parameters to the (compile time) begin
-    // and end iterators over that function's parameter types.
-    template< typename Function
-              , class From = typename boost::mpl::begin< boost::function_types::parameter_types<Function> >::type
-              , class To   = typename boost::mpl::end< boost::function_types::parameter_types<Function> >::type
-              >
-    struct invoker;
-
-    // deliver LLSD arguments one at a time
-    typedef boost::function<LLSD()> args_source;
-    // obtain args from an args_source to build param list and call target
-    // function
-    typedef boost::function<void(const args_source&)> invoker_function;
+    // call target function with args from LLSD array
+    typedef std::function<LLSD(const LLSD&)> invoker_function;
 
     template <typename Function>
     invoker_function make_invoker(Function f);
@@ -387,101 +660,38 @@ private:
 /*****************************************************************************
 *   LLEventDispatcher template implementation details
 *****************************************************************************/
-// Step 3 of parameter analysis, the recursive case.
-template<typename Function, class From, class To>
-struct LLEventDispatcher::invoker
-{
-    template<typename T>
-    struct remove_cv_ref
-        : boost::remove_cv< typename boost::remove_reference<T>::type >
-    { };
-
-    // apply() accepts an arbitrary boost::fusion sequence as args. It
-    // examines the next parameter type in the parameter-types sequence
-    // bounded by From and To, obtains the next LLSD object from the passed
-    // args_source and constructs an LLSDParam of appropriate type to try
-    // to convert the value. It then recurs with the next parameter-types
-    // iterator, passing the args sequence thus far.
-    template<typename Args>
-    static inline
-    void apply(Function func, const args_source& argsrc, Args const & args)
-    {
-        typedef typename boost::mpl::deref<From>::type arg_type;
-        typedef typename boost::mpl::next<From>::type next_iter_type;
-        typedef typename remove_cv_ref<arg_type>::type plain_arg_type;
-
-        invoker<Function, next_iter_type, To>::apply
-        ( func, argsrc, boost::fusion::push_back(args, LLSDParam<plain_arg_type>(argsrc())));
-    }
-
-    // Special treatment for instance (first) parameter of a non-static member
-    // function. Accept the instance-getter callable, calling that to produce
-    // the first args value. Since we know we're at the top of the recursion
-    // chain, we need not also require a partial args sequence from our caller.
-    template <typename InstanceGetter>
-    static inline
-    void method_apply(Function func, const args_source& argsrc, const InstanceGetter& getter)
-    {
-        typedef typename boost::mpl::next<From>::type next_iter_type;
-
-        // Instead of grabbing the first item from argsrc and making an
-        // LLSDParam of it, call getter() and pass that as the instance param.
-        invoker<Function, next_iter_type, To>::apply
-        ( func, argsrc, boost::fusion::push_back(boost::fusion::nil(), boost::ref(getter())));
-    }
-};
-
-// Step 4 of parameter analysis, the leaf case. When the general
-// invoker<Function, From, To> logic has advanced From until it matches To,
-// the compiler will pick this template specialization.
-template<typename Function, class To>
-struct LLEventDispatcher::invoker<Function,To,To>
-{
-    // the argument list is complete, now call the function
-    template<typename Args>
-    static inline
-    void apply(Function func, const args_source&, Args const & args)
-    {
-        boost::fusion::invoke(func, args);
-    }
-};
-
-template<typename Function>
-typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function> >::type
-LLEventDispatcher::add(const std::string& name, const std::string& desc, Function f)
+template <typename Function>
+void LLEventDispatcher::addV(const std::string& name, const std::string& desc, Function f)
 {
-    // Construct an invoker_function, a callable accepting const args_source&.
+    // Construct an invoker_function, a callable accepting const LLSD&.
     // Add to DispatchMap an ArrayParamsDispatchEntry that will handle the
     // caller's LLSD::Array.
     addArrayParamsDispatchEntry(name, desc, make_invoker(f),
-                                boost::function_types::function_arity<Function>::value);
+                                LL::function_arity<Function>::value);
 }
 
-template<typename Method, typename InstanceGetter>
-typename boost::enable_if< boost::function_types::is_member_function_pointer<Method> >::type
-LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
-                       const InstanceGetter& getter)
+template<typename Method, typename InstanceGetter, typename>
+void LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
+                            const InstanceGetter& getter)
 {
     // Subtract 1 from the compile-time arity because the getter takes care of
     // the first parameter. We only need (arity - 1) additional arguments.
     addArrayParamsDispatchEntry(name, desc, make_invoker(f, getter),
-                                boost::function_types::function_arity<Method>::value - 1);
+                                LL::function_arity<Method>::value - 1);
 }
 
-template<typename Function>
-typename boost::enable_if< boost::function_types::is_nonmember_callable_builtin<Function> >::type
-LLEventDispatcher::add(const std::string& name, const std::string& desc, Function f,
-                       const LLSD& params, const LLSD& defaults)
+template<typename Function, typename>
+void LLEventDispatcher::add(const std::string& name, const std::string& desc, Function f,
+                            const LLSD& params, const LLSD& defaults)
 {
     // See comments for previous is_nonmember_callable_builtin add().
     addMapParamsDispatchEntry(name, desc, make_invoker(f), params, defaults);
 }
 
-template<typename Method, typename InstanceGetter>
-typename boost::enable_if< boost::function_types::is_member_function_pointer<Method> >::type
-LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
-                       const InstanceGetter& getter,
-                       const LLSD& params, const LLSD& defaults)
+template<typename Method, typename InstanceGetter, typename>
+void LLEventDispatcher::add(const std::string& name, const std::string& desc, Method f,
+                            const InstanceGetter& getter,
+                            const LLSD& params, const LLSD& defaults)
 {
     addMapParamsDispatchEntry(name, desc, make_invoker(f, getter), params, defaults);
 }
@@ -490,29 +700,45 @@ template <typename Function>
 LLEventDispatcher::invoker_function
 LLEventDispatcher::make_invoker(Function f)
 {
-    // Step 1 of parameter analysis, the top of the recursion. Passing a
-    // suitable f (see add()'s enable_if condition) to this method causes it
-    // to infer the function type; specifying that function type to invoker<>
-    // causes it to fill in the begin/end MPL iterators over the function's
-    // list of parameter types.
-    // While normally invoker::apply() could infer its template type from the
-    // boost::fusion::nil parameter value, here we must be explicit since
-    // we're boost::bind()ing it rather than calling it directly.
-    return boost::bind(&invoker<Function>::template apply<boost::fusion::nil>,
-                       f,
-                       _1,
-                       boost::fusion::nil());
+    // Return an invoker_function that accepts (const LLSD& args).
+    return [f](const LLSD& args)
+    {
+        // When called, call always_return<LLSD>, directing it to call
+        // f(expanded args). always_return<LLSD> guarantees we'll get an LLSD
+        // value back, even if it's undefined because 'f' doesn't return a
+        // type convertible to LLSD.
+        return LL::always_return<LLSD>(
+            [f, args]
+            ()
+            {
+                return LL::apply(f, args);
+            });
+    };
 }
 
 template <typename Method, typename InstanceGetter>
 LLEventDispatcher::invoker_function
 LLEventDispatcher::make_invoker(Method f, const InstanceGetter& getter)
 {
-    // Use invoker::method_apply() to treat the instance (first) arg specially.
-    return boost::bind(&invoker<Method>::template method_apply<InstanceGetter>,
-                       f,
-                       _1,
-                       getter);
+    return [f, getter](const LLSD& args)
+    {
+        // always_return<LLSD>() immediately calls the lambda we pass, and
+        // returns LLSD whether our passed lambda returns void or non-void.
+        return LL::always_return<LLSD>(
+            [f, getter, args]
+            ()
+            {
+                // function_arity<member function> includes its implicit 'this' pointer
+                constexpr auto arity = LL::function_arity<
+                    typename std::remove_reference<Method>::type>::value - 1;
+
+                // Use bind_front() to bind the method to (a pointer to) the object
+                // returned by getter(). It's okay to capture and bind a pointer
+                // because this bind_front() object will last only as long as this
+                // lambda call.
+                return LL::apply_n<arity>(LL::bind_front(f, LL::get_ptr(getter())), args);
+            });
+    };
 }
 
 /*****************************************************************************
@@ -521,21 +747,138 @@ LLEventDispatcher::make_invoker(Method f, const InstanceGetter& getter)
 /**
  * Bundle an LLEventPump and a listener with an LLEventDispatcher. A class
  * that contains (or derives from) LLDispatchListener need only specify the
- * LLEventPump name and dispatch key, and add() its methods. Incoming events
- * will automatically be dispatched.
+ * LLEventPump name and dispatch key, and add() its methods. Each incoming
+ * event ("request") will automatically be dispatched.
+ *
+ * If the request contains a "reply" key specifying the LLSD::String name of
+ * an LLEventPump to which to respond, LLDispatchListener will attempt to send
+ * a response to that LLEventPump.
+ *
+ * If some error occurs (e.g. nonexistent callable name, wrong params) and
+ * "reply" is present, LLDispatchListener will send a response map to the
+ * specified LLEventPump containing an "error" key whose value is the relevant
+ * error message. If "reply" is not present, the DispatchError exception will
+ * propagate. Since LLDispatchListener bundles an LLEventStream, which
+ * attempts the call immediately on receiving the post() call, there's a
+ * reasonable chance that the exception will highlight the post() call that
+ * triggered the error.
+ *
+ * If LLDispatchListener successfully calls the target callable, but no
+ * "reply" key is present, any value returned by that callable is discarded.
+ * If a "reply" key is present, but the target callable is void -- or it
+ * returns LLSD::isUndefined() -- no response is sent. If a void callable
+ * wants to send a response, it must do so explicitly.
+ *
+ * If the target callable returns a type convertible to LLSD (and, if it
+ * directly returns LLSD, the return value isDefined()), and if a "reply" key
+ * is present in the request, LLDispatchListener will post the returned value
+ * to the "reply" LLEventPump. If the returned value is an LLSD map, it will
+ * merge the echoed "reqid" key into the map and send that. Otherwise, it will
+ * send an LLSD map containing "reqid" and a "data" key whose value is the
+ * value returned by the target callable.
+ *
+ * (It is inadvisable for a target callable to return an LLSD map containing
+ * keys "data", "reqid" or "error", as that will confuse the invoker.)
+ *
+ * Normally the request will specify the value of the dispatch key as an
+ * LLSD::String naming the target callable. Alternatively, several such calls
+ * may be "batched" as described below.
+ *
+ * If the value of the dispatch key is itself an LLSD map (a "request map"),
+ * each map key must name a target callable, and the value of that key must
+ * contain the parameters to pass to that callable. If a "reply" key is
+ * present in the request, the response map will contain a key for each of the
+ * keys in the request map. The value of every such key is the value returned
+ * by the target callable.
+ *
+ * (Avoid naming any target callable in the LLDispatchListener "data", "reqid"
+ * or "error" to avoid confusion.)
+ *
+ * Since LLDispatchListener calls the target callables specified by a request
+ * map in arbitrary order, this form assumes that the batched operations are
+ * independent of each other. LLDispatchListener will attempt every call, even
+ * if some attempts produce errors. If any keys in the request map produce
+ * errors, LLDispatchListener builds a composite error message string
+ * collecting the relevant messages. The corresponding keys will be missing
+ * from the response map. As in the single-callable case, absent a "reply" key
+ * in the request, this error message will be thrown as a DispatchError. With
+ * a "reply" key, it will be returned as the value of the "error" key. This
+ * form can indicate partial success: some request keys might have
+ * return-value keys in the response, others might have message text in the
+ * "error" key.
+ *
+ * If a specific call sequence is required, the value of the dispatch key may
+ * instead be an LLSD array (a "request array"). Each entry in the request
+ * array ("request entry") names a target callable, to be called in
+ * array-index sequence. Arguments for that callable may be specified in
+ * either of two ways.
+ *
+ * The request entry may itself be a two-element array, whose [0] is an
+ * LLSD::String naming the target callable and whose [1] contains the
+ * arguments to pass to that callable.
+ *
+ * Alternatively, the request entry may be an LLSD::String naming the target
+ * callable, in which case the request must contain an arguments key (optional
+ * third constructor argument) whose value is an array matching the request
+ * array. The arguments for the request entry's target callable are found at
+ * the same index in the arguments key array.
+ *
+ * If a "reply" key is present in the request, the response map will contain a
+ * "data" key whose value is an array. Each entry in that response array will
+ * contain the result from the corresponding request entry.
+ *
+ * This form assumes that any of the batched operations might depend on the
+ * success of a previous operation in the same batch. The @emph first error
+ * encountered will terminate the sequence. The error message might either be
+ * thrown as DispatchError or, given a "reply" key, returned as the "error"
+ * key in the response map. This form can indicate partial success: the first
+ * few request entries might have return-value entries in the "data" response
+ * array, along with an "error" key whose value is the error message that
+ * stopped the sequence.
  */
-class LL_COMMON_API LLDispatchListener: public LLEventDispatcher
+// Instead of containing an LLEventStream, LLDispatchListener derives from it.
+// This allows an LLEventPumps::PumpFactory to return a pointer to an
+// LLDispatchListener (subclass) instance, and still have ~LLEventPumps()
+// properly clean it up.
+class LL_COMMON_API LLDispatchListener:
+    public LLEventDispatcher,
+    public LLEventStream
 {
 public:
-    LLDispatchListener(const std::string& pumpname, const std::string& key);
-
-    std::string getPumpName() const { return mPump.getName(); }
+    /// LLEventPump name, dispatch key [, arguments key (see LLEventDispatcher)]
+    template <typename... ARGS>
+    LLDispatchListener(const std::string& pumpname, const std::string& key,
+                       ARGS&&... args);
+    virtual ~LLDispatchListener() {}
 
 private:
-    bool process(const LLSD& event);
+    bool process(const LLSD& event) const;
+    void call_one(const LLSD& name, const LLSD& event) const;
+    void call_map(const LLSD& reqmap, const LLSD& event) const;
+    void call_array(const LLSD& reqarray, const LLSD& event) const;
+    void reply(const LLSD& reply, const LLSD& request) const;
 
-    LLEventStream mPump;
     LLTempBoundListener mBoundListener;
+    static std::string mReplyKey;
 };
 
+template <typename... ARGS>
+LLDispatchListener::LLDispatchListener(const std::string& pumpname, const std::string& key,
+                                       ARGS&&... args):
+    // pass through any additional arguments to LLEventDispatcher ctor
+    LLEventDispatcher(pumpname, key, std::forward<ARGS>(args)...),
+    // Do NOT tweak the passed pumpname. In practice, when someone
+    // instantiates a subclass of our LLEventAPI subclass, they intend to
+    // claim that LLEventPump name in the global LLEventPumps namespace. It
+    // would be mysterious and distressing if we allowed name tweaking, and
+    // someone else claimed pumpname first for a completely unrelated
+    // LLEventPump. Posted events would never reach our subclass listener
+    // because we would have silently changed its name; meanwhile listeners
+    // (if any) on that other LLEventPump would be confused by the events
+    // intended for our subclass.
+    LLEventStream(pumpname, false),
+    mBoundListener(listen("self", [this](const LLSD& event){ return process(event); }))
+{
+}
+
 #endif /* ! defined(LL_LLEVENTDISPATCHER_H) */
diff --git a/indra/llcommon/lleventfilter.h b/indra/llcommon/lleventfilter.h
index 7613850fb2..1fb41e0297 100644
--- a/indra/llcommon/lleventfilter.h
+++ b/indra/llcommon/lleventfilter.h
@@ -435,16 +435,61 @@ public:
         // generic type-appropriate store through mTarget, construct an
         // LLSDParam<T> and store that, thus engaging LLSDParam's custom
         // conversions.
-        mTarget = LLSDParam<T>(llsd::drill(event, mPath));
+        storeTarget(LLSDParam<T>(llsd::drill(event, mPath)));
         return mConsume;
     }
 
 private:
+    // This method disambiguates LLStoreListener<LLSD>. Directly assigning
+    // some_LLSD_var = LLSDParam<LLSD>(some_LLSD_value);
+    // is problematic because the compiler has too many choices: LLSD has
+    // multiple assignment operator overloads, and LLSDParam<LLSD> has a
+    // templated conversion operator. But LLSDParam<LLSD> can convert to a
+    // (const LLSD&) parameter, and LLSD::operator=(const LLSD&) works.
+    void storeTarget(const T& value)
+    {
+        mTarget = value;
+    }
+
     T& mTarget;
     const LLSD mPath;
     const bool mConsume;
 };
 
+/**
+ * LLVarHolder bundles a target variable of the specified type. We use it as a
+ * base class so the target variable will be fully constructed by the time a
+ * subclass constructor tries to pass a reference to some other base class.
+ */
+template <typename T>
+struct LLVarHolder
+{
+    T mVar;
+};
+
+/**
+ * LLCaptureListener isa LLStoreListener that bundles the target variable of
+ * interest.
+ */
+template <typename T>
+class LLCaptureListener: public LLVarHolder<T>,
+                         public LLStoreListener<T>
+{
+private:
+    using holder = LLVarHolder<T>;
+    using super = LLStoreListener<T>;
+
+public:
+    LLCaptureListener(const LLSD& path=LLSD(), bool consume=false):
+        super(*this, holder::mVar, path, consume)
+    {}
+
+    void set(T&& newval=T()) { holder::mVar = std::forward<T>(newval); }
+
+    const T& get() const { return holder::mVar; }
+    operator const T&() { return holder::mVar; }
+};
+
 /*****************************************************************************
 *   LLEventLogProxy
 *****************************************************************************/
diff --git a/indra/llcommon/llevents.cpp b/indra/llcommon/llevents.cpp
index 0a213bddef..1a305ec3dc 100644
--- a/indra/llcommon/llevents.cpp
+++ b/indra/llcommon/llevents.cpp
@@ -68,19 +68,78 @@
 LLEventPumps::LLEventPumps():
     mFactories
     {
-        { "LLEventStream",   [](const std::string& name, bool tweak)
+        { "LLEventStream",   [](const std::string& name, bool tweak, const std::string& /*type*/)
                              { return new LLEventStream(name, tweak); } },
-        { "LLEventMailDrop", [](const std::string& name, bool tweak)
+        { "LLEventMailDrop", [](const std::string& name, bool tweak, const std::string& /*type*/)
                              { return new LLEventMailDrop(name, tweak); } }
     },
     mTypes
     {
-        // LLEventStream is the default for obtain(), so even if somebody DOES
-        // call obtain("placeholder"), this sample entry won't break anything.
-        { "placeholder", "LLEventStream" }
+//      { "placeholder", "LLEventStream" }
     }
 {}
 
+bool LLEventPumps::registerTypeFactory(const std::string& type, const TypeFactory& factory)
+{
+    auto found = mFactories.find(type);
+    // can't re-register a TypeFactory for a type name that's already registered
+    if (found != mFactories.end())
+        return false;
+    // doesn't already exist, go ahead and register
+    mFactories[type] = factory;
+    return true;
+}
+
+void LLEventPumps::unregisterTypeFactory(const std::string& type)
+{
+    auto found = mFactories.find(type);
+    if (found != mFactories.end())
+        mFactories.erase(found);
+}
+
+bool LLEventPumps::registerPumpFactory(const std::string& name, const PumpFactory& factory)
+{
+    // Do we already have a pump by this name?
+    if (mPumpMap.find(name) != mPumpMap.end())
+        return false;
+    // Do we already have an override for this pump name?
+    if (mTypes.find(name) != mTypes.end())
+        return false;
+    // Leverage the two-level lookup implemented by mTypes (pump name -> type
+    // name) and mFactories (type name -> factory). We could instead create a
+    // whole separate (pump name -> factory) map, and look in both; or we
+    // could change mTypes to (pump name -> factory) and, for typical type-
+    // based lookups, use a "factory" that looks up the real factory in
+    // mFactories. But this works, and we don't expect many calls to make() -
+    // either explicit or implicit via obtain().
+    // Create a bogus type name extremely unlikely to collide with an actual type.
+    static std::string nul(1, '\0');
+    std::string type_name{ nul + name };
+    mTypes[name] = type_name;
+    // TypeFactory is called with (name, tweak, type), whereas PumpFactory
+    // accepts only name. We could adapt with std::bind(), but this lambda
+    // does the trick.
+    mFactories[type_name] =
+        [factory]
+        (const std::string& name, bool /*tweak*/, const std::string& /*type*/)
+        { return factory(name); };
+    return true;
+}
+
+void LLEventPumps::unregisterPumpFactory(const std::string& name)
+{
+    auto tfound = mTypes.find(name);
+    if (tfound != mTypes.end())
+    {
+        auto ffound = mFactories.find(tfound->second);
+        if (ffound != mFactories.end())
+        {
+            mFactories.erase(ffound);
+        }
+        mTypes.erase(tfound);
+    }
+}
+
 LLEventPump& LLEventPumps::obtain(const std::string& name)
 {
     PumpMap::iterator found = mPumpMap.find(name);
@@ -114,7 +173,7 @@ LLEventPump& LLEventPumps::make(const std::string& name, bool tweak,
         // Passing an unrecognized type name is a no-no
         LLTHROW(BadType(type));
     }
-    auto newInstance = (found->second)(name, tweak);
+    auto newInstance = (found->second)(name, tweak, type);
     // LLEventPump's constructor implicitly registers each new instance in
     // mPumpMap. But remember that we instantiated it (in mOurPumps) so we'll
     // delete it later.
diff --git a/indra/llcommon/llevents.h b/indra/llcommon/llevents.h
index ae6e5aabc9..c1dbf4392f 100644
--- a/indra/llcommon/llevents.h
+++ b/indra/llcommon/llevents.h
@@ -268,6 +268,45 @@ public:
     LLEventPump& make(const std::string& name, bool tweak=false,
                       const std::string& type=std::string());
 
+    /// function passed to registerTypeFactory()
+    typedef std::function<LLEventPump*(const std::string& name, bool tweak, const std::string& type)> TypeFactory;
+
+    /**
+     * Register a TypeFactory for use with make(). When make() is called with
+     * the specified @a type string, call @a factory(name, tweak, type) to
+     * instantiate it.
+     *
+     * Returns true if successfully registered, false if there already exists
+     * a TypeFactory for the specified @a type name.
+     */
+    bool registerTypeFactory(const std::string& type, const TypeFactory& factory);
+    void unregisterTypeFactory(const std::string& type);
+
+    /// function passed to registerPumpFactory()
+    typedef std::function<LLEventPump*(const std::string&)> PumpFactory;
+
+    /**
+     * Register a PumpFactory for use with obtain(). When obtain() is called
+     * with the specified @a name string, if an LLEventPump with the specified
+     * @a name doesn't already exist, call @a factory(name) to instantiate it.
+     *
+     * Returns true if successfully registered, false if there already exists
+     * a factory override for the specified @a name.
+     *
+     * PumpFactory does not support @a tweak because it's only called when
+     * <i>that particular</i> @a name is passed to obtain(). Bear in mind that
+     * <tt>obtain(name)</tt> might still bypass the caller's PumpFactory for a
+     * couple different reasons:
+     *
+     * * registerPumpFactory() returns false because there's already a factory
+     *   override for the specified @name
+     * * between a successful <tt>registerPumpFactory(name)</tt> call (returns
+     *   true) and a call to <tt>obtain(name)</tt>, someone explicitly
+     *   instantiated an LLEventPump(name), so obtain(name) returned that.
+     */
+    bool registerPumpFactory(const std::string& name, const PumpFactory& factory);
+    void unregisterPumpFactory(const std::string& name);
+
     /**
      * Find the named LLEventPump instance. If it exists post the message to it.
      * If the pump does not exist, do nothing.
@@ -325,13 +364,13 @@ testable:
     typedef std::set<LLEventPump*> PumpSet;
     PumpSet mOurPumps;
     // for make(), map string type name to LLEventPump subclass factory function
-    typedef std::map<std::string, std::function<LLEventPump*(const std::string&, bool)>> PumpFactories;
+    typedef std::map<std::string, TypeFactory> TypeFactories;
     // Data used by make().
     // One might think mFactories and mTypes could reasonably be static. So
     // they could -- if not for the fact that make() or obtain() might be
     // called before this module's static variables have been initialized.
     // This is why we use singletons in the first place.
-    PumpFactories mFactories;
+    TypeFactories mFactories;
 
     // for obtain(), map desired string instance name to string type when
     // obtain() must create the instance
diff --git a/indra/llcommon/llframetimer.cpp b/indra/llcommon/llframetimer.cpp
index c54029e8b4..1e9920746b 100644
--- a/indra/llcommon/llframetimer.cpp
+++ b/indra/llcommon/llframetimer.cpp
@@ -29,11 +29,6 @@
 
 #include "llframetimer.h"
 
-// We don't bother building a stand alone lib; we just need to include the one source file for Tracy support
-#if LL_PROFILER_CONFIGURATION == LL_PROFILER_CONFIG_TRACY || LL_PROFILER_CONFIGURATION == LL_PROFILER_CONFIG_TRACY_FAST_TIMER
-	#include "TracyClient.cpp"
-#endif // LL_PROFILER_CONFIGURATION
-
 // Static members
 //LLTimer	LLFrameTimer::sInternalTimer;
 U64 LLFrameTimer::sStartTotalTime = totalTime();
diff --git a/indra/llcommon/llinstancetracker.h b/indra/llcommon/llinstancetracker.h
index 34f2a5985a..27422e1266 100644
--- a/indra/llcommon/llinstancetracker.h
+++ b/indra/llcommon/llinstancetracker.h
@@ -104,22 +104,26 @@ public:
         return LockStatic()->mMap.size(); 
     }
     
-    // snapshot of std::pair<const KEY, std::shared_ptr<T>> pairs
-    class snapshot
+    // snapshot of std::pair<const KEY, std::shared_ptr<SUBCLASS>> pairs, for
+    // some SUBCLASS derived from T
+    template <typename SUBCLASS>
+    class snapshot_of
     {
         // It's very important that what we store in this snapshot are
         // weak_ptrs, NOT shared_ptrs. That's how we discover whether any
         // instance has been deleted during the lifespan of a snapshot.
         typedef std::vector<std::pair<const KEY, weak_t>> VectorType;
-        // Dereferencing our iterator produces a std::shared_ptr for each
-        // instance that still exists. Since we store weak_ptrs, that involves
-        // two chained transformations:
+        // Dereferencing the iterator we publish produces a
+        // std::shared_ptr<SUBCLASS> for each instance that still exists.
+        // Since we store weak_ptr<T>, that involves two chained
+        // transformations:
         // - a transform_iterator to lock the weak_ptr and return a shared_ptr
-        // - a filter_iterator to skip any shared_ptr that has become invalid.
+        // - a filter_iterator to skip any shared_ptr<T> that has become
+        //   invalid or references any T instance that isn't SUBCLASS.
         // It is very important that we filter lazily, that is, during
         // traversal. Any one of our stored weak_ptrs might expire during
         // traversal.
-        typedef std::pair<const KEY, ptr_t> strong_pair;
+        typedef std::pair<const KEY, std::shared_ptr<SUBCLASS>> strong_pair;
         // Note for future reference: nat has not yet had any luck (up to
         // Boost 1.67) trying to use boost::transform_iterator with a hand-
         // coded functor, only with actual functions. In my experience, an
@@ -127,7 +131,7 @@ public:
         // result_type typedef. But this works.
         static strong_pair strengthen(typename VectorType::value_type& pair)
         {
-            return { pair.first, pair.second.lock() };
+            return { pair.first, std::dynamic_pointer_cast<SUBCLASS>(pair.second.lock()) };
         }
         static bool dead_skipper(const strong_pair& pair)
         {
@@ -135,7 +139,7 @@ public:
         }
 
     public:
-        snapshot():
+        snapshot_of():
             // populate our vector with a snapshot of (locked!) InstanceMap
             // note, this assigns pair<KEY, shared_ptr> to pair<KEY, weak_ptr>
             mData(mLock->mMap.begin(), mLock->mMap.end())
@@ -184,44 +188,51 @@ public:
 #endif // LL_WINDOWS
         VectorType mData;
     };
+    using snapshot = snapshot_of<T>;
 
-    // iterate over this for references to each instance
-    class instance_snapshot: public snapshot
+    // iterate over this for references to each SUBCLASS instance
+    template <typename SUBCLASS>
+    class instance_snapshot_of: public snapshot_of<SUBCLASS>
     {
     private:
-        static T& instance_getter(typename snapshot::iterator::reference pair)
+        using super = snapshot_of<SUBCLASS>;
+        static T& instance_getter(typename super::iterator::reference pair)
         {
             return *pair.second;
         }
     public:
         typedef boost::transform_iterator<decltype(instance_getter)*,
-                                          typename snapshot::iterator> iterator;
-        iterator begin() { return iterator(snapshot::begin(), instance_getter); }
-        iterator end()   { return iterator(snapshot::end(),   instance_getter); }
+                                          typename super::iterator> iterator;
+        iterator begin() { return iterator(super::begin(), instance_getter); }
+        iterator end()   { return iterator(super::end(),   instance_getter); }
 
         void deleteAll()
         {
-            for (auto it(snapshot::begin()), end(snapshot::end()); it != end; ++it)
+            for (auto it(super::begin()), end(super::end()); it != end; ++it)
             {
                 delete it->second.get();
             }
         }
-    };                   
+    };
+    using instance_snapshot = instance_snapshot_of<T>;
 
     // iterate over this for each key
-    class key_snapshot: public snapshot
+    template <typename SUBCLASS>
+    class key_snapshot_of: public snapshot_of<SUBCLASS>
     {
     private:
-        static KEY key_getter(typename snapshot::iterator::reference pair)
+        using super = snapshot_of<SUBCLASS>;
+        static KEY key_getter(typename super::iterator::reference pair)
         {
             return pair.first;
         }
     public:
         typedef boost::transform_iterator<decltype(key_getter)*,
-                                          typename snapshot::iterator> iterator;
-        iterator begin() { return iterator(snapshot::begin(), key_getter); }
-        iterator end()   { return iterator(snapshot::end(),   key_getter); }
+                                          typename super::iterator> iterator;
+        iterator begin() { return iterator(super::begin(), key_getter); }
+        iterator end()   { return iterator(super::end(),   key_getter); }
     };
+    using key_snapshot = key_snapshot_of<T>;
 
     static ptr_t getInstance(const KEY& k)
     {
@@ -368,22 +379,25 @@ public:
         return LockStatic()->mSet.size();
     }
 
-    // snapshot of std::shared_ptr<T> pointers
-    class snapshot
+    // snapshot of std::shared_ptr<SUBCLASS> pointers
+    template <typename SUBCLASS>
+    class snapshot_of
     {
         // It's very important that what we store in this snapshot are
         // weak_ptrs, NOT shared_ptrs. That's how we discover whether any
         // instance has been deleted during the lifespan of a snapshot.
         typedef std::vector<weak_t> VectorType;
-        // Dereferencing our iterator produces a std::shared_ptr for each
-        // instance that still exists. Since we store weak_ptrs, that involves
-        // two chained transformations:
+        // Dereferencing the iterator we publish produces a
+        // std::shared_ptr<SUBCLASS> for each instance that still exists.
+        // Since we store weak_ptrs, that involves two chained
+        // transformations:
         // - a transform_iterator to lock the weak_ptr and return a shared_ptr
-        // - a filter_iterator to skip any shared_ptr that has become invalid.
-        typedef std::shared_ptr<T> strong_ptr;
+        // - a filter_iterator to skip any shared_ptr that has become invalid
+        //   or references any T instance that isn't SUBCLASS.
+        typedef std::shared_ptr<SUBCLASS> strong_ptr;
         static strong_ptr strengthen(typename VectorType::value_type& ptr)
         {
-            return ptr.lock();
+            return std::dynamic_pointer_cast<SUBCLASS>(ptr.lock());
         }
         static bool dead_skipper(const strong_ptr& ptr)
         {
@@ -391,7 +405,7 @@ public:
         }
 
     public:
-        snapshot():
+        snapshot_of():
             // populate our vector with a snapshot of (locked!) InstanceSet
             // note, this assigns stored shared_ptrs to weak_ptrs for snapshot
             mData(mLock->mSet.begin(), mLock->mSet.end())
@@ -437,22 +451,33 @@ public:
 #endif // LL_WINDOWS
         VectorType mData;
     };
+    using snapshot = snapshot_of<T>;
 
     // iterate over this for references to each instance
-    struct instance_snapshot: public snapshot
+    template <typename SUBCLASS>
+    class instance_snapshot_of: public snapshot_of<SUBCLASS>
     {
-        typedef boost::indirect_iterator<typename snapshot::iterator> iterator;
-        iterator begin() { return iterator(snapshot::begin()); }
-        iterator end()   { return iterator(snapshot::end()); }
+    private:
+        using super = snapshot_of<SUBCLASS>;
+
+    public:
+        typedef boost::indirect_iterator<typename super::iterator> iterator;
+        iterator begin() { return iterator(super::begin()); }
+        iterator end()   { return iterator(super::end()); }
 
         void deleteAll()
         {
-            for (auto it(snapshot::begin()), end(snapshot::end()); it != end; ++it)
+            for (auto it(super::begin()), end(super::end()); it != end; ++it)
             {
                 delete it->get();
             }
         }
     };
+    using instance_snapshot = instance_snapshot_of<T>;
+    // key_snapshot_of isn't really meaningful, but define it anyway to avoid
+    // requiring two different LLInstanceTrackerSubclass implementations.
+    template <typename SUBCLASS>
+    using key_snapshot_of = instance_snapshot_of<SUBCLASS>;
 
 protected:
     LLInstanceTracker()
diff --git a/indra/llcommon/llinstancetrackersubclass.h b/indra/llcommon/llinstancetrackersubclass.h
new file mode 100644
index 0000000000..ea9a38200f
--- /dev/null
+++ b/indra/llcommon/llinstancetrackersubclass.h
@@ -0,0 +1,98 @@
+/**
+ * @file   llinstancetrackersubclass.h
+ * @author Nat Goodspeed
+ * @date   2022-12-09
+ * @brief  Intermediate class to get subclass-specific types from
+ *         LLInstanceTracker instance-retrieval methods.
+ *
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_LLINSTANCETRACKERSUBCLASS_H)
+#define LL_LLINSTANCETRACKERSUBCLASS_H
+
+#include <memory>                   // std::shared_ptr, std::weak_ptr
+
+/**
+ * Derive your subclass S of a subclass T of LLInstanceTracker<T> from
+ * LLInstanceTrackerSubclass<S, T> to perform appropriate downcasting and
+ * filtering for LLInstanceTracker access methods.
+ *
+ * LLInstanceTracker<T> uses CRTP, so that getWeak(), getInstance(), snapshot
+ * and instance_snapshot return pointers and references to T. The trouble is
+ * that subclasses T0 and T1 derived from T also get pointers and references
+ * to their base class T, requiring explicit downcasting. Moreover,
+ * T0::getInstance() shouldn't find an instance of any T subclass other than
+ * T0. Nor should T0::snapshot.
+ *
+ * @code
+ * class Tracked: public LLInstanceTracker<Tracked, std::string>
+ * {
+ * private:
+ *     using super = LLInstanceTracker<Tracked, std::string>;
+ * public:
+ *     Tracked(const std::string& name): super(name) {}
+ *     // All references to Tracked::ptr_t, Tracked::getInstance() etc.
+ *     // appropriately use Tracked.
+ *     // ...
+ * };
+ *
+ * // But now we derive SubTracked from Tracked. We need SubTracked::ptr_t,
+ * // SubTracked::getInstance() etc. to use SubTracked, not Tracked.
+ * // This LLInstanceTrackerSubclass specialization is itself derived from
+ * // Tracked.
+ * class SubTracked: public LLInstanceTrackerSubclass<SubTracked, Tracked>
+ * {
+ * private:
+ *     using super = LLInstanceTrackerSubclass<SubTracked, Tracked>;
+ * public:
+ *     // LLInstanceTrackerSubclass's constructor forwards to Tracked's.
+ *     SubTracked(const std::string& name): super(name) {}
+ *     // SubTracked::getInstance() returns std::shared_ptr<SubTracked>, etc.
+ *     // ...
+ * @endcode
+ */
+template <typename SUBCLASS, typename T>
+class LLInstanceTrackerSubclass: public T
+{
+public:
+    using ptr_t  = std::shared_ptr<SUBCLASS>;
+    using weak_t = std::weak_ptr<SUBCLASS>;
+
+    // forward any constructor call to the corresponding T ctor
+    template <typename... ARGS>
+    LLInstanceTrackerSubclass(ARGS&&... args):
+        T(std::forward<ARGS>(args)...)
+    {}
+
+    weak_t getWeak()
+    {
+        // call base-class getWeak(), try to lock, downcast to SUBCLASS
+        return std::dynamic_pointer_cast<SUBCLASS>(T::getWeak().lock());
+    }
+
+    template <typename KEY>
+    static ptr_t getInstance(const KEY& k)
+    {
+        return std::dynamic_pointer_cast<SUBCLASS>(T::getInstance(k));
+    }
+
+    using snapshot          = typename T::template snapshot_of<SUBCLASS>;
+    using instance_snapshot = typename T::template instance_snapshot_of<SUBCLASS>;
+    using key_snapshot      = typename T::template key_snapshot_of<SUBCLASS>;
+
+    static size_t instanceCount()
+    {
+        // T::instanceCount() lies because our snapshot, et al., won't
+        // necessarily return all the T instances -- only those that are also
+        // SUBCLASS instances. Count those.
+        size_t count = 0;
+        for (const auto& pair : snapshot())
+            ++count;
+        return count;
+    }
+};
+
+#endif /* ! defined(LL_LLINSTANCETRACKERSUBCLASS_H) */
diff --git a/indra/llcommon/llleap.cpp b/indra/llcommon/llleap.cpp
index 5b5bf97cef..8f88e728ce 100644
--- a/indra/llcommon/llleap.cpp
+++ b/indra/llcommon/llleap.cpp
@@ -340,11 +340,28 @@ public:
             }
             else
             {
-                // The LLSD object we got from our stream contains the keys we
-                // need.
-                LLEventPumps::instance().obtain(data["pump"]).post(data["data"]);
-                // Block calls to this method; resetting mBlocker unblocks calls
-                // to the other method.
+                try
+                {
+                    // The LLSD object we got from our stream contains the
+                    // keys we need.
+                    LLEventPumps::instance().obtain(data["pump"]).post(data["data"]);
+                }
+                catch (const std::exception& err)
+                {
+                    // No plugin should be allowed to crash the viewer by
+                    // driving an exception -- intentionally or not.
+                    LOG_UNHANDLED_EXCEPTION(stringize("handling request ", data));
+                    // Whether or not the plugin added a "reply" key to the
+                    // request, send a reply. We happen to know who originated
+                    // this request, and the reply LLEventPump of interest.
+                    // Not our problem if the plugin ignores the reply event.
+                    data["reply"] = mReplyPump.getName();
+                    sendReply(llsd::map("error",
+                                        stringize(LLError::Log::classname(err), ": ", err.what())),
+                              data);
+                }
+                // Block calls to this method; resetting mBlocker unblocks
+                // calls to the other method.
                 mBlocker.reset(new LLEventPump::Blocker(mStdoutDataConnection));
                 // Go check for any more pending events in the buffer.
                 if (childout.size())
diff --git a/indra/llcommon/llleaplistener.cpp b/indra/llcommon/llleaplistener.cpp
index 11bfec1b31..471f52e91c 100644
--- a/indra/llcommon/llleaplistener.cpp
+++ b/indra/llcommon/llleaplistener.cpp
@@ -14,14 +14,16 @@
 // associated header
 #include "llleaplistener.h"
 // STL headers
-#include <map>
+#include <algorithm>                // std::find_if
 #include <functional>
+#include <map>
+#include <set>
 // std headers
 // external library headers
-#include <boost/foreach.hpp>
 // other Linden headers
-#include "lluuid.h"
+#include "lazyeventapi.h"
 #include "llsdutil.h"
+#include "lluuid.h"
 #include "stringize.h"
 
 /*****************************************************************************
@@ -110,7 +112,7 @@ LLLeapListener::~LLLeapListener()
     // value_type, and Bad Things would happen if you copied an
     // LLTempBoundListener. (Destruction of the original would disconnect the
     // listener, invalidating every stored connection.)
-    BOOST_FOREACH(ListenersMap::value_type& pair, mListeners)
+    for (ListenersMap::value_type& pair : mListeners)
     {
         pair.second.disconnect();
     }
@@ -208,31 +210,65 @@ void LLLeapListener::getAPIs(const LLSD& request) const
 {
     Response reply(LLSD(), request);
 
+    // first, traverse existing LLEventAPI instances
+    std::set<std::string> instances;
     for (auto& ea : LLEventAPI::instance_snapshot())
     {
-        LLSD info;
-        info["desc"] = ea.getDesc();
-        reply[ea.getName()] = info;
+        // remember which APIs are actually instantiated
+        instances.insert(ea.getName());
+        reply[ea.getName()] = llsd::map("desc", ea.getDesc());
+    }
+    // supplement that with *potential* instances: that is, instances of
+    // LazyEventAPI that can each instantiate an LLEventAPI on demand
+    for (const auto& lea : LL::LazyEventAPIBase::instance_snapshot())
+    {
+        // skip any LazyEventAPI that's already instantiated its LLEventAPI
+        if (instances.find(lea.getName()) == instances.end())
+        {
+            reply[lea.getName()] = llsd::map("desc", lea.getDesc());
+        }
     }
 }
 
+// Because LazyEventAPI deliberately mimics LLEventAPI's query API, this
+// function can be passed either -- even though they're unrelated types.
+template <typename API>
+void reportAPI(LLEventAPI::Response& reply, const API& api)
+{
+    reply["name"] = api.getName();
+    reply["desc"] = api.getDesc();
+    reply["key"]  = api.getDispatchKey();
+    LLSD ops;
+    for (const auto& namedesc : api)
+    {
+        ops.append(api.getMetadata(namedesc.first));
+    }
+    reply["ops"] = ops;
+}
+
 void LLLeapListener::getAPI(const LLSD& request) const
 {
     Response reply(LLSD(), request);
 
-    auto found = LLEventAPI::getInstance(request["api"]);
-    if (found)
+    // check first among existing LLEventAPI instances
+    auto foundea = LLEventAPI::getInstance(request["api"]);
+    if (foundea)
+    {
+        reportAPI(reply, *foundea);
+    }
+    else
     {
-        reply["name"] = found->getName();
-        reply["desc"] = found->getDesc();
-        reply["key"] = found->getDispatchKey();
-        LLSD ops;
-        for (LLEventAPI::const_iterator oi(found->begin()), oend(found->end());
-             oi != oend; ++oi)
+        // Here the requested LLEventAPI doesn't yet exist, but do we have a
+        // registered LazyEventAPI for it?
+        LL::LazyEventAPIBase::instance_snapshot snap;
+        auto foundlea = std::find_if(snap.begin(), snap.end(),
+                                     [api = request["api"].asString()]
+                                     (const auto& lea)
+                                     { return (lea.getName() == api); });
+        if (foundlea != snap.end())
         {
-            ops.append(found->getMetadata(oi->first));
+            reportAPI(reply, *foundlea);
         }
-        reply["ops"] = ops;
     }
 }
 
diff --git a/indra/llcommon/llmemory.cpp b/indra/llcommon/llmemory.cpp
index d6ae1284d3..7cdf7254ff 100644
--- a/indra/llcommon/llmemory.cpp
+++ b/indra/llcommon/llmemory.cpp
@@ -35,6 +35,7 @@
 # include <sys/types.h>
 # include <mach/task.h>
 # include <mach/mach_init.h>
+#include <mach/mach_host.h>
 #elif LL_LINUX
 # include <unistd.h>
 #endif
@@ -109,6 +110,50 @@ void LLMemory::updateMemoryInfo()
 	{
 		sAvailPhysicalMemInKB = U32Kilobytes(0);
 	}
+
+#elif defined(LL_DARWIN)
+    task_vm_info info;
+    mach_msg_type_number_t  infoCount = TASK_VM_INFO_COUNT;
+    // MACH_TASK_BASIC_INFO reports the same resident_size, but does not tell us the reusable bytes or phys_footprint.
+    if (task_info(mach_task_self(), TASK_VM_INFO, reinterpret_cast<task_info_t>(&info), &infoCount) == KERN_SUCCESS)
+    {
+        // Our Windows definition of PagefileUsage is documented by Microsoft as "the total amount of
+        // memory that the memory manager has committed for a running process", which is rss.
+        sAllocatedPageSizeInKB = U32Bytes(info.resident_size);
+
+        // Activity Monitor => Inspect Process => Real Memory Size appears to report resident_size
+        // Activity monitor => main window memory column appears to report phys_footprint, which spot checks as at least 30% less.
+        //        I think that is because of compression, which isn't going to give us a consistent measurement. We want uncompressed totals.
+        //
+        // In between is resident_size - reusable. This is what Chrome source code uses, with source comments saying it is 'the "Real Memory" value
+        // reported for the app by the Memory Monitor in Instruments.' It is still about 8% bigger than phys_footprint.
+        //
+        // (On Windows, we use WorkingSetSize.)
+        sAllocatedMemInKB = U32Bytes(info.resident_size - info.reusable);
+     }
+    else
+    {
+        LL_WARNS() << "task_info failed" << LL_ENDL;
+    }
+
+    // Total installed and available physical memory are properties of the host, not just our process.
+    vm_statistics64_data_t vmstat;
+    mach_msg_type_number_t count = HOST_VM_INFO64_COUNT;
+    mach_port_t host = mach_host_self();
+    vm_size_t page_size;
+    host_page_size(host, &page_size);
+    kern_return_t result = host_statistics64(host, HOST_VM_INFO64, reinterpret_cast<host_info_t>(&vmstat), &count);
+    if (result == KERN_SUCCESS) {
+        // This is what Chrome reports as 'the "Physical Memory Free" value reported by the Memory Monitor in Instruments.'
+        // Note though that inactive pages are not included here and not yet free, but could become so under memory pressure.
+        sAvailPhysicalMemInKB = U32Bytes(vmstat.free_count * page_size);
+        sMaxPhysicalMemInKB = LLMemoryInfo::getHardwareMemSize();
+      }
+    else
+    {
+        LL_WARNS() << "task_info failed" << LL_ENDL;
+    }
+
 #else
 	//not valid for other systems for now.
 	sAllocatedMemInKB = U64Bytes(LLMemory::getCurrentRSS());
diff --git a/indra/llcommon/llmutex.h b/indra/llcommon/llmutex.h
index 838d7d34c0..0d70da6178 100644
--- a/indra/llcommon/llmutex.h
+++ b/indra/llcommon/llmutex.h
@@ -36,7 +36,8 @@
 
 //============================================================================
 
-#define MUTEX_DEBUG (LL_DEBUG || LL_RELEASE_WITH_DEBUG_INFO)
+//#define MUTEX_DEBUG (LL_DEBUG || LL_RELEASE_WITH_DEBUG_INFO)
+#define MUTEX_DEBUG 0 //disable mutex debugging as it's interfering with profiles
 
 #if MUTEX_DEBUG
 #include <map>
@@ -61,7 +62,7 @@ protected:
 	mutable LLThread::id_t	mLockingThread;
 	
 #if MUTEX_DEBUG
-	std::map<LLThread::id_t, BOOL> mIsLocked;
+	std::unordered_map<LLThread::id_t, BOOL> mIsLocked;
 #endif
 };
 
diff --git a/indra/llcommon/llpointer.h b/indra/llcommon/llpointer.h
index 96ccfb481e..64aceddf32 100644
--- a/indra/llcommon/llpointer.h
+++ b/indra/llcommon/llpointer.h
@@ -341,4 +341,28 @@ private:
 	bool mStayUnique;
 };
 
+
+// boost hash adapter
+template <class Type>
+struct boost::hash<LLPointer<Type>>
+{
+    typedef LLPointer<Type> argument_type;
+    typedef std::size_t result_type;
+    result_type operator()(argument_type const& s) const
+    {
+        return (std::size_t) s.get();
+    }
+};
+
+// Adapt boost hash to std hash
+namespace std
+{
+    template<class Type> struct hash<LLPointer<Type>>
+    {
+        std::size_t operator()(LLPointer<Type> const& s) const noexcept
+        {
+            return boost::hash<LLPointer<Type>>()(s);
+        }
+    };
+}
 #endif
diff --git a/indra/llcommon/llprofiler.h b/indra/llcommon/llprofiler.h
index f9d7ae7ce4..af5e5777bf 100644
--- a/indra/llcommon/llprofiler.h
+++ b/indra/llcommon/llprofiler.h
@@ -86,8 +86,12 @@ extern thread_local bool gProfilerEnabled;
         #define TRACY_ONLY_IPV4      1
         #include "Tracy.hpp"
 
-        // Mutually exclusive with detailed memory tracing
+        // Enable OpenGL profiling
         #define LL_PROFILER_ENABLE_TRACY_OPENGL 0
+
+        // Enable RenderDoc labeling
+        #define LL_PROFILER_ENABLE_RENDER_DOC 0
+
     #endif
 
     #if LL_PROFILER_CONFIGURATION == LL_PROFILER_CONFIG_TRACY
@@ -104,14 +108,13 @@ extern thread_local bool gProfilerEnabled;
         #define LL_PROFILE_ZONE_ERR(name)               LL_PROFILE_ZONE_NAMED_COLOR( name, 0XFF0000  )  // RGB yellow
         #define LL_PROFILE_ZONE_INFO(name)              LL_PROFILE_ZONE_NAMED_COLOR( name, 0X00FFFF  )  // RGB cyan
         #define LL_PROFILE_ZONE_WARN(name)              LL_PROFILE_ZONE_NAMED_COLOR( name, 0x0FFFF00 )  // RGB red
-        #define LL_PROFILE_ALLOC(ptr, size)             TracyAlloc(ptr, size)
-        #define LL_PROFILE_FREE(ptr)                    TracyFree(ptr)
     #endif
     #if LL_PROFILER_CONFIGURATION == LL_PROFILER_CONFIG_FAST_TIMER
         #define LL_PROFILER_FRAME_END
         #define LL_PROFILER_SET_THREAD_NAME( name )      (void)(name)
         #define LL_RECORD_BLOCK_TIME(name)                                                                  const LLTrace::BlockTimer& LL_GLUE_TOKENS(block_time_recorder, __LINE__)(LLTrace::timeThisBlock(name)); (void)LL_GLUE_TOKENS(block_time_recorder, __LINE__);
         #define LL_PROFILE_ZONE_NAMED(name)             // LL_PROFILE_ZONE_NAMED is a no-op when Tracy is disabled
+        #define LL_PROFILE_ZONE_NAMED_COLOR(name,color) // LL_PROFILE_ZONE_NAMED_COLOR is a no-op when Tracy is disabled
         #define LL_PROFILE_ZONE_SCOPED                  // LL_PROFILE_ZONE_SCOPED is a no-op when Tracy is disabled
         #define LL_PROFILE_ZONE_COLOR(name,color)       // LL_RECORD_BLOCK_TIME(name)
 
@@ -121,8 +124,6 @@ extern thread_local bool gProfilerEnabled;
         #define LL_PROFILE_ZONE_ERR(name)               (void)(name); // Not supported
         #define LL_PROFILE_ZONE_INFO(name)              (void)(name); // Not supported
         #define LL_PROFILE_ZONE_WARN(name)              (void)(name); // Not supported
-        #define LL_PROFILE_ALLOC(ptr, size)             (void)(ptr); (void)(size);
-        #define LL_PROFILE_FREE(ptr)                    (void)(ptr);
     #endif
     #if LL_PROFILER_CONFIGURATION == LL_PROFILER_CONFIG_TRACY_FAST_TIMER
         #define LL_PROFILER_FRAME_END                   FrameMark
@@ -138,14 +139,45 @@ extern thread_local bool gProfilerEnabled;
         #define LL_PROFILE_ZONE_ERR(name)               LL_PROFILE_ZONE_NAMED_COLOR( name, 0XFF0000  )  // RGB yellow
         #define LL_PROFILE_ZONE_INFO(name)              LL_PROFILE_ZONE_NAMED_COLOR( name, 0X00FFFF  )  // RGB cyan
         #define LL_PROFILE_ZONE_WARN(name)              LL_PROFILE_ZONE_NAMED_COLOR( name, 0x0FFFF00 )  // RGB red
-        #define LL_PROFILE_ALLOC(ptr, size)             TracyAlloc(ptr, size)
-        #define LL_PROFILE_FREE(ptr)                    TracyFree(ptr)
     #endif
 #else
     #define LL_PROFILER_FRAME_END
     #define LL_PROFILER_SET_THREAD_NAME( name ) (void)(name)
 #endif // LL_PROFILER
 
+#if LL_PROFILER_ENABLE_TRACY_OPENGL
+#define LL_PROFILE_GPU_ZONE(name)        TracyGpuZone(name)
+#define LL_PROFILE_GPU_ZONEC(name,color) TracyGpuZoneC(name,color)
+#define LL_PROFILER_GPU_COLLECT           TracyGpuCollect
+#define LL_PROFILER_GPU_CONTEXT           TracyGpuContext
+
+// disable memory tracking (incompatible with GPU tracing
+#define LL_PROFILE_ALLOC(ptr, size)             (void)(ptr); (void)(size);
+#define LL_PROFILE_FREE(ptr)                    (void)(ptr);
+#else
+#define LL_PROFILE_GPU_ZONE(name)        (void)name;
+#define LL_PROFILE_GPU_ZONEC(name,color) (void)name;(void)color;
+#define LL_PROFILER_GPU_COLLECT
+#define LL_PROFILER_GPU_CONTEXT
+
+#define LL_LABEL_OBJECT_GL(type, name, length, label)
+
+#if LL_PROFILER_CONFIGURATION > 1
+#define LL_PROFILE_ALLOC(ptr, size)             TracyAlloc(ptr, size)
+#define LL_PROFILE_FREE(ptr)                    TracyFree(ptr)
+#else
+#define LL_PROFILE_ALLOC(ptr, size)             (void)(ptr); (void)(size);
+#define LL_PROFILE_FREE(ptr)                    (void)(ptr);
+#endif
+
+#endif
+
+#if LL_PROFILER_ENABLE_RENDER_DOC
+#define LL_LABEL_OBJECT_GL(type, name, length, label) glObjectLabel(type, name, length, label)
+#else
+#define LL_LABEL_OBJECT_GL(type, name, length, label)
+#endif
+
 #include "llprofilercategories.h"
 
 #endif // LL_PROFILER_H
diff --git a/indra/llcommon/llprofilercategories.h b/indra/llcommon/llprofilercategories.h
index 8db29468cc..617431f629 100644
--- a/indra/llcommon/llprofilercategories.h
+++ b/indra/llcommon/llprofilercategories.h
@@ -52,7 +52,7 @@
 #define LL_PROFILER_CATEGORY_ENABLE_LOGGING     1
 #define LL_PROFILER_CATEGORY_ENABLE_MATERIAL    1
 #define LL_PROFILER_CATEGORY_ENABLE_MEDIA       1
-#define LL_PROFILER_CATEGORY_ENABLE_MEMORY      1
+#define LL_PROFILER_CATEGORY_ENABLE_MEMORY      0
 #define LL_PROFILER_CATEGORY_ENABLE_NETWORK     1
 #define LL_PROFILER_CATEGORY_ENABLE_OCTREE      1
 #define LL_PROFILER_CATEGORY_ENABLE_PIPELINE    1
diff --git a/indra/llcommon/llptrto.h b/indra/llcommon/llptrto.h
index 4082e30de6..9ef279fdbf 100644
--- a/indra/llcommon/llptrto.h
+++ b/indra/llcommon/llptrto.h
@@ -33,9 +33,12 @@
 
 #include "llpointer.h"
 #include "llrefcount.h"             // LLRefCount
+#include <boost/intrusive_ptr.hpp>
+#include <boost/shared_ptr.hpp>
 #include <boost/type_traits/is_base_of.hpp>
 #include <boost/type_traits/remove_pointer.hpp>
-#include <boost/utility/enable_if.hpp>
+#include <memory>                   // std::shared_ptr, std::unique_ptr
+#include <type_traits>
 
 /**
  * LLPtrTo<TARGET>::type is either of two things:
@@ -55,14 +58,14 @@ struct LLPtrTo
 
 /// specialize for subclasses of LLRefCount
 template <class T>
-struct LLPtrTo<T, typename boost::enable_if< boost::is_base_of<LLRefCount, T> >::type>
+struct LLPtrTo<T, typename std::enable_if< boost::is_base_of<LLRefCount, T>::value >::type>
 {
     typedef LLPointer<T> type;
 };
 
 /// specialize for subclasses of LLThreadSafeRefCount
 template <class T>
-struct LLPtrTo<T, typename boost::enable_if< boost::is_base_of<LLThreadSafeRefCount, T> >::type>
+struct LLPtrTo<T, typename std::enable_if< boost::is_base_of<LLThreadSafeRefCount, T>::value >::type>
 {
     typedef LLPointer<T> type;
 };
@@ -83,4 +86,83 @@ struct LLRemovePointer< LLPointer<SOMECLASS> >
     typedef SOMECLASS type;
 };
 
+namespace LL
+{
+
+/*****************************************************************************
+*   get_ref()
+*****************************************************************************/
+    template <typename T>
+    struct GetRef
+    {
+        // return const ref or non-const ref, depending on whether we can bind
+        // a non-const lvalue ref to the argument
+        const auto& operator()(const T& obj) const { return obj; }
+        auto& operator()(T& obj) const { return obj; }
+    };
+
+    template <typename T>
+    struct GetRef<const T*>
+    {
+        const auto& operator()(const T* ptr) const { return *ptr; }
+    };
+
+    template <typename T>
+    struct GetRef<T*>
+    {
+        auto& operator()(T* ptr) const { return *ptr; }
+    };
+
+    template <typename T>
+    struct GetRef< LLPointer<T> >
+    {
+        auto& operator()(LLPointer<T> ptr) const { return *ptr; }
+    };
+
+    /// whether we're passed a pointer or a reference, return a reference
+    template <typename T>
+    auto& get_ref(T& ptr_or_ref)
+    {
+        return GetRef<typename std::decay<T>::type>()(ptr_or_ref);
+    }
+
+    template <typename T>
+    const auto& get_ref(const T& ptr_or_ref)
+    {
+        return GetRef<typename std::decay<T>::type>()(ptr_or_ref);
+    }
+
+/*****************************************************************************
+*   get_ptr()
+*****************************************************************************/
+    // if T is any pointer type we recognize, return it unchanged
+    template <typename T>
+    const T* get_ptr(const T* ptr) { return ptr; }
+
+    template <typename T>
+    T* get_ptr(T* ptr) { return ptr; }
+
+    template <typename T>
+    const std::shared_ptr<T>& get_ptr(const std::shared_ptr<T>& ptr) { return ptr; }
+
+    template <typename T>
+    const std::unique_ptr<T>& get_ptr(const std::unique_ptr<T>& ptr) { return ptr; }
+
+    template <typename T>
+    const boost::shared_ptr<T>& get_ptr(const boost::shared_ptr<T>& ptr) { return ptr; }
+
+    template <typename T>
+    const boost::intrusive_ptr<T>& get_ptr(const boost::intrusive_ptr<T>& ptr) { return ptr; }
+
+    template <typename T>
+    const LLPointer<T>& get_ptr(const LLPointer<T>& ptr) { return ptr; }
+
+    // T is not any pointer type we recognize, take a pointer to the parameter
+    template <typename T>
+    const T* get_ptr(const T& obj) { return &obj; }
+
+    template <typename T>
+    T* get_ptr(T& obj) { return &obj; }
+} // namespace LL
+
 #endif /* ! defined(LL_LLPTRTO_H) */
diff --git a/indra/llcommon/llqueuedthread.cpp b/indra/llcommon/llqueuedthread.cpp
index b06fee0ec2..394212ee0d 100644
--- a/indra/llcommon/llqueuedthread.cpp
+++ b/indra/llcommon/llqueuedthread.cpp
@@ -26,20 +26,26 @@
 #include "linden_common.h"
 #include "llqueuedthread.h"
 
+#include <chrono>
+
 #include "llstl.h"
 #include "lltimer.h"	// ms_sleep()
-#include "lltracethreadrecorder.h"
+#include "llmutex.h"
 
 //============================================================================
 
 // MAIN THREAD
 LLQueuedThread::LLQueuedThread(const std::string& name, bool threaded, bool should_pause) :
-	LLThread(name),
-	mThreaded(threaded),
-	mIdleThread(TRUE),
-	mNextHandle(0),
-	mStarted(FALSE)
+    LLThread(name),
+    mIdleThread(TRUE),
+    mNextHandle(0),
+    mStarted(FALSE),
+    mThreaded(threaded),
+    mRequestQueue(name, 1024 * 1024)
 {
+    llassert(threaded); // not threaded implementation is deprecated
+    mMainQueue = LL::WorkQueue::getInstance("mainloop");
+
 	if (mThreaded)
 	{
 		if(should_pause)
@@ -69,6 +75,11 @@ void LLQueuedThread::shutdown()
 	unpause(); // MAIN THREAD
 	if (mThreaded)
 	{
+        if (mRequestQueue.size() == 0)
+        {
+            mRequestQueue.close();
+        }
+
 		S32 timeout = 100;
 		for ( ; timeout>0; timeout--)
 		{
@@ -104,6 +115,8 @@ void LLQueuedThread::shutdown()
 	{
 		LL_WARNS() << "~LLQueuedThread() called with active requests: " << active_count << LL_ENDL;
 	}
+
+    mRequestQueue.close();
 }
 
 //----------------------------------------------------------------------------
@@ -112,6 +125,7 @@ void LLQueuedThread::shutdown()
 // virtual
 size_t LLQueuedThread::update(F32 max_time_ms)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	if (!mStarted)
 	{
 		if (!mThreaded)
@@ -125,29 +139,34 @@ size_t LLQueuedThread::update(F32 max_time_ms)
 
 size_t LLQueuedThread::updateQueue(F32 max_time_ms)
 {
-	F64 max_time = (F64)max_time_ms * .001;
-	LLTimer timer;
-	size_t pending = 1;
-
+    LL_PROFILE_ZONE_SCOPED;
 	// Frame Update
 	if (mThreaded)
 	{
-		pending = getPending();
-		if(pending > 0)
+        // schedule a call to threadedUpdate for every call to updateQueue
+        if (!isQuitting())
+        {
+            mRequestQueue.post([=]()
+                {
+                    LL_PROFILE_ZONE_NAMED_CATEGORY_THREAD("qt - update");
+                    mIdleThread = FALSE;
+                    threadedUpdate();
+                    mIdleThread = TRUE;
+                }
+            );
+        }
+
+		if(getPending() > 0)
 		{
-		unpause();
-	}
+		    unpause();
+	    }
 	}
 	else
 	{
-		while (pending > 0)
-		{
-			pending = processNextRequest();
-			if (max_time && timer.getElapsedTimeF64() > max_time)
-				break;
-		}
+        mRequestQueue.runFor(std::chrono::microseconds((int) (max_time_ms*1000.f)));
+        threadedUpdate();
 	}
-	return pending;
+	return getPending();
 }
 
 void LLQueuedThread::incQueue()
@@ -166,11 +185,7 @@ void LLQueuedThread::incQueue()
 // May be called from any thread
 size_t LLQueuedThread::getPending()
 {
-	size_t res;
-	lockData();
-	res = mRequestQueue.size();
-	unlockData();
-	return res;
+    return mRequestQueue.size();
 }
 
 // MAIN thread
@@ -195,35 +210,28 @@ void LLQueuedThread::waitOnPending()
 // MAIN thread
 void LLQueuedThread::printQueueStats()
 {
-	lockData();
-	if (!mRequestQueue.empty())
+    U32 size = mRequestQueue.size();
+	if (size > 0)
 	{
-		QueuedRequest *req = *mRequestQueue.begin();
-		LL_INFOS() << llformat("Pending Requests:%d Current status:%d", mRequestQueue.size(), req->getStatus()) << LL_ENDL;
+		LL_INFOS() << llformat("Pending Requests:%d ", mRequestQueue.size()) << LL_ENDL;
 	}
 	else
 	{
 		LL_INFOS() << "Queued Thread Idle" << LL_ENDL;
 	}
-	unlockData();
 }
 
 // MAIN thread
 LLQueuedThread::handle_t LLQueuedThread::generateHandle()
 {
-	lockData();
-	while ((mNextHandle == nullHandle()) || (mRequestHash.find(mNextHandle)))
-	{
-		mNextHandle++;
-	}
-	const LLQueuedThread::handle_t res = mNextHandle++;
-	unlockData();
+    U32 res = ++mNextHandle;
 	return res;
 }
 
 // MAIN thread
 bool LLQueuedThread::addRequest(QueuedRequest* req)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	if (mStatus == QUITTING)
 	{
 		return false;
@@ -231,14 +239,14 @@ bool LLQueuedThread::addRequest(QueuedRequest* req)
 	
 	lockData();
 	req->setStatus(STATUS_QUEUED);
-	mRequestQueue.insert(req);
-	mRequestHash.insert(req);
+    mRequestHash.insert(req);
 #if _DEBUG
 // 	LL_INFOS() << llformat("LLQueuedThread::Added req [%08d]",handle) << LL_ENDL;
 #endif
 	unlockData();
 
-	incQueue();
+    llassert(!mDataLock->isSelfLocked());
+    mRequestQueue.post([this, req]() { processRequest(req); });
 
 	return true;
 }
@@ -246,6 +254,7 @@ bool LLQueuedThread::addRequest(QueuedRequest* req)
 // MAIN thread
 bool LLQueuedThread::waitForResult(LLQueuedThread::handle_t handle, bool auto_complete)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	llassert (handle != nullHandle());
 	bool res = false;
 	bool waspaused = isPaused();
@@ -312,6 +321,7 @@ LLQueuedThread::status_t LLQueuedThread::getRequestStatus(handle_t handle)
 
 void LLQueuedThread::abortRequest(handle_t handle, bool autocomplete)
 {
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
 	lockData();
 	QueuedRequest* req = (QueuedRequest*)mRequestHash.find(handle);
 	if (req)
@@ -333,30 +343,9 @@ void LLQueuedThread::setFlags(handle_t handle, U32 flags)
 	unlockData();
 }
 
-void LLQueuedThread::setPriority(handle_t handle, U32 priority)
-{
-	lockData();
-	QueuedRequest* req = (QueuedRequest*)mRequestHash.find(handle);
-	if (req)
-	{
-		if(req->getStatus() == STATUS_INPROGRESS)
-		{
-			// not in list
-			req->setPriority(priority);
-		}
-		else if(req->getStatus() == STATUS_QUEUED)
-		{
-			// remove from list then re-insert
-			llverify(mRequestQueue.erase(req) == 1);
-			req->setPriority(priority);
-			mRequestQueue.insert(req);
-		}
-	}
-	unlockData();
-}
-
 bool LLQueuedThread::completeRequest(handle_t handle)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	bool res = false;
 	lockData();
 	QueuedRequest* req = (QueuedRequest*)mRequestHash.find(handle);
@@ -399,88 +388,120 @@ bool LLQueuedThread::check()
 //============================================================================
 // Runs on its OWN thread
 
-size_t LLQueuedThread::processNextRequest()
+void LLQueuedThread::processRequest(LLQueuedThread::QueuedRequest* req)
 {
-	QueuedRequest *req;
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
+
+    mIdleThread = FALSE;
+    //threadedUpdate();
+
 	// Get next request from pool
 	lockData();
 	
-	while(1)
+	if ((req->getFlags() & FLAG_ABORT) || (mStatus == QUITTING))
 	{
-		req = NULL;
-		if (mRequestQueue.empty())
+        LL_PROFILE_ZONE_NAMED_CATEGORY_THREAD("qtpr - abort");
+		req->setStatus(STATUS_ABORTED);
+		req->finishRequest(false);
+		if (req->getFlags() & FLAG_AUTO_COMPLETE)
 		{
-			break;
-		}
-		req = *mRequestQueue.begin();
-		mRequestQueue.erase(mRequestQueue.begin());
-		if ((req->getFlags() & FLAG_ABORT) || (mStatus == QUITTING))
-		{
-			req->setStatus(STATUS_ABORTED);
-			req->finishRequest(false);
-			if (req->getFlags() & FLAG_AUTO_COMPLETE)
-			{
-				mRequestHash.erase(req);
-				req->deleteRequest();
+			mRequestHash.erase(req);
+			req->deleteRequest();
 // 				check();
-			}
-			continue;
 		}
-		llassert_always(req->getStatus() == STATUS_QUEUED);
-		break;
-	}
-	U32 start_priority = 0 ;
-	if (req)
-	{
-		req->setStatus(STATUS_INPROGRESS);
-		start_priority = req->getPriority();
-	}
-	unlockData();
-
-	// This is the only place we will call req->setStatus() after
-	// it has initially been seet to STATUS_QUEUED, so it is
-	// safe to access req.
-	if (req)
-	{
-		// process request		
-		bool complete = req->processRequest();
-
-		if (complete)
-		{
-			lockData();
-			req->setStatus(STATUS_COMPLETE);
-			req->finishRequest(true);
-			if (req->getFlags() & FLAG_AUTO_COMPLETE)
-			{
-				mRequestHash.erase(req);
-				req->deleteRequest();
-// 				check();
-			}
-			unlockData();
-		}
-		else
-		{
-			lockData();
-			req->setStatus(STATUS_QUEUED);
-			mRequestQueue.insert(req);
-			unlockData();
-			if (mThreaded && start_priority < PRIORITY_NORMAL)
-			{
-				ms_sleep(1); // sleep the thread a little
-			}
-		}
-		
-		LLTrace::get_thread_recorder()->pushToParent();
+        unlockData();
 	}
+    else
+    {
+        llassert_always(req->getStatus() == STATUS_QUEUED);
+
+        if (req)
+        {
+            req->setStatus(STATUS_INPROGRESS);
+        }
+        unlockData();
+
+        // This is the only place we will call req->setStatus() after
+        // it has initially been seet to STATUS_QUEUED, so it is
+        // safe to access req.
+        if (req)
+        {
+            // process request		
+            bool complete = req->processRequest();
+
+            if (complete)
+            {
+                LL_PROFILE_ZONE_NAMED_CATEGORY_THREAD("qtpr - complete");
+                lockData();
+                req->setStatus(STATUS_COMPLETE);
+                req->finishRequest(true);
+                if (req->getFlags() & FLAG_AUTO_COMPLETE)
+                {
+                    mRequestHash.erase(req);
+                    req->deleteRequest();
+                    // 				check();
+                }
+                unlockData();
+            }
+            else
+            {
+                LL_PROFILE_ZONE_NAMED_CATEGORY_THREAD("qtpr - retry");
+                //put back on queue and try again in 0.1ms
+                lockData();
+                req->setStatus(STATUS_QUEUED);
+                
+                unlockData();
+
+                llassert(!mDataLock->isSelfLocked());
+
+#if 0
+                // try again on next frame
+                // NOTE: tried using "post" with a time in the future, but this
+                // would invariably cause this thread to wait for a long time (10+ ms)
+                // while work is pending
+                bool ret = LL::WorkQueue::postMaybe(
+                    mMainQueue,
+                    [=]()
+                    {
+                        LL_PROFILE_ZONE_NAMED("processRequest - retry");
+                        mRequestQueue.post([=]()
+                            {
+                                LL_PROFILE_ZONE_NAMED("processRequest - retry"); // <-- not redundant, track retry on both queues
+                                processRequest(req);
+                            });
+                    });
+                llassert(ret);
+#else
+                using namespace std::chrono_literals;
+                auto retry_time = LL::WorkQueue::TimePoint::clock::now() + 16ms;
+                mRequestQueue.post([=]
+                    {
+                        LL_PROFILE_ZONE_NAMED("processRequest - retry");
+                        if (LL::WorkQueue::TimePoint::clock::now() < retry_time)
+                        {
+                            auto sleep_time = std::chrono::duration_cast<std::chrono::milliseconds>(retry_time - LL::WorkQueue::TimePoint::clock::now());
+                            
+                            if (sleep_time.count() > 0) 
+                            {
+                                ms_sleep(sleep_time.count());
+                            }
+                        }
+                        processRequest(req);
+                    });
+#endif
+                
+            }
+        }
+    }
 
-	return getPending();
+    mIdleThread = TRUE;
 }
 
 // virtual
 bool LLQueuedThread::runCondition()
 {
 	// mRunCondition must be locked here
-	if (mRequestQueue.empty() && mIdleThread)
+	if (mRequestQueue.size() == 0 && mIdleThread)
 		return false;
 	else
 		return true;
@@ -494,18 +515,13 @@ void LLQueuedThread::run()
 	startThread();
 	mStarted = TRUE;
 	
-	while (1)
+
+	/*while (1)
 	{
+        LL_PROFILE_ZONE_SCOPED;
 		// this will block on the condition until runCondition() returns true, the thread is unpaused, or the thread leaves the RUNNING state.
 		checkPause();
 		
-		if (isQuitting())
-		{
-			LLTrace::get_thread_recorder()->pushToParent();
-			endThread();
-			break;
-		}
-
 		mIdleThread = FALSE;
 
 		threadedUpdate();
@@ -514,12 +530,18 @@ void LLQueuedThread::run()
 
 		if (pending_work == 0)
 		{
+            //LL_PROFILE_ZONE_NAMED("LLQueuedThread - sleep");
 			mIdleThread = TRUE;
-			ms_sleep(1);
+			//ms_sleep(1);
 		}
 		//LLThread::yield(); // thread should yield after each request		
-	}
+	}*/
+    mRequestQueue.runUntilClose();
+
+    endThread();
 	LL_INFOS() << "LLQueuedThread " << mName << " EXITING." << LL_ENDL;
+
+    
 }
 
 // virtual
@@ -539,10 +561,9 @@ void LLQueuedThread::threadedUpdate()
 
 //============================================================================
 
-LLQueuedThread::QueuedRequest::QueuedRequest(LLQueuedThread::handle_t handle, U32 priority, U32 flags) :
+LLQueuedThread::QueuedRequest::QueuedRequest(LLQueuedThread::handle_t handle, U32 flags) :
 	LLSimpleHashEntry<LLQueuedThread::handle_t>(handle),
 	mStatus(STATUS_UNKNOWN),
-	mPriority(priority),
 	mFlags(flags)
 {
 }
diff --git a/indra/llcommon/llqueuedthread.h b/indra/llcommon/llqueuedthread.h
index 90fce3dc5d..814dbc4c38 100644
--- a/indra/llcommon/llqueuedthread.h
+++ b/indra/llcommon/llqueuedthread.h
@@ -36,6 +36,7 @@
 
 #include "llthread.h"
 #include "llsimplehash.h"
+#include "workqueue.h"
 
 //============================================================================
 // Note: ~LLQueuedThread is O(N) N=# of queued threads, assumed to be small
@@ -45,15 +46,6 @@ class LL_COMMON_API LLQueuedThread : public LLThread
 {
 	//------------------------------------------------------------------------
 public:
-	enum priority_t {
-		PRIORITY_IMMEDIATE = 0x7FFFFFFF,
-		PRIORITY_URGENT =    0x40000000,
-		PRIORITY_HIGH =      0x30000000,
-		PRIORITY_NORMAL =    0x20000000,
-		PRIORITY_LOW =       0x10000000,
-		PRIORITY_LOWBITS =   0x0FFFFFFF,
-		PRIORITY_HIGHBITS =  0x70000000
-	};
 	enum status_t {
 		STATUS_EXPIRED = -1,
 		STATUS_UNKNOWN = 0,
@@ -82,28 +74,17 @@ public:
 		virtual ~QueuedRequest(); // use deleteRequest()
 		
 	public:
-		QueuedRequest(handle_t handle, U32 priority, U32 flags = 0);
+		QueuedRequest(handle_t handle, U32 flags = 0);
 
 		status_t getStatus()
 		{
 			return mStatus;
 		}
-		U32 getPriority() const
-		{
-			return mPriority;
-		}
 		U32 getFlags() const
 		{
 			return mFlags;
 		}
-		bool higherPriority(const QueuedRequest& second) const
-		{
-			if ( mPriority == second.mPriority)
-				return mHashKey < second.mHashKey;
-			else
-				return mPriority > second.mPriority;
-		}
-
+		
 	protected:
 		status_t setStatus(status_t newstatus)
 		{
@@ -121,28 +102,11 @@ public:
 		virtual void finishRequest(bool completed); // Always called from thread after request has completed or aborted
 		virtual void deleteRequest(); // Only method to delete a request
 
-		void setPriority(U32 pri)
-		{
-			// Only do this on a request that is not in a queued list!
-			mPriority = pri;
-		};
-		
 	protected:
 		LLAtomicBase<status_t> mStatus;
-		U32 mPriority;
 		U32 mFlags;
 	};
 
-protected:
-	struct queued_request_less
-	{
-		bool operator()(const QueuedRequest* lhs, const QueuedRequest* rhs) const
-		{
-			return lhs->higherPriority(*rhs); // higher priority in front of queue (set)
-		}
-	};
-
-
 	//------------------------------------------------------------------------
 	
 public:
@@ -167,7 +131,7 @@ private:
 protected:
 	handle_t generateHandle();
 	bool addRequest(QueuedRequest* req);
-	size_t  processNextRequest(void);
+	void processRequest(QueuedRequest* req);
 	void incQueue();
 
 public:
@@ -186,7 +150,6 @@ public:
 	status_t getRequestStatus(handle_t handle);
 	void abortRequest(handle_t handle, bool autocomplete);
 	void setFlags(handle_t handle, U32 flags);
-	void setPriority(handle_t handle, U32 priority);
 	bool completeRequest(handle_t handle);
 	// This is public for support classes like LLWorkerThread,
 	// but generally the methods above should be used.
@@ -200,8 +163,10 @@ protected:
 	BOOL mStarted;  // required when mThreaded is false to call startThread() from update()
 	LLAtomicBool mIdleThread; // request queue is empty (or we are quitting) and the thread is idle
 	
-	typedef std::set<QueuedRequest*, queued_request_less> request_queue_t;
-	request_queue_t mRequestQueue;
+	//typedef std::set<QueuedRequest*, queued_request_less> request_queue_t;
+	//request_queue_t mRequestQueue;
+    LL::WorkQueue mRequestQueue;
+    LL::WorkQueue::weak_t mMainQueue;
 
 	enum { REQUEST_HASH_SIZE = 512 }; // must be power of 2
 	typedef LLSimpleHash<handle_t, REQUEST_HASH_SIZE> request_hash_t;
diff --git a/indra/llcommon/llsdserialize.cpp b/indra/llcommon/llsdserialize.cpp
index 3db456ddb3..a475be6293 100644
--- a/indra/llcommon/llsdserialize.cpp
+++ b/indra/llcommon/llsdserialize.cpp
@@ -475,6 +475,7 @@ LLSDNotationParser::~LLSDNotationParser()
 // virtual
 S32 LLSDNotationParser::doParse(std::istream& istr, LLSD& data, S32 max_depth) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 	// map: { string:object, string:object }
 	// array: [ object, object, object ]
 	// undef: !
@@ -734,6 +735,7 @@ S32 LLSDNotationParser::doParse(std::istream& istr, LLSD& data, S32 max_depth) c
 
 S32 LLSDNotationParser::parseMap(std::istream& istr, LLSD& map, S32 max_depth) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 	// map: { string:object, string:object }
 	map = LLSD::emptyMap();
 	S32 parse_count = 0;
@@ -794,6 +796,7 @@ S32 LLSDNotationParser::parseMap(std::istream& istr, LLSD& map, S32 max_depth) c
 
 S32 LLSDNotationParser::parseArray(std::istream& istr, LLSD& array, S32 max_depth) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 	// array: [ object, object, object ]
 	array = LLSD::emptyArray();
 	S32 parse_count = 0;
@@ -833,6 +836,7 @@ S32 LLSDNotationParser::parseArray(std::istream& istr, LLSD& array, S32 max_dept
 
 bool LLSDNotationParser::parseString(std::istream& istr, LLSD& data) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 	std::string value;
 	auto count = deserialize_string(istr, value, mMaxBytesLeft);
 	if(PARSE_FAILURE == count) return false;
@@ -843,6 +847,7 @@ bool LLSDNotationParser::parseString(std::istream& istr, LLSD& data) const
 
 bool LLSDNotationParser::parseBinary(std::istream& istr, LLSD& data) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 	// binary: b##"ff3120ab1"
 	// or: b(len)"..."
 
@@ -945,6 +950,7 @@ LLSDBinaryParser::~LLSDBinaryParser()
 // virtual
 S32 LLSDBinaryParser::doParse(std::istream& istr, LLSD& data, S32 max_depth) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
 /**
  * Undefined: '!'<br>
  * Boolean: '1' for true '0' for false<br>
diff --git a/indra/llcommon/llsdserialize_xml.cpp b/indra/llcommon/llsdserialize_xml.cpp
index ac128c9f86..38b11eb32b 100644
--- a/indra/llcommon/llsdserialize_xml.cpp
+++ b/indra/llcommon/llsdserialize_xml.cpp
@@ -923,6 +923,8 @@ void LLSDXMLParser::parsePart(const char *buf, llssize len)
 // virtual
 S32 LLSDXMLParser::doParse(std::istream& input, LLSD& data, S32 max_depth) const
 {
+	LL_PROFILE_ZONE_SCOPED_CATEGORY_LLSD
+
 	#ifdef XML_PARSER_PERFORMANCE_TESTS
 	XML_Timer timer( &parseTime );
 	#endif	// XML_PARSER_PERFORMANCE_TESTS
diff --git a/indra/llcommon/llsdutil.cpp b/indra/llcommon/llsdutil.cpp
index f70bee9903..e98fc0285a 100644
--- a/indra/llcommon/llsdutil.cpp
+++ b/indra/llcommon/llsdutil.cpp
@@ -1046,3 +1046,38 @@ LLSD llsd_shallow(LLSD value, LLSD filter)
 
     return shallow;
 }
+
+LLSD LL::apply_llsd_fix(size_t arity, const LLSD& args)
+{
+    // LLSD supports a number of types, two of which are aggregates: Map and
+    // Array. We don't try to support Map: supporting Map would seem to
+    // promise that we could somehow match the string key to 'func's parameter
+    // names. Uh sorry, maybe in some future version of C++ with reflection.
+    if (args.isMap())
+    {
+        LLTHROW(LL::apply_error("LL::apply(function, Map LLSD) unsupported"));
+    }
+    // We expect an LLSD array, but what the heck, treat isUndefined() as a
+    // zero-length array for calling a nullary 'func'.
+    if (args.isUndefined() || args.isArray())
+    {
+        // this works because LLSD().size() == 0
+        if (args.size() != arity)
+        {
+            LLTHROW(LL::apply_error(stringize("LL::apply(function(", arity, " args), ",
+                                              args.size(), "-entry LLSD array)")));
+        }
+        return args;
+    }
+
+    // args is one of the scalar types
+    // scalar_LLSD.size() == 0, so don't test that here.
+    // You can pass a scalar LLSD only to a unary 'func'.
+    if (arity != 1)
+    {
+        LLTHROW(LL::apply_error(stringize("LL::apply(function(", arity, " args), "
+                                          "LLSD ", LLSD::typeString(args.type()), ")")));
+    }
+    // make an array of it
+    return llsd::array(args);
+}
diff --git a/indra/llcommon/llsdutil.h b/indra/llcommon/llsdutil.h
index 372278c51a..ad54d1b0be 100644
--- a/indra/llcommon/llsdutil.h
+++ b/indra/llcommon/llsdutil.h
@@ -29,8 +29,14 @@
 #ifndef LL_LLSDUTIL_H
 #define LL_LLSDUTIL_H
 
+#include "apply.h"                  // LL::invoke()
+#include "function_types.h"         // LL::function_arity
 #include "llsd.h"
 #include <boost/functional/hash.hpp>
+#include <cassert>
+#include <memory>                   // std::shared_ptr
+#include <type_traits>
+#include <vector>
 
 // U32
 LL_COMMON_API LLSD ll_sd_from_U32(const U32);
@@ -298,6 +304,11 @@ LLSD map(Ts&&... vs)
 /*****************************************************************************
 *   LLSDParam
 *****************************************************************************/
+struct LLSDParamBase
+{
+    virtual ~LLSDParamBase() {}
+};
+
 /**
  * LLSDParam is a customization point for passing LLSD values to function
  * parameters of more or less arbitrary type. LLSD provides a small set of
@@ -315,7 +326,7 @@ LLSD map(Ts&&... vs)
  * @endcode
  */
 template <typename T>
-class LLSDParam
+class LLSDParam: public LLSDParamBase
 {
 public:
     /**
@@ -323,13 +334,66 @@ public:
      * value for later retrieval
      */
     LLSDParam(const LLSD& value):
-        _value(value)
+        value_(value)
     {}
 
-    operator T() const { return _value; }
+    operator T() const { return value_; }
 
 private:
-    T _value;
+    T value_;
+};
+
+/**
+ * LLSDParam<LLSD> is for when you don't already have the target parameter
+ * type in hand. Instantiate LLSDParam<LLSD>(your LLSD object), and the
+ * templated conversion operator will try to select a more specific LLSDParam
+ * specialization.
+ */
+template <>
+class LLSDParam<LLSD>: public LLSDParamBase
+{
+private:
+    LLSD value_;
+    // LLSDParam<LLSD>::operator T() works by instantiating an LLSDParam<T> on
+    // demand. Returning that engages LLSDParam<T>::operator T(), producing
+    // the desired result. But LLSDParam<const char*> owns a std::string whose
+    // c_str() is returned by its operator const char*(). If we return a temp
+    // LLSDParam<const char*>, the compiler can destroy it right away, as soon
+    // as we've called operator const char*(). That's a problem! That
+    // invalidates the const char* we've just passed to the subject function.
+    // This LLSDParam<LLSD> is presumably guaranteed to survive until the
+    // subject function has returned, so we must ensure that any constructed
+    // LLSDParam<T> lives just as long as this LLSDParam<LLSD> does. Putting
+    // each LLSDParam<T> on the heap and capturing a smart pointer in a vector
+    // works. We would have liked to use std::unique_ptr, but vector entries
+    // must be copyable.
+    // (Alternatively we could assume that every instance of LLSDParam<LLSD>
+    // will be asked for at most ONE conversion. We could store a scalar
+    // std::unique_ptr and, when constructing an new LLSDParam<T>, assert that
+    // the unique_ptr is empty. But some future change in usage patterns, and
+    // consequent failure of that assertion, would be very mysterious. Instead
+    // of explaining how to fix it, just fix it now.)
+    mutable std::vector<std::shared_ptr<LLSDParamBase>> converters_;
+
+public:
+    LLSDParam(const LLSD& value): value_(value) {}
+
+    /// if we're literally being asked for an LLSD parameter, avoid infinite
+    /// recursion
+    operator LLSD() const { return value_; }
+
+    /// otherwise, instantiate a more specific LLSDParam<T> to convert; that
+    /// preserves the existing customization mechanism
+    template <typename T>
+    operator T() const
+    {
+        // capture 'ptr' with the specific subclass type because converters_
+        // only stores LLSDParamBase pointers
+        auto ptr{ std::make_shared<LLSDParam<std::decay_t<T>>>(value_) };
+        // keep the new converter alive until we ourselves are destroyed
+        converters_.push_back(ptr);
+        return *ptr;
+    }
 };
 
 /**
@@ -346,17 +410,17 @@ private:
  */
 #define LLSDParam_for(T, AS)                    \
 template <>                                     \
-class LLSDParam<T>                              \
+class LLSDParam<T>: public LLSDParamBase        \
 {                                               \
 public:                                         \
     LLSDParam(const LLSD& value):               \
-        _value((T)value.AS())                      \
+        value_((T)value.AS())                   \
     {}                                          \
                                                 \
-    operator T() const { return _value; }       \
+    operator T() const { return value_; }       \
                                                 \
 private:                                        \
-    T _value;                                   \
+    T value_;                                   \
 }
 
 LLSDParam_for(float,        asReal);
@@ -372,31 +436,31 @@ LLSDParam_for(LLSD::Binary, asBinary);
  * safely pass an LLSDParam<const char*>(yourLLSD).
  */
 template <>
-class LLSDParam<const char*>
+class LLSDParam<const char*>: public LLSDParamBase
 {
 private:
     // The difference here is that we store a std::string rather than a const
     // char*. It's important that the LLSDParam object own the std::string.
-    std::string _value;
+    std::string value_;
     // We don't bother storing the incoming LLSD object, but we do have to
-    // distinguish whether _value is an empty string because the LLSD object
+    // distinguish whether value_ is an empty string because the LLSD object
     // contains an empty string or because it's isUndefined().
-    bool _undefined;
+    bool undefined_;
 
 public:
     LLSDParam(const LLSD& value):
-        _value(value),
-        _undefined(value.isUndefined())
+        value_(value),
+        undefined_(value.isUndefined())
     {}
 
-    // The const char* we retrieve is for storage owned by our _value member.
+    // The const char* we retrieve is for storage owned by our value_ member.
     // That's how we guarantee that the const char* is valid for the lifetime
     // of this LLSDParam object. Constructing your LLSDParam in the argument
     // list should ensure that the LLSDParam object will persist for the
     // duration of the function call.
     operator const char*() const
     {
-        if (_undefined)
+        if (undefined_)
         {
             // By default, an isUndefined() LLSD object's asString() method
             // will produce an empty string. But for a function accepting
@@ -406,7 +470,7 @@ public:
             // case, though, no LLSD value could pass NULL.
             return NULL;
         }
-        return _value.c_str();
+        return value_.c_str();
     }
 };
 
@@ -555,4 +619,56 @@ struct hash<LLSD>
     }
 };
 }
+
+namespace LL
+{
+
+/*****************************************************************************
+*   apply(function, LLSD array)
+*****************************************************************************/
+// validate incoming LLSD blob, and return an LLSD array suitable to pass to
+// the function of interest
+LLSD apply_llsd_fix(size_t arity, const LLSD& args);
+
+// Derived from https://stackoverflow.com/a/20441189
+// and https://en.cppreference.com/w/cpp/utility/apply .
+// We can't simply make a tuple from the LLSD array and then apply() that
+// tuple to the function -- how would make_tuple() deduce the correct
+// parameter type for each entry? We must go directly to the target function.
+template <typename CALLABLE, std::size_t... I>
+auto apply_impl(CALLABLE&& func, const LLSD& array, std::index_sequence<I...>)
+{
+    // call func(unpacked args), using generic LLSDParam<LLSD> to convert each
+    // entry in 'array' to the target parameter type
+    return std::forward<CALLABLE>(func)(LLSDParam<LLSD>(array[I])...);
+}
+
+// use apply_n<ARITY>(function, LLSD) to call a specific arity of a variadic
+// function with (that many) items from the passed LLSD array
+template <size_t ARITY, typename CALLABLE>
+auto apply_n(CALLABLE&& func, const LLSD& args)
+{
+    return apply_impl(std::forward<CALLABLE>(func),
+                      apply_llsd_fix(ARITY, args),
+                      std::make_index_sequence<ARITY>());
+}
+
+/**
+ * apply(function, LLSD) goes beyond C++17 std::apply(). For this case
+ * @a function @emph cannot be variadic: the compiler must know at compile
+ * time how many arguments to pass. This isn't Python. (But see apply_n() to
+ * pass a specific number of args to a variadic function.)
+ */
+template <typename CALLABLE>
+auto apply(CALLABLE&& func, const LLSD& args)
+{
+    // infer arity from the definition of func
+    constexpr auto arity = function_arity<
+        typename std::remove_reference<CALLABLE>::type>::value;
+    // now that we have a compile-time arity, apply_n() works
+    return apply_n<arity>(std::forward<CALLABLE>(func), args);
+}
+
+} // namespace LL
+
 #endif // LL_LLSDUTIL_H
diff --git a/indra/llcommon/llsys.cpp b/indra/llcommon/llsys.cpp
index 91cb65b815..938685bae6 100644
--- a/indra/llcommon/llsys.cpp
+++ b/indra/llcommon/llsys.cpp
@@ -771,20 +771,28 @@ static U32Kilobytes LLMemoryAdjustKBResult(U32Kilobytes inKB)
 }
 #endif
 
+#if LL_DARWIN
+// static
+U32Kilobytes LLMemoryInfo::getHardwareMemSize()
+{
+    // This might work on Linux as well.  Someone check...
+    uint64_t phys = 0;
+    int mib[2] = { CTL_HW, HW_MEMSIZE };
+
+    size_t len = sizeof(phys);
+    sysctl(mib, 2, &phys, &len, NULL, 0);
+
+    return U64Bytes(phys);
+}
+#endif
+
 U32Kilobytes LLMemoryInfo::getPhysicalMemoryKB() const
 {
 #if LL_WINDOWS
 	return LLMemoryAdjustKBResult(U32Kilobytes(mStatsMap["Total Physical KB"].asInteger()));
 
 #elif LL_DARWIN
-	// This might work on Linux as well.  Someone check...
-	uint64_t phys = 0;
-	int mib[2] = { CTL_HW, HW_MEMSIZE };
-
-	size_t len = sizeof(phys);	
-	sysctl(mib, 2, &phys, &len, NULL, 0);
-	
-	return U64Bytes(phys);
+    return getHardwareMemSize();
 
 #elif LL_LINUX
 	U64 phys = 0;
diff --git a/indra/llcommon/llsys.h b/indra/llcommon/llsys.h
index 70a03810c5..08d4abffa2 100644
--- a/indra/llcommon/llsys.h
+++ b/indra/llcommon/llsys.h
@@ -129,7 +129,10 @@ public:
 	LLMemoryInfo(); ///< Default constructor
 	void stream(std::ostream& s) const;	///< output text info to s
 
-	U32Kilobytes getPhysicalMemoryKB() const; 
+	U32Kilobytes getPhysicalMemoryKB() const;
+#if LL_DARWIN
+    static U32Kilobytes getHardwareMemSize(); // Because some Mac linkers won't let us reference extern gSysMemory from a different lib.
+#endif
 
 	//get the available memory infomation in KiloBytes.
 	static void getAvailableMemoryKB(U32Kilobytes& avail_physical_mem_kb, U32Kilobytes& avail_virtual_mem_kb);
diff --git a/indra/llcommon/llthread.cpp b/indra/llcommon/llthread.cpp
index a051c7f575..cd4975d9d3 100644
--- a/indra/llcommon/llthread.cpp
+++ b/indra/llcommon/llthread.cpp
@@ -42,6 +42,7 @@
 
 
 #ifdef LL_WINDOWS
+
 const DWORD MS_VC_EXCEPTION=0x406D1388;
 
 #pragma pack(push,8)
@@ -134,6 +135,15 @@ void LLThread::threadRun()
 {
 #ifdef LL_WINDOWS
     set_thread_name(-1, mName.c_str());
+
+#if 0 // probably a bad idea, see usage of SetThreadIdealProcessor in LLWindowWin32)
+    HANDLE hThread = GetCurrentThread();
+    if (hThread)
+    {
+        SetThreadAffinityMask(hThread, (DWORD_PTR) 0xFFFFFFFFFFFFFFFE);
+    }
+#endif
+
 #endif
 
     LL_PROFILER_SET_THREAD_NAME( mName.c_str() );
diff --git a/indra/llcommon/lltimer.cpp b/indra/llcommon/lltimer.cpp
index 58bedacf43..1a99ac2886 100644
--- a/indra/llcommon/lltimer.cpp
+++ b/indra/llcommon/lltimer.cpp
@@ -30,6 +30,9 @@
 
 #include "u64.h"
 
+#include <chrono>
+#include <thread>
+
 #if LL_WINDOWS
 #	include "llwin32headerslean.h"
 #elif LL_LINUX || LL_DARWIN
@@ -62,9 +65,18 @@ LLTimer* LLTimer::sTimer = NULL;
 //---------------------------------------------------------------------------
 
 #if LL_WINDOWS
+
+
+#if 0
 void ms_sleep(U32 ms)
 {
-	Sleep(ms);
+    LL_PROFILE_ZONE_SCOPED;
+    using TimePoint = std::chrono::steady_clock::time_point;
+    auto resume_time = TimePoint::clock::now() + std::chrono::milliseconds(ms);
+    while (TimePoint::clock::now() < resume_time)
+    {
+        std::this_thread::yield(); //note: don't use LLThread::yield here to avoid yielding for too long
+    }
 }
 
 U32 micro_sleep(U64 us, U32 max_yields)
@@ -74,6 +86,35 @@ U32 micro_sleep(U64 us, U32 max_yields)
 	ms_sleep((U32)(us / 1000));
     return 0;
 }
+
+#else
+
+U32 micro_sleep(U64 us, U32 max_yields)
+{
+    LL_PROFILE_ZONE_SCOPED
+#if 0
+    LARGE_INTEGER ft;
+    ft.QuadPart = -static_cast<S64>(us * 10);  // '-' using relative time
+
+    HANDLE timer = CreateWaitableTimer(NULL, TRUE, NULL);
+    SetWaitableTimer(timer, &ft, 0, NULL, NULL, 0);
+    WaitForSingleObject(timer, INFINITE);
+    CloseHandle(timer);
+#else
+    Sleep(us / 1000);
+#endif
+
+    return 0;
+}
+
+void ms_sleep(U32 ms)
+{
+    LL_PROFILE_ZONE_SCOPED
+    micro_sleep(ms * 1000, 0);
+}
+
+#endif
+
 #elif LL_LINUX || LL_DARWIN
 static void _sleep_loop(struct timespec& thiswait)
 {
diff --git a/indra/llcommon/lluuid.cpp b/indra/llcommon/lluuid.cpp
index 5655e8e2f2..200add404f 100644
--- a/indra/llcommon/lluuid.cpp
+++ b/indra/llcommon/lluuid.cpp
@@ -1,31 +1,31 @@
-/** 
+/**
  * @file lluuid.cpp
  *
  * $LicenseInfo:firstyear=2000&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2010, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
 
 #include "linden_common.h"
 
-// We can't use WIN32_LEAN_AND_MEAN here, needs lots of includes.
+ // We can't use WIN32_LEAN_AND_MEAN here, needs lots of includes.
 #if LL_WINDOWS
 #include "llwin32headers.h"
 // ugh, this is ugly.  We need to straighten out our linking for this library
@@ -51,7 +51,7 @@ const LLUUID LLUUID::null;
 const LLTransactionID LLTransactionID::tnull;
 
 // static 
-LLMutex * LLUUID::mMutex = NULL;
+LLMutex* LLUUID::mMutex = NULL;
 
 
 
@@ -60,15 +60,15 @@ LLMutex * LLUUID::mMutex = NULL;
 NOT DONE YET!!!
 
 static char BASE85_TABLE[] = {
-	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
-	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
-	'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
-	'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
-	'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
-	'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
-	'y', 'z', '!', '#', '$', '%', '&', '(', ')', '*',
-	'+', '-', ';', '[', '=', '>', '?', '@', '^', '_',
-	'`', '{', '|', '}', '~', '\0'
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
+    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
+    'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
+    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+    'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
+    'y', 'z', '!', '#', '$', '%', '&', '(', ')', '*',
+    '+', '-', ';', '[', '=', '>', '?', '@', '^', '_',
+    '`', '{', '|', '}', '~', '\0'
 };
 
 
@@ -94,28 +94,28 @@ return ret;
 
 void LLUUID::toBase85(char* out)
 {
-	U32* me = (U32*)&(mData[0]);
-	for(S32 i = 0; i < 4; ++i)
-	{
-		char* o = &out[i*i];
-		for(S32 j = 0; j < 5; ++j)
-		{
-			o[4-j] = BASE85_TABLE[ me[i] % 85];
-			word /= 85;
-		}
-	}
+    U32* me = (U32*)&(mData[0]);
+    for(S32 i = 0; i < 4; ++i)
+    {
+        char* o = &out[i*i];
+        for(S32 j = 0; j < 5; ++j)
+        {
+            o[4-j] = BASE85_TABLE[ me[i] % 85];
+            word /= 85;
+        }
+    }
 }
 
 unsigned int decode( char const * fiveChars ) throw( bad_input_data )
 {
-	unsigned int ret = 0;
-	for( S32 ix = 0; ix < 5; ++ix )
-	{
-		char * s = strchr( encodeTable, fiveChars[ ix ] );
-		ret = ret * 85 + (s-encodeTable);
-	}
-	return ret;
-} 
+    unsigned int ret = 0;
+    for( S32 ix = 0; ix < 5; ++ix )
+    {
+        char * s = strchr( encodeTable, fiveChars[ ix ] );
+        ret = ret * 85 + (s-encodeTable);
+    }
+    return ret;
+}
 */
 
 #define LL_USE_JANKY_RANDOM_NUMBER_GENERATOR 0
@@ -130,8 +130,8 @@ static U64 sJankyRandomSeed(LLUUID::getRandomSeed());
  */
 U32 janky_fast_random_bytes()
 {
-	sJankyRandomSeed = U64L(1664525) * sJankyRandomSeed + U64L(1013904223); 
-	return (U32)sJankyRandomSeed;
+    sJankyRandomSeed = U64L(1664525) * sJankyRandomSeed + U64L(1013904223);
+    return (U32)sJankyRandomSeed;
 }
 
 /**
@@ -139,8 +139,8 @@ U32 janky_fast_random_bytes()
  */
 U32 janky_fast_random_byes_range(U32 val)
 {
-	sJankyRandomSeed = U64L(1664525) * sJankyRandomSeed + U64L(1013904223); 
-	return (U32)(sJankyRandomSeed) % val; 
+    sJankyRandomSeed = U64L(1664525) * sJankyRandomSeed + U64L(1013904223);
+    return (U32)(sJankyRandomSeed) % val;
 }
 
 /**
@@ -148,257 +148,257 @@ U32 janky_fast_random_byes_range(U32 val)
  */
 U32 janky_fast_random_seeded_bytes(U32 seed, U32 val)
 {
-	seed = U64L(1664525) * (U64)(seed) + U64L(1013904223); 
-	return (U32)(seed) % val; 
+    seed = U64L(1664525) * (U64)(seed)+U64L(1013904223);
+    return (U32)(seed) % val;
 }
 #endif
 
 // Common to all UUID implementations
 void LLUUID::toString(std::string& out) const
 {
-	out = llformat(
-		"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
-		(U8)(mData[0]),
-		(U8)(mData[1]),
-		(U8)(mData[2]),
-		(U8)(mData[3]),
-		(U8)(mData[4]),
-		(U8)(mData[5]),
-		(U8)(mData[6]),
-		(U8)(mData[7]),
-		(U8)(mData[8]),
-		(U8)(mData[9]),
-		(U8)(mData[10]),
-		(U8)(mData[11]),
-		(U8)(mData[12]),
-		(U8)(mData[13]),
-		(U8)(mData[14]),
-		(U8)(mData[15]));
+    out = llformat(
+        "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+        (U8)(mData[0]),
+        (U8)(mData[1]),
+        (U8)(mData[2]),
+        (U8)(mData[3]),
+        (U8)(mData[4]),
+        (U8)(mData[5]),
+        (U8)(mData[6]),
+        (U8)(mData[7]),
+        (U8)(mData[8]),
+        (U8)(mData[9]),
+        (U8)(mData[10]),
+        (U8)(mData[11]),
+        (U8)(mData[12]),
+        (U8)(mData[13]),
+        (U8)(mData[14]),
+        (U8)(mData[15]));
 }
 
 // *TODO: deprecate
-void LLUUID::toString(char *out) const
+void LLUUID::toString(char* out) const
 {
-	std::string buffer;
-	toString(buffer);
-	strcpy(out,buffer.c_str()); /* Flawfinder: ignore */
+    std::string buffer;
+    toString(buffer);
+    strcpy(out, buffer.c_str()); /* Flawfinder: ignore */
 }
 
 void LLUUID::toCompressedString(std::string& out) const
 {
-	char bytes[UUID_BYTES+1];
-	memcpy(bytes, mData, UUID_BYTES);		/* Flawfinder: ignore */
-	bytes[UUID_BYTES] = '\0';
-	out.assign(bytes, UUID_BYTES);
+    char bytes[UUID_BYTES + 1];
+    memcpy(bytes, mData, UUID_BYTES);		/* Flawfinder: ignore */
+    bytes[UUID_BYTES] = '\0';
+    out.assign(bytes, UUID_BYTES);
 }
 
 // *TODO: deprecate
-void LLUUID::toCompressedString(char *out) const
+void LLUUID::toCompressedString(char* out) const
 {
-	memcpy(out, mData, UUID_BYTES);		/* Flawfinder: ignore */
-	out[UUID_BYTES] = '\0';
+    memcpy(out, mData, UUID_BYTES);		/* Flawfinder: ignore */
+    out[UUID_BYTES] = '\0';
 }
 
 std::string LLUUID::getString() const
 {
-	return asString();
+    return asString();
 }
 
 std::string LLUUID::asString() const
 {
-	std::string str;
-	toString(str);
-	return str;
+    std::string str;
+    toString(str);
+    return str;
 }
 
 BOOL LLUUID::set(const char* in_string, BOOL emit)
 {
-	return set(ll_safe_string(in_string),emit);
+    return set(ll_safe_string(in_string), emit);
 }
 
 BOOL LLUUID::set(const std::string& in_string, BOOL emit)
 {
-	BOOL broken_format = FALSE;
-
-	// empty strings should make NULL uuid
-	if (in_string.empty())
-	{
-		setNull();
-		return TRUE;
-	}
-
-	if (in_string.length() != (UUID_STR_LENGTH - 1))		/* Flawfinder: ignore */
-	{
-		// I'm a moron.  First implementation didn't have the right UUID format.
-		// Shouldn't see any of these any more
-		if (in_string.length() == (UUID_STR_LENGTH - 2))	/* Flawfinder: ignore */
-		{
-			if(emit)
-			{
-				LL_WARNS() << "Warning! Using broken UUID string format" << LL_ENDL;
-			}
-			broken_format = TRUE;
-		}
-		else
-		{
-			// Bad UUID string.  Spam as INFO, as most cases we don't care.
-			if(emit)
-			{
-				//don't spam the logs because a resident can't spell.
-				LL_WARNS() << "Bad UUID string: " << in_string << LL_ENDL;
-			}
-			setNull();
-			return FALSE;
-		}
-	}
-
-	U8 cur_pos = 0;
-	S32 i;
-	for (i = 0; i < UUID_BYTES; i++)
-	{
-		if ((i == 4) || (i == 6) || (i == 8) || (i == 10))
-		{
-			cur_pos++;
-			if (broken_format && (i==10))
-			{
-				// Missing - in the broken format
-				cur_pos--;
-			}
-		}
-
-		mData[i] = 0;
-
-		if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
-		{
-			mData[i] += (U8)(in_string[cur_pos] - '0');
-		}
-		else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <='f'))
-		{
-			mData[i] += (U8)(10 + in_string[cur_pos] - 'a');
-		}
-		else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <='F'))
-		{
-			mData[i] += (U8)(10 + in_string[cur_pos] - 'A');
-		}
-		else
-		{
-			if(emit)
-			{							
-				LL_WARNS() << "Invalid UUID string character" << LL_ENDL;
-			}
-			setNull();
-			return FALSE;
-		}
-
-		mData[i] = mData[i] << 4;
-		cur_pos++;
-
-		if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
-		{
-			mData[i] += (U8)(in_string[cur_pos] - '0');
-		}
-		else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <='f'))
-		{
-			mData[i] += (U8)(10 + in_string[cur_pos] - 'a');
-		}
-		else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <='F'))
-		{
-			mData[i] += (U8)(10 + in_string[cur_pos] - 'A');
-		}
-		else
-		{
-			if(emit)
-			{
-				LL_WARNS() << "Invalid UUID string character" << LL_ENDL;
-			}
-			setNull();
-			return FALSE;
-		}
-		cur_pos++;
-	}
-
-	return TRUE;
+    BOOL broken_format = FALSE;
+
+    // empty strings should make NULL uuid
+    if (in_string.empty())
+    {
+        setNull();
+        return TRUE;
+    }
+
+    if (in_string.length() != (UUID_STR_LENGTH - 1))		/* Flawfinder: ignore */
+    {
+        // I'm a moron.  First implementation didn't have the right UUID format.
+        // Shouldn't see any of these any more
+        if (in_string.length() == (UUID_STR_LENGTH - 2))	/* Flawfinder: ignore */
+        {
+            if (emit)
+            {
+                LL_WARNS() << "Warning! Using broken UUID string format" << LL_ENDL;
+            }
+            broken_format = TRUE;
+        }
+        else
+        {
+            // Bad UUID string.  Spam as INFO, as most cases we don't care.
+            if (emit)
+            {
+                //don't spam the logs because a resident can't spell.
+                LL_WARNS() << "Bad UUID string: " << in_string << LL_ENDL;
+            }
+            setNull();
+            return FALSE;
+        }
+    }
+
+    U8 cur_pos = 0;
+    S32 i;
+    for (i = 0; i < UUID_BYTES; i++)
+    {
+        if ((i == 4) || (i == 6) || (i == 8) || (i == 10))
+        {
+            cur_pos++;
+            if (broken_format && (i == 10))
+            {
+                // Missing - in the broken format
+                cur_pos--;
+            }
+        }
+
+        mData[i] = 0;
+
+        if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
+        {
+            mData[i] += (U8)(in_string[cur_pos] - '0');
+        }
+        else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <= 'f'))
+        {
+            mData[i] += (U8)(10 + in_string[cur_pos] - 'a');
+        }
+        else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <= 'F'))
+        {
+            mData[i] += (U8)(10 + in_string[cur_pos] - 'A');
+        }
+        else
+        {
+            if (emit)
+            {
+                LL_WARNS() << "Invalid UUID string character" << LL_ENDL;
+            }
+            setNull();
+            return FALSE;
+        }
+
+        mData[i] = mData[i] << 4;
+        cur_pos++;
+
+        if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
+        {
+            mData[i] += (U8)(in_string[cur_pos] - '0');
+        }
+        else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <= 'f'))
+        {
+            mData[i] += (U8)(10 + in_string[cur_pos] - 'a');
+        }
+        else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <= 'F'))
+        {
+            mData[i] += (U8)(10 + in_string[cur_pos] - 'A');
+        }
+        else
+        {
+            if (emit)
+            {
+                LL_WARNS() << "Invalid UUID string character" << LL_ENDL;
+            }
+            setNull();
+            return FALSE;
+        }
+        cur_pos++;
+    }
+
+    return TRUE;
 }
 
 BOOL LLUUID::validate(const std::string& in_string)
 {
-	BOOL broken_format = FALSE;
-	if (in_string.length() != (UUID_STR_LENGTH - 1))		/* Flawfinder: ignore */
-	{
-		// I'm a moron.  First implementation didn't have the right UUID format.
-		if (in_string.length() == (UUID_STR_LENGTH - 2))		/* Flawfinder: ignore */
-		{
-			broken_format = TRUE;
-		}
-		else
-		{
-			return FALSE;
-		}
-	}
-
-	U8 cur_pos = 0;
-	for (U32 i = 0; i < 16; i++)
-	{
-		if ((i == 4) || (i == 6) || (i == 8) || (i == 10))
-		{
-			cur_pos++;
-			if (broken_format && (i==10))
-			{
-				// Missing - in the broken format
-				cur_pos--;
-			}
-		}
-
-		if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
-		{
-		}
-		else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <='f'))
-		{
-		}
-		else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <='F'))
-		{
-		}
-		else
-		{
-			return FALSE;
-		}
-
-		cur_pos++;
-
-		if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
-		{
-		}
-		else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <='f'))
-		{
-		}
-		else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <='F'))
-		{
-		}
-		else
-		{
-			return FALSE;
-		}
-		cur_pos++;
-	}
-	return TRUE;
+    BOOL broken_format = FALSE;
+    if (in_string.length() != (UUID_STR_LENGTH - 1))		/* Flawfinder: ignore */
+    {
+        // I'm a moron.  First implementation didn't have the right UUID format.
+        if (in_string.length() == (UUID_STR_LENGTH - 2))		/* Flawfinder: ignore */
+        {
+            broken_format = TRUE;
+        }
+        else
+        {
+            return FALSE;
+        }
+    }
+
+    U8 cur_pos = 0;
+    for (U32 i = 0; i < 16; i++)
+    {
+        if ((i == 4) || (i == 6) || (i == 8) || (i == 10))
+        {
+            cur_pos++;
+            if (broken_format && (i == 10))
+            {
+                // Missing - in the broken format
+                cur_pos--;
+            }
+        }
+
+        if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
+        {
+        }
+        else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <= 'f'))
+        {
+        }
+        else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <= 'F'))
+        {
+        }
+        else
+        {
+            return FALSE;
+        }
+
+        cur_pos++;
+
+        if ((in_string[cur_pos] >= '0') && (in_string[cur_pos] <= '9'))
+        {
+        }
+        else if ((in_string[cur_pos] >= 'a') && (in_string[cur_pos] <= 'f'))
+        {
+        }
+        else if ((in_string[cur_pos] >= 'A') && (in_string[cur_pos] <= 'F'))
+        {
+        }
+        else
+        {
+            return FALSE;
+        }
+        cur_pos++;
+    }
+    return TRUE;
 }
 
 const LLUUID& LLUUID::operator^=(const LLUUID& rhs)
 {
-	U32* me = (U32*)&(mData[0]);
-	const U32* other = (U32*)&(rhs.mData[0]);
-	for(S32 i = 0; i < 4; ++i)
-	{
-		me[i] = me[i] ^ other[i];
-	}
-	return *this;
+    U32* me = (U32*)&(mData[0]);
+    const U32* other = (U32*)&(rhs.mData[0]);
+    for (S32 i = 0; i < 4; ++i)
+    {
+        me[i] = me[i] ^ other[i];
+    }
+    return *this;
 }
 
 LLUUID LLUUID::operator^(const LLUUID& rhs) const
 {
-	LLUUID id(*this);
-	id ^= rhs;
-	return id;
+    LLUUID id(*this);
+    id ^= rhs;
+    return id;
 }
 
 // WARNING: this algorithm SHALL NOT be changed. It is also used by the server
@@ -406,107 +406,107 @@ LLUUID LLUUID::operator^(const LLUUID& rhs) const
 // it would cause invalid assets.
 void LLUUID::combine(const LLUUID& other, LLUUID& result) const
 {
-	LLMD5 md5_uuid;
-	md5_uuid.update((unsigned char*)mData, 16);
-	md5_uuid.update((unsigned char*)other.mData, 16);
-	md5_uuid.finalize();
-	md5_uuid.raw_digest(result.mData);
+    LLMD5 md5_uuid;
+    md5_uuid.update((unsigned char*)mData, 16);
+    md5_uuid.update((unsigned char*)other.mData, 16);
+    md5_uuid.finalize();
+    md5_uuid.raw_digest(result.mData);
 }
 
-LLUUID LLUUID::combine(const LLUUID &other) const
+LLUUID LLUUID::combine(const LLUUID& other) const
 {
-	LLUUID combination;
-	combine(other, combination);
-	return combination;
+    LLUUID combination;
+    combine(other, combination);
+    return combination;
 }
 
-std::ostream& operator<<(std::ostream& s, const LLUUID &uuid)
+std::ostream& operator<<(std::ostream& s, const LLUUID& uuid)
 {
-	std::string uuid_str;
-	uuid.toString(uuid_str);
-	s << uuid_str;
-	return s;
+    std::string uuid_str;
+    uuid.toString(uuid_str);
+    s << uuid_str;
+    return s;
 }
 
-std::istream& operator>>(std::istream &s, LLUUID &uuid)
+std::istream& operator>>(std::istream& s, LLUUID& uuid)
 {
-	U32 i;
-	char uuid_str[UUID_STR_LENGTH];		/* Flawfinder: ignore */
-	for (i = 0; i < UUID_STR_LENGTH-1; i++)
-	{
-		s >> uuid_str[i];
-	}
-	uuid_str[i] = '\0';
-	uuid.set(std::string(uuid_str));
-	return s;
+    U32 i;
+    char uuid_str[UUID_STR_LENGTH];		/* Flawfinder: ignore */
+    for (i = 0; i < UUID_STR_LENGTH - 1; i++)
+    {
+        s >> uuid_str[i];
+    }
+    uuid_str[i] = '\0';
+    uuid.set(std::string(uuid_str));
+    return s;
 }
 
-static void get_random_bytes(void *buf, int nbytes)
+static void get_random_bytes(void* buf, int nbytes)
 {
-	int i;
-	char *cp = (char *) buf;
-
-	// *NOTE: If we are not using the janky generator ll_rand()
-	// generates at least 3 good bytes of data since it is 0 to
-	// RAND_MAX. This could be made more efficient by copying all the
-	// bytes.
-	for (i=0; i < nbytes; i++)
+    int i;
+    char* cp = (char*)buf;
+
+    // *NOTE: If we are not using the janky generator ll_rand()
+    // generates at least 3 good bytes of data since it is 0 to
+    // RAND_MAX. This could be made more efficient by copying all the
+    // bytes.
+    for (i = 0; i < nbytes; i++)
 #if LL_USE_JANKY_RANDOM_NUMBER_GENERATOR
-		*cp++ = janky_fast_random_bytes() & 0xFF;
+        * cp++ = janky_fast_random_bytes() & 0xFF;
 #else
-		*cp++ = ll_rand() & 0xFF;
+        * cp++ = ll_rand() & 0xFF;
 #endif
-	return;	
+    return;
 }
 
 #if	LL_WINDOWS
 
 typedef struct _ASTAT_
 {
-	ADAPTER_STATUS adapt;
-	NAME_BUFFER    NameBuff [30];
+    ADAPTER_STATUS adapt;
+    NAME_BUFFER    NameBuff[30];
 }ASTAT, * PASTAT;
 
 // static
-S32	LLUUID::getNodeID(unsigned char	*node_id)
+S32	LLUUID::getNodeID(unsigned char* node_id)
 {
-	ASTAT Adapter;
-	NCB Ncb;
-	UCHAR uRetCode;
-	LANA_ENUM   lenum;
-	int      i;
-	int retval = 0;
-
-	memset( &Ncb, 0, sizeof(Ncb) );
-	Ncb.ncb_command = NCBENUM;
-	Ncb.ncb_buffer = (UCHAR *)&lenum;
-	Ncb.ncb_length = sizeof(lenum);
-	uRetCode = Netbios( &Ncb );
-
-	for(i=0; i < lenum.length ;i++)
-	{
-		memset( &Ncb, 0, sizeof(Ncb) );
-		Ncb.ncb_command = NCBRESET;
-		Ncb.ncb_lana_num = lenum.lana[i];
-
-		uRetCode = Netbios( &Ncb );
-
-		memset( &Ncb, 0, sizeof (Ncb) );
-		Ncb.ncb_command = NCBASTAT;
-		Ncb.ncb_lana_num = lenum.lana[i];
-
-		strcpy( (char *)Ncb.ncb_callname,  "*              " );		/* Flawfinder: ignore */
-		Ncb.ncb_buffer = (unsigned char *)&Adapter;
-		Ncb.ncb_length = sizeof(Adapter);
-
-		uRetCode = Netbios( &Ncb );
-		if ( uRetCode == 0 )
-		{
-			memcpy(node_id,Adapter.adapt.adapter_address,6);		/* Flawfinder: ignore */
-			retval = 1;
-		}
-	}
-	return retval;
+    ASTAT Adapter;
+    NCB Ncb;
+    UCHAR uRetCode;
+    LANA_ENUM   lenum;
+    int      i;
+    int retval = 0;
+
+    memset(&Ncb, 0, sizeof(Ncb));
+    Ncb.ncb_command = NCBENUM;
+    Ncb.ncb_buffer = (UCHAR*)&lenum;
+    Ncb.ncb_length = sizeof(lenum);
+    uRetCode = Netbios(&Ncb);
+
+    for (i = 0; i < lenum.length; i++)
+    {
+        memset(&Ncb, 0, sizeof(Ncb));
+        Ncb.ncb_command = NCBRESET;
+        Ncb.ncb_lana_num = lenum.lana[i];
+
+        uRetCode = Netbios(&Ncb);
+
+        memset(&Ncb, 0, sizeof(Ncb));
+        Ncb.ncb_command = NCBASTAT;
+        Ncb.ncb_lana_num = lenum.lana[i];
+
+        strcpy((char*)Ncb.ncb_callname, "*              ");		/* Flawfinder: ignore */
+        Ncb.ncb_buffer = (unsigned char*)&Adapter;
+        Ncb.ncb_length = sizeof(Adapter);
+
+        uRetCode = Netbios(&Ncb);
+        if (uRetCode == 0)
+        {
+            memcpy(node_id, Adapter.adapt.adapter_address, 6);		/* Flawfinder: ignore */
+            retval = 1;
+        }
+    }
+    return retval;
 }
 
 #elif LL_DARWIN
@@ -525,66 +525,66 @@ S32	LLUUID::getNodeID(unsigned char	*node_id)
 #include <net/route.h>
 #include <ifaddrs.h>
 
-// static
-S32 LLUUID::getNodeID(unsigned char *node_id)
+ // static
+S32 LLUUID::getNodeID(unsigned char* node_id)
 {
-	int i;
-	unsigned char 	*a = NULL;
-	struct ifaddrs *ifap, *ifa;
-	int rv;
-	S32 result = 0;
-
-	if ((rv=getifaddrs(&ifap))==-1)
-	{       
-		return -1;
-	}
-	if (ifap == NULL)
-	{
-		return -1;
-	}
-
-	for (ifa = ifap; ifa != NULL; ifa = ifa->ifa_next)
-	{       
-//		printf("Interface %s, address family %d, ", ifa->ifa_name, ifa->ifa_addr->sa_family);
-		for(i=0; i< ifa->ifa_addr->sa_len; i++)
-		{
-//			printf("%02X ", (unsigned char)ifa->ifa_addr->sa_data[i]);
-		}
-//		printf("\n");
-		
-		if(ifa->ifa_addr->sa_family == AF_LINK)
-		{
-			// This is a link-level address
-			struct sockaddr_dl *lla = (struct sockaddr_dl *)ifa->ifa_addr;
-			
-//			printf("\tLink level address, type %02X\n", lla->sdl_type);
-
-			if(lla->sdl_type == IFT_ETHER)
-			{
-				// Use the first ethernet MAC in the list.
-				// For some reason, the macro LLADDR() defined in net/if_dl.h doesn't expand correctly.  This is what it would do.
-				a = (unsigned char *)&((lla)->sdl_data);
-				a += (lla)->sdl_nlen;
-				
-				if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
-				{
-					continue;
-				}
-
-				if (node_id) 
-				{
-					memcpy(node_id, a, 6);
-					result = 1;
-				}
-				
-				// We found one.
-				break;
-			}
-		}
-	}
-	freeifaddrs(ifap);
-
-	return result;
+    int i;
+    unsigned char* a = NULL;
+    struct ifaddrs* ifap, * ifa;
+    int rv;
+    S32 result = 0;
+
+    if ((rv = getifaddrs(&ifap)) == -1)
+    {
+        return -1;
+    }
+    if (ifap == NULL)
+    {
+        return -1;
+    }
+
+    for (ifa = ifap; ifa != NULL; ifa = ifa->ifa_next)
+    {
+        //		printf("Interface %s, address family %d, ", ifa->ifa_name, ifa->ifa_addr->sa_family);
+        for (i = 0; i < ifa->ifa_addr->sa_len; i++)
+        {
+            //			printf("%02X ", (unsigned char)ifa->ifa_addr->sa_data[i]);
+        }
+        //		printf("\n");
+
+        if (ifa->ifa_addr->sa_family == AF_LINK)
+        {
+            // This is a link-level address
+            struct sockaddr_dl* lla = (struct sockaddr_dl*)ifa->ifa_addr;
+
+            //			printf("\tLink level address, type %02X\n", lla->sdl_type);
+
+            if (lla->sdl_type == IFT_ETHER)
+            {
+                // Use the first ethernet MAC in the list.
+                // For some reason, the macro LLADDR() defined in net/if_dl.h doesn't expand correctly.  This is what it would do.
+                a = (unsigned char*)&((lla)->sdl_data);
+                a += (lla)->sdl_nlen;
+
+                if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
+                {
+                    continue;
+                }
+
+                if (node_id)
+                {
+                    memcpy(node_id, a, 6);
+                    result = 1;
+                }
+
+                // We found one.
+                break;
+            }
+        }
+    }
+    freeifaddrs(ifap);
+
+    return result;
 }
 
 #else
@@ -611,22 +611,22 @@ S32 LLUUID::getNodeID(unsigned char *node_id)
 #endif
 #endif
 
-// static
-S32 LLUUID::getNodeID(unsigned char *node_id)
+ // static
+S32 LLUUID::getNodeID(unsigned char* node_id)
 {
-	int 		sd;
-	struct ifreq 	ifr, *ifrp;
-	struct ifconf 	ifc;
-	char buf[1024];
-	int		n, i;
-	unsigned char 	*a;
-	
-/*
- * BSD 4.4 defines the size of an ifreq to be
- * max(sizeof(ifreq), sizeof(ifreq.ifr_name)+ifreq.ifr_addr.sa_len
- * However, under earlier systems, sa_len isn't present, so the size is 
- * just sizeof(struct ifreq)
- */
+    int 		sd;
+    struct ifreq 	ifr, * ifrp;
+    struct ifconf 	ifc;
+    char buf[1024];
+    int		n, i;
+    unsigned char* a;
+
+    /*
+     * BSD 4.4 defines the size of an ifreq to be
+     * max(sizeof(ifreq), sizeof(ifreq.ifr_name)+ifreq.ifr_addr.sa_len
+     * However, under earlier systems, sa_len isn't present, so the size is
+     * just sizeof(struct ifreq)
+     */
 #ifdef HAVE_SA_LEN
 #ifndef max
 #define max(a,b) ((a) > (b) ? (a) : (b))
@@ -637,252 +637,253 @@ S32 LLUUID::getNodeID(unsigned char *node_id)
 #define ifreq_size(i) sizeof(struct ifreq)
 #endif /* HAVE_SA_LEN*/
 
-	sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
-	if (sd < 0) {
-		return -1;
-	}
-	memset(buf, 0, sizeof(buf));
-	ifc.ifc_len = sizeof(buf);
-	ifc.ifc_buf = buf;
-	if (ioctl (sd, SIOCGIFCONF, (char *)&ifc) < 0) {
-		close(sd);
-		return -1;
-	}
-	n = ifc.ifc_len;
-	for (i = 0; i < n; i+= ifreq_size(*ifr) ) {
-		ifrp = (struct ifreq *)((char *) ifc.ifc_buf+i);
-		strncpy(ifr.ifr_name, ifrp->ifr_name, IFNAMSIZ);		/* Flawfinder: ignore */
+    sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
+    if (sd < 0) {
+        return -1;
+    }
+    memset(buf, 0, sizeof(buf));
+    ifc.ifc_len = sizeof(buf);
+    ifc.ifc_buf = buf;
+    if (ioctl(sd, SIOCGIFCONF, (char*)&ifc) < 0) {
+        close(sd);
+        return -1;
+    }
+    n = ifc.ifc_len;
+    for (i = 0; i < n; i += ifreq_size(*ifr)) {
+        ifrp = (struct ifreq*)((char*)ifc.ifc_buf + i);
+        strncpy(ifr.ifr_name, ifrp->ifr_name, IFNAMSIZ);		/* Flawfinder: ignore */
 #ifdef SIOCGIFHWADDR
-		if (ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
-			continue;
-		a = (unsigned char *) &ifr.ifr_hwaddr.sa_data;
+        if (ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
+            continue;
+        a = (unsigned char*)&ifr.ifr_hwaddr.sa_data;
 #else
 #ifdef SIOCGENADDR
-		if (ioctl(sd, SIOCGENADDR, &ifr) < 0)
-			continue;
-		a = (unsigned char *) ifr.ifr_enaddr;
+        if (ioctl(sd, SIOCGENADDR, &ifr) < 0)
+            continue;
+        a = (unsigned char*)ifr.ifr_enaddr;
 #else
-		/*
-		 * XXX we don't have a way of getting the hardware
-		 * address
-		 */
-		close(sd);
-		return 0;
+        /*
+         * XXX we don't have a way of getting the hardware
+         * address
+         */
+        close(sd);
+        return 0;
 #endif /* SIOCGENADDR */
 #endif /* SIOCGIFHWADDR */
-		if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
-			continue;
-		if (node_id) {
-			memcpy(node_id, a, 6);		/* Flawfinder: ignore */
-			close(sd);
-			return 1;
-		}
-	}
-	close(sd);
-	return 0;
+        if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
+            continue;
+        if (node_id) {
+            memcpy(node_id, a, 6);		/* Flawfinder: ignore */
+            close(sd);
+            return 1;
+        }
+    }
+    close(sd);
+    return 0;
 }
 
 #endif
 
-S32 LLUUID::cmpTime(uuid_time_t *t1, uuid_time_t *t2)
+S32 LLUUID::cmpTime(uuid_time_t* t1, uuid_time_t* t2)
 {
-   // Compare two time values.
+    // Compare two time values.
 
-   if (t1->high < t2->high) return -1;
-   if (t1->high > t2->high) return 1;
-   if (t1->low  < t2->low)  return -1;
-   if (t1->low  > t2->low)  return 1;
-   return 0;
+    if (t1->high < t2->high) return -1;
+    if (t1->high > t2->high) return 1;
+    if (t1->low < t2->low)  return -1;
+    if (t1->low > t2->low)  return 1;
+    return 0;
 }
 
-void LLUUID::getSystemTime(uuid_time_t *timestamp)
+void LLUUID::getSystemTime(uuid_time_t* timestamp)
 {
-   // Get system time with 100ns precision. Time is since Oct 15, 1582.
+    // Get system time with 100ns precision. Time is since Oct 15, 1582.
 #if LL_WINDOWS
-   ULARGE_INTEGER time;
-   GetSystemTimeAsFileTime((FILETIME *)&time);
-   // NT keeps time in FILETIME format which is 100ns ticks since
-   // Jan 1, 1601. UUIDs use time in 100ns ticks since Oct 15, 1582.
-   // The difference is 17 Days in Oct + 30 (Nov) + 31 (Dec)
-   // + 18 years and 5 leap days.
-   time.QuadPart +=
-            (unsigned __int64) (1000*1000*10)       // seconds
-          * (unsigned __int64) (60 * 60 * 24)       // days
-          * (unsigned __int64) (17+30+31+365*18+5); // # of days
-
-   timestamp->high = time.HighPart;
-   timestamp->low  = time.LowPart;
+    ULARGE_INTEGER time;
+    GetSystemTimeAsFileTime((FILETIME*)&time);
+    // NT keeps time in FILETIME format which is 100ns ticks since
+    // Jan 1, 1601. UUIDs use time in 100ns ticks since Oct 15, 1582.
+    // The difference is 17 Days in Oct + 30 (Nov) + 31 (Dec)
+    // + 18 years and 5 leap days.
+    time.QuadPart +=
+        (unsigned __int64)(1000 * 1000 * 10)       // seconds
+        * (unsigned __int64)(60 * 60 * 24)       // days
+        * (unsigned __int64)(17 + 30 + 31 + 365 * 18 + 5); // # of days
+
+    timestamp->high = time.HighPart;
+    timestamp->low = time.LowPart;
 #else
-   struct timeval tp;
-   gettimeofday(&tp, 0);
-
-   // Offset between UUID formatted times and Unix formatted times.
-   // UUID UTC base time is October 15, 1582.
-   // Unix base time is January 1, 1970.
-   U64 uuid_time = ((U64)tp.tv_sec * 10000000) + (tp.tv_usec * 10) +
-                           U64L(0x01B21DD213814000);
-   timestamp->high = (U32) (uuid_time >> 32);
-   timestamp->low  = (U32) (uuid_time & 0xFFFFFFFF);
+    struct timeval tp;
+    gettimeofday(&tp, 0);
+
+    // Offset between UUID formatted times and Unix formatted times.
+    // UUID UTC base time is October 15, 1582.
+    // Unix base time is January 1, 1970.
+    U64 uuid_time = ((U64)tp.tv_sec * 10000000) + (tp.tv_usec * 10) +
+        U64L(0x01B21DD213814000);
+    timestamp->high = (U32)(uuid_time >> 32);
+    timestamp->low = (U32)(uuid_time & 0xFFFFFFFF);
 #endif
 }
 
-void LLUUID::getCurrentTime(uuid_time_t *timestamp)
+void LLUUID::getCurrentTime(uuid_time_t* timestamp)
 {
-   // Get current time as 60 bit 100ns ticks since whenever.
-   // Compensate for the fact that real clock resolution is less
-   // than 100ns.
-
-   const U32 uuids_per_tick = 1024;
-
-   static uuid_time_t time_last;
-   static U32    uuids_this_tick;
-   static BOOL     init = FALSE;
-
-   if (!init) {
-      getSystemTime(&time_last);
-      uuids_this_tick = uuids_per_tick;
-      init = TRUE;
-      mMutex = new LLMutex();
-   }
-
-   uuid_time_t time_now = {0,0};
-
-   while (1) {
-      getSystemTime(&time_now);
-
-      // if clock reading changed since last UUID generated
-      if (cmpTime(&time_last, &time_now))  {
-         // reset count of uuid's generated with this clock reading
-         uuids_this_tick = 0;
-         break;
-      }
-      if (uuids_this_tick < uuids_per_tick) {
-         uuids_this_tick++;
-         break;
-      }
-      // going too fast for our clock; spin
-   }
-
-   time_last = time_now;
-
-   if (uuids_this_tick != 0) {
-      if (time_now.low & 0x80000000) {
-         time_now.low += uuids_this_tick;
-         if (!(time_now.low & 0x80000000))
-            time_now.high++;
-      } else
-         time_now.low += uuids_this_tick;
-   }
-
-   timestamp->high = time_now.high;
-   timestamp->low  = time_now.low;
+    // Get current time as 60 bit 100ns ticks since whenever.
+    // Compensate for the fact that real clock resolution is less
+    // than 100ns.
+
+    const U32 uuids_per_tick = 1024;
+
+    static uuid_time_t time_last;
+    static U32    uuids_this_tick;
+    static BOOL     init = FALSE;
+
+    if (!init) {
+        getSystemTime(&time_last);
+        uuids_this_tick = uuids_per_tick;
+        init = TRUE;
+        mMutex = new LLMutex();
+    }
+
+    uuid_time_t time_now = { 0,0 };
+
+    while (1) {
+        getSystemTime(&time_now);
+
+        // if clock reading changed since last UUID generated
+        if (cmpTime(&time_last, &time_now)) {
+            // reset count of uuid's generated with this clock reading
+            uuids_this_tick = 0;
+            break;
+        }
+        if (uuids_this_tick < uuids_per_tick) {
+            uuids_this_tick++;
+            break;
+        }
+        // going too fast for our clock; spin
+    }
+
+    time_last = time_now;
+
+    if (uuids_this_tick != 0) {
+        if (time_now.low & 0x80000000) {
+            time_now.low += uuids_this_tick;
+            if (!(time_now.low & 0x80000000))
+                time_now.high++;
+        }
+        else
+            time_now.low += uuids_this_tick;
+    }
+
+    timestamp->high = time_now.high;
+    timestamp->low = time_now.low;
 }
 
 void LLUUID::generate()
 {
-	// Create a UUID.
-	uuid_time_t timestamp;
-
-	static unsigned char node_id[6];	/* Flawfinder: ignore */
-	static int has_init = 0;
-   
-	// Create a UUID.
-	static uuid_time_t time_last = {0,0};
-	static U16 clock_seq = 0;
+    // Create a UUID.
+    uuid_time_t timestamp;
+
+    static unsigned char node_id[6];	/* Flawfinder: ignore */
+    static int has_init = 0;
+
+    // Create a UUID.
+    static uuid_time_t time_last = { 0,0 };
+    static U16 clock_seq = 0;
 #if LL_USE_JANKY_RANDOM_NUMBER_GENERATOR
-	static U32 seed = 0L; // dummy seed.  reset it below
+    static U32 seed = 0L; // dummy seed.  reset it below
 #endif
-	if (!has_init) 
-	{
-		has_init = 1;
-		if (getNodeID(node_id) <= 0) 
-		{
-			get_random_bytes(node_id, 6);
-			/*
-			 * Set multicast bit, to prevent conflicts
-			 * with IEEE 802 addresses obtained from
-			 * network cards
-			 */
-			node_id[0] |= 0x80;
-		}
-
-		getCurrentTime(&time_last);
+    if (!has_init)
+    {
+        has_init = 1;
+        if (getNodeID(node_id) <= 0)
+        {
+            get_random_bytes(node_id, 6);
+            /*
+             * Set multicast bit, to prevent conflicts
+             * with IEEE 802 addresses obtained from
+             * network cards
+             */
+            node_id[0] |= 0x80;
+        }
+
+        getCurrentTime(&time_last);
 #if LL_USE_JANKY_RANDOM_NUMBER_GENERATOR
-		seed = time_last.low;
+        seed = time_last.low;
 #endif
 
 #if LL_USE_JANKY_RANDOM_NUMBER_GENERATOR
-		clock_seq = (U16)janky_fast_random_seeded_bytes(seed, 65536);
+        clock_seq = (U16)janky_fast_random_seeded_bytes(seed, 65536);
 #else
-		clock_seq = (U16)ll_rand(65536);
+        clock_seq = (U16)ll_rand(65536);
 #endif
-	}
-
-	// get current time
-	getCurrentTime(&timestamp);
-	U16 our_clock_seq = clock_seq;
-
-	// if clock hasn't changed or went backward, change clockseq
-	if (cmpTime(&timestamp, &time_last) != 1) 
-	{
-		LLMutexLock	lock(mMutex);
-		clock_seq = (clock_seq + 1) & 0x3FFF;
-		if (clock_seq == 0) 
-			clock_seq++;
-		our_clock_seq = clock_seq;	// Ensure we're using a different clock_seq value from previous time
-	}
+    }
+
+    // get current time
+    getCurrentTime(&timestamp);
+    U16 our_clock_seq = clock_seq;
+
+    // if clock hasn't changed or went backward, change clockseq
+    if (cmpTime(&timestamp, &time_last) != 1)
+    {
+        LLMutexLock	lock(mMutex);
+        clock_seq = (clock_seq + 1) & 0x3FFF;
+        if (clock_seq == 0)
+            clock_seq++;
+        our_clock_seq = clock_seq;	// Ensure we're using a different clock_seq value from previous time
+    }
 
     time_last = timestamp;
 
-	memcpy(mData+10, node_id, 6);		/* Flawfinder: ignore */
-	U32 tmp;
-	tmp = timestamp.low;
-	mData[3] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[2] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[1] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[0] = (unsigned char) tmp;
-	
-	tmp = (U16) timestamp.high;
-	mData[5] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[4] = (unsigned char) tmp;
-
-	tmp = (timestamp.high >> 16) | 0x1000;
-	mData[7] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[6] = (unsigned char) tmp;
-
-	tmp = our_clock_seq;
-
-	mData[9] = (unsigned char) tmp;
-	tmp >>= 8;
-	mData[8] = (unsigned char) tmp;
-
-	HBXXH128::digest(*this, (const void*)mData, 16);
+    memcpy(mData + 10, node_id, 6);		/* Flawfinder: ignore */
+    U32 tmp;
+    tmp = timestamp.low;
+    mData[3] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[2] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[1] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[0] = (unsigned char)tmp;
+
+    tmp = (U16)timestamp.high;
+    mData[5] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[4] = (unsigned char)tmp;
+
+    tmp = (timestamp.high >> 16) | 0x1000;
+    mData[7] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[6] = (unsigned char)tmp;
+
+    tmp = our_clock_seq;
+
+    mData[9] = (unsigned char)tmp;
+    tmp >>= 8;
+    mData[8] = (unsigned char)tmp;
+
+    HBXXH128::digest(*this, (const void*)mData, 16);
 }
 
 void LLUUID::generate(const std::string& hash_string)
 {
-	HBXXH128::digest(*this, hash_string);
+    HBXXH128::digest(*this, hash_string);
 }
 
 U32 LLUUID::getRandomSeed()
 {
-   static unsigned char seed[16];		/* Flawfinder: ignore */
-   
-   getNodeID(&seed[0]);
+    static unsigned char seed[16];		/* Flawfinder: ignore */
+
+    getNodeID(&seed[0]);
 
-   // Incorporate the pid into the seed to prevent
-   // processes that start on the same host at the same
-   // time from generating the same seed.
-   pid_t pid = LLApp::getPid();
+    // Incorporate the pid into the seed to prevent
+    // processes that start on the same host at the same
+    // time from generating the same seed.
+    pid_t pid = LLApp::getPid();
 
-   seed[6]=(unsigned char)(pid >> 8);
-   seed[7]=(unsigned char)(pid);
-   getSystemTime((uuid_time_t *)(&seed[8]));
+    seed[6] = (unsigned char)(pid >> 8);
+    seed[7] = (unsigned char)(pid);
+    getSystemTime((uuid_time_t*)(&seed[8]));
 
    U64 seed64 = HBXXH64::digest((const void*)seed, 16);
    return U32(seed64) ^ U32(seed64 >> 32);
@@ -890,92 +891,92 @@ U32 LLUUID::getRandomSeed()
 
 BOOL LLUUID::parseUUID(const std::string& buf, LLUUID* value)
 {
-	if( buf.empty() || value == NULL)
-	{
-		return FALSE;
-	}
-
-	std::string temp( buf );
-	LLStringUtil::trim(temp);
-	if( LLUUID::validate( temp ) )
-	{
-		value->set( temp );
-		return TRUE;
-	}
-	return FALSE;
+    if (buf.empty() || value == NULL)
+    {
+        return FALSE;
+    }
+
+    std::string temp(buf);
+    LLStringUtil::trim(temp);
+    if (LLUUID::validate(temp))
+    {
+        value->set(temp);
+        return TRUE;
+    }
+    return FALSE;
 }
 
 //static
 LLUUID LLUUID::generateNewID(std::string hash_string)
 {
-	LLUUID new_id;
-	if (hash_string.empty())
-	{
-		new_id.generate();
-	}
-	else
-	{
-		new_id.generate(hash_string);
-	}
-	return new_id;
+    LLUUID new_id;
+    if (hash_string.empty())
+    {
+        new_id.generate();
+    }
+    else
+    {
+        new_id.generate(hash_string);
+    }
+    return new_id;
 }
 
 LLAssetID LLTransactionID::makeAssetID(const LLUUID& session) const
 {
-	LLAssetID result;
-	if (isNull())
-	{
-		result.setNull();
-	}
-	else
-	{
-		combine(session, result);
-	}
-	return result;
+    LLAssetID result;
+    if (isNull())
+    {
+        result.setNull();
+    }
+    else
+    {
+        combine(session, result);
+    }
+    return result;
 }
 
 // Construct
 LLUUID::LLUUID()
 {
-	setNull();
+    setNull();
 }
 
 
 // Faster than copying from memory
- void LLUUID::setNull()
+void LLUUID::setNull()
 {
-	U32 *word = (U32 *)mData;
-	word[0] = 0;
-	word[1] = 0;
-	word[2] = 0;
-	word[3] = 0;
+    U32* word = (U32*)mData;
+    word[0] = 0;
+    word[1] = 0;
+    word[2] = 0;
+    word[3] = 0;
 }
 
 
 // Compare
- bool LLUUID::operator==(const LLUUID& rhs) const
+bool LLUUID::operator==(const LLUUID& rhs) const
 {
-	U32 *tmp = (U32 *)mData;
-	U32 *rhstmp = (U32 *)rhs.mData;
-	// Note: binary & to avoid branching
-	return 
-		(tmp[0] == rhstmp[0]) &  
-		(tmp[1] == rhstmp[1]) &
-		(tmp[2] == rhstmp[2]) &
-		(tmp[3] == rhstmp[3]);
+    U32* tmp = (U32*)mData;
+    U32* rhstmp = (U32*)rhs.mData;
+    // Note: binary & to avoid branching
+    return
+        (tmp[0] == rhstmp[0]) &
+        (tmp[1] == rhstmp[1]) &
+        (tmp[2] == rhstmp[2]) &
+        (tmp[3] == rhstmp[3]);
 }
 
 
- bool LLUUID::operator!=(const LLUUID& rhs) const
+bool LLUUID::operator!=(const LLUUID& rhs) const
 {
-	U32 *tmp = (U32 *)mData;
-	U32 *rhstmp = (U32 *)rhs.mData;
-	// Note: binary | to avoid branching
-	return 
-		(tmp[0] != rhstmp[0]) |
-		(tmp[1] != rhstmp[1]) |
-		(tmp[2] != rhstmp[2]) |
-		(tmp[3] != rhstmp[3]);
+    U32* tmp = (U32*)mData;
+    U32* rhstmp = (U32*)rhs.mData;
+    // Note: binary | to avoid branching
+    return
+        (tmp[0] != rhstmp[0]) |
+        (tmp[1] != rhstmp[1]) |
+        (tmp[2] != rhstmp[2]) |
+        (tmp[3] != rhstmp[3]);
 }
 
 /*
@@ -983,94 +984,94 @@ LLUUID::LLUUID()
 // to integers, among other things.  Use isNull() or notNull().
  LLUUID::operator bool() const
 {
-	U32 *word = (U32 *)mData;
-	return (word[0] | word[1] | word[2] | word[3]) > 0;
+    U32 *word = (U32 *)mData;
+    return (word[0] | word[1] | word[2] | word[3]) > 0;
 }
 */
 
- BOOL LLUUID::notNull() const
+BOOL LLUUID::notNull() const
 {
-	U32 *word = (U32 *)mData;
-	return (word[0] | word[1] | word[2] | word[3]) > 0;
+    U32* word = (U32*)mData;
+    return (word[0] | word[1] | word[2] | word[3]) > 0;
 }
 
 // Faster than == LLUUID::null because doesn't require
 // as much memory access.
- BOOL LLUUID::isNull() const
+BOOL LLUUID::isNull() const
 {
-	U32 *word = (U32 *)mData;
-	// If all bits are zero, return !0 == TRUE
-	return !(word[0] | word[1] | word[2] | word[3]);
+    U32* word = (U32*)mData;
+    // If all bits are zero, return !0 == TRUE
+    return !(word[0] | word[1] | word[2] | word[3]);
 }
 
- LLUUID::LLUUID(const char *in_string)
+LLUUID::LLUUID(const char* in_string)
 {
-	if (!in_string || in_string[0] == 0)
-	{
-		setNull();
-		return;
-	}
- 
-	set(in_string);
+    if (!in_string || in_string[0] == 0)
+    {
+        setNull();
+        return;
+    }
+
+    set(in_string);
 }
 
- LLUUID::LLUUID(const std::string& in_string)
+LLUUID::LLUUID(const std::string& in_string)
 {
-	if (in_string.empty())
-	{
-		setNull();
-		return;
-	}
+    if (in_string.empty())
+    {
+        setNull();
+        return;
+    }
 
-	set(in_string);
+    set(in_string);
 }
 
 // IW: DON'T "optimize" these w/ U32s or you'll scoogie the sort order
 // IW: this will make me very sad
- bool LLUUID::operator<(const LLUUID &rhs) const
+bool LLUUID::operator<(const LLUUID& rhs) const
 {
-	U32 i;
-	for( i = 0; i < (UUID_BYTES - 1); i++ )
-	{
-		if( mData[i] != rhs.mData[i] )
-		{
-			return (mData[i] < rhs.mData[i]);
-		}
-	}
-	return (mData[UUID_BYTES - 1] < rhs.mData[UUID_BYTES - 1]);
+    U32 i;
+    for (i = 0; i < (UUID_BYTES - 1); i++)
+    {
+        if (mData[i] != rhs.mData[i])
+        {
+            return (mData[i] < rhs.mData[i]);
+        }
+    }
+    return (mData[UUID_BYTES - 1] < rhs.mData[UUID_BYTES - 1]);
 }
 
- bool LLUUID::operator>(const LLUUID &rhs) const
+bool LLUUID::operator>(const LLUUID& rhs) const
 {
-	U32 i;
-	for( i = 0; i < (UUID_BYTES - 1); i++ )
-	{
-		if( mData[i] != rhs.mData[i] )
-		{
-			return (mData[i] > rhs.mData[i]);
-		}
-	}
-	return (mData[UUID_BYTES - 1] > rhs.mData[UUID_BYTES - 1]);
+    U32 i;
+    for (i = 0; i < (UUID_BYTES - 1); i++)
+    {
+        if (mData[i] != rhs.mData[i])
+        {
+            return (mData[i] > rhs.mData[i]);
+        }
+    }
+    return (mData[UUID_BYTES - 1] > rhs.mData[UUID_BYTES - 1]);
 }
 
- U16 LLUUID::getCRC16() const
+U16 LLUUID::getCRC16() const
 {
-	// A UUID is 16 bytes, or 8 shorts.
-	U16 *short_data = (U16*)mData;
-	U16 out = 0;
-	out += short_data[0];
-	out += short_data[1];
-	out += short_data[2];
-	out += short_data[3];
-	out += short_data[4];
-	out += short_data[5];
-	out += short_data[6];
-	out += short_data[7];
-	return out;
+    // A UUID is 16 bytes, or 8 shorts.
+    U16* short_data = (U16*)mData;
+    U16 out = 0;
+    out += short_data[0];
+    out += short_data[1];
+    out += short_data[2];
+    out += short_data[3];
+    out += short_data[4];
+    out += short_data[5];
+    out += short_data[6];
+    out += short_data[7];
+    return out;
 }
 
- U32 LLUUID::getCRC32() const
+U32 LLUUID::getCRC32() const
 {
-	U32 *tmp = (U32*)mData;
-	return tmp[0] + tmp[1] + tmp[2] + tmp[3];
+    U32* tmp = (U32*)mData;
+    return tmp[0] + tmp[1] + tmp[2] + tmp[3];
 }
diff --git a/indra/llcommon/llworkerthread.cpp b/indra/llcommon/llworkerthread.cpp
index e5eda1eac7..06c74bdba0 100644
--- a/indra/llcommon/llworkerthread.cpp
+++ b/indra/llcommon/llworkerthread.cpp
@@ -73,6 +73,7 @@ void LLWorkerThread::clearDeleteList()
 		{
 			worker->mRequestHandle = LLWorkerThread::nullHandle();
 			worker->clearFlags(LLWorkerClass::WCF_HAVE_WORK);
+			worker->clearFlags(LLWorkerClass::WCF_WORKING);
 			delete worker;
 		}
 		mDeleteList.clear() ;
@@ -97,6 +98,7 @@ size_t LLWorkerThread::update(F32 max_time_ms)
 		{
 			if (worker->getFlags(LLWorkerClass::WCF_WORK_FINISHED))
 			{
+                worker->setFlags(LLWorkerClass::WCF_DELETE_REQUESTED);
 				delete_list.push_back(worker);
 				mDeleteList.erase(curiter);
 			}
@@ -130,11 +132,11 @@ size_t LLWorkerThread::update(F32 max_time_ms)
 
 //----------------------------------------------------------------------------
 
-LLWorkerThread::handle_t LLWorkerThread::addWorkRequest(LLWorkerClass* workerclass, S32 param, U32 priority)
+LLWorkerThread::handle_t LLWorkerThread::addWorkRequest(LLWorkerClass* workerclass, S32 param)
 {
 	handle_t handle = generateHandle();
 	
-	WorkRequest* req = new WorkRequest(handle, priority, workerclass, param);
+	WorkRequest* req = new WorkRequest(handle, workerclass, param);
 
 	bool res = addRequest(req);
 	if (!res)
@@ -157,8 +159,8 @@ void LLWorkerThread::deleteWorker(LLWorkerClass* workerclass)
 //============================================================================
 // Runs on its OWN thread
 
-LLWorkerThread::WorkRequest::WorkRequest(handle_t handle, U32 priority, LLWorkerClass* workerclass, S32 param) :
-	LLQueuedThread::QueuedRequest(handle, priority),
+LLWorkerThread::WorkRequest::WorkRequest(handle_t handle, LLWorkerClass* workerclass, S32 param) :
+	LLQueuedThread::QueuedRequest(handle),
 	mWorkerClass(workerclass),
 	mParam(param)
 {
@@ -177,6 +179,7 @@ void LLWorkerThread::WorkRequest::deleteRequest()
 // virtual
 bool LLWorkerThread::WorkRequest::processRequest()
 {
+    LL_PROFILE_ZONE_SCOPED;
 	LLWorkerClass* workerclass = getWorkerClass();
 	workerclass->setWorking(true);
 	bool complete = workerclass->doWork(getParam());
@@ -187,6 +190,7 @@ bool LLWorkerThread::WorkRequest::processRequest()
 // virtual
 void LLWorkerThread::WorkRequest::finishRequest(bool completed)
 {
+    LL_PROFILE_ZONE_SCOPED;
 	LLWorkerClass* workerclass = getWorkerClass();
 	workerclass->finishWork(getParam(), completed);
 	U32 flags = LLWorkerClass::WCF_WORK_FINISHED | (completed ? 0 : LLWorkerClass::WCF_WORK_ABORTED);
@@ -200,7 +204,6 @@ LLWorkerClass::LLWorkerClass(LLWorkerThread* workerthread, const std::string& na
 	: mWorkerThread(workerthread),
 	  mWorkerClassName(name),
 	  mRequestHandle(LLWorkerThread::nullHandle()),
-	  mRequestPriority(LLWorkerThread::PRIORITY_NORMAL),
 	  mMutex(),
 	  mWorkFlags(0)
 {
@@ -289,7 +292,7 @@ bool LLWorkerClass::yield()
 //----------------------------------------------------------------------------
 
 // calls startWork, adds doWork() to queue
-void LLWorkerClass::addWork(S32 param, U32 priority)
+void LLWorkerClass::addWork(S32 param)
 {
 	mMutex.lock();
 	llassert_always(!(mWorkFlags & (WCF_WORKING|WCF_HAVE_WORK)));
@@ -303,7 +306,7 @@ void LLWorkerClass::addWork(S32 param, U32 priority)
 	startWork(param);
 	clearFlags(WCF_WORK_FINISHED|WCF_WORK_ABORTED);
 	setFlags(WCF_HAVE_WORK);
-	mRequestHandle = mWorkerThread->addWorkRequest(this, param, priority);
+	mRequestHandle = mWorkerThread->addWorkRequest(this, param);
 	mMutex.unlock();
 }
 
@@ -318,7 +321,6 @@ void LLWorkerClass::abortWork(bool autocomplete)
 	if (mRequestHandle != LLWorkerThread::nullHandle())
 	{
 		mWorkerThread->abortRequest(mRequestHandle, autocomplete);
-		mWorkerThread->setPriority(mRequestHandle, LLQueuedThread::PRIORITY_IMMEDIATE);
 		setFlags(WCF_ABORT_REQUESTED);
 	}
 	mMutex.unlock();
@@ -392,16 +394,5 @@ void LLWorkerClass::scheduleDelete()
 	}
 }
 
-void LLWorkerClass::setPriority(U32 priority)
-{
-	mMutex.lock();
-	if (mRequestHandle != LLWorkerThread::nullHandle() && mRequestPriority != priority)
-	{
-		mRequestPriority = priority;
-		mWorkerThread->setPriority(mRequestHandle, priority);
-	}
-	mMutex.unlock();
-}
-
 //============================================================================
 
diff --git a/indra/llcommon/llworkerthread.h b/indra/llcommon/llworkerthread.h
index e3004d7242..bf94c84090 100644
--- a/indra/llcommon/llworkerthread.h
+++ b/indra/llcommon/llworkerthread.h
@@ -56,7 +56,7 @@ public:
 		virtual ~WorkRequest(); // use deleteRequest()
 		
 	public:
-		WorkRequest(handle_t handle, U32 priority, LLWorkerClass* workerclass, S32 param);
+		WorkRequest(handle_t handle, LLWorkerClass* workerclass, S32 param);
 
 		S32 getParam()
 		{
@@ -90,7 +90,7 @@ public:
 
 	/*virtual*/ size_t update(F32 max_time_ms);
 	
-	handle_t addWorkRequest(LLWorkerClass* workerclass, S32 param, U32 priority = PRIORITY_NORMAL);
+	handle_t addWorkRequest(LLWorkerClass* workerclass, S32 param);
 	
 	S32 getNumDeletes() { return (S32)mDeleteList.size(); } // debug
 
@@ -151,10 +151,6 @@ public:
 	bool isWorking() { return getFlags(WCF_WORKING); }
 	bool wasAborted() { return getFlags(WCF_ABORT_REQUESTED); }
 
-	// setPriority(): changes the priority of a request
-	void setPriority(U32 priority);
-	U32  getPriority() { return mRequestPriority; }
-		
 	const std::string& getName() const { return mWorkerClassName; }
 
 protected:
@@ -169,7 +165,7 @@ protected:
 	void setWorkerThread(LLWorkerThread* workerthread);
 
 	// addWork(): calls startWork, adds doWork() to queue
-	void addWork(S32 param, U32 priority = LLWorkerThread::PRIORITY_NORMAL);
+	void addWork(S32 param);
 
 	// abortWork(): requests that work be aborted
 	void abortWork(bool autocomplete);
@@ -193,7 +189,6 @@ protected:
 	LLWorkerThread* mWorkerThread;
 	std::string mWorkerClassName;
 	handle_t mRequestHandle;
-	U32 mRequestPriority; // last priority set
 
 private:
 	LLMutex mMutex;
diff --git a/indra/llcommon/tests/apply_test.cpp b/indra/llcommon/tests/apply_test.cpp
new file mode 100644
index 0000000000..56b497e0c8
--- /dev/null
+++ b/indra/llcommon/tests/apply_test.cpp
@@ -0,0 +1,240 @@
+/**
+ * @file   apply_test.cpp
+ * @author Nat Goodspeed
+ * @date   2022-12-19
+ * @brief  Test for apply.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "apply.h"
+// STL headers
+// std headers
+#include <iomanip>
+// external library headers
+// other Linden headers
+#include "llsd.h"
+#include "llsdutil.h"
+#include <array>
+#include <string>
+#include <vector>
+
+// for ensure_equals
+std::ostream& operator<<(std::ostream& out, const std::vector<std::string>& stringvec)
+{
+    const char* delim = "[";
+    for (const auto& str : stringvec)
+    {
+        out << delim << std::quoted(str);
+        delim = ", ";
+    }
+    return out << ']';
+}
+
+// the above must be declared BEFORE ensure_equals(std::vector<std::string>)
+#include "../test/lltut.h"
+
+/*****************************************************************************
+*   TUT
+*****************************************************************************/
+namespace tut
+{
+    namespace statics
+    {
+        /*------------------------------ data ------------------------------*/
+        // Although we're using types from the LLSD namespace, we're not
+        // constructing LLSD values, but rather instances of the C++ types
+        // supported by LLSD.
+        static LLSD::Boolean b{true};
+        static LLSD::Integer i{17};
+        static LLSD::Real    f{3.14};
+        static LLSD::String  s{ "hello" };
+        static LLSD::UUID    uu{ "baadf00d-dead-beef-baad-feedb0ef" };
+        static LLSD::Date    dt{ "2022-12-19" };
+        static LLSD::URI     uri{ "http://secondlife.com" };
+        static LLSD::Binary  bin{ 0x01, 0x02, 0x03, 0x04, 0x05 };
+
+        static std::vector<LLSD::String> quick
+        {
+            "The", "quick", "brown", "fox", "etc."
+        };
+
+        static std::array<int, 5> fibs
+        {
+            0, 1, 1, 2, 3
+        };
+
+        // ensure that apply() actually reaches the target method --
+        // lack of ensure_equals() failure could be due to no-op apply()
+        bool called{ false };
+        // capture calls from collect()
+        std::vector<std::string> collected;
+
+        /*------------------------- test functions -------------------------*/
+        void various(LLSD::Boolean b, LLSD::Integer i, LLSD::Real f, const LLSD::String& s,
+                     const LLSD::UUID& uu, const LLSD::Date& dt,
+                     const LLSD::URI& uri, const LLSD::Binary& bin)
+        {
+            called = true;
+            ensure_equals(  "b mismatch", b,   statics::b);
+            ensure_equals(  "i mismatch", i,   statics::i);
+            ensure_equals(  "f mismatch", f,   statics::f);
+            ensure_equals(  "s mismatch", s,   statics::s);
+            ensure_equals( "uu mismatch", uu,  statics::uu);
+            ensure_equals( "dt mismatch", dt,  statics::dt);
+            ensure_equals("uri mismatch", uri, statics::uri);
+            ensure_equals("bin mismatch", bin, statics::bin);
+        }
+
+        void strings(std::string s0, std::string s1, std::string s2, std::string s3, std::string s4)
+        {
+            called = true;
+            ensure_equals("s0 mismatch", s0, statics::quick[0]);
+            ensure_equals("s1 mismatch", s1, statics::quick[1]);
+            ensure_equals("s2 mismatch", s2, statics::quick[2]);
+            ensure_equals("s3 mismatch", s3, statics::quick[3]);
+            ensure_equals("s4 mismatch", s4, statics::quick[4]);
+        }
+
+        void ints(int i0, int i1, int i2, int i3, int i4)
+        {
+            called = true;
+            ensure_equals("i0 mismatch", i0, statics::fibs[0]);
+            ensure_equals("i1 mismatch", i1, statics::fibs[1]);
+            ensure_equals("i2 mismatch", i2, statics::fibs[2]);
+            ensure_equals("i3 mismatch", i3, statics::fibs[3]);
+            ensure_equals("i4 mismatch", i4, statics::fibs[4]);
+        }
+
+        void sdfunc(const LLSD& sd)
+        {
+            called = true;
+            ensure_equals("sd mismatch", sd.asInteger(), statics::i);
+        }
+
+        void intfunc(int i)
+        {
+            called = true;
+            ensure_equals("i mismatch", i, statics::i);
+        }
+
+        void voidfunc()
+        {
+            called = true;
+        }
+
+        // recursion tail
+        void collect()
+        {
+            called = true;
+        }
+
+        // collect(arbitrary)
+        template <typename... ARGS>
+        void collect(const std::string& first, ARGS&&... rest)
+        {
+            statics::collected.push_back(first);
+            collect(std::forward<ARGS>(rest)...);
+        }
+    } // namespace statics
+
+    struct apply_data
+    {
+        apply_data()
+        {
+            // reset called before each test
+            statics::called = false;
+            statics::collected.clear();
+        }
+    };
+    typedef test_group<apply_data> apply_group;
+    typedef apply_group::object object;
+    apply_group applygrp("apply");
+
+    template<> template<>
+    void object::test<1>()
+    {
+        set_test_name("apply(tuple)");
+        LL::apply(statics::various,
+                  std::make_tuple(statics::b, statics::i, statics::f, statics::s,
+                                  statics::uu, statics::dt, statics::uri, statics::bin));
+        ensure("apply(tuple) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<2>()
+    {
+        set_test_name("apply(array)");
+        LL::apply(statics::ints, statics::fibs);
+        ensure("apply(array) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<3>()
+    {
+        set_test_name("apply(vector)");
+        LL::apply(statics::strings, statics::quick);
+        ensure("apply(vector) failed", statics::called);
+    }
+
+    // The various apply(LLSD) tests exercise only the success cases because
+    // the failure cases trigger assert() fail, which is hard to catch.
+    template<> template<>
+    void object::test<4>()
+    {
+        set_test_name("apply(LLSD())");
+        LL::apply(statics::voidfunc, LLSD());
+        ensure("apply(LLSD()) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<5>()
+    {
+        set_test_name("apply(fn(int), LLSD scalar)");
+        LL::apply(statics::intfunc, LLSD(statics::i));
+        ensure("apply(fn(int), LLSD scalar) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<6>()
+    {
+        set_test_name("apply(fn(LLSD), LLSD scalar)");
+        // This test verifies that LLSDParam<LLSD> doesn't send the compiler
+        // into infinite recursion when the target is itself LLSD.
+        LL::apply(statics::sdfunc, LLSD(statics::i));
+        ensure("apply(fn(LLSD), LLSD scalar) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<7>()
+    {
+        set_test_name("apply(LLSD array)");
+        LL::apply(statics::various,
+                  llsd::array(statics::b, statics::i, statics::f, statics::s,
+                              statics::uu, statics::dt, statics::uri, statics::bin));
+        ensure("apply(LLSD array) failed", statics::called);
+    }
+
+    template<> template<>
+    void object::test<8>()
+    {
+        set_test_name("VAPPLY()");
+        // Make a std::array<std::string> from statics::quick. We can't call a
+        // variadic function with a data structure of dynamic length.
+        std::array<std::string, 5> strray;
+        for (size_t i = 0; i < strray.size(); ++i)
+            strray[i] = statics::quick[i];
+        // This doesn't work: the compiler doesn't know which overload of
+        // collect() to pass to LL::apply().
+        // LL::apply(statics::collect, strray);
+        // That's what VAPPLY() is for.
+        VAPPLY(statics::collect, strray);
+        ensure("VAPPLY() failed", statics::called);
+        ensure_equals("collected mismatch", statics::collected, statics::quick);
+    }
+} // namespace tut
diff --git a/indra/llcommon/tests/lazyeventapi_test.cpp b/indra/llcommon/tests/lazyeventapi_test.cpp
new file mode 100644
index 0000000000..31b2d6d17f
--- /dev/null
+++ b/indra/llcommon/tests/lazyeventapi_test.cpp
@@ -0,0 +1,136 @@
+/**
+ * @file   lazyeventapi_test.cpp
+ * @author Nat Goodspeed
+ * @date   2022-06-18
+ * @brief  Test for lazyeventapi.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "lazyeventapi.h"
+// STL headers
+// std headers
+// external library headers
+// other Linden headers
+#include "../test/lltut.h"
+#include "llevents.h"
+#include "llsdutil.h"
+
+// observable side effect, solely for testing
+static LLSD data;
+
+// LLEventAPI listener subclass
+class MyListener: public LLEventAPI
+{
+public:
+    // need this trivial forwarding constructor
+    // (of course do any other initialization your subclass requires)
+    MyListener(const LL::LazyEventAPIParams& params):
+        LLEventAPI(params)
+    {}
+
+    // example operation, registered by LazyEventAPI subclass below
+    void set_data(const LLSD& event)
+    {
+        data = event["data"];
+    }
+};
+
+// LazyEventAPI registrar subclass
+class MyRegistrar: public LL::LazyEventAPI<MyListener>
+{
+    using super = LL::LazyEventAPI<MyListener>;
+    using super::listener;
+public:
+    // LazyEventAPI subclass initializes like a classic LLEventAPI subclass
+    // constructor, with API name and desc plus add() calls for the defined
+    // operations
+    MyRegistrar():
+        super("Test", "This is a test LLEventAPI")
+    {
+        add("set", "This is a set operation", &listener::set_data);
+    }
+};
+// Normally we'd declare a static instance of MyRegistrar -- but because we
+// want to test both with and without, defer declaration to individual test
+// methods.
+
+/*****************************************************************************
+*   TUT
+*****************************************************************************/
+namespace tut
+{
+    struct lazyeventapi_data
+    {
+        lazyeventapi_data()
+        {
+            // before every test, reset 'data'
+            data.clear();
+        }
+        ~lazyeventapi_data()
+        {
+            // after every test, reset LLEventPumps
+            LLEventPumps::deleteSingleton();
+        }
+    };
+    typedef test_group<lazyeventapi_data> lazyeventapi_group;
+    typedef lazyeventapi_group::object object;
+    lazyeventapi_group lazyeventapigrp("lazyeventapi");
+
+    template<> template<>
+    void object::test<1>()
+    {
+        set_test_name("LazyEventAPI");
+        // this is where the magic (should) happen
+        // 'register' still a keyword until C++17
+        MyRegistrar regster;
+        LLEventPumps::instance().obtain("Test").post(llsd::map("op", "set", "data", "hey"));
+        ensure_equals("failed to set data", data.asString(), "hey");
+    }
+
+    template<> template<>
+    void object::test<2>()
+    {
+        set_test_name("No LazyEventAPI");
+        // Because the MyRegistrar declaration in test<1>() is local, because
+        // it has been destroyed, we fully expect NOT to reach a MyListener
+        // instance with this post.
+        LLEventPumps::instance().obtain("Test").post(llsd::map("op", "set", "data", "moot"));
+        ensure("accidentally set data", ! data.isDefined());
+    }
+
+    template<> template<>
+    void object::test<3>()
+    {
+        set_test_name("LazyEventAPI metadata");
+        MyRegistrar regster;
+        // Of course we have 'regster' in hand; we don't need to search for
+        // it. But this next test verifies that we can find (all) LazyEventAPI
+        // instances using LazyEventAPIBase::instance_snapshot. Normally we
+        // wouldn't search; normally we'd just look at each instance in the
+        // loop body.
+        const MyRegistrar* found = nullptr;
+        for (const auto& registrar : LL::LazyEventAPIBase::instance_snapshot())
+            if ((found = dynamic_cast<const MyRegistrar*>(&registrar)))
+                break;
+        ensure("Failed to find MyRegistrar via LLInstanceTracker", found);
+
+        ensure_equals("wrong API name", found->getName(), "Test");
+        ensure_contains("wrong API desc", found->getDesc(), "test LLEventAPI");
+        ensure_equals("wrong API field", found->getDispatchKey(), "op");
+        // Normally we'd just iterate over *found. But for test purposes,
+        // actually capture the range of NameDesc pairs in a vector.
+        std::vector<LL::LazyEventAPIBase::NameDesc> ops{ found->begin(), found->end() };
+        ensure_equals("failed to find operations", ops.size(), 1);
+        ensure_equals("wrong operation name", ops[0].first, "set");
+        ensure_contains("wrong operation desc", ops[0].second, "set operation");
+        LLSD metadata{ found->getMetadata(ops[0].first) };
+        ensure_equals("bad metadata name", metadata["name"].asString(), ops[0].first);
+        ensure_equals("bad metadata desc", metadata["desc"].asString(), ops[0].second);
+    }
+} // namespace tut
diff --git a/indra/llcommon/tests/lleventdispatcher_test.cpp b/indra/llcommon/tests/lleventdispatcher_test.cpp
index 466f11f52a..b0c532887c 100644
--- a/indra/llcommon/tests/lleventdispatcher_test.cpp
+++ b/indra/llcommon/tests/lleventdispatcher_test.cpp
@@ -18,9 +18,12 @@
 // external library headers
 // other Linden headers
 #include "../test/lltut.h"
+#include "lleventfilter.h"
 #include "llsd.h"
 #include "llsdutil.h"
+#include "llevents.h"
 #include "stringize.h"
+#include "StringVec.h"
 #include "tests/wrapllerrs.h"
 #include "../test/catch_and_store_what_in.h"
 #include "../test/debug.h"
@@ -32,8 +35,6 @@
 #include <boost/bind.hpp>
 #include <boost/function.hpp>
 #include <boost/range.hpp>
-#include <boost/foreach.hpp>
-#define foreach BOOST_FOREACH
 
 #include <boost/lambda/lambda.hpp>
 
@@ -177,6 +178,7 @@ struct Vars
     /*-------- Arbitrary-params (non-const, const, static) methods ---------*/
     void methodna(NPARAMSa)
     {
+        DEBUG;
         // Because our const char* param cp might be NULL, and because we
         // intend to capture the value in a std::string, have to distinguish
         // between the NULL value and any non-NULL value. Use a convention
@@ -188,7 +190,7 @@ struct Vars
         else
             vcp = std::string("'") + cp + "'";
 
-        debug()("methodna(", b,
+        this->debug()("methodna(", b,
               ", ", i,
               ", ", f,
               ", ", d,
@@ -205,7 +207,7 @@ struct Vars
     void methodnb(NPARAMSb)
     {
         std::ostringstream vbin;
-        foreach(U8 byte, bin)
+        for (U8 byte: bin)
         {
             vbin << std::hex << std::setfill('0') << std::setw(2) << unsigned(byte);
         }
@@ -226,7 +228,8 @@ struct Vars
 
     void cmethodna(NPARAMSa) const
     {
-        debug()('c', NONL);
+        DEBUG;
+        this->debug()('c', NONL);
         const_cast<Vars*>(this)->methodna(NARGSa);
     }
 
@@ -315,6 +318,31 @@ void freenb(NPARAMSb)
 *****************************************************************************/
 namespace tut
 {
+    void ensure_has(const std::string& outer, const std::string& inner)
+    {
+        ensure(stringize("'", outer, "' does not contain '", inner, "'"),
+               outer.find(inner) != std::string::npos);
+    }
+
+    template <typename CALLABLE>
+    std::string call_exc(CALLABLE&& func, const std::string& exc_frag)
+    {
+        std::string what =
+            catch_what<LLEventDispatcher::DispatchError>(std::forward<CALLABLE>(func));
+        ensure_has(what, exc_frag);
+        return what;
+    }
+
+    template <typename CALLABLE>
+    void call_logerr(CALLABLE&& func, const std::string& frag)
+    {
+        CaptureLog capture;
+        // the error should be logged; we just need to stop the exception
+        // propagating
+        catch_what<LLEventDispatcher::DispatchError>(std::forward<CALLABLE>(func));
+        capture.messageWith(frag);
+    }
+
     struct lleventdispatcher_data
     {
         Debug debug{"test"};
@@ -397,9 +425,9 @@ namespace tut
             work.add(name, desc, &Dispatcher::cmethod1, required);
             // Non-subclass method with/out required params
             addf("method1", "method1", &v);
-            work.add(name, desc, boost::bind(&Vars::method1, boost::ref(v), _1));
+            work.add(name, desc, [this](const LLSD& args){ return v.method1(args); });
             addf("method1_req", "method1", &v);
-            work.add(name, desc, boost::bind(&Vars::method1, boost::ref(v), _1), required);
+            work.add(name, desc, [this](const LLSD& args){ return v.method1(args); }, required);
 
             /*--------------- Arbitrary params, array style ----------------*/
 
@@ -461,7 +489,7 @@ namespace tut
             debug("dft_array_full:\n",
                   dft_array_full);
             // Partial defaults arrays.
-            foreach(LLSD::String a, ab)
+            for (LLSD::String a: ab)
             {
                 LLSD::Integer partition(std::min(partial_offset, dft_array_full[a].size()));
                 dft_array_partial[a] =
@@ -471,7 +499,7 @@ namespace tut
             debug("dft_array_partial:\n",
                   dft_array_partial);
 
-            foreach(LLSD::String a, ab)
+            for(LLSD::String a: ab)
             {
                 // Generate full defaults maps by zipping (params, dft_array_full).
                 dft_map_full[a] = zipmap(params[a], dft_array_full[a]);
@@ -583,6 +611,7 @@ namespace tut
 
         void addf(const std::string& n, const std::string& d, Vars* v)
         {
+            debug("addf('", n, "', '", d, "')");
             // This method is to capture in our own DescMap the name and
             // description of every registered function, for metadata query
             // testing.
@@ -598,19 +627,14 @@ namespace tut
         {
             // Copy descs to a temp map of same type.
             DescMap forgotten(descs.begin(), descs.end());
-            // LLEventDispatcher intentionally provides only const_iterator:
-            // since dereferencing that iterator generates values on the fly,
-            // it's meaningless to have a modifiable iterator. But since our
-            // 'work' object isn't const, by default BOOST_FOREACH() wants to
-            // use non-const iterators. Persuade it to use the const_iterator.
-            foreach(LLEventDispatcher::NameDesc nd, const_cast<const Dispatcher&>(work))
+            for (LLEventDispatcher::NameDesc nd: work)
             {
                 DescMap::iterator found = forgotten.find(nd.first);
-                ensure(STRINGIZE("LLEventDispatcher records function '" << nd.first
-                                 << "' we didn't enter"),
+                ensure(stringize("LLEventDispatcher records function '", nd.first,
+                                 "' we didn't enter"),
                        found != forgotten.end());
-                ensure_equals(STRINGIZE("LLEventDispatcher desc '" << nd.second <<
-                                        "' doesn't match what we entered: '" << found->second << "'"),
+                ensure_equals(stringize("LLEventDispatcher desc '", nd.second,
+                                        "' doesn't match what we entered: '", found->second, "'"),
                               nd.second, found->second);
                 // found in our map the name from LLEventDispatcher, good, erase
                 // our map entry
@@ -621,41 +645,49 @@ namespace tut
                 std::ostringstream out;
                 out << "LLEventDispatcher failed to report";
                 const char* delim = ": ";
-                foreach(const DescMap::value_type& fme, forgotten)
+                for (const DescMap::value_type& fme: forgotten)
                 {
                     out << delim << fme.first;
                     delim = ", ";
                 }
-                ensure(out.str(), false);
+                throw failure(out.str());
             }
         }
 
         Vars* varsfor(const std::string& name)
         {
             VarsMap::const_iterator found = funcvars.find(name);
-            ensure(STRINGIZE("No Vars* for " << name), found != funcvars.end());
-            ensure(STRINGIZE("NULL Vars* for " << name), found->second);
+            ensure(stringize("No Vars* for ", name), found != funcvars.end());
+            ensure(stringize("NULL Vars* for ", name), found->second);
             return found->second;
         }
 
-        void ensure_has(const std::string& outer, const std::string& inner)
+        std::string call_exc(const std::string& func, const LLSD& args, const std::string& exc_frag)
         {
-            ensure(STRINGIZE("'" << outer << "' does not contain '" << inner << "'").c_str(),
-                   outer.find(inner) != std::string::npos);
+            return tut::call_exc(
+                [this, func, args]()
+                {
+                    if (func.empty())
+                    {
+                        work(args);
+                    }
+                    else
+                    {
+                        work(func, args);
+                    }
+                },
+                exc_frag);
         }
 
-        void call_exc(const std::string& func, const LLSD& args, const std::string& exc_frag)
+        void call_logerr(const std::string& func, const LLSD& args, const std::string& frag)
         {
-            std::string threw = catch_what<std::runtime_error>([this, &func, &args](){
-                    work(func, args);
-                });
-            ensure_has(threw, exc_frag);
+            tut::call_logerr([this, func, args](){ work(func, args); }, frag);
         }
 
         LLSD getMetadata(const std::string& name)
         {
             LLSD meta(work.getMetadata(name));
-            ensure(STRINGIZE("No metadata for " << name), meta.isDefined());
+            ensure(stringize("No metadata for ", name), meta.isDefined());
             return meta;
         }
 
@@ -724,7 +756,7 @@ namespace tut
         set_test_name("map-style registration with non-array params");
         // Pass "param names" as scalar or as map
         LLSD attempts(llsd::array(17, LLSDMap("pi", 3.14)("two", 2)));
-        foreach(LLSD ae, inArray(attempts))
+        for (LLSD ae: inArray(attempts))
         {
             std::string threw = catch_what<std::exception>([this, &ae](){
                     work.add("freena_err", "freena", freena, ae);
@@ -799,7 +831,7 @@ namespace tut
     {
         set_test_name("query Callables with/out required params");
         LLSD names(llsd::array("free1", "Dmethod1", "Dcmethod1", "method1"));
-        foreach(LLSD nm, inArray(names))
+        for (LLSD nm: inArray(names))
         {
             LLSD metadata(getMetadata(nm));
             ensure_equals("name mismatch", metadata["name"], nm);
@@ -828,19 +860,19 @@ namespace tut
                        (5, llsd::array("freena_array", "smethodna_array", "methodna_array")),
                        llsd::array
                        (5, llsd::array("freenb_array", "smethodnb_array", "methodnb_array"))));
-        foreach(LLSD ae, inArray(expected))
+        for (LLSD ae: inArray(expected))
         {
             LLSD::Integer arity(ae[0].asInteger());
             LLSD names(ae[1]);
             LLSD req(LLSD::emptyArray());
             if (arity)
                 req[arity - 1] = LLSD();
-            foreach(LLSD nm, inArray(names))
+            for (LLSD nm: inArray(names))
             {
                 LLSD metadata(getMetadata(nm));
                 ensure_equals("name mismatch", metadata["name"], nm);
                 ensure_equals(metadata["desc"].asString(), descs[nm]);
-                ensure_equals(STRINGIZE("mismatched required for " << nm.asString()),
+                ensure_equals(stringize("mismatched required for ", nm.asString()),
                               metadata["required"], req);
                 ensure("should not have optional", metadata["optional"].isUndefined());
             }
@@ -854,7 +886,7 @@ namespace tut
         // - (Free function | non-static method), map style, no params (ergo
         //   no defaults)
         LLSD names(llsd::array("free0_map", "smethod0_map", "method0_map"));
-        foreach(LLSD nm, inArray(names))
+        for (LLSD nm: inArray(names))
         {
             LLSD metadata(getMetadata(nm));
             ensure_equals("name mismatch", metadata["name"], nm);
@@ -884,7 +916,7 @@ namespace tut
                            llsd::array("smethodnb_map_adft", "smethodnb_map_mdft"),
                            llsd::array("methodna_map_adft", "methodna_map_mdft"),
                            llsd::array("methodnb_map_adft", "methodnb_map_mdft")));
-        foreach(LLSD eq, inArray(equivalences))
+        for (LLSD eq: inArray(equivalences))
         {
             LLSD adft(eq[0]);
             LLSD mdft(eq[1]);
@@ -898,8 +930,8 @@ namespace tut
             ensure_equals("mdft name", mdft, mmeta["name"]);
             ameta.erase("name");
             mmeta.erase("name");
-            ensure_equals(STRINGIZE("metadata for " << adft.asString()
-                                    << " vs. " << mdft.asString()),
+            ensure_equals(stringize("metadata for ", adft.asString(),
+                                    " vs. ", mdft.asString()),
                           ameta, mmeta);
         }
     }
@@ -915,7 +947,7 @@ namespace tut
         // params are required. Also maps containing left requirements for
         // partial defaults arrays. Also defaults maps from defaults arrays.
         LLSD allreq, leftreq, rightdft;
-        foreach(LLSD::String a, ab)
+        for (LLSD::String a: ab)
         {
             // The map in which all params are required uses params[a] as
             // keys, with all isUndefined() as values. We can accomplish that
@@ -943,9 +975,9 @@ namespace tut
         // Generate maps containing parameter names not provided by the
         // dft_map_partial maps.
         LLSD skipreq(allreq);
-        foreach(LLSD::String a, ab)
+        for (LLSD::String a: ab)
         {
-            foreach(const MapEntry& me, inMap(dft_map_partial[a]))
+            for (const MapEntry& me: inMap(dft_map_partial[a]))
             {
                 skipreq[a].erase(me.first);
             }
@@ -990,7 +1022,7 @@ namespace tut
                      (llsd::array("freenb_map_mdft", "smethodnb_map_mdft", "methodnb_map_mdft"),
                       llsd::array(LLSD::emptyMap(), dft_map_full["b"])))); // required, optional
 
-        foreach(LLSD grp, inArray(groups))
+        for (LLSD grp: inArray(groups))
         {
             // Internal structure of each group in 'groups':
             LLSD names(grp[0]);
@@ -1003,14 +1035,14 @@ namespace tut
                   optional);
 
             // Loop through 'names'
-            foreach(LLSD nm, inArray(names))
+            for (LLSD nm: inArray(names))
             {
                 LLSD metadata(getMetadata(nm));
                 ensure_equals("name mismatch", metadata["name"], nm);
                 ensure_equals(nm.asString(), metadata["desc"].asString(), descs[nm]);
-                ensure_equals(STRINGIZE(nm << " required mismatch"),
+                ensure_equals(stringize(nm, " required mismatch"),
                               metadata["required"], required);
-                ensure_equals(STRINGIZE(nm << " optional mismatch"),
+                ensure_equals(stringize(nm, " optional mismatch"),
                               metadata["optional"], optional);
             }
         }
@@ -1031,13 +1063,7 @@ namespace tut
     {
         set_test_name("call with bad name");
         call_exc("freek", LLSD(), "not found");
-        // We don't have a comparable helper function for the one-arg
-        // operator() method, and it's not worth building one just for this
-        // case. Write it out.
-        std::string threw = catch_what<std::runtime_error>([this](){
-                work(LLSDMap("op", "freek"));
-            });
-        ensure_has(threw, "bad");
+        std::string threw = call_exc("", LLSDMap("op", "freek"), "bad");
         ensure_has(threw, "op");
         ensure_has(threw, "freek");
     }
@@ -1079,7 +1105,7 @@ namespace tut
         // LLSD value matching 'required' according to llsd_matches() rules.
         LLSD matching(LLSDMap("d", 3.14)("array", llsd::array("answer", true, answer)));
         // Okay, walk through 'tests'.
-        foreach(const CallablesTriple& tr, tests)
+        for (const CallablesTriple& tr: tests)
         {
             // Should be able to pass 'answer' to Callables registered
             // without 'required'.
@@ -1087,7 +1113,7 @@ namespace tut
             ensure_equals("answer mismatch", tr.llsd, answer);
             // Should NOT be able to pass 'answer' to Callables registered
             // with 'required'.
-            call_exc(tr.name_req, answer, "bad request");
+            call_logerr(tr.name_req, answer, "bad request");
             // But SHOULD be able to pass 'matching' to Callables registered
             // with 'required'.
             work(tr.name_req, matching);
@@ -1101,17 +1127,20 @@ namespace tut
         set_test_name("passing wrong args to (map | array)-style registrations");
 
         // Pass scalar/map to array-style functions, scalar/array to map-style
-        // functions. As that validation happens well before we engage the
-        // argument magic, it seems pointless to repeat this with every
-        // variation: (free function | non-static method), (no | arbitrary)
-        // args. We should only need to engage it for one map-style
-        // registration and one array-style registration.
-        std::string array_exc("needs an args array");
-        call_exc("free0_array", 17, array_exc);
-        call_exc("free0_array", LLSDMap("pi", 3.14), array_exc);
+        // functions. It seems pointless to repeat this with every variation:
+        // (free function | non-static method), (no | arbitrary) args. We
+        // should only need to engage it for one map-style registration and
+        // one array-style registration.
+        // Now that LLEventDispatcher has been extended to treat an LLSD
+        // scalar as a single-entry array, the error we expect in this case is
+        // that apply() is trying to pass that non-empty array to a nullary
+        // function.
+        call_logerr("free0_array", 17, "LL::apply");
+        // similarly, apply() doesn't accept an LLSD Map
+        call_logerr("free0_array", LLSDMap("pi", 3.14), "unsupported");
 
         std::string map_exc("needs a map");
-        call_exc("free0_map", 17, map_exc);
+        call_logerr("free0_map", 17, map_exc);
         // Passing an array to a map-style function works now! No longer an
         // error case!
 //      call_exc("free0_map", llsd::array("a", "b"), map_exc);
@@ -1125,7 +1154,7 @@ namespace tut
                    ("free0_array", "free0_map",
                     "smethod0_array", "smethod0_map",
                     "method0_array", "method0_map"));
-        foreach(LLSD name, inArray(names))
+        for (LLSD name: inArray(names))
         {
             // Look up the Vars instance for this function.
             Vars* vars(varsfor(name));
@@ -1150,15 +1179,21 @@ namespace tut
     template<> template<>
     void object::test<19>()
     {
-        set_test_name("call array-style functions with too-short arrays");
-        // Could have two different too-short arrays, one for *na and one for
-        // *nb, but since they both take 5 params...
+        set_test_name("call array-style functions with wrong-length arrays");
+        // Could have different wrong-length arrays for *na and for *nb, but
+        // since they both take 5 params...
         LLSD tooshort(llsd::array("this", "array", "too", "short"));
-        foreach(const LLSD& funcsab, inArray(array_funcs))
+        LLSD toolong (llsd::array("this", "array", "is",  "one", "too", "long"));
+        LLSD badargs (llsd::array(tooshort, toolong));
+        for (const LLSD& toosomething: inArray(badargs))
         {
-            foreach(const llsd::MapEntry& e, inMap(funcsab))
+            for (const LLSD& funcsab: inArray(array_funcs))
             {
-                call_exc(e.second, tooshort, "requires more arguments");
+                for (const llsd::MapEntry& e: inMap(funcsab))
+                {
+                    // apply() complains about wrong number of array entries
+                    call_logerr(e.second, toosomething, "LL::apply");
+                }
             }
         }
     }
@@ -1166,7 +1201,7 @@ namespace tut
     template<> template<>
     void object::test<20>()
     {
-        set_test_name("call array-style functions with (just right | too long) arrays");
+        set_test_name("call array-style functions with right-size arrays");
         std::vector<U8> binary;
         for (size_t h(0x01), i(0); i < 5; h+= 0x22, ++i)
         {
@@ -1178,40 +1213,25 @@ namespace tut
                                            LLDate("2011-02-03T15:07:00Z"),
                                            LLURI("http://secondlife.com"),
                                            binary)));
-        LLSD argsplus(args);
-        argsplus["a"].append("bogus");
-        argsplus["b"].append("bogus");
         LLSD expect;
-        foreach(LLSD::String a, ab)
+        for (LLSD::String a: ab)
         {
             expect[a] = zipmap(params[a], args[a]);
         }
         // Adjust expect["a"]["cp"] for special Vars::cp treatment.
-        expect["a"]["cp"] = std::string("'") + expect["a"]["cp"].asString() + "'";
+        expect["a"]["cp"] = stringize("'", expect["a"]["cp"].asString(), "'");
         debug("expect: ", expect);
 
-        // Use substantially the same logic for args and argsplus
-        LLSD argsarrays(llsd::array(args, argsplus));
-        // So i==0 selects 'args', i==1 selects argsplus
-        for (LLSD::Integer i(0), iend(argsarrays.size()); i < iend; ++i)
+        for (const LLSD& funcsab: inArray(array_funcs))
         {
-            foreach(const LLSD& funcsab, inArray(array_funcs))
+            for (LLSD::String a: ab)
             {
-                foreach(LLSD::String a, ab)
-                {
-                    // Reset the Vars instance before each call
-                    Vars* vars(varsfor(funcsab[a]));
-                    *vars = Vars();
-                    work(funcsab[a], argsarrays[i][a]);
-                    ensure_llsd(STRINGIZE(funcsab[a].asString() <<
-                                          ": expect[\"" << a << "\"] mismatch"),
-                                vars->inspect(), expect[a], 7); // 7 bits ~= 2 decimal digits
-
-                    // TODO: in the i==1 or argsplus case, intercept LL_WARNS
-                    // output? Even without that, using argsplus verifies that
-                    // passing too many args isn't fatal; it works -- but
-                    // would be nice to notice the warning too.
-                }
+                // Reset the Vars instance before each call
+                Vars* vars(varsfor(funcsab[a]));
+                *vars = Vars();
+                work(funcsab[a], args[a]);
+                ensure_llsd(stringize(funcsab[a].asString(), ": expect[\"", a, "\"] mismatch"),
+                            vars->inspect(), expect[a], 7); // 7 bits ~= 2 decimal digits
             }
         }
     }
@@ -1239,7 +1259,7 @@ namespace tut
                         ("a", llsd::array(false, 255, 98.6, 1024.5, "pointer"))
                         ("b", llsd::array("object", LLUUID::generateNewID(), LLDate::now(), LLURI("http://wiki.lindenlab.com/wiki"), LLSD::Binary(boost::begin(binary), boost::end(binary)))));
         LLSD array_overfull(array_full);
-        foreach(LLSD::String a, ab)
+        for (LLSD::String a: ab)
         {
             array_overfull[a].append("bogus");
         }
@@ -1253,7 +1273,7 @@ namespace tut
         ensure_not_equals("UUID collision",
                           array_full["b"][1].asUUID(), dft_array_full["b"][1].asUUID());
         LLSD map_full, map_overfull;
-        foreach(LLSD::String a, ab)
+        for (LLSD::String a: ab)
         {
             map_full[a] = zipmap(params[a], array_full[a]);
             map_overfull[a] = map_full[a];
@@ -1294,21 +1314,360 @@ namespace tut
                      "freenb_map_mdft",    "smethodnb_map_mdft",    "methodnb_map_mdft")));
         // Treat (full | overfull) (array | map) the same.
         LLSD argssets(llsd::array(array_full, array_overfull, map_full, map_overfull));
-        foreach(const LLSD& args, inArray(argssets))
+        for (const LLSD& args: inArray(argssets))
         {
-            foreach(LLSD::String a, ab)
+            for (LLSD::String a: ab)
             {
-                foreach(LLSD::String name, inArray(names[a]))
+                for (LLSD::String name: inArray(names[a]))
                 {
                     // Reset the Vars instance
                     Vars* vars(varsfor(name));
                     *vars = Vars();
                     work(name, args[a]);
-                    ensure_llsd(STRINGIZE(name << ": expect[\"" << a << "\"] mismatch"),
+                    ensure_llsd(stringize(name, ": expect[\"", a, "\"] mismatch"),
                                 vars->inspect(), expect[a], 7); // 7 bits, 2 decimal digits
                     // intercept LL_WARNS for the two overfull cases?
                 }
             }
         }
     }
+
+    struct DispatchResult: public LLDispatchListener
+    {
+        using DR = DispatchResult;
+
+        DispatchResult(): LLDispatchListener("results", "op")
+        {
+            add("strfunc",   "return string",       &DR::strfunc);
+            add("voidfunc",  "void function",       &DR::voidfunc);
+            add("emptyfunc", "return empty LLSD",   &DR::emptyfunc);
+            add("intfunc",   "return Integer LLSD", &DR::intfunc);
+            add("llsdfunc",  "return passed LLSD",  &DR::llsdfunc);
+            add("mapfunc",   "return map LLSD",     &DR::mapfunc);
+            add("arrayfunc", "return array LLSD",   &DR::arrayfunc);
+        }
+
+        std::string strfunc(const std::string& str) const { return "got " + str; }
+        void voidfunc()                  const {}
+        LLSD emptyfunc()                 const { return {}; }
+        int  intfunc(int i)              const { return -i; }
+        LLSD llsdfunc(const LLSD& event) const
+        {
+            LLSD result{ event };
+            result["with"] = "string";
+            return result;
+        }
+        LLSD mapfunc(int i, const std::string& str) const
+        {
+            return llsd::map("i", intfunc(i), "str", strfunc(str));
+        }
+        LLSD arrayfunc(int i, const std::string& str) const
+        {
+            return llsd::array(intfunc(i), strfunc(str));
+        }
+    };
+
+    template<> template<>
+    void object::test<23>()
+    {
+        set_test_name("string result");
+        DispatchResult service;
+        LLSD result{ service("strfunc", "a string") };
+        ensure_equals("strfunc() mismatch", result.asString(), "got a string");
+    }
+
+    template<> template<>
+    void object::test<24>()
+    {
+        set_test_name("void result");
+        DispatchResult service;
+        LLSD result{ service("voidfunc", LLSD()) };
+        ensure("voidfunc() returned defined", result.isUndefined());
+    }
+
+    template<> template<>
+    void object::test<25>()
+    {
+        set_test_name("Integer result");
+        DispatchResult service;
+        LLSD result{ service("intfunc", -17) };
+        ensure_equals("intfunc() mismatch", result.asInteger(), 17);
+    }
+
+    template<> template<>
+    void object::test<26>()
+    {
+        set_test_name("LLSD echo");
+        DispatchResult service;
+        LLSD result{ service("llsdfunc", llsd::map("op", "llsdfunc", "reqid", 17)) };
+        ensure_equals("llsdfunc() mismatch", result,
+                      llsd::map("op", "llsdfunc", "reqid", 17, "with", "string"));
+    }
+
+    template<> template<>
+    void object::test<27>()
+    {
+        set_test_name("map LLSD result");
+        DispatchResult service;
+        LLSD result{ service("mapfunc", llsd::array(-12, "value")) };
+        ensure_equals("mapfunc() mismatch", result, llsd::map("i", 12, "str", "got value"));
+    }
+
+    template<> template<>
+    void object::test<28>()
+    {
+        set_test_name("array LLSD result");
+        DispatchResult service;
+        LLSD result{ service("arrayfunc", llsd::array(-8, "word")) };
+        ensure_equals("arrayfunc() mismatch", result, llsd::array(8, "got word"));
+    }
+
+    template<> template<>
+    void object::test<29>()
+    {
+        set_test_name("listener error, no reply");
+        DispatchResult service;
+        tut::call_exc(
+            [&service]()
+            { service.post(llsd::map("op", "nosuchfunc", "reqid", 17)); },
+            "nosuchfunc");
+    }
+
+    template<> template<>
+    void object::test<30>()
+    {
+        set_test_name("listener error with reply");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map("op", "nosuchfunc", "reqid", 17, "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure("no reply", reply.isDefined());
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        ensure_has(reply["error"].asString(), "nosuchfunc");
+    }
+
+    template<> template<>
+    void object::test<31>()
+    {
+        set_test_name("listener call to void function");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        result.set("non-empty");
+        for (const auto& func: StringVec{ "voidfunc", "emptyfunc" })
+        {
+            service.post(llsd::map(
+                             "op", func,
+                             "reqid", 17,
+                             "reply", result.getName()));
+            ensure_equals("reply from " + func, result.get().asString(), "non-empty");
+        }
+    }
+
+    template<> template<>
+    void object::test<32>()
+    {
+        set_test_name("listener call to string function");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", "strfunc",
+                         "args", llsd::array("a string"),
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        ensure_equals("bad reply from strfunc", reply["data"].asString(), "got a string");
+    }
+
+    template<> template<>
+    void object::test<33>()
+    {
+        set_test_name("listener call to map function");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", "mapfunc",
+                         "args", llsd::array(-7, "value"),
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        ensure_equals("bad i from mapfunc", reply["i"].asInteger(), 7);
+        ensure_equals("bad str from mapfunc", reply["str"], "got value");
+    }
+
+    template<> template<>
+    void object::test<34>()
+    {
+        set_test_name("batched map success");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", llsd::map(
+                             "strfunc", "some string",
+                             "intfunc", 2,
+                             "voidfunc", LLSD(),
+                             "arrayfunc", llsd::array(-5, "other string")),
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        reply.erase("reqid");
+        ensure_equals(
+            "bad map batch",
+            reply,
+            llsd::map(
+                "strfunc", "got some string",
+                "intfunc", -2,
+                "voidfunc", LLSD(),
+                "arrayfunc", llsd::array(5, "got other string")));
+    }
+
+    template<> template<>
+    void object::test<35>()
+    {
+        set_test_name("batched map error");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", llsd::map(
+                             "badfunc", 34, // !
+                             "strfunc", "some string",
+                             "intfunc", 2,
+                             "missing", LLSD(), // !
+                             "voidfunc", LLSD(),
+                             "arrayfunc", llsd::array(-5, "other string")),
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        reply.erase("reqid");
+        auto error{ reply["error"].asString() };
+        reply.erase("error");
+        ensure_has(error, "badfunc");
+        ensure_has(error, "missing");
+        ensure_equals(
+            "bad partial batch",
+            reply,
+            llsd::map(
+                "strfunc", "got some string",
+                "intfunc", -2,
+                "voidfunc", LLSD(),
+                "arrayfunc", llsd::array(5, "got other string")));
+    }
+
+    template<> template<>
+    void object::test<36>()
+    {
+        set_test_name("batched map exception");
+        DispatchResult service;
+        auto error = tut::call_exc(
+            [&service]()
+            {
+                service.post(llsd::map(
+                                 "op", llsd::map(
+                                     "badfunc", 34, // !
+                                     "strfunc", "some string",
+                                     "intfunc", 2,
+                                     "missing", LLSD(), // !
+                                     "voidfunc", LLSD(),
+                                     "arrayfunc", llsd::array(-5, "other string")),
+                                 "reqid", 17));
+                // no "reply"
+            },
+            "badfunc");
+        ensure_has(error, "missing");
+    }
+
+    template<> template<>
+    void object::test<37>()
+    {
+        set_test_name("batched array success");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", llsd::array(
+                             llsd::array("strfunc", "some string"),
+                             llsd::array("intfunc", 2),
+                             "arrayfunc",
+                             "voidfunc"),
+                         "args", llsd::array(
+                             LLSD(),
+                             LLSD(),
+                             llsd::array(-5, "other string")),
+                         // args array deliberately short, since the default
+                         // [3] is undefined, which should work for voidfunc
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        reply.erase("reqid");
+        ensure_equals(
+            "bad array batch",
+            reply,
+            llsd::map(
+                "data", llsd::array(
+                    "got some string",
+                    -2,
+                    llsd::array(5, "got other string"),
+                    LLSD())));
+    }
+
+    template<> template<>
+    void object::test<38>()
+    {
+        set_test_name("batched array error");
+        DispatchResult service;
+        LLCaptureListener<LLSD> result;
+        service.post(llsd::map(
+                         "op", llsd::array(
+                             llsd::array("strfunc", "some string"),
+                             llsd::array("intfunc", 2, "whoops"), // bad form
+                             "arrayfunc",
+                             "voidfunc"),
+                         "args", llsd::array(
+                             LLSD(),
+                             LLSD(),
+                             llsd::array(-5, "other string")),
+                         // args array deliberately short, since the default
+                         // [3] is undefined, which should work for voidfunc
+                         "reqid", 17,
+                         "reply", result.getName()));
+        LLSD reply{ result.get() };
+        ensure_equals("reqid not echoed", reply["reqid"].asInteger(), 17);
+        reply.erase("reqid");
+        auto error{ reply["error"] };
+        reply.erase("error");
+        ensure_has(error, "[1]");
+        ensure_has(error, "unsupported");
+        ensure_equals("bad array batch", reply,
+                      llsd::map("data", llsd::array("got some string")));
+    }
+
+    template<> template<>
+    void object::test<39>()
+    {
+        set_test_name("batched array exception");
+        DispatchResult service;
+        auto error = tut::call_exc(
+            [&service]()
+            {
+                service.post(llsd::map(
+                                 "op", llsd::array(
+                                     llsd::array("strfunc", "some string"),
+                                     llsd::array("intfunc", 2, "whoops"), // bad form
+                                     "arrayfunc",
+                                     "voidfunc"),
+                                 "args", llsd::array(
+                                     LLSD(),
+                                     LLSD(),
+                                     llsd::array(-5, "other string")),
+                                 // args array deliberately short, since the default
+                                 // [3] is undefined, which should work for voidfunc
+                                 "reqid", 17));
+                // no "reply"
+            },
+            "[1]");
+        ensure_has(error, "unsupported");
+    }
 } // namespace tut
diff --git a/indra/llcommon/tests/workqueue_test.cpp b/indra/llcommon/tests/workqueue_test.cpp
index 7655a7aa1f..df16f4a46e 100644
--- a/indra/llcommon/tests/workqueue_test.cpp
+++ b/indra/llcommon/tests/workqueue_test.cpp
@@ -38,7 +38,7 @@ namespace tut
 {
     struct workqueue_data
     {
-        WorkQueue queue{"queue"};
+        WorkSchedule queue{"queue"};
     };
     typedef test_group<workqueue_data> workqueue_group;
     typedef workqueue_group::object object;
@@ -49,8 +49,8 @@ namespace tut
     {
         set_test_name("name");
         ensure_equals("didn't capture name", queue.getKey(), "queue");
-        ensure("not findable", WorkQueue::getInstance("queue") == queue.getWeak().lock());
-        WorkQueue q2;
+        ensure("not findable", WorkSchedule::getInstance("queue") == queue.getWeak().lock());
+        WorkSchedule q2;
         ensure("has no name", LLStringUtil::startsWith(q2.getKey(), "WorkQueue"));
     }
 
@@ -73,16 +73,16 @@ namespace tut
     {
         set_test_name("postEvery");
         // record of runs
-        using Shared = std::deque<WorkQueue::TimePoint>;
+        using Shared = std::deque<WorkSchedule::TimePoint>;
         // This is an example of how to share data between the originator of
-        // postEvery(work) and the work item itself, since usually a WorkQueue
+        // postEvery(work) and the work item itself, since usually a WorkSchedule
         // is used to dispatch work to a different thread. Neither of them
         // should call any of LLCond's wait methods: you don't want to stall
         // either the worker thread or the originating thread (conventionally
         // main). Use LLCond or a subclass even if all you want to do is
         // signal the work item that it can quit; consider LLOneShotCond.
         LLCond<Shared> data;
-        auto start = WorkQueue::TimePoint::clock::now();
+        auto start = WorkSchedule::TimePoint::clock::now();
         // 2s seems like a long time to wait, since it directly impacts the
         // duration of this test program. Unfortunately GitHub's Mac runners
         // are pretty wimpy, and we're getting spurious "too late" errors just
@@ -97,7 +97,7 @@ namespace tut
                 data.update_one(
                     [](Shared& data)
                     {
-                        data.push_back(WorkQueue::TimePoint::clock::now());
+                        data.push_back(WorkSchedule::TimePoint::clock::now());
                     });
                 // by the 3rd call, return false to stop
                 return (++count < 3);
@@ -106,7 +106,7 @@ namespace tut
         // postEvery() running, so run until we have exhausted the iterations
         // or we time out waiting
         for (auto finish = start + 10*interval;
-             WorkQueue::TimePoint::clock::now() < finish &&
+             WorkSchedule::TimePoint::clock::now() < finish &&
              data.get([](const Shared& data){ return data.size(); }) < 3; )
         {
             queue.runPending();
@@ -143,8 +143,8 @@ namespace tut
     void object::test<4>()
     {
         set_test_name("postTo");
-        WorkQueue main("main");
-        auto qptr = WorkQueue::getInstance("queue");
+        WorkSchedule main("main");
+        auto qptr = WorkSchedule::getInstance("queue");
         int result = 0;
         main.postTo(
             qptr,
@@ -175,8 +175,8 @@ namespace tut
     void object::test<5>()
     {
         set_test_name("postTo with void return");
-        WorkQueue main("main");
-        auto qptr = WorkQueue::getInstance("queue");
+        WorkSchedule main("main");
+        auto qptr = WorkSchedule::getInstance("queue");
         std::string observe;
         main.postTo(
             qptr,
@@ -198,7 +198,7 @@ namespace tut
         std::string stored;
         // Try to call waitForResult() on this thread's main coroutine. It
         // should throw because the main coroutine must service the queue.
-        auto what{ catch_what<WorkQueue::Error>(
+        auto what{ catch_what<WorkSchedule::Error>(
                 [this, &stored](){ stored = queue.waitForResult(
                         [](){ return "should throw"; }); }) };
         ensure("lambda should not have run", stored.empty());
diff --git a/indra/llcommon/tests/wrapllerrs.h b/indra/llcommon/tests/wrapllerrs.h
index 3779fb41bc..d657b329bb 100644
--- a/indra/llcommon/tests/wrapllerrs.h
+++ b/indra/llcommon/tests/wrapllerrs.h
@@ -226,6 +226,11 @@ public:
         return boost::dynamic_pointer_cast<CaptureLogRecorder>(mRecorder)->streamto(out);
     }
 
+    friend inline std::ostream& operator<<(std::ostream& out, const CaptureLog& self)
+    {
+        return self.streamto(out);
+    }
+
 private:
     LLError::FatalFunction mFatalFunction;
     LLError::SettingsStoragePtr mOldSettings;
diff --git a/indra/llcommon/threadpool.cpp b/indra/llcommon/threadpool.cpp
index d5adf11264..3a9a5a2062 100644
--- a/indra/llcommon/threadpool.cpp
+++ b/indra/llcommon/threadpool.cpp
@@ -17,18 +17,58 @@
 // std headers
 // external library headers
 // other Linden headers
+#include "commoncontrol.h"
 #include "llerror.h"
 #include "llevents.h"
+#include "llsd.h"
 #include "stringize.h"
 
-LL::ThreadPool::ThreadPool(const std::string& name, size_t threads, size_t capacity):
+#include <boost/fiber/algo/round_robin.hpp>
+
+/*****************************************************************************
+*   Custom fiber scheduler for worker threads
+*****************************************************************************/
+// As of 2022-12-06, each of our worker threads only runs a single (default)
+// fiber: we don't launch explicit fibers within worker threads, nor do we
+// anticipate doing so. So a worker thread that's simply waiting for incoming
+// tasks should really sleep a little. Override the default fiber scheduler to
+// implement that.
+struct sleepy_robin: public boost::fibers::algo::round_robin
+{
+    virtual void suspend_until( std::chrono::steady_clock::time_point const&) noexcept
+    {
+#if LL_WINDOWS
+        // round_robin holds a std::condition_variable, and
+        // round_robin::suspend_until() calls
+        // std::condition_variable::wait_until(). On Windows, that call seems
+        // busier than it ought to be. Try just sleeping.
+        Sleep(1);
+#else
+        // currently unused other than windows, but might as well have something here
+        // different units than Sleep(), but we actually just want to sleep for any de-minimis duration
+        usleep(1);
+#endif
+    }
+
+    virtual void notify() noexcept
+    {
+        // Since our Sleep() call above will wake up on its own, we need not
+        // take any special action to wake it.
+    }
+};
+
+/*****************************************************************************
+*   ThreadPoolBase
+*****************************************************************************/
+LL::ThreadPoolBase::ThreadPoolBase(const std::string& name, size_t threads,
+                                   WorkQueueBase* queue):
     super(name),
-    mQueue(name, capacity),
     mName("ThreadPool:" + name),
-    mThreadCount(threads)
+    mThreadCount(getConfiguredWidth(name, threads)),
+    mQueue(queue)
 {}
 
-void LL::ThreadPool::start()
+void LL::ThreadPoolBase::start()
 {
     for (size_t i = 0; i < mThreadCount; ++i)
     {
@@ -56,17 +96,17 @@ void LL::ThreadPool::start()
         });
 }
 
-LL::ThreadPool::~ThreadPool()
+LL::ThreadPoolBase::~ThreadPoolBase()
 {
     close();
 }
 
-void LL::ThreadPool::close()
+void LL::ThreadPoolBase::close()
 {
-    if (! mQueue.isClosed())
+    if (! mQueue->isClosed())
     {
         LL_DEBUGS("ThreadPool") << mName << " closing queue and joining threads" << LL_ENDL;
-        mQueue.close();
+        mQueue->close();
         for (auto& pair: mThreads)
         {
             LL_DEBUGS("ThreadPool") << mName << " waiting on thread " << pair.first << LL_ENDL;
@@ -76,14 +116,74 @@ void LL::ThreadPool::close()
     }
 }
 
-void LL::ThreadPool::run(const std::string& name)
+void LL::ThreadPoolBase::run(const std::string& name)
 {
+#if LL_WINDOWS
+    // Try using sleepy_robin fiber scheduler.
+    boost::fibers::use_scheduling_algorithm<sleepy_robin>();
+#endif // LL_WINDOWS
+
     LL_DEBUGS("ThreadPool") << name << " starting" << LL_ENDL;
     run();
     LL_DEBUGS("ThreadPool") << name << " stopping" << LL_ENDL;
 }
 
-void LL::ThreadPool::run()
+void LL::ThreadPoolBase::run()
+{
+    mQueue->runUntilClose();
+}
+
+//static
+size_t LL::ThreadPoolBase::getConfiguredWidth(const std::string& name, size_t dft)
+{
+    LLSD poolSizes;
+    try
+    {
+        poolSizes = LL::CommonControl::get("Global", "ThreadPoolSizes");
+        // "ThreadPoolSizes" is actually a map containing the sizes of
+        // interest -- or should be, if this process has an
+        // LLViewerControlListener instance and its settings include
+        // "ThreadPoolSizes". If we failed to retrieve it, perhaps we're in a
+        // program that doesn't define that, or perhaps there's no such
+        // setting, or perhaps we're asking too early, before the LLEventAPI
+        // itself has been instantiated. In any of those cases, it seems worth
+        // warning.
+        if (! poolSizes.isDefined())
+        {
+            // Note: we don't warn about absence of an override key for a
+            // particular ThreadPool name, that's fine. This warning is about
+            // complete absence of a ThreadPoolSizes setting, which we expect
+            // in a normal viewer session.
+            LL_WARNS("ThreadPool") << "No 'ThreadPoolSizes' setting for ThreadPool '"
+                                   << name << "'" << LL_ENDL;
+        }
+    }
+    catch (const LL::CommonControl::Error& exc)
+    {
+        // We don't want ThreadPool to *require* LLViewerControlListener.
+        // Just log it and carry on.
+        LL_WARNS("ThreadPool") << "Can't check 'ThreadPoolSizes': " << exc.what() << LL_ENDL;
+    }
+
+    LL_DEBUGS("ThreadPool") << "ThreadPoolSizes = " << poolSizes << LL_ENDL;
+    // LLSD treats an undefined value as an empty map when asked to retrieve a
+    // key, so we don't need this to be conditional.
+    LLSD sizeSpec{ poolSizes[name] };
+    // We retrieve sizeSpec as LLSD, rather than immediately as LLSD::Integer,
+    // so we can distinguish the case when it's undefined.
+    return sizeSpec.isInteger() ? sizeSpec.asInteger() : dft;
+}
+
+//static
+size_t LL::ThreadPoolBase::getWidth(const std::string& name, size_t dft)
 {
-    mQueue.runUntilClose();
+    auto instance{ getInstance(name) };
+    if (instance)
+    {
+        return instance->getWidth();
+    }
+    else
+    {
+        return getConfiguredWidth(name, dft);
+    }
 }
diff --git a/indra/llcommon/threadpool.h b/indra/llcommon/threadpool.h
index f8eec3b457..60f4a0ce1b 100644
--- a/indra/llcommon/threadpool.h
+++ b/indra/llcommon/threadpool.h
@@ -13,7 +13,9 @@
 #if ! defined(LL_THREADPOOL_H)
 #define LL_THREADPOOL_H
 
+#include "threadpool_fwd.h"
 #include "workqueue.h"
+#include <memory>                   // std::unique_ptr
 #include <string>
 #include <thread>
 #include <utility>                  // std::pair
@@ -22,17 +24,24 @@
 namespace LL
 {
 
-    class ThreadPool: public LLInstanceTracker<ThreadPool, std::string>
+    class ThreadPoolBase: public LLInstanceTracker<ThreadPoolBase, std::string>
     {
     private:
-        using super = LLInstanceTracker<ThreadPool, std::string>;
+        using super = LLInstanceTracker<ThreadPoolBase, std::string>;
+
     public:
         /**
-         * Pass ThreadPool a string name. This can be used to look up the
+         * Pass ThreadPoolBase a string name. This can be used to look up the
          * relevant WorkQueue.
+         *
+         * The number of threads you pass sets the compile-time default. But
+         * if the user has overridden the LLSD map in the "ThreadPoolSizes"
+         * setting with a key matching this ThreadPool name, that setting
+         * overrides this parameter.
          */
-        ThreadPool(const std::string& name, size_t threads=1, size_t capacity=1024);
-        virtual ~ThreadPool();
+        ThreadPoolBase(const std::string& name, size_t threads,
+                       WorkQueueBase* queue);
+        virtual ~ThreadPoolBase();
 
         /**
          * Launch the ThreadPool. Until this call, a constructed ThreadPool
@@ -50,8 +59,6 @@ namespace LL
 
         std::string getName() const { return mName; }
         size_t getWidth() const { return mThreads.size(); }
-        /// obtain a non-const reference to the WorkQueue to post work to it
-        WorkQueue& getQueue() { return mQueue; }
 
         /**
          * Override run() if you need special processing. The default run()
@@ -59,15 +66,72 @@ namespace LL
          */
         virtual void run();
 
+        /**
+         * getConfiguredWidth() returns the setting, if any, for the specified
+         * ThreadPool name. Returns dft if the "ThreadPoolSizes" map does not
+         * contain the specified name.
+         */
+        static
+        size_t getConfiguredWidth(const std::string& name, size_t dft=0);
+
+        /**
+         * This getWidth() returns the width of the instantiated ThreadPool
+         * with the specified name, if any. If no instance exists, returns its
+         * getConfiguredWidth() if any. If there's no instance and no relevant
+         * override, return dft. Presumably dft should match the threads
+         * parameter passed to the ThreadPool constructor call that will
+         * eventually instantiate the ThreadPool with that name.
+         */
+        static
+        size_t getWidth(const std::string& name, size_t dft);
+
+    protected:
+        std::unique_ptr<WorkQueueBase> mQueue;
+
     private:
         void run(const std::string& name);
 
-        WorkQueue mQueue;
         std::string mName;
         size_t mThreadCount;
         std::vector<std::pair<std::string, std::thread>> mThreads;
     };
 
+    /**
+     * Specialize with WorkQueue or, for timestamped tasks, WorkSchedule
+     */
+    template <class QUEUE>
+    struct ThreadPoolUsing: public ThreadPoolBase
+    {
+        using queue_t = QUEUE;
+
+        /**
+         * Pass ThreadPoolUsing a string name. This can be used to look up the
+         * relevant WorkQueue.
+         *
+         * The number of threads you pass sets the compile-time default. But
+         * if the user has overridden the LLSD map in the "ThreadPoolSizes"
+         * setting with a key matching this ThreadPool name, that setting
+         * overrides this parameter.
+         *
+         * Pass an explicit capacity to limit the size of the queue.
+         * Constraining the queue can cause a submitter to block. Do not
+         * constrain any ThreadPool accepting work from the main thread.
+         */
+        ThreadPoolUsing(const std::string& name, size_t threads=1, size_t capacity=1024*1024):
+            ThreadPoolBase(name, threads, new queue_t(name, capacity))
+        {}
+        ~ThreadPoolUsing() override {}
+
+        /**
+         * obtain a non-const reference to the specific WorkQueue subclass to
+         * post work to it
+         */
+        queue_t& getQueue() { return static_cast<queue_t&>(*mQueue); }
+    };
+
+    /// ThreadPool is shorthand for using the simpler WorkQueue
+    using ThreadPool = ThreadPoolUsing<WorkQueue>;
+
 } // namespace LL
 
 #endif /* ! defined(LL_THREADPOOL_H) */
diff --git a/indra/llcommon/threadpool_fwd.h b/indra/llcommon/threadpool_fwd.h
new file mode 100644
index 0000000000..1aa3c4a0e2
--- /dev/null
+++ b/indra/llcommon/threadpool_fwd.h
@@ -0,0 +1,25 @@
+/**
+ * @file   threadpool_fwd.h
+ * @author Nat Goodspeed
+ * @date   2022-12-09
+ * @brief  Forward declarations for ThreadPool et al.
+ * 
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Copyright (c) 2022, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_THREADPOOL_FWD_H)
+#define LL_THREADPOOL_FWD_H
+
+#include "workqueue.h"
+
+namespace LL
+{
+    template <class QUEUE>
+    struct ThreadPoolUsing;
+
+    using ThreadPool = ThreadPoolUsing<WorkQueue>;
+} // namespace LL
+
+#endif /* ! defined(LL_THREADPOOL_FWD_H) */
diff --git a/indra/llcommon/workqueue.cpp b/indra/llcommon/workqueue.cpp
index eb06890468..cf80ce0656 100644
--- a/indra/llcommon/workqueue.cpp
+++ b/indra/llcommon/workqueue.cpp
@@ -26,83 +26,65 @@
 using Mutex = LLCoros::Mutex;
 using Lock  = LLCoros::LockType;
 
-LL::WorkQueue::WorkQueue(const std::string& name, size_t capacity):
-    super(makeName(name)),
-    mQueue(capacity)
+/*****************************************************************************
+*   WorkQueueBase
+*****************************************************************************/
+LL::WorkQueueBase::WorkQueueBase(const std::string& name):
+    super(makeName(name))
 {
     // TODO: register for "LLApp" events so we can implicitly close() on
     // viewer shutdown.
 }
 
-void LL::WorkQueue::close()
-{
-    mQueue.close();
-}
-
-size_t LL::WorkQueue::size()
-{
-    return mQueue.size();
-}
-
-bool LL::WorkQueue::isClosed()
-{
-    return mQueue.isClosed();
-}
-
-bool LL::WorkQueue::done()
-{
-    return mQueue.done();
-}
-
-void LL::WorkQueue::runUntilClose()
+void LL::WorkQueueBase::runUntilClose()
 {
     try
     {
         for (;;)
         {
             LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
-            callWork(mQueue.pop());
+            callWork(pop_());
         }
     }
-    catch (const Queue::Closed&)
+    catch (const Closed&)
     {
     }
 }
 
-bool LL::WorkQueue::runPending()
+bool LL::WorkQueueBase::runPending()
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
-    for (Work work; mQueue.tryPop(work); )
+    for (Work work; tryPop_(work); )
     {
         callWork(work);
     }
-    return ! mQueue.done();
+    return ! done();
 }
 
-bool LL::WorkQueue::runOne()
+bool LL::WorkQueueBase::runOne()
 {
     Work work;
-    if (mQueue.tryPop(work))
+    if (tryPop_(work))
     {
         callWork(work);
     }
-    return ! mQueue.done();
+    return ! done();
 }
 
-bool LL::WorkQueue::runUntil(const TimePoint& until)
+bool LL::WorkQueueBase::runUntil(const TimePoint& until)
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
     // Should we subtract some slop to allow for typical Work execution time?
     // How much slop?
     // runUntil() is simply a time-bounded runPending().
-    for (Work work; TimePoint::clock::now() < until && mQueue.tryPop(work); )
+    for (Work work; TimePoint::clock::now() < until && tryPop_(work); )
     {
         callWork(work);
     }
-    return ! mQueue.done();
+    return ! done();
 }
 
-std::string LL::WorkQueue::makeName(const std::string& name)
+std::string LL::WorkQueueBase::makeName(const std::string& name)
 {
     if (! name.empty())
         return name;
@@ -120,14 +102,7 @@ std::string LL::WorkQueue::makeName(const std::string& name)
     return STRINGIZE("WorkQueue" << num);
 }
 
-void LL::WorkQueue::callWork(const Queue::DataTuple& work)
-{
-    // ThreadSafeSchedule::pop() always delivers a tuple, even when
-    // there's only one data field per item, as for us.
-    callWork(std::get<0>(work));
-}
-
-void LL::WorkQueue::callWork(const Work& work)
+void LL::WorkQueueBase::callWork(const Work& work)
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD;
     try
@@ -142,12 +117,12 @@ void LL::WorkQueue::callWork(const Work& work)
     }
 }
 
-void LL::WorkQueue::error(const std::string& msg)
+void LL::WorkQueueBase::error(const std::string& msg)
 {
     LL_ERRS("WorkQueue") << msg << LL_ENDL;
 }
 
-void LL::WorkQueue::checkCoroutine(const std::string& method)
+void LL::WorkQueueBase::checkCoroutine(const std::string& method)
 {
     // By convention, the default coroutine on each thread has an empty name
     // string. See also LLCoros::logname().
@@ -156,3 +131,115 @@ void LL::WorkQueue::checkCoroutine(const std::string& method)
         LLTHROW(Error("Do not call " + method + " from a thread's default coroutine"));
     }
 }
+
+/*****************************************************************************
+*   WorkQueue
+*****************************************************************************/
+LL::WorkQueue::WorkQueue(const std::string& name, size_t capacity):
+    super(name),
+    mQueue(capacity)
+{
+}
+
+void LL::WorkQueue::close()
+{
+    mQueue.close();
+}
+
+size_t LL::WorkQueue::size()
+{
+    return mQueue.size();
+}
+
+bool LL::WorkQueue::isClosed()
+{
+    return mQueue.isClosed();
+}
+
+bool LL::WorkQueue::done()
+{
+    return mQueue.done();
+}
+
+bool LL::WorkQueue::post(const Work& callable)
+{
+    return mQueue.pushIfOpen(callable);
+}
+
+bool LL::WorkQueue::tryPost(const Work& callable)
+{
+    return mQueue.tryPush(callable);
+}
+
+LL::WorkQueue::Work LL::WorkQueue::pop_()
+{
+    return mQueue.pop();
+}
+
+bool LL::WorkQueue::tryPop_(Work& work)
+{
+    return mQueue.tryPop(work);
+}
+
+/*****************************************************************************
+*   WorkSchedule
+*****************************************************************************/
+LL::WorkSchedule::WorkSchedule(const std::string& name, size_t capacity):
+    super(name),
+    mQueue(capacity)
+{
+}
+
+void LL::WorkSchedule::close()
+{
+    mQueue.close();
+}
+
+size_t LL::WorkSchedule::size()
+{
+    return mQueue.size();
+}
+
+bool LL::WorkSchedule::isClosed()
+{
+    return mQueue.isClosed();
+}
+
+bool LL::WorkSchedule::done()
+{
+    return mQueue.done();
+}
+
+bool LL::WorkSchedule::post(const Work& callable)
+{
+    // Use TimePoint::clock::now() instead of TimePoint's representation of
+    // the epoch because this WorkSchedule may contain a mix of past-due
+    // TimedWork items and TimedWork items scheduled for the future. Sift this
+    // new item into the correct place.
+    return post(callable, TimePoint::clock::now());
+}
+
+bool LL::WorkSchedule::post(const Work& callable, const TimePoint& time)
+{
+    return mQueue.pushIfOpen(TimedWork(time, callable));
+}
+
+bool LL::WorkSchedule::tryPost(const Work& callable)
+{
+    return tryPost(callable, TimePoint::clock::now());
+}
+
+bool LL::WorkSchedule::tryPost(const Work& callable, const TimePoint& time)
+{
+    return mQueue.tryPush(TimedWork(time, callable));
+}
+
+LL::WorkSchedule::Work LL::WorkSchedule::pop_()
+{
+    return std::get<0>(mQueue.pop());
+}
+
+bool LL::WorkSchedule::tryPop_(Work& work)
+{
+    return mQueue.tryPop(work);
+}
diff --git a/indra/llcommon/workqueue.h b/indra/llcommon/workqueue.h
index 70fd65bd0c..ec0700a718 100644
--- a/indra/llcommon/workqueue.h
+++ b/indra/llcommon/workqueue.h
@@ -15,6 +15,7 @@
 #include "llcoros.h"
 #include "llexception.h"
 #include "llinstancetracker.h"
+#include "llinstancetrackersubclass.h"
 #include "threadsafeschedule.h"
 #include <chrono>
 #include <exception>                // std::current_exception
@@ -23,27 +24,23 @@
 
 namespace LL
 {
+
+/*****************************************************************************
+*   WorkQueueBase: API for WorkQueue and WorkSchedule
+*****************************************************************************/
     /**
      * A typical WorkQueue has a string name that can be used to find it.
      */
-    class WorkQueue: public LLInstanceTracker<WorkQueue, std::string>
+    class WorkQueueBase: public LLInstanceTracker<WorkQueueBase, std::string>
     {
     private:
-        using super = LLInstanceTracker<WorkQueue, std::string>;
+        using super = LLInstanceTracker<WorkQueueBase, std::string>;
 
     public:
         using Work = std::function<void()>;
-
-    private:
-        using Queue = ThreadSafeSchedule<Work>;
-        // helper for postEvery()
-        template <typename Rep, typename Period, typename CALLABLE>
-        class BackJack;
-
-    public:
-        using TimePoint = Queue::TimePoint;
-        using TimedWork = Queue::TimeTuple;
-        using Closed    = Queue::Closed;
+        using Closed = LLThreadSafeQueueInterrupt;
+        // for runFor()
+        using TimePoint = std::chrono::steady_clock::time_point;
 
         struct Error: public LLException
         {
@@ -51,18 +48,18 @@ namespace LL
         };
 
         /**
-         * You may omit the WorkQueue name, in which case a unique name is
+         * You may omit the WorkQueueBase name, in which case a unique name is
          * synthesized; for practical purposes that makes it anonymous.
          */
-        WorkQueue(const std::string& name = std::string(), size_t capacity=1024);
+        WorkQueueBase(const std::string& name);
 
         /**
          * Since the point of WorkQueue is to pass work to some other worker
-         * thread(s) asynchronously, it's important that the WorkQueue continue
-         * to exist until the worker thread(s) have drained it. To communicate
-         * that it's time for them to quit, close() the queue.
+         * thread(s) asynchronously, it's important that it continue to exist
+         * until the worker thread(s) have drained it. To communicate that
+         * it's time for them to quit, close() the queue.
          */
-        void close();
+        virtual void close() = 0;
 
         /**
          * WorkQueue supports multiple producers and multiple consumers. In
@@ -78,152 +75,57 @@ namespace LL
          * * If you're the only consumer, noticing that size() > 0 is
          *   meaningful.
          */
-        size_t size();
+        virtual size_t size() = 0;
         /// producer end: are we prevented from pushing any additional items?
-        bool isClosed();
+        virtual bool isClosed() = 0;
         /// consumer end: are we done, is the queue entirely drained?
-        bool done();
+        virtual bool done() = 0;
 
         /*---------------------- fire and forget API -----------------------*/
 
-        /// fire-and-forget, but at a particular (future?) time
-        template <typename CALLABLE>
-        void post(const TimePoint& time, CALLABLE&& callable)
-        {
-            // Defer reifying an arbitrary CALLABLE until we hit this or
-            // postIfOpen(). All other methods should accept CALLABLEs of
-            // arbitrary type to avoid multiple levels of std::function
-            // indirection.
-            mQueue.push(TimedWork(time, std::move(callable)));
-        }
-
-        /// fire-and-forget
-        template <typename CALLABLE>
-        void post(CALLABLE&& callable)
-        {
-            // We use TimePoint::clock::now() instead of TimePoint's
-            // representation of the epoch because this WorkQueue may contain
-            // a mix of past-due TimedWork items and TimedWork items scheduled
-            // for the future. Sift this new item into the correct place.
-            post(TimePoint::clock::now(), std::move(callable));
-        }
-
-        /**
-         * post work for a particular time, unless the queue is closed before
-         * we can post
-         */
-        template <typename CALLABLE>
-        bool postIfOpen(const TimePoint& time, CALLABLE&& callable)
-        {
-            // Defer reifying an arbitrary CALLABLE until we hit this or
-            // post(). All other methods should accept CALLABLEs of arbitrary
-            // type to avoid multiple levels of std::function indirection.
-            return mQueue.pushIfOpen(TimedWork(time, std::move(callable)));
-        }
-
         /**
          * post work, unless the queue is closed before we can post
          */
-        template <typename CALLABLE>
-        bool postIfOpen(CALLABLE&& callable)
-        {
-            return postIfOpen(TimePoint::clock::now(), std::move(callable));
-        }
+        virtual bool post(const Work&) = 0;
 
         /**
-         * Post work to be run at a specified time to another WorkQueue, which
-         * may or may not still exist and be open. Return true if we were able
-         * to post.
+         * post work, unless the queue is full
          */
-        template <typename CALLABLE>
-        static bool postMaybe(weak_t target, const TimePoint& time, CALLABLE&& callable);
+        virtual bool tryPost(const Work&) = 0;
 
         /**
          * Post work to another WorkQueue, which may or may not still exist
-         * and be open. Return true if we were able to post.
-         */
-        template <typename CALLABLE>
-        static bool postMaybe(weak_t target, CALLABLE&& callable)
-        {
-            return postMaybe(target, TimePoint::clock::now(),
-                             std::forward<CALLABLE>(callable));
-        }
-
-        /**
-         * Launch a callable returning bool that will trigger repeatedly at
-         * specified interval, until the callable returns false.
-         *
-         * If you need to signal that callable from outside, DO NOT bind a
-         * reference to a simple bool! That's not thread-safe. Instead, bind
-         * an LLCond variant, e.g. LLOneShotCond or LLBoolCond.
+         * and be open. Support any post() overload. Return true if we were
+         * able to post.
          */
-        template <typename Rep, typename Period, typename CALLABLE>
-        void postEvery(const std::chrono::duration<Rep, Period>& interval,
-                       CALLABLE&& callable);
-
-        template <typename CALLABLE>
-        bool tryPost(CALLABLE&& callable)
-        {
-            return mQueue.tryPush(TimedWork(TimePoint::clock::now(), std::move(callable)));
-        }
+        template <typename... ARGS>
+        static bool postMaybe(weak_t target, ARGS&&... args);
 
         /*------------------------- handshake API --------------------------*/
 
         /**
-         * Post work to another WorkQueue to be run at a specified time,
-         * requesting a specific callback to be run on this WorkQueue on
-         * completion.
-         *
-         * Returns true if able to post, false if the other WorkQueue is
-         * inaccessible.
-         */
-        // Apparently some Microsoft header file defines a macro CALLBACK? The
-        // natural template argument name CALLBACK produces very weird Visual
-        // Studio compile errors that seem utterly unrelated to this source
-        // code.
-        template <typename CALLABLE, typename FOLLOWUP>
-        bool postTo(weak_t target,
-                    const TimePoint& time, CALLABLE&& callable, FOLLOWUP&& callback);
-
-        /**
          * Post work to another WorkQueue, requesting a specific callback to
-         * be run on this WorkQueue on completion.
+         * be run on this WorkQueue on completion. Optional final argument is
+         * TimePoint for WorkSchedule.
          *
          * Returns true if able to post, false if the other WorkQueue is
          * inaccessible.
          */
-        template <typename CALLABLE, typename FOLLOWUP>
-        bool postTo(weak_t target, CALLABLE&& callable, FOLLOWUP&& callback)
-        {
-            return postTo(target, TimePoint::clock::now(),
-                          std::move(callable), std::move(callback));
-        }
-
-        /**
-         * Post work to another WorkQueue to be run at a specified time,
-         * blocking the calling coroutine until then, returning the result to
-         * caller on completion.
-         *
-         * In general, we assume that each thread's default coroutine is busy
-         * servicing its WorkQueue or whatever. To try to prevent mistakes, we
-         * forbid calling waitForResult() from a thread's default coroutine.
-         */
-        template <typename CALLABLE>
-        auto waitForResult(const TimePoint& time, CALLABLE&& callable);
+        template <typename CALLABLE, typename FOLLOWUP, typename... ARGS>
+        bool postTo(weak_t target, CALLABLE&& callable, FOLLOWUP&& callback,
+                    ARGS&&... args);
 
         /**
          * Post work to another WorkQueue, blocking the calling coroutine
-         * until then, returning the result to caller on completion.
+         * until then, returning the result to caller on completion. Optional
+         * final argument is TimePoint for WorkSchedule.
          *
          * In general, we assume that each thread's default coroutine is busy
          * servicing its WorkQueue or whatever. To try to prevent mistakes, we
          * forbid calling waitForResult() from a thread's default coroutine.
          */
-        template <typename CALLABLE>
-        auto waitForResult(CALLABLE&& callable)
-        {
-            return waitForResult(TimePoint::clock::now(), std::move(callable));
-        }
+        template <typename CALLABLE, typename... ARGS>
+        auto waitForResult(CALLABLE&& callable, ARGS&&... args);
 
         /*--------------------------- worker API ---------------------------*/
 
@@ -270,7 +172,7 @@ namespace LL
          */
         bool runUntil(const TimePoint& until);
 
-    private:
+    protected:
         template <typename CALLABLE, typename FOLLOWUP>
         static auto makeReplyLambda(CALLABLE&& callable, FOLLOWUP&& callback);
         /// general case: arbitrary C++ return type
@@ -290,13 +192,170 @@ namespace LL
         static void checkCoroutine(const std::string& method);
         static void error(const std::string& msg);
         static std::string makeName(const std::string& name);
-        void callWork(const Queue::DataTuple& work);
         void callWork(const Work& work);
+
+    private:
+        virtual Work pop_() = 0;
+        virtual bool tryPop_(Work&) = 0;
+    };
+
+/*****************************************************************************
+*   WorkQueue: no timestamped task support
+*****************************************************************************/
+    class WorkQueue: public LLInstanceTrackerSubclass<WorkQueue, WorkQueueBase>
+    {
+    private:
+        using super = LLInstanceTrackerSubclass<WorkQueue, WorkQueueBase>;
+
+    public:
+        /**
+         * You may omit the WorkQueue name, in which case a unique name is
+         * synthesized; for practical purposes that makes it anonymous.
+         */
+        WorkQueue(const std::string& name = std::string(), size_t capacity=1024);
+
+        /**
+         * Since the point of WorkQueue is to pass work to some other worker
+         * thread(s) asynchronously, it's important that it continue to exist
+         * until the worker thread(s) have drained it. To communicate that
+         * it's time for them to quit, close() the queue.
+         */
+        void close() override;
+
+        /**
+         * WorkQueue supports multiple producers and multiple consumers. In
+         * the general case it's misleading to test size(), since any other
+         * thread might change it the nanosecond the lock is released. On that
+         * basis, some might argue against publishing a size() method at all.
+         *
+         * But there are two specific cases in which a test based on size()
+         * might be reasonable:
+         *
+         * * If you're the only producer, noticing that size() == 0 is
+         *   meaningful.
+         * * If you're the only consumer, noticing that size() > 0 is
+         *   meaningful.
+         */
+        size_t size() override;
+        /// producer end: are we prevented from pushing any additional items?
+        bool isClosed() override;
+        /// consumer end: are we done, is the queue entirely drained?
+        bool done() override;
+
+        /*---------------------- fire and forget API -----------------------*/
+
+        /**
+         * post work, unless the queue is closed before we can post
+         */
+        bool post(const Work&) override;
+
+        /**
+         * post work, unless the queue is full
+         */
+        bool tryPost(const Work&) override;
+
+    private:
+        using Queue = LLThreadSafeQueue<Work>;
+        Queue mQueue;
+
+        Work pop_() override;
+        bool tryPop_(Work&) override;
+    };
+
+/*****************************************************************************
+*   WorkSchedule: add support for timestamped tasks
+*****************************************************************************/
+    class WorkSchedule: public LLInstanceTrackerSubclass<WorkSchedule, WorkQueueBase>
+    {
+    private:
+        using super = LLInstanceTrackerSubclass<WorkSchedule, WorkQueueBase>;
+        using Queue = ThreadSafeSchedule<Work>;
+        // helper for postEvery()
+        template <typename Rep, typename Period, typename CALLABLE>
+        class BackJack;
+
+    public:
+        using TimePoint = Queue::TimePoint;
+        using TimedWork = Queue::TimeTuple;
+
+        /**
+         * You may omit the WorkSchedule name, in which case a unique name is
+         * synthesized; for practical purposes that makes it anonymous.
+         */
+        WorkSchedule(const std::string& name = std::string(), size_t capacity=1024);
+
+        /**
+         * Since the point of WorkSchedule is to pass work to some other worker
+         * thread(s) asynchronously, it's important that the WorkSchedule continue
+         * to exist until the worker thread(s) have drained it. To communicate
+         * that it's time for them to quit, close() the queue.
+         */
+        void close() override;
+
+        /**
+         * WorkSchedule supports multiple producers and multiple consumers. In
+         * the general case it's misleading to test size(), since any other
+         * thread might change it the nanosecond the lock is released. On that
+         * basis, some might argue against publishing a size() method at all.
+         *
+         * But there are two specific cases in which a test based on size()
+         * might be reasonable:
+         *
+         * * If you're the only producer, noticing that size() == 0 is
+         *   meaningful.
+         * * If you're the only consumer, noticing that size() > 0 is
+         *   meaningful.
+         */
+        size_t size() override;
+        /// producer end: are we prevented from pushing any additional items?
+        bool isClosed() override;
+        /// consumer end: are we done, is the queue entirely drained?
+        bool done() override;
+
+        /*---------------------- fire and forget API -----------------------*/
+
+        /**
+         * post work, unless the queue is closed before we can post
+         */
+        bool post(const Work& callable) override;
+
+        /**
+         * post work for a particular time, unless the queue is closed before
+         * we can post
+         */
+        bool post(const Work& callable, const TimePoint& time);
+
+        /**
+         * post work, unless the queue is full
+         */
+        bool tryPost(const Work& callable) override;
+
+        /**
+         * post work for a particular time, unless the queue is full
+         */
+        bool tryPost(const Work& callable, const TimePoint& time);
+
+        /**
+         * Launch a callable returning bool that will trigger repeatedly at
+         * specified interval, until the callable returns false.
+         *
+         * If you need to signal that callable from outside, DO NOT bind a
+         * reference to a simple bool! That's not thread-safe. Instead, bind
+         * an LLCond variant, e.g. LLOneShotCond or LLBoolCond.
+         */
+        template <typename Rep, typename Period, typename CALLABLE>
+        bool postEvery(const std::chrono::duration<Rep, Period>& interval,
+                       CALLABLE&& callable);
+
+    private:
         Queue mQueue;
+
+        Work pop_() override;
+        bool tryPop_(Work&) override;
     };
 
     /**
-     * BackJack is, in effect, a hand-rolled lambda, binding a WorkQueue, a
+     * BackJack is, in effect, a hand-rolled lambda, binding a WorkSchedule, a
      * CALLABLE that returns bool, a TimePoint and an interval at which to
      * relaunch it. As long as the callable continues returning true, BackJack
      * keeps resubmitting it to the target WorkQueue.
@@ -305,7 +364,7 @@ namespace LL
     // class method gets its own 'this' pointer -- which we need to resubmit
     // the whole BackJack callable.
     template <typename Rep, typename Period, typename CALLABLE>
-    class WorkQueue::BackJack
+    class WorkSchedule::BackJack
     {
     public:
         // bind the desired data
@@ -319,9 +378,10 @@ namespace LL
             mCallable(std::move(callable))
         {}
 
-        // Call by target WorkQueue -- note that although WE require a
-        // callable returning bool, WorkQueue wants a void callable. We
-        // consume the bool.
+        // This operator() method, called by target WorkSchedule, is what
+        // makes this object a Work item. Although WE require a callable
+        // returning bool, WorkSchedule wants a void callable. We consume the
+        // bool.
         void operator()()
         {
             // If mCallable() throws an exception, don't catch it here: if it
@@ -337,7 +397,7 @@ namespace LL
                 // register our intent to fire at exact mIntervals.
                 mStart += mInterval;
 
-                // We're being called at this moment by the target WorkQueue.
+                // We're being called at this moment by the target WorkSchedule.
                 // Assume it still exists, rather than checking the result of
                 // lock().
                 // Resubmit the whole *this callable: that's why we're a class
@@ -345,14 +405,10 @@ namespace LL
                 // move-only callable; but naturally this statement must be
                 // the last time we reference this instance, which may become
                 // moved-from.
-                try
-                {
-                    mTarget.lock()->post(mStart, std::move(*this));
-                }
-                catch (const Closed&)
-                {
-                    // Once this queue is closed, oh well, just stop
-                }
+                auto target{ std::dynamic_pointer_cast<WorkSchedule>(mTarget.lock()) };
+                // Discard bool return: once this queue is closed, oh well,
+                // just stop
+                target->post(std::move(*this), mStart);
             }
         }
 
@@ -364,8 +420,8 @@ namespace LL
     };
 
     template <typename Rep, typename Period, typename CALLABLE>
-    void WorkQueue::postEvery(const std::chrono::duration<Rep, Period>& interval,
-                              CALLABLE&& callable)
+    bool WorkSchedule::postEvery(const std::chrono::duration<Rep, Period>& interval,
+                                 CALLABLE&& callable)
     {
         if (interval.count() <= 0)
         {
@@ -381,14 +437,14 @@ namespace LL
         // Instantiate and post a suitable BackJack, binding a weak_ptr to
         // self, the current time, the desired interval and the desired
         // callable.
-        post(
+        return post(
             BackJack<Rep, Period, CALLABLE>(
                  getWeak(), TimePoint::clock::now(), interval, std::move(callable)));
     }
 
     /// general case: arbitrary C++ return type
     template <typename CALLABLE, typename FOLLOWUP, typename RETURNTYPE>
-    struct WorkQueue::MakeReplyLambda
+    struct WorkQueueBase::MakeReplyLambda
     {
         auto operator()(CALLABLE&& callable, FOLLOWUP&& callback)
         {
@@ -409,7 +465,7 @@ namespace LL
 
     /// specialize for CALLABLE returning void
     template <typename CALLABLE, typename FOLLOWUP>
-    struct WorkQueue::MakeReplyLambda<CALLABLE, FOLLOWUP, void>
+    struct WorkQueueBase::MakeReplyLambda<CALLABLE, FOLLOWUP, void>
     {
         auto operator()(CALLABLE&& callable, FOLLOWUP&& callback)
         {
@@ -421,16 +477,16 @@ namespace LL
     };
 
     template <typename CALLABLE, typename FOLLOWUP>
-    auto WorkQueue::makeReplyLambda(CALLABLE&& callable, FOLLOWUP&& callback)
+    auto WorkQueueBase::makeReplyLambda(CALLABLE&& callable, FOLLOWUP&& callback)
     {
         return MakeReplyLambda<CALLABLE, FOLLOWUP,
                                decltype(std::forward<CALLABLE>(callable)())>()
             (std::move(callable), std::move(callback));
     }
 
-    template <typename CALLABLE, typename FOLLOWUP>
-    bool WorkQueue::postTo(weak_t target,
-                           const TimePoint& time, CALLABLE&& callable, FOLLOWUP&& callback)
+    template <typename CALLABLE, typename FOLLOWUP, typename... ARGS>
+    bool WorkQueueBase::postTo(weak_t target, CALLABLE&& callable, FOLLOWUP&& callback,
+                               ARGS&&... args)
     {
         LL_PROFILE_ZONE_SCOPED;
         // We're being asked to post to the WorkQueue at target.
@@ -443,13 +499,12 @@ namespace LL
         // Here we believe target WorkQueue still exists. Post to it a
         // lambda that packages our callable, our callback and a weak_ptr
         // to this originating WorkQueue.
-        tptr->post(
-            time,
+        return tptr->post(
             [reply = super::getWeak(),
              callable = std::move(callable),
              callback = std::move(callback)]
-            ()
-            mutable {
+            () mutable
+            {
                 // Use postMaybe() below in case this originating WorkQueue
                 // has been closed or destroyed. Remember, the outer lambda is
                 // now running on a thread servicing the target WorkQueue, and
@@ -472,44 +527,34 @@ namespace LL
                         // originating WorkQueue. Once there, rethrow it.
                         [exc = std::current_exception()](){ std::rethrow_exception(exc); });
                 }
-            });
-
-        // looks like we were able to post()
-        return true;
+            },
+            // if caller passed a TimePoint, pass it along to post()
+            std::forward<ARGS>(args)...);
     }
 
-    template <typename CALLABLE>
-    bool WorkQueue::postMaybe(weak_t target, const TimePoint& time, CALLABLE&& callable)
+    template <typename... ARGS>
+    bool WorkQueueBase::postMaybe(weak_t target, ARGS&&... args)
     {
         LL_PROFILE_ZONE_SCOPED;
         // target is a weak_ptr: have to lock it to check it
         auto tptr = target.lock();
         if (tptr)
         {
-            try
-            {
-                tptr->post(time, std::forward<CALLABLE>(callable));
-                // we were able to post()
-                return true;
-            }
-            catch (const Closed&)
-            {
-                // target WorkQueue still exists, but is Closed
-            }
+            return tptr->post(std::forward<ARGS>(args)...);
         }
-        // either target no longer exists, or its WorkQueue is Closed
+        // target no longer exists
         return false;
     }
 
     /// general case: arbitrary C++ return type
     template <typename CALLABLE, typename RETURNTYPE>
-    struct WorkQueue::WaitForResult
+    struct WorkQueueBase::WaitForResult
     {
-        auto operator()(WorkQueue* self, const TimePoint& time, CALLABLE&& callable)
+        template <typename... ARGS>
+        auto operator()(WorkQueueBase* self, CALLABLE&& callable, ARGS&&... args)
         {
             LLCoros::Promise<RETURNTYPE> promise;
-            self->post(
-                time,
+            bool posted = self->post(
                 // We dare to bind a reference to Promise because it's
                 // specifically designed for cross-thread communication.
                 [&promise, callable = std::move(callable)]()
@@ -523,7 +568,13 @@ namespace LL
                     {
                         promise.set_exception(std::current_exception());
                     }
-                });
+                },
+                // if caller passed a TimePoint, pass it to post()
+                std::forward<ARGS>(args)...);
+            if (! posted)
+            {
+                LLTHROW(WorkQueueBase::Closed());
+            }
             auto future{ LLCoros::getFuture(promise) };
             // now, on the calling thread, wait for that result
             LLCoros::TempStatus st("waiting for WorkQueue::waitForResult()");
@@ -533,13 +584,13 @@ namespace LL
 
     /// specialize for CALLABLE returning void
     template <typename CALLABLE>
-    struct WorkQueue::WaitForResult<CALLABLE, void>
+    struct WorkQueueBase::WaitForResult<CALLABLE, void>
     {
-        void operator()(WorkQueue* self, const TimePoint& time, CALLABLE&& callable)
+        template <typename... ARGS>
+        void operator()(WorkQueueBase* self, CALLABLE&& callable, ARGS&&... args)
         {
             LLCoros::Promise<void> promise;
-            self->post(
-                time,
+            bool posted = self->post(
                 // &promise is designed for cross-thread access
                 [&promise, callable = std::move(callable)]()
                 mutable {
@@ -552,7 +603,13 @@ namespace LL
                     {
                         promise.set_exception(std::current_exception());
                     }
-                });
+                },
+                // if caller passed a TimePoint, pass it to post()
+                std::forward<ARGS>(args)...);
+            if (! posted)
+            {
+                LLTHROW(WorkQueueBase::Closed());
+            }
             auto future{ LLCoros::getFuture(promise) };
             // block until set_value()
             LLCoros::TempStatus st("waiting for void WorkQueue::waitForResult()");
@@ -560,13 +617,13 @@ namespace LL
         }
     };
 
-    template <typename CALLABLE>
-    auto WorkQueue::waitForResult(const TimePoint& time, CALLABLE&& callable)
+    template <typename CALLABLE, typename... ARGS>
+    auto WorkQueueBase::waitForResult(CALLABLE&& callable, ARGS&&... args)
     {
         checkCoroutine("waitForResult()");
         // derive callable's return type so we can specialize for void
         return WaitForResult<CALLABLE, decltype(std::forward<CALLABLE>(callable)())>()
-            (this, time, std::forward<CALLABLE>(callable));
+            (this, std::forward<CALLABLE>(callable), std::forward<ARGS>(args)...);
     }
 
 } // namespace LL