Merge pull request #3943 from secondlife/maxim/2025.04-chat-mention

#3758 initial chat mention support

35 files changed, 926 insertions, 84 deletions

diff --git a/indra/llui/CMakeLists.txt b/indra/llui/CMakeLists.txt
index a0314cb5f2..908e94b24c 100644
--- a/indra/llui/CMakeLists.txt
+++ b/indra/llui/CMakeLists.txt
@@ -18,6 +18,7 @@ set(llui_SOURCE_FILES
     llbadgeowner.cpp
     llbutton.cpp
     llchatentry.cpp
+    llchatmentionhelper.cpp
     llcheckboxctrl.cpp
     llclipboard.cpp
     llcombobox.cpp
@@ -130,6 +131,7 @@ set(llui_HEADER_FILES
     llcallbackmap.h
     llchatentry.h
     llchat.h
+    llchatmentionhelper.h
     llcheckboxctrl.h
     llclipboard.h
     llcombobox.h
diff --git a/indra/llui/llchatentry.cpp b/indra/llui/llchatentry.cpp
index e8d942b8af..7506cd99c0 100644
--- a/indra/llui/llchatentry.cpp
+++ b/indra/llui/llchatentry.cpp
@@ -52,6 +52,7 @@ LLChatEntry::LLChatEntry(const Params& p)
     mCurrentHistoryLine = mLineHistory.begin();
 
     mAutoIndent = false;
+    mShowChatMentionPicker = true;
     keepSelectionOnReturn(true);
 }
 
diff --git a/indra/llui/llchatmentionhelper.cpp b/indra/llui/llchatmentionhelper.cpp
new file mode 100644
index 0000000000..f7769b2cbe
--- /dev/null
+++ b/indra/llui/llchatmentionhelper.cpp
@@ -0,0 +1,151 @@
+/**
+* @file llchatmentionhelper.cpp
+*
+* $LicenseInfo:firstyear=2025&license=viewerlgpl$
+* Second Life Viewer Source Code
+* Copyright (C) 2025, 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"
+
+#include "llchatmentionhelper.h"
+#include "llfloater.h"
+#include "llfloaterreg.h"
+#include "lluictrl.h"
+
+constexpr char CHAT_MENTION_HELPER_FLOATER[] = "chat_mention_picker";
+
+bool LLChatMentionHelper::isActive(const LLUICtrl* ctrl) const
+{
+    return mHostHandle.get() == ctrl;
+}
+
+bool LLChatMentionHelper::isCursorInNameMention(const LLWString& wtext, S32 cursor_pos, S32* mention_start_pos) const
+{
+    if (cursor_pos <= 0 || cursor_pos > static_cast<S32>(wtext.size()))
+        return false;
+
+    // Find the beginning of the current word
+    S32 start = cursor_pos - 1;
+    while (start > 0 && wtext[start - 1] != U32(' ') && wtext[start - 1] != U32('\n'))
+    {
+        --start;
+    }
+
+    if (wtext[start] != U32('@'))
+        return false;
+
+    if (mention_start_pos)
+        *mention_start_pos = start;
+
+    S32 word_length = cursor_pos - start;
+
+    if (word_length == 1)
+    {
+        return true;
+    }
+
+    // Get the name after '@'
+    std::string name = wstring_to_utf8str(wtext.substr(start + 1, word_length - 1));
+    LLStringUtil::toLower(name);
+    for (const auto& av_name : mAvatarNames)
+    {
+        if (av_name == name || av_name.find(name) == 0)
+        {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void LLChatMentionHelper::showHelper(LLUICtrl* host_ctrl, S32 local_x, S32 local_y, const std::string& av_name, std::function<void(std::string)> cb)
+{
+    if (mHelperHandle.isDead())
+    {
+        LLFloater* av_picker_floater = LLFloaterReg::getInstance(CHAT_MENTION_HELPER_FLOATER);
+        mHelperHandle = av_picker_floater->getHandle();
+        mHelperCommitConn = av_picker_floater->setCommitCallback([&](LLUICtrl* ctrl, const LLSD& param) { onCommitName(param.asString()); });
+    }
+    setHostCtrl(host_ctrl);
+    mNameCommitCb = cb;
+
+    S32 floater_x, floater_y;
+    if (!host_ctrl->localPointToOtherView(local_x, local_y, &floater_x, &floater_y, gFloaterView))
+    {
+        LL_WARNS() << "Cannot show helper for non-floater controls." << LL_ENDL;
+        return;
+    }
+
+    LLFloater* av_picker_floater = mHelperHandle.get();
+    LLRect rect = av_picker_floater->getRect();
+    rect.setLeftTopAndSize(floater_x, floater_y + rect.getHeight(), rect.getWidth(), rect.getHeight());
+    av_picker_floater->setRect(rect);
+    av_picker_floater->openFloater(LLSD().with("av_name", av_name));
+}
+
+void LLChatMentionHelper::hideHelper(const LLUICtrl* ctrl)
+{
+    if ((ctrl && !isActive(ctrl)))
+    {
+        return;
+    }
+    setHostCtrl(nullptr);
+}
+
+bool LLChatMentionHelper::handleKey(const LLUICtrl* ctrl, KEY key, MASK mask)
+{
+    if (mHelperHandle.isDead() || !isActive(ctrl))
+    {
+        return false;
+    }
+
+    return mHelperHandle.get()->handleKey(key, mask, true);
+}
+
+void LLChatMentionHelper::onCommitName(std::string name_url)
+{
+    if (!mHostHandle.isDead() && mNameCommitCb)
+    {
+        mNameCommitCb(name_url);
+    }
+}
+
+void LLChatMentionHelper::setHostCtrl(LLUICtrl* host_ctrl)
+{
+    const LLUICtrl* pCurHostCtrl = mHostHandle.get();
+    if (pCurHostCtrl != host_ctrl)
+    {
+        mHostCtrlFocusLostConn.disconnect();
+        mHostHandle.markDead();
+        mNameCommitCb = {};
+
+        if (!mHelperHandle.isDead())
+        {
+            mHelperHandle.get()->closeFloater();
+        }
+
+        if (host_ctrl)
+        {
+            mHostHandle = host_ctrl->getHandle();
+            mHostCtrlFocusLostConn = host_ctrl->setFocusLostCallback(std::bind([&]() { hideHelper(getHostCtrl()); }));
+        }
+    }
+}
diff --git a/indra/llui/llchatmentionhelper.h b/indra/llui/llchatmentionhelper.h
new file mode 100644
index 0000000000..5f95d06f31
--- /dev/null
+++ b/indra/llui/llchatmentionhelper.h
@@ -0,0 +1,66 @@
+/**
+* @file llchatmentionhelper.h
+* @brief Header file for LLChatMentionHelper
+*
+* $LicenseInfo:firstyear=2025&license=viewerlgpl$
+* Second Life Viewer Source Code
+* Copyright (C) 2025, 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
+* $/LicenseInfo$
+*/
+
+#pragma once
+
+#include "llhandle.h"
+#include "llsingleton.h"
+
+#include <boost/signals2.hpp>
+
+class LLFloater;
+class LLUICtrl;
+
+class LLChatMentionHelper : public LLSingleton<LLChatMentionHelper>
+{
+    LLSINGLETON(LLChatMentionHelper) {}
+    ~LLChatMentionHelper() override {}
+
+public:
+
+    bool isActive(const LLUICtrl* ctrl) const;
+    bool isCursorInNameMention(const LLWString& wtext, S32 cursor_pos, S32* mention_start_pos = nullptr) const;
+    void showHelper(LLUICtrl* host_ctrl, S32 local_x, S32 local_y, const std::string& av_name, std::function<void(std::string)> commit_cb);
+    void hideHelper(const LLUICtrl* ctrl = nullptr);
+
+    bool handleKey(const LLUICtrl* ctrl, KEY key, MASK mask);
+    void onCommitName(std::string name_url);
+
+    void updateAvatarList(std::vector<std::string> av_names) { mAvatarNames = av_names; }
+
+protected:
+    void setHostCtrl(LLUICtrl* host_ctrl);
+    LLUICtrl* getHostCtrl() const { return mHostHandle.get(); }
+
+private:
+    LLHandle<LLUICtrl>  mHostHandle;
+    LLHandle<LLFloater> mHelperHandle;
+    boost::signals2::connection mHostCtrlFocusLostConn;
+    boost::signals2::connection mHelperCommitConn;
+    std::function<void(std::string)> mNameCommitCb;
+
+    std::vector<std::string> mAvatarNames;
+};
diff --git a/indra/llui/llflatlistview.cpp b/indra/llui/llflatlistview.cpp
index b8c833f4fd..8178bada42 100644
--- a/indra/llui/llflatlistview.cpp
+++ b/indra/llui/llflatlistview.cpp
@@ -459,6 +459,7 @@ LLFlatListView::LLFlatListView(const LLFlatListView::Params& p)
   , mNoItemsCommentTextbox(NULL)
   , mIsConsecutiveSelection(false)
   , mKeepSelectionVisibleOnReshape(p.keep_selection_visible_on_reshape)
+  , mFocusOnItemClicked(true)
 {
     mBorderThickness = getBorderWidth();
 
@@ -610,7 +611,10 @@ void LLFlatListView::onItemMouseClick(item_pair_t* item_pair, MASK mask)
         return;
     }
 
-    setFocus(true);
+    if (mFocusOnItemClicked)
+    {
+        setFocus(true);
+    }
 
     bool select_item = !isSelected(item_pair);
 
diff --git a/indra/llui/llflatlistview.h b/indra/llui/llflatlistview.h
index 0ea3115f30..6271231183 100644
--- a/indra/llui/llflatlistview.h
+++ b/indra/llui/llflatlistview.h
@@ -299,6 +299,8 @@ public:
 
     virtual S32 notify(const LLSD& info) override;
 
+    void setFocusOnItemClicked(bool b) { mFocusOnItemClicked = b; }
+
     virtual ~LLFlatListView();
 
 protected:
@@ -423,6 +425,8 @@ private:
 
     bool mKeepSelectionVisibleOnReshape;
 
+    bool mFocusOnItemClicked;
+
     /** All pairs of the list */
     pairs_list_t mItemPairs;
 
diff --git a/indra/llui/llstyle.cpp b/indra/llui/llstyle.cpp
index 4714665e8b..7a0e620d61 100644
--- a/indra/llui/llstyle.cpp
+++ b/indra/llui/llstyle.cpp
@@ -38,11 +38,13 @@ LLStyle::Params::Params()
     color("color", LLColor4::black),
     readonly_color("readonly_color", LLColor4::black),
     selected_color("selected_color", LLColor4::black),
+    highlight_bg_color("highlight_bg_color", LLColor4::green),
     alpha("alpha", 1.f),
     font("font", LLStyle::getDefaultFont()),
     image("image"),
     link_href("href"),
-    is_link("is_link")
+    is_link("is_link"),
+    draw_highlight_bg("draw_highlight_bg", false)
 {}
 
 
@@ -51,12 +53,14 @@ LLStyle::LLStyle(const LLStyle::Params& p)
     mColor(p.color),
     mReadOnlyColor(p.readonly_color),
     mSelectedColor(p.selected_color),
+    mHighlightBgColor(p.highlight_bg_color),
     mFont(p.font()),
     mLink(p.link_href),
     mIsLink(p.is_link.isProvided() ? p.is_link : !p.link_href().empty()),
     mDropShadow(p.drop_shadow),
     mImagep(p.image()),
-    mAlpha(p.alpha)
+    mAlpha(p.alpha),
+    mDrawHighlightBg(p.draw_highlight_bg)
 {}
 
 void LLStyle::setFont(const LLFontGL* font)
diff --git a/indra/llui/llstyle.h b/indra/llui/llstyle.h
index 0c78fe5a9f..71c3f88109 100644
--- a/indra/llui/llstyle.h
+++ b/indra/llui/llstyle.h
@@ -43,15 +43,25 @@ public:
         Optional<LLFontGL::ShadowType>  drop_shadow;
         Optional<LLUIColor>             color,
                                         readonly_color,
-                                        selected_color;
+                                        selected_color,
+                                        highlight_bg_color;
         Optional<F32>                   alpha;
         Optional<const LLFontGL*>       font;
         Optional<LLUIImage*>            image;
         Optional<std::string>           link_href;
         Optional<bool>                  is_link;
+        Optional<bool>                  draw_highlight_bg;
         Params();
     };
     LLStyle(const Params& p = Params());
+
+    enum EUnderlineLink
+    {
+        UNDERLINE_ALWAYS = 0,
+        UNDERLINE_ON_HOVER,
+        UNDERLINE_NEVER
+    };
+
 public:
     const LLUIColor& getColor() const { return mColor; }
     void setColor(const LLUIColor &color) { mColor = color; }
@@ -84,6 +94,9 @@ public:
 
     bool isImage() const { return mImagep.notNull(); }
 
+    bool getDrawHighlightBg() const { return mDrawHighlightBg; }
+    const LLUIColor& getHighlightBgColor() const { return mHighlightBgColor; }
+
     bool operator==(const LLStyle &rhs) const
     {
         return
@@ -91,11 +104,13 @@ public:
             && mColor == rhs.mColor
             && mReadOnlyColor == rhs.mReadOnlyColor
             && mSelectedColor == rhs.mSelectedColor
+            && mHighlightBgColor == rhs.mHighlightBgColor
             && mFont == rhs.mFont
             && mLink == rhs.mLink
             && mImagep == rhs.mImagep
             && mDropShadow == rhs.mDropShadow
-            && mAlpha == rhs.mAlpha;
+            && mAlpha == rhs.mAlpha
+            && mDrawHighlightBg == rhs.mDrawHighlightBg;
     }
 
     bool operator!=(const LLStyle& rhs) const { return !(*this == rhs); }
@@ -112,11 +127,13 @@ private:
     LLUIColor           mColor;
     LLUIColor           mReadOnlyColor;
     LLUIColor           mSelectedColor;
+    LLUIColor           mHighlightBgColor;
     const LLFontGL*     mFont;
     LLPointer<LLUIImage> mImagep;
     F32                 mAlpha;
     bool                mVisible;
     bool                mIsLink;
+    bool                mDrawHighlightBg;
 };
 
 typedef LLPointer<LLStyle> LLStyleSP;
diff --git a/indra/llui/lltextbase.cpp b/indra/llui/lltextbase.cpp
index 41e7094163..c1b01f420b 100644
--- a/indra/llui/lltextbase.cpp
+++ b/indra/llui/lltextbase.cpp
@@ -460,6 +460,62 @@ std::vector<LLRect> LLTextBase::getSelectionRects()
     return selection_rects;
 }
 
+std::vector<std::pair<LLRect, LLUIColor>> LLTextBase::getHighlightedBgRects()
+{
+    std::vector<std::pair<LLRect, LLUIColor>> highlight_rects;
+
+    LLRect content_display_rect = getVisibleDocumentRect();
+
+    // binary search for line that starts before top of visible buffer
+    line_list_t::const_iterator line_iter =
+        std::lower_bound(mLineInfoList.begin(), mLineInfoList.end(), content_display_rect.mTop, compare_bottom());
+    line_list_t::const_iterator end_iter =
+        std::upper_bound(mLineInfoList.begin(), mLineInfoList.end(), content_display_rect.mBottom, compare_top());
+
+    for (; line_iter != end_iter; ++line_iter)
+    {
+            segment_set_t::iterator segment_iter;
+            S32 segment_offset;
+            getSegmentAndOffset(line_iter->mDocIndexStart, &segment_iter, &segment_offset);
+
+            // Use F32 otherwise a string of multiple segments
+            // will accumulate a large error
+            F32 left_precise  = (F32)line_iter->mRect.mLeft;
+            F32 right_precise = (F32)line_iter->mRect.mLeft;
+
+            for (; segment_iter != mSegments.end(); ++segment_iter)
+            {
+                LLTextSegmentPtr segmentp = *segment_iter;
+
+                S32 segment_line_start = segmentp->getStart() + segment_offset;
+                S32 segment_line_end = llmin(segmentp->getEnd(), line_iter->mDocIndexEnd);
+
+                if (segment_line_start > segment_line_end)
+                    break;
+
+                F32 segment_width  = 0;
+                S32 segment_height = 0;
+
+                S32 num_chars = segment_line_end - segment_line_start;
+                segmentp->getDimensionsF32(segment_offset, num_chars, segment_width, segment_height);
+                right_precise += segment_width;
+
+                if (segmentp->getStyle()->getDrawHighlightBg())
+                {
+                    LLRect selection_rect;
+                    selection_rect.mLeft = (S32)left_precise;
+                    selection_rect.mRight = (S32)right_precise;
+                    selection_rect.mBottom = line_iter->mRect.mBottom;
+                    selection_rect.mTop = line_iter->mRect.mTop;
+
+                    highlight_rects.push_back(std::pair(selection_rect, segmentp->getStyle()->getHighlightBgColor()));
+                }
+                left_precise += segment_width;
+            }
+    }
+    return highlight_rects;
+}
+
 // Draws the black box behind the selected text
 void LLTextBase::drawSelectionBackground()
 {
@@ -529,6 +585,71 @@ void LLTextBase::drawSelectionBackground()
     }
 }
 
+void LLTextBase::drawHighlightedBackground()
+{
+    if (!mLineInfoList.empty())
+    {
+        std::vector<std::pair<LLRect, LLUIColor>> highlight_rects = getHighlightedBgRects();
+
+        if (highlight_rects.empty())
+            return;
+
+        gGL.getTexUnit(0)->unbind(LLTexUnit::TT_TEXTURE);
+
+        LLRect content_display_rect = getVisibleDocumentRect();
+
+        for (std::vector<std::pair<LLRect, LLUIColor>>::iterator rect_it = highlight_rects.begin();
+             rect_it != highlight_rects.end(); ++rect_it)
+        {
+            LLRect selection_rect = rect_it->first;
+            const LLColor4& color = rect_it->second;
+            if (mScroller)
+            {
+                // If scroller is On content_display_rect has correct rect and safe to use as is
+                // Note: we might need to account for border
+                selection_rect.translate(mVisibleTextRect.mLeft - content_display_rect.mLeft, mVisibleTextRect.mBottom - content_display_rect.mBottom);
+            }
+            else
+            {
+                // If scroller is Off content_display_rect will have rect from document, adjusted to text width, heigh and position
+                // and we have to acount for offset depending on position
+                S32 v_delta = 0;
+                S32 h_delta = 0;
+                switch (mVAlign)
+                {
+                case LLFontGL::TOP:
+                    v_delta = mVisibleTextRect.mTop - content_display_rect.mTop - mVPad;
+                    break;
+                case LLFontGL::VCENTER:
+                    v_delta = (llmax(mVisibleTextRect.getHeight() - content_display_rect.mTop, -content_display_rect.mBottom) + (mVisibleTextRect.mBottom - content_display_rect.mBottom)) / 2;
+                    break;
+                case LLFontGL::BOTTOM:
+                    v_delta = mVisibleTextRect.mBottom - content_display_rect.mBottom;
+                    break;
+                default:
+                    break;
+                }
+                switch (mHAlign)
+                {
+                case LLFontGL::LEFT:
+                    h_delta = mVisibleTextRect.mLeft - content_display_rect.mLeft + mHPad;
+                    break;
+                case LLFontGL::HCENTER:
+                    h_delta = (llmax(mVisibleTextRect.getWidth() - content_display_rect.mLeft, -content_display_rect.mRight) + (mVisibleTextRect.mRight - content_display_rect.mRight)) / 2;
+                    break;
+                case LLFontGL::RIGHT:
+                    h_delta = mVisibleTextRect.mRight - content_display_rect.mRight;
+                    break;
+                default:
+                    break;
+                }
+                selection_rect.translate(h_delta, v_delta);
+            }
+            gl_rect_2d(selection_rect, color);
+        }
+    }
+}
+
 void LLTextBase::drawCursor()
 {
     F32 alpha = getDrawContext().mAlpha;
@@ -1399,6 +1520,7 @@ void LLTextBase::draw()
             drawChild(mDocumentView);
         }
 
+        drawHighlightedBackground();
         drawSelectionBackground();
         drawText();
         drawCursor();
@@ -2200,20 +2322,20 @@ static LLUIImagePtr image_from_icon_name(const std::string& icon_name)
 }
 
 
-void LLTextBase::appendTextImpl(const std::string &new_text, const LLStyle::Params& input_params)
+void LLTextBase::appendTextImpl(const std::string& new_text, const LLStyle::Params& input_params, bool force_slurl)
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_UI;
     LLStyle::Params style_params(getStyleParams());
     style_params.overwriteFrom(input_params);
 
     S32 part = (S32)LLTextParser::WHOLE;
-    if (mParseHTML && !style_params.is_link) // Don't search for URLs inside a link segment (STORM-358).
+    if ((mParseHTML || force_slurl) && !style_params.is_link) // Don't search for URLs inside a link segment (STORM-358).
     {
         S32 start=0,end=0;
         LLUrlMatch match;
         std::string text = new_text;
         while (LLUrlRegistry::instance().findUrl(text, match,
-                boost::bind(&LLTextBase::replaceUrl, this, _1, _2, _3), isContentTrusted() || mAlwaysShowIcons))
+                boost::bind(&LLTextBase::replaceUrl, this, _1, _2, _3), isContentTrusted() || mAlwaysShowIcons, force_slurl))
         {
             start = match.getStart();
             end = match.getEnd()+1;
@@ -2245,7 +2367,7 @@ void LLTextBase::appendTextImpl(const std::string &new_text, const LLStyle::Para
             }
 
             // output the styled Url
-            appendAndHighlightTextImpl(match.getLabel(), part, link_params, match.underlineOnHoverOnly());
+            appendAndHighlightTextImpl(match.getLabel(), part, link_params, match.getUnderline());
             bool tooltip_required =  !match.getTooltip().empty();
 
             // set the tooltip for the Url label
@@ -2260,7 +2382,7 @@ void LLTextBase::appendTextImpl(const std::string &new_text, const LLStyle::Para
             {
                 link_params.color = LLColor4::grey;
                 link_params.readonly_color = LLColor4::grey;
-                appendAndHighlightTextImpl(label, part, link_params, match.underlineOnHoverOnly());
+                appendAndHighlightTextImpl(label, part, link_params, match.getUnderline());
 
                 // set the tooltip for the query part of url
                 if (tooltip_required)
@@ -2428,7 +2550,7 @@ void LLTextBase::appendWidget(const LLInlineViewSegment::Params& params, const s
     insertStringNoUndo(getLength(), widget_wide_text, &segments);
 }
 
-void LLTextBase::appendAndHighlightTextImpl(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, bool underline_on_hover_only)
+void LLTextBase::appendAndHighlightTextImpl(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, e_underline underline_link)
 {
     // Save old state
     S32 selection_start = mSelectionStart;
@@ -2458,7 +2580,7 @@ void LLTextBase::appendAndHighlightTextImpl(const std::string &new_text, S32 hig
             S32 cur_length = getLength();
             LLStyleConstSP sp(new LLStyle(highlight_params));
             LLTextSegmentPtr segmentp;
-            if (underline_on_hover_only || mSkipLinkUnderline)
+            if ((underline_link == e_underline::UNDERLINE_ON_HOVER) || mSkipLinkUnderline)
             {
                 highlight_params.font.style("NORMAL");
                 LLStyleConstSP normal_sp(new LLStyle(highlight_params));
@@ -2482,7 +2604,7 @@ void LLTextBase::appendAndHighlightTextImpl(const std::string &new_text, S32 hig
         S32 segment_start = old_length;
         S32 segment_end = old_length + static_cast<S32>(wide_text.size());
         LLStyleConstSP sp(new LLStyle(style_params));
-        if (underline_on_hover_only || mSkipLinkUnderline)
+        if ((underline_link == e_underline::UNDERLINE_ON_HOVER) || mSkipLinkUnderline)
         {
             LLStyle::Params normal_style_params(style_params);
             normal_style_params.font.style("NORMAL");
@@ -2516,7 +2638,7 @@ void LLTextBase::appendAndHighlightTextImpl(const std::string &new_text, S32 hig
     }
 }
 
-void LLTextBase::appendAndHighlightText(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, bool underline_on_hover_only)
+void LLTextBase::appendAndHighlightText(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, e_underline underline_link)
 {
     if (new_text.empty())
     {
@@ -2531,7 +2653,7 @@ void LLTextBase::appendAndHighlightText(const std::string &new_text, S32 highlig
         if (pos != start)
         {
             std::string str = std::string(new_text,start,pos-start);
-            appendAndHighlightTextImpl(str, highlight_part, style_params, underline_on_hover_only);
+            appendAndHighlightTextImpl(str, highlight_part, style_params, underline_link);
         }
         appendLineBreakSegment(style_params);
         start = pos+1;
@@ -2539,7 +2661,7 @@ void LLTextBase::appendAndHighlightText(const std::string &new_text, S32 highlig
     }
 
     std::string str = std::string(new_text, start, new_text.length() - start);
-    appendAndHighlightTextImpl(str, highlight_part, style_params, underline_on_hover_only);
+    appendAndHighlightTextImpl(str, highlight_part, style_params, underline_link);
 }
 
 
@@ -3336,6 +3458,7 @@ LLNormalTextSegment::LLNormalTextSegment( LLStyleConstSP style, S32 start, S32 e
     mLastGeneration(-1)
 {
     mFontHeight = mStyle->getFont()->getLineHeight();
+    mCanEdit = !mStyle->getDrawHighlightBg();
 
     LLUIImagePtr image = mStyle->getImage();
     if (image.notNull())
diff --git a/indra/llui/lltextbase.h b/indra/llui/lltextbase.h
index e62b56963d..8ca653acb9 100644
--- a/indra/llui/lltextbase.h
+++ b/indra/llui/lltextbase.h
@@ -35,6 +35,7 @@
 #include "llstyle.h"
 #include "llkeywords.h"
 #include "llpanel.h"
+#include "llurlmatch.h"
 
 #include <string>
 #include <vector>
@@ -139,7 +140,7 @@ public:
     /*virtual*/ S32                 getNumChars(S32 num_pixels, S32 segment_offset, S32 line_offset, S32 max_chars, S32 line_ind) const;
     /*virtual*/ void                updateLayout(const class LLTextBase& editor);
     /*virtual*/ F32                 draw(S32 start, S32 end, S32 selection_start, S32 selection_end, const LLRectf& draw_rect);
-    /*virtual*/ bool                canEdit() const { return true; }
+    /*virtual*/ bool                canEdit() const { return mCanEdit; }
     /*virtual*/ const LLUIColor&     getColor() const                    { return mStyle->getColor(); }
     /*virtual*/ LLStyleConstSP      getStyle() const                    { return mStyle; }
     /*virtual*/ void                setStyle(LLStyleConstSP style)  { mStyle = style; }
@@ -161,6 +162,8 @@ protected:
     virtual     const LLWString&    getWText()  const;
     virtual     const S32           getLength() const;
 
+    void setAllowEdit(bool can_edit) { mCanEdit = can_edit; }
+
 protected:
     class LLTextBase&   mEditor;
     LLStyleConstSP      mStyle;
@@ -169,6 +172,8 @@ protected:
     std::string         mTooltip;
     boost::signals2::connection mImageLoadedConnection;
 
+    bool mCanEdit { true };
+
     // font rendering
     LLFontVertexBuffer  mFontBufferPreSelection;
     LLFontVertexBuffer  mFontBufferSelection;
@@ -606,6 +611,7 @@ protected:
         bool operator()(const LLTextSegmentPtr& a, const LLTextSegmentPtr& b) const;
     };
     typedef std::multiset<LLTextSegmentPtr, compare_segment_end> segment_set_t;
+    typedef LLStyle::EUnderlineLink e_underline;
 
     // member functions
     LLTextBase(const Params &p);
@@ -619,12 +625,13 @@ protected:
     virtual void                    drawSelectionBackground(); // draws the black box behind the selected text
     void                            drawCursor();
     void                            drawText();
+    void                            drawHighlightedBackground();
 
     // modify contents
     S32                             insertStringNoUndo(S32 pos, const LLWString &wstr, segment_vec_t* segments = NULL); // returns num of chars actually inserted
     S32                             removeStringNoUndo(S32 pos, S32 length);
     S32                             overwriteCharNoUndo(S32 pos, llwchar wc);
-    void                            appendAndHighlightText(const std::string &new_text, S32 highlight_part, const LLStyle::Params& stylep, bool underline_on_hover_only = false);
+    void                            appendAndHighlightText(const std::string &new_text, S32 highlight_part, const LLStyle::Params& stylep, e_underline underline_link = e_underline::UNDERLINE_ALWAYS);
 
 
     // manage segments
@@ -672,8 +679,9 @@ protected:
     // avatar names are looked up.
     void replaceUrl(const std::string &url, const std::string &label, const std::string& icon);
 
-    void                            appendTextImpl(const std::string &new_text, const LLStyle::Params& input_params = LLStyle::Params());
-    void                            appendAndHighlightTextImpl(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, bool underline_on_hover_only = false);
+    void                            appendTextImpl(const std::string &new_text, const LLStyle::Params& input_params = LLStyle::Params(), bool force_slurl = false);
+    void                            appendAndHighlightTextImpl(const std::string &new_text, S32 highlight_part, const LLStyle::Params& style_params, e_underline underline_link = e_underline::UNDERLINE_ALWAYS);
+    S32 normalizeUri(std::string& uri);
 
 protected:
     // virtual
@@ -683,6 +691,7 @@ protected:
     }
 
     std::vector<LLRect> getSelectionRects();
+    std::vector<std::pair<LLRect, LLUIColor>> getHighlightedBgRects();
 
 protected:
     // text segmentation and flow
diff --git a/indra/llui/lltexteditor.cpp b/indra/llui/lltexteditor.cpp
index fe4cce29ab..cfe729be06 100644
--- a/indra/llui/lltexteditor.cpp
+++ b/indra/llui/lltexteditor.cpp
@@ -60,6 +60,7 @@
 #include "llurlregistry.h"
 #include "lltooltip.h"
 #include "llmenugl.h"
+#include "llchatmentionhelper.h"
 
 #include <queue>
 #include "llcombobox.h"
@@ -270,6 +271,7 @@ LLTextEditor::LLTextEditor(const LLTextEditor::Params& p) :
     mPrevalidator(p.prevalidator()),
     mShowContextMenu(p.show_context_menu),
     mShowEmojiHelper(p.show_emoji_helper),
+    mShowChatMentionPicker(false),
     mEnableTooltipPaste(p.enable_tooltip_paste),
     mPassDelete(false),
     mKeepSelectionOnReturn(false)
@@ -714,6 +716,30 @@ void LLTextEditor::handleEmojiCommit(llwchar emoji)
     }
 }
 
+void LLTextEditor::handleMentionCommit(std::string name_url)
+{
+    S32 mention_start_pos;
+    if (LLChatMentionHelper::instance().isCursorInNameMention(getWText(), mCursorPos, &mention_start_pos))
+    {
+        remove(mention_start_pos, mCursorPos - mention_start_pos, true);
+        insert(mention_start_pos, utf8str_to_wstring(name_url), false, LLTextSegmentPtr());
+
+        std::string new_text(wstring_to_utf8str(getConvertedText()));
+        clear();
+        appendTextImpl(new_text, LLStyle::Params(), true);
+
+        segment_set_t::const_iterator it = getSegIterContaining(mention_start_pos);
+        if (it != mSegments.end())
+        {
+            setCursorPos((*it)->getEnd() + 1);
+        }
+        else
+        {
+            setCursorPos(mention_start_pos);
+        }
+    }
+}
+
 bool LLTextEditor::handleMouseDown(S32 x, S32 y, MASK mask)
 {
     bool    handled = false;
@@ -1103,6 +1129,7 @@ void LLTextEditor::removeCharOrTab()
         }
 
         tryToShowEmojiHelper();
+        tryToShowMentionHelper();
     }
     else
     {
@@ -1128,6 +1155,7 @@ void LLTextEditor::removeChar()
         setCursorPos(mCursorPos - 1);
         removeChar(mCursorPos);
         tryToShowEmojiHelper();
+        tryToShowMentionHelper();
     }
     else
     {
@@ -1189,6 +1217,7 @@ void LLTextEditor::addChar(llwchar wc)
 
     setCursorPos(mCursorPos + addChar( mCursorPos, wc ));
     tryToShowEmojiHelper();
+    tryToShowMentionHelper();
 
     if (!mReadOnly && mAutoreplaceCallback != NULL)
     {
@@ -1247,6 +1276,31 @@ void LLTextEditor::tryToShowEmojiHelper()
     }
 }
 
+void LLTextEditor::tryToShowMentionHelper()
+{
+    if (mReadOnly || !mShowChatMentionPicker)
+        return;
+
+    S32 mention_start_pos;
+    LLWString text(getWText());
+    if (LLChatMentionHelper::instance().isCursorInNameMention(text, mCursorPos, &mention_start_pos))
+    {
+        const LLRect cursor_rect(getLocalRectFromDocIndex(mention_start_pos));
+        std::string name_part(wstring_to_utf8str(text.substr(mention_start_pos, mCursorPos - mention_start_pos)));
+        name_part.erase(0, 1);
+        auto cb = [this](std::string name_url)
+        {
+            handleMentionCommit(name_url);
+        };
+        LLChatMentionHelper::instance().showHelper(this, cursor_rect.mLeft, cursor_rect.mTop, name_part, cb);
+    }
+    else
+    {
+        LLChatMentionHelper::instance().hideHelper();
+    }
+}
+
+
 void LLTextEditor::addLineBreakChar(bool group_together)
 {
     if( !getEnabled() )
@@ -1873,7 +1927,7 @@ bool LLTextEditor::handleKeyHere(KEY key, MASK mask )
     // not handled and let the parent take care of field movement.
     if (KEY_TAB == key && mTabsToNextField)
     {
-        return false;
+        return mShowChatMentionPicker && LLChatMentionHelper::instance().handleKey(this, key, mask);
     }
 
     if (mReadOnly && mScroller)
@@ -1884,9 +1938,13 @@ bool LLTextEditor::handleKeyHere(KEY key, MASK mask )
     }
     else
     {
-        if (!mReadOnly && mShowEmojiHelper && LLEmojiHelper::instance().handleKey(this, key, mask))
+        if (!mReadOnly)
         {
-            return true;
+            if ((mShowEmojiHelper && LLEmojiHelper::instance().handleKey(this, key, mask)) ||
+                (mShowChatMentionPicker && LLChatMentionHelper::instance().handleKey(this, key, mask)))
+            {
+                return true;
+            }
         }
 
         if (mEnableTooltipPaste &&
@@ -3083,3 +3141,21 @@ S32 LLTextEditor::spacesPerTab()
 {
     return SPACES_PER_TAB;
 }
+
+LLWString LLTextEditor::getConvertedText() const
+{
+    LLWString text = getWText();
+    S32 diff = 0;
+    for (auto segment : mSegments)
+    {
+        if (segment && segment->getStyle() && segment->getStyle()->getDrawHighlightBg())
+        {
+            S32 seg_length = segment->getEnd() - segment->getStart();
+            std::string slurl = segment->getStyle()->getLinkHREF();
+
+            text.replace(segment->getStart() + diff, seg_length, utf8str_to_wstring(slurl));
+            diff += (S32)slurl.size() - seg_length;
+        }
+    }
+    return text;
+}
diff --git a/indra/llui/lltexteditor.h b/indra/llui/lltexteditor.h
index 353a7b93a0..882bb145df 100644
--- a/indra/llui/lltexteditor.h
+++ b/indra/llui/lltexteditor.h
@@ -95,6 +95,8 @@ public:
     void    insertEmoji(llwchar emoji);
     void    handleEmojiCommit(llwchar emoji);
 
+    void handleMentionCommit(std::string name_url);
+
     // mousehandler overrides
     virtual bool    handleMouseDown(S32 x, S32 y, MASK mask);
     virtual bool    handleMouseUp(S32 x, S32 y, MASK mask);
@@ -212,6 +214,8 @@ public:
 
     void            setPassDelete(bool b) { mPassDelete = b; }
 
+    LLWString       getConvertedText() const;
+
 protected:
     void            showContextMenu(S32 x, S32 y);
     void            drawPreeditMarker();
@@ -254,6 +258,7 @@ protected:
     S32             remove(S32 pos, S32 length, bool group_with_next_op);
 
     void            tryToShowEmojiHelper();
+    void            tryToShowMentionHelper();
     void            focusLostHelper();
     void            updateAllowingLanguageInput();
     bool            hasPreeditString() const;
@@ -291,6 +296,7 @@ protected:
 
     bool                mAutoIndent;
     bool                mParseOnTheFly;
+    bool                mShowChatMentionPicker;
 
     void                updateLinkSegments();
     void                keepSelectionOnReturn(bool keep) { mKeepSelectionOnReturn = keep; }
diff --git a/indra/llui/llurlentry.cpp b/indra/llui/llurlentry.cpp
index 77f132e9d8..34138da34d 100644
--- a/indra/llui/llurlentry.cpp
+++ b/indra/llui/llurlentry.cpp
@@ -29,7 +29,6 @@
 #include "llurlentry.h"
 #include "lluictrl.h"
 #include "lluri.h"
-#include "llurlmatch.h"
 #include "llurlregistry.h"
 #include "lluriparser.h"
 
@@ -48,7 +47,7 @@
 // Utility functions
 std::string localize_slapp_label(const std::string& url, const std::string& full_name);
 
-
+LLUUID LLUrlEntryBase::sAgentID(LLUUID::null);
 LLUrlEntryBase::LLUrlEntryBase()
 {
 }
@@ -68,7 +67,7 @@ std::string LLUrlEntryBase::getIcon(const std::string &url)
     return mIcon;
 }
 
-LLStyle::Params LLUrlEntryBase::getStyle() const
+LLStyle::Params LLUrlEntryBase::getStyle(const std::string &url) const
 {
     LLStyle::Params style_params;
     style_params.color = LLUIColorTable::instance().getColor("HTMLLinkColor");
@@ -667,10 +666,14 @@ std::string LLUrlEntryAgent::getTooltip(const std::string &string) const
     return LLTrans::getString("TooltipAgentUrl");
 }
 
-bool LLUrlEntryAgent::underlineOnHoverOnly(const std::string &string) const
+LLStyle::EUnderlineLink LLUrlEntryAgent::getUnderline(const std::string& string) const
 {
     std::string url = getUrl(string);
-    return LLStringUtil::endsWith(url, "/about") || LLStringUtil::endsWith(url, "/inspect");
+    if (LLStringUtil::endsWith(url, "/about") || LLStringUtil::endsWith(url, "/inspect"))
+    {
+        return LLStyle::EUnderlineLink::UNDERLINE_ON_HOVER;
+    }
+    return LLStyle::EUnderlineLink::UNDERLINE_ALWAYS;
 }
 
 std::string LLUrlEntryAgent::getLabel(const std::string &url, const LLUrlLabelCallback &cb)
@@ -712,11 +715,12 @@ std::string LLUrlEntryAgent::getLabel(const std::string &url, const LLUrlLabelCa
     }
 }
 
-LLStyle::Params LLUrlEntryAgent::getStyle() const
+LLStyle::Params LLUrlEntryAgent::getStyle(const std::string &url) const
 {
-    LLStyle::Params style_params = LLUrlEntryBase::getStyle();
+    LLStyle::Params style_params = LLUrlEntryBase::getStyle(url);
     style_params.color = LLUIColorTable::instance().getColor("HTMLLinkColor");
     style_params.readonly_color = LLUIColorTable::instance().getColor("HTMLLinkColor");
+
     return style_params;
 }
 
@@ -751,6 +755,10 @@ std::string localize_slapp_label(const std::string& url, const std::string& full
     {
         return LLTrans::getString("SLappAgentRemoveFriend") + " " + full_name;
     }
+    if (LLStringUtil::endsWith(url, "/mention"))
+    {
+        return "@" + full_name;
+    }
     return full_name;
 }
 
@@ -762,6 +770,34 @@ std::string LLUrlEntryAgent::getIcon(const std::string &url)
     return mIcon;
 }
 
+///
+/// LLUrlEntryAgentMention Describes a chat mention Url, e.g.,
+/// secondlife:///app/agent/0e346d8b-4433-4d66-a6b0-fd37083abc4c/mention
+///
+LLUrlEntryAgentMention::LLUrlEntryAgentMention()
+{
+    mPattern  = boost::regex(APP_HEADER_REGEX "/agent/[\\da-f-]+/mention", boost::regex::perl | boost::regex::icase);
+    mMenuName = "menu_url_agent.xml";
+    mIcon = std::string();
+}
+
+LLStyle::EUnderlineLink LLUrlEntryAgentMention::getUnderline(const std::string& string) const
+{
+    return LLStyle::EUnderlineLink::UNDERLINE_NEVER;
+}
+
+LLStyle::Params LLUrlEntryAgentMention::getStyle(const std::string& url) const
+{
+    LLStyle::Params style_params = LLUrlEntryAgent::getStyle(url);
+    style_params.font.style = "NORMAL";
+    style_params.draw_highlight_bg = true;
+
+    LLUUID agent_id(getIDStringFromUrl(url));
+    style_params.highlight_bg_color = LLUIColorTable::instance().getColor((agent_id == sAgentID) ? "ChatSelfMentionHighlight" : "ChatMentionHighlight");
+
+    return style_params;
+}
+
 //
 // LLUrlEntryAgentName describes a Second Life agent name Url, e.g.,
 // secondlife:///app/agent/0e346d8b-4433-4d66-a6b0-fd37083abc4c/(completename|displayname|username)
@@ -823,7 +859,7 @@ std::string LLUrlEntryAgentName::getLabel(const std::string &url, const LLUrlLab
     }
 }
 
-LLStyle::Params LLUrlEntryAgentName::getStyle() const
+LLStyle::Params LLUrlEntryAgentName::getStyle(const std::string &url) const
 {
     // don't override default colors
     return LLStyle::Params().is_link(false);
@@ -959,9 +995,9 @@ std::string LLUrlEntryGroup::getLabel(const std::string &url, const LLUrlLabelCa
     }
 }
 
-LLStyle::Params LLUrlEntryGroup::getStyle() const
+LLStyle::Params LLUrlEntryGroup::getStyle(const std::string &url) const
 {
-    LLStyle::Params style_params = LLUrlEntryBase::getStyle();
+    LLStyle::Params style_params = LLUrlEntryBase::getStyle(url);
     style_params.color = LLUIColorTable::instance().getColor("HTMLLinkColor");
     style_params.readonly_color = LLUIColorTable::instance().getColor("HTMLLinkColor");
     return style_params;
@@ -1037,7 +1073,6 @@ std::string LLUrlEntryChat::getLabel(const std::string &url, const LLUrlLabelCal
 }
 
 // LLUrlEntryParcel statics.
-LLUUID  LLUrlEntryParcel::sAgentID(LLUUID::null);
 LLUUID  LLUrlEntryParcel::sSessionID(LLUUID::null);
 LLHost  LLUrlEntryParcel::sRegionHost;
 bool    LLUrlEntryParcel::sDisconnected(false);
@@ -1371,17 +1406,17 @@ std::string LLUrlEntrySLLabel::getTooltip(const std::string &string) const
     return LLUrlEntryBase::getTooltip(string);
 }
 
-bool LLUrlEntrySLLabel::underlineOnHoverOnly(const std::string &string) const
+LLStyle::EUnderlineLink LLUrlEntrySLLabel::getUnderline(const std::string& string) const
 {
     std::string url = getUrl(string);
-    LLUrlMatch match;
+    LLUrlMatch  match;
     if (LLUrlRegistry::instance().findUrl(url, match))
     {
-        return match.underlineOnHoverOnly();
+        return match.getUnderline();
     }
 
     // unrecognized URL? should not happen
-    return LLUrlEntryBase::underlineOnHoverOnly(string);
+    return LLUrlEntryBase::getUnderline(string);
 }
 
 //
@@ -1445,7 +1480,7 @@ std::string LLUrlEntryNoLink::getLabel(const std::string &url, const LLUrlLabelC
     return getUrl(url);
 }
 
-LLStyle::Params LLUrlEntryNoLink::getStyle() const
+LLStyle::Params LLUrlEntryNoLink::getStyle(const std::string &url) const
 {
     // Don't render as URL (i.e. no context menu or hand cursor).
     return LLStyle::Params().is_link(false);
diff --git a/indra/llui/llurlentry.h b/indra/llui/llurlentry.h
index fffee88496..740e99acfd 100644
--- a/indra/llui/llurlentry.h
+++ b/indra/llui/llurlentry.h
@@ -85,7 +85,7 @@ public:
     virtual std::string getIcon(const std::string &url);
 
     /// Return the style to render the displayed text
-    virtual LLStyle::Params getStyle() const;
+    virtual LLStyle::Params getStyle(const std::string &url) const;
 
     /// Given a matched Url, return a tooltip string for the hyperlink
     virtual std::string getTooltip(const std::string &string) const { return mTooltip; }
@@ -96,11 +96,12 @@ public:
     /// Return the name of a SL location described by this Url, if any
     virtual std::string getLocation(const std::string &url) const { return ""; }
 
-    /// Should this link text be underlined only when mouse is hovered over it?
-    virtual bool underlineOnHoverOnly(const std::string &string) const { return false; }
+    virtual LLStyle::EUnderlineLink getUnderline(const std::string& string) const { return LLStyle::EUnderlineLink::UNDERLINE_ALWAYS; }
 
     virtual bool isTrusted() const { return false; }
 
+    virtual bool getSkipProfileIcon(const std::string& string) const { return false; }
+
     virtual LLUUID  getID(const std::string &string) const { return LLUUID::null; }
 
     bool isLinkDisabled() const;
@@ -109,6 +110,8 @@ public:
 
     virtual bool isSLURLvalid(const std::string &url) const { return true; };
 
+    static void setAgentID(const LLUUID& id) { sAgentID = id; }
+
 protected:
     std::string getIDStringFromUrl(const std::string &url) const;
     std::string escapeUrl(const std::string &url) const;
@@ -130,6 +133,8 @@ protected:
     std::string                                     mMenuName;
     std::string                                     mTooltip;
     std::multimap<std::string, LLUrlEntryObserver>  mObservers;
+
+    static LLUUID sAgentID;
 };
 
 ///
@@ -224,9 +229,11 @@ public:
     /*virtual*/ std::string getLabel(const std::string &url, const LLUrlLabelCallback &cb);
     /*virtual*/ std::string getIcon(const std::string &url);
     /*virtual*/ std::string getTooltip(const std::string &string) const;
-    /*virtual*/ LLStyle::Params getStyle() const;
+    /*virtual*/ LLStyle::Params getStyle(const std::string &url) const;
     /*virtual*/ LLUUID  getID(const std::string &string) const;
-    /*virtual*/ bool underlineOnHoverOnly(const std::string &string) const;
+
+    LLStyle::EUnderlineLink getUnderline(const std::string& string) const;
+
 protected:
     /*virtual*/ void callObservers(const std::string &id, const std::string &label, const std::string& icon);
 private:
@@ -237,6 +244,19 @@ private:
 };
 
 ///
+/// LLUrlEntryAgentMention Describes a chat mention Url, e.g.,
+/// secondlife:///app/agent/0e346d8b-4433-4d66-a6b0-fd37083abc4c/mention
+class LLUrlEntryAgentMention : public LLUrlEntryAgent
+{
+public:
+    LLUrlEntryAgentMention();
+
+    LLStyle::Params getStyle(const std::string& url) const;
+    LLStyle::EUnderlineLink getUnderline(const std::string& string) const;
+    bool getSkipProfileIcon(const std::string& string) const { return true; };
+};
+
+///
 /// LLUrlEntryAgentName Describes a Second Life agent name Url, e.g.,
 /// secondlife:///app/agent/0e346d8b-4433-4d66-a6b0-fd37083abc4c/(completename|displayname|username)
 /// that displays various forms of user name
@@ -257,7 +277,7 @@ public:
         mAvatarNameCacheConnections.clear();
     }
     /*virtual*/ std::string getLabel(const std::string &url, const LLUrlLabelCallback &cb);
-    /*virtual*/ LLStyle::Params getStyle() const;
+    /*virtual*/ LLStyle::Params getStyle(const std::string &url) const;
 protected:
     // override this to pull out relevant name fields
     virtual std::string getName(const LLAvatarName& avatar_name) = 0;
@@ -339,7 +359,7 @@ class LLUrlEntryGroup : public LLUrlEntryBase
 public:
     LLUrlEntryGroup();
     /*virtual*/ std::string getLabel(const std::string &url, const LLUrlLabelCallback &cb);
-    /*virtual*/ LLStyle::Params getStyle() const;
+    /*virtual*/ LLStyle::Params getStyle(const std::string &url) const;
     /*virtual*/ LLUUID  getID(const std::string &string) const;
 private:
     void onGroupNameReceived(const LLUUID& id, const std::string& name, bool is_group);
@@ -411,17 +431,15 @@ public:
     // Processes parcel label and triggers notifying observers.
     static void processParcelInfo(const LLParcelData& parcel_data);
 
-    // Next 4 setters are used to update agent and viewer connection information
+    // Next setters are used to update agent and viewer connection information
     // upon events like user login, viewer disconnect and user changing region host.
     // These setters are made public to be accessible from newview and should not be
     // used in other cases.
-    static void setAgentID(const LLUUID& id) { sAgentID = id; }
     static void setSessionID(const LLUUID& id) { sSessionID = id; }
     static void setRegionHost(const LLHost& host) { sRegionHost = host; }
     static void setDisconnected(bool disconnected) { sDisconnected = disconnected; }
 
 private:
-    static LLUUID                       sAgentID;
     static LLUUID                       sSessionID;
     static LLHost                       sRegionHost;
     static bool                         sDisconnected;
@@ -486,7 +504,7 @@ public:
     /*virtual*/ std::string getLabel(const std::string &url, const LLUrlLabelCallback &cb);
     /*virtual*/ std::string getUrl(const std::string &string) const;
     /*virtual*/ std::string getTooltip(const std::string &string) const;
-    /*virtual*/ bool underlineOnHoverOnly(const std::string &string) const;
+    LLStyle::EUnderlineLink getUnderline(const std::string& string) const;
 };
 
 ///
@@ -510,7 +528,7 @@ public:
     LLUrlEntryNoLink();
     /*virtual*/ std::string getLabel(const std::string &url, const LLUrlLabelCallback &cb);
     /*virtual*/ std::string getUrl(const std::string &string) const;
-    /*virtual*/ LLStyle::Params getStyle() const;
+    /*virtual*/ LLStyle::Params getStyle(const std::string &url) const;
 };
 
 ///
diff --git a/indra/llui/llurlmatch.cpp b/indra/llui/llurlmatch.cpp
index bfa3b167b1..f093934ca9 100644
--- a/indra/llui/llurlmatch.cpp
+++ b/indra/llui/llurlmatch.cpp
@@ -37,8 +37,9 @@ LLUrlMatch::LLUrlMatch() :
     mIcon(""),
     mMenuName(""),
     mLocation(""),
-    mUnderlineOnHoverOnly(false),
-    mTrusted(false)
+    mUnderline(e_underline::UNDERLINE_ALWAYS),
+    mTrusted(false),
+    mSkipProfileIcon(false)
 {
 }
 
@@ -46,7 +47,7 @@ void LLUrlMatch::setValues(U32 start, U32 end, const std::string &url, const std
                            const std::string& query, const std::string &tooltip,
                            const std::string &icon, const LLStyle::Params& style,
                            const std::string &menu, const std::string &location,
-                           const LLUUID& id, bool underline_on_hover_only, bool trusted)
+                           const LLUUID& id, e_underline underline, bool trusted, bool skip_icon)
 {
     mStart = start;
     mEnd = end;
@@ -60,6 +61,7 @@ void LLUrlMatch::setValues(U32 start, U32 end, const std::string &url, const std
     mMenuName = menu;
     mLocation = location;
     mID = id;
-    mUnderlineOnHoverOnly = underline_on_hover_only;
+    mUnderline = underline;
     mTrusted = trusted;
+    mSkipProfileIcon = skip_icon;
 }
diff --git a/indra/llui/llurlmatch.h b/indra/llui/llurlmatch.h
index 887796bb37..418a21f963 100644
--- a/indra/llui/llurlmatch.h
+++ b/indra/llui/llurlmatch.h
@@ -79,18 +79,20 @@ public:
     /// return the SL location that this Url describes, or "" if none.
     std::string getLocation() const { return mLocation; }
 
-    /// Should this link text be underlined only when mouse is hovered over it?
-    bool underlineOnHoverOnly() const { return mUnderlineOnHoverOnly; }
+    typedef LLStyle::EUnderlineLink e_underline;
+    e_underline getUnderline() const { return mUnderline; }
 
     /// Return true if Url is trusted.
     bool isTrusted() const { return mTrusted; }
 
+    bool getSkipProfileIcon() const { return mSkipProfileIcon; }
+
     /// Change the contents of this match object (used by LLUrlRegistry)
     void setValues(U32 start, U32 end, const std::string &url, const std::string &label,
                    const std::string& query, const std::string &tooltip, const std::string &icon,
                    const LLStyle::Params& style, const std::string &menu,
                    const std::string &location, const LLUUID& id,
-                   bool underline_on_hover_only = false, bool trusted = false);
+                   e_underline underline = e_underline::UNDERLINE_ALWAYS, bool trusted = false, bool skip_icon = false);
 
     const LLUUID& getID() const { return mID; }
 private:
@@ -105,8 +107,9 @@ private:
     std::string mLocation;
     LLUUID      mID;
     LLStyle::Params mStyle;
-    bool        mUnderlineOnHoverOnly;
+    e_underline mUnderline;
     bool        mTrusted;
+    bool mSkipProfileIcon;
 };
 
 #endif
diff --git a/indra/llui/llurlregistry.cpp b/indra/llui/llurlregistry.cpp
index cec1ddfc57..02d88c83fb 100644
--- a/indra/llui/llurlregistry.cpp
+++ b/indra/llui/llurlregistry.cpp
@@ -62,6 +62,8 @@ LLUrlRegistry::LLUrlRegistry()
     registerUrl(new LLUrlEntryAgentUserName());
     // LLUrlEntryAgent*Name must appear before LLUrlEntryAgent since
     // LLUrlEntryAgent is a less specific (catchall for agent urls)
+    mUrlEntryAgentMention = new LLUrlEntryAgentMention();
+    registerUrl(mUrlEntryAgentMention);
     registerUrl(new LLUrlEntryAgent());
     registerUrl(new LLUrlEntryChat());
     registerUrl(new LLUrlEntryGroup());
@@ -155,7 +157,7 @@ static bool stringHasUrl(const std::string &text)
             text.find("@") != std::string::npos);
 }
 
-bool LLUrlRegistry::findUrl(const std::string &text, LLUrlMatch &match, const LLUrlLabelCallback &cb, bool is_content_trusted)
+bool LLUrlRegistry::findUrl(const std::string &text, LLUrlMatch &match, const LLUrlLabelCallback &cb, bool is_content_trusted, bool skip_non_mentions)
 {
     // avoid costly regexes if there is clearly no URL in the text
     if (! stringHasUrl(text))
@@ -176,6 +178,11 @@ bool LLUrlRegistry::findUrl(const std::string &text, LLUrlMatch &match, const LL
             continue;
         }
 
+        if (skip_non_mentions && (mUrlEntryAgentMention != *it))
+        {
+            continue;
+        }
+
         LLUrlEntryBase *url_entry = *it;
 
         U32 start = 0, end = 0;
@@ -233,12 +240,13 @@ bool LLUrlRegistry::findUrl(const std::string &text, LLUrlMatch &match, const LL
                         match_entry->getQuery(url),
                         match_entry->getTooltip(url),
                         match_entry->getIcon(url),
-                        match_entry->getStyle(),
+                        match_entry->getStyle(url),
                         match_entry->getMenuName(),
                         match_entry->getLocation(url),
                         match_entry->getID(url),
-                        match_entry->underlineOnHoverOnly(url),
-                        match_entry->isTrusted());
+                        match_entry->getUnderline(url),
+                        match_entry->isTrusted(),
+                        match_entry->getSkipProfileIcon(url));
         return true;
     }
 
@@ -274,7 +282,9 @@ bool LLUrlRegistry::findUrl(const LLWString &text, LLUrlMatch &match, const LLUr
                         match.getMenuName(),
                         match.getLocation(),
                         match.getID(),
-                        match.underlineOnHoverOnly());
+                        match.getUnderline(),
+                        false,
+                        match.getSkipProfileIcon());
         return true;
     }
     return false;
diff --git a/indra/llui/llurlregistry.h b/indra/llui/llurlregistry.h
index c22af0dbc4..b9502f4592 100644
--- a/indra/llui/llurlregistry.h
+++ b/indra/llui/llurlregistry.h
@@ -75,7 +75,7 @@ public:
     /// your callback is invoked if the matched Url's label changes in the future
     bool findUrl(const std::string &text, LLUrlMatch &match,
                  const LLUrlLabelCallback &cb = &LLUrlRegistryNullCallback,
-                 bool is_content_trusted = false);
+                 bool is_content_trusted = false, bool skip_non_mentions = false);
 
     /// a slightly less efficient version of findUrl for wide strings
     bool findUrl(const LLWString &text, LLUrlMatch &match,
@@ -101,6 +101,7 @@ private:
     LLUrlEntryBase* mUrlEntrySLLabel;
     LLUrlEntryBase* mUrlEntryNoLink;
     LLUrlEntryBase* mUrlEntryKeybinding;
+    LLUrlEntryBase* mUrlEntryAgentMention;
 };
 
 #endif
diff --git a/indra/newview/CMakeLists.txt b/indra/newview/CMakeLists.txt
index fff1597fd9..98151e2f4d 100644
--- a/indra/newview/CMakeLists.txt
+++ b/indra/newview/CMakeLists.txt
@@ -201,6 +201,7 @@ set(viewer_SOURCE_FILES
     llfloatercamera.cpp
     llfloatercamerapresets.cpp
     llfloaterchangeitemthumbnail.cpp
+    llfloaterchatmentionpicker.cpp
     llfloaterchatvoicevolume.cpp
     llfloaterclassified.cpp
     llfloatercolorpicker.cpp
@@ -870,6 +871,7 @@ set(viewer_HEADER_FILES
     llfloaterbuyland.h
     llfloatercamerapresets.h
     llfloaterchangeitemthumbnail.h
+    llfloaterchatmentionpicker.h
     llfloatercamera.h
     llfloaterchatvoicevolume.h
     llfloaterclassified.h
diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index edc70030b4..7e7aa521d3 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -475,7 +475,7 @@ static void deferred_ui_audio_callback(const LLUUID& uuid)
 
 bool    create_text_segment_icon_from_url_match(LLUrlMatch* match,LLTextBase* base)
 {
-    if(!match || !base || base->getPlainText())
+    if (!match || match->getSkipProfileIcon() || !base || base->getPlainText())
         return false;
 
     LLUUID match_id = match->getID();
diff --git a/indra/newview/llavatarlist.cpp b/indra/newview/llavatarlist.cpp
index 8f858fe4e1..f206474e71 100644
--- a/indra/newview/llavatarlist.cpp
+++ b/indra/newview/llavatarlist.cpp
@@ -141,6 +141,7 @@ LLAvatarList::LLAvatarList(const Params& p)
 , mShowSpeakingIndicator(p.show_speaking_indicator)
 , mShowPermissions(p.show_permissions_granted)
 , mShowCompleteName(false)
+, mForceCompleteName(false)
 {
     setCommitOnSelectionChange(true);
 
@@ -177,7 +178,7 @@ void LLAvatarList::setShowIcons(std::string param_name)
 
 std::string LLAvatarList::getAvatarName(LLAvatarName av_name)
 {
-    return mShowCompleteName? av_name.getCompleteName(false) : av_name.getDisplayName();
+    return mShowCompleteName? av_name.getCompleteName(false, mForceCompleteName) : av_name.getDisplayName();
 }
 
 // virtual
@@ -364,7 +365,7 @@ void LLAvatarList::updateAvatarNames()
     for( std::vector<LLPanel*>::const_iterator it = items.begin(); it != items.end(); it++)
     {
         LLAvatarListItem* item = static_cast<LLAvatarListItem*>(*it);
-        item->setShowCompleteName(mShowCompleteName);
+        item->setShowCompleteName(mShowCompleteName, mForceCompleteName);
         item->updateAvatarName();
     }
     mNeedUpdateNames = false;
@@ -404,6 +405,11 @@ boost::signals2::connection LLAvatarList::setItemDoubleClickCallback(const mouse
     return mItemDoubleClickSignal.connect(cb);
 }
 
+boost::signals2::connection LLAvatarList::setItemClickedCallback(const mouse_signal_t::slot_type& cb)
+{
+    return mItemClickedSignal.connect(cb);
+}
+
 //virtual
 S32 LLAvatarList::notifyParent(const LLSD& info)
 {
@@ -418,7 +424,7 @@ S32 LLAvatarList::notifyParent(const LLSD& info)
 void LLAvatarList::addNewItem(const LLUUID& id, const std::string& name, bool is_online, EAddPosition pos)
 {
     LLAvatarListItem* item = new LLAvatarListItem();
-    item->setShowCompleteName(mShowCompleteName);
+    item->setShowCompleteName(mShowCompleteName, mForceCompleteName);
     // This sets the name as a side effect
     item->setAvatarId(id, mSessionID, mIgnoreOnlineStatus);
     item->setOnline(mIgnoreOnlineStatus ? true : is_online);
@@ -432,6 +438,7 @@ void LLAvatarList::addNewItem(const LLUUID& id, const std::string& name, bool is
 
 
     item->setDoubleClickCallback(boost::bind(&LLAvatarList::onItemDoubleClicked, this, _1, _2, _3, _4));
+    item->setMouseDownCallback(boost::bind(&LLAvatarList::onItemClicked, this, _1, _2, _3, _4));
 
     addItem(item, id, pos);
 }
@@ -550,6 +557,11 @@ void LLAvatarList::onItemDoubleClicked(LLUICtrl* ctrl, S32 x, S32 y, MASK mask)
     mItemDoubleClickSignal(ctrl, x, y, mask);
 }
 
+void LLAvatarList::onItemClicked(LLUICtrl* ctrl, S32 x, S32 y, MASK mask)
+{
+    mItemClickedSignal(ctrl, x, y, mask);
+}
+
 bool LLAvatarItemComparator::compare(const LLPanel* item1, const LLPanel* item2) const
 {
     const LLAvatarListItem* avatar_item1 = dynamic_cast<const LLAvatarListItem*>(item1);
diff --git a/indra/newview/llavatarlist.h b/indra/newview/llavatarlist.h
index af5bfefcde..f99da93a3d 100644
--- a/indra/newview/llavatarlist.h
+++ b/indra/newview/llavatarlist.h
@@ -96,11 +96,13 @@ public:
 
     boost::signals2::connection setItemDoubleClickCallback(const mouse_signal_t::slot_type& cb);
 
+    boost::signals2::connection setItemClickedCallback(const mouse_signal_t::slot_type& cb);
+
     virtual S32 notifyParent(const LLSD& info);
 
     void handleDisplayNamesOptionChanged();
 
-    void setShowCompleteName(bool show) { mShowCompleteName = show;};
+    void setShowCompleteName(bool show, bool force = false) { mShowCompleteName = show; mForceCompleteName = force; };
 
 protected:
     void refresh();
@@ -113,6 +115,7 @@ protected:
     void updateLastInteractionTimes();
     void rebuildNames();
     void onItemDoubleClicked(LLUICtrl* ctrl, S32 x, S32 y, MASK mask);
+    void onItemClicked(LLUICtrl* ctrl, S32 x, S32 y, MASK mask);
     void updateAvatarNames();
 
 private:
@@ -127,6 +130,7 @@ private:
     bool mShowSpeakingIndicator;
     bool mShowPermissions;
     bool mShowCompleteName;
+    bool mForceCompleteName;
 
     LLTimer*                mLITUpdateTimer; // last interaction time update timer
     std::string             mIconParamName;
@@ -138,6 +142,7 @@ private:
 
     commit_signal_t mRefreshCompleteSignal;
     mouse_signal_t mItemDoubleClickSignal;
+    mouse_signal_t mItemClickedSignal;
 };
 
 /** Abstract comparator for avatar items */
diff --git a/indra/newview/llavatarlistitem.cpp b/indra/newview/llavatarlistitem.cpp
index 880910d18e..6ef45ed160 100644
--- a/indra/newview/llavatarlistitem.cpp
+++ b/indra/newview/llavatarlistitem.cpp
@@ -78,6 +78,7 @@ LLAvatarListItem::LLAvatarListItem(bool not_from_ui_factory/* = true*/)
     mShowProfileBtn(true),
     mShowPermissions(false),
     mShowCompleteName(false),
+    mForceCompleteName(false),
     mHovered(false),
     mAvatarNameCacheConnection(),
     mGreyOutUsername("")
@@ -324,13 +325,11 @@ void LLAvatarListItem::setShowProfileBtn(bool show)
 
 void LLAvatarListItem::showSpeakingIndicator(bool visible)
 {
-    // Already done? Then do nothing.
-    if (mSpeakingIndicator->getVisible() == (bool)visible)
-        return;
-// Disabled to not contradict with SpeakingIndicatorManager functionality. EXT-3976
-// probably this method should be totally removed.
-//  mSpeakingIndicator->setVisible(visible);
-//  updateChildren();
+    if (mSpeakingIndicator)
+    {
+        mSpeakingIndicator->setIsActiveChannel(visible);
+        mSpeakingIndicator->setShowParticipantsSpeaking(visible);
+    }
 }
 
 void LLAvatarListItem::setAvatarIconVisible(bool visible)
@@ -417,8 +416,8 @@ void LLAvatarListItem::onAvatarNameCache(const LLAvatarName& av_name)
     mAvatarNameCacheConnection.disconnect();
 
     mGreyOutUsername = "";
-    std::string name_string = mShowCompleteName? av_name.getCompleteName(false) : av_name.getDisplayName();
-    if(av_name.getCompleteName() != av_name.getUserName())
+    std::string name_string = mShowCompleteName? av_name.getCompleteName(false, mForceCompleteName) : av_name.getDisplayName();
+    if(av_name.getCompleteName(false, mForceCompleteName) != av_name.getUserName())
     {
         mGreyOutUsername = "[ " + av_name.getUserName(true) + " ]";
         LLStringUtil::toLower(mGreyOutUsername);
diff --git a/indra/newview/llavatarlistitem.h b/indra/newview/llavatarlistitem.h
index 2e4c597d30..2ec7a41055 100644
--- a/indra/newview/llavatarlistitem.h
+++ b/indra/newview/llavatarlistitem.h
@@ -106,7 +106,7 @@ public:
     void setShowPermissions(bool show) { mShowPermissions = show; };
     void showLastInteractionTime(bool show);
     void setAvatarIconVisible(bool visible);
-    void setShowCompleteName(bool show) { mShowCompleteName = show;};
+    void setShowCompleteName(bool show, bool force = false) { mShowCompleteName = show; mForceCompleteName = force;};
 
     const LLUUID& getAvatarId() const;
     std::string getAvatarName() const;
@@ -220,6 +220,7 @@ private:
     bool mHovered;
 
     bool mShowCompleteName;
+    bool mForceCompleteName;
     std::string mGreyOutUsername;
 
     void fetchAvatarName();
diff --git a/indra/newview/llfloaterchatmentionpicker.cpp b/indra/newview/llfloaterchatmentionpicker.cpp
new file mode 100644
index 0000000000..1cfed122a9
--- /dev/null
+++ b/indra/newview/llfloaterchatmentionpicker.cpp
@@ -0,0 +1,184 @@
+/**
+ * @file llfloaterchatmentionpicker.cpp
+ *
+ * $LicenseInfo:firstyear=2025&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2025, 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 "llviewerprecompiledheaders.h"
+
+#include "llfloaterchatmentionpicker.h"
+
+#include "llavatarlist.h"
+#include "llfloaterimcontainer.h"
+#include "llchatmentionhelper.h"
+#include "llparticipantlist.h"
+
+LLUUID LLFloaterChatMentionPicker::sSessionID(LLUUID::null);
+
+LLFloaterChatMentionPicker::LLFloaterChatMentionPicker(const LLSD& key)
+: LLFloater(key), mAvatarList(NULL)
+{
+    // This floater should hover on top of our dependent (with the dependent having the focus)
+    setFocusStealsFrontmost(false);
+    setBackgroundVisible(false);
+    setAutoFocus(false);
+}
+
+bool LLFloaterChatMentionPicker::postBuild()
+{
+    mAvatarList = getChild<LLAvatarList>("avatar_list");
+    mAvatarList->setShowCompleteName(true, true);
+    mAvatarList->setFocusOnItemClicked(false);
+    mAvatarList->setItemClickedCallback([this](LLUICtrl* ctrl, S32 x, S32 y, MASK mask)
+    {
+        if (LLAvatarListItem* item = dynamic_cast<LLAvatarListItem*>(ctrl))
+        {
+            selectResident(item->getAvatarId());
+        }
+    });
+    mAvatarList->setRefreshCompleteCallback([this](LLUICtrl* ctrl, const LLSD& param)
+    {
+        if (mAvatarList->numSelected() == 0)
+        {
+            mAvatarList->selectFirstItem();
+        }
+    });
+
+    return LLFloater::postBuild();
+}
+
+void LLFloaterChatMentionPicker::onOpen(const LLSD& key)
+{
+    buildAvatarList();
+    mAvatarList->setNameFilter(key.has("av_name") ? key["av_name"].asString() : "");
+
+    gFloaterView->adjustToFitScreen(this, false);
+}
+
+uuid_vec_t LLFloaterChatMentionPicker::getParticipantIds()
+{
+    LLParticipantList* item = dynamic_cast<LLParticipantList*>(LLFloaterIMContainer::getInstance()->getSessionModel(sSessionID));
+    if (!item)
+    {
+        LL_WARNS() << "Participant list is missing" << LL_ENDL;
+        return {};
+    }
+
+    uuid_vec_t avatar_ids;
+    LLFolderViewModelItemCommon::child_list_t::const_iterator current_participant_model = item->getChildrenBegin();
+    LLFolderViewModelItemCommon::child_list_t::const_iterator end_participant_model = item->getChildrenEnd();
+    while (current_participant_model != end_participant_model)
+    {
+        LLConversationItem* participant_model = dynamic_cast<LLConversationItem*>(*current_participant_model);
+        if (participant_model)
+        {
+            avatar_ids.push_back(participant_model->getUUID());
+        }
+        current_participant_model++;
+    }
+    return avatar_ids;
+}
+
+void LLFloaterChatMentionPicker::buildAvatarList()
+{
+    uuid_vec_t& avatar_ids = mAvatarList->getIDs();
+    avatar_ids = getParticipantIds();
+    updateAvatarList(avatar_ids);
+    mAvatarList->setDirty();
+}
+
+void LLFloaterChatMentionPicker::selectResident(const LLUUID& id)
+{
+    if (id.isNull())
+        return;
+
+    setValue(stringize("secondlife:///app/agent/", id.asString(), "/mention "));
+    onCommit();
+    LLChatMentionHelper::instance().hideHelper();
+}
+
+void LLFloaterChatMentionPicker::onClose(bool app_quitting)
+{
+    if (!app_quitting)
+    {
+        LLChatMentionHelper::instance().hideHelper();
+    }
+}
+
+bool LLFloaterChatMentionPicker::handleKey(KEY key, MASK mask, bool called_from_parent)
+{
+    if (mask == MASK_NONE)
+    {
+        switch (key)
+        {
+            case KEY_UP:
+            case KEY_DOWN:
+                return mAvatarList->handleKey(key, mask, called_from_parent);
+            case KEY_RETURN:
+            case KEY_TAB:
+                selectResident(mAvatarList->getSelectedUUID());
+                return true;
+            case KEY_ESCAPE:
+                LLChatMentionHelper::instance().hideHelper();
+                return true;
+            case KEY_LEFT:
+            case KEY_RIGHT:
+                return true;
+            default:
+                break;
+        }
+    }
+    return LLFloater::handleKey(key, mask, called_from_parent);
+}
+
+void LLFloaterChatMentionPicker::goneFromFront()
+{
+    LLChatMentionHelper::instance().hideHelper();
+}
+
+void LLFloaterChatMentionPicker::updateSessionID(LLUUID session_id)
+{
+    sSessionID = session_id;
+
+    LLParticipantList* item = dynamic_cast<LLParticipantList*>(LLFloaterIMContainer::getInstance()->getSessionModel(sSessionID));
+    if (!item)
+    {
+        LL_WARNS() << "Participant list is missing" << LL_ENDL;
+        return;
+    }
+
+    uuid_vec_t avatar_ids = getParticipantIds();
+    updateAvatarList(avatar_ids);
+}
+
+void LLFloaterChatMentionPicker::updateAvatarList(uuid_vec_t& avatar_ids)
+{
+    std::vector<std::string> av_names;
+    for (auto& id : avatar_ids)
+    {
+        LLAvatarName av_name;
+        LLAvatarNameCache::get(id, &av_name);
+        av_names.push_back(utf8str_tolower(av_name.getAccountName()));
+        av_names.push_back(utf8str_tolower(av_name.getDisplayName()));
+    }
+    LLChatMentionHelper::instance().updateAvatarList(av_names);
+}
diff --git a/indra/newview/llfloaterchatmentionpicker.h b/indra/newview/llfloaterchatmentionpicker.h
new file mode 100644
index 0000000000..8d221d7a89
--- /dev/null
+++ b/indra/newview/llfloaterchatmentionpicker.h
@@ -0,0 +1,58 @@
+/**
+ * @file llfloaterchatmentionpicker.h
+ *
+ * $LicenseInfo:firstyear=2025&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2025, 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
+ * $/LicenseInfo$
+ */
+
+#ifndef LLFLOATERCHATMENTIONPICKER_H
+#define LLFLOATERCHATMENTIONPICKER_H
+
+#include "llfloater.h"
+
+class LLAvatarList;
+
+class LLFloaterChatMentionPicker : public LLFloater
+{
+public:
+    LLFloaterChatMentionPicker(const LLSD& key);
+
+    virtual bool postBuild() override;
+    virtual void goneFromFront() override;
+
+    void buildAvatarList();
+
+    static uuid_vec_t getParticipantIds();
+    static void updateSessionID(LLUUID session_id);
+    static void updateAvatarList(uuid_vec_t& avatar_ids);
+
+private:
+
+    void onOpen(const LLSD& key) override;
+    void onClose(bool app_quitting) override;
+    virtual bool handleKey(KEY key, MASK mask, bool called_from_parent) override;
+    void selectResident(const LLUUID& id);
+
+    static LLUUID sSessionID;
+    LLAvatarList* mAvatarList;
+};
+
+#endif
diff --git a/indra/newview/llfloaterimnearbychat.cpp b/indra/newview/llfloaterimnearbychat.cpp
index db6f9ac22a..b649514bff 100644
--- a/indra/newview/llfloaterimnearbychat.cpp
+++ b/indra/newview/llfloaterimnearbychat.cpp
@@ -586,7 +586,7 @@ void LLFloaterIMNearbyChat::sendChat( EChatType type )
 {
     if (mInputEditor)
     {
-        LLWString text = mInputEditor->getWText();
+        LLWString text = mInputEditor->getConvertedText();
         LLWStringUtil::trim(text);
         LLWStringUtil::replaceChar(text,182,'\n'); // Convert paragraph symbols back into newlines.
         if (!text.empty())
diff --git a/indra/newview/llfloaterimsession.cpp b/indra/newview/llfloaterimsession.cpp
index 185274981b..84a9fad708 100644
--- a/indra/newview/llfloaterimsession.cpp
+++ b/indra/newview/llfloaterimsession.cpp
@@ -251,7 +251,7 @@ void LLFloaterIMSession::sendMsgFromInputEditor()
     {
         if (mInputEditor)
         {
-            LLWString text = mInputEditor->getWText();
+            LLWString text = mInputEditor->getConvertedText();
             LLWStringUtil::trim(text);
             LLWStringUtil::replaceChar(text,182,'\n'); // Convert paragraph symbols back into newlines.
             if(!text.empty())
diff --git a/indra/newview/llfloaterimsessiontab.cpp b/indra/newview/llfloaterimsessiontab.cpp
index 50e765c236..96aac8c1e6 100644
--- a/indra/newview/llfloaterimsessiontab.cpp
+++ b/indra/newview/llfloaterimsessiontab.cpp
@@ -35,6 +35,7 @@
 #include "llavatariconctrl.h"
 #include "llchatentry.h"
 #include "llchathistory.h"
+#include "llfloaterchatmentionpicker.h"
 #include "llchiclet.h"
 #include "llchicletbar.h"
 #include "lldraghandle.h"
@@ -485,6 +486,7 @@ void LLFloaterIMSessionTab::onFocusReceived()
         LLIMModel::instance().sendNoUnreadMessages(mSessionID);
     }
 
+    LLFloaterChatMentionPicker::updateSessionID(mSessionID);
     super::onFocusReceived();
 }
 
diff --git a/indra/newview/llpanelprofile.cpp b/indra/newview/llpanelprofile.cpp
index 08605f7cf4..c81746a48a 100644
--- a/indra/newview/llpanelprofile.cpp
+++ b/indra/newview/llpanelprofile.cpp
@@ -328,7 +328,7 @@ public:
         }
 
         const std::string verb = params[1].asString();
-        if (verb == "about")
+        if (verb == "about" || verb == "mention")
         {
             LLAvatarActions::showProfile(avatar_id);
             return true;
diff --git a/indra/newview/llstartup.cpp b/indra/newview/llstartup.cpp
index 3973036cc6..4f60f98b49 100644
--- a/indra/newview/llstartup.cpp
+++ b/indra/newview/llstartup.cpp
@@ -3566,7 +3566,7 @@ bool process_login_success_response()
 
     // Agent id needed for parcel info request in LLUrlEntryParcel
     // to resolve parcel name.
-    LLUrlEntryParcel::setAgentID(gAgentID);
+    LLUrlEntryBase::setAgentID(gAgentID);
 
     text = response["session_id"].asString();
     if(!text.empty()) gAgentSessionID.set(text);
diff --git a/indra/newview/llviewerchat.cpp b/indra/newview/llviewerchat.cpp
index 8b01c4ef88..2ca2c5c07d 100644
--- a/indra/newview/llviewerchat.cpp
+++ b/indra/newview/llviewerchat.cpp
@@ -36,6 +36,7 @@
 #include "llviewerregion.h"
 #include "llworld.h"
 #include "llinstantmessage.h" //SYSTEM_FROM
+#include "llurlregistry.h"
 
 // LLViewerChat
 LLViewerChat::font_change_signal_t LLViewerChat::sChatFontChangedSignal;
@@ -222,6 +223,13 @@ void LLViewerChat::formatChatMsg(const LLChat& chat, std::string& formated_msg)
 {
     std::string tmpmsg = chat.mText;
 
+    // show @name instead of slurl for chat mentions
+    LLUrlMatch match;
+    while (LLUrlRegistry::instance().findUrl(tmpmsg, match, LLUrlRegistryNullCallback, false, true))
+    {
+        tmpmsg.replace(match.getStart(), match.getEnd() - match.getStart() + 1, match.getLabel());
+    }
+
     if(chat.mChatStyle == CHAT_STYLE_IRC)
     {
         formated_msg = chat.mFromName + tmpmsg.substr(3);
diff --git a/indra/newview/llviewerfloaterreg.cpp b/indra/newview/llviewerfloaterreg.cpp
index 95c2a77ba8..4d9c2f3281 100644
--- a/indra/newview/llviewerfloaterreg.cpp
+++ b/indra/newview/llviewerfloaterreg.cpp
@@ -58,6 +58,7 @@
 #include "llfloatercamera.h"
 #include "llfloatercamerapresets.h"
 #include "llfloaterchangeitemthumbnail.h"
+#include "llfloaterchatmentionpicker.h"
 #include "llfloaterchatvoicevolume.h"
 #include "llfloaterclassified.h"
 #include "llfloaterconversationlog.h"
@@ -353,6 +354,7 @@ void LLViewerFloaterReg::registerFloaters()
     LLFloaterReg::add("chat_voice", "floater_voice_chat_volume.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterChatVoiceVolume>);
     LLFloaterReg::add("change_item_thumbnail", "floater_change_item_thumbnail.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterChangeItemThumbnail>);
     LLFloaterReg::add("nearby_chat", "floater_im_session.xml", (LLFloaterBuildFunc)&LLFloaterIMNearbyChat::buildFloater);
+    LLFloaterReg::add("chat_mention_picker", "floater_chat_mention_picker.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterChatMentionPicker>);
     LLFloaterReg::add("classified", "floater_classified.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterClassified>);
     LLFloaterReg::add("compile_queue", "floater_script_queue.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterCompileQueue>);
     LLFloaterReg::add("conversation", "floater_conversation_log.xml", (LLFloaterBuildFunc)&LLFloaterReg::build<LLFloaterConversationLog>);
diff --git a/indra/newview/skins/default/colors.xml b/indra/newview/skins/default/colors.xml
index f0af4acf20..cb190d3d34 100644
--- a/indra/newview/skins/default/colors.xml
+++ b/indra/newview/skins/default/colors.xml
@@ -1000,4 +1000,10 @@
   <color
     name="OutfitSnapshotMacMask2"
     value="0.1 0.1 0.1 1"/>
+  <color
+    name="ChatMentionHighlight"
+    value="0.82 0.91 0.98 0.15" />
+  <color
+    name="ChatSelfMentionHighlight"
+    value="0.85 0.75 0.40 0.5" />
 </colors>
diff --git a/indra/newview/skins/default/xui/en/floater_chat_mention_picker.xml b/indra/newview/skins/default/xui/en/floater_chat_mention_picker.xml
new file mode 100644
index 0000000000..bbad99f932
--- /dev/null
+++ b/indra/newview/skins/default/xui/en/floater_chat_mention_picker.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
+<floater
+    name="chat_mention_picker"
+    title="CHOOSE RESIDENT"
+    single_instance="true"
+    can_minimize="false"
+    can_tear_off="false"
+    can_resize="true"
+    auto_close="true"
+    layout="topleft"
+    min_width="250"
+    chrome="true"
+    height="125"
+    width="310">
+   <avatar_list
+    allow_select="true"
+    follows="all"
+    height="120"
+    width="306"
+    ignore_online_status="true"
+    layout="topleft"
+    left="3"
+    keep_one_selected="true"
+    multi_select="false"
+    show_info_btn="false"
+    show_profile_btn="false"
+    show_speaking_indicator="false"
+    name="avatar_list"
+    right="-1"
+    top="2" />
+</floater>