diff --git a/crates/action_log/src/action_log.rs b/crates/action_log/src/action_log.rs
index 0471ae45dd8..99cc0a2d79b 100644
--- a/crates/action_log/src/action_log.rs
+++ b/crates/action_log/src/action_log.rs
@@ -936,7 +936,11 @@ impl ActionLog {
         let mut undo_buffers = Vec::new();
         let mut futures = Vec::new();
 
-        for buffer in self.changed_buffers(cx).into_keys() {
+        for buffer in self
+            .changed_buffers(cx)
+            .map(|(buffer, _)| buffer)
+            .collect::<Vec<_>>()
+        {
             let buffer_ranges = vec![Anchor::min_max_range_for_buffer(
                 buffer.read(cx).remote_id(),
             )];
@@ -1023,17 +1027,19 @@ impl ActionLog {
     }
 
     /// Returns the set of buffers that contain edits that haven't been reviewed by the user.
-    pub fn changed_buffers(&self, cx: &App) -> BTreeMap<Entity<Buffer>, Entity<BufferDiff>> {
+    pub fn changed_buffers(
+        &self,
+        cx: &App,
+    ) -> impl Iterator<Item = (Entity<Buffer>, Entity<BufferDiff>)> {
         self.tracked_buffers
             .iter()
             .filter(|(_, tracked)| tracked.has_edits(cx))
             .map(|(buffer, tracked)| (buffer.clone(), tracked.diff.clone()))
-            .collect()
     }
 
     /// Returns the total number of lines added and removed across all unreviewed buffers.
     pub fn diff_stats(&self, cx: &App) -> DiffStats {
-        DiffStats::all_files(&self.changed_buffers(cx), cx)
+        DiffStats::all_files(self.changed_buffers(cx), cx)
     }
 
     /// Iterate over buffers changed since last read or edited by the model
@@ -1079,7 +1085,7 @@ impl DiffStats {
     }
 
     pub fn all_files(
-        changed_buffers: &BTreeMap<Entity<Buffer>, Entity<BufferDiff>>,
+        changed_buffers: impl IntoIterator<Item = (Entity<Buffer>, Entity<BufferDiff>)>,
         cx: &App,
     ) -> Self {
         let mut total = DiffStats::default();
@@ -3254,21 +3260,21 @@ mod tests {
             child_log_1
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
         let child_2_changed: Vec<_> = cx.read(|cx| {
             child_log_2
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
         let parent_changed: Vec<_> = cx.read(|cx| {
             parent_log
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
 
@@ -3494,7 +3500,6 @@ mod tests {
             action_log
                 .read(cx)
                 .changed_buffers(cx)
-                .into_iter()
                 .map(|(buffer, diff)| {
                     let snapshot = buffer.read(cx).snapshot();
                     (
diff --git a/crates/agent/src/tools/edit_file_tool.rs b/crates/agent/src/tools/edit_file_tool.rs
index 82c6463dd11..2801c8878d1 100644
--- a/crates/agent/src/tools/edit_file_tool.rs
+++ b/crates/agent/src/tools/edit_file_tool.rs
@@ -2608,7 +2608,8 @@ mod tests {
 
         cx.run_until_parked();
 
-        let changed = action_log.read_with(cx, |log, cx| log.changed_buffers(cx));
+        let changed =
+            action_log.read_with(cx, |log, cx| log.changed_buffers(cx).collect::<Vec<_>>());
         assert!(
             !changed.is_empty(),
             "action_log.changed_buffers() should be non-empty after streaming edit,
diff --git a/crates/agent/src/tools/write_file_tool.rs b/crates/agent/src/tools/write_file_tool.rs
index 89942c316ce..735a9d23a91 100644
--- a/crates/agent/src/tools/write_file_tool.rs
+++ b/crates/agent/src/tools/write_file_tool.rs
@@ -1061,7 +1061,8 @@ mod tests {
 
         cx.run_until_parked();
 
-        let changed = action_log.read_with(cx, |log, cx| log.changed_buffers(cx));
+        let changed =
+            action_log.read_with(cx, |log, cx| log.changed_buffers(cx).collect::<Vec<_>>());
         assert!(
             !changed.is_empty(),
             "action_log.changed_buffers() should be non-empty after streaming write, \
@@ -1133,7 +1134,8 @@ mod tests {
         );
 
         // Reject all edits — this should delete the newly created file
-        let changed = action_log.read_with(cx, |log, cx| log.changed_buffers(cx));
+        let changed =
+            action_log.read_with(cx, |log, cx| log.changed_buffers(cx).collect::<Vec<_>>());
         assert!(
             !changed.is_empty(),
             "action_log should track the created file as changed"
diff --git a/crates/agent_ui/src/agent_diff.rs b/crates/agent_ui/src/agent_diff.rs
index 95a9191ef85..9a820db7b20 100644
--- a/crates/agent_ui/src/agent_diff.rs
+++ b/crates/agent_ui/src/agent_diff.rs
@@ -138,7 +138,7 @@ impl AgentDiffPane {
             .changed_buffers(cx);
 
         // Sort edited files alphabetically for consistency with Git diff view
-        let mut sorted_buffers: Vec<_> = changed_buffers.iter().collect();
+        let mut sorted_buffers: Vec<_> = changed_buffers.collect();
         sorted_buffers.sort_by(|(buffer_a, _), (buffer_b, _)| {
             let path_a = buffer_a.read(cx).file().map(|f| f.path().clone());
             let path_b = buffer_b.read(cx).file().map(|f| f.path().clone());
@@ -1535,7 +1535,7 @@ impl AgentDiff {
         };
 
         let action_log = thread.read(cx).action_log();
-        let changed_buffers = action_log.read(cx).changed_buffers(cx);
+        let changed_buffers = action_log.read(cx).changed_buffers(cx).collect::<Vec<_>>();
 
         let mut unaffected = self.reviewing_editors.clone();
 
@@ -1769,12 +1769,13 @@ impl AgentDiff {
         {
             let changed_buffers = thread.read(cx).action_log().read(cx).changed_buffers(cx);
 
-            let mut keys = changed_buffers.keys();
-            keys.find(|k| *k == &curr_buffer);
+            let mut keys = changed_buffers.map(|(buffer, _)| buffer);
+            keys.find(|k| *k == curr_buffer);
             let next_project_path = keys
                 .next()
-                .filter(|k| *k != &curr_buffer)
+                .filter(|k| *k != curr_buffer)
                 .and_then(|after| after.read(cx).project_path(cx));
+            drop(keys);
 
             if let Some(path) = next_project_path {
                 let task = workspace.open_path(path, None, true, window, cx);
diff --git a/crates/agent_ui/src/conversation_view.rs b/crates/agent_ui/src/conversation_view.rs
index fc266cbed42..c1646179483 100644
--- a/crates/agent_ui/src/conversation_view.rs
+++ b/crates/agent_ui/src/conversation_view.rs
@@ -53,7 +53,7 @@ use std::num::NonZeroUsize;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::Instant;
-use std::{collections::BTreeMap, rc::Rc, time::Duration};
+use std::{rc::Rc, time::Duration};
 use terminal_view::terminal_panel::TerminalPanel;
 use text::Anchor;
 use theme_settings::{AgentBufferFontSize, AgentUiFontSize};
diff --git a/crates/agent_ui/src/conversation_view/thread_view.rs b/crates/agent_ui/src/conversation_view/thread_view.rs
index c4416f06d7a..857ef88dbc3 100644
--- a/crates/agent_ui/src/conversation_view/thread_view.rs
+++ b/crates/agent_ui/src/conversation_view/thread_view.rs
@@ -2310,7 +2310,7 @@ impl ThreadView {
         let thread = &self.thread;
         let telemetry = ActionLogTelemetry::from(thread.read(cx));
         let action_log = thread.read(cx).action_log().clone();
-        let has_changes = action_log.read(cx).changed_buffers(cx).len() > 0;
+        let has_changes = action_log.read(cx).changed_buffers(cx).next().is_some();
 
         action_log
             .update(cx, |action_log, cx| {
@@ -2580,7 +2580,7 @@ impl ThreadView {
         let thread = self.thread.read(cx);
         let action_log = thread.action_log();
         let telemetry = ActionLogTelemetry::from(thread);
-        let changed_buffers = action_log.read(cx).changed_buffers(cx);
+        let changed_buffers = action_log.read(cx).changed_buffers(cx).collect::<Vec<_>>();
         let plan = thread.plan();
         let queue_is_empty = !self.has_queued_messages();
 
@@ -2686,7 +2686,7 @@ impl ThreadView {
         &self,
         action_log: &Entity<ActionLog>,
         telemetry: ActionLogTelemetry,
-        changed_buffers: &BTreeMap<Entity<Buffer>, Entity<BufferDiff>>,
+        changed_buffers: &[(Entity<Buffer>, Entity<BufferDiff>)],
         pending_edits: bool,
         cx: &Context<Self>,
     ) -> impl IntoElement {
@@ -3433,7 +3433,7 @@ impl ThreadView {
 
     fn render_edits_summary(
         &self,
-        changed_buffers: &BTreeMap<Entity<Buffer>, Entity<BufferDiff>>,
+        changed_buffers: &[(Entity<Buffer>, Entity<BufferDiff>)],
         expanded: bool,
         pending_edits: bool,
         cx: &Context<Self>,
@@ -3478,7 +3478,7 @@ impl ThreadView {
                                 ),
                             )
                         } else {
-                            let stats = DiffStats::all_files(changed_buffers, cx);
+                            let stats = DiffStats::all_files(changed_buffers.iter().cloned(), cx);
                             let dot_divider = || {
                                 Label::new("•")
                                     .size(LabelSize::XSmall)
@@ -8391,7 +8391,7 @@ impl ThreadView {
             .map(|thread| thread.read(cx).session_id().clone());
         let action_log = thread.as_ref().map(|thread| thread.read(cx).action_log());
         let changed_buffers = action_log
-            .map(|log| log.read(cx).changed_buffers(cx))
+            .map(|log| log.read(cx).changed_buffers(cx).collect::<Vec<_>>())
             .unwrap_or_default();
 
         let is_pending_tool_call = thread_view
@@ -8404,7 +8404,7 @@ impl ThreadView {
 
         let is_expanded = self.expanded_tool_calls.contains(&tool_call.id);
         let files_changed = changed_buffers.len();
-        let diff_stats = DiffStats::all_files(&changed_buffers, cx);
+        let diff_stats = DiffStats::all_files(changed_buffers, cx);
 
         let is_running = matches!(
             tool_call.status,
diff --git a/crates/gpui/src/text_system.rs b/crates/gpui/src/text_system.rs
index bebe180b262..043d37f679b 100644
--- a/crates/gpui/src/text_system.rs
+++ b/crates/gpui/src/text_system.rs
@@ -234,12 +234,6 @@ impl TextSystem {
         Ok(self.advance(font_id, font_size, 'm')?.width)
     }
 
-    // Consider removing this?
-    /// Returns the shaped layout width of an `em`.
-    pub fn em_layout_width(&self, font_id: FontId, font_size: Pixels) -> Pixels {
-        self.layout_width(font_id, font_size, 'm')
-    }
-
     /// Returns the width of an `ch`.
     ///
     /// Uses the width of the `0` character in the given font and size.
@@ -699,6 +693,28 @@ impl WindowTextSystem {
         layout
     }
 
+    /// Returns the shaped layout width of for the given character, in the given font and size.
+    pub fn layout_width(&self, font_id: FontId, font_size: Pixels, ch: char) -> Pixels {
+        let mut buffer = [0; 4];
+        let buffer: &_ = ch.encode_utf8(&mut buffer);
+        self.line_layout_cache
+            .layout_line(
+                buffer,
+                font_size,
+                &[FontRun {
+                    len: buffer.len(),
+                    font_id,
+                }],
+                None,
+            )
+            .width
+    }
+
+    /// Returns the shaped layout width of an `em`.
+    pub fn em_layout_width(&self, font_id: FontId, font_size: Pixels) -> Pixels {
+        self.layout_width(font_id, font_size, 'm')
+    }
+
     /// Probe the line layout cache using a caller-provided content hash, without allocating.
     ///
     /// Returns `Some(layout)` if the layout is already cached in either the current frame
diff --git a/crates/sidebar/src/sidebar.rs b/crates/sidebar/src/sidebar.rs
index 948650d0959..81d65e63366 100644
--- a/crates/sidebar/src/sidebar.rs
+++ b/crates/sidebar/src/sidebar.rs
@@ -307,7 +307,7 @@ enum ListEntry {
         is_active: bool,
         has_threads: bool,
     },
-    Thread(ThreadEntry),
+    Thread(Arc<ThreadEntry>),
     Terminal(TerminalEntry),
 }
 
@@ -403,7 +403,7 @@ impl ListEntry {
 
 impl From<ThreadEntry> for ListEntry {
     fn from(thread: ThreadEntry) -> Self {
-        ListEntry::Thread(thread)
+        ListEntry::Thread(Arc::new(thread))
     }
 }
 
@@ -479,24 +479,22 @@ fn linked_worktree_path_lists_for_workspaces(
     workspaces: &[Entity<Workspace>],
     cx: &App,
 ) -> Vec<PathList> {
-    let mut linked_worktree_paths = HashSet::new();
+    let mut linked_worktree_paths = Vec::new();
     for workspace in workspaces {
         if workspace.read(cx).visible_worktrees(cx).count() != 1 {
             continue;
         }
         for snapshot in root_repository_snapshots(workspace, cx) {
-            for linked_worktree in snapshot.linked_worktrees() {
-                linked_worktree_paths.insert(linked_worktree.path.clone());
-            }
+            linked_worktree_paths.extend(
+                snapshot.linked_worktrees().iter().map(|linked_worktree| {
+                    PathList::new(std::slice::from_ref(&linked_worktree.path))
+                }),
+            );
         }
     }
 
-    let mut linked_worktree_paths = linked_worktree_paths.into_iter().collect::<Vec<_>>();
-    linked_worktree_paths.sort();
+    linked_worktree_paths.sort_by(|a, b| a.paths()[0].cmp(&b.paths()[0]));
     linked_worktree_paths
-        .into_iter()
-        .map(|path| PathList::new(std::slice::from_ref(&path)))
-        .collect()
 }
 
 fn workspace_has_terminal_metadata_except(
@@ -1439,12 +1437,11 @@ impl Sidebar {
                 .is_some_and(|active| group_workspaces.contains(active));
 
             // Collect live thread infos from all workspaces in this group.
-            let live_infos: Vec<_> = group_workspaces
+            let live_infos = group_workspaces
                 .iter()
-                .flat_map(|ws| all_thread_infos_for_workspace(ws, cx))
-                .collect();
+                .flat_map(|ws| all_thread_infos_for_workspace(ws, cx));
 
-            let mut threads: Vec<ThreadEntry> = Vec::new();
+            let mut threads: Vec<Arc<ThreadEntry>> = Vec::new();
             let mut has_running_threads = false;
             let mut waiting_thread_count: usize = 0;
             let group_host = group_key.host();
@@ -1461,12 +1458,12 @@ impl Sidebar {
                 let thread_store = ThreadMetadataStore::global(cx);
 
                 let make_thread_entry =
-                    |row: ThreadMetadata, workspace: ThreadEntryWorkspace| -> ThreadEntry {
+                    |row: ThreadMetadata, workspace: ThreadEntryWorkspace| -> Arc<ThreadEntry> {
                         let (icon, icon_from_external_svg) = resolve_agent_icon(&row.agent_id);
                         let worktrees =
                             worktree_info_from_thread_paths(&row.worktree_paths, &branch_by_path);
                         let is_draft = row.is_draft();
-                        ThreadEntry {
+                        Arc::new(ThreadEntry {
                             metadata: row,
                             icon,
                             icon_from_external_svg,
@@ -1479,7 +1476,7 @@ impl Sidebar {
                             highlight_positions: Vec::new(),
                             worktrees,
                             diff_stats: DiffStats::default(),
-                        }
+                        })
                     };
 
                 // Main code path: one query per group via main_worktree_paths.
@@ -1574,7 +1571,7 @@ impl Sidebar {
                     if !thread.is_draft {
                         continue;
                     }
-                    thread.metadata.title = draft_display_label_for_thread_metadata(
+                    Arc::make_mut(thread).metadata.title = draft_display_label_for_thread_metadata(
                         &thread.metadata,
                         &thread.workspace,
                         cx,
@@ -1584,26 +1581,26 @@ impl Sidebar {
 
                 // Build a lookup from live_infos and compute running/waiting
                 // counts in a single pass.
-                let mut live_info_by_session: HashMap<&acp::SessionId, &ActiveThreadInfo> =
+                let mut live_info_by_session: HashMap<acp::SessionId, ActiveThreadInfo> =
                     HashMap::new();
-                for info in &live_infos {
-                    live_info_by_session.insert(&info.session_id, info);
+                for info in live_infos {
                     if info.status == AgentThreadStatus::Running {
                         has_running_threads = true;
                     }
                     if info.status == AgentThreadStatus::WaitingForConfirmation {
                         waiting_thread_count += 1;
                     }
+                    live_info_by_session.insert(info.session_id.clone(), info);
                 }
 
                 // Merge live info into threads and update notification state
                 // in a single pass.
                 for thread in &mut threads {
                     if let Some(session_id) = thread.metadata.session_id.clone() {
-                        if let Some(&info) = live_info_by_session.get(&session_id) {
+                        if let Some(info) = live_info_by_session.get(&session_id) {
                             let status = info.status;
                             let thread_id = thread.metadata.thread_id;
-                            thread.apply_active_info(info);
+                            Arc::make_mut(thread).apply_active_info(info);
                             new_live_statuses.insert(session_id, (status, thread_id));
                         }
                     }
@@ -1637,7 +1634,7 @@ impl Sidebar {
                     b_time.cmp(&a_time)
                 });
             } else {
-                for info in &live_infos {
+                for info in live_infos {
                     if info.status == AgentThreadStatus::Running {
                         has_running_threads = true;
                     }
@@ -1708,20 +1705,23 @@ impl Sidebar {
                     fuzzy_match_positions(&query, &label).unwrap_or_default();
                 let workspace_matched = !workspace_highlight_positions.is_empty();
 
-                let mut matched_threads: Vec<ThreadEntry> = Vec::new();
+                let mut matched_threads: Vec<Arc<ThreadEntry>> = Vec::new();
                 for mut thread in threads {
-                    let title = thread.metadata.display_title();
-                    if let Some(positions) = fuzzy_match_positions(&query, title.as_ref()) {
-                        thread.highlight_positions = positions;
-                    }
                     let mut worktree_matched = false;
-                    for worktree in &mut thread.worktrees {
-                        let Some(name) = worktree.worktree_name.as_ref() else {
-                            continue;
-                        };
-                        if let Some(positions) = fuzzy_match_positions(&query, name) {
-                            worktree.highlight_positions = positions;
-                            worktree_matched = true;
+                    {
+                        let thread = Arc::make_mut(&mut thread);
+                        let title = thread.metadata.display_title();
+                        if let Some(positions) = fuzzy_match_positions(&query, title.as_ref()) {
+                            thread.highlight_positions = positions;
+                        }
+                        for worktree in &mut thread.worktrees {
+                            let Some(name) = worktree.worktree_name.as_ref() else {
+                                continue;
+                            };
+                            if let Some(positions) = fuzzy_match_positions(&query, name) {
+                                worktree.highlight_positions = positions;
+                                worktree_matched = true;
+                            }
                         }
                     }
                     if workspace_matched
@@ -4723,7 +4723,7 @@ impl Sidebar {
                     .as_ref()
                     .map(|workspace| PathList::new(&workspace.read(cx).root_paths(cx)))
             });
-        let thread_entry_workspace = thread_entry.map(|thread| thread.workspace);
+        let thread_entry_workspace = thread_entry.map(|thread| thread.workspace.clone());
 
         if let (
             Some(metadata),
@@ -5229,7 +5229,7 @@ impl Sidebar {
     fn push_entries_by_display_time(
         entries: &mut Vec<ListEntry>,
         terminals: Vec<TerminalEntry>,
-        threads: Vec<ThreadEntry>,
+        threads: Vec<Arc<ThreadEntry>>,
         current_session_ids: &mut HashSet<acp::SessionId>,
         current_thread_ids: &mut HashSet<agent_ui::ThreadId>,
     ) {
diff --git a/crates/sidebar/src/sidebar_tests.rs b/crates/sidebar/src/sidebar_tests.rs
index 97ddea152d1..40cfc62fa39 100644
--- a/crates/sidebar/src/sidebar_tests.rs
+++ b/crates/sidebar/src/sidebar_tests.rs
@@ -1089,7 +1089,7 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 is_active: true,
                 has_threads: true,
             },
-            ListEntry::Thread(ThreadEntry {
+            ListEntry::Thread(Arc::new(ThreadEntry {
                 metadata: ThreadMetadata {
                     thread_id: ThreadId::new(),
                     session_id: Some(acp::SessionId::new(Arc::from("t-1"))),
@@ -1114,9 +1114,9 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 highlight_positions: Vec::new(),
                 worktrees: Vec::new(),
                 diff_stats: DiffStats::default(),
-            }),
+            })),
             // Active thread with Running status
-            ListEntry::Thread(ThreadEntry {
+            ListEntry::Thread(Arc::new(ThreadEntry {
                 metadata: ThreadMetadata {
                     thread_id: ThreadId::new(),
                     session_id: Some(acp::SessionId::new(Arc::from("t-2"))),
@@ -1141,9 +1141,9 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 highlight_positions: Vec::new(),
                 worktrees: Vec::new(),
                 diff_stats: DiffStats::default(),
-            }),
+            })),
             // Active thread with Error status
-            ListEntry::Thread(ThreadEntry {
+            ListEntry::Thread(Arc::new(ThreadEntry {
                 metadata: ThreadMetadata {
                     thread_id: ThreadId::new(),
                     session_id: Some(acp::SessionId::new(Arc::from("t-3"))),
@@ -1168,10 +1168,10 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 highlight_positions: Vec::new(),
                 worktrees: Vec::new(),
                 diff_stats: DiffStats::default(),
-            }),
+            })),
             // Thread with WaitingForConfirmation status, not active
             // remote_connection: None,
-            ListEntry::Thread(ThreadEntry {
+            ListEntry::Thread(Arc::new(ThreadEntry {
                 metadata: ThreadMetadata {
                     thread_id: ThreadId::new(),
                     session_id: Some(acp::SessionId::new(Arc::from("t-4"))),
@@ -1196,10 +1196,10 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 highlight_positions: Vec::new(),
                 worktrees: Vec::new(),
                 diff_stats: DiffStats::default(),
-            }),
+            })),
             // Background thread that completed (should show notification)
             // remote_connection: None,
-            ListEntry::Thread(ThreadEntry {
+            ListEntry::Thread(Arc::new(ThreadEntry {
                 metadata: ThreadMetadata {
                     thread_id: notified_thread_id,
                     session_id: Some(acp::SessionId::new(Arc::from("t-5"))),
@@ -1224,7 +1224,7 @@ async fn test_visible_entries_as_strings(cx: &mut TestAppContext) {
                 highlight_positions: Vec::new(),
                 worktrees: Vec::new(),
                 diff_stats: DiffStats::default(),
-            }),
+            })),
             // Collapsed project header
             ListEntry::ProjectHeader {
                 key: ProjectGroupKey::new(None, collapsed_path.clone()),