agent: Bring title editing back to text threads (#29425)

This also fixes a little UI bug where the text thread title would push
the buttons away from the UI when there was still space.

Release Notes:

- agent: Made text thread titles editable again.

---------

Co-authored-by: Michael Sloan <mgsloan@gmail.com>

crates/assistant_context_editor/src/context.rs

@@ -459,6 +459,7 @@ pub enum ContextEvent {
     ShowMaxMonthlySpendReachedError,
     MessagesEdited,
     SummaryChanged,
+    SummaryGenerated,
     StreamedCompletion,
     StartedThoughtProcess(Range<language::Anchor>),
     EndedThoughtProcess(language::Anchor),
@@ -482,7 +483,7 @@ pub enum ContextEvent {
 #[derive(Clone, Default, Debug)]
 pub struct ContextSummary {
     pub text: String,
-    done: bool,
+    pub done: bool,
     timestamp: clock::Lamport,
 }
 
@@ -640,7 +641,7 @@ pub struct AssistantContext {
     contents: Vec<Content>,
     messages_metadata: HashMap<MessageId, MessageMetadata>,
     summary: Option<ContextSummary>,
-    pending_summary: Task<Option<()>>,
+    summary_task: Task<Option<()>>,
     completion_count: usize,
     pending_completions: Vec<PendingCompletion>,
     token_count: Option<usize>,
@@ -741,7 +742,7 @@ impl AssistantContext {
             thought_process_output_sections: Vec::new(),
             edits_since_last_parse: edits_since_last_slash_command_parse,
             summary: None,
-            pending_summary: Task::ready(None),
+            summary_task: Task::ready(None),
             completion_count: Default::default(),
             pending_completions: Default::default(),
             token_count: None,
@@ -951,7 +952,7 @@ impl AssistantContext {
 
     fn flush_ops(&mut self, cx: &mut Context<AssistantContext>) {
         let mut changed_messages = HashSet::default();
-        let mut summary_changed = false;
+        let mut summary_generated = false;
 
         self.pending_ops.sort_unstable_by_key(|op| op.timestamp());
         for op in mem::take(&mut self.pending_ops) {
@@ -993,7 +994,7 @@ impl AssistantContext {
                         .map_or(true, |summary| new_summary.timestamp > summary.timestamp)
                     {
                         self.summary = Some(new_summary);
-                        summary_changed = true;
+                        summary_generated = true;
                     }
                 }
                 ContextOperation::SlashCommandStarted {
@@ -1072,8 +1073,9 @@ impl AssistantContext {
             cx.notify();
         }
 
-        if summary_changed {
+        if summary_generated {
             cx.emit(ContextEvent::SummaryChanged);
+            cx.emit(ContextEvent::SummaryGenerated);
             cx.notify();
         }
     }
@@ -2947,7 +2949,7 @@ impl AssistantContext {
         self.message_anchors.insert(insertion_ix, new_anchor);
     }
 
-    pub fn summarize(&mut self, replace_old: bool, cx: &mut Context<Self>) {
+    pub fn summarize(&mut self, mut replace_old: bool, cx: &mut Context<Self>) {
         let Some(model) = LanguageModelRegistry::read_global(cx).default_model() else {
             return;
         };
@@ -2967,7 +2969,18 @@ impl AssistantContext {
                 cache: false,
             });
 
-            self.pending_summary = cx.spawn(async move |this, cx| {
+            // If there is no summary, it is set with `done: false` so that "Loading Summary…" can
+            // be displayed.
+            if self.summary.is_none() {
+                self.summary = Some(ContextSummary {
+                    text: "".to_string(),
+                    done: false,
+                    timestamp: clock::Lamport::default(),
+                });
+                replace_old = true;
+            }
+
+            self.summary_task = cx.spawn(async move |this, cx| {
                 async move {
                     let stream = model.model.stream_completion_text(request, &cx);
                     let mut messages = stream.await?;
@@ -2992,6 +3005,7 @@ impl AssistantContext {
                             };
                             this.push_op(operation, cx);
                             cx.emit(ContextEvent::SummaryChanged);
+                            cx.emit(ContextEvent::SummaryGenerated);
                         })?;
 
                         // Stop if the LLM generated multiple lines.
@@ -3012,6 +3026,7 @@ impl AssistantContext {
                             };
                             this.push_op(operation, cx);
                             cx.emit(ContextEvent::SummaryChanged);
+                            cx.emit(ContextEvent::SummaryGenerated);
                         }
                     })?;
 
@@ -3184,7 +3199,7 @@ impl AssistantContext {
         });
     }
 
-    pub fn custom_summary(&mut self, custom_summary: String, cx: &mut Context<Self>) {
+    pub fn set_custom_summary(&mut self, custom_summary: String, cx: &mut Context<Self>) {
         let timestamp = self.next_timestamp();
         let summary = self.summary.get_or_insert(ContextSummary::default());
         summary.timestamp = timestamp;
@@ -3192,6 +3207,15 @@ impl AssistantContext {
         summary.text = custom_summary;
         cx.emit(ContextEvent::SummaryChanged);
     }
+
+    pub const DEFAULT_SUMMARY: SharedString = SharedString::new_static("New Text Thread");
+
+    pub fn summary_or_default(&self) -> SharedString {
+        self.summary
+            .as_ref()
+            .map(|summary| summary.text.clone().into())
+            .unwrap_or(Self::DEFAULT_SUMMARY)
+    }
 }
 
 fn trimmed_text_in_range(buffer: &BufferSnapshot, range: Range<text::Anchor>) -> String {

crates/assistant_context_editor/src/context_editor.rs

@@ -48,7 +48,7 @@ use project::{Project, Worktree};
 use rope::Point;
 use serde::{Deserialize, Serialize};
 use settings::{Settings, SettingsStore, update_settings_file};
-use std::{any::TypeId, borrow::Cow, cmp, ops::Range, path::PathBuf, sync::Arc, time::Duration};
+use std::{any::TypeId, cmp, ops::Range, path::PathBuf, sync::Arc, time::Duration};
 use text::SelectionGoal;
 use ui::{
     ButtonLike, Disclosure, ElevationIndex, KeyBinding, PopoverMenuHandle, TintColor, Tooltip,
@@ -618,6 +618,7 @@ impl ContextEditor {
                     context.save(Some(Duration::from_millis(500)), self.fs.clone(), cx);
                 });
             }
+            ContextEvent::SummaryGenerated => {}
             ContextEvent::StartedThoughtProcess(range) => {
                 let creases = self.insert_thought_process_output_sections(
                     [(
@@ -2179,13 +2180,8 @@ impl ContextEditor {
         });
     }
 
-    pub fn title(&self, cx: &App) -> Cow<str> {
-        self.context
-            .read(cx)
-            .summary()
-            .map(|summary| summary.text.clone())
-            .map(Cow::Owned)
-            .unwrap_or_else(|| Cow::Borrowed(DEFAULT_TAB_TITLE))
+    pub fn title(&self, cx: &App) -> SharedString {
+        self.context.read(cx).summary_or_default()
     }
 
     fn render_patch_block(