From 2dee480486576c9deede3b2ed3808a275b8fd35c Mon Sep 17 00:00:00 2001
From: Matt Toohey <contact@matttoohey.com>
Date: Thu, 9 Apr 2026 11:49:51 +1000
Subject: [PATCH] feat(diff): add commit session launcher to diff modal

Add a commit session launcher to the diff modal sidebar, allowing users
to kick off commit sessions directly from the diff view. The launcher
composes a prompt with launch context (commit SHA, review ID, branch
scope) embedded as XML metadata, which is extracted at drain time to
provide the agent with relevant diff context.

Key changes:
- Commit session launcher component pinned to diff modal sidebar
- Launch context embedding/extraction in session queue pipeline
- Shared stripXmlTags utility to deduplicate XML block stripping
- Queue state awareness with live session status updates
- Commit prompt prefill extracted for reuse across entry points

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 apps/staged/src-tauri/src/session_commands.rs | 162 +++++++++++-
 apps/staged/src/lib/commands.ts               |   9 +-
 .../lib/features/branches/BranchCard.svelte   |   3 +-
 .../features/branches/commitSessionPrefill.ts |   3 +
 .../diff/DiffCommitSessionLauncher.svelte     | 240 ++++++++++++++++++
 .../src/lib/features/diff/DiffModal.svelte    | 112 ++++----
 .../lib/features/sessions/SessionModal.svelte |  15 +-
 .../features/sessions/sessionModalHelpers.ts  |  10 +-
 .../features/timeline/BranchTimeline.svelte   |   6 +-
 .../lib/features/timeline/liveSessionHints.ts |   7 +-
 apps/staged/src/lib/types.ts                  |   7 +
 11 files changed, 505 insertions(+), 69 deletions(-)
 create mode 100644 apps/staged/src/lib/features/branches/commitSessionPrefill.ts
 create mode 100644 apps/staged/src/lib/features/diff/DiffCommitSessionLauncher.svelte

diff --git a/apps/staged/src-tauri/src/session_commands.rs b/apps/staged/src-tauri/src/session_commands.rs
index 437442ecc..c89790f73 100644
--- a/apps/staged/src-tauri/src/session_commands.rs
+++ b/apps/staged/src-tauri/src/session_commands.rs
@@ -448,6 +448,15 @@ pub enum BranchSessionType {
     Review,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct BranchSessionLaunchContext {
+    pub source: String,
+    pub scope: String,
+    pub commit_sha: String,
+    pub review_id: Option<String>,
+}
+
 /// Response from starting a branch session.
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
@@ -623,6 +632,7 @@ pub async fn start_branch_session(
     session_type: BranchSessionType,
     provider: Option<String>,
     image_ids: Option<Vec<String>>,
+    launch_context: Option<BranchSessionLaunchContext>,
 ) -> Result<BranchSessionResponse, String> {
     let store = get_store(&store)?;
 
@@ -711,6 +721,7 @@ pub async fn start_branch_session(
         &project_information,
         &branch_context,
         &session_type,
+        launch_context.as_ref(),
     );
 
     // Create the session
@@ -840,6 +851,7 @@ pub async fn start_branch_session(
 /// (commit or note), but does NOT resolve working directory, git context,
 /// or spawn an agent. The session will be started later via `drain_queued_sessions`.
 #[tauri::command(rename_all = "camelCase")]
+#[allow(clippy::too_many_arguments)]
 pub fn queue_branch_session(
     store: tauri::State<'_, Mutex<Option<Arc<Store>>>>,
     registry: tauri::State<'_, Arc<session_runner::SessionRegistry>>,
@@ -848,6 +860,7 @@ pub fn queue_branch_session(
     session_type: BranchSessionType,
     provider: Option<String>,
     image_ids: Option<Vec<String>>,
+    launch_context: Option<BranchSessionLaunchContext>,
 ) -> Result<BranchSessionResponse, String> {
     let store = get_store(&store)?;
 
@@ -866,7 +879,8 @@ pub fn queue_branch_session(
 
     // Create the queued session — prompt is stored raw (not enriched with
     // context) since context will be built when the session is drained.
-    let mut session = store::Session::new_queued(&prompt);
+    let queued_prompt = embed_launch_context(&prompt, launch_context.as_ref())?;
+    let mut session = store::Session::new_queued(&queued_prompt);
     if let Some(ref p) = provider {
         session = session.with_provider(p);
     }
@@ -975,7 +989,7 @@ pub async fn drain_queued_sessions_for_branch(
         };
 
     // Use the original prompt from the queued session.
-    let prompt = session.prompt.clone();
+    let (prompt, launch_context) = extract_launch_context(&session.prompt)?;
     let session_id = session.id.clone();
 
     // Resolve branch → project (same as start_branch_session).
@@ -1050,6 +1064,7 @@ pub async fn drain_queued_sessions_for_branch(
         &project_information,
         &branch_context,
         &session_type,
+        launch_context.as_ref(),
     );
 
     // Atomically transition session from queued to running.
@@ -1290,6 +1305,7 @@ pub async fn trigger_auto_review(
         &project_information,
         &branch_context,
         &BranchSessionType::Review,
+        None,
     );
 
     // Create the session
@@ -2318,6 +2334,7 @@ fn build_full_prompt(
     project_information: &str,
     branch_context: &str,
     session_type: &BranchSessionType,
+    launch_context: Option<&BranchSessionLaunchContext>,
 ) -> String {
     let action_instructions = match session_type {
         BranchSessionType::Note => {
@@ -2432,16 +2449,88 @@ Rules:
     let action_tag = format!(
         "<action>\n{action_instructions}\n\nProject information:\n{project_information}\n</action>"
     );
+    let branch_history = render_branch_history(branch_context, launch_context);
 
     format!(
         "{action_tag}\n\n\
          <branch-history>\n\
-         {branch_context}\n\
+         {branch_history}\n\
          </branch-history>\n\n\
          {user_prompt}"
     )
 }
 
+fn render_branch_history(
+    branch_context: &str,
+    launch_context: Option<&BranchSessionLaunchContext>,
+) -> String {
+    let mut parts = Vec::new();
+    if !branch_context.trim().is_empty() {
+        parts.push(branch_context.trim_end().to_string());
+    }
+    if let Some(entry) = render_launch_context_entry(launch_context) {
+        parts.push(entry);
+    }
+    parts.join("\n\n")
+}
+
+fn render_launch_context_entry(
+    launch_context: Option<&BranchSessionLaunchContext>,
+) -> Option<String> {
+    let context = launch_context?;
+    if context.source != "diff_viewer" {
+        return None;
+    }
+
+    let scope_suffix = match context.scope.as_str() {
+        "branch" => String::new(),
+        _ => format!(" (scope: {})", context.scope),
+    };
+
+    let mut entry = format!(
+        "Viewed diff before starting this session: commit {}{}.",
+        context.commit_sha, scope_suffix
+    );
+    if let Some(review_id) = context.review_id.as_deref() {
+        entry = format!(
+            "Viewed diff before starting this session: review {} on commit {}{}.",
+            review_id, context.commit_sha, scope_suffix
+        );
+    }
+    Some(entry)
+}
+
+fn embed_launch_context(
+    prompt: &str,
+    launch_context: Option<&BranchSessionLaunchContext>,
+) -> Result<String, String> {
+    let Some(context) = launch_context else {
+        return Ok(prompt.to_string());
+    };
+    let json = serde_json::to_string(context).map_err(|e| e.to_string())?;
+    Ok(format!(
+        "<launch-context>{json}</launch-context>\n\n{}",
+        prompt.trim_start()
+    ))
+}
+
+fn extract_launch_context(
+    prompt: &str,
+) -> Result<(String, Option<BranchSessionLaunchContext>), String> {
+    const OPEN: &str = "<launch-context>";
+    const CLOSE: &str = "</launch-context>";
+
+    let Some(rest) = prompt.strip_prefix(OPEN) else {
+        return Ok((prompt.to_string(), None));
+    };
+    let Some((json, remainder)) = rest.split_once(CLOSE) else {
+        return Err("Queued session prompt had malformed launch context".to_string());
+    };
+    let context =
+        serde_json::from_str::<BranchSessionLaunchContext>(json).map_err(|e| e.to_string())?;
+    Ok((remainder.trim_start().to_string(), Some(context)))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -2527,6 +2616,7 @@ mod tests {
             "project info",
             "branch context",
             &BranchSessionType::Review,
+            None,
         );
 
         assert!(
@@ -2589,4 +2679,70 @@ mod tests {
         let review = store.get_review(&review.id).unwrap().unwrap();
         assert!(review.is_auto);
     }
+
+    #[test]
+    fn commit_prompt_appends_diff_viewer_context_to_branch_history() {
+        let prompt = build_full_prompt(
+            "user prompt",
+            "project info",
+            "branch context",
+            &BranchSessionType::Commit,
+            Some(&BranchSessionLaunchContext {
+                source: "diff_viewer".to_string(),
+                scope: "commit".to_string(),
+                commit_sha: "abc123".to_string(),
+                review_id: Some("review-42".to_string()),
+            }),
+        );
+
+        assert!(prompt.contains(
+            "Viewed diff before starting this session: review review-42 on commit abc123 (scope: commit)."
+        ));
+    }
+
+    #[test]
+    fn commit_prompt_omits_branch_scope_from_diff_viewer_context() {
+        let prompt = build_full_prompt(
+            "user prompt",
+            "project info",
+            "branch context",
+            &BranchSessionType::Commit,
+            Some(&BranchSessionLaunchContext {
+                source: "diff_viewer".to_string(),
+                scope: "branch".to_string(),
+                commit_sha: "abc123".to_string(),
+                review_id: None,
+            }),
+        );
+
+        assert!(prompt.contains("Viewed diff before starting this session: commit abc123."));
+        assert!(!prompt.contains("(scope: branch)"));
+    }
+
+    #[test]
+    fn queued_prompt_round_trips_launch_context() {
+        let prompt = embed_launch_context(
+            "Implement plan",
+            Some(&BranchSessionLaunchContext {
+                source: "diff_viewer".to_string(),
+                scope: "branch".to_string(),
+                commit_sha: "deadbeef".to_string(),
+                review_id: None,
+            }),
+        )
+        .unwrap();
+
+        let (decoded_prompt, launch_context) = extract_launch_context(&prompt).unwrap();
+
+        assert_eq!(decoded_prompt, "Implement plan");
+        assert_eq!(
+            launch_context,
+            Some(BranchSessionLaunchContext {
+                source: "diff_viewer".to_string(),
+                scope: "branch".to_string(),
+                commit_sha: "deadbeef".to_string(),
+                review_id: None,
+            })
+        );
+    }
 }
diff --git a/apps/staged/src/lib/commands.ts b/apps/staged/src/lib/commands.ts
index cee6d7b50..4936b5b58 100644
--- a/apps/staged/src/lib/commands.ts
+++ b/apps/staged/src/lib/commands.ts
@@ -13,6 +13,7 @@ import type {
   Branch,
   BranchTimeline,
   BranchRef,
+  BranchSessionLaunchContext,
   BranchSessionType,
   BranchSessionResponse,
   StoreIncompatibility,
@@ -557,7 +558,8 @@ export function startBranchSession(
   prompt: string,
   sessionType: BranchSessionType,
   provider?: string,
-  imageIds?: string[]
+  imageIds?: string[],
+  launchContext?: BranchSessionLaunchContext
 ): Promise<BranchSessionResponse> {
   return invoke('start_branch_session', {
     branchId,
@@ -565,6 +567,7 @@ export function startBranchSession(
     sessionType,
     provider: provider ?? null,
     imageIds: imageIds ?? null,
+    launchContext: launchContext ?? null,
   });
 }
 
@@ -574,7 +577,8 @@ export function queueBranchSession(
   prompt: string,
   sessionType: BranchSessionType,
   provider?: string,
-  imageIds?: string[]
+  imageIds?: string[],
+  launchContext?: BranchSessionLaunchContext
 ): Promise<BranchSessionResponse> {
   return invoke('queue_branch_session', {
     branchId,
@@ -582,6 +586,7 @@ export function queueBranchSession(
     sessionType,
     provider: provider ?? null,
     imageIds: imageIds ?? null,
+    launchContext: launchContext ?? null,
   });
 }
 
diff --git a/apps/staged/src/lib/features/branches/BranchCard.svelte b/apps/staged/src/lib/features/branches/BranchCard.svelte
index 3f0c426a8..47bba165a 100644
--- a/apps/staged/src/lib/features/branches/BranchCard.svelte
+++ b/apps/staged/src/lib/features/branches/BranchCard.svelte
@@ -38,6 +38,7 @@
   import ReasonBanner from './ReasonBanner.svelte';
   import RemoteWorkspaceStatusBadge from './RemoteWorkspaceStatusBadge.svelte';
   import RemoteWorkspaceStatusView from './RemoteWorkspaceStatusView.svelte';
+  import { getCommitPrefillFromReviewComments } from './commitSessionPrefill';
   import { alerts } from '../../shared/alerts.svelte';
 
   interface Props {
@@ -236,7 +237,7 @@
     const latest = all[0];
 
     if (latest.kind === 'review' && latest.commentCount > 0) {
-      return 'Resolve code review comments';
+      return getCommitPrefillFromReviewComments(latest.commentCount);
     }
     if (latest.kind === 'note' && latest.title.toLowerCase().includes('plan')) {
       return 'Implement plan';
diff --git a/apps/staged/src/lib/features/branches/commitSessionPrefill.ts b/apps/staged/src/lib/features/branches/commitSessionPrefill.ts
new file mode 100644
index 000000000..adcbd2d15
--- /dev/null
+++ b/apps/staged/src/lib/features/branches/commitSessionPrefill.ts
@@ -0,0 +1,3 @@
+export function getCommitPrefillFromReviewComments(userVisibleCommentCount: number): string {
+  return userVisibleCommentCount > 0 ? 'Resolve code review comments' : '';
+}
diff --git a/apps/staged/src/lib/features/diff/DiffCommitSessionLauncher.svelte b/apps/staged/src/lib/features/diff/DiffCommitSessionLauncher.svelte
new file mode 100644
index 000000000..bbb4f7101
--- /dev/null
+++ b/apps/staged/src/lib/features/diff/DiffCommitSessionLauncher.svelte
@@ -0,0 +1,240 @@
+<script lang="ts">
+  import { onMount } from 'svelte';
+  import { listen, type UnlistenFn } from '@tauri-apps/api/event';
+  import { Send } from 'lucide-svelte';
+  import Spinner from '../../shared/Spinner.svelte';
+  import { alerts } from '../../shared/alerts.svelte';
+  import * as commands from '../../api/commands';
+  import { getCommitPrefillFromReviewComments } from '../branches/commitSessionPrefill';
+  import type { SessionStatusPayload } from '../../types';
+
+  interface Props {
+    branchId: string;
+    commitSha: string;
+    scope: 'branch' | 'commit';
+    reviewId?: string;
+    visibleCommentCount: number;
+    onStarted: () => void;
+  }
+
+  let { branchId, commitSha, scope, reviewId, visibleCommentCount, onStarted }: Props = $props();
+
+  let draftPrompt = $state('');
+  let isDirty = $state(false);
+  let starting = $state(false);
+  let timelineLoading = $state(true);
+  let hasRunningSession = $state(false);
+  let textareaElement = $state<HTMLTextAreaElement | null>(null);
+
+  const MIN_TEXTAREA_HEIGHT_PX = 80;
+  const MAX_TEXTAREA_HEIGHT_PX = 260;
+
+  let suggestedPrompt = $derived(getCommitPrefillFromReviewComments(visibleCommentCount));
+  let willQueue = $derived(timelineLoading || hasRunningSession);
+
+  $effect(() => {
+    if (!isDirty) {
+      draftPrompt = suggestedPrompt;
+    }
+  });
+
+  $effect(() => {
+    draftPrompt;
+    syncTextareaHeight();
+  });
+
+  async function refreshQueueState(force = false) {
+    try {
+      const timeline = await commands.getBranchTimeline(branchId, { force });
+      hasRunningSession =
+        timeline.commits.some(
+          (c) => c.sessionStatus === 'running' || c.sessionStatus === 'queued'
+        ) ||
+        timeline.notes.some((n) => n.sessionStatus === 'running' || n.sessionStatus === 'queued') ||
+        timeline.reviews.some((r) => r.sessionStatus === 'running' || r.sessionStatus === 'queued');
+    } catch (e) {
+      console.error('[DiffCommitSessionLauncher] Failed to load timeline:', e);
+      hasRunningSession = false;
+    } finally {
+      timelineLoading = false;
+    }
+  }
+
+  onMount(() => {
+    void refreshQueueState();
+
+    let unlisten: UnlistenFn | null = null;
+    listen<SessionStatusPayload>('session-status-changed', (event) => {
+      if (event.payload.branchId !== branchId) return;
+      void refreshQueueState(true);
+    }).then((fn) => {
+      unlisten = fn;
+    });
+
+    return () => {
+      unlisten?.();
+    };
+  });
+
+  function handleInput(event: Event) {
+    draftPrompt = (event.currentTarget as HTMLTextAreaElement).value;
+    isDirty = true;
+  }
+
+  function syncTextareaHeight() {
+    if (!textareaElement) return;
+
+    textareaElement.style.height = 'auto';
+    textareaElement.style.height = `${Math.min(
+      Math.max(textareaElement.scrollHeight, MIN_TEXTAREA_HEIGHT_PX),
+      MAX_TEXTAREA_HEIGHT_PX
+    )}px`;
+  }
+
+  async function handleSubmit() {
+    const finalPrompt = draftPrompt.trim();
+    if (!finalPrompt || starting) return;
+
+    starting = true;
+    try {
+      await refreshQueueState(true);
+
+      const launchContext = {
+        source: 'diff_viewer' as const,
+        scope,
+        commitSha,
+        reviewId: reviewId ?? null,
+      };
+
+      if (hasRunningSession) {
+        await commands.queueBranchSession(
+          branchId,
+          finalPrompt,
+          'commit',
+          undefined,
+          undefined,
+          launchContext
+        );
+      } else {
+        await commands.startBranchSession(
+          branchId,
+          finalPrompt,
+          'commit',
+          undefined,
+          undefined,
+          launchContext
+        );
+      }
+
+      onStarted();
+    } catch (e) {
+      alerts.show({
+        tone: 'error',
+        title: hasRunningSession
+          ? 'Unable to queue commit session'
+          : 'Unable to start commit session',
+        message: e instanceof Error ? e.message : String(e),
+        durationMs: 0,
+      });
+    } finally {
+      starting = false;
+    }
+  }
+</script>
+
+<div class="composer">
+  <textarea
+    bind:this={textareaElement}
+    class="composer-input"
+    value={draftPrompt}
+    placeholder="Describe any changes you want"
+    rows="3"
+    disabled={starting}
+    oninput={handleInput}
+  ></textarea>
+  <div class="composer-footer">
+    <button
+      class="composer-submit"
+      type="button"
+      onclick={handleSubmit}
+      disabled={starting || !draftPrompt.trim()}
+    >
+      {#if starting}
+        <Spinner size={14} />
+        {willQueue ? 'Queueing…' : 'Starting…'}
+      {:else}
+        <Send size={14} />
+        {willQueue ? 'Queue commit' : 'Start commit'}
+      {/if}
+    </button>
+  </div>
+</div>
+
+<style>
+  .composer {
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+    padding: 12px;
+    border-top: 1px solid var(--border-subtle);
+    background: color-mix(in srgb, var(--bg-chrome) 94%, var(--bg-hover));
+  }
+
+  .composer-input {
+    padding: 10px 12px;
+    background: var(--bg-primary);
+    border: 1px solid var(--border-muted);
+    border-radius: 6px;
+    color: var(--text-primary);
+    font-size: var(--size-sm);
+    font-family: inherit;
+    line-height: 1.5;
+    resize: none;
+    overflow-y: auto;
+    min-height: 80px;
+    max-height: 260px;
+    transition: border-color 0.15s;
+  }
+
+  .composer-input:focus {
+    outline: none;
+    border-color: var(--border-emphasis);
+  }
+
+  .composer-input::placeholder {
+    color: var(--text-faint);
+  }
+
+  .composer-footer {
+    display: flex;
+    align-items: center;
+    justify-content: flex-end;
+    gap: 8px;
+  }
+
+  .composer-submit {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: 6px;
+    padding: 8px 16px;
+    border-radius: 6px;
+    font-size: var(--size-sm);
+    font-weight: 500;
+    cursor: pointer;
+    transition: all 0.15s;
+    background: var(--ui-accent);
+    border: none;
+    color: var(--bg-deepest);
+    width: 100%;
+  }
+
+  .composer-submit:hover:not(:disabled) {
+    background: var(--ui-accent-hover);
+  }
+
+  .composer-submit:disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+  }
+</style>
diff --git a/apps/staged/src/lib/features/diff/DiffModal.svelte b/apps/staged/src/lib/features/diff/DiffModal.svelte
index 3b99f59bd..8b40a6a7a 100644
--- a/apps/staged/src/lib/features/diff/DiffModal.svelte
+++ b/apps/staged/src/lib/features/diff/DiffModal.svelte
@@ -20,6 +20,7 @@
   import { DiffViewer, CrossFileSearchBar } from '@builderbot/diff-viewer/components';
   import DiffCommentsSection from './DiffCommentsSection.svelte';
   import DiffFileTreeSection from './DiffFileTreeSection.svelte';
+  import DiffCommitSessionLauncher from './DiffCommitSessionLauncher.svelte';
   import DiffReferenceSection from './DiffReferenceSection.svelte';
   import ConfirmDialog from '../../shared/ConfirmDialog.svelte';
   import { createDiffViewerState } from './diffViewerState.svelte';
@@ -248,8 +249,9 @@
   let readonlyTree = $derived(compactTree(buildTree(fileEntries)));
   let needsReviewTree = $derived(compactTree(buildTree(needsReview)));
   let reviewedTree = $derived(compactTree(buildTree(reviewed)));
-
   /** Flatten tree nodes depth-first to get the visual file order in the sidebar. */
+  let revealedAnnotations = $derived(annotationsRevealed ? currentAnnotations : []);
+
   function flattenTreeFiles(nodes: TreeNode[]): FileEntry[] {
     const result: FileEntry[] = [];
     for (const node of nodes) {
@@ -543,7 +545,7 @@
           loading={diffViewer.state.loadingFile !== null}
           {beforeLabel}
           {afterLabel}
-          annotations={currentAnnotations}
+          annotations={revealedAnnotations}
           {annotationsRevealed}
           searchState={searchState.state}
           onAddComment={readonly ? undefined : handleAddComment}
@@ -569,49 +571,62 @@
           </div>
         {:else}
           <div class="sidebar-content">
-            <!-- Search bar -->
-            <CrossFileSearchBar
-              files={diffViewer.state.files}
-              loadFileDiff={loadFileDiffForSearch}
-              {searchState}
-            />
-
-            <DiffFileTreeSection
-              {readonly}
-              {fileEntries}
-              {needsReview}
-              {reviewed}
-              {readonlyTree}
-              {needsReviewTree}
-              {reviewedTree}
-              selectedFile={diffViewer.state.selectedFile}
-              {isCollapsed}
-              onToggleDir={toggleDir}
-              onSelectFile={selectFile}
-              onToggleReviewed={toggleReviewed}
-              onJumpToLine={handleJumpToLine}
-              {searchState}
-              diffViewerState={diffViewer}
-            />
-            {#if !readonly}
-              <DiffReferenceSection
-                referenceFiles={reviewHandle?.state.referenceFiles ?? []}
-                selectedFile={diffViewer.state.selectedFile}
-                onSelectFile={(path) => {
-                  selectedCommentId = null;
-                  diffViewer.selectFile(path);
-                }}
-                onRemoveReferenceFile={handleRemoveReferenceFile}
+            <div class="sidebar-scroll">
+              <!-- Search bar -->
+              <CrossFileSearchBar
+                files={diffViewer.state.files}
+                loadFileDiff={loadFileDiffForSearch}
+                {searchState}
               />
 
-              <DiffCommentsSection
-                comments={currentComments}
-                {selectedCommentId}
-                {copiedFeedback}
-                onSelectComment={handleSelectComment}
-                onCopyAll={handleCopyComments}
-                onDeleteAll={handleDeleteAllComments}
-                onDeleteComment={handleDeleteComment}
+              <DiffFileTreeSection
+                {readonly}
+                {fileEntries}
+                {needsReview}
+                {reviewed}
+                {readonlyTree}
+                {needsReviewTree}
+                {reviewedTree}
+                selectedFile={diffViewer.state.selectedFile}
+                {isCollapsed}
+                onToggleDir={toggleDir}
+                onSelectFile={selectFile}
+                onToggleReviewed={toggleReviewed}
+                onJumpToLine={handleJumpToLine}
+                {searchState}
+                diffViewerState={diffViewer}
+              />
+              {#if !readonly}
+                <DiffReferenceSection
+                  referenceFiles={reviewHandle?.state.referenceFiles ?? []}
+                  selectedFile={diffViewer.state.selectedFile}
+                  onSelectFile={(path) => {
+                    selectedCommentId = null;
+                    diffViewer.selectFile(path);
+                  }}
+                  onRemoveReferenceFile={handleRemoveReferenceFile}
+                />
+
+                <DiffCommentsSection
+                  comments={currentComments}
+                  {selectedCommentId}
+                  {copiedFeedback}
+                  onSelectComment={handleSelectComment}
+                  onCopyAll={handleCopyComments}
+                  onDeleteAll={handleDeleteAllComments}
+                  onDeleteComment={handleDeleteComment}
+                />
+              {/if}
+            </div>
+
+            {#if !readonly && diffViewer.state.commitSha}
+              <DiffCommitSessionLauncher
+                {branchId}
+                commitSha={diffViewer.state.commitSha}
+                {scope}
+                {reviewId}
+                visibleCommentCount={currentComments.length}
+                onStarted={onClose}
               />
             {/if}
           </div>
@@ -761,16 +776,23 @@
     width: 240px;
     flex-shrink: 0;
     border-left: none;
-    overflow-y: auto;
-    overflow-x: hidden;
+    overflow: hidden;
   }
 
   .sidebar-content {
     display: flex;
     flex-direction: column;
+    height: 100%;
     padding: 0;
   }
 
+  .sidebar-scroll {
+    flex: 1;
+    min-height: 0;
+    overflow-y: auto;
+    overflow-x: hidden;
+  }
+
   .sidebar-loading,
   .sidebar-error,
   .sidebar-empty {
diff --git a/apps/staged/src/lib/features/sessions/SessionModal.svelte b/apps/staged/src/lib/features/sessions/SessionModal.svelte
index 923c8aa3e..b711aa95f 100644
--- a/apps/staged/src/lib/features/sessions/SessionModal.svelte
+++ b/apps/staged/src/lib/features/sessions/SessionModal.svelte
@@ -67,6 +67,7 @@
     verbGroupSummary,
     hasXmlBlocks,
     stripCodeFences,
+    stripXmlTags,
   } from './sessionModalHelpers';
   import InContentSearch from '../../shared/InContentSearch.svelte';
   import { highlightMatches, clearHighlights, scrollToMatch } from '../../shared/textHighlight';
@@ -594,7 +595,7 @@
     const segments: ContentSegment[] = [];
     let remaining = content;
 
-    const tagPattern = /<(action|branch-history)>([\s\S]*?)<\/\1>/g;
+    const tagPattern = /<(action|branch-history|launch-context)>([\s\S]*?)<\/\1>/g;
     let lastIndex = 0;
     let match: RegExpExecArray | null;
 
@@ -606,7 +607,12 @@
       }
 
       const tag = match[1];
-      const label = tag === 'action' ? 'Action instructions' : 'Branch history';
+      const label =
+        tag === 'action'
+          ? 'Action instructions'
+          : tag === 'branch-history'
+            ? 'Branch history'
+            : 'Launch context';
       const icon = tag === 'action' ? Zap : GitBranch;
       segments.push({ type: 'xml-block', tag, label, content: match[2].trim(), icon });
 
@@ -840,10 +846,7 @@
     <header class="modal-header">
       <div class="header-content">
         <span class="header-title">
-          {session?.prompt
-            ? session.prompt.replace(/<(action|branch-history)>[\s\S]*?<\/\1>/g, '').trim() ||
-              'Session'
-            : 'Session'}
+          {session?.prompt ? stripXmlTags(session.prompt) || 'Session' : 'Session'}
         </span>
       </div>
       <InContentSearch
diff --git a/apps/staged/src/lib/features/sessions/sessionModalHelpers.ts b/apps/staged/src/lib/features/sessions/sessionModalHelpers.ts
index 8710ee3d8..666855d02 100644
--- a/apps/staged/src/lib/features/sessions/sessionModalHelpers.ts
+++ b/apps/staged/src/lib/features/sessions/sessionModalHelpers.ts
@@ -8,8 +8,16 @@ export interface ToolDisplay {
   detail: string;
 }
 
+/** Pattern matching XML-tagged context blocks embedded in prompts/messages. */
+const XML_BLOCK_PATTERN = /<(action|branch-history|launch-context)>[\s\S]*?<\/\1>/g;
+
 export function hasXmlBlocks(content: string): boolean {
-  return /<(action|branch-history)>/.test(content);
+  return /<(action|branch-history|launch-context)>/.test(content);
+}
+
+/** Strip XML-tagged context blocks (action, branch-history, launch-context) from display text. */
+export function stripXmlTags(text: string): string {
+  return text.replace(XML_BLOCK_PATTERN, '').trim();
 }
 
 export function parseToolCall(content: string): ParsedToolCall | null {
diff --git a/apps/staged/src/lib/features/timeline/BranchTimeline.svelte b/apps/staged/src/lib/features/timeline/BranchTimeline.svelte
index d011f2c91..21adf8731 100644
--- a/apps/staged/src/lib/features/timeline/BranchTimeline.svelte
+++ b/apps/staged/src/lib/features/timeline/BranchTimeline.svelte
@@ -25,6 +25,7 @@
     type PendingHintItemType,
   } from './liveSessionHints';
   import { isEmptyFailedReview } from './reviewState';
+  import { stripXmlTags } from '../sessions/sessionModalHelpers';
 
   type PendingItem = {
     key: string;
@@ -194,11 +195,6 @@
     deleteDisabledReason?: string;
   };
 
-  /** Strip XML-tagged context blocks (action, branch-history) from display text. */
-  function stripXmlTags(text: string): string {
-    return text.replace(/<(action|branch-history)>[\s\S]*?<\/\1>/g, '').trim();
-  }
-
   let runningSessionIds = $derived.by(() => collectRunningSessionIds(timeline, pendingItems));
 
   /** True when there is at least one non-queued active session (running in timeline or pending-but-not-queued). */
diff --git a/apps/staged/src/lib/features/timeline/liveSessionHints.ts b/apps/staged/src/lib/features/timeline/liveSessionHints.ts
index 44650bb5c..3949aceb8 100644
--- a/apps/staged/src/lib/features/timeline/liveSessionHints.ts
+++ b/apps/staged/src/lib/features/timeline/liveSessionHints.ts
@@ -1,6 +1,6 @@
 import * as commands from '../../api/commands';
 import type { BranchTimeline, SessionMessage } from '../../types';
-import { formatToolDisplay } from '../sessions/sessionModalHelpers';
+import { formatToolDisplay, stripXmlTags } from '../sessions/sessionModalHelpers';
 
 const HINT_POLL_INTERVAL_MS = 750;
 const MAX_HINT_LENGTH = 72;
@@ -18,11 +18,6 @@ export type PendingHintItem = {
   sessionId?: string;
 };
 
-/** Strip XML-tagged context blocks (action, branch-history) from display text. */
-function stripXmlTags(text: string): string {
-  return text.replace(/<(action|branch-history)>[\s\S]*?<\/\1>/g, '').trim();
-}
-
 function normalizeHintText(text: string): string | undefined {
   const cleaned = stripXmlTags(text)
     .replace(/```[\s\S]*?```/g, ' ')
diff --git a/apps/staged/src/lib/types.ts b/apps/staged/src/lib/types.ts
index b7cb386b2..c03d2b752 100644
--- a/apps/staged/src/lib/types.ts
+++ b/apps/staged/src/lib/types.ts
@@ -254,6 +254,13 @@ export interface SessionMessage {
 
 export type BranchSessionType = 'note' | 'commit' | 'review';
 
+export interface BranchSessionLaunchContext {
+  source: 'diff_viewer';
+  scope: 'branch' | 'commit';
+  commitSha: string;
+  reviewId?: string | null;
+}
+
 export interface BranchSessionResponse {
   sessionId: string;
   artifactId: string;