feat(desktop): defer new task session creation until first message (#746)

apps/desktop/src/components/Sidebar.tsx

@@ -619,10 +619,9 @@ export function Sidebar({
       : sessions.filter(
           (session) => !sessionArchived(session, sessionMeta[session.id]),
         );
-    // Empty sessions are durable sidebar rows now. Their message count, not
-    // their title, controls New Task reuse, so a manual rename never changes
-    // the empty-slot behavior.
-    return candidates;
+    // New-task drafts stay out of history until they carry input: sessions
+    // with only a default title (including legacy empty drafts) never render.
+    return candidates.filter((session) => !isDefaultSessionTitle(session.title));
   }, [sessions, showArchived, sessionMeta]);
 
   const compareSessions = useCallback((a: SessionSummary, b: SessionSummary) => {

apps/desktop/src/stores/slices/session-slice.ts

@@ -23,6 +23,7 @@ import {
   sessionNeedsModelPin,
 } from "../../lib/session-model";
 import {
+  clearSessionPanes,
   retainSessionPane,
 } from "../../lib/session-panes";
 import {
@@ -476,28 +477,23 @@ export function createSessionSlice({
           if (!runtime.navigationIntentIsCurrent(intent)) return;
         }
 
-        const latest = runtime.latestSessionInScope(
-          get().sessions,
-          requestedProjectPath,
-          get().sessionMeta,
-        );
-        if (
-          latest &&
-          sessionIsReusableEmpty(latest, {
-            running: get().runningSessions[latest.id] === true,
-            liveMessageCount: runtime.liveMessageCountForSession(latest.id, get()),
-            submitted: runtime.submittedComposerDrafts.has(latest.id),
-          })
-        ) {
-          if (get().activeSessionId === latest.id && get().page === "chat") return;
-          await get().selectSession(latest.id, { navigationIntent: intent });
-          return;
-        }
-
-        await persistSessionAndSelect({
-          intent,
-          projectPath: requestedProjectPath,
-          draftConfiguration: null,
+        // New task starts as an unpersisted draft (ADR 0084): no session is created
+        // and no sidebar history row appears until the first message materializes it.
+        // The draft stays within its requested project scope, if any.
+        set((s) => {
+          const stack = s.navStack.slice(0, s.navIndex + 1);
+          const nextStack = [...stack, { page: "chat" as const }].slice(-50);
+          return {
+            ...switchWorkPanelSession(s, undefined),
+            ...clearSessionPanes(),
+            activeSessionId: undefined,
+            draftConfiguration: null,
+            messages: [],
+            page: "chat" as const,
+            navStack: nextStack,
+            navIndex: nextStack.length - 1,
+            isRunning: false,
+          };
         });
       })();
       runtime.pendingNewSessionRequests.set(scopeKey, request);

apps/desktop/test/app-store-sidebar.test.mjs

@@ -66,13 +66,12 @@ test("project new-session creation uses one store-owned navigation transaction",
   );
 });
 
-test("durable empty sessions render and title heuristics do not filter them", () => {
-  assert.doesNotMatch(
+test("new-task drafts stay out of sidebar history until the first message", () => {
+  assert.match(
     sidebarSource,
     /candidates\.filter\(\(session\) => !isDefaultSessionTitle\(session\.title\)\)/,
   );
-  assert.match(storeSource, /latestSessionInScope/);
-  assert.match(storeSource, /sessionIsReusableEmpty/);
+  assert.match(storeSource, /New task starts as an unpersisted draft/);
   assert.match(storeSource, /pendingNewSessionRequests/);
   assert.doesNotMatch(sidebarSource, /keptEmptyScopes/);
 });

apps/desktop/test/composer-send-state.test.mjs

@@ -189,26 +189,18 @@ test("editing a queued prompt needs an empty composer and restores its draft", (
   assert.doesNotMatch(queueSlice, /text: item\.content/);
 });
 
-test("new task persists or reuses an empty session and keeps the run flag scoped", () => {
+test("new task opens an unpersisted draft and keeps the run flag scoped", () => {
   const newSession = sessionSlice.match(
     /newSession: async [\s\S]*?\n    forkSession: async/,
   )?.[0] ?? "";
   assert.ok(newSession.length > 0, "newSession implementation not found");
-  assert.match(newSession, /latestSessionInScope/);
-  assert.match(newSession, /sessionIsReusableEmpty/);
-  assert.match(newSession, /persistSessionAndSelect/);
+  assert.match(newSession, /New task starts as an unpersisted draft/);
+  assert.match(newSession, /activeSessionId: undefined/);
   assert.match(newSession, /pendingNewSessionRequests/);
   assert.doesNotMatch(newSession, /refreshSessions/);
-  // A newly selected empty session uses its own run state, so a turn still
-  // streaming in the previous session cannot leave it stuck on the stop
-  // button.
   assert.match(
     sessionCoordination,
-    /async function persistSessionAndSelect[\s\S]*?\n    return sessionId;\n  }\n/,
-  );
-  assert.match(
-    sessionCoordination,
-    /isRunning: current\.runningSessions\[summary\.id\] \?\? false/,
+    /async function materializeDraftSession[\s\S]*?\n    return persistSessionAndSelect\(\{ intent \}\);\n  \}\n/,
   );
 });
 

apps/desktop/test/session-create.test.mjs

@@ -35,14 +35,13 @@ test("empty sessions have a whole, already-known transcript window", () => {
   });
 });
 
-test("new task reuses renderer-empty sessions without a blocking list refresh", () => {
+test("new task opens unpersisted draft without a blocking list refresh", () => {
   const newSession =
     sessionSlice.match(/newSession: async [\s\S]*?\n    forkSession: async/)?.[0] ?? "";
   assert.ok(newSession.length > 0, "newSession implementation not found");
-  assert.match(newSession, /sessionIsReusableEmpty/);
-  assert.match(newSession, /liveMessageCountForSession/);
+  assert.match(newSession, /New task starts as an unpersisted draft/);
+  assert.match(newSession, /activeSessionId: undefined/);
   assert.doesNotMatch(newSession, /refreshSessions/);
-  assert.match(newSession, /persistSessionAndSelect/);
   assert.match(newSession, /pendingNewSessionRequests/);
 });
 

docs/adr/0084-deferred-new-task-session-creation.md

@@ -2,7 +2,7 @@
 
 - **Status:** Accepted
 - **Date:** 2026-08-14
-- **Related:** D220 · D088 · D093 · E2E-011b · E2E-011d
+- **Related:** D220 · D088 · D093 · E2E-011b · E2E-011d · #746
 
 ## Context
 

docs/adr/0113-immediate-empty-session-slot-and-deduplication.md

@@ -1,6 +1,6 @@
 # ADR 0113: Persist the New Task empty slot immediately and deduplicate it by message count
 
-- **Status:** Accepted
+- **Status:** Superseded by reinstatement of ADR 0084 (#746)
 - **Date:** 2026-08-21
 - **Supersedes:** ADR 0084 / D220
 - **Related:** D088 · D093 · D305 · E2E-011b · E2E-011d · E2E-011e · E2E-011g