fix(ui): retire finished draft recovery mappings

Keep an active composer isolated while sending, then restore the shared draft on a later visit once no recovered work remains. Re-establish the mapping for new text, attachments, or pending intent. Scope the storage-failure test to sessionStorage on every platform.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/IssueChatThread.test.tsx

@@ -3405,8 +3405,13 @@ describe("IssueChatThread", () => {
         </MemoryRouter>
       );
       let root = createRoot(container);
+      const storagePrototype = Object.getPrototypeOf(sessionStorage) as Storage;
+      const originalStorageWrite = storagePrototype.setItem;
       const recoveryWrite = scenario === "unavailable recovery storage"
-        ? vi.spyOn(Object.getPrototypeOf(sessionStorage), "setItem").mockImplementation(() => { throw new Error("Storage full"); })
+        ? vi.spyOn(storagePrototype, "setItem").mockImplementation(function (this: Storage, key: string, value: string) {
+          if (this === sessionStorage) throw new Error("Storage full");
+          return originalStorageWrite.call(this, key, value);
+        })
         : null;
       try {
         await act(async () => root.render(element(false)));
@@ -3476,6 +3481,31 @@ describe("IssueChatThread", () => {
     } finally { await act(async () => root.unmount()); }
   });
 
+  it("returns to the shared draft after finishing a recovery and leaving the task", async () => {
+    const a = "finished-recovery-a";
+    const b = "finished-recovery-b";
+    localStorage.setItem(a, "The other tab's preserved draft");
+    preserveDraftInTab(a, "My recovered message", []);
+    const onAdd = vi.fn().mockResolvedValue(undefined);
+    const root = createRoot(container);
+    const element = (draftKey: string) => (
+      <MemoryRouter><IssueChatThread comments={[]} linkedRuns={[]} timelineEvents={[]} liveRuns={[]}
+        onAdd={onAdd} draftKey={draftKey} enableLiveTranscriptPolling={false} /></MemoryRouter>
+    );
+    const editor = () => container.querySelector<HTMLTextAreaElement>('textarea[aria-label="Issue chat editor"]')!;
+    try {
+      await act(async () => root.render(element(a)));
+      expect(editor().value).toBe("My recovered message");
+      await act(async () => (Array.from(container.querySelectorAll("button")).find(button => button.textContent === "Send") as HTMLButtonElement).click());
+      expect(onAdd.mock.calls[0]![0]).toBe("My recovered message");
+      expect(editor().value).toBe("");
+      await act(async () => root.render(element(b)));
+      await act(async () => root.render(element(a)));
+      expect(editor().value).toBe("The other tab's preserved draft");
+      expect(container.textContent).not.toContain("This draft is kept separately");
+    } finally { await act(async () => root.unmount()); }
+  });
+
   it("stores and restores the composer draft per issue key", () => {
     vi.useFakeTimers();
     const root = createRoot(container);

ui/src/components/IssueChatThread.tsx

@@ -4682,6 +4682,9 @@ const IssueChatComposer = forwardRef<
   const [newRecovery, setDraftRecovery] = useState<{ sourceKey: string; key: string; persisted: boolean } | null>(null);
   const draftRecovery = newRecovery?.sourceKey === sharedDraftKey ? newRecovery : restoredRecovery;
   const draftKey = draftRecovery?.key ?? sharedDraftKey;
+  // Keep the active buffer through send completion. Re-entering a task may
+  // return to its shared draft after an empty recovery has been retired.
+  useEffect(() => setDraftRecovery(restoredRecovery), [sharedDraftKey, restoredRecovery]);
   const retiredDraftKeyRef = useRef<string | undefined>(undefined);
   // Initialize before StrictMode's mount cleanup can flush an empty value over
   // the stored draft. The effect below handles subsequent task-key changes.

ui/src/lib/composer-draft.test.ts

@@ -45,6 +45,28 @@ describe("task draft upload receipts", () => {
     expect(loadDraftSubmission(key)?.attemptId).toBe(id);
   });
 
+  it("retires a finished recovery but keeps or restores its mapping for unsent work", () => {
+    sessionStorage.clear();
+    saveDraft(key, "Shared draft stays available");
+    const fork = preserveDraftInTab(key, "Recovered message", []);
+    saveDraftSubmission(fork.key, { attemptId: id, reviewed: false });
+    expect(settleDraftSubmission(fork.key, id)).toBe(true);
+    expect(loadDraftRecoveryKey(key)).toBeNull();
+    expect(loadDraft(key)).toBe("Shared draft stays available");
+
+    saveDraft(fork.key, "Next recovered draft");
+    expect(loadDraftRecoveryKey(key)).toBe(fork.key);
+    saveDraftSubmission(fork.key, { attemptId: id, reviewed: false, nextDraftOffset: 0, submittedAttachmentIds: [] });
+    expect(settleDraftSubmission(fork.key, id)).toBe(true);
+    expect(loadDraftRecoveryKey(key)).toBe(fork.key);
+    expect(loadDraft(fork.key)).toBe("Next recovered draft");
+    clearDraft(fork.key);
+    expect(loadDraftRecoveryKey(key)).toBeNull();
+    saveDraftAttachments(fork.key, [receipt]);
+    expect(loadDraftRecoveryKey(key)).toBe(fork.key);
+    expect(loadDraftAttachments(fork.key)).toEqual([receipt]);
+  });
+
   it("settles only submitted text and attachments while preserving the next draft", () => {
     const nextId = "aaf8228f-0be7-45ae-a104-6fbe0af6f1d3";
     const nextReceipt = { ...receipt, attachmentId: nextId, contentPath: `/api/attachments/${nextId}/content` };

ui/src/lib/composer-draft.ts

@@ -51,6 +51,17 @@ export function preserveDraftInTab(draftKey: string, body: string, attachments:
   }
 }
 
+function syncDraftRecoveryMarker(draftKey: string) {
+  const prefix = "paperclip:agent-chat-draft:recovered:";
+  if (!draftKey.startsWith(prefix)) return;
+  const marker = `${draftKey}:recovery:v1`;
+  if (loadDraft(draftKey).trim() || loadDraftAttachments(draftKey).length || loadDraftSubmission(draftKey)) {
+    sessionStorage.setItem(marker, draftKey.slice(prefix.length));
+  } else {
+    sessionStorage.removeItem(marker);
+  }
+}
+
 function mayWriteDraft(draftKey: string, attemptId?: string) {
   const pending = loadDraftSubmission(draftKey);
   return !pending || pending.attemptId === attemptId;
@@ -64,6 +75,7 @@ export function saveDraft(draftKey: string, value: string, attemptId?: string) {
     } else {
       draftStorage(draftKey).removeItem(draftKey);
     }
+    syncDraftRecoveryMarker(draftKey);
   } catch {
     // Ignore browser storage failures.
   }
@@ -75,6 +87,7 @@ export function clearDraft(draftKey: string, attemptId?: string) {
     draftStorage(draftKey).removeItem(draftKey);
     draftStorage(draftKey).removeItem(`${draftKey}:attachments:v1`);
     draftStorage(draftKey).removeItem(`${draftKey}:submission:v1`);
+    syncDraftRecoveryMarker(draftKey);
   } catch {
     // Ignore browser storage failures.
   }
@@ -127,6 +140,7 @@ export function saveDraftSubmission(
       `${draftKey}:submission:v1`,
       JSON.stringify({ version: 1, draftKey, ...submission }),
     );
+    syncDraftRecoveryMarker(draftKey);
   } catch {
     /* The composer also retains the fence in memory. */
   }
@@ -134,8 +148,10 @@ export function saveDraftSubmission(
 
 export function clearDraftSubmission(draftKey: string, attemptId: string) {
   try {
-    if (loadDraftSubmission(draftKey)?.attemptId === attemptId)
+    if (loadDraftSubmission(draftKey)?.attemptId === attemptId) {
       draftStorage(draftKey).removeItem(`${draftKey}:submission:v1`);
+      syncDraftRecoveryMarker(draftKey);
+    }
   } catch {
     /* Disabled browser storage is supported in memory. */
   }
@@ -238,6 +254,7 @@ export function saveDraftAttachments(draftKey: string, attachments: unknown, att
         JSON.stringify({ version: 1, draftKey, attachments: selected }),
       );
     else draftStorage(draftKey).removeItem(`${draftKey}:attachments:v1`);
+    syncDraftRecoveryMarker(draftKey);
   } catch {
     /* Disabled/full browser storage must not break the composer. */
   }