fix(canvas): keep "agent is working" indicator alive for external/poll-mode turns

External / MCP-registered workspaces (delivery_mode=poll, e.g. the
local-Mac orchestrator) have no public URL: POST /workspaces/:id/a2a
short-circuits server-side (a2a_proxy.go:402) and returns a synthetic
{status:"queued", delivery_mode:"poll"} envelope IMMEDIATELY with no
reply. useChatSend treated that as a terminal response and called
releaseSendGuards() → `sending` went false the instant the POST
returned → the ChatTab thinking indicator vanished and the external
turn looked dead, even though the agent had not started. Internal
agents reply on the same synchronous POST so their indicator naturally
holds — that's the whole asymmetry; the transport is shared.

Fix (Tier A, minimal, client-only): detect the synthetic poll envelope
and KEEP `sending` true so the existing internal working-indicator
persists as a "received — agent is working" state. The eventual reply
already flows AgentMessageWriter → AGENT_MESSAGE WS push →
useChatSocket onAgentMessage/onSendComplete → releaseSendGuards, i.e.
the external reply now drives the indicator through the exact same path
an internal async reply uses — no parallel system. A generous 15-min
safety timer surfaces an honest, actionable error instead of an
infinite spinner if an offline poll agent never replies.

Tier B (lifecycle-driven interim progress) and Tier C (tool-call
parity — has an operator-privacy tradeoff, CTO decision required) are
designed in internal RFC external-workspace-canvas-progress-feedback,
not in this PR.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

canvas/src/components/tabs/chat/hooks/__tests__/useChatSend.test.tsx

@@ -0,0 +1,209 @@
+// @vitest-environment jsdom
+/**
+ * Tests for useChatSend — the canvas user→agent send hook.
+ *
+ * Behavioural focus: the poll-mode ("queued") path. When the target
+ * workspace is an external / MCP-registered agent (delivery_mode=poll,
+ * e.g. an operator laptop running the molecule MCP channel), the
+ * platform's POST /workspaces/:id/a2a returns a synthetic
+ * {status:"queued", delivery_mode:"poll"} envelope IMMEDIATELY with no
+ * reply — the real reply arrives later over the AGENT_MESSAGE
+ * WebSocket push.
+ *
+ * Pre-fix the hook treated that synthetic envelope as a terminal
+ * response and called releaseSendGuards() → `sending` went false the
+ * instant the POST returned → the "agent is working" indicator
+ * vanished and the external turn looked dead. This suite pins the
+ * fixed contract:
+ *
+ *   - a real reply still clears `sending` (regression guard)
+ *   - a poll "queued" envelope KEEPS `sending` true (no terminal
+ *     clear) so the existing thinking indicator persists
+ *   - the eventual reply path (releaseSendGuards, the same call the
+ *     AGENT_MESSAGE WS push makes via useChatSocket) clears it
+ *   - an offline poll agent that never replies eventually surfaces an
+ *     honest error instead of an infinite spinner
+ *
+ * Plus pure-function coverage for the poll-envelope detector.
+ *
+ * Root cause: workspace-server a2a_proxy.go:402 poll-mode
+ * short-circuit returns {status:"queued"} synchronously.
+ */
+import {
+  describe,
+  it,
+  expect,
+  vi,
+  beforeEach,
+  afterEach,
+  type Mock,
+} from "vitest";
+import { act, renderHook, cleanup } from "@testing-library/react";
+
+const { mockApiPost } = vi.hoisted(() => ({ mockApiPost: vi.fn() }));
+
+vi.mock("@/lib/api", () => ({
+  api: { post: mockApiPost },
+}));
+
+vi.mock("../uploads", () => ({
+  uploadChatFiles: vi.fn(),
+}));
+
+// Import AFTER mocks.
+import {
+  useChatSend,
+  isPollQueuedResponse,
+  extractReplyText,
+  POLL_QUEUED_REPLY_TIMEOUT_MS,
+} from "../useChatSend";
+
+const flush = () => act(async () => { await Promise.resolve(); });
+
+describe("isPollQueuedResponse", () => {
+  it("is true only for the synthetic poll-mode queued envelope", () => {
+    expect(isPollQueuedResponse({ status: "queued", delivery_mode: "poll" })).toBe(true);
+  });
+
+  it("is false for a real agent reply", () => {
+    expect(
+      isPollQueuedResponse({ result: { parts: [{ kind: "text", text: "hi" }] } }),
+    ).toBe(false);
+  });
+
+  it("is false for null / undefined / partial shapes", () => {
+    expect(isPollQueuedResponse(null)).toBe(false);
+    expect(isPollQueuedResponse(undefined)).toBe(false);
+    // status=queued without delivery_mode=poll is NOT the poll envelope
+    // — don't accidentally swallow a real reply that happens to carry
+    // an unrelated status field.
+    expect(isPollQueuedResponse({ status: "queued" })).toBe(false);
+    expect(isPollQueuedResponse({ delivery_mode: "poll" })).toBe(false);
+  });
+});
+
+describe("extractReplyText (regression guard — unchanged by fix)", () => {
+  it("collects text parts from result", () => {
+    expect(
+      extractReplyText({ result: { parts: [{ kind: "text", text: "hello" }] } }),
+    ).toBe("hello");
+  });
+  it("returns empty for the poll-queued envelope", () => {
+    expect(extractReplyText({ status: "queued", delivery_mode: "poll" })).toBe("");
+  });
+});
+
+describe("useChatSend — poll-mode in-progress state", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    mockApiPost.mockReset();
+  });
+  afterEach(() => {
+    vi.runOnlyPendingTimers();
+    vi.useRealTimers();
+    cleanup();
+  });
+
+  const setup = () => {
+    const onUserMessage = vi.fn();
+    const onAgentMessage = vi.fn();
+    const { result } = renderHook(() =>
+      useChatSend("ws-ext-1", {
+        getHistoryMessages: () => [],
+        onUserMessage,
+        onAgentMessage,
+      }),
+    );
+    return { result, onUserMessage, onAgentMessage };
+  };
+
+  it("a real reply clears `sending` (regression guard)", async () => {
+    mockApiPost.mockResolvedValue({
+      result: { parts: [{ kind: "text", text: "real reply" }] },
+    });
+    const { result, onAgentMessage } = setup();
+
+    await act(async () => {
+      void result.current.sendMessage("hi");
+    });
+    await flush();
+
+    expect(onAgentMessage).toHaveBeenCalledTimes(1);
+    expect(result.current.sending).toBe(false);
+  });
+
+  it("keeps `sending` true on a poll 'queued' envelope (no terminal clear)", async () => {
+    mockApiPost.mockResolvedValue({ status: "queued", delivery_mode: "poll" });
+    const { result, onAgentMessage } = setup();
+
+    await act(async () => {
+      void result.current.sendMessage("hi external agent");
+    });
+    await flush();
+
+    // The POST resolved, but it was only a queued ack — the indicator
+    // must stay up and no agent bubble should be rendered yet.
+    expect(result.current.sending).toBe(true);
+    expect(onAgentMessage).not.toHaveBeenCalled();
+    expect(result.current.error).toBeNull();
+  });
+
+  it("releaseSendGuards (the AGENT_MESSAGE-push path) clears the poll in-progress state", async () => {
+    mockApiPost.mockResolvedValue({ status: "queued", delivery_mode: "poll" });
+    const { result } = setup();
+
+    await act(async () => {
+      void result.current.sendMessage("hi");
+    });
+    await flush();
+    expect(result.current.sending).toBe(true);
+
+    // Simulate the terminal AGENT_MESSAGE WebSocket push arriving:
+    // useChatSocket's onAgentMessage / onSendComplete call
+    // releaseSendGuards. That must clear the in-progress state AND the
+    // safety timer (asserted by the next test).
+    act(() => {
+      result.current.releaseSendGuards();
+    });
+    expect(result.current.sending).toBe(false);
+  });
+
+  it("surfaces an honest error if a poll agent never replies (safety timeout)", async () => {
+    mockApiPost.mockResolvedValue({ status: "queued", delivery_mode: "poll" });
+    const { result } = setup();
+
+    await act(async () => {
+      void result.current.sendMessage("hi");
+    });
+    await flush();
+    expect(result.current.sending).toBe(true);
+
+    act(() => {
+      vi.advanceTimersByTime(POLL_QUEUED_REPLY_TIMEOUT_MS + 1000);
+    });
+
+    expect(result.current.sending).toBe(false);
+    expect(result.current.error).toMatch(/queued/i);
+  });
+
+  it("does NOT fire the safety error when the reply arrives before timeout", async () => {
+    mockApiPost.mockResolvedValue({ status: "queued", delivery_mode: "poll" });
+    const { result } = setup();
+
+    await act(async () => {
+      void result.current.sendMessage("hi");
+    });
+    await flush();
+
+    // Reply arrives (releaseSendGuards) well before the timeout.
+    act(() => {
+      result.current.releaseSendGuards();
+    });
+    act(() => {
+      vi.advanceTimersByTime(POLL_QUEUED_REPLY_TIMEOUT_MS + 1000);
+    });
+
+    expect(result.current.error).toBeNull();
+    expect(result.current.sending).toBe(false);
+  });
+});

canvas/src/components/tabs/chat/hooks/useChatSend.ts

@@ -1,6 +1,6 @@
 "use client";
 
-import { useCallback, useRef, useState } from "react";
+import { useCallback, useEffect, useRef, useState } from "react";
 import { api } from "@/lib/api";
 import { uploadChatFiles } from "../uploads";
 import { createMessage, type ChatMessage, type ChatAttachment } from "../types";
@@ -22,8 +22,42 @@ interface A2AResponse {
     parts?: A2APart[];
     artifacts?: Array<{ parts: A2APart[] }>;
   };
+  /** Synthetic poll-mode envelope. The platform returns this
+   *  immediately (HTTP 200) when the target workspace is registered
+   *  delivery_mode=poll — an external / MCP-registered agent with no
+   *  public URL (e.g. an operator's laptop running the molecule MCP
+   *  channel). The request has only been QUEUED into activity_logs;
+   *  the agent will pick it up on its next poll and the real reply
+   *  arrives asynchronously over the AGENT_MESSAGE WebSocket push
+   *  (consumed by useChatSocket). See workspace-server
+   *  a2a_proxy.go:402 (poll-mode short-circuit) and
+   *  a2a_proxy_helpers.go:516 (logA2AReceiveQueued). */
+  status?: string;
+  delivery_mode?: string;
 }
 
+/** True when `resp` is the platform's synthetic poll-mode "queued"
+ *  envelope rather than a real agent reply. For these the send is
+ *  acknowledged-but-pending: the user's message landed and the agent
+ *  is working, but there is no reply yet — the terminal AGENT_MESSAGE
+ *  push will arrive later over the WebSocket. Treating this as a
+ *  terminal response (the pre-fix behaviour) cleared the "agent is
+ *  working" indicator the instant the POST returned, so an external
+ *  workspace turn looked dead even though work had not started. */
+export function isPollQueuedResponse(resp: A2AResponse | null | undefined): boolean {
+  return !!resp && resp.status === "queued" && resp.delivery_mode === "poll";
+}
+
+/** Hard ceiling on how long the "agent is working" indicator stays up
+ *  for a poll-mode turn with no reply. The terminal AGENT_MESSAGE push
+ *  normally clears it well before this. The cap exists so a poll-mode
+ *  workspace that is offline / never consumes its queue doesn't pin a
+ *  spinner forever — at which point we surface an honest, actionable
+ *  error instead of an opaque dead spinner. Generous because poll
+ *  agents (an operator laptop) can legitimately take minutes to wake,
+ *  poll, and respond; the goal is "eventually honest", not fail-fast. */
+export const POLL_QUEUED_REPLY_TIMEOUT_MS = 15 * 60 * 1000;
+
 export function extractReplyText(resp: A2AResponse): string {
   const collect = (parts: A2APart[] | undefined): string => {
     if (!parts) return "";
@@ -59,14 +93,29 @@ export function useChatSend(workspaceId: string, options: UseChatSendOptions) {
   const sendInFlightRef = useRef(false);
   const sendingFromAPIRef = useRef(false);
   const sendTokenRef = useRef(0);
+  // Safety-net timer armed only for poll-mode ("queued") turns: the
+  // POST returns immediately with no reply, so the normal
+  // POST-resolves-→-clear-spinner path can't drive the indicator. The
+  // terminal AGENT_MESSAGE WebSocket push clears it via
+  // releaseSendGuards (which also clears this timer); the timer is the
+  // backstop for an offline poll agent that never consumes its queue.
+  const pollTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const optionsRef = useRef(options);
   optionsRef.current = options;
 
+  const clearPollTimeout = useCallback(() => {
+    if (pollTimeoutRef.current !== null) {
+      clearTimeout(pollTimeoutRef.current);
+      pollTimeoutRef.current = null;
+    }
+  }, []);
+
   const releaseSendGuards = useCallback(() => {
+    clearPollTimeout();
     setSending(false);
     sendingFromAPIRef.current = false;
     sendInFlightRef.current = false;
-  }, []);
+  }, [clearPollTimeout]);
 
   const clearError = useCallback(() => setError(null), []);
 
@@ -146,6 +195,33 @@ export function useChatSend(workspaceId: string, options: UseChatSendOptions) {
             sendInFlightRef.current = false;
             return;
           }
+          // Poll-mode ("queued") turn: the message landed and the
+          // external/MCP agent will pick it up on its next poll, but
+          // there is NO reply in this response. Pre-fix this fell
+          // through to releaseSendGuards() below and the "agent is
+          // working" indicator vanished the instant the POST returned —
+          // an external-workspace turn looked dead even though work had
+          // not started. Instead, keep `sending` true so the existing
+          // thinking indicator (the same one internal agents use)
+          // persists as a "received — agent is working" state; the
+          // terminal AGENT_MESSAGE WebSocket push (consumed by
+          // useChatSocket → onAgentMessage / onSendComplete →
+          // releaseSendGuards) clears it when the real reply arrives,
+          // exactly the path an internal async reply already uses.
+          if (isPollQueuedResponse(resp)) {
+            clearPollTimeout();
+            pollTimeoutRef.current = setTimeout(() => {
+              if (sendTokenRef.current !== myToken) return;
+              if (!sendingFromAPIRef.current) return;
+              releaseSendGuards();
+              setError(
+                "No response yet from this agent — it may be offline or " +
+                  "busy. Your message was delivered and is queued; the " +
+                  "reply will appear here if the agent picks it up.",
+              );
+            }, POLL_QUEUED_REPLY_TIMEOUT_MS);
+            return;
+          }
           const replyText = extractReplyText(resp);
           const replyFiles = extractFilesFromTask(
             (resp?.result ?? {}) as Record<string, unknown>,
@@ -167,9 +243,15 @@ export function useChatSend(workspaceId: string, options: UseChatSendOptions) {
           setError("Failed to send message — agent may be unreachable");
         });
     },
-    [workspaceId, sending, uploading],
+    [workspaceId, sending, uploading, clearPollTimeout],
   );
 
+  // Drop the poll-mode safety timer on unmount / workspace switch so a
+  // stale timeout can't fire setError against a panel the user has
+  // already navigated away from. sendTokenRef guards correctness if it
+  // ever did fire; this just avoids the wasted timer + setState churn.
+  useEffect(() => clearPollTimeout, [clearPollTimeout]);
+
   return {
     sending,
     uploading,