Show resume failure when a running turn cannot be restored

packages/chat-ui/src/chat-workspace.tsx

@@ -13,6 +13,7 @@
 
 import { isAgentAddress } from "@corbits/chat/mentions";
 import { Button, EmptyState, toast } from "@corbits/react-ui";
+import { reportError } from "@corbits/error-sink";
 import {
   CaretDown,
   ChatCircle,
@@ -56,6 +57,7 @@ import { useTurnActivity, TurnActivityStrip } from "./turn-activity";
 import type { StreamingReplyState } from "./streaming-reply";
 import { AgentBadge, WorkbenchTimeline, messageDomId } from "./timeline";
 import { NoUsableModelBanner } from "./no-usable-model-banner";
+import { ResumeFailedBanner } from "./resume-failed-banner";
 import type {
   CurrentUser,
   PinActions,
@@ -625,6 +627,12 @@ function ChatWorkspaceInner({
     onWorkbenchChange?.(id);
   };
   const [inviteDialogOpen, setInviteDialogOpen] = useState(false);
+  // CL-6833: catch-up `fetchRunningTurn` failure must surface a banner with
+  // Retry — never look idle. `resumeAttempt` re-arms the effect on Retry.
+  const [resumeFailedRefId, setResumeFailedRefId] = useState<string | null>(
+    null,
+  );
+  const [resumeAttempt, setResumeAttempt] = useState(0);
   // null = workbench root feed. A concrete id opens that thread in the same
   // geometry (timeline + composer). pendingParentMessageId is set when the
   // user opens a reply on a message that has no thread yet.
@@ -932,20 +940,39 @@ function ChatWorkspaceInner({
   // rather than showing nothing until the next live token arrives. Any
   // live event that beats this fetch back always wins — see
   // `resumeFromTurn`'s own guard.
+  // CL-6833: a failed catch-up must not swallow into idle — report a ref
+  // and keep `ResumeFailedBanner` visible until Retry succeeds (or the
+  // workbench changes).
   useEffect(() => {
     if (activeWorkbenchId === null || resumeAgentAddress === undefined) {
+      setResumeFailedRefId(null);
       return;
     }
     let cancelled = false;
     fetchRunningTurn(tenantId, activeWorkbenchId, resumeAgentAddress)
       .then((runningTurn) => {
-        if (!cancelled) resumeFromTurn(runningTurn);
+        if (cancelled) return;
+        setResumeFailedRefId(null);
+        resumeFromTurn(runningTurn);
       })
-      .catch(() => undefined);
+      .catch((cause) => {
+        if (cancelled) return;
+        const refId = reportError(cause, {
+          operation: "chat.resumeRunningTurn",
+          tenantId,
+          roomId: activeWorkbenchId,
+          agentId: resumeAgentAddress,
+        });
+        setResumeFailedRefId(refId);
+      });
     return () => {
       cancelled = true;
     };
-  }, [tenantId, activeWorkbenchId, resumeAgentAddress]);
+  }, [tenantId, activeWorkbenchId, resumeAgentAddress, resumeAttempt]);
+
+  const handleRetryResume = useCallback(() => {
+    setResumeAttempt((attempt) => attempt + 1);
+  }, []);
 
   const { pendingSends, handleSend, retryPendingSend, discardPendingSend } =
     useOptimisticSends({
@@ -1456,6 +1483,12 @@ function ChatWorkspaceInner({
                   />
                   <TurnActivityStrip activity={turnActivity} />
                   <div className="chat-composer-stack">
+                    {resumeFailedRefId !== null ? (
+                      <ResumeFailedBanner
+                        refId={resumeFailedRefId}
+                        onRetry={handleRetryResume}
+                      />
+                    ) : null}
                     {hasUsableModel === false && hasAgentParticipant ? (
                       <NoUsableModelBanner
                         onConnectModel={() => onConnectModel?.()}

packages/chat-ui/src/resume-failed-banner.tsx

@@ -0,0 +1,27 @@
+// CL-6833: mid-turn reopen whose catch-up fetch (`fetchRunningTurn`) fails
+// must not leave the room looking idle. This soft banner names the gap,
+// quotes a `reportError` ref id, and offers Retry — never a silent
+// `.catch(() => undefined)`.
+import { Button } from "@corbits/react-ui";
+import { WarningCircle } from "@corbits/icons";
+import { CHAT_STRINGS } from "./strings";
+
+export function ResumeFailedBanner({
+  refId,
+  onRetry,
+}: {
+  readonly refId: string;
+  readonly onRetry: () => void;
+}) {
+  return (
+    <div className="chat-resume-failed-banner" role="alert">
+      <WarningCircle aria-hidden="true" />
+      <span className="chat-resume-failed-banner-text">
+        {CHAT_STRINGS.resumeFailedNotice(refId)}
+      </span>
+      <Button type="button" variant="outline" size="sm" onClick={onRetry}>
+        {CHAT_STRINGS.resumeFailedRetryAction}
+      </Button>
+    </div>
+  );
+}

packages/chat-ui/src/strings.ts

@@ -277,6 +277,9 @@ export const CHAT_STRINGS = {
   turnActivityThinking: "Thinking…",
   turnActivityRetry: (attempt: number) => `Retrying (attempt ${attempt})…`,
   replyTimedOutNotice: "No reply arrived — the agent may be unavailable.",
+  resumeFailedNotice: (refId: string) =>
+    `Couldn't resume the running reply — try again. (ref ${refId})`,
+  resumeFailedRetryAction: "Retry",
   turnFailedTitle: (sender: string) => `${sender} didn't reply`,
   turnFailedSub: "No reply arrived — the agent may be unavailable.",
   noUsableModelBannerText:

packages/chat-ui/src/styles.css

@@ -1847,6 +1847,31 @@
   flex: 1;
 }
 
+/* CL-6833: catch-up fetch for a still-running turn failed — soft alert
+   above the activity strip so a mid-turn reopen never looks idle. Same
+   visual weight as the no-model banner; role=alert is set in markup. */
+.chat-resume-failed-banner {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  margin: 0 0 0.5rem;
+  padding: 0.4rem 0.6rem;
+  border-radius: var(--ui-radius-md, 0.375rem);
+  background: color-mix(in srgb, var(--destructive) 8%, transparent);
+  color: color-mix(in srgb, var(--destructive) 78%, var(--muted-foreground));
+  font-size: 0.8125rem;
+}
+
+.chat-resume-failed-banner svg {
+  flex-shrink: 0;
+  width: 1rem;
+  height: 1rem;
+}
+
+.chat-resume-failed-banner-text {
+  flex: 1;
+}
+
 .chat-composer {
   position: relative;
   flex-shrink: 0;

packages/chat-ui/test/chat-workspace.test.tsx

@@ -53,6 +53,7 @@ const WORKBENCH_WIRE = {
 function stubFetch(
   sentMessages?: unknown[],
   workbench: typeof WORKBENCH_WIRE = WORKBENCH_WIRE,
+  options: { readonly turnsFail?: boolean } = {},
 ) {
   globalThis.EventSource = StubEventSource as unknown as typeof EventSource;
   globalThis.fetch = (async (input: RequestInfo | URL, init?: RequestInit) => {
@@ -81,6 +82,18 @@ function stubFetch(
     if (/\/chat\/workbenches\/[^/]+\/invitable$/.test(path)) {
       return json({ items: [] });
     }
+    // CL-6380 catch-up: empty list = nothing running. Returning this by
+    // default keeps agent-participant mounts from treating an unstubbed
+    // turns path as a resume failure (CL-6833).
+    if (/\/chat\/workbenches\/[^/]+\/turns(?:\/|$|\?)/.test(path)) {
+      if (options.turnsFail === true) {
+        return new Response(JSON.stringify({ error: "turns unavailable" }), {
+          status: 500,
+          headers: { "content-type": "application/json" },
+        });
+      }
+      return json({ items: [] });
+    }
     if (/\/chat\/workbenches\/[^/]+\/settings$/.test(path)) {
       return json({
         ...workbench,
@@ -1729,6 +1742,96 @@ describe("Workbench header polish (CL-6106)", () => {
   });
 });
 
+describe("CL-6833: running-turn resume failure is visible, never silent idle", () => {
+  test("a failed catch-up fetch shows the resume-failed banner with Retry", async () => {
+    stubFetch(undefined, WORKBENCH_WITH_AGENT_WIRE, { turnsFail: true });
+    const harness = await mount({
+      tenant: { kind: "ready", tenantId: "tnt_1" },
+      workbenchId: "ch_1",
+    });
+    await harness.settle();
+    await harness.settle();
+
+    const banner = harness.container.querySelector(
+      ".chat-resume-failed-banner",
+    );
+    expect(banner).not.toBeNull();
+    expect(banner?.getAttribute("role")).toBe("alert");
+    expect(harness.container.textContent).toContain(
+      "Couldn't resume the running reply",
+    );
+    expect(
+      [...harness.container.querySelectorAll("button")].some(
+        (button) => button.textContent?.trim() === "Retry",
+      ),
+    ).toBe(true);
+    harness.unmount();
+  });
+
+  test("a successful empty catch-up leaves the room without a resume banner", async () => {
+    stubFetch(undefined, WORKBENCH_WITH_AGENT_WIRE);
+    const harness = await mount({
+      tenant: { kind: "ready", tenantId: "tnt_1" },
+      workbenchId: "ch_1",
+    });
+    await harness.settle();
+    await harness.settle();
+
+    expect(
+      harness.container.querySelector(".chat-resume-failed-banner"),
+    ).toBeNull();
+    harness.unmount();
+  });
+
+  test("Retry re-asks the turns endpoint after a resume failure", async () => {
+    let turnsCalls = 0;
+    stubFetch(undefined, WORKBENCH_WITH_AGENT_WIRE, { turnsFail: true });
+    const failingFetch = globalThis.fetch;
+    globalThis.fetch = (async (
+      input: RequestInfo | URL,
+      init?: RequestInit,
+    ) => {
+      const path = typeof input === "string" ? input : String(input);
+      if (/\/chat\/workbenches\/[^/]+\/turns(?:\/|$|\?)/.test(path)) {
+        turnsCalls += 1;
+        if (turnsCalls >= 2) {
+          return new Response(JSON.stringify({ items: [] }), {
+            status: 200,
+            headers: { "content-type": "application/json" },
+          });
+        }
+      }
+      return failingFetch(input, init);
+    }) as typeof fetch;
+
+    const harness = await mount({
+      tenant: { kind: "ready", tenantId: "tnt_1" },
+      workbenchId: "ch_1",
+    });
+    await harness.settle();
+    await harness.settle();
+
+    expect(
+      harness.container.querySelector(".chat-resume-failed-banner"),
+    ).not.toBeNull();
+
+    const retry = [...harness.container.querySelectorAll("button")].find(
+      (button) => button.textContent?.trim() === "Retry",
+    ) as HTMLButtonElement;
+    await act(async () => {
+      retry.click();
+      await sleep(30);
+    });
+    await harness.settle();
+
+    expect(turnsCalls).toBeGreaterThanOrEqual(2);
+    expect(
+      harness.container.querySelector(".chat-resume-failed-banner"),
+    ).toBeNull();
+    harness.unmount();
+  });
+});
+
 describe("switching workbenches never carries a stale root-thread id across", () => {
   // CL-6067/6069 regression, still guarded after CL-6313 made it
   // structurally impossible: the timeline no longer fetches by thread id

packages/chat-ui/test/resume-failed-banner.test.tsx

@@ -0,0 +1,49 @@
+// CL-6833: mid-turn reopen whose catch-up fetch fails must not leave the
+// room looking idle — a visible soft banner with Retry, never a silent
+// swallow of `fetchRunningTurn(...).catch(() => undefined)`.
+import { afterEach, describe, expect, test } from "bun:test";
+import { act } from "react";
+import { createRoot } from "react-dom/client";
+import type { Root } from "react-dom/client";
+
+import { ResumeFailedBanner } from "../src/resume-failed-banner";
+
+let container: HTMLDivElement | null = null;
+let root: Root | null = null;
+
+afterEach(() => {
+  if (root !== null) act(() => root?.unmount());
+  container?.remove();
+  container = null;
+  root = null;
+});
+
+describe("ResumeFailedBanner (CL-6833)", () => {
+  test("names the gap with a quotable ref and offers Retry, never a dead end", async () => {
+    const retries: number[] = [];
+    container = document.createElement("div");
+    document.body.appendChild(container);
+    root = createRoot(container);
+    await act(async () => {
+      root?.render(
+        <ResumeFailedBanner
+          refId="mt4ewrje-zvbmti"
+          onRetry={() => retries.push(1)}
+        />,
+      );
+    });
+
+    const banner = container.querySelector(".chat-resume-failed-banner");
+    expect(banner).not.toBeNull();
+    expect(banner?.getAttribute("role")).toBe("alert");
+    expect(container.textContent).toContain(
+      "Couldn't resume the running reply",
+    );
+    expect(container.textContent).toContain("ref mt4ewrje-zvbmti");
+
+    act(() => {
+      (container?.querySelector("button") as HTMLButtonElement).click();
+    });
+    expect(retries).toEqual([1]);
+  });
+});