diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
index 6c98159e..1d9ab7ff 100644
--- a/.gitea/workflows/ci.yml
+++ b/.gitea/workflows/ci.yml
@@ -145,10 +145,10 @@ jobs:
     # the diagnostic step with its own continue-on-error: true (line 203).
     # Flip confirmed by CI / Platform (Go) status = success on main HEAD 363905d3.
     continue-on-error: false
-    # Job-level ceiling. The go test step below runs with a per-step 10m timeout;
-    # this cap catches any step that leaks past that. Set well above 10m so
+    # Job-level ceiling. The go test step below runs with a per-step 30m timeout;
+    # this cap catches any step that leaks past that. Set well above 30m so
     # the per-step timeout is the active constraint.
-    timeout-minutes: 15
+    timeout-minutes: 35
     defaults:
       run:
         working-directory: workspace-server
@@ -176,12 +176,14 @@ jobs:
         name: Run golangci-lint
         run: $(go env GOPATH)/bin/golangci-lint run --timeout 3m ./...
       - if: always()
-        name: Diagnostic — per-package verbose 60s
+        name: Diagnostic — per-package verbose (300s timeout)
         run: |
           set +e
-          go test -race -v -timeout 60s ./internal/handlers/... 2>&1 | tee /tmp/test-handlers.log
+          # 300s allows handlers + pendinguploads packages to complete on cold
+          # runners with -race instrumentation (~60-120s each vs ~14s non-race).
+          go test -race -v -timeout 300s ./internal/handlers/... 2>&1 | tee /tmp/test-handlers.log
           handlers_exit=$?
-          go test -race -v -timeout 60s ./internal/pendinguploads/... 2>&1 | tee /tmp/test-pu.log
+          go test -race -v -timeout 300s ./internal/pendinguploads/... 2>&1 | tee /tmp/test-pu.log
           pu_exit=$?
           echo "::group::handlers exit=$handlers_exit (last 100 lines)"
           tail -100 /tmp/test-handlers.log
@@ -194,10 +196,10 @@ jobs:
       - if: always()
         name: Run tests with race detection and coverage
         # Explicit timeout: cold runner cache causes OOM kills at ~4m39s on the
-        # full ./... suite with race detection + coverage. A 10m per-step timeout
-        # lets the suite complete on cold cache (~5-7m) while failing cleanly
-        # instead of OOM-killing. The job-level timeout (15m) is a backstop.
-        run: go test -race -timeout 10m -coverprofile=coverage.out ./...
+        # full ./... suite with race detection + coverage. A 30m per-step timeout
+        # lets the suite complete on cold cache (~13-25m) while failing cleanly
+        # instead of OOM-killing. The job-level timeout (35m) is a backstop.
+        run: go test -race -timeout 30m -coverprofile=coverage.out ./...
 
       - if: always()
         name: Per-file coverage report
diff --git a/canvas/src/components/__tests__/AuditTrailPanel.format.test.ts b/canvas/src/components/__tests__/AuditTrailPanel.format.test.ts
new file mode 100644
index 00000000..43a47fbe
--- /dev/null
+++ b/canvas/src/components/__tests__/AuditTrailPanel.format.test.ts
@@ -0,0 +1,55 @@
+// @vitest-environment jsdom
+/**
+ * Tests for formatAuditRelativeTime exported from AuditTrailPanel.
+ */
+import { describe, it, expect } from "vitest";
+import { formatAuditRelativeTime } from "../AuditTrailPanel";
+
+describe("formatAuditRelativeTime", () => {
+  const now = new Date("2026-05-18T12:00:00Z").getTime();
+
+  it('returns "just now" for timestamps less than 60s ago', () => {
+    const ts = new Date(now - 30_000).toISOString(); // 30s ago
+    expect(formatAuditRelativeTime(ts, now)).toBe("just now");
+  });
+
+  it("returns minutes for timestamps under 1h", () => {
+    const ts = new Date(now - 5 * 60_000).toISOString(); // 5m ago
+    expect(formatAuditRelativeTime(ts, now)).toBe("5m ago");
+  });
+
+  it("returns hours for timestamps under 24h", () => {
+    const ts = new Date(now - 3 * 3_600_000).toISOString(); // 3h ago
+    expect(formatAuditRelativeTime(ts, now)).toBe("3h ago");
+  });
+
+  it("returns locale date for timestamps older than 24h", () => {
+    const ts = new Date(now - 2 * 86_400_000).toISOString(); // 2d ago
+    const result = formatAuditRelativeTime(ts, now);
+    // Returns a locale date string; just verify it's a non-empty string
+    expect(typeof result).toBe("string");
+    expect(result.length).toBeGreaterThan(0);
+    expect(result).not.toBe("just now");
+    expect(result).not.toMatch(/m ago$/);
+    expect(result).not.toMatch(/h ago$/);
+  });
+
+  it("handles exactly 60s boundary as minutes", () => {
+    const ts = new Date(now - 60_000).toISOString(); // exactly 1m ago
+    expect(formatAuditRelativeTime(ts, now)).toBe("1m ago");
+  });
+
+  it("handles exactly 3600s boundary as hours", () => {
+    const ts = new Date(now - 3_600_000).toISOString(); // exactly 1h ago
+    expect(formatAuditRelativeTime(ts, now)).toBe("1h ago");
+  });
+
+  it("handles exactly 86400s boundary", () => {
+    const ts = new Date(now - 86_400_000).toISOString(); // exactly 24h ago
+    const result = formatAuditRelativeTime(ts, now);
+    // Exactly 24h should fall into the "days" branch
+    expect(typeof result).toBe("string");
+    expect(result).not.toMatch(/m ago$/);
+    expect(result).not.toMatch(/h ago$/);
+  });
+});
diff --git a/canvas/src/components/__tests__/MemoryInspectorPanel.helpers.test.ts b/canvas/src/components/__tests__/MemoryInspectorPanel.helpers.test.ts
new file mode 100644
index 00000000..c2b2d935
--- /dev/null
+++ b/canvas/src/components/__tests__/MemoryInspectorPanel.helpers.test.ts
@@ -0,0 +1,82 @@
+// @vitest-environment jsdom
+/**
+ * Tests for exported helpers from MemoryInspectorPanel:
+ * isPluginUnavailableError, formatTTL.
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { isPluginUnavailableError, formatTTL } from "../MemoryInspectorPanel";
+
+describe("isPluginUnavailableError", () => {
+  it("returns true when error message contains MEMORY_PLUGIN_URL", () => {
+    const err = new Error("MEMORY_PLUGIN_URL is not configured");
+    expect(isPluginUnavailableError(err)).toBe(true);
+  });
+
+  it("returns false when error message does not contain MEMORY_PLUGIN_URL", () => {
+    const err = new Error("Connection refused");
+    expect(isPluginUnavailableError(err)).toBe(false);
+  });
+
+  it("returns false for non-Error values", () => {
+    expect(isPluginUnavailableError("string error")).toBe(false);
+    expect(isPluginUnavailableError(null)).toBe(false);
+    expect(isPluginUnavailableError(undefined)).toBe(false);
+    expect(isPluginUnavailableError({})).toBe(false);
+  });
+
+  it("handles Error with empty message", () => {
+    expect(isPluginUnavailableError(new Error(""))).toBe(false);
+  });
+});
+
+describe("formatTTL", () => {
+  // Freeze time at 2026-05-18T12:00:00Z for deterministic tests.
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2026-05-18T12:00:00Z"));
+  });
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("returns empty string for null", () => {
+    expect(formatTTL(null)).toBe("");
+  });
+
+  it("returns empty string for undefined", () => {
+    expect(formatTTL(undefined)).toBe("");
+  });
+
+  it("returns empty string for empty string", () => {
+    expect(formatTTL("")).toBe("");
+  });
+
+  it("returns 'expired' for past timestamps", () => {
+    const past = new Date(Date.now() - 60_000).toISOString();
+    expect(formatTTL(past)).toBe("expired");
+  });
+
+  it("returns seconds for sub-minute future TTLs", () => {
+    const future = new Date(Date.now() + 30_000).toISOString();
+    expect(formatTTL(future)).toBe("30s");
+  });
+
+  it("returns minutes for sub-hour future TTLs", () => {
+    const future = new Date(Date.now() + 5 * 60_000).toISOString();
+    expect(formatTTL(future)).toBe("5m");
+  });
+
+  it("returns hours for sub-day future TTLs", () => {
+    const future = new Date(Date.now() + 3 * 3_600_000).toISOString();
+    expect(formatTTL(future)).toBe("3h");
+  });
+
+  it("returns days for TTLs longer than 24h", () => {
+    const future = new Date(Date.now() + 2 * 86_400_000).toISOString();
+    expect(formatTTL(future)).toBe("2d");
+  });
+
+  it("returns empty string for invalid date string", () => {
+    expect(formatTTL("not-a-date")).toBe("");
+  });
+});
diff --git a/canvas/src/components/mobile/MobileChat.tsx b/canvas/src/components/mobile/MobileChat.tsx
index b5940a0e..39b80268 100644
--- a/canvas/src/components/mobile/MobileChat.tsx
+++ b/canvas/src/components/mobile/MobileChat.tsx
@@ -242,6 +242,8 @@ export function MobileChat({
 
   useChatSocket(agentId, {
     onAgentMessage: appendMessageDeduped,
+    // Fan-out user's own outbound message to all sessions (issue #228).
+    onUserMessage: appendMessageDeduped,
     onSendComplete: releaseSendGuards,
   });
 
@@ -748,7 +750,14 @@ export function MobileChat({
               border: "none",
               outline: "none",
               background: "transparent",
-              fontSize: 14.5,
+              // 16px floor: iOS Safari/WebKit auto-zooms the viewport on
+              // focus when a focused field's font-size is < 16px. Anything
+              // below this re-introduces the tap-to-zoom layout jump on the
+              // mobile PWA. Do NOT lower this without also adding a
+              // maximum-scale/user-scalable viewport lock — and that lock
+              // breaks pinch-to-zoom accessibility, so 16px here is the
+              // correct trade.
+              fontSize: 16,
               lineHeight: 1.4,
               color: p.text,
               padding: "6px 0",
diff --git a/canvas/src/components/mobile/__tests__/MobileChat.test.tsx b/canvas/src/components/mobile/__tests__/MobileChat.test.tsx
index 0c8e2459..2ef96e86 100644
--- a/canvas/src/components/mobile/__tests__/MobileChat.test.tsx
+++ b/canvas/src/components/mobile/__tests__/MobileChat.test.tsx
@@ -263,6 +263,20 @@ describe("MobileChat — composer", () => {
     const sendBtn = container.querySelector('[aria-label="Send"]') as HTMLButtonElement;
     expect(sendBtn.disabled).toBe(true);
   });
+
+  // iOS Safari/WebKit auto-zooms the viewport on focus when a focused
+  // <input>/<textarea> has an effective font-size below 16px. On the
+  // mobile PWA this made the whole layout scale up the moment the user
+  // tapped into the chat box. Keeping the composer font ≥16px is the
+  // root-cause fix — it suppresses the focus-zoom WITHOUT disabling
+  // pinch-to-zoom (which a maximum-scale/user-scalable viewport hack
+  // would have done at the cost of accessibility).
+  it("composer textarea font-size is >= 16px (prevents iOS focus-zoom)", () => {
+    const { container } = renderChat(mockAgentId);
+    const textarea = container.querySelector("textarea") as HTMLTextAreaElement;
+    const fontSizePx = parseFloat(textarea.style.fontSize);
+    expect(fontSizePx).toBeGreaterThanOrEqual(16);
+  });
 });
 
 // ─── Tabs ─────────────────────────────────────────────────────────────────────
diff --git a/canvas/src/components/tabs/ChatTab.tsx b/canvas/src/components/tabs/ChatTab.tsx
index d6a9b85c..1cd7056a 100644
--- a/canvas/src/components/tabs/ChatTab.tsx
+++ b/canvas/src/components/tabs/ChatTab.tsx
@@ -143,6 +143,12 @@ function MyChatPanel({ workspaceId, data }: Props) {
         releaseSendGuards();
       }
     },
+    // Fan-out of user's own outbound message to all sessions (issue #228).
+    // Uses appendMessageDeduped so the originating session collapses its
+    // optimistic copy (same role + content within 3-second window).
+    onUserMessage: (msg) => {
+      history.setMessages((prev) => appendMessageDeduped(prev, msg));
+    },
     onActivityLog: (entry) => {
       if (!sending) return;
       setActivityLog((prev) => appendActivityLine(prev, entry));
diff --git a/canvas/src/components/tabs/chat/__tests__/a2aErrorHint.test.ts b/canvas/src/components/tabs/chat/__tests__/a2aErrorHint.test.ts
index 8518829b..ebc35071 100644
--- a/canvas/src/components/tabs/chat/__tests__/a2aErrorHint.test.ts
+++ b/canvas/src/components/tabs/chat/__tests__/a2aErrorHint.test.ts
@@ -64,4 +64,66 @@ describe("inferA2AErrorHint", () => {
     expect(hint).toMatch(/Claude Code SDK/);
     expect(hint).not.toMatch(/proxy timeout/);
   });
+
+  // ---- P1 #348: poll-mode timeout-class detection ----
+
+  it("routes poll-mode budget exhaustion to its specific actionable hint", () => {
+    // a2a_tools_delegation.py emits this exact shape after the 600s
+    // budget. The user must NOT be told to restart — the work is
+    // still in flight on the platform side.
+    const hint = inferA2AErrorHint(
+      "polling timeout after 600s (delegation_id=abc, last_status=processing); the platform is still working on it — call check_task_status('abc') to retrieve later",
+    );
+    expect(hint).toMatch(/Do NOT restart/);
+    expect(hint).toMatch(/check_task_status/);
+  });
+
+  it("matches the check_task_status hint clue even without the 'polling timeout' phrase", () => {
+    const hint = inferA2AErrorHint(
+      "platform busy — call check_task_status('xyz')",
+    );
+    expect(hint).toMatch(/check_task_status/);
+  });
+
+  it("poll-mode hint wins over the generic timeout bucket", () => {
+    // The string contains both "polling timeout after" and "timeout"
+    // — the more-specific poll-mode hint must win so users don't get
+    // the generic "restart" advice for a still-in-flight task.
+    const hint = inferA2AErrorHint("polling timeout after 600s ...");
+    expect(hint).toMatch(/Do NOT restart/);
+    expect(hint).not.toMatch(/restart the workspace if this repeats/);
+  });
+
+  // ---- P1 #348: codex-aware specialization ----
+
+  it("specialises the empty-detail hint for codex callees", () => {
+    // Per feedback_surface_actionable_failure_reason_to_user: opaque
+    // restart prompts are the anti-pattern. With peerKind=codex the
+    // hint explicitly de-recommends restart.
+    const hint = inferA2AErrorHint("", { peerKind: "codex" });
+    expect(hint).toMatch(/codex/);
+    expect(hint).toMatch(/check its Activity tab/i);
+    expect(hint).not.toMatch(/A workspace restart is the safe first move/);
+  });
+
+  it("specialises generic-timeout hint for codex callees", () => {
+    const hint = inferA2AErrorHint("ReadTimeout", { peerKind: "codex" });
+    expect(hint).toMatch(/codex/);
+    expect(hint).toMatch(/600s/);
+  });
+
+  it("falls back to the non-codex generic timeout hint when no peerKind given", () => {
+    const hint = inferA2AErrorHint("ReadTimeout");
+    expect(hint).toMatch(/proxy timeout/);
+    expect(hint).not.toMatch(/600s sync-proxy/);
+  });
+
+  it("preserves existing empty-detail wording when no peer context provided", () => {
+    const hint = inferA2AErrorHint("");
+    expect(hint).toMatch(/no error detail/);
+    // Updated wording: must NOT be the bare "restart is the safe
+    // first move" line — that violates surface-actionable-reason.
+    expect(hint).not.toMatch(/safe first move/);
+    expect(hint).toMatch(/Activity tab/);
+  });
 });
diff --git a/canvas/src/components/tabs/chat/__tests__/message-parser.test.ts b/canvas/src/components/tabs/chat/__tests__/message-parser.test.ts
index 3a4748a7..28780041 100644
--- a/canvas/src/components/tabs/chat/__tests__/message-parser.test.ts
+++ b/canvas/src/components/tabs/chat/__tests__/message-parser.test.ts
@@ -248,6 +248,88 @@ describe("extractResponseText", () => {
   });
 });
 
+describe("extractAgentText", () => {
+  it("extracts text from top-level parts", () => {
+    const task = {
+      parts: [{ kind: "text", text: "Agent said hello" }],
+    };
+    expect(extractAgentText(task)).toBe("Agent said hello");
+  });
+
+  it("extracts from artifacts[0].parts when top-level parts absent", () => {
+    const task = {
+      artifacts: [
+        { parts: [{ kind: "text", text: "From artifact block" }] },
+      ],
+    };
+    expect(extractAgentText(task)).toBe("From artifact block");
+  });
+
+  it("extracts from status.message.parts as fallback", () => {
+    const task = {
+      status: {
+        message: { parts: [{ kind: "text", text: "Status text" }] },
+      },
+    };
+    expect(extractAgentText(task)).toBe("Status text");
+  });
+
+  it("prefers top-level parts over artifacts", () => {
+    const task = {
+      parts: [{ kind: "text", text: "top-level wins" }],
+      artifacts: [
+        { parts: [{ kind: "text", text: "artifact text" }] },
+      ],
+    };
+    expect(extractAgentText(task)).toBe("top-level wins");
+  });
+
+  it("prefers top-level parts over status.message", () => {
+    const task = {
+      parts: [{ kind: "text", text: "parts wins" }],
+      status: {
+        message: { parts: [{ kind: "text", text: "status text" }] },
+      },
+    };
+    expect(extractAgentText(task)).toBe("parts wins");
+  });
+
+  it("returns string identity when task itself is a string", () => {
+    expect(extractAgentText("plain string task" as unknown as Record<string, unknown>)).toBe(
+      "plain string task",
+    );
+  });
+
+  it("returns fallback when task is an empty object", () => {
+    expect(extractAgentText({})).toBe("(Could not extract response text)");
+  });
+
+  it("returns fallback when task has no extractable text", () => {
+    expect(
+      extractAgentText({ status: "running", other: "fields" }),
+    ).toBe("(Could not extract response text)");
+  });
+
+  it("tolerates malformed nested shapes without throwing", () => {
+    const task = {
+      parts: null,
+      artifacts: "not an array",
+      status: { message: 42 },
+    };
+    expect(extractAgentText(task)).toBe("(Could not extract response text)");
+  });
+
+  it("joins multiple text parts with newline", () => {
+    const task = {
+      parts: [
+        { kind: "text", text: "Line one" },
+        { kind: "text", text: "Line two" },
+      ],
+    };
+    expect(extractAgentText(task)).toBe("Line one\nLine two");
+  });
+});
+
 describe("extractTextsFromParts", () => {
   it("extracts text parts with kind=text", () => {
     const parts = [
diff --git a/canvas/src/components/tabs/chat/__tests__/resolveWorkspaceName.test.ts b/canvas/src/components/tabs/chat/__tests__/resolveWorkspaceName.test.ts
new file mode 100644
index 00000000..2f54f9e8
--- /dev/null
+++ b/canvas/src/components/tabs/chat/__tests__/resolveWorkspaceName.test.ts
@@ -0,0 +1,102 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { useCanvasStore } from "@/store/canvas";
+import { resolveWorkspaceName } from "../hooks/resolveWorkspaceName";
+
+beforeEach(() => {
+  // Reset store to a clean slate between tests so node lookup is deterministic.
+  useCanvasStore.setState({ nodes: [] });
+});
+
+describe("resolveWorkspaceName", () => {
+  it("returns the workspace name when a node with that ID exists", () => {
+    useCanvasStore.setState({
+      nodes: [
+        {
+          id: "ws-alpha-001",
+          type: "workspace",
+          data: { name: "Alpha Agent" },
+          position: { x: 0, y: 0 },
+        },
+      ],
+    });
+
+    expect(resolveWorkspaceName("ws-alpha-001")).toBe("Alpha Agent");
+  });
+
+  it("falls back to the first 8 chars of the ID when no matching node exists", () => {
+    expect(resolveWorkspaceName("ws-zzz-not-found")).toBe("ws-zzz-n");
+  });
+
+  it("falls back to the first 8 chars when the node exists but has no name", () => {
+    useCanvasStore.setState({
+      nodes: [
+        {
+          id: "ws-no-name",
+          type: "workspace",
+          // data.name is deliberately absent
+          data: {},
+          position: { x: 0, y: 0 },
+        },
+      ],
+    });
+
+    expect(resolveWorkspaceName("ws-no-name")).toBe("ws-no-na");
+  });
+
+  it("returns the first 8 chars for a very short ID", () => {
+    expect(resolveWorkspaceName("ab")).toBe("ab");
+  });
+
+  it("returns the first 8 chars when the ID is exactly 8 characters", () => {
+    // slice(0,8) of an 8-char string is the full string
+    const id = "12345678";
+    expect(resolveWorkspaceName(id)).toBe(id);
+  });
+
+  it("picks the right node when multiple workspaces share a prefix", () => {
+    useCanvasStore.setState({
+      nodes: [
+        {
+          id: "00000000-0000-0000-0000-000000000001",
+          type: "workspace",
+          data: { name: "Backend Agent" },
+          position: { x: 0, y: 0 },
+        },
+        {
+          id: "00000000-0000-0000-0000-000000000002",
+          type: "workspace",
+          data: { name: "Frontend Agent" },
+          position: { x: 100, y: 0 },
+        },
+      ],
+    });
+
+    expect(resolveWorkspaceName("00000000-0000-0000-0000-000000000002")).toBe(
+      "Frontend Agent"
+    );
+    expect(resolveWorkspaceName("00000000-0000-0000-0000-000000000001")).toBe(
+      "Backend Agent"
+    );
+  });
+
+  it("does not mutate store state between calls", () => {
+    useCanvasStore.setState({
+      nodes: [
+        {
+          id: "stable-id",
+          type: "workspace",
+          data: { name: "Stable Workspace" },
+          position: { x: 0, y: 0 },
+        },
+      ],
+    });
+
+    resolveWorkspaceName("stable-id");
+    resolveWorkspaceName("unknown-id");
+
+    // Store nodes must be unchanged — resolveWorkspaceName is read-only.
+    const nodes = useCanvasStore.getState().nodes;
+    expect(nodes).toHaveLength(1);
+    expect((nodes[0] as { id: string }).id).toBe("stable-id");
+  });
+});
diff --git a/canvas/src/components/tabs/chat/__tests__/useChatSocket.userMessage.test.ts b/canvas/src/components/tabs/chat/__tests__/useChatSocket.userMessage.test.ts
new file mode 100644
index 00000000..73b6ebe1
--- /dev/null
+++ b/canvas/src/components/tabs/chat/__tests__/useChatSocket.userMessage.test.ts
@@ -0,0 +1,216 @@
+// @vitest-environment jsdom
+/**
+ * Tests for USER_MESSAGE event handling in useChatSocket.
+ *
+ * Covers issue #228: a canvas user's own outbound message was not fanned
+ * out to other sessions — the originating session inserted it optimistically,
+ * but other sessions only saw it after a manual refresh.
+ *
+ * The server now broadcasts USER_MESSAGE on canvas message/send. This test
+ * verifies the canvas side consumes and forwards it to onUserMessage.
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { renderHook, act } from "@testing-library/react";
+import React from "react";
+import { useChatSocket, type UseChatSocketCallbacks } from "../hooks/useChatSocket";
+import { emitSocketEvent, _resetSocketEventListenersForTests } from "@/store/socket-events";
+import type { WSMessage } from "@/store/socket";
+
+// Silence React StrictMode double-invoke noise — we care about final state.
+const WARN = console.warn;
+beforeEach(() => { console.warn = () => {}; });
+afterEach(() => { console.warn = WARN; });
+
+beforeEach(() => {
+  _resetSocketEventListenersForTests();
+  vi.useFakeTimers();
+  vi.setSystemTime(new Date("2026-05-18T10:00:00Z"));
+});
+afterEach(() => {
+  vi.useRealTimers();
+  _resetSocketEventListenersForTests();
+});
+
+const WORKSPACE_ID = "00000000-0000-0000-0000-000000000001";
+
+function makeUserMessageEvent(
+  workspaceId: string,
+  overrides: Partial<{
+    message: string;
+    attachments: Array<{ uri: string; name: string; mimeType?: string; size?: number }>;
+    messageId: string;
+  }> = {},
+): WSMessage {
+  const { message = "Hello, agent!", attachments, messageId } = overrides;
+  const payload: Record<string, unknown> = { message };
+  if (attachments) payload.attachments = attachments;
+  if (messageId) payload.messageId = messageId;
+  return {
+    event: "USER_MESSAGE",
+    workspace_id: workspaceId,
+    timestamp: "2026-05-18T10:00:00Z",
+    payload,
+  };
+}
+
+describe("useChatSocket USER_MESSAGE handling", () => {
+  it("calls onUserMessage with a ChatMessage when USER_MESSAGE arrives for matching workspace", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    const { result } = renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(makeUserMessageEvent(WORKSPACE_ID, { message: "Hello!" }));
+    });
+
+    expect(onUserMessage).toHaveBeenCalledTimes(1);
+    const msg = onUserMessage.mock.calls[0][0];
+    expect(msg.role).toBe("user");
+    expect(msg.content).toBe("Hello!");
+    expect(typeof msg.id).toBe("string");
+    expect(msg.timestamp).toBe("2026-05-18T10:00:00.000Z");
+  });
+
+  it("calls onUserMessage with attachments extracted from the payload", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(
+        makeUserMessageEvent(WORKSPACE_ID, {
+          message: "Here is the file",
+          attachments: [
+            { uri: "workspace:/uploads/report.pdf", name: "report.pdf", mimeType: "application/pdf", size: 4096 },
+          ],
+        }),
+      );
+    });
+
+    expect(onUserMessage).toHaveBeenCalledTimes(1);
+    const msg = onUserMessage.mock.calls[0][0];
+    expect(msg.role).toBe("user");
+    expect(msg.content).toBe("Here is the file");
+    expect(msg.attachments).toHaveLength(1);
+    expect(msg.attachments![0].uri).toBe("workspace:/uploads/report.pdf");
+    expect(msg.attachments![0].name).toBe("report.pdf");
+    expect(msg.attachments![0].mimeType).toBe("application/pdf");
+    expect(msg.attachments![0].size).toBe(4096);
+  });
+
+  it("does NOT call onUserMessage when workspace_id does not match", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(
+        makeUserMessageEvent("00000000-0000-0000-0000-000000000099", { message: "wrong workspace" }),
+      );
+    });
+
+    expect(onUserMessage).not.toHaveBeenCalled();
+  });
+
+  it("does NOT call onUserMessage when message is empty and no attachments", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(makeUserMessageEvent(WORKSPACE_ID, { message: "" }));
+    });
+
+    expect(onUserMessage).not.toHaveBeenCalled();
+  });
+
+  it("ignores USER_MESSAGE when onUserMessage callback is undefined", () => {
+    const callbacks: UseChatSocketCallbacks = { onAgentMessage: vi.fn() };
+    // Should not throw — undefined callback is guarded
+    expect(() =>
+      renderHook(() => useChatSocket(WORKSPACE_ID, callbacks)),
+    ).not.toThrow();
+
+    const { result } = renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+    act(() => {
+      emitSocketEvent(makeUserMessageEvent(WORKSPACE_ID, { message: "Hello" }));
+    });
+    // No error thrown even without onUserMessage
+  });
+
+  it("other event types do NOT trigger onUserMessage", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent({
+        event: "A2A_RESPONSE",
+        workspace_id: WORKSPACE_ID,
+        timestamp: "2026-05-18T10:00:00Z",
+        payload: {},
+      });
+    });
+
+    expect(onUserMessage).not.toHaveBeenCalled();
+  });
+
+  it("re-fires onUserMessage for each USER_MESSAGE event received", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(makeUserMessageEvent(WORKSPACE_ID, { message: "First message" }));
+    });
+    act(() => {
+      emitSocketEvent(makeUserMessageEvent(WORKSPACE_ID, { message: "Second message" }));
+    });
+
+    expect(onUserMessage).toHaveBeenCalledTimes(2);
+    expect(onUserMessage.mock.calls[0][0].content).toBe("First message");
+    expect(onUserMessage.mock.calls[1][0].content).toBe("Second message");
+  });
+
+  it("handles USER_MESSAGE with messageId in payload", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(
+        makeUserMessageEvent(WORKSPACE_ID, { message: "With ID", messageId: "msg-id-abc" }),
+      );
+    });
+
+    expect(onUserMessage).toHaveBeenCalledTimes(1);
+    const msg = onUserMessage.mock.calls[0][0];
+    expect(msg.content).toBe("With ID");
+  });
+
+  it("filters out attachments with empty uri or name (defence-in-depth)", () => {
+    const onUserMessage = vi.fn();
+    const callbacks: UseChatSocketCallbacks = { onUserMessage };
+    renderHook(() => useChatSocket(WORKSPACE_ID, callbacks));
+
+    act(() => {
+      emitSocketEvent(
+        makeUserMessageEvent(WORKSPACE_ID, {
+          message: "Mixed attachments",
+          attachments: [
+            { uri: "workspace:/uploads/good.pdf", name: "good.pdf" },
+            { uri: "", name: "bad.pdf" }, // empty uri — dropped
+            { uri: "workspace:/uploads/also-bad", name: "" }, // empty name — dropped
+            { uri: "workspace:/uploads/also-good.txt", name: "also-good.txt" },
+          ],
+        }),
+      );
+    });
+
+    expect(onUserMessage).toHaveBeenCalledTimes(1);
+    const msg = onUserMessage.mock.calls[0][0];
+    expect(msg.attachments).toHaveLength(2);
+    expect(msg.attachments![0].name).toBe("good.pdf");
+    expect(msg.attachments![1].name).toBe("also-good.txt");
+  });
+});
diff --git a/canvas/src/components/tabs/chat/a2aErrorHint.ts b/canvas/src/components/tabs/chat/a2aErrorHint.ts
index e29e643a..7096a2bc 100644
--- a/canvas/src/components/tabs/chat/a2aErrorHint.ts
+++ b/canvas/src/components/tabs/chat/a2aErrorHint.ts
@@ -10,10 +10,37 @@
  * had already drifted (Activity tab gained `not found`/`offline`
  * cases AgentCommsPanel never picked up) — this module is the merged
  * superset and the only place hint text should change.
+ *
+ * Optional `context.peerKind` lets callers signal "the callee was a
+ * codex-runtime task" so the timeout-class hints can be more specific
+ * about expected long completion times (PM-coordinating-Researcher is
+ * the canonical case where the 600s sync-proxy budget is too tight).
  */
-export function inferA2AErrorHint(detail: string): string {
+export interface A2AErrorContext {
+  /** Runtime of the callee, when known. e.g. "codex", "claude-code". */
+  peerKind?: string;
+}
+
+export function inferA2AErrorHint(
+  detail: string,
+  context?: A2AErrorContext,
+): string {
   const t = detail.toLowerCase();
 
+  // Poll-mode budget exhaustion (a2a_tools_delegation.py emits
+  // "polling timeout after Ns ... call check_task_status(...) to
+  // retrieve later"). This is NOT a delivery failure — the work is
+  // still in flight on the platform side. Route to a specific hint
+  // BEFORE the generic timeout bucket so the user gets the actionable
+  // "wait + check_task_status" guidance instead of the misleading
+  // "restart the workspace" anti-pattern.
+  if (
+    t.includes("polling timeout after") ||
+    t.includes("call check_task_status")
+  ) {
+    return "The 600s sync-polling budget expired but the platform is still working on the delegation. Do NOT restart — the work isn't lost. Wait, then call check_task_status with the delegation_id to retrieve the result. If the callee is a long-running codex task, this is expected.";
+  }
+
   // "control request timeout" is the specific Claude Code SDK init
   // wedge symptom. Pattern on the full phrase, not bare "initialize"
   // — a user task containing "failed to initialize database" would
@@ -27,6 +54,13 @@ export function inferA2AErrorHint(detail: string): string {
     t.includes("deadline exceeded") ||
     t.includes("timeout")
   ) {
+    // For codex callees, a 600s sync-proxy timeout is the EXPECTED
+    // shape when the task is genuinely long-running. Calling out the
+    // workspace-restart anti-pattern explicitly per
+    // `feedback_surface_actionable_failure_reason_to_user`.
+    if ((context?.peerKind || "").toLowerCase() === "codex") {
+      return "The codex remote agent didn't respond within the 600s sync-proxy timeout. Codex tasks can legitimately run longer than this — check the callee's Activity tab; the work may still be progressing. Restart only if the container is genuinely stuck (no activity for several minutes).";
+    }
     return "The remote agent didn't respond within the proxy timeout. It may be busy with a long task, or the runtime is stuck — restart the workspace if this repeats.";
   }
   if (
@@ -48,7 +82,16 @@ export function inferA2AErrorHint(detail: string): string {
     return "The remote workspace can't be reached — it may be stopped, removed, or outside the access control list. Verify the peer is online before retrying.";
   }
   if (detail === "") {
-    return "The remote agent returned no error detail (the underlying httpx exception had an empty message — typically a connection-reset or silent timeout). A workspace restart is the safe first move.";
+    // Per `feedback_surface_actionable_failure_reason_to_user`: a bare
+    // "restart the workspace" prompt is the anti-pattern when the
+    // underlying failure was a silent timeout against a long-running
+    // remote (codex Researcher being coordinated by PM is the
+    // canonical case). If the caller knows the peer is codex, route
+    // to the more specific hint that explicitly de-recommends restart.
+    if ((context?.peerKind || "").toLowerCase() === "codex") {
+      return "The codex remote agent returned no error detail — most often the 600s sync-proxy budget expired before the task finished. The work may still be progressing on the callee side; check its Activity tab before restarting.";
+    }
+    return "The remote agent returned no error detail (the underlying httpx exception had an empty message — typically a connection-reset or silent timeout). Check the callee's Activity tab to see if work is still in flight before restarting.";
   }
   return "The remote agent reported a delivery failure. Check the workspace logs or try restarting.";
 }
diff --git a/canvas/src/components/tabs/chat/hooks/__tests__/useChatSend.test.tsx b/canvas/src/components/tabs/chat/hooks/__tests__/useChatSend.test.tsx
new file mode 100644
index 00000000..79610461
--- /dev/null
+++ b/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);
+  });
+});
diff --git a/canvas/src/components/tabs/chat/hooks/useChatHistory.ts b/canvas/src/components/tabs/chat/hooks/useChatHistory.ts
index 00a16f67..bf7a16ac 100644
--- a/canvas/src/components/tabs/chat/hooks/useChatHistory.ts
+++ b/canvas/src/components/tabs/chat/hooks/useChatHistory.ts
@@ -2,6 +2,7 @@
 
 import { useCallback, useEffect, useRef, useState } from "react";
 import { api } from "@/lib/api";
+import { subscribeSocketResume } from "@/store/socket-events";
 import { type ChatMessage, appendMessageDeduped as appendMessageDedupedFn } from "../types";
 
 const INITIAL_HISTORY_LIMIT = 10;
@@ -82,6 +83,23 @@ export function useChatHistory(
     loadInitial();
   }, [loadInitial]);
 
+  // Back-fill on socket resume. The singleton WS emits this when it
+  // recovers from a down period (ordinary drop, or — the case this
+  // fixes — a mobile-browser background-suspend that silently killed
+  // the socket while the page was frozen). While the socket was dead
+  // every AGENT_MESSAGE / A2A_RESPONSE for this thread was missed, and
+  // the store's rehydrate() only re-pulls /workspaces status, not chat.
+  // Re-running loadInitial() re-fetches the latest persisted history —
+  // exactly what a navigate-away-and-back (remount) does today, but
+  // without the user having to do it. Shared by desktop ChatTab and
+  // MobileChat (both consume this hook), so the realtime path stays
+  // unified across surfaces rather than forked for mobile.
+  useEffect(() => {
+    return subscribeSocketResume(() => {
+      loadInitial();
+    });
+  }, [loadInitial]);
+
   const loadOlder = useCallback(async () => {
     if (inflightRef.current || !hasMoreRef.current) return;
     const oldest = oldestMessageRef.current;
diff --git a/canvas/src/components/tabs/chat/hooks/useChatSend.ts b/canvas/src/components/tabs/chat/hooks/useChatSend.ts
index dd9951b5..e0efd261 100644
--- a/canvas/src/components/tabs/chat/hooks/useChatSend.ts
+++ b/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,
diff --git a/canvas/src/components/tabs/chat/hooks/useChatSocket.ts b/canvas/src/components/tabs/chat/hooks/useChatSocket.ts
index 15815e9a..8b8bfaeb 100644
--- a/canvas/src/components/tabs/chat/hooks/useChatSocket.ts
+++ b/canvas/src/components/tabs/chat/hooks/useChatSocket.ts
@@ -7,6 +7,10 @@ import { createMessage, type ChatMessage } from "../types";
 
 export interface UseChatSocketCallbacks {
   onAgentMessage?: (msg: ChatMessage) => void;
+  /** Called when another session sent a user message — used to fan out
+   *  the user's own outbound text to all sessions so a second device
+   *  sees the question live without a manual refresh (issue #228). */
+  onUserMessage?: (msg: ChatMessage) => void;
   onActivityLog?: (entry: string) => void;
   onSendComplete?: () => void;
   onSendError?: (error: string) => void;
@@ -43,6 +47,33 @@ export function useChatSocket(
 
   useSocketEvent((msg) => {
     try {
+      if (msg.event === "USER_MESSAGE" && msg.workspace_id === workspaceId) {
+        const p = msg.payload || {};
+        const message = typeof p.message === "string" ? p.message : "";
+        const rawAttachments = p.attachments;
+        const attachments =
+          Array.isArray(rawAttachments)
+            ? (rawAttachments as Array<{ uri?: unknown; name?: unknown; mimeType?: unknown; size?: unknown }>)
+                .filter(
+                  (a) =>
+                    typeof a?.uri === "string" && a.uri.length > 0 &&
+                    typeof a?.name === "string" && a.name.length > 0,
+                )
+                .map((a) => ({
+                  uri: a.uri as string,
+                  name: a.name as string,
+                  mimeType: typeof a.mimeType === "string" ? a.mimeType : undefined,
+                  size: typeof a.size === "number" ? a.size : undefined,
+                }))
+            : undefined;
+        if (message || (attachments && attachments.length > 0)) {
+          callbacksRef.current.onUserMessage?.(
+            createMessage("user", message, attachments),
+          );
+        }
+        return;
+      }
+
       if (msg.event === "ACTIVITY_LOGGED") {
         if (msg.workspace_id !== workspaceId) return;
 
@@ -67,9 +98,21 @@ export function useChatSocket(
             const own = (targetId || msg.workspace_id) === workspaceId;
             if (own) {
               callbacksRef.current.onSendComplete?.();
-              callbacksRef.current.onSendError?.(
-                "Agent error (Exception) — see workspace logs for details.",
-              );
+              // internal#211/#212: surface the runtime's curated,
+              // user-actionable reason (provider HTTP status + error
+              // code + the provider's own guidance, e.g. a 403 "org
+              // disabled · use an API key / ask your admin"). The
+              // server now includes error_detail in the ACTIVITY_LOGGED
+              // broadcast; fall back to summary, and only as a last
+              // resort to a generic line. The old hardcoded
+              // "Agent error (Exception) — see workspace logs for
+              // details." string pointed at a logs UI that does not
+              // exist and discarded the actionable reason entirely.
+              const detail =
+                (p.error_detail as string) ||
+                (p.summary as string) ||
+                "The agent turn failed but the runtime reported no detail. Retry once; if it repeats the workspace runtime may need a restart.";
+              callbacksRef.current.onSendError?.(detail);
             }
           }
         } else if (type === "a2a_send") {
diff --git a/canvas/src/hooks/__tests__/useKeyboardShortcut.test.tsx b/canvas/src/hooks/__tests__/useKeyboardShortcut.test.tsx
new file mode 100644
index 00000000..dc8ebccc
--- /dev/null
+++ b/canvas/src/hooks/__tests__/useKeyboardShortcut.test.tsx
@@ -0,0 +1,166 @@
+// @vitest-environment jsdom
+/**
+ * Tests for useKeyboardShortcut.
+ *
+ * Strategy: use renderHook from @testing-library/react so useEffect fires
+ * before dispatch.  We spy on window.addEventListener to capture the registered
+ * handler.  Events are dispatched by calling the captured handler directly
+ * with a KeyboardEvent that has metaKey/ctrlKey overridden via
+ * Object.defineProperty (jsdom's built-in modifier-key event is unreliable).
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { cleanup, act, renderHook } from "@testing-library/react";
+import { useState, useCallback } from "react";
+import { useKeyboardShortcut } from "../use-keyboard-shortcut";
+
+afterEach(cleanup);
+
+// Capture the most-recently registered keydown handler so tests can dispatch through it.
+let registeredHandler: ((e: KeyboardEvent) => void) | null = null;
+
+const addSpy = vi.spyOn(window, "addEventListener").mockImplementation(
+  (event: string, handler: EventListener) => {
+    if (event === "keydown") {
+      registeredHandler = handler as (e: KeyboardEvent) => void;
+    }
+  },
+);
+
+const removeSpy = vi.spyOn(window, "removeEventListener").mockImplementation(
+  (event: string) => {
+    if (event === "keydown") {
+      registeredHandler = null;
+    }
+  },
+);
+
+beforeEach(() => {
+  registeredHandler = null;
+  addSpy.mockClear();
+  removeSpy.mockClear();
+});
+
+/**
+ * Dispatch a keydown event through the captured handler.
+ * Wrapped in act() so React flushes any state updates synchronously.
+ * Bypasses jsdom's internal event routing (which doesn't go through
+ * window.EventTarget.prototype.addEventListener for fireEvent dispatch).
+ */
+function dispatchKeydown(
+  key: string,
+  { meta = false, ctrl = false }: { meta?: boolean; ctrl?: boolean } = {},
+) {
+  act(() => {
+    const e = new KeyboardEvent("keydown", { key, bubbles: true });
+    Object.defineProperty(e, "metaKey", { value: meta });
+    Object.defineProperty(e, "ctrlKey", { value: ctrl });
+    registeredHandler?.(e);
+  });
+}
+
+describe("useKeyboardShortcut", () => {
+  describe("enabled=false", () => {
+    it("does not register a keydown listener", () => {
+      renderHook(() =>
+        useKeyboardShortcut("k", vi.fn(), { enabled: false }),
+      );
+      expect(addSpy).not.toHaveBeenCalledWith("keydown", expect.any(Function));
+    });
+  });
+
+  describe("meta modifier", () => {
+    it("fires callback on Cmd+K", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { meta: true }));
+      dispatchKeydown("k", { meta: true });
+      expect(cb).toHaveBeenCalledTimes(1);
+    });
+
+    it("does NOT fire on Ctrl+K when only meta=true", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { meta: true }));
+      dispatchKeydown("k", { ctrl: true });
+      expect(cb).not.toHaveBeenCalled();
+    });
+
+    it("does NOT fire on plain K even with meta=true", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { meta: true }));
+      dispatchKeydown("k", { meta: false, ctrl: false });
+      expect(cb).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("ctrl modifier", () => {
+    it("fires callback on Ctrl+K", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { ctrl: true }));
+      dispatchKeydown("k", { ctrl: true });
+      expect(cb).toHaveBeenCalledTimes(1);
+    });
+
+    it("does NOT fire on Cmd+K when only ctrl=true", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { ctrl: true }));
+      dispatchKeydown("k", { meta: true });
+      expect(cb).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("no-modifier guard", () => {
+    it("does not fire when no modifier is held", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, {}));
+      dispatchKeydown("k", { meta: false, ctrl: false });
+      expect(cb).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("key mismatch", () => {
+    it("does not fire when wrong key is pressed", () => {
+      const cb = vi.fn();
+      renderHook(() => useKeyboardShortcut("k", cb, { meta: true }));
+      dispatchKeydown("j", { meta: true });
+      expect(cb).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("count reflects shortcut fires", () => {
+    it("increments when Cmd+K fires", () => {
+      const { result } = renderHook(() => {
+        const [count, setCount] = useState(0);
+        const cb = useCallback(() => setCount((c) => c + 1), []);
+        useKeyboardShortcut("k", cb, { meta: true });
+        return count;
+      });
+      expect(result.current).toBe(0);
+      dispatchKeydown("k", { meta: true });
+      expect(result.current).toBe(1);
+      dispatchKeydown("k", { meta: true });
+      expect(result.current).toBe(2);
+    });
+
+    it("does not increment on wrong modifier", () => {
+      const { result } = renderHook(() => {
+        const [count, setCount] = useState(0);
+        const cb = useCallback(() => setCount((c) => c + 1), []);
+        useKeyboardShortcut("k", cb, { meta: true });
+        return count;
+      });
+      dispatchKeydown("k", { ctrl: true }); // wrong modifier
+      expect(result.current).toBe(0);
+    });
+  });
+
+  describe("cleanup on unmount", () => {
+    it("removes the keydown listener on unmount", () => {
+      const cb = vi.fn();
+      const { unmount } = renderHook(() =>
+        useKeyboardShortcut("k", cb, { meta: true }),
+      );
+      expect(removeSpy).not.toHaveBeenCalled();
+      unmount();
+      expect(removeSpy).toHaveBeenCalledWith("keydown", expect.any(Function));
+    });
+  });
+});
diff --git a/canvas/src/hooks/__tests__/useSocketEvent.test.tsx b/canvas/src/hooks/__tests__/useSocketEvent.test.tsx
new file mode 100644
index 00000000..bcf7213a
--- /dev/null
+++ b/canvas/src/hooks/__tests__/useSocketEvent.test.tsx
@@ -0,0 +1,84 @@
+// @vitest-environment jsdom
+/**
+ * Tests for useSocketEvent.
+ *
+ * Covers:
+ *   - subscribeSocketEvents is called on mount
+ *   - Unsubscribe is called on unmount
+ *   - subscribeSocketEvents is called only once (ref-based, not render-based)
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { render, cleanup } from "@testing-library/react";
+import React from "react";
+import { useSocketEvent } from "../useSocketEvent";
+
+afterEach(cleanup);
+
+// Mutable ref shared between vi.mock factory and test helpers
+const state = {
+  handler: null as ((msg: unknown) => void) | null,
+  unsubscribe: null as (() => void) | null,
+};
+
+// Module-level mock — factory uses the state object so beforeEach can update it
+vi.mock("@/store/socket-events", () => ({
+  subscribeSocketEvents: vi.fn().mockImplementation(() => {
+    if (state.unsubscribe) return state.unsubscribe;
+    const fn = vi.fn();
+    state.unsubscribe = fn;
+    return fn;
+  }),
+}));
+
+import { subscribeSocketEvents } from "@/store/socket-events";
+
+beforeEach(() => {
+  state.handler = null;
+  state.unsubscribe = null;
+  vi.mocked(subscribeSocketEvents).mockImplementation(() => {
+    const fn = vi.fn();
+    state.unsubscribe = fn;
+    return fn;
+  });
+});
+
+// Dispatch a message through the subscribed handler
+function dispatchMsg(msg: unknown) {
+  if (state.handler) {
+    state.handler(msg);
+  }
+}
+
+// Consumer component that stores the handler ref
+function SocketConsumer({ cb }: { cb: (msg: unknown) => void }) {
+  useSocketEvent(cb as (msg: unknown) => void);
+  // Store the handler so tests can dispatch through it
+  // We do this by re-mocking to capture the handler
+  return <div data-testid="consumer" />;
+}
+
+describe("useSocketEvent", () => {
+  it("calls subscribeSocketEvents on mount", () => {
+    render(<SocketConsumer cb={vi.fn()} />);
+    expect(subscribeSocketEvents).toHaveBeenCalledTimes(1);
+  });
+
+  it("calls the unsubscribe function on unmount", () => {
+    const unsubscribe = vi.fn();
+    vi.mocked(subscribeSocketEvents).mockReturnValueOnce(unsubscribe);
+    const { unmount } = render(<SocketConsumer cb={vi.fn()} />);
+    unmount();
+    expect(unsubscribe).toHaveBeenCalledTimes(1);
+  });
+
+  it("subscribeSocketEvents is called only once on re-renders", () => {
+    const { rerender } = render(<SocketConsumer cb={vi.fn()} />);
+    const initial = vi.mocked(subscribeSocketEvents).mock.calls.length;
+
+    rerender(<SocketConsumer cb={vi.fn()} />);
+    rerender(<SocketConsumer cb={vi.fn()} />);
+    rerender(<SocketConsumer cb={vi.fn()} />);
+
+    expect(vi.mocked(subscribeSocketEvents).mock.calls.length).toBe(initial);
+  });
+});
diff --git a/canvas/src/hooks/__tests__/useWorkspaceName.test.tsx b/canvas/src/hooks/__tests__/useWorkspaceName.test.tsx
new file mode 100644
index 00000000..065fa164
--- /dev/null
+++ b/canvas/src/hooks/__tests__/useWorkspaceName.test.tsx
@@ -0,0 +1,98 @@
+// @vitest-environment jsdom
+/**
+ * Tests for useWorkspaceName.
+ *
+ * Tests that the hook correctly resolves workspace IDs to names
+ * using the canvas store's nodes.
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { renderHook, cleanup } from "@testing-library/react";
+import React from "react";
+import { useWorkspaceName } from "../useWorkspaceName";
+
+afterEach(cleanup);
+
+const mockNodes = [
+  { id: "ws-1", data: { name: "Alpha Workspace" } },
+  { id: "ws-2", data: { name: "Beta Workspace" } },
+  { id: "ws-3", data: {} }, // node without name
+  { id: "ws-4", data: { name: "" } }, // empty name
+] as const;
+
+// Stable reference so useCallback deps are stable across re-renders
+const stableNodes = [...mockNodes];
+
+vi.mock("@/store/canvas", () => ({
+  useCanvasStore: Object.assign(
+    vi.fn((selector?: (s: { nodes: typeof stableNodes }) => unknown) => {
+      if (typeof selector === "function") {
+        return selector({ nodes: stableNodes });
+      }
+      return { nodes: stableNodes };
+    }),
+    { getState: vi.fn(() => ({ nodes: stableNodes })) },
+  ),
+}));
+
+import { useCanvasStore } from "@/store/canvas";
+
+beforeEach(() => {
+  vi.mocked(useCanvasStore).mockClear();
+});
+
+describe("useWorkspaceName", () => {
+  it("returns the workspace name for a known ID", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve("ws-1");
+    });
+    expect(result.current).toBe("Alpha Workspace");
+  });
+
+  it("returns the workspace name for another known ID", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve("ws-2");
+    });
+    expect(result.current).toBe("Beta Workspace");
+  });
+
+  it("returns empty string for null", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve(null);
+    });
+    expect(result.current).toBe("");
+  });
+
+  it("falls back to first 8 chars of ID when node has no name", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve("ws-3");
+    });
+    expect(result.current).toBe("ws-3".slice(0, 8));
+  });
+
+  it("falls back to first 8 chars of ID when name is empty string", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve("ws-4");
+    });
+    expect(result.current).toBe("ws-4".slice(0, 8));
+  });
+
+  it("falls back to first 8 chars of ID for unknown workspace", () => {
+    const { result } = renderHook(() => {
+      const resolve = useWorkspaceName();
+      return resolve("ws-999");
+    });
+    expect(result.current).toBe("ws-999".slice(0, 8));
+  });
+
+  it("callback is memoized — same reference across renders", () => {
+    const { result, rerender } = renderHook(() => useWorkspaceName());
+    const first = result.current;
+    rerender();
+    expect(result.current).toBe(first);
+  });
+});
diff --git a/canvas/src/lib/__tests__/cssVar.test.ts b/canvas/src/lib/__tests__/cssVar.test.ts
index 148602f7..6342446b 100644
--- a/canvas/src/lib/__tests__/cssVar.test.ts
+++ b/canvas/src/lib/__tests__/cssVar.test.ts
@@ -1,67 +1,32 @@
 // @vitest-environment jsdom
-/**
- * Tests for cssVar — maps ColorToken to a CSS variable string.
- *
- * Exists for the rare case where an inline style="" or SVG fill needs
- * a token value rather than a Tailwind class. The returned var(--color-foo)
- * string follows the live theme without re-renders.
- */
 import { describe, it, expect } from "vitest";
-import { cssVar } from "../theme";
-import type { ColorToken } from "../theme";
+import { cssVar, type ColorToken } from "../theme";
 
 describe("cssVar", () => {
-  it("returns 'var(--color-surface)' for 'surface'", () => {
-    expect(cssVar("surface")).toBe("var(--color-surface)");
-  });
+  const tokens: ColorToken[] = [
+    "surface", "surface-elevated", "surface-sunken", "surface-card",
+    "line", "line-soft", "ink", "ink-mid", "ink-soft",
+    "accent", "accent-strong", "warm", "good", "bad",
+    "bg", "bg-elev", "bg-card", "line-strong",
+    "ink-mute", "ink-dim", "accent-dim", "plasma", "warn",
+  ];
 
-  it("returns 'var(--color-ink)' for 'ink'", () => {
-    expect(cssVar("ink")).toBe("var(--color-ink)");
-  });
-
-  it("returns 'var(--color-accent)' for 'accent'", () => {
-    expect(cssVar("accent")).toBe("var(--color-accent)");
-  });
-
-  it("returns 'var(--color-good)' for 'good'", () => {
-    expect(cssVar("good")).toBe("var(--color-good)");
-  });
-
-  it("returns 'var(--color-bad)' for 'bad'", () => {
-    expect(cssVar("bad")).toBe("var(--color-bad)");
-  });
-
-  it("returns 'var(--color-warn)' for 'warn'", () => {
-    expect(cssVar("warn")).toBe("var(--color-warn)");
-  });
-
-  it("handles all surface variants", () => {
-    const surfaces: ColorToken[] = ["surface", "surface-elevated", "surface-sunken", "surface-card"];
-    for (const t of surfaces) {
-      expect(cssVar(t)).toBe(`var(--color-${t})`);
+  it("returns a CSS variable string for every colour token", () => {
+    for (const token of tokens) {
+      expect(cssVar(token)).toBe(`var(--color-${token})`);
     }
   });
 
-  it("handles all ink variants", () => {
-    const inks: ColorToken[] = ["ink", "ink-mid", "ink-soft", "ink-mute", "ink-dim"];
-    for (const t of inks) {
-      expect(cssVar(t)).toBe(`var(--color-${t})`);
-    }
+  it("returned string can be used as an inline style value", () => {
+    const el = document.createElement("div");
+    el.style.color = cssVar("ink");
+    el.style.backgroundColor = cssVar("surface");
+    expect(el.style.color).toBe("var(--color-ink)");
+    expect(el.style.backgroundColor).toBe("var(--color-surface)");
   });
 
-  it("handles always-dark tokens", () => {
-    const dark: ColorToken[] = ["bg", "bg-elev", "bg-card", "line-strong", "accent-dim", "plasma"];
-    for (const t of dark) {
-      expect(cssVar(t)).toBe(`var(--color-${t})`);
-    }
-  });
-
-  it("is a pure function — same input always returns same output", () => {
-    const tokens: ColorToken[] = ["surface", "accent", "good", "bad", "warm"];
-    for (const t of tokens) {
-      for (let i = 0; i < 3; i++) {
-        expect(cssVar(t)).toBe(`var(--color-${t})`);
-      }
-    }
+  it("returned string contains the token name verbatim", () => {
+    expect(cssVar("accent-strong")).toContain("accent-strong");
+    expect(cssVar("ink-dim")).toContain("ink-dim");
   });
 });
diff --git a/canvas/src/lib/__tests__/theme-provider.test.tsx b/canvas/src/lib/__tests__/theme-provider.test.tsx
new file mode 100644
index 00000000..8d2b8ddc
--- /dev/null
+++ b/canvas/src/lib/__tests__/theme-provider.test.tsx
@@ -0,0 +1,134 @@
+// @vitest-environment jsdom
+/**
+ * Tests for ThemeProvider and useTheme.
+ *
+ * Uses renderHook so useEffect fires before assertions.
+ * matchMedia is stubbed via Object.defineProperty in beforeEach.
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { render, renderHook, cleanup, act } from "@testing-library/react";
+import React from "react";
+import { ThemeProvider, useTheme } from "../theme-provider";
+
+afterEach(cleanup);
+
+function makeMatcher(prefersDark: boolean) {
+  return {
+    matches: prefersDark,
+    media: "(prefers-color-scheme: dark)",
+    onchange: null,
+    addListener: vi.fn(),
+    removeListener: vi.fn(),
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  };
+}
+
+beforeEach(() => {
+  Object.defineProperty(window, "matchMedia", {
+    writable: true,
+    configurable: true,
+    value: vi.fn().mockImplementation(() => makeMatcher(false)),
+  });
+});
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+describe("useTheme", () => {
+  it("returns noopTheme when no provider is in the tree", () => {
+    const { result } = renderHook(() => useTheme());
+    expect(result.current).toMatchObject({
+      theme: "system",
+      resolvedTheme: "light",
+    });
+    expect(typeof result.current.setTheme).toBe("function");
+  });
+});
+
+describe("ThemeProvider", () => {
+  it("initialises with the initialTheme prop", () => {
+    const { result } = renderHook(() => useTheme(), {
+      wrapper: ({ children }) => (
+        <ThemeProvider initialTheme="dark">{children}</ThemeProvider>
+      ),
+    });
+    expect(result.current).toMatchObject({
+      theme: "dark",
+      resolvedTheme: "dark",
+    });
+    expect(document.documentElement.dataset.theme).toBe("dark");
+  });
+
+  it("reflects system preference when theme=system", () => {
+    Object.defineProperty(window, "matchMedia", {
+      writable: true,
+      configurable: true,
+      value: vi.fn().mockImplementation(() => makeMatcher(true)),
+    });
+
+    const { result } = renderHook(() => useTheme(), {
+      wrapper: ({ children }) => (
+        <ThemeProvider initialTheme="system">{children}</ThemeProvider>
+      ),
+    });
+    expect(result.current).toMatchObject({
+      theme: "system",
+      resolvedTheme: "dark",
+    });
+    expect(document.documentElement.dataset.theme).toBe("dark");
+  });
+
+  it("resolvedTheme follows explicit theme, not system, when theme != system", () => {
+    Object.defineProperty(window, "matchMedia", {
+      writable: true,
+      configurable: true,
+      value: vi.fn().mockImplementation(() => makeMatcher(true)),
+    });
+
+    const { result } = renderHook(() => useTheme(), {
+      wrapper: ({ children }) => (
+        <ThemeProvider initialTheme="light">{children}</ThemeProvider>
+      ),
+    });
+    expect(result.current).toMatchObject({
+      theme: "light",
+      resolvedTheme: "light",
+    });
+    expect(document.documentElement.dataset.theme).toBe("light");
+  });
+
+  it("setTheme updates theme state", () => {
+    let setThemeRef: ((t: string) => void) | null = null;
+
+    const { result } = renderHook(() => {
+      const ctx = useTheme();
+      // Capture setTheme on first render
+      if (!setThemeRef) setThemeRef = ctx.setTheme;
+      return ctx;
+    }, {
+      wrapper: ({ children }) => (
+        <ThemeProvider initialTheme="light">{children}</ThemeProvider>
+      ),
+    });
+
+    expect(result.current.theme).toBe("light");
+
+    act(() => { setThemeRef!("dark"); });
+    expect(result.current.theme).toBe("dark");
+    expect(document.documentElement.dataset.theme).toBe("dark");
+  });
+
+  it("sets document.documentElement.dataset.theme to resolvedTheme on mount", () => {
+    render(
+      <ThemeProvider initialTheme="dark">
+        <div />
+      </ThemeProvider>,
+    );
+    // renderHook already flushed effects; plain render also needs act
+    act(() => {});
+    expect(document.documentElement.dataset.theme).toBe("dark");
+  });
+});
diff --git a/canvas/src/store/__tests__/socket.test.ts b/canvas/src/store/__tests__/socket.test.ts
index ee7f94b7..662c1f6a 100644
--- a/canvas/src/store/__tests__/socket.test.ts
+++ b/canvas/src/store/__tests__/socket.test.ts
@@ -21,12 +21,22 @@ vi.mock("../canvas", () => ({
 class MockWebSocket {
   static instances: MockWebSocket[] = [];
 
+  // Mirror the real WebSocket readyState constants — socket.ts's wake
+  // path reads WebSocket.OPEN / WebSocket.CONNECTING and this.ws.readyState.
+  static readonly CONNECTING = 0;
+  static readonly OPEN = 1;
+  static readonly CLOSING = 2;
+  static readonly CLOSED = 3;
+
   url: string;
   onopen: (() => void) | null = null;
   onmessage: ((event: { data: string }) => void) | null = null;
   onclose: (() => void) | null = null;
   onerror: (() => void) | null = null;
   closeCallCount = 0;
+  // Starts OPEN once triggerOpen runs; tests flip this to simulate a
+  // mobile background-suspend that left a dead/half-open socket.
+  readyState = MockWebSocket.CONNECTING;
 
   constructor(url: string) {
     this.url = url;
@@ -35,10 +45,12 @@ class MockWebSocket {
 
   close() {
     this.closeCallCount++;
+    this.readyState = MockWebSocket.CLOSED;
   }
 
   // Helpers to trigger events in tests
   triggerOpen() {
+    this.readyState = MockWebSocket.OPEN;
     this.onopen?.();
   }
 
@@ -59,6 +71,46 @@ class MockWebSocket {
   }
 }
 
+// ---------------------------------------------------------------------------
+// Minimal DOM stub (vitest environment is 'node' — no window/document).
+// socket.ts's wake-recovery attaches visibilitychange/pageshow/online/
+// focus listeners; under node it self-no-ops via a typeof guard, so to
+// exercise the path we inject just enough of window/document here, the
+// same way WebSocket is stubbed above. Kept tiny on purpose — a single
+// listener registry keyed by event name, plus a settable
+// visibilityState.
+// ---------------------------------------------------------------------------
+
+interface FakeTarget {
+  _l: Record<string, Array<() => void>>;
+  addEventListener: (type: string, fn: () => void) => void;
+  removeEventListener: (type: string, fn: () => void) => void;
+  dispatch: (type: string) => void;
+}
+
+function makeFakeTarget(): FakeTarget {
+  const l: Record<string, Array<() => void>> = {};
+  return {
+    _l: l,
+    addEventListener(type, fn) {
+      (l[type] ||= []).push(fn);
+    },
+    removeEventListener(type, fn) {
+      l[type] = (l[type] || []).filter((f) => f !== fn);
+    },
+    dispatch(type) {
+      for (const fn of l[type] || []) fn();
+    },
+  };
+}
+
+const fakeWindow = makeFakeTarget();
+const fakeDocument = Object.assign(makeFakeTarget(), {
+  visibilityState: "visible" as string,
+});
+(globalThis as unknown as Record<string, unknown>).window = fakeWindow;
+(globalThis as unknown as Record<string, unknown>).document = fakeDocument;
+
 // Install mock WebSocket globally before importing socket module
 (globalThis as unknown as Record<string, unknown>).WebSocket = MockWebSocket;
 
@@ -328,6 +380,153 @@ describe("WebSocket onerror", () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// Wake recovery — mobile background-suspend regression (mobile chat not
+// updating in real time until refresh). Simulates: connect → open →
+// the OS freezes the page and silently kills the WS WITHOUT firing
+// onclose → user returns (visibilitychange / pageshow / online /
+// focus) → assert the dead socket is replaced AND, on the new socket's
+// open, the resume signal fires so chat history back-fills the missed
+// AGENT_MESSAGE / A2A_RESPONSE events.
+// ---------------------------------------------------------------------------
+
+import {
+  subscribeSocketResume,
+  _resetSocketResumeListenersForTests,
+} from "../socket-events";
+
+describe("wake recovery (mobile background-suspend)", () => {
+  beforeEach(() => {
+    _resetSocketResumeListenersForTests();
+    fakeDocument.visibilityState = "visible";
+  });
+
+  function suspendKill(ws: MockWebSocket) {
+    // Mobile background-suspend: the OS tore the transport down but the
+    // page was frozen so onclose never ran. The socket object survives
+    // with a CLOSED readyState and no reconnect was scheduled.
+    ws.readyState = MockWebSocket.CLOSED;
+  }
+
+  it("reconnects on visibilitychange when the socket was silently killed", () => {
+    connectSocket();
+    const ws = getLastWS();
+    ws.triggerOpen();
+    expect(MockWebSocket.instances).toHaveLength(1);
+
+    suspendKill(ws);
+    fakeDocument.dispatch("visibilitychange");
+
+    // A fresh socket must have been created — the stale one is not
+    // reused.
+    expect(MockWebSocket.instances.length).toBeGreaterThan(1);
+  });
+
+  it("does NOT reconnect on visibilitychange while the socket is still healthy", () => {
+    connectSocket();
+    const ws = getLastWS();
+    ws.triggerOpen();
+    expect(MockWebSocket.instances).toHaveLength(1);
+
+    // Healthy OPEN socket + a spurious visibilitychange (e.g. quick tab
+    // peek that never actually suspended) → no churn.
+    fakeDocument.dispatch("visibilitychange");
+    expect(MockWebSocket.instances).toHaveLength(1);
+  });
+
+  it("ignores visibilitychange when the page is hidden (the hide transition)", () => {
+    connectSocket();
+    const ws = getLastWS();
+    ws.triggerOpen();
+    suspendKill(ws);
+
+    fakeDocument.visibilityState = "hidden";
+    fakeDocument.dispatch("visibilitychange");
+    // Hidden → must not reconnect (would defeat the purpose; we only
+    // re-arm when the user is actually looking at the page again).
+    expect(MockWebSocket.instances).toHaveLength(1);
+  });
+
+  it.each(["pageshow", "online", "focus"])(
+    "reconnects on window '%s' after a silent kill",
+    (evt) => {
+      connectSocket();
+      const ws = getLastWS();
+      ws.triggerOpen();
+      suspendKill(ws);
+
+      fakeWindow.dispatch(evt);
+      expect(MockWebSocket.instances.length).toBeGreaterThan(1);
+    },
+  );
+
+  it("emits the resume signal once the recovered socket re-opens (so chat back-fills missed messages)", () => {
+    const onResume = vi.fn();
+    const unsub = subscribeSocketResume(onResume);
+
+    connectSocket();
+    const ws1 = getLastWS();
+    ws1.triggerOpen();
+    // First open must NOT fire resume — the mount-time chat-history
+    // fetch already covers the initial load.
+    expect(onResume).not.toHaveBeenCalled();
+
+    // Background-suspend silently kills the socket, then the user
+    // returns.
+    suspendKill(ws1);
+    fakeDocument.dispatch("visibilitychange");
+
+    // The wake handler force-reconnected; the new socket completing its
+    // handshake is what signals "we recovered from a gap — re-fetch".
+    const ws2 = getLastWS();
+    expect(ws2).not.toBe(ws1);
+    ws2.triggerOpen();
+
+    expect(onResume).toHaveBeenCalledTimes(1);
+    unsub();
+  });
+
+  it("does not emit resume on the very first connect", () => {
+    const onResume = vi.fn();
+    const unsub = subscribeSocketResume(onResume);
+    connectSocket();
+    getLastWS().triggerOpen();
+    expect(onResume).not.toHaveBeenCalled();
+    unsub();
+  });
+
+  it("emits resume after an ordinary onclose-driven reconnect too (desktop path unchanged)", () => {
+    const onResume = vi.fn();
+    const unsub = subscribeSocketResume(onResume);
+
+    connectSocket();
+    const ws1 = getLastWS();
+    ws1.triggerOpen();
+    // Ordinary network drop — onclose fires normally.
+    ws1.triggerClose();
+    vi.advanceTimersByTime(1100); // past the 1s backoff
+    const ws2 = getLastWS();
+    expect(ws2).not.toBe(ws1);
+    ws2.triggerOpen();
+
+    expect(onResume).toHaveBeenCalledTimes(1);
+    unsub();
+  });
+
+  it("detaches wake listeners on disconnect (no reconnect after teardown)", () => {
+    connectSocket();
+    const ws = getLastWS();
+    ws.triggerOpen();
+    disconnectSocket();
+
+    const countAfterDisconnect = MockWebSocket.instances.length;
+    // A wake event after teardown must be inert.
+    fakeDocument.dispatch("visibilitychange");
+    fakeWindow.dispatch("focus");
+    expect(MockWebSocket.instances.length).toBe(countAfterDisconnect);
+  });
+});
+
 // ---------------------------------------------------------------------------
 // Health check (startHealthCheck / stopHealthCheck via onopen / disconnect)
 // ---------------------------------------------------------------------------
diff --git a/canvas/src/store/socket-events.ts b/canvas/src/store/socket-events.ts
index b9b8c549..2d0d2d2e 100644
--- a/canvas/src/store/socket-events.ts
+++ b/canvas/src/store/socket-events.ts
@@ -61,3 +61,53 @@ export function subscribeSocketEvents(listener: Listener): () => void {
 export function _resetSocketEventListenersForTests(): void {
   listeners.clear();
 }
+
+// ---------------------------------------------------------------------------
+// Socket-resume signal
+// ---------------------------------------------------------------------------
+//
+// Fired by the ReconnectingSocket when the WS comes back up AFTER having
+// been down (drop, or a mobile-browser background-suspend that silently
+// killed the socket while the page was frozen). Distinct from the raw
+// event bus above: while the socket was dead the page missed every
+// AGENT_MESSAGE / A2A_RESPONSE, and the store's rehydrate() only re-pulls
+// /workspaces status — it does NOT back-fill chat messages. Components
+// that render a live message thread (desktop ChatTab + MobileChat, both
+// via useChatHistory) subscribe here to re-fetch their history on resume
+// so missed agent replies appear without the user having to navigate
+// away+back or hard-refresh. Shared by desktop and mobile — the recovery
+// is in the singleton socket, not forked per-surface.
+
+type ResumeListener = () => void;
+
+const resumeListeners = new Set<ResumeListener>();
+
+/** Notify every resume subscriber that the socket just recovered from a
+ *  down period. Called by ReconnectingSocket.onopen, but only when the
+ *  open follows a prior loss (not the very first connect — the initial
+ *  mount-time history fetch already covers that). */
+export function emitSocketResume(): void {
+  for (const listener of resumeListeners) {
+    try {
+      listener();
+    } catch (err) {
+      if (typeof console !== "undefined") {
+        console.error("socket-resume listener threw:", err);
+      }
+    }
+  }
+}
+
+/** Register a resume subscriber. Returns an unsubscribe function the
+ *  caller must invoke from its effect cleanup. */
+export function subscribeSocketResume(listener: ResumeListener): () => void {
+  resumeListeners.add(listener);
+  return () => {
+    resumeListeners.delete(listener);
+  };
+}
+
+/** Test-only: drop all resume subscribers. */
+export function _resetSocketResumeListenersForTests(): void {
+  resumeListeners.clear();
+}
diff --git a/canvas/src/store/socket.ts b/canvas/src/store/socket.ts
index 7b2adcd3..574dc058 100644
--- a/canvas/src/store/socket.ts
+++ b/canvas/src/store/socket.ts
@@ -1,6 +1,6 @@
 import { useCanvasStore } from "./canvas";
 import { deriveWsBaseUrl } from "@/lib/ws-url";
-import { emitSocketEvent } from "./socket-events";
+import { emitSocketEvent, emitSocketResume } from "./socket-events";
 
 // If explicit WS_URL is set, use it as-is (may include custom path).
 // Otherwise derive base + append /ws.
@@ -98,9 +98,107 @@ class ReconnectingSocket {
   // caller can fire-and-forget without coordinating.
   private rehydrateInFlight: Promise<void> | null = null;
   private rehydrateDedup = new RehydrateDedup(REHYDRATE_DEDUP_WINDOW_MS);
+  // True once any onopen has fired. Gates the resume signal so the very
+  // first connect doesn't fire it (the mount-time chat-history fetch
+  // already covers the initial load — a resume here would be a wasted
+  // duplicate). Set on the first successful open and stays true.
+  private everConnected = false;
+  // True between a loss (onclose / wake-detected stale socket) and the
+  // next successful onopen. Only when this is set does onopen emit the
+  // resume signal — i.e. we recovered from a real gap during which
+  // AGENT_MESSAGE / A2A_RESPONSE events may have been missed.
+  private wasDown = false;
+  // Bound wake handler. iOS Safari / Chrome-mobile freeze the page and
+  // its timers when the tab is backgrounded or the device locks, and
+  // tear the WS down WITHOUT reliably firing onclose before the freeze.
+  // On thaw nothing re-arms: onclose never ran so no reconnect was
+  // scheduled, and the health-check / fallback-poll intervals were
+  // suspended. The socket is silently dead until a manual refresh. This
+  // handler force-reconnects on any wake signal when the socket isn't
+  // healthy. Stored so disconnect() can detach the listeners.
+  private onWake: (() => void) | null = null;
 
   constructor(url: string) {
     this.url = url;
+    this.installWakeListeners();
+  }
+
+  /** Attach page-lifecycle listeners that force a reconnect when the
+   *  page returns to the foreground / regains connectivity and the
+   *  socket is not OPEN. Shared by desktop and mobile — desktop rarely
+   *  hits the stale-socket path (its onclose fires promptly) so this is
+   *  effectively a no-op there, while mobile depends on it because the
+   *  background-suspend kills the socket without an onclose. */
+  private installWakeListeners() {
+    if (typeof window === "undefined" || typeof document === "undefined") {
+      return;
+    }
+    const wake = () => {
+      if (this.disposed) return;
+      // Only act on a visible page — visibilitychange also fires on the
+      // hide transition, which we must ignore (closing here would defeat
+      // the point).
+      if (
+        typeof document.visibilityState === "string" &&
+        document.visibilityState !== "visible"
+      ) {
+        return;
+      }
+      // Healthy socket → nothing to do. A stale/half-open socket on
+      // mobile reports CLOSED or CLOSING (the OS tore the transport
+      // down); CONNECTING is also unhealthy from the user's POV but a
+      // reconnect attempt is already in flight, so leave it.
+      const live =
+        this.ws !== null &&
+        (this.ws.readyState === WebSocket.OPEN ||
+          this.ws.readyState === WebSocket.CONNECTING);
+      if (live) return;
+      // Tear down any zombie and reconnect immediately. Mark wasDown so
+      // the subsequent onopen emits the resume signal and chat threads
+      // back-fill the messages missed while frozen.
+      this.wasDown = true;
+      this.forceReconnect();
+    };
+    this.onWake = wake;
+    document.addEventListener("visibilitychange", wake);
+    window.addEventListener("pageshow", wake);
+    window.addEventListener("online", wake);
+    window.addEventListener("focus", wake);
+  }
+
+  private removeWakeListeners() {
+    if (!this.onWake) return;
+    if (typeof window !== "undefined" && typeof document !== "undefined") {
+      document.removeEventListener("visibilitychange", this.onWake);
+      window.removeEventListener("pageshow", this.onWake);
+      window.removeEventListener("online", this.onWake);
+      window.removeEventListener("focus", this.onWake);
+    }
+    this.onWake = null;
+  }
+
+  /** Detach the current (presumed dead/stale) socket without routing
+   *  through its onclose, cancel any pending backoff timer, and
+   *  reconnect now. Used by the wake path: the browser already killed
+   *  the transport, so the exponential backoff that onclose would have
+   *  scheduled is both absent and undesirable — the user is looking at
+   *  the page and wants it live immediately. */
+  private forceReconnect() {
+    if (this.disposed) return;
+    if (this.reconnectTimer) {
+      clearTimeout(this.reconnectTimer);
+      this.reconnectTimer = null;
+    }
+    if (this.ws) {
+      this.ws.onopen = null;
+      this.ws.onmessage = null;
+      this.ws.onclose = null;
+      this.ws.onerror = null;
+      try { this.ws.close(); } catch { /* noop */ }
+      this.ws = null;
+    }
+    this.attempt = 0;
+    this.connect();
   }
 
   connect() {
@@ -132,6 +230,18 @@ class ReconnectingSocket {
       this.stopFallbackPoll();
       this.rehydrate();
       this.startHealthCheck();
+      // If this open follows a real loss (drop, or a mobile background-
+      // suspend that the wake handler recovered from), signal resume so
+      // live message threads re-fetch the AGENT_MESSAGE / A2A_RESPONSE
+      // history they missed while the socket was dead — rehydrate()
+      // above only refreshes /workspaces status, not chat. Gate on
+      // everConnected so the very first open (covered by the mount-time
+      // history fetch) doesn't fire a redundant resume.
+      if (this.everConnected && this.wasDown) {
+        emitSocketResume();
+      }
+      this.everConnected = true;
+      this.wasDown = false;
     };
 
     ws.onmessage = (event) => {
@@ -157,6 +267,11 @@ class ReconnectingSocket {
       // corresponds to the WS we just tore down (prevents a stale
       // onclose from a zombie socket from re-arming the loop).
       if (this.disposed || this.ws !== ws) return;
+      // We had a live socket and lost it — mark down so the next onopen
+      // emits the resume signal and chat threads back-fill missed
+      // messages. (The wake path also sets this; setting it here covers
+      // the ordinary network-drop case.)
+      this.wasDown = true;
       this.stopHealthCheck();
       useCanvasStore.getState().setWsStatus("connecting");
       this.startFallbackPoll();
@@ -247,6 +362,7 @@ class ReconnectingSocket {
 
   disconnect() {
     this.disposed = true;
+    this.removeWakeListeners();
     this.stopHealthCheck();
     this.stopFallbackPoll();
     if (this.reconnectTimer) {
diff --git a/scripts/build_runtime_package.py b/scripts/build_runtime_package.py
index 52f57c18..08174da0 100755
--- a/scripts/build_runtime_package.py
+++ b/scripts/build_runtime_package.py
@@ -62,6 +62,7 @@ TOP_LEVEL_MODULES = {
     "a2a_tools_memory",
     "a2a_tools_messaging",
     "a2a_tools_rbac",
+    "a2a_tools_identity",
     "adapter_base",
     "agent",
     "agents_md",
diff --git a/workspace-server/internal/events/types.go b/workspace-server/internal/events/types.go
index a081d46e..787cdb20 100644
--- a/workspace-server/internal/events/types.go
+++ b/workspace-server/internal/events/types.go
@@ -41,8 +41,9 @@ type EventType string
 // scan-friendly as it grows.
 const (
 	// Chat / agent messaging — surfaces in canvas chat panels.
-	EventAgentMessage EventType = "AGENT_MESSAGE"
-	EventA2AResponse  EventType = "A2A_RESPONSE"
+	EventAgentMessage   EventType = "AGENT_MESSAGE"
+	EventA2AResponse   EventType = "A2A_RESPONSE"
+	EventUserMessage    EventType = "USER_MESSAGE"
 	EventActivityLogged EventType = "ACTIVITY_LOGGED"
 	EventChannelMessage EventType = "CHANNEL_MESSAGE"
 
@@ -95,6 +96,7 @@ const (
 var AllEventTypes = []EventType{
 	EventA2AResponse,
 	EventActivityLogged,
+	EventUserMessage,
 	EventAgentAssigned,
 	EventAgentCardUpdated,
 	EventAgentMessage,
diff --git a/workspace-server/internal/events/types_test.go b/workspace-server/internal/events/types_test.go
index bef0ed8b..361f898a 100644
--- a/workspace-server/internal/events/types_test.go
+++ b/workspace-server/internal/events/types_test.go
@@ -41,6 +41,7 @@ func TestAllEventTypes_IsSnapshot(t *testing.T) {
 		"DELEGATION_STATUS",
 		"EXTERNAL_CREDENTIALS_ROTATED",
 		"TASK_UPDATED",
+		"USER_MESSAGE",
 		"WORKSPACE_AWAITING_AGENT",
 		"WORKSPACE_DEGRADED",
 		"WORKSPACE_HEARTBEAT",
diff --git a/workspace-server/internal/handlers/a2a_proxy_helpers.go b/workspace-server/internal/handlers/a2a_proxy_helpers.go
index 08fd2102..98c51bb7 100644
--- a/workspace-server/internal/handlers/a2a_proxy_helpers.go
+++ b/workspace-server/internal/handlers/a2a_proxy_helpers.go
@@ -11,6 +11,7 @@ import (
 	"log"
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/Molecule-AI/molecule-monorepo/platform/internal/db"
@@ -344,6 +345,19 @@ func (h *WorkspaceHandler) logA2ASuccess(ctx context.Context, workspaceID, calle
 			"duration_ms":   durationMs,
 		})
 	}
+
+	// #228: fan user's own outbound message to all sessions of the workspace.
+	// When a canvas user sends a message (callerID == "" and method == "message/send"),
+	// the originating session already inserted it optimistically in useChatSend.
+	// Other sessions see nothing until a manual refresh — this broadcast closes
+	// that gap. The originating session collapses its optimistic copy via the
+	// 3-second appendMessageDeduped window (same role + content = deduped).
+	if callerID == "" && a2aMethod == "message/send" && statusCode < 400 {
+		userPayload := extractCanvasUserMessage(body)
+		if userPayload != nil {
+			h.broadcaster.BroadcastOnly(workspaceID, string(events.EventUserMessage), userPayload)
+		}
+	}
 }
 
 func nilIfEmpty(s string) *string {
@@ -393,6 +407,119 @@ func validateCallerToken(ctx context.Context, c *gin.Context, callerID string) e
 // matching (the wsauth errors are typed for the invalid case).
 var errInvalidCallerToken = errors.New("missing caller auth token")
 
+// canvasUserMessage holds the extracted user message extracted from an
+// A2A canvas request body for broadcasting to other sessions.
+type canvasUserMessage struct {
+	Message   string                               `json:"message,omitempty"`
+	Parts     []map[string]interface{}              `json:"parts,omitempty"`
+	MessageID string                               `json:"messageId,omitempty"`
+	Attachments []map[string]interface{}            `json:"attachments,omitempty"`
+}
+
+// extractCanvasUserMessage parses an A2A JSON-RPC request body and extracts
+// the user-authored text and attachments from a canvas-initiated message/send.
+// Returns nil when the body is not a canvas user message (empty, malformed,
+// or not a message/send from canvas). The returned payload is safe to pass
+// directly to BroadcastOnly — nil fields are omitted from JSON.
+func extractCanvasUserMessage(body []byte) map[string]interface{} {
+	if len(body) == 0 {
+		return nil
+	}
+	var top map[string]json.RawMessage
+	if err := json.Unmarshal(body, &top); err != nil {
+		return nil
+	}
+	// Only handle message/send from canvas
+	var method string
+	if err := json.Unmarshal(top["method"], &method); err != nil || method != "message/send" {
+		return nil
+	}
+	params, ok := top["params"]
+	if !ok {
+		return nil
+	}
+	var paramsMap map[string]json.RawMessage
+	if err := json.Unmarshal(params, &paramsMap); err != nil {
+		return nil
+	}
+	msgRaw, ok := paramsMap["message"]
+	if !ok {
+		return nil
+	}
+	var msg map[string]json.RawMessage
+	if err := json.Unmarshal(msgRaw, &msg); err != nil {
+		return nil
+	}
+
+	// role field: only broadcast user-role messages (canvas users)
+	var role string
+	if err := json.Unmarshal(msg["role"], &role); err != nil || role != "user" {
+		return nil
+	}
+
+	result := make(map[string]interface{})
+
+	// Extract messageId if present
+	var mid string
+	if err := json.Unmarshal(msg["messageId"], &mid); err == nil && mid != "" {
+		result["messageId"] = mid
+	}
+
+	// Extract text from parts — accumulate all text parts into a single string
+	var parts []json.RawMessage
+	if err := json.Unmarshal(msg["parts"], &parts); err == nil {
+		var texts []string
+		var fileAttachments []map[string]interface{}
+		for _, pRaw := range parts {
+			var p map[string]json.RawMessage
+			if err := json.Unmarshal(pRaw, &p); err != nil {
+				continue
+			}
+			var t string
+			if err := json.Unmarshal(p["text"], &t); err == nil && t != "" {
+				texts = append(texts, t)
+			}
+			var fileRaw json.RawMessage
+			if err := json.Unmarshal(p["file"], &fileRaw); err == nil && fileRaw != nil {
+				var f map[string]json.RawMessage
+				if err := json.Unmarshal(fileRaw, &f); err == nil {
+					att := make(map[string]interface{})
+					var s string
+					if err := json.Unmarshal(f["uri"], &s); err == nil {
+						att["uri"] = s
+					}
+					if err := json.Unmarshal(f["name"], &s); err == nil {
+						att["name"] = s
+					}
+					if err := json.Unmarshal(f["mimeType"], &s); err == nil {
+						att["mimeType"] = s
+					}
+					var n float64
+					if err := json.Unmarshal(f["size"], &n); err == nil {
+						att["size"] = n
+					}
+					if len(att) > 0 {
+						fileAttachments = append(fileAttachments, att)
+					}
+				}
+			}
+		}
+		if len(texts) > 0 {
+			// Join with newlines — user may have sent multiple text parts
+			result["message"] = strings.Join(texts, "\n")
+		}
+		if len(fileAttachments) > 0 {
+			result["attachments"] = fileAttachments
+		}
+	}
+
+	// Drop empty payloads
+	if len(result) == 0 {
+		return nil
+	}
+	return result
+}
+
 // extractToolTrace pulls metadata.tool_trace from an A2A JSON-RPC response.
 // Returns nil when absent or malformed — callers can pass it straight through.
 func extractToolTrace(respBody []byte) json.RawMessage {
diff --git a/workspace-server/internal/handlers/a2a_proxy_helpers_user_message_test.go b/workspace-server/internal/handlers/a2a_proxy_helpers_user_message_test.go
new file mode 100644
index 00000000..caf5b1cd
--- /dev/null
+++ b/workspace-server/internal/handlers/a2a_proxy_helpers_user_message_test.go
@@ -0,0 +1,262 @@
+package handlers
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// TestExtractCanvasUserMessage_TextOnly covers the primary path: a canvas user
+// sends a plain text message with no attachments.
+func TestExtractCanvasUserMessage_TextOnly(t *testing.T) {
+	body := []byte(`{
+		"method": "message/send",
+		"params": {
+			"message": {
+				"role": "user",
+				"messageId": "msg-abc-123",
+				"parts": [
+					{"kind": "text", "text": "Hello, agent!"}
+				]
+			}
+		}
+	}`)
+	got := extractCanvasUserMessage(body)
+	if got == nil {
+		t.Fatal("expected non-nil payload for text message")
+	}
+	if got["message"] != "Hello, agent!" {
+		t.Errorf("message = %v, want %q", got["message"], "Hello, agent!")
+	}
+	mid, ok := got["messageId"].(string)
+	if !ok || mid != "msg-abc-123" {
+		t.Errorf("messageId = %v, want %q", got["messageId"], "msg-abc-123")
+	}
+	_, hasAttachments := got["attachments"]
+	if hasAttachments {
+		t.Errorf("unexpected attachments: %v", got["attachments"])
+	}
+}
+
+// TestExtractCanvasUserMessage_FileOnly covers a user message with a file but no text.
+func TestExtractCanvasUserMessage_FileOnly(t *testing.T) {
+	body := []byte(`{
+		"method": "message/send",
+		"params": {
+			"message": {
+				"role": "user",
+				"messageId": "msg-file-456",
+				"parts": [
+					{
+						"kind": "file",
+						"file": {
+							"name": "report.pdf",
+							"uri": "workspace:/uploads/report.pdf",
+							"mimeType": "application/pdf",
+							"size": 4096
+						}
+					}
+				]
+			}
+		}
+	}`)
+	got := extractCanvasUserMessage(body)
+	if got == nil {
+		t.Fatal("expected non-nil payload for file-only message")
+	}
+	if got["message"] != nil {
+		t.Errorf("unexpected message text: %v", got["message"])
+	}
+	attachments, ok := got["attachments"].([]map[string]interface{})
+	if !ok || len(attachments) != 1 {
+		t.Fatalf("attachments = %v, want 1-element array", got["attachments"])
+	}
+	att := attachments[0]
+	if att["uri"] != "workspace:/uploads/report.pdf" {
+		t.Errorf("uri = %v, want %q", att["uri"], "workspace:/uploads/report.pdf")
+	}
+	if att["name"] != "report.pdf" {
+		t.Errorf("name = %v, want %q", att["name"], "report.pdf")
+	}
+	if att["mimeType"] != "application/pdf" {
+		t.Errorf("mimeType = %v, want %q", att["mimeType"], "application/pdf")
+	}
+}
+
+// TestExtractCanvasUserMessage_TextAndFile covers a user message with both text and a file.
+func TestExtractCanvasUserMessage_TextAndFile(t *testing.T) {
+	body := []byte(`{
+		"method": "message/send",
+		"params": {
+			"message": {
+				"role": "user",
+				"parts": [
+					{"kind": "text", "text": "Here is the file:"},
+					{"kind": "text", "text": "see below"},
+					{
+						"kind": "file",
+						"file": {
+							"name": "data.csv",
+							"uri": "workspace:/exports/data.csv",
+							"mimeType": "text/csv",
+							"size": 8192
+						}
+					}
+				]
+			}
+		}
+	}`)
+	got := extractCanvasUserMessage(body)
+	if got == nil {
+		t.Fatal("expected non-nil payload")
+	}
+	// Two text parts are joined with newline
+	if got["message"] != "Here is the file:\nsee below" {
+		t.Errorf("message = %v, want %q", got["message"], "Here is the file:\nsee below")
+	}
+	attachments, ok := got["attachments"].([]map[string]interface{})
+	if !ok || len(attachments) != 1 {
+		t.Fatalf("attachments = %v, want 1-element array", got["attachments"])
+	}
+}
+
+// TestExtractCanvasUserMessage_Malformed covers malformed JSON.
+func TestExtractCanvasUserMessage_Malformed(t *testing.T) {
+	cases := []struct {
+		name string
+		body []byte
+	}{
+		{"not JSON", []byte(`{not valid`)},
+		{"wrong type top-level", []byte(`123`)},
+		{"missing params", []byte(`{"method":"message/send"}`)},
+		{"params not object", []byte(`{"method":"message/send","params":123}`)},
+		{"missing message", []byte(`{"method":"message/send","params":{}}`)},
+		{"message not object", []byte(`{"method":"message/send","params":{"message":123}}`)},
+		{"role missing", []byte(`{"method":"message/send","params":{"message":{"parts":[]}}}`)},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := extractCanvasUserMessage(tc.body); got != nil {
+				t.Errorf("expected nil for %s, got %v", tc.name, got)
+			}
+		})
+	}
+}
+
+// TestExtractCanvasUserMessage_NotUserRole covers agent/workspace callers
+// whose role is not "user" — these should not be broadcast as USER_MESSAGE.
+func TestExtractCanvasUserMessage_NotUserRole(t *testing.T) {
+	cases := []struct {
+		name string
+		body []byte
+	}{
+		{
+			"agent role",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"agent","parts":[{"kind":"text","text":"hello"}]}}}`),
+		},
+		{
+			"assistant role",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"assistant","parts":[{"kind":"text","text":"hello"}]}}}`),
+		},
+		{
+			"empty role",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"","parts":[{"kind":"text","text":"hello"}]}}}`),
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := extractCanvasUserMessage(tc.body); got != nil {
+				t.Errorf("expected nil for role=%s, got %v", tc.name, got)
+			}
+		})
+	}
+}
+
+// TestExtractCanvasUserMessage_NotMessageSend covers non-message/send methods.
+func TestExtractCanvasUserMessage_NotMessageSend(t *testing.T) {
+	cases := []struct {
+		name   string
+		method string
+	}{
+		{"tasks/send", "tasks/send"},
+		{"initialize", "initialize"},
+		{"ping", "ping"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			body, _ := json.Marshal(map[string]interface{}{
+				"method": tc.method,
+				"params": map[string]interface{}{
+					"message": map[string]interface{}{
+						"role":  "user",
+						"parts": []map[string]interface{}{{"kind": "text", "text": "hello"}},
+					},
+				},
+			})
+			if got := extractCanvasUserMessage(body); got != nil {
+				t.Errorf("expected nil for method=%q, got %v", tc.method, got)
+			}
+		})
+	}
+}
+
+// TestExtractCanvasUserMessage_BlankOrEmpty covers text with only whitespace
+// and empty parts arrays.
+func TestExtractCanvasUserMessage_BlankOrEmpty(t *testing.T) {
+	cases := []struct {
+		name string
+		body []byte
+	}{
+		{
+			"empty text part",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"user","parts":[{"kind":"text","text":""}]}}}`),
+		},
+		{
+			"empty parts array",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"user","parts":[]}}}`),
+		},
+		{
+			"whitespace-only text — still included as valid content",
+			[]byte(`{"method":"message/send","params":{"message":{"role":"user","parts":[{"kind":"text","text":"   "}]}}}`),
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := extractCanvasUserMessage(tc.body)
+			if tc.name == "whitespace-only text — still included as valid content" {
+				// Whitespace-only text is valid content — preserve it as-is.
+				// Canvas dedup collapses identical copies; whitespace is not stripped.
+				if got == nil {
+					t.Error("expected non-nil for whitespace-only text")
+				} else if got["message"] != "   " {
+					t.Errorf("message = %q, want %q", got["message"], "   ")
+				}
+				return
+			}
+			if got != nil {
+				t.Errorf("expected nil for %s, got %v", tc.name, got)
+			}
+		})
+	}
+}
+
+// TestExtractCanvasUserMessage_Unicode covers non-ASCII text.
+func TestExtractCanvasUserMessage_Unicode(t *testing.T) {
+	body := []byte(`{
+		"method": "message/send",
+		"params": {
+			"message": {
+				"role": "user",
+				"parts": [
+					{"kind": "text", "text": "こんにちは世界 🌍 日本語"}
+				]
+			}
+		}
+	}`)
+	got := extractCanvasUserMessage(body)
+	if got == nil {
+		t.Fatal("expected non-nil payload for unicode message")
+	}
+	if got["message"] != "こんにちは世界 🌍 日本語" {
+		t.Errorf("message = %v, want %q", got["message"], "こんにちは世界 🌍 日本語")
+	}
+}
diff --git a/workspace-server/internal/handlers/activity.go b/workspace-server/internal/handlers/activity.go
index 56dd7a1b..b10bc753 100644
--- a/workspace-server/internal/handlers/activity.go
+++ b/workspace-server/internal/handlers/activity.go
@@ -691,6 +691,19 @@ func logActivityExec(ctx context.Context, exec activityExecutor, broadcaster eve
 		if respStr != nil {
 			payload["response_body"] = json.RawMessage(respJSON)
 		}
+		// internal#211/#212: error_detail carries the runtime's curated,
+		// user-actionable, secret-safe failure reason (provider HTTP
+		// status + error code + the provider's own guidance, e.g. a 403
+		// "org disabled · use an API key / ask your admin"). It is
+		// already persisted to the DB column above and capped by the
+		// runtime's report_activity helper (4096 chars). Previously it
+		// was dropped from the LIVE broadcast, so the canvas had nothing
+		// to render and fell back to a hardcoded opaque
+		// "Agent error (Exception) — see workspace logs" string. Include
+		// it so the chat bubble shows the real reason in real time.
+		if params.ErrorDetail != nil && *params.ErrorDetail != "" {
+			payload["error_detail"] = *params.ErrorDetail
+		}
 	}
 
 	return func() {
diff --git a/workspace-server/internal/handlers/chat_files.go b/workspace-server/internal/handlers/chat_files.go
index c62a2d04..48f58f10 100644
--- a/workspace-server/internal/handlers/chat_files.go
+++ b/workspace-server/internal/handlers/chat_files.go
@@ -107,10 +107,29 @@ func (h *ChatFilesHandler) WithPendingUploads(storage pendinguploads.Storage, br
 }
 
 // chatUploadMaxBytes caps the full multipart request body so a
-// malicious / runaway client can't OOM the proxy hop. 50 MB matches
-// the workspace-side limit; anything larger is rejected at the
+// malicious / runaway client can't OOM the proxy hop. 100 MB matches
+// the workspace-side total limit; anything larger is rejected at the
 // network boundary before forwarding.
-const chatUploadMaxBytes = 50 * 1024 * 1024
+//
+// SSOT NOTE (issue #1520): this constant is the source of truth for
+// chat upload limits across the platform. Its value is exported to
+// the workspace container at provision time via the env var
+// CHAT_UPLOAD_MAX_TOTAL_BYTES (see
+// workspace_provision_shared.go::applyChatUploadLimits) so the
+// Python runtime cap stays in lock-step. Do NOT change this without
+// updating the per-file cap chatUploadMaxFileBytes below and
+// verifying the env-injection site is unchanged.
+const chatUploadMaxBytes = 100 * 1024 * 1024
+
+// chatUploadMaxFileBytes caps any single multipart part. Mirrors the
+// total cap by default because most chat uploads are a single file;
+// keeping per-file equal to total avoids the surprise of "my 60 MB
+// file fit under the total but got 413'd on per-file". Exported to
+// the workspace container as CHAT_UPLOAD_MAX_FILE_BYTES so the
+// Starlette parser's max_part_size matches and any single part above
+// Starlette's default 1 MiB no longer raises MultiPartException
+// (root cause of issue #1520).
+const chatUploadMaxFileBytes = 100 * 1024 * 1024
 
 // resolveWorkspaceForwardCreds resolves the workspace's URL +
 // platform_inbound_secret for an /internal/* forward, applying
diff --git a/workspace-server/internal/handlers/chat_upload_limits_test.go b/workspace-server/internal/handlers/chat_upload_limits_test.go
new file mode 100644
index 00000000..1d228989
--- /dev/null
+++ b/workspace-server/internal/handlers/chat_upload_limits_test.go
@@ -0,0 +1,63 @@
+package handlers
+
+// chat_upload_limits_test.go — pins the SSOT env-injection contract
+// for chat-upload caps (issue #1520). The Python workspace runtime
+// reads these env vars at module init; drift between the constant in
+// chat_files.go and the env-var name here silently breaks chat upload
+// fleet-wide, so the contract is asserted as a unit test in the same
+// package as the producer.
+
+import (
+	"fmt"
+	"testing"
+)
+
+// applyChatUploadLimits MUST seed both env vars to the byte-count
+// stringification of the Go-side constants. Anything else means a
+// Python-side parser cap that disagrees with the Go-side network cap,
+// which is exactly the drift that shipped #1520.
+func TestApplyChatUploadLimits_DefaultsMatchGoConstants(t *testing.T) {
+	env := map[string]string{}
+	applyChatUploadLimits(env)
+
+	wantFile := fmt.Sprintf("%d", chatUploadMaxFileBytes)
+	if got := env["CHAT_UPLOAD_MAX_FILE_BYTES"]; got != wantFile {
+		t.Errorf("CHAT_UPLOAD_MAX_FILE_BYTES = %q, want %q", got, wantFile)
+	}
+
+	wantTotal := fmt.Sprintf("%d", chatUploadMaxBytes)
+	if got := env["CHAT_UPLOAD_MAX_TOTAL_BYTES"]; got != wantTotal {
+		t.Errorf("CHAT_UPLOAD_MAX_TOTAL_BYTES = %q, want %q", got, wantTotal)
+	}
+}
+
+// Pre-existing values win. A tenant override, plugin mutator, or A/B
+// experiment that already set the env MUST be preserved — the SSOT
+// helper is a defaulting layer, not an override layer.
+func TestApplyChatUploadLimits_PreExistingValuesPreserved(t *testing.T) {
+	env := map[string]string{
+		"CHAT_UPLOAD_MAX_FILE_BYTES":  "1234",
+		"CHAT_UPLOAD_MAX_TOTAL_BYTES": "5678",
+	}
+	applyChatUploadLimits(env)
+
+	if got := env["CHAT_UPLOAD_MAX_FILE_BYTES"]; got != "1234" {
+		t.Errorf("pre-existing CHAT_UPLOAD_MAX_FILE_BYTES overwritten: got %q", got)
+	}
+	if got := env["CHAT_UPLOAD_MAX_TOTAL_BYTES"]; got != "5678" {
+		t.Errorf("pre-existing CHAT_UPLOAD_MAX_TOTAL_BYTES overwritten: got %q", got)
+	}
+}
+
+// The 100 MB minimum is the CTO-directed allowance floor (issue #1520).
+// Pin so a future "tidy up: 100 MB seems large" refactor surfaces here
+// before reverting the user-visible behaviour change.
+func TestChatUploadCaps_MinimumAllowanceFloor(t *testing.T) {
+	const floor = 100 * 1024 * 1024
+	if chatUploadMaxBytes < floor {
+		t.Errorf("chatUploadMaxBytes = %d, below #1520 floor %d", chatUploadMaxBytes, floor)
+	}
+	if chatUploadMaxFileBytes < floor {
+		t.Errorf("chatUploadMaxFileBytes = %d, below #1520 floor %d", chatUploadMaxFileBytes, floor)
+	}
+}
diff --git a/workspace-server/internal/handlers/delegation.go b/workspace-server/internal/handlers/delegation.go
index 3d1b6e5d..06c1eb96 100644
--- a/workspace-server/internal/handlers/delegation.go
+++ b/workspace-server/internal/handlers/delegation.go
@@ -747,6 +747,14 @@ func (h *DelegationHandler) listDelegationsFromLedger(ctx context.Context, works
 			entry["response_preview"] = textutil.TruncateBytes(resultPreview.String, 300)
 		}
 		if errorDetail.Valid && errorDetail.String != "" {
+			// Emit both keys: `error_detail` is the canonical field the
+			// Python poll-mode consumer (a2a_tools_delegation.py:184)
+			// reads from /delegations rows — without it, poll-mode
+			// silently loses the failure reason and falls through to
+			// the generic "delegation failed" string. `error` is kept
+			// for back-compat with existing UI surfaces that read the
+			// shorter name.
+			entry["error_detail"] = errorDetail.String
 			entry["error"] = errorDetail.String
 		}
 		if lastHeartbeat != nil {
@@ -808,6 +816,8 @@ func (h *DelegationHandler) listDelegationsFromActivityLogs(ctx context.Context,
 			entry["delegation_id"] = delegationID
 		}
 		if errorDetail != "" {
+			// Emit both keys per the rename: see listDelegationsFromLedger.
+			entry["error_detail"] = errorDetail
 			entry["error"] = errorDetail
 		}
 		if responseBody != "" {
diff --git a/workspace-server/internal/handlers/delegation_test.go b/workspace-server/internal/handlers/delegation_test.go
index 223b8de7..863f4fd0 100644
--- a/workspace-server/internal/handlers/delegation_test.go
+++ b/workspace-server/internal/handlers/delegation_test.go
@@ -1546,6 +1546,71 @@ func TestListDelegations_LedgerEmptyFallsBackToActivityLogs(t *testing.T) {
 	}
 }
 
+// ---------- ListDelegations: activity_logs failed row emits BOTH error + error_detail ----------
+
+// Field-rename pin (P1 #348 / RFC #2829 PR-2 follow-up): the legacy
+// activity_logs fallback path must also emit `error_detail` alongside
+// the historical `error` key. Without this, poll-mode (which reads
+// `error_detail`) silently loses the failure reason when the ledger
+// is empty and the handler falls back to activity_logs.
+func TestListDelegations_ActivityLogsFailedEmitsBothErrorKeys(t *testing.T) {
+	mock := setupTestDB(t)
+	setupTestRedis(t)
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	// Ledger empty → fall back to activity_logs.
+	mock.ExpectQuery("SELECT d.delegation_id, d.caller_id, d.callee_id, d.task_preview").
+		WithArgs("ws-source").
+		WillReturnRows(sqlmock.NewRows([]string{
+			"delegation_id", "caller_id", "callee_id", "task_preview",
+			"status", "result_preview", "error_detail", "last_heartbeat",
+			"deadline", "created_at", "updated_at",
+		}))
+
+	now := time.Now()
+	activityRows := sqlmock.NewRows([]string{
+		"id", "activity_type", "source_id", "target_id",
+		"summary", "status", "error_detail", "response_body",
+		"delegation_id", "created_at",
+	}).AddRow(
+		"act-failed", "delegate_result", "ws-source", "ws-target",
+		"Delegation failed", "error", "codex runtime timed out", "",
+		"del-failed-002", now,
+	)
+	mock.ExpectQuery("SELECT id, activity_type").
+		WithArgs("ws-source").
+		WillReturnRows(activityRows)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: "ws-source"}}
+	c.Request = httptest.NewRequest("GET", "/workspaces/ws-source/delegations", nil)
+
+	dh.ListDelegations(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var resp []map[string]interface{}
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("failed to parse response: %v", err)
+	}
+	if len(resp) != 1 {
+		t.Fatalf("expected 1 row, got %d", len(resp))
+	}
+	if resp[0]["error"] != "codex runtime timed out" {
+		t.Errorf("expected `error` field set, got %v", resp[0]["error"])
+	}
+	if resp[0]["error_detail"] != "codex runtime timed out" {
+		t.Errorf("expected `error_detail` field set (poll-mode contract), got %v", resp[0]["error_detail"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet sqlmock expectations: %v", err)
+	}
+}
+
 // ---------- ListDelegations: both ledger and activity_logs empty → [] ----------
 
 func TestListDelegations_BothEmptyReturnsEmptyArray(t *testing.T) {
@@ -1744,7 +1809,15 @@ func TestListDelegations_LedgerFailedIncludesErrorDetail(t *testing.T) {
 		t.Errorf("expected status 'failed', got %v", resp[0]["status"])
 	}
 	if resp[0]["error"] != "Callee workspace not reachable" {
-		t.Errorf("expected error detail, got %v", resp[0]["error"])
+		t.Errorf("expected error detail under `error`, got %v", resp[0]["error"])
+	}
+	// Field-rename pin (P1 #348 / RFC #2829 PR-2 follow-up): the
+	// Python poll-mode consumer in a2a_tools_delegation.py:184 reads
+	// `error_detail`, not `error`. Both keys MUST be present so polling
+	// surfaces the real failure reason instead of falling through to
+	// the generic "delegation failed" string.
+	if resp[0]["error_detail"] != "Callee workspace not reachable" {
+		t.Errorf("expected error detail under `error_detail`, got %v", resp[0]["error_detail"])
 	}
 	if err := mock.ExpectationsWereMet(); err != nil {
 		t.Errorf("unmet sqlmock expectations: %v", err)
diff --git a/workspace-server/internal/handlers/plugins_install_test.go b/workspace-server/internal/handlers/plugins_install_test.go
new file mode 100644
index 00000000..06c90878
--- /dev/null
+++ b/workspace-server/internal/handlers/plugins_install_test.go
@@ -0,0 +1,53 @@
+package handlers
+
+// plugins_install_test.go — additional coverage for plugins_install.go.
+//
+// Gaps filled vs. existing test files:
+//   - plugins_install_external_test.go: Install + Uninstall 422 (external runtime) ✓ covered
+//   - plugins_test.go:                 Install 400 (missing source, invalid body, etc.) ✓ covered
+//                                    Uninstall 400 (invalid plugin name, empty name) ✓ covered
+//                                    Download auth gate ✓ covered
+//   - org_import_helpers_test.go:      countWorkspaces, envRequirementKey, sanitizeEnvMembers,
+//                                        flattenAndSortRequirements, collectOrgEnv ✓ covered
+//
+// New test added here:
+//   - Uninstall 503: container not running, no SaaS dispatch.
+//
+// NOTE: validateWorkspaceID is not called inside the Install/Uninstall handlers.
+// UUID validation is the responsibility of the WorkspaceAuth middleware, so no
+// 400 test is needed here for UUID format.
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+// TestPluginUninstall_ContainerNotRunning_Returns503 exercises the 503 path
+// where neither a local Docker container nor a SaaS instance-id dispatch
+// resolves. The handler must return "workspace container not running" — NOT a
+// generic 500 or a misleading 422 (external-runtime) message.
+func TestPluginUninstall_ContainerNotRunning_Returns503(t *testing.T) {
+	// No docker client + no instance-id lookup → falls through to 503.
+	h := NewPluginsHandler(t.TempDir(), nil, nil)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{
+		{Key: "id", Value: "550e8400-e29b-41d4-a716-446655440000"},
+		{Key: "name", Value: "some-plugin"},
+	}
+	c.Request = httptest.NewRequest("DELETE",
+		"/workspaces/550e8400-e29b-41d4-a716-446655440000/plugins/some-plugin", nil)
+
+	h.Uninstall(c)
+
+	require.Equal(t, http.StatusServiceUnavailable, w.Code)
+	var body map[string]string
+	json.Unmarshal(w.Body.Bytes(), &body)
+	require.Equal(t, "workspace container not running", body["error"])
+}
diff --git a/workspace-server/internal/handlers/plugins_listing_test.go b/workspace-server/internal/handlers/plugins_listing_test.go
new file mode 100644
index 00000000..8f9db9be
--- /dev/null
+++ b/workspace-server/internal/handlers/plugins_listing_test.go
@@ -0,0 +1,141 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func TestListRegistry_EmptyDir(t *testing.T) {
+	dir := t.TempDir()
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list, got %d plugins", len(got))
+	}
+}
+
+func TestListRegistry_IgnoresFiles(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "not-a-plugin.txt"), []byte("x"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list (files ignored), got %d", len(got))
+	}
+}
+
+func TestListRegistry_SinglePlugin(t *testing.T) {
+	dir := t.TempDir()
+	pluginDir := filepath.Join(dir, "my-plugin")
+	if err := os.Mkdir(pluginDir, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pluginDir, "plugin.yaml"), []byte("name: my-plugin\nversion: 1.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 plugin, got %d", len(got))
+	}
+	if got[0].Name != "my-plugin" {
+		t.Errorf("expected name 'my-plugin', got %q", got[0].Name)
+	}
+}
+
+func TestListRegistry_FiltersByRuntime(t *testing.T) {
+	dir := t.TempDir()
+	for _, spec := range []struct{ name, yaml string }{
+		{"runtime-a", "name: runtime-a\nruntimes:\n  - claude-code\n"},
+		{"runtime-b", "name: runtime-b\nruntimes:\n  - hermes\n"},
+		{"universal", "name: universal\nversion: 1.0.0\n"},
+	} {
+		pd := filepath.Join(dir, spec.name)
+		if err := os.Mkdir(pd, 0755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte(spec.yaml), 0600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	// Filter to claude-code: runtime-a matches, universal (no runtimes field)
+	// is always included per supportsRuntime semantics.
+	got := h.listRegistryFiltered("claude-code")
+	if len(got) != 2 {
+		t.Fatalf("expected 2 (runtime-a + universal), got %d: %v", len(got), func() []string {
+			ns := make([]string, len(got))
+			for i, p := range got { ns[i] = p.Name }
+			return ns
+		}())
+	}
+}
+
+func TestListRegistry_PluginWithNoRuntimeDeclarations_AlwaysIncluded(t *testing.T) {
+	dir := t.TempDir()
+	pd := filepath.Join(dir, "universal-plugin")
+	if err := os.Mkdir(pd, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte("name: universal-plugin\nversion: 1.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	// When plugin declares no runtimes, it should always be included (try-it).
+	got := h.listRegistryFiltered("any-runtime")
+	if len(got) != 1 {
+		t.Errorf("expected 1 plugin (unspecified runtime), got %d", len(got))
+	}
+}
+
+func TestListRegistry_ReadDirError_ReturnsEmpty(t *testing.T) {
+	h := NewPluginsHandler("/nonexistent/path/for/plugins", nil, nil)
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list on ReadDir error, got %d", len(got))
+	}
+}
+
+func TestListRegistry_HTTPEndpoint(t *testing.T) {
+	dir := t.TempDir()
+	pd := filepath.Join(dir, "test-plugin")
+	if err := os.Mkdir(pd, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte("name: test-plugin\nversion: 2.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest("GET", "/plugins", nil)
+	h.ListRegistry(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var plugins []pluginInfo
+	if err := json.Unmarshal(w.Body.Bytes(), &plugins); err != nil {
+		t.Fatalf("failed to parse JSON: %v", err)
+	}
+	if len(plugins) != 1 {
+		t.Errorf("expected 1 plugin, got %d", len(plugins))
+	}
+	if plugins[0].Name != "test-plugin" {
+		t.Errorf("expected name 'test-plugin', got %q", plugins[0].Name)
+	}
+}
diff --git a/workspace-server/internal/handlers/runtime_registry.go b/workspace-server/internal/handlers/runtime_registry.go
index 0efa2ec0..4ded65ab 100644
--- a/workspace-server/internal/handlers/runtime_registry.go
+++ b/workspace-server/internal/handlers/runtime_registry.go
@@ -86,6 +86,40 @@ var fallbackRuntimes = map[string]struct{}{
 	"mock": {},
 }
 
+// stripJSON5Comments removes // single-line comments from JSON5-formatted
+// data. The Integration Tester appends "// Triggered by <job>" to
+// manifest.json after cloning, which causes json.Unmarshal to fail with
+// "invalid character '/'". This strips trailing and mid-file comments
+// before parsing so Go's strict JSON parser accepts JSON5 files.
+//
+// Handles:
+//   - Standalone comment lines:    // comment
+//   - Trailing comments:          "key": "value", // comment
+//   - Comments inside strings are NOT touched ("http://example.com")
+func stripJSON5Comments(data []byte) []byte {
+	var result []byte
+	inString := false
+	i := 0
+	for i < len(data) {
+		if data[i] == '"' && (i == 0 || data[i-1] != '\\') {
+			inString = !inString
+			result = append(result, data[i])
+			i++
+			continue
+		}
+		if !inString && i+1 < len(data) && data[i] == '/' && data[i+1] == '/' {
+			// Skip to end of line
+			for i < len(data) && data[i] != '\n' {
+				i++
+			}
+			continue
+		}
+		result = append(result, data[i])
+		i++
+	}
+	return result
+}
+
 // loadRuntimesFromManifest builds the runtime allowlist from
 // manifest.json. Each workspace_templates[].name is normalized to its
 // base runtime identifier (strips the `-default` suffix templates
@@ -101,6 +135,9 @@ func loadRuntimesFromManifest(path string) (map[string]struct{}, error) {
 	if err != nil {
 		return nil, err
 	}
+	// Strip JSON5 // comments before parsing. The Integration Tester
+	// appends "// Triggered by <job>" to manifest.json after cloning.
+	data = stripJSON5Comments(data)
 	var m manifestFile
 	if err := json.Unmarshal(data, &m); err != nil {
 		return nil, err
diff --git a/workspace-server/internal/handlers/runtime_registry_test.go b/workspace-server/internal/handlers/runtime_registry_test.go
index 78c2c687..54dedbc6 100644
--- a/workspace-server/internal/handlers/runtime_registry_test.go
+++ b/workspace-server/internal/handlers/runtime_registry_test.go
@@ -8,6 +8,7 @@ package handlers
 //      fallback (tested at the initKnownRuntimes level via integration).
 
 import (
+	"encoding/json"
 	"os"
 	"path/filepath"
 	"testing"
@@ -111,3 +112,133 @@ func keys(m map[string]struct{}) []string {
 	}
 	return out
 }
+
+// ── stripJSON5Comments tests ─────────────────────────────────────────────────
+
+func TestStripJSON5Comments_Standalone(t *testing.T) {
+	// Whitespace before the // is preserved; only the // and its text are removed.
+	// The result is still valid JSON.
+	input := "{\n\t// This is a comment\n\t\"workspace_templates\": []\n}"
+	got := string(stripJSON5Comments([]byte(input)))
+	// Stripping should produce valid JSON: try parsing it
+	var m manifestFile
+	if err := json.Unmarshal([]byte(got), &m); err != nil {
+		t.Errorf("output is not valid JSON: %v\ngot: %q", err, got)
+	}
+	if m.WorkspaceTemplates == nil {
+		t.Error("WorkspaceTemplates field should be present after parsing")
+	}
+}
+
+func TestStripJSON5Comments_Trailing(t *testing.T) {
+	input := `{"key": "value"} // trailing comment`
+	got := string(stripJSON5Comments([]byte(input)))
+	want := `{"key": "value"} `
+	if got != want {
+		t.Errorf("trailing comment:\ngot:  %q\nwant: %q", got, want)
+	}
+}
+
+func TestStripJSON5Comments_URLsPreserved(t *testing.T) {
+	// URLs with // in them must NOT be stripped
+	input := `{"url": "https://example.com/path"}`
+	got := string(stripJSON5Comments([]byte(input)))
+	if got != input {
+		t.Errorf("URL stripped: got %q, want %q", got, input)
+	}
+}
+
+func TestStripJSON5Comments_InlineComment(t *testing.T) {
+	// Whitespace before // is preserved; only the comment text is removed.
+	// Result must be valid JSON.
+	input := "{\n\t\"workspace_templates\": [] // inline comment\n}"
+	got := string(stripJSON5Comments([]byte(input)))
+	var m manifestFile
+	if err := json.Unmarshal([]byte(got), &m); err != nil {
+		t.Errorf("output is not valid JSON: %v\ngot: %q", err, got)
+	}
+}
+
+func TestStripJSON5Comments_IntegrationTesterAppend(t *testing.T) {
+	// Simulates what the Integration Tester does: appends // Triggered by ...
+	// to the end of a valid JSON file.
+	input := `{
+	"workspace_templates": [
+		{"name": "hermes", "repo": "org/hermes"}
+	]
+}
+// Triggered by e2e-test job 12345
+`
+	got := string(stripJSON5Comments([]byte(input)))
+	if got == input {
+		t.Error("Integration Tester comment was NOT stripped")
+	}
+	// After stripping, it should be valid JSON
+	var m manifestFile
+	if err := json.Unmarshal([]byte(got), &m); err != nil {
+		t.Errorf("stripped content is not valid JSON: %v\ngot: %q", err, got)
+	}
+	if len(m.WorkspaceTemplates) != 1 || m.WorkspaceTemplates[0].Name != "hermes" {
+		t.Errorf("workspace_templates not parsed: %+v", m.WorkspaceTemplates)
+	}
+}
+
+func TestStripJSON5Comments_NoComments(t *testing.T) {
+	input := `{"workspace_templates": [{"name": "hermes"}]}`
+	got := string(stripJSON5Comments([]byte(input)))
+	if got != input {
+		t.Errorf("unmodified JSON changed: got %q", got)
+	}
+}
+
+// ── loadRuntimesFromManifest with JSON5 comments ─────────────────────────────
+
+func TestLoadRuntimesFromManifest_WithJSON5TrailingComment(t *testing.T) {
+	// Regression: Integration Tester appends "// Triggered by ..." to manifest.json
+	// after cloning. Before the fix, this caused json.Unmarshal to fail with
+	// "invalid character '/'". After the fix, the comment is stripped first.
+	dir := t.TempDir()
+	path := filepath.Join(dir, "manifest.json")
+	manifest := `{
+		"workspace_templates": [
+			{"name": "hermes", "repo": "org/hermes"},
+			{"name": "claude-code-default", "repo": "org/cc"}
+		]
+	}
+	// Triggered by e2e-test job
+	`
+	if err := os.WriteFile(path, []byte(manifest), 0600); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	got, err := loadRuntimesFromManifest(path)
+	if err != nil {
+		t.Fatalf("loadRuntimesFromManifest with trailing comment: %v", err)
+	}
+	for _, must := range []string{"hermes", "claude-code"} {
+		if _, ok := got[must]; !ok {
+			t.Errorf("expected runtime %q in result: %v", must, keys(got))
+		}
+	}
+}
+
+func TestLoadRuntimesFromManifest_WithInlineJSON5Comment(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "manifest.json")
+	// JSON5 with inline comment
+	manifest := `{
+		// runtime templates
+		"workspace_templates": [
+			{"name": "langgraph", "repo": "org/lg"} // the default
+		]
+	}`
+	if err := os.WriteFile(path, []byte(manifest), 0600); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	got, err := loadRuntimesFromManifest(path)
+	if err != nil {
+		t.Fatalf("loadRuntimesFromManifest with inline comment: %v", err)
+	}
+	if _, ok := got["langgraph"]; !ok {
+		t.Errorf("expected langgraph in result: %v", keys(got))
+	}
+}
diff --git a/workspace-server/internal/handlers/secrets.go b/workspace-server/internal/handlers/secrets.go
index f5313082..3108eb5a 100644
--- a/workspace-server/internal/handlers/secrets.go
+++ b/workspace-server/internal/handlers/secrets.go
@@ -411,9 +411,11 @@ func (h *SecretsHandler) restartAllAffectedByGlobalKey(key string) {
 	var ids []string
 	for rows.Next() {
 		var id string
-		if err := rows.Scan(&id); err == nil {
-			ids = append(ids, id)
+		if err := rows.Scan(&id); err != nil {
+			log.Printf("Global secret %s: scan error listing affected workspace: %v", key, err)
+			continue
 		}
+		ids = append(ids, id)
 	}
 	if err := rows.Err(); err != nil {
 		log.Printf("restartAllAffectedByGlobalKey: iteration error: %v", err)
diff --git a/workspace-server/internal/handlers/workspace_abilities_test.go b/workspace-server/internal/handlers/workspace_abilities_test.go
new file mode 100644
index 00000000..ea912b38
--- /dev/null
+++ b/workspace-server/internal/handlers/workspace_abilities_test.go
@@ -0,0 +1,193 @@
+package handlers
+
+import (
+	"bytes"
+	"database/sql"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/gin-gonic/gin"
+)
+
+// patchReq builds a gin context for a PATCH request to /workspaces/:id/abilities.
+func patchReq(id, body string) (*http.Request, *httptest.ResponseRecorder, *gin.Context) {
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: id}}
+	c.Request = httptest.NewRequest("PATCH", "/workspaces/"+id+"/abilities", bytes.NewBufferString(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+	return c.Request, w, c
+}
+
+func TestPatchAbilities_InvalidWorkspaceID(t *testing.T) {
+	setupTestDB(t)
+
+	// "not-a-uuid" fails validateWorkspaceID
+	_, w, c := patchReq("not-a-uuid", `{"broadcast_enabled":true}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestPatchAbilities_EmptyBody(t *testing.T) {
+	setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000001"
+
+	// Empty JSON object — no ability fields present
+	_, w, c := patchReq(id, `{}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+
+	var resp map[string]string
+	json.Unmarshal(w.Body.Bytes(), &resp)
+	if resp["error"] != "at least one ability field required" {
+		t.Errorf("expected 'at least one ability field required', got %v", resp["error"])
+	}
+}
+
+func TestPatchAbilities_WorkspaceNotFound(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000002"
+
+	// SELECT EXISTS returns false (workspace does not exist)
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(false))
+
+	_, w, c := patchReq(id, `{"broadcast_enabled":true}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Errorf("expected 404, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestPatchAbilities_SetBroadcastEnabledTrue(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000003"
+
+	// SELECT EXISTS → true
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
+	// UPDATE broadcast_enabled = true
+	mock.ExpectExec(`UPDATE workspaces SET broadcast_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, true).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	_, w, c := patchReq(id, `{"broadcast_enabled":true}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+
+	var resp map[string]string
+	json.Unmarshal(w.Body.Bytes(), &resp)
+	if resp["status"] != "updated" {
+		t.Errorf("expected status=updated, got %v", resp["status"])
+	}
+}
+
+func TestPatchAbilities_SetTalkToUserEnabledFalse(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000004"
+
+	// SELECT EXISTS → true
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
+	// UPDATE talk_to_user_enabled = false
+	mock.ExpectExec(`UPDATE workspaces SET talk_to_user_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, false).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	_, w, c := patchReq(id, `{"talk_to_user_enabled":false}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestPatchAbilities_BothFields(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000005"
+
+	// SELECT EXISTS → true
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
+	// UPDATE broadcast_enabled = false
+	mock.ExpectExec(`UPDATE workspaces SET broadcast_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, false).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	// UPDATE talk_to_user_enabled = true
+	mock.ExpectExec(`UPDATE workspaces SET talk_to_user_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, true).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	_, w, c := patchReq(id, `{"broadcast_enabled":false,"talk_to_user_enabled":true}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestPatchAbilities_BroadcastUpdateFails(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000006"
+
+	// SELECT EXISTS → true
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
+	// UPDATE fails
+	mock.ExpectExec(`UPDATE workspaces SET broadcast_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, true).
+		WillReturnError(sql.ErrConnDone)
+
+	_, w, c := patchReq(id, `{"broadcast_enabled":true}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestPatchAbilities_TalkToUserUpdateFails(t *testing.T) {
+	mock := setupTestDB(t)
+	id := "00000000-0000-0000-0000-000000000007"
+
+	// SELECT EXISTS → true
+	mock.ExpectQuery(`SELECT EXISTS\(SELECT 1 FROM workspaces WHERE id = \$1 AND status != 'removed'\)`).
+		WithArgs(id).
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
+	// UPDATE broadcast_enabled skipped (not in payload)
+	// UPDATE talk_to_user_enabled fails
+	mock.ExpectExec(`UPDATE workspaces SET talk_to_user_enabled = \$2, updated_at = now\(\) WHERE id = \$1`).
+		WithArgs(id, false).
+		WillReturnError(sql.ErrConnDone)
+
+	_, w, c := patchReq(id, `{"talk_to_user_enabled":false}`)
+	PatchAbilities(c)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+}
diff --git a/workspace-server/internal/handlers/workspace_broadcast.go b/workspace-server/internal/handlers/workspace_broadcast.go
index 66847566..e4b9e08f 100644
--- a/workspace-server/internal/handlers/workspace_broadcast.go
+++ b/workspace-server/internal/handlers/workspace_broadcast.go
@@ -34,11 +34,13 @@ import (
 
 // BroadcastHandler is constructed once and shared across requests.
 type BroadcastHandler struct {
-	broadcaster *events.Broadcaster
+	broadcaster events.EventEmitter
 }
 
 // NewBroadcastHandler creates a BroadcastHandler.
-func NewBroadcastHandler(b *events.Broadcaster) *BroadcastHandler {
+// The emitter is any EventEmitter — the concrete *Broadcaster in production,
+// or a test double in unit tests.
+func NewBroadcastHandler(b events.EventEmitter) *BroadcastHandler {
 	return &BroadcastHandler{broadcaster: b}
 }
 
diff --git a/workspace-server/internal/handlers/workspace_broadcast_test.go b/workspace-server/internal/handlers/workspace_broadcast_test.go
index 50668643..c662f52a 100644
--- a/workspace-server/internal/handlers/workspace_broadcast_test.go
+++ b/workspace-server/internal/handlers/workspace_broadcast_test.go
@@ -67,7 +67,6 @@ func TestBroadcast_OrgScopedRecipients(t *testing.T) {
 	if w.Code != http.StatusOK {
 		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
 	}
-
 	var resp map[string]interface{}
 	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
 		t.Fatalf("failed to unmarshal response: %v", err)
@@ -206,7 +205,7 @@ func TestBroadcast_Disabled(t *testing.T) {
 	broadcaster := newTestBroadcaster()
 	handler := NewBroadcastHandler(broadcaster)
 
-	senderID := "00000000-0000-0000-0000-000000000001"
+	senderID := "00000000-0000-0000-0000-000000000003"
 	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
 		WithArgs(senderID).
 		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("Disabled Agent", false))
@@ -237,7 +236,7 @@ func TestBroadcast_EmptyOrg_NoRecipients(t *testing.T) {
 	broadcaster := newTestBroadcaster()
 	handler := NewBroadcastHandler(broadcaster)
 
-	senderID := "00000000-0000-0000-0000-000000000001" // org root, only workspace in org
+	senderID := "00000000-0000-0000-0000-000000000004" // org root, only workspace in org
 
 	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
 		WithArgs(senderID).
@@ -297,33 +296,12 @@ func TestBroadcast_InvalidWorkspaceID(t *testing.T) {
 	}
 }
 
-func TestBroadcast_MissingMessage(t *testing.T) {
-	setupTestDB(t)
-	broadcaster := newTestBroadcaster()
-	handler := NewBroadcastHandler(broadcaster)
-
-	w := httptest.NewRecorder()
-	c, _ := gin.CreateTestContext(w)
-	c.Params = gin.Params{{Key: "id", Value: "00000000-0000-0000-0000-000000000001"}}
-	c.Request = httptest.NewRequest("POST", "/workspaces/00000000-0000-0000-0000-000000000001/broadcast", bytes.NewBufferString("{}"))
-	c.Request.Header.Set("Content-Type", "application/json")
-
-	handler.Broadcast(c)
-
-	if w.Code != http.StatusBadRequest {
-		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
-	}
-}
-
-// TestBroadcast_OrgRootLookupFails verifies that if the recursive CTE for
-// finding the org root errors, the handler returns 500 instead of proceeding
-// with an un-scoped query that would broadcast to all orgs.
 func TestBroadcast_OrgRootLookupFails(t *testing.T) {
 	mock := setupTestDB(t)
 	broadcaster := newTestBroadcaster()
 	handler := NewBroadcastHandler(broadcaster)
 
-	senderID := "00000000-0000-0000-0000-000000000001"
+	senderID := "00000000-0000-0000-0000-000000000005"
 
 	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
 		WithArgs(senderID).
@@ -353,16 +331,13 @@ func TestBroadcast_OrgRootLookupFails(t *testing.T) {
 	}
 }
 
-// TestBroadcast_OrgScoped_SelfBroadcastExcluded verifies that broadcasting
-// from a workspace does not send a broadcast_receive to the sender itself
-// (the sender logs broadcast_sent, not broadcast_receive).
 func TestBroadcast_OrgScoped_SelfBroadcastExcluded(t *testing.T) {
 	mock := setupTestDB(t)
 	broadcaster := newTestBroadcaster()
 	handler := NewBroadcastHandler(broadcaster)
 
-	senderID := "00000000-0000-0000-0000-000000000001"
-	peerID := "00000000-0000-0000-0000-000000000002"
+	senderID := "00000000-0000-0000-0000-000000000006"
+	peerID := "00000000-0000-0000-0000-000000000007"
 
 	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
 		WithArgs(senderID).
@@ -399,10 +374,145 @@ func TestBroadcast_OrgScoped_SelfBroadcastExcluded(t *testing.T) {
 	}
 }
 
+// TestBroadcast_RecipientActivityLogFails_SkipsAndContinues: if one recipient's
+// activity_log insert fails, the handler logs the error and continues to the
+// next recipient rather than aborting the whole broadcast.
+func TestBroadcast_RecipientActivityLogFails_SkipsAndContinues(t *testing.T) {
+	mock := setupTestDB(t)
+	broadcaster := newTestBroadcaster()
+	handler := NewBroadcastHandler(broadcaster)
+
+	senderID := "00000000-0000-0000-0000-000000000008"
+	peerA := "00000000-0000-0000-0000-000000000009"
+	peerB := "00000000-0000-0000-0000-00000000000a"
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("Resilient Agent", true))
+
+	mock.ExpectQuery(`WITH RECURSIVE org_chain AS`).
+		WithArgs(senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"root_id"}).AddRow(senderID))
+
+	mock.ExpectQuery(`WITH RECURSIVE org_chain AS`).
+		WithArgs(senderID, senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(peerA).AddRow(peerB))
+
+	// Peer A fails — handler logs and continues
+	mock.ExpectExec(`INSERT INTO activity_logs`).WithArgs(peerA, senderID, sqlmock.AnyArg()).
+		WillReturnError(context.DeadlineExceeded)
+	// Peer B succeeds
+	mock.ExpectExec(`INSERT INTO activity_logs`).WithArgs(peerB, senderID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	// Sender log succeeds
+	mock.ExpectExec(`INSERT INTO activity_logs`).WithArgs(senderID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: senderID}}
+	body := `{"message":"partial delivery"}`
+	c.Request = httptest.NewRequest("POST", "/workspaces/"+senderID+"/broadcast", bytes.NewBufferString(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var resp map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &resp)
+	// Only peerB was delivered
+	if int(resp["delivered"].(float64)) != 1 {
+		t.Errorf("expected delivered=1, got %v", resp["delivered"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet expectations: %v", err)
+	}
+}
+
+// TestBroadcast_SenderActivityLogFails_StillReturns200: if the sender's own
+// broadcast_sent activity_log insert fails, the handler still returns 200
+// so the caller doesn't retry a broadcast that already partially delivered.
+func TestBroadcast_SenderActivityLogFails_StillReturns200(t *testing.T) {
+	mock := setupTestDB(t)
+	broadcaster := newTestBroadcaster()
+	handler := NewBroadcastHandler(broadcaster)
+
+	senderID := "00000000-0000-0000-0000-00000000000b"
+	peerA := "00000000-0000-0000-0000-00000000000c"
+
+	mock.ExpectQuery(`SELECT name, broadcast_enabled FROM workspaces WHERE id = \$1 AND status != 'removed'`).
+		WithArgs(senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"name", "broadcast_enabled"}).AddRow("Log-Fail Agent", true))
+
+	mock.ExpectQuery(`WITH RECURSIVE org_chain AS`).
+		WithArgs(senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"root_id"}).AddRow(senderID))
+
+	mock.ExpectQuery(`WITH RECURSIVE org_chain AS`).
+		WithArgs(senderID, senderID).
+		WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(peerA))
+
+	// Peer log succeeds
+	mock.ExpectExec(`INSERT INTO activity_logs`).WithArgs(peerA, senderID, sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	// Sender log FAILS
+	mock.ExpectExec(`INSERT INTO activity_logs`).WithArgs(senderID, sqlmock.AnyArg()).
+		WillReturnError(context.DeadlineExceeded)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: senderID}}
+	body := `{"message":"log fail test"}`
+	c.Request = httptest.NewRequest("POST", "/workspaces/"+senderID+"/broadcast", bytes.NewBufferString(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200 even on sender log failure, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestBroadcast_MissingMessage(t *testing.T) {
+	setupTestDB(t)
+	broadcaster := newTestBroadcaster()
+	handler := NewBroadcastHandler(broadcaster)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: "00000000-0000-0000-0000-00000000000d"}}
+	c.Request = httptest.NewRequest("POST", "/workspaces/00000000-0000-0000-0000-00000000000d/broadcast", bytes.NewBufferString("{}"))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestBroadcast_MissingBody(t *testing.T) {
+	setupTestDB(t)
+	broadcaster := newTestBroadcaster()
+	handler := NewBroadcastHandler(broadcaster)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: "00000000-0000-0000-0000-00000000000e"}}
+	c.Request = httptest.NewRequest("POST", "/workspaces/00000000-0000-0000-0000-00000000000e/broadcast", nil)
+	// no Content-Type and no body
+
+	handler.Broadcast(c)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
 // TestBroadcast_Truncate tests that messages are truncated with the Unicode ellipsis
-// TestBroadcast_Truncate tests that messages are truncated with the Unicode ellipsis
-// character (U+2026) when len(msg) > max. The truncated output is max runes + "…",
-// so truncating a 48-char string at max=20 produces 21 characters (20 runes + "…").
+// character (U+2026) when len(msg) > max. The truncated output is max runes + "…".
 func TestBroadcast_Truncate(t *testing.T) {
 	cases := []struct {
 		msg    string
@@ -410,14 +520,18 @@ func TestBroadcast_Truncate(t *testing.T) {
 		expect string
 	}{
 		{"short", 120, "short"}, // under max — no truncation
-		// exactly120chars (15) + 105 ones = 120 chars; at max=120 → unchanged
+		// exactly 120 chars → unchanged
 		{"exactly120chars1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111", 120, "exactly120chars111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111…"},
-		// "this is a longer mes" = 20 runes; + "…" = 21 chars
+		// 21 runes at max=20 → 20 + "…" = 21 chars
 		{"this is a longer message that needs truncating", 20, "this is a longer mes…"},
 		// at-max boundary: 20 chars at max=20 → no truncation
 		{"exactly twenty chars", 20, "exactly twenty chars"},
 		// over max: 11 chars at max=10 → 10 + "…" = 11
 		{"hello world!", 10, "hello worl…"},
+		// Unicode: 3-rune string at max=3 → unchanged
+		{"日本語", 3, "日本語"},
+		// Empty string → unchanged
+		{"", 120, ""},
 	}
 	for _, tc := range cases {
 		result := broadcastTruncate(tc.msg, tc.max)
diff --git a/workspace-server/internal/handlers/workspace_provision_shared.go b/workspace-server/internal/handlers/workspace_provision_shared.go
index e879521a..ba54bd96 100644
--- a/workspace-server/internal/handlers/workspace_provision_shared.go
+++ b/workspace-server/internal/handlers/workspace_provision_shared.go
@@ -37,6 +37,7 @@ package handlers
 import (
 	"context"
 	"errors"
+	"fmt"
 	"log"
 	"path/filepath"
 
@@ -132,6 +133,10 @@ func (h *WorkspaceHandler) prepareProvisionContext(
 	// a workspace_secret named GIT_AUTHOR_NAME can override.
 	applyAgentGitIdentity(envVars, payload.Name)
 	applyRuntimeModelEnv(envVars, payload.Runtime, payload.Model)
+	// SSOT for chat-upload limits — see chat_files.go::chatUploadMaxBytes.
+	// Injecting via env keeps the Python workspace runtime caps in
+	// lock-step with the Go cap on every provision. Fixes #1520.
+	applyChatUploadLimits(envVars)
 	if payload.Role != "" {
 		envVars["MOLECULE_AGENT_ROLE"] = payload.Role
 	}
@@ -223,3 +228,28 @@ func (h *WorkspaceHandler) markProvisionFailed(ctx context.Context, workspaceID,
 		log.Printf("markProvisionFailed: db update failed for %s: %v", workspaceID, dbErr)
 	}
 }
+
+// applyChatUploadLimits seeds the chat-upload cap env vars on the
+// workspace container so the Python /internal/chat/uploads/ingest
+// handler parses the multipart form with the same per-file allowance
+// that the Go proxy enforces.
+//
+// Why env-driven (and not, say, a hard-coded Python constant): keeping
+// one Go constant as the source of truth and forwarding it lets
+// operations bump the cap by editing one file + redeploy, instead of
+// editing two files in two languages and risking the drift that
+// shipped #1520 (Go cap 50 MB, Python parser cap 1 MiB — Starlette
+// default — so a 5 MB image always 400'd on parse before per-file
+// enforcement could fire).
+//
+// Pre-existing env wins. If something downstream (a tenant override,
+// a plugin mutator, an A/B experiment) has already set either var,
+// we leave it alone. Default-only injection.
+func applyChatUploadLimits(envVars map[string]string) {
+	if _, set := envVars["CHAT_UPLOAD_MAX_FILE_BYTES"]; !set {
+		envVars["CHAT_UPLOAD_MAX_FILE_BYTES"] = fmt.Sprintf("%d", chatUploadMaxFileBytes)
+	}
+	if _, set := envVars["CHAT_UPLOAD_MAX_TOTAL_BYTES"]; !set {
+		envVars["CHAT_UPLOAD_MAX_TOTAL_BYTES"] = fmt.Sprintf("%d", chatUploadMaxBytes)
+	}
+}
diff --git a/workspace/executor_helpers.py b/workspace/executor_helpers.py
index 52ae41b4..95e5aa81 100644
--- a/workspace/executor_helpers.py
+++ b/workspace/executor_helpers.py
@@ -599,6 +599,28 @@ def _sanitize_for_external(msg: str) -> str:
     import re as _re
 
     msg = _re.sub(r"(?i)(?:bearer|token|api[_-]?key|sk-)[ :=]+[A-Za-z0-9_/.-]{20,}", "[REDACTED]", msg)
+    # Bare provider key with NO separator after the prefix — a real
+    # `sk-ant-api03-…` / `sk-…` key uses `-` (not `[ :=]`) so the rule
+    # above misses it. Require ≥24 key-ish chars after the `sk-`/`sk-ant-`
+    # prefix so curated examples like `sk-ant-EXAMPLE-SHORT` (13 chars
+    # after `sk-ant-`) still pass through un-redacted.
+    msg = _re.sub(r"(?i)\bsk-(?:ant-)?[A-Za-z0-9_-]{24,}", "[REDACTED]", msg)
+    # JSON-quoted credential values: {"token": "…"} / {"apiKey": "…"} /
+    # {"secret": "…"} / {"password": "…"}. Redact only the value, and only
+    # when it is ≥24 chars so a short curated sample like
+    # `"api_key": "sk-ant-EXAMPLE-SHORT"` (20-char value) still passes.
+    msg = _re.sub(
+        r'(?i)("(?:token|api[_-]?key|secret|password)"\s*:\s*")[^"]{24,}(")',
+        r"\1[REDACTED]\2",
+        msg,
+    )
+    # AWS secret access key in `aws_secret_access_key=…` form (env dumps,
+    # boto tracebacks). The base64-ish value runs until whitespace/quote.
+    msg = _re.sub(
+        r"(?i)(aws_secret_access_key\s*[:=]\s*)\S+",
+        r"\1[REDACTED]",
+        msg,
+    )
     # Absolute paths: /etc/shadow, /home/user/.aws/credentials, etc.
     msg = _re.sub(r"(?:/[^/\s]+){2,}", lambda m: m.group(0) if len(m.group(0)) < 60 else "[REDACTED_PATH]", msg)
     return msg
@@ -608,6 +630,7 @@ def sanitize_agent_error(
     exc: BaseException | None = None,
     category: str | None = None,
     stderr: str | None = None,
+    reason: str | None = None,
 ) -> str:
     """Render an agent-side failure into a user-safe error message.
 
@@ -615,6 +638,18 @@ def sanitize_agent_error(
     category string (e.g. from `classify_subprocess_error`). If both are
     given, `category` wins. If neither, the tag defaults to "unknown".
 
+    When ``reason`` is provided (internal#211/#212), it is a *pre-curated,
+    user-actionable, secret-safe* explanation built by the caller from a
+    provider-side failure — e.g. a 403 "Your organization has disabled
+    Claude subscription access · Use an Anthropic API key instead, or ask
+    your admin to enable access" with error code ``oauth_org_not_allowed``.
+    This text is exactly what the user needs to self-serve, so it is
+    surfaced VERBATIM as the message instead of being collapsed to the
+    opaque exception class name. It still passes through the
+    key/token/bearer/path scrubber as a belt-and-braces second pass so a
+    buggy caller can't leak a credential that snuck into the reason.
+    ``reason`` wins over ``stderr``; both lose to neither being set.
+
     When ``stderr`` is provided (e.g. the first ~1 KB of a subprocess stderr
     or HTTP error body), it is sanitized and appended to the output so the
     A2A caller gets actionable context without needing to dig through workspace
@@ -629,6 +664,13 @@ def sanitize_agent_error(
     else:
         tag = "unknown"
 
+    if reason:
+        # Curated, user-actionable reason — surface it as the message.
+        # Still scrub: a 403/auth/quota message is safe, but the scrubber
+        # is cheap insurance against a caller that didn't curate cleanly.
+        clean = _sanitize_for_external(reason[:_MAX_STDERR_PREVIEW])
+        return f"Agent error ({tag}): {clean}"
+
     if stderr:
         # Truncate and sanitize before including — prevents DoS via
         # a malicious or buggy peer injecting a huge error body, and
diff --git a/workspace/internal_chat_uploads.py b/workspace/internal_chat_uploads.py
index 396c1ac8..bff6ea73 100644
--- a/workspace/internal_chat_uploads.py
+++ b/workspace/internal_chat_uploads.py
@@ -26,9 +26,14 @@ Path safety:
     a colliding name fails fast (the random prefix already makes
     collisions astronomical, but defense-in-depth costs nothing).
 
-Limits (matches the Go contract from chat_files.go):
-    - 50 MB total request body
-    - 25 MB per file
+Limits (SSOT — matches the Go contract from chat_files.go, injected
+via CHAT_UPLOAD_MAX_TOTAL_BYTES / CHAT_UPLOAD_MAX_FILE_BYTES at
+provision time; falls back to legacy 50 MB / 25 MB when env unset):
+    - CHAT_UPLOAD_MAX_TOTAL_BYTES total request body (default 50 MB)
+    - CHAT_UPLOAD_MAX_FILE_BYTES per file (default 25 MB)
+      ALSO passed as Starlette ``max_part_size`` to override the
+      Starlette-1.0 default of 1 MiB which silently 400'd every
+      upload > 1 MiB before #1520 fix.
     - filename truncated to 100 chars
 
 Response shape:
@@ -61,14 +66,47 @@ logger = logging.getLogger(__name__)
 # keeps working unchanged.
 CHAT_UPLOAD_DIR = "/workspace/.molecule/chat-uploads"
 
+def _env_int(name: str, default: int) -> int:
+    """Parse an int from the environment, falling back to ``default``.
+
+    Mis-formatted values (anything ``int()`` rejects) fall back to the
+    default rather than crashing module import — operations needs to be
+    able to roll back a bad env-var push by simply removing the var,
+    not by also fixing a worker that won't boot.
+    """
+    raw = os.environ.get(name)
+    if not raw:
+        return default
+    try:
+        return int(raw)
+    except (TypeError, ValueError):
+        logger.warning("internal_chat_uploads: env %s=%r not an int; using default %d", name, raw, default)
+        return default
+
 # Total-request body cap. multipart/form-data with multiple parts can
 # add ~100 bytes of framing per file; the cap is the bytes hitting the
 # socket, including framing.
-CHAT_UPLOAD_MAX_BYTES = 50 * 1024 * 1024  # 50 MB
+#
+# SSOT (issue #1520): the source of truth is the Go constant
+# chatUploadMaxBytes in workspace-server/internal/handlers/chat_files.go,
+# exported to the workspace container as CHAT_UPLOAD_MAX_TOTAL_BYTES at
+# provision time (workspace_provision_shared.go::applyChatUploadLimits).
+# Unset env → keep the previous 50 MB default so an unprovisioned /
+# locally-run workspace does NOT regress.
+CHAT_UPLOAD_MAX_BYTES = _env_int("CHAT_UPLOAD_MAX_TOTAL_BYTES", 50 * 1024 * 1024)
 
-# Per-file cap. Keeping per-file under total lets a user attach, say,
-# a 5 MB PDF + 10 small screenshots in a single batch.
-CHAT_UPLOAD_MAX_FILE_BYTES = 25 * 1024 * 1024  # 25 MB
+# Per-file cap. SSOT (issue #1520): exported from the Go side as
+# CHAT_UPLOAD_MAX_FILE_BYTES; default 25 MB if env is unset so an older
+# workspace provisioned before the env-injection landed keeps the
+# legacy ceiling.
+#
+# This value is ALSO passed as Starlette's ``max_part_size`` (see
+# ingest_handler below) — Starlette 1.0 defaults max_part_size to
+# **1 MiB**, which is the actual root cause of #1520: any single file
+# part above 1 MiB raised MultiPartException before per-file enforcement
+# could fire. Wiring max_part_size to the same cap as per-file means
+# the user-visible ceiling is exactly the per-file cap, no surprises.
+CHAT_UPLOAD_MAX_FILE_BYTES = _env_int("CHAT_UPLOAD_MAX_FILE_BYTES", 25 * 1024 * 1024)
 
 # Conservative {alnum, dot, underscore, dash} character class — anything
 # outside gets rewritten so embedded paths, control chars, newlines,
@@ -146,11 +184,30 @@ async def ingest_handler(request: Request) -> JSONResponse:
                 status_code=413,
             )
 
+    # max_part_size: Starlette 1.0 defaults to 1 MiB. Any single
+    # part above that raises MultiPartException BEFORE per-file
+    # enforcement can run — which silently broke every chat upload
+    # > 1 MiB (issue #1520, fleet-wide P0 2026-05-18). Wire it to
+    # the per-file cap so the user-visible ceiling matches what
+    # the per-file 413 path expects.
     try:
-        form = await request.form(max_files=64, max_fields=32)
+        form = await request.form(
+            max_files=64,
+            max_fields=32,
+            max_part_size=CHAT_UPLOAD_MAX_FILE_BYTES,
+        )
     except Exception as exc:  # multipart parse error
         logger.warning("internal_chat_uploads: multipart parse failed: %s", exc)
-        return JSONResponse({"error": "failed to parse multipart form"}, status_code=400)
+        # Surface the exception detail (feedback_surface_actionable_failure_reason_to_user):
+        # MultiPartException strings ("Part exceeded maximum size of …",
+        # "Invalid boundary", "Too many parts", etc.) contain no secrets
+        # — they describe shape, not content. The 200-char cap is
+        # belt-and-braces against an exception class we haven't seen
+        # whose ``str()`` is unbounded.
+        return JSONResponse(
+            {"error": "failed to parse multipart form", "detail": str(exc)[:200]},
+            status_code=400,
+        )
 
     # Starlette's FormData allows multiple values per key — `files` may
     # appear multiple times for batched uploads. getlist returns them
diff --git a/workspace/tests/test_executor_helpers.py b/workspace/tests/test_executor_helpers.py
index 9ca88063..ab953f55 100644
--- a/workspace/tests/test_executor_helpers.py
+++ b/workspace/tests/test_executor_helpers.py
@@ -788,6 +788,123 @@ def test_sanitize_agent_error_stderr_combined_with_existing_tests():
     assert "workspace logs" in out
 
 
+# ─── reason passthrough (internal#211/#212: surface actionable provider error) ───
+
+
+def test_sanitize_agent_error_reason_surfaced_verbatim():
+    """A curated provider reason is shown to the user, not collapsed to the
+    exception class name. This is the internal#211 regression: a 403
+    org-disabled message must reach the canvas."""
+    reason = (
+        "provider HTTP 403 — oauth_org_not_allowed — Your organization has "
+        "disabled Claude subscription access for Claude Code · Use an "
+        "Anthropic API key instead, or ask your admin to enable access"
+    )
+
+    class _ResultErr(Exception):
+        pass
+
+    out = sanitize_agent_error(exc=_ResultErr("opaque"), reason=reason)
+    # The actionable provider guidance and status code must be visible.
+    assert "403" in out
+    assert "oauth_org_not_allowed" in out
+    assert "disabled Claude subscription access" in out
+    assert "ask your admin to enable access" in out
+    # NOT the old opaque form.
+    assert "see workspace logs" not in out
+
+
+def test_sanitize_agent_error_reason_still_scrubs_secrets():
+    """Even on the reason path the key/token scrubber runs — a buggy caller
+    that lets a bearer token into the reason still gets it redacted."""
+    leaky = (
+        "provider HTTP 401 — auth failed — Authorization: Bearer "
+        "PLACEHOLDER_LONG_TOKEN_0123456789abcdefghijklm please re-auth"
+    )
+    out = sanitize_agent_error(reason=leaky)
+    assert "[REDACTED]" in out
+    assert "PLACEHOLDER_LONG_TOKEN_0123456789abcdefghijklm" not in out
+    # The non-secret guidance still survives the scrub.
+    assert "401" in out
+    assert "please re-auth" in out
+
+
+def test_sanitize_agent_error_reason_scrubs_all_secret_formats():
+    """The scrubber must redact every realistic credential shape — not just
+    the `Bearer <tok>` form the original test happened to exercise
+    (internal#212 review finding: bare `sk-ant-api03-…` keys, JSON-quoted
+    "token"/"apiKey" values, and `aws_secret_access_key=` all leaked).
+    All curated/actionable guidance must still survive the scrub.
+    """
+    # 1. Bare sk-ant-api03 key — no `[ :=]` separator after the prefix
+    #    (a real Anthropic key uses `-`), so the legacy regex missed it.
+    bare = (
+        "provider HTTP 401 — auth failed — invalid key "
+        "sk-FAKEPLACEHOLDERabcdefghijklmnopqrstuvwxy0123456789 "
+        "please re-auth"
+    )
+    out = sanitize_agent_error(reason=bare)
+    assert "sk-FAKEPLACEHOLDERabcdefghijklmnopqrstuvwxy0123456789" not in out
+    assert "[REDACTED]" in out
+    assert "401" in out  # actionable status survives
+    assert "please re-auth" in out  # actionable guidance survives
+
+    # 2. JSON-quoted "token" / "apiKey" values.
+    jblob = (
+        'provider error — config dump {"token": '
+        '"abcDEF0123456789ghIJKL0123456789mnopQRST", "apiKey": '
+        '"anon_fakefakefakefakefakefakefakefakefakefake"} — '
+        "use an API key instead"
+    )
+    out = sanitize_agent_error(reason=jblob)
+    assert "abcDEF0123456789ghIJKL0123456789mnopQRST" not in out
+    assert "anon_fakefakefakefakefakefakefakefakefakefake" not in out
+    assert "[REDACTED]" in out
+    assert "use an API key instead" in out  # actionable guidance survives
+
+    # 3. aws_secret_access_key=… form.
+    awsblob = (
+        "provider HTTP 403 — boto credential error "
+        "aws_secret_access_key=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY — "
+        "ask your admin to enable access"
+    )
+    out = sanitize_agent_error(reason=awsblob)
+    assert "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY" not in out
+    assert "[REDACTED]" in out
+    assert "403" in out  # actionable status survives
+    assert "ask your admin to enable access" in out  # guidance survives
+
+    # 4. Regression: the original Bearer form still redacts.
+    # Uses PLACEHOLDER_LONG_TOKEN (>=40 chars, no sk-ant- prefix) to avoid
+    # triggering the secret-scan workflow pattern
+    # `sk-ant-[A-Za-z0-9_-]{40,}`.
+    bearer = (
+        "provider HTTP 401 — Authorization: Bearer "
+        "PLACEHOLDER_LONG_TOKEN_9876543210abcdefghij re-auth"
+    )
+    out = sanitize_agent_error(reason=bearer)
+    assert "PLACEHOLDER_LONG_TOKEN_9876543210abcdefghij" not in out
+    assert "[REDACTED]" in out
+    assert "re-auth" in out
+
+
+def test_sanitize_agent_error_reason_wins_over_stderr():
+    """When both reason and stderr are passed, the curated reason wins."""
+    out = sanitize_agent_error(
+        reason="provider HTTP 403 — use an API key",
+        stderr="raw subprocess noise that should not be shown",
+    )
+    assert "use an API key" in out
+    assert "raw subprocess noise" not in out
+
+
+def test_sanitize_agent_error_no_reason_unchanged():
+    """Omitting reason preserves the original generic behavior."""
+    out = sanitize_agent_error(exc=ValueError("boom"))
+    assert "ValueError" in out
+    assert "workspace logs" in out
+
+
 
 # ======================================================================
 # classify_subprocess_error
diff --git a/workspace/tests/test_internal_chat_uploads.py b/workspace/tests/test_internal_chat_uploads.py
index d386de65..e7949490 100644
--- a/workspace/tests/test_internal_chat_uploads.py
+++ b/workspace/tests/test_internal_chat_uploads.py
@@ -299,3 +299,122 @@ def test_symlink_at_target_is_refused(client: TestClient, chat_uploads_dir: Path
     assert r.status_code == 500, r.text
     # Sentinel content unchanged — the symlink wasn't followed.
     assert sentinel.read_bytes() == b"original"
+# ───────────── issue #1520: max_part_size + SSOT env-driven caps ─────────────
+
+
+def test_part_above_starlette_1mib_default_is_accepted(client: TestClient, chat_uploads_dir: Path):
+    """Regression: pre-fix, ANY single multipart part > 1 MiB raised
+    MultiPartException because the ingest handler called
+    ``request.form()`` without ``max_part_size`` and Starlette 1.0's
+    default is 1 MiB (issue #1520, fleet-wide P0 2026-05-18).
+
+    This test sends a 2 MiB part, which is well below the 25 MB default
+    per-file cap but ABOVE the Starlette default, so it pins the fix:
+    we now pass ``max_part_size=CHAT_UPLOAD_MAX_FILE_BYTES`` so the
+    parser uses the same cap the per-file 413 path expects.
+    """
+    payload = b"a" * (2 * 1024 * 1024)  # 2 MiB — > Starlette 1 MiB default
+    r = client.post(
+        "/internal/chat/uploads/ingest",
+        files={"files": ("big-but-allowed.bin", payload)},
+        headers={"Authorization": "Bearer test-secret"},
+    )
+    assert r.status_code == 200, r.text
+    item = r.json()["files"][0]
+    assert item["size"] == len(payload)
+
+
+def test_parse_error_surfaces_exception_detail(client: TestClient):
+    """Per feedback_surface_actionable_failure_reason_to_user: the 400
+    body must include a ``detail`` field naming WHICH multipart error
+    fired. The MultiPartException strings ("Part exceeded maximum size
+    of …", "Invalid boundary", "Too many parts", etc.) describe SHAPE
+    not content — no secrets.
+
+    We trigger a real Starlette MultiPartException by submitting a body
+    whose Content-Type advertises ``multipart/form-data`` but whose
+    body is not a valid multipart envelope — the parser raises before
+    any per-file check can fire.
+    """
+    r = client.post(
+        "/internal/chat/uploads/ingest",
+        content=b"this is not a valid multipart body",
+        headers={
+            "Authorization": "Bearer test-secret",
+            "Content-Type": "multipart/form-data; boundary=----not-a-real-boundary",
+        },
+    )
+    assert r.status_code == 400, r.text
+    body = r.json()
+    assert body["error"] == "failed to parse multipart form"
+    # Detail must be present + non-empty + bounded.
+    assert "detail" in body and isinstance(body["detail"], str)
+    assert body["detail"], "detail must not be empty"
+    assert len(body["detail"]) <= 200, "detail must be bounded"
+
+
+def test_total_cap_413_still_fires_above_per_file_pass(client: TestClient, monkeypatch: pytest.MonkeyPatch):
+    """Total-cap 413 path still works: two parts whose sum exceeds
+    CHAT_UPLOAD_MAX_BYTES but each individually fits the per-file cap.
+    Sanity-check that raising the per-file ceiling didn't accidentally
+    short-circuit the total-cap check.
+    """
+    monkeypatch.setattr(internal_chat_uploads, "CHAT_UPLOAD_MAX_BYTES", 1024)
+    monkeypatch.setattr(internal_chat_uploads, "CHAT_UPLOAD_MAX_FILE_BYTES", 800)
+    r = client.post(
+        "/internal/chat/uploads/ingest",
+        files=[
+            ("files", ("a.bin", b"a" * 600)),
+            ("files", ("b.bin", b"b" * 600)),
+        ],
+        headers={"Authorization": "Bearer test-secret"},
+    )
+    assert r.status_code == 413
+    # Either early (Content-Length pre-parse) or post-parse cumulative path is
+    # acceptable; both messages mention exceeding the total limit.
+    err = r.json()["error"]
+    assert "exceeds" in err and "limit" in err, err
+
+
+def test_env_driven_ssot_overrides_caps(tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
+    """SSOT contract: setting CHAT_UPLOAD_MAX_FILE_BYTES /
+    CHAT_UPLOAD_MAX_TOTAL_BYTES in the environment at module import
+    time changes the module constants. Pin so the
+    workspace_provision_shared.go::applyChatUploadLimits env injection
+    cannot silently drift from what the Python side reads.
+    """
+    import importlib
+
+    monkeypatch.setenv("CHAT_UPLOAD_MAX_FILE_BYTES", str(7 * 1024 * 1024))
+    monkeypatch.setenv("CHAT_UPLOAD_MAX_TOTAL_BYTES", str(13 * 1024 * 1024))
+
+    reloaded = importlib.reload(internal_chat_uploads)
+    try:
+        assert reloaded.CHAT_UPLOAD_MAX_FILE_BYTES == 7 * 1024 * 1024
+        assert reloaded.CHAT_UPLOAD_MAX_BYTES == 13 * 1024 * 1024
+    finally:
+        # Reset to defaults so subsequent tests see clean constants.
+        monkeypatch.delenv("CHAT_UPLOAD_MAX_FILE_BYTES", raising=False)
+        monkeypatch.delenv("CHAT_UPLOAD_MAX_TOTAL_BYTES", raising=False)
+        importlib.reload(internal_chat_uploads)
+
+
+def test_env_driven_ssot_malformed_value_falls_back_to_default(tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
+    """If ops pushes a garbage value the worker still boots with the
+    in-code default (operability over precision — see _env_int
+    docstring). Pin the fallback.
+    """
+    import importlib
+
+    monkeypatch.setenv("CHAT_UPLOAD_MAX_FILE_BYTES", "not-an-int")
+    monkeypatch.setenv("CHAT_UPLOAD_MAX_TOTAL_BYTES", "")  # empty == use default
+
+    reloaded = importlib.reload(internal_chat_uploads)
+    try:
+        # Defaults (legacy 25 MB / 50 MB) come back.
+        assert reloaded.CHAT_UPLOAD_MAX_FILE_BYTES == 25 * 1024 * 1024
+        assert reloaded.CHAT_UPLOAD_MAX_BYTES == 50 * 1024 * 1024
+    finally:
+        monkeypatch.delenv("CHAT_UPLOAD_MAX_FILE_BYTES", raising=False)
+        monkeypatch.delenv("CHAT_UPLOAD_MAX_TOTAL_BYTES", raising=False)
+        importlib.reload(internal_chat_uploads)