fix(web): close P3 chat re-review findings

apps/web/src/lib/socket.spec.ts

@@ -10,25 +10,45 @@ vi.mock('socket.io-client', () => ({
 
 import { destroySocket, getSocket } from './socket';
 
-function createMockSocket(): {
+interface MockChatSocket {
   on: ReturnType<typeof vi.fn>;
   offAny: ReturnType<typeof vi.fn>;
   disconnect: ReturnType<typeof vi.fn>;
-} {
+  /** Test-only helper: fires every handler registered for `event` via
-  const mockSocket = {
+   * `.on`, mirroring how a real socket.io-client instance invokes its own
-    on: vi.fn(() => mockSocket),
+   * listeners (e.g. calling the registered `disconnect` handler(s) on a
+   * real transient disconnect). */
+  trigger(event: string): void;
+}
+
+function createMockSocket(): MockChatSocket {
+  const handlers = new Map<string, Set<() => void>>();
+  const mockSocket: MockChatSocket = {
+    on: vi.fn((event: string, handler: () => void) => {
+      if (!handlers.has(event)) handlers.set(event, new Set());
+      handlers.get(event)?.add(handler);
+      return mockSocket;
+    }),
     offAny: vi.fn(() => mockSocket),
     disconnect: vi.fn(() => mockSocket),
+    trigger(event: string): void {
+      for (const handler of handlers.get(event) ?? []) handler();
+    },
   };
   return mockSocket;
 }
 
+let currentMock!: MockChatSocket;
+
 describe('chat socket', () => {
   beforeEach(() => {
     ioMock.mockReset();
     // A fresh object per io() call so identity assertions (same singleton vs.
     // a genuinely new instance) are meaningful.
-    ioMock.mockImplementation(() => createMockSocket());
+    ioMock.mockImplementation(() => {
+      currentMock = createMockSocket();
+      return currentMock;
+    });
   });
 
   afterEach(() => {
@@ -52,9 +72,14 @@ describe('chat socket', () => {
     const first = getSocket();
 
     // socket.ts must not react to a real socket's `disconnect` event by
-    // nulling the singleton — it registers no such handler at all now, so
+    // nulling the singleton — it registers no such handler at all now.
-    // simply calling getSocket() again after a "disconnect" must still
+    // Actually fire every handler registered via `.on('disconnect', ...)`
-    // return the same instance.
+    // (mirroring a real socket.io-client reconnect) instead of merely
+    // calling getSocket() again: this is what makes the test fail if
+    // production reintroduces `socket.on('disconnect', () => { socket =
+    // null; })`, since that handler would run here and null the singleton
+    // before the next getSocket() call.
+    currentMock.trigger('disconnect');
     const second = getSocket();
 
     expect(second).toBe(first);

apps/web/src/spa/chat/commands-panel.spec.tsx

@@ -174,6 +174,66 @@ describe('CommandsPanel', () => {
     ).toBe(false);
   });
 
+  it('shows the guarded server-provided denial reason for a denied approval', async () => {
+    await render(
+      <CommandsPanel
+        manifest={null}
+        results={[]}
+        approval={{
+          conversationId: 'c1',
+          command: 'deploy',
+          success: false,
+          message: 'Not authorized',
+        }}
+        pendingApproval={{ command: 'deploy', args: 'prod' }}
+        hasConversation
+        onExecute={vi.fn()}
+        onApprove={vi.fn()}
+        onRunApproved={vi.fn()}
+      />,
+    );
+
+    expect(container?.textContent).toContain('Not authorized');
+  });
+
+  it('falls back to a stable "Denied." copy when a denial has no usable message', async () => {
+    await render(
+      <CommandsPanel
+        manifest={null}
+        results={[]}
+        approval={{ conversationId: 'c1', command: 'deploy', success: false }}
+        pendingApproval={{ command: 'deploy', args: 'prod' }}
+        hasConversation
+        onExecute={vi.fn()}
+        onApprove={vi.fn()}
+        onRunApproved={vi.fn()}
+      />,
+    );
+
+    expect(container?.textContent).toContain('Denied.');
+  });
+
+  it('shows the guarded contract-provided reason for a failed command result, falling back to a stable copy only when absent', async () => {
+    await render(
+      <CommandsPanel
+        manifest={null}
+        results={[
+          { conversationId: 'c1', command: 'model', success: false, message: 'Unknown model' },
+          { conversationId: 'c1', command: 'deploy', success: false },
+        ]}
+        approval={null}
+        pendingApproval={null}
+        hasConversation={false}
+        onExecute={vi.fn()}
+        onApprove={vi.fn()}
+        onRunApproved={vi.fn()}
+      />,
+    );
+
+    expect(container?.textContent).toContain('Unknown model');
+    expect(container?.textContent).toContain('Command failed.');
+  });
+
   it('does not throw when the manifest fields are malformed (non-array commands/skills)', async () => {
     const manifest = {
       commands: 'not-an-array',

apps/web/src/spa/chat/commands-panel.tsx

@@ -1,14 +1,16 @@
 import { useState, type ReactElement } from 'react';
 import type { PendingApproval } from './use-chat-connection';
-import { asString } from './runtime-guards';
+import { asNonEmptyString, asString } from './runtime-guards';
 import type {
   CommandManifest,
   SlashCommandApprovalResultPayload,
   SlashCommandResultPayload,
 } from '@/lib/chat-contract';
 
-/** Stable client copy shown for a failed command — never the raw server
+/** Stable fallback copy shown for a failed command only when the server's
- * detail, which could leak internal error text to the user. */
+ * own guarded, non-empty `message` (e.g. "Unknown model") is absent or
+ * malformed — the structured contract reason itself is otherwise shown
+ * directly, never a raw thrown exception, stack trace, or object value. */
 const COMMAND_FAILURE_COPY = 'Command failed.';
 
 interface CommandsPanelProps {
@@ -104,11 +106,17 @@ export function CommandsPanel({
 
       {approval ? (
         <div role={approval.success ? 'status' : 'alert'} className="flex items-center gap-2">
-          {/* Stable client copy only — never the server-controlled
+          {/* A successful approval shows stable client copy only — never
-              approval.message or echoed approval.command as the primary
+              the server-controlled approval.message or echoed
-              confirmation. The frozen local pendingApproval below (not this
+              approval.command as the primary confirmation. The frozen local
-              line) is the sole authoritative statement of what will run. */}
+              pendingApproval below (not this line) is the sole authoritative
-          <span>{approval.success ? 'Approved.' : 'Denied.'}</span>
+              statement of what will run. A denial, by contrast, is not an
+              execution authority and safely surfaces the guarded structured
+              reason the server gave (e.g. "Not authorized"), falling back to
+              a stable copy only when absent/malformed. */}
+          <span>
+            {approval.success ? 'Approved.' : asNonEmptyString(approval.message, 'Denied.')}
+          </span>
           {canRunApproved && pendingApproval ? (
             <>
               {/* Authoritative frozen local command+args — what the click below
@@ -135,7 +143,7 @@ export function CommandsPanel({
                 ? typeof result.message === 'string' && result.message
                   ? ` — ${result.message}`
                   : ''
-                : ` — ${COMMAND_FAILURE_COPY}`}
+                : ` — ${asNonEmptyString(result.message, COMMAND_FAILURE_COPY)}`}
             </li>
           ))}
         </ul>

apps/web/src/spa/chat/runtime-guards.ts

@@ -10,6 +10,14 @@ export function asString(value: unknown, fallback = ''): string {
   return typeof value === 'string' ? value : fallback;
 }
 
+/** Like `asString`, but an empty string also falls back — used for guarded
+ * contract-provided reason strings (e.g. a denial or failure message) where
+ * an empty string is not a meaningful value to display in place of the
+ * stable fallback copy. */
+export function asNonEmptyString(value: unknown, fallback: string): string {
+  return typeof value === 'string' && value.length > 0 ? value : fallback;
+}
+
 export function asFiniteNumber(value: unknown, fallback = 0): number {
   return typeof value === 'number' && Number.isFinite(value) ? value : fallback;
 }

apps/web/src/spa/chat/session-panel.tsx

@@ -1,5 +1,6 @@
 import type { ReactElement } from 'react';
 import type { SessionInfoPayload } from '@/lib/chat-contract';
+import { MAX_MANIFEST_ITEMS } from './limits';
 import { asString, asStringArray } from './runtime-guards';
 
 interface SessionPanelProps {
@@ -15,7 +16,13 @@ export function SessionPanel({
 }: SessionPanelProps): ReactElement | null {
   if (!sessionInfo) return null;
 
-  const availableThinkingLevels = asStringArray(sessionInfo.availableThinkingLevels);
+  // The reducer already caps this before storing it, but the render site
+  // defends independently — a hostile payload must never be able to force
+  // this <select> to lay out an unbounded number of options.
+  const availableThinkingLevels = asStringArray(sessionInfo.availableThinkingLevels).slice(
+    0,
+    MAX_MANIFEST_ITEMS,
+  );
   const hasThinkingLevels = availableThinkingLevels.length > 0;
 
   return (

apps/web/src/spa/chat/use-chat-connection.spec.tsx

@@ -1,9 +1,10 @@
 import { act } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it, vi } from 'vitest';
-import { createFakeChatSocket } from './test-support/fake-chat-socket';
+import { createFakeChatSocket, type EmittedEvent } from './test-support/fake-chat-socket';
 import {
   MAX_COMMAND_RESULTS,
+  MAX_EXECUTED_APPROVAL_IDS,
   MAX_MANIFEST_ITEMS,
   MAX_MESSAGES,
   MAX_STREAM_CHARS,
@@ -430,6 +431,14 @@ describe('useChatConnection', () => {
     expect(latest?.state.conversationId).toBe('c1');
     expect(latest?.state.error).toBe('Failed to start agent session. Please try again.');
     expect(latest?.state.streaming).toBe(false);
+    expect(latest?.state.sending).toBe(false);
+
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'retry' });
+    });
+
+    expect(fake.emitted.filter((e) => e.event === 'message')).toHaveLength(2);
+    expect(latest?.state.messages.some((m) => m.text === 'retry')).toBe(true);
   });
 
   it('stops streaming when a typed error arrives mid-turn', async () => {
@@ -881,6 +890,10 @@ describe('useChatConnection', () => {
 
     expect(latest?.state.manifest?.commands).toEqual([]);
     expect(latest?.state.manifest?.skills).toEqual([]);
+    // The raw stored reload must be normalized the same way as the manifest —
+    // never left holding the malformed raw value.
+    expect(latest?.state.systemReload?.commands).toEqual([]);
+    expect(latest?.state.systemReload?.skills).toEqual([]);
   });
 
   it('falls back to a safe tool label when agent:tool:start carries a non-string toolName', async () => {
@@ -932,19 +945,74 @@ describe('useChatConnection', () => {
     expect(latest?.state.pendingApproval).toEqual({ command: 'deploy', args: 'prod' });
   });
 
-  it('caps streamed agent:text at MAX_STREAM_CHARS, keeping only the most recent characters', async () => {
+  it('caps streamed agent:text at MAX_STREAM_CHARS behind a visible marker disclosing the honest dropped-character count across multiple appends', async () => {
     await act(async () => {
       fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
       fake.serverEmit('agent:start', { conversationId: 'c1' });
     });
 
+    const firstChunk = 'a'.repeat(MAX_STREAM_CHARS);
+    const secondChunk = 'b'.repeat(500);
+    const thirdChunk = 'c'.repeat(300);
+
     await act(async () => {
-      fake.serverEmit('agent:text', { conversationId: 'c1', text: 'a'.repeat(MAX_STREAM_CHARS) });
+      fake.serverEmit('agent:text', { conversationId: 'c1', text: firstChunk });
-      fake.serverEmit('agent:text', { conversationId: 'c1', text: 'b'.repeat(10) });
+    });
+    await act(async () => {
+      fake.serverEmit('agent:text', { conversationId: 'c1', text: secondChunk });
+    });
+    await act(async () => {
+      fake.serverEmit('agent:text', { conversationId: 'c1', text: thirdChunk });
     });
 
-    expect(latest?.state.text).toHaveLength(MAX_STREAM_CHARS);
+    const text = latest?.state.text ?? '';
-    expect(latest?.state.text.endsWith('b'.repeat(10))).toBe(true);
+    expect(text.length).toBeLessThanOrEqual(MAX_STREAM_CHARS);
+
+    const match = text.match(/^…\[truncated (\d+) characters\]…/);
+    expect(match).not.toBeNull();
+    const markerLength = match?.[0].length ?? 0;
+    const droppedCount = Number(match?.[1]);
+    const tail = text.slice(markerLength);
+    const totalStreamed = firstChunk.length + secondChunk.length + thirdChunk.length;
+
+    // The marker's N must be the actual count of original characters no
+    // longer visible — not an estimate — across all three appends.
+    expect(droppedCount).toBe(totalStreamed - tail.length);
+    expect(tail.endsWith(thirdChunk)).toBe(true);
+  });
+
+  it('caps streamed agent:thinking at MAX_STREAM_CHARS behind the same honest truncation marker as agent:text', async () => {
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+    });
+
+    const firstChunk = 'x'.repeat(MAX_STREAM_CHARS);
+    const secondChunk = 'y'.repeat(500);
+    const thirdChunk = 'z'.repeat(300);
+
+    await act(async () => {
+      fake.serverEmit('agent:thinking', { conversationId: 'c1', text: firstChunk });
+    });
+    await act(async () => {
+      fake.serverEmit('agent:thinking', { conversationId: 'c1', text: secondChunk });
+    });
+    await act(async () => {
+      fake.serverEmit('agent:thinking', { conversationId: 'c1', text: thirdChunk });
+    });
+
+    const thinking = latest?.state.thinking ?? '';
+    expect(thinking.length).toBeLessThanOrEqual(MAX_STREAM_CHARS);
+
+    const match = thinking.match(/^…\[truncated (\d+) characters\]…/);
+    expect(match).not.toBeNull();
+    const markerLength = match?.[0].length ?? 0;
+    const droppedCount = Number(match?.[1]);
+    const tail = thinking.slice(markerLength);
+    const totalStreamed = firstChunk.length + secondChunk.length + thirdChunk.length;
+
+    expect(droppedCount).toBe(totalStreamed - tail.length);
+    expect(tail.endsWith(thirdChunk)).toBe(true);
   });
 
   it('caps commandResults at MAX_COMMAND_RESULTS when flooded with command:result events', async () => {
@@ -983,7 +1051,7 @@ describe('useChatConnection', () => {
     expect(latest?.state.manifest?.commands).toHaveLength(MAX_MANIFEST_ITEMS);
   });
 
-  it('caps a system:reload manifest replacement at MAX_MANIFEST_ITEMS', async () => {
+  it('caps a system:reload manifest replacement at MAX_MANIFEST_ITEMS for both the raw stored reload and the manifest', async () => {
     const commands = Array.from({ length: MAX_MANIFEST_ITEMS + 5 }, (_, i) => ({
       name: `cmd${i}`,
       aliases: [],
@@ -992,17 +1060,48 @@ describe('useChatConnection', () => {
       execution: 'socket' as const,
       available: true,
     }));
+    const skills = Array.from({ length: MAX_MANIFEST_ITEMS + 5 }, (_, i) => ({
+      name: `skill${i}`,
+      description: '',
+      available: true,
+    }));
 
     await act(async () => {
       fake.serverEmit('system:reload', {
         commands,
-        skills: [],
+        skills,
         providers: ['anthropic'],
         message: 'reloaded',
       });
     });
 
     expect(latest?.state.manifest?.commands).toHaveLength(MAX_MANIFEST_ITEMS);
+    expect(latest?.state.manifest?.skills).toHaveLength(MAX_MANIFEST_ITEMS);
+    // The raw stored reload (state.systemReload) must be bounded the same
+    // way as the manifest derived from it — a hostile/oversized broadcast
+    // must never leave the uncapped raw payload sitting in state.
+    expect(latest?.state.systemReload?.commands).toHaveLength(MAX_MANIFEST_ITEMS);
+    expect(latest?.state.systemReload?.skills).toHaveLength(MAX_MANIFEST_ITEMS);
+  });
+
+  it('caps availableThinkingLevels before storing a hostile session:info payload', async () => {
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+    });
+
+    const hostileLevels = Array.from({ length: MAX_MANIFEST_ITEMS + 50 }, (_, i) => `level-${i}`);
+
+    await act(async () => {
+      fake.serverEmit('session:info', {
+        conversationId: 'c1',
+        provider: 'anthropic',
+        modelId: 'claude',
+        thinkingLevel: 'level-0',
+        availableThinkingLevels: hostileLevels,
+      });
+    });
+
+    expect(latest?.state.sessionInfo?.availableThinkingLevels).toHaveLength(MAX_MANIFEST_ITEMS);
   });
 
   it('ignores a malformed (object) conversationId on the establishing message:ack, leaving the turn recoverable for a later valid ack', async () => {
@@ -1245,6 +1344,234 @@ describe('useChatConnection', () => {
     expect(new Set(ids).size).toBe(ids.length);
   });
 
+  it('fails closed after the consumed approval cache saturates and rejects replay of the ID the old eviction policy forgot', async () => {
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+    });
+
+    // Fill the bounded dedup set to capacity with genuinely distinct,
+    // legitimately approved and executed IDs. Each step of approve/respond/
+    // run gets its own `act()` so a render (and the ref-syncing effects)
+    // lands between them — combining approve+respond in one act would let
+    // `approvalRequestPending` flip true-then-false within a single commit,
+    // skipping the render the lock-sync effect depends on.
+    for (let i = 0; i < MAX_EXECUTED_APPROVAL_IDS; i += 1) {
+      await act(async () => {
+        latest?.actions.approveCommand({ command: 'deploy' });
+      });
+      await act(async () => {
+        fake.serverEmit('command:approval', {
+          conversationId: 'c1',
+          command: 'deploy',
+          success: true,
+          approvalId: `ap-${i}`,
+        });
+      });
+      await act(async () => {
+        latest?.actions.runApprovedCommand();
+      });
+    }
+
+    // One more distinct approval once the set is already full. The old
+    // eviction policy would delete the oldest entry (ap-0) to make room and
+    // let this execute; the fixed behavior must deny it instead.
+    await act(async () => {
+      latest?.actions.approveCommand({ command: 'deploy' });
+    });
+    await act(async () => {
+      fake.serverEmit('command:approval', {
+        conversationId: 'c1',
+        command: 'deploy',
+        success: true,
+        approvalId: 'ap-overflow',
+      });
+    });
+    await act(async () => {
+      latest?.actions.runApprovedCommand();
+    });
+
+    // A fresh local approval request, replaying the very first approvalId —
+    // this is the replay the old eviction policy would have let through a
+    // second time because it had forgotten ap-0 ever ran.
+    await act(async () => {
+      latest?.actions.approveCommand({ command: 'deploy' });
+    });
+    await act(async () => {
+      fake.serverEmit('command:approval', {
+        conversationId: 'c1',
+        command: 'deploy',
+        success: true,
+        approvalId: 'ap-0',
+      });
+    });
+    await act(async () => {
+      latest?.actions.runApprovedCommand();
+    });
+
+    const executes = fake.emitted.filter(
+      (e): e is EmittedEvent<'command:execute'> => e.event === 'command:execute',
+    );
+    // Only the original MAX_EXECUTED_APPROVAL_IDS executions ever happened —
+    // neither the overflow ID nor the replay of ap-0 produced a new one.
+    expect(executes).toHaveLength(MAX_EXECUTED_APPROVAL_IDS);
+    expect(executes.filter((e) => e.payload.approvalId === 'ap-0')).toHaveLength(1);
+    expect(executes.some((e) => e.payload.approvalId === 'ap-overflow')).toBe(false);
+  });
+
+  it('does not unlock turn B when a stale same-conversation agent:end from turn A arrives', async () => {
+    // Turn A completes normally on c1.
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+      fake.serverEmit('agent:end', { conversationId: 'c1' });
+    });
+    expect(latest?.state.sending).toBe(false);
+
+    // Turn B is sent (same conversation — the wire gives it no distinct
+    // turn id, only the same conversationId as turn A).
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn B' });
+    });
+    expect(latest?.state.sending).toBe(true);
+
+    // Turn A's agent:end arrives late (network reordering) for the SAME
+    // conversation, before turn B's own ack/start ever arrived. A
+    // conversationId-only check cannot tell this apart from turn B's own
+    // terminal event, so this must not unlock — turn B has not yet been
+    // armed by its own accepted ack/start.
+    await act(async () => {
+      fake.serverEmit('agent:end', { conversationId: 'c1' });
+    });
+    expect(latest?.state.sending).toBe(true);
+    // A recognized-stale terminal must be a true no-op — it must not touch
+    // streaming/error, which legitimately belong to the still in-flight
+    // turn B.
+    expect(latest?.state.streaming).toBe(false);
+    expect(latest?.state.error).toBeNull();
+
+    // An attempted turn C must still be rejected — the lock is still held.
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn C attempt' });
+    });
+    expect(fake.emitted.filter((e) => e.event === 'message')).toHaveLength(1);
+    expect(latest?.state.messages.some((m) => m.text === 'turn C attempt')).toBe(false);
+
+    // Turn B's own, current ack/start arms the lock, and its own terminal
+    // event can then legitimately release it, allowing a later send.
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm2' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+    });
+    await act(async () => {
+      fake.serverEmit('agent:end', { conversationId: 'c1' });
+    });
+    expect(latest?.state.sending).toBe(false);
+
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn D' });
+    });
+    expect(fake.emitted.filter((e) => e.event === 'message')).toHaveLength(2);
+  });
+
+  it('does not unlock turn B when a stale same-conversation error from turn A arrives', async () => {
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+      fake.serverEmit('agent:end', { conversationId: 'c1' });
+    });
+    expect(latest?.state.sending).toBe(false);
+
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn B' });
+    });
+    expect(latest?.state.sending).toBe(true);
+
+    // A stale error for turn A, same conversationId, arrives before turn
+    // B's own ack/start — must not unlock turn B.
+    await act(async () => {
+      fake.serverEmit('error', { conversationId: 'c1', error: 'stale turn A failure' });
+    });
+    expect(latest?.state.sending).toBe(true);
+    // A recognized-stale terminal must be a true no-op — its message must
+    // never be displayed/stored, and it must not touch streaming, which
+    // legitimately belongs to the still in-flight turn B.
+    expect(latest?.state.error).toBeNull();
+    expect(latest?.state.streaming).toBe(false);
+
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn C attempt' });
+    });
+    expect(fake.emitted.filter((e) => e.event === 'message')).toHaveLength(1);
+    expect(latest?.state.messages.some((m) => m.text === 'turn C attempt')).toBe(false);
+
+    // Turn B's own current ack/start arms the lock; its own terminal event
+    // (here, its own error) can then legitimately release it.
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm2' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+    });
+    await act(async () => {
+      fake.serverEmit('error', { conversationId: 'c1', error: 'turn B failed' });
+    });
+    expect(latest?.state.sending).toBe(false);
+
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn D' });
+    });
+    expect(fake.emitted.filter((e) => e.event === 'message')).toHaveLength(2);
+  });
+
+  it('a recognized-stale same-conversation error during an unarmed turn B does not clear approvalRequestPending, does not overwrite the frozen pendingApproval, and does not surface its message', async () => {
+    // Turn A completes normally on c1.
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmit('agent:start', { conversationId: 'c1' });
+      fake.serverEmit('agent:end', { conversationId: 'c1' });
+    });
+    expect(latest?.state.sending).toBe(false);
+
+    // Turn B is sent but has not yet been armed by its own ack/start.
+    await act(async () => {
+      latest?.actions.sendMessage({ content: 'turn B' });
+    });
+    expect(latest?.state.sending).toBe(true);
+
+    // An approval request is outstanding on c1 — approveCommand has no
+    // dependency on `sending`/`streaming`, so this is legitimate even while
+    // turn B is unarmed.
+    await act(async () => {
+      latest?.actions.approveCommand({ command: 'deploy', args: 'prod' });
+    });
+    expect(latest?.state.approvalRequestPending).toBe(true);
+    expect(latest?.state.pendingApproval).toEqual({ command: 'deploy', args: 'prod' });
+    expect(fake.emitted.filter((e) => e.event === 'command:approve')).toHaveLength(1);
+
+    // A stale error from turn A, same conversationId, arrives before turn
+    // B's own ack/start. This must be a true no-op: it must not release
+    // `sending`, must not display/store its message, must not touch
+    // `streaming`, and — critically — must not clear
+    // `approvalRequestPending`/`pendingApproval`, which would re-arm the
+    // approve UI for a request that is still outstanding.
+    await act(async () => {
+      fake.serverEmit('error', { conversationId: 'c1', error: 'stale turn A failure' });
+    });
+
+    expect(latest?.state.sending).toBe(true);
+    expect(latest?.state.approvalRequestPending).toBe(true);
+    expect(latest?.state.pendingApproval).toEqual({ command: 'deploy', args: 'prod' });
+    expect(latest?.state.error).toBeNull();
+    expect(latest?.state.streaming).toBe(false);
+
+    // A second approval attempt while the first is still outstanding must
+    // still be rejected — exactly one command:approve total, and the
+    // original frozen command+args must be unchanged.
+    await act(async () => {
+      latest?.actions.approveCommand({ command: 'deploy', args: 'staging' });
+    });
+    expect(fake.emitted.filter((e) => e.event === 'command:approve')).toHaveLength(1);
+    expect(latest?.state.pendingApproval).toEqual({ command: 'deploy', args: 'prod' });
+  });
+
   it('removes every listener and tears down the socket on cleanup, using no network', async () => {
     const registeredEvents = [...fake.listeners.keys()];
     expect(registeredEvents.length).toBeGreaterThan(0);

apps/web/src/spa/chat/use-chat-connection.ts

@@ -8,7 +8,13 @@ import {
   MAX_STREAM_CHARS,
   MAX_TOOLS,
 } from './limits';
-import { asConversationId, asFiniteNumber, asString, isRecord } from './runtime-guards';
+import {
+  asConversationId,
+  asFiniteNumber,
+  asString,
+  asStringArray,
+  isRecord,
+} from './runtime-guards';
 import type {
   AgentEndPayload,
   AgentStartPayload,
@@ -35,11 +41,64 @@ export interface ToolCallState {
   status: 'running' | 'success' | 'error' | 'anomaly';
 }
 
-/** Appends `addition` to `existing`, keeping at most `max` characters by
+/** Formats the visible marker prepended to a capped stream buffer once any
- * dropping the oldest (leading) characters once the cap is exceeded. */
+ * original characters have been dropped from it. Reconstructing the prior
-function capAppendString(existing: string, addition: string, max: number): string {
+ * tail (see `capAppendStream` below) always slices this exact computed
-  const next = existing + addition;
+ * length off the front of the previous displayed value — it never scans
-  return next.length > max ? next.slice(next.length - max) : next;
+ * buffer content for marker-shaped text, so real streamed content that
+ * happens to look like a marker can never be mistaken for one. */
+function formatTruncationMarker(dropped: number): string {
+  return `…[truncated ${dropped} characters]…`;
+}
+
+interface CappedStream {
+  /** The full value to store/display — a plain tail when nothing has been
+   * dropped yet, otherwise the marker followed by the retained tail. Always
+   * bounded to at most `max` characters in total. */
+  displayed: string;
+  /** Total original stream characters dropped so far, cumulative across
+   * every append — never reset while the buffer is still accumulating. */
+  dropped: number;
+}
+
+/** Appends `addition` to a stream buffer capped at `max` displayed
+ * characters (marker included), honestly disclosing how many original
+ * characters have been dropped so far rather than silently retaining only
+ * the tail. `priorDisplayed`/`priorDropped` come from state; the marker (if
+ * any) already present in `priorDisplayed` is stripped by the exact length
+ * `formatTruncationMarker(priorDropped)` computes, not by pattern-matching. */
+function capAppendStream(
+  priorDisplayed: string,
+  priorDropped: number,
+  addition: string,
+  max: number,
+): CappedStream {
+  const priorTail =
+    priorDropped > 0
+      ? priorDisplayed.slice(formatTruncationMarker(priorDropped).length)
+      : priorDisplayed;
+  const combinedTail = priorTail + addition;
+
+  if (priorDropped === 0 && combinedTail.length <= max) {
+    return { displayed: combinedTail, dropped: 0 };
+  }
+
+  // The marker's own text grows (rarely) as `dropped`'s digit count grows,
+  // which shrinks the budget left for the tail, which can in turn increase
+  // `dropped` further — a handful of iterations is always enough to reach a
+  // fixed point for any realistic character count.
+  let dropped = priorDropped;
+  for (let i = 0; i < 8; i += 1) {
+    const budget = Math.max(0, max - formatTruncationMarker(dropped).length);
+    const nextDropped = priorDropped + Math.max(0, combinedTail.length - budget);
+    if (nextDropped === dropped) break;
+    dropped = nextDropped;
+  }
+
+  const marker = formatTruncationMarker(dropped);
+  const budget = Math.max(0, max - marker.length);
+  const tail = combinedTail.slice(Math.max(0, combinedTail.length - budget));
+  return { displayed: marker + tail, dropped };
 }
 
 /** Pushes `item` onto `arr`, dropping the oldest entries once `max` is exceeded. */
@@ -72,6 +131,17 @@ function isUnrecoverableStartupFailure(state: ChatConnectionState): boolean {
   return state.conversationId === null && state.pendingSend;
 }
 
+/** True when a scoped `agent:end`/`error` is a recognized-stale terminal: a
+ * send is genuinely in flight (`sending`) but the current turn's own
+ * ack/start has not armed `armedTurnToken` yet — so this event must be a
+ * leftover from an earlier turn on the same conversation, not this one's own
+ * terminal. Recognizing this must make the event a true no-op: it may not
+ * finalize/clear transient state (text, thinking, streaming, error,
+ * approvalRequestPending) that belongs to the still in-flight turn. */
+function isRecognizedStaleTerminal(state: ChatConnectionState): boolean {
+  return state.sending && state.armedTurnToken !== state.turnToken;
+}
+
 /** Deterministic, unique-per-event fallback id for a malformed `toolCallId`.
  * Sourced from a monotonically increasing counter carried in state (`toolSeq`)
  * rather than `tools.length`, so it stays collision-free even once `tools` is
@@ -166,7 +236,14 @@ export interface ChatConnectionState {
   ack: MessageAckPayload | null;
   streaming: boolean;
   text: string;
+  /** Total original `agent:text` characters dropped so far by the
+   * MAX_STREAM_CHARS cap on `text` — tracked separately from `text` itself
+   * so the honest cumulative count survives across multiple appends without
+   * re-parsing any marker embedded in the displayed string. */
+  textDroppedChars: number;
   thinking: string;
+  /** Same accounting as `textDroppedChars`, for `thinking`. */
+  thinkingDroppedChars: number;
   tools: ToolCallState[];
   usage: SessionUsagePayload | null;
   sessionInfo: SessionInfoPayload | null;
@@ -189,6 +266,20 @@ export interface ChatConnectionState {
    * tools remain, so fallback ids stay unique across the MAX_TOOLS cap
    * boundary. */
   toolSeq: number;
+  /** Monotonically increasing id for the current in-flight turn, minted at
+   * local send time. Wire payloads (agent:end/error) carry only a
+   * conversationId, not a turn-scoped correlation id — two different turns
+   * on the SAME conversation are indistinguishable on the wire, so this
+   * local counter is what actually tells them apart. */
+  turnToken: number;
+  /** The `turnToken` value (if any) that has been armed to accept a normal
+   * terminal release, set only by an accepted (conversation-scoped)
+   * message:ack or agent:start for the CURRENT token. A same-conversation
+   * agent:end/error may only set `sending: false` when this equals
+   * `turnToken` — otherwise it is a stale terminal event from an earlier
+   * turn on the same conversation and must not unlock a still-in-flight
+   * later turn. Fails closed: an unarmed token can never be unlocked. */
+  armedTurnToken: number | null;
 }
 
 export interface ChatConnectionActions {
@@ -212,7 +303,9 @@ const initialState: ChatConnectionState = {
   ack: null,
   streaming: false,
   text: '',
+  textDroppedChars: 0,
   thinking: '',
+  thinkingDroppedChars: 0,
   tools: [],
   usage: null,
   sessionInfo: null,
@@ -226,6 +319,8 @@ const initialState: ChatConnectionState = {
   messages: [],
   messageSeq: 0,
   toolSeq: 0,
+  turnToken: 0,
+  armedTurnToken: null,
 };
 
 type Action =
@@ -274,7 +369,14 @@ function resolveScopedConversation(
     return { active: true, state };
   }
   if (state.conversationId === null && state.pendingSend) {
-    return { active: true, state: { ...state, conversationId, pendingSend: false } };
+    // The very first scoped event for a brand-new conversation can only belong
+    // to the currently in-flight turn — no prior same-conversation turn exists to
+    // be confused with. Arm the current turnToken so a terminal event (error,
+    // agent:end) arriving before ack/start can still properly release the send lock.
+    return {
+      active: true,
+      state: { ...state, conversationId, pendingSend: false, armedTurnToken: state.turnToken },
+    };
   }
   return { active: false, state: null };
 }
@@ -311,37 +413,61 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
           conversationId,
           pendingSend: false,
           ack: sanitizeAck(payload, conversationId),
+          // The very first scoped event ever received for a brand-new
+          // conversation can only belong to the currently in-flight turn —
+          // no prior same-conversation turn can exist to be confused with.
+          armedTurnToken: state.turnToken,
         };
       }
       if (payload.conversationId !== state.conversationId) return state;
-      return { ...state, ack: sanitizeAck(payload, state.conversationId) };
+      return {
+        ...state,
+        ack: sanitizeAck(payload, state.conversationId),
+        armedTurnToken: state.turnToken,
+      };
     }
 
     case 'server/agent:start': {
       const resolved = resolveScopedConversation(state, action.payload.conversationId);
       if (!resolved.active) return state;
-      return { ...resolved.state, streaming: true, text: '', thinking: '', tools: [], error: null };
+      return {
+        ...resolved.state,
+        streaming: true,
+        text: '',
+        thinking: '',
+        textDroppedChars: 0,
+        thinkingDroppedChars: 0,
+        tools: [],
+        error: null,
+        armedTurnToken: resolved.state.turnToken,
+      };
     }
 
     case 'server/agent:text': {
       const resolved = resolveScopedConversation(state, action.payload.conversationId);
       if (!resolved.active) return state;
-      return {
+      const capped = capAppendStream(
-        ...resolved.state,
+        resolved.state.text,
-        text: capAppendString(resolved.state.text, asString(action.payload.text), MAX_STREAM_CHARS),
+        resolved.state.textDroppedChars,
-      };
+        asString(action.payload.text),
+        MAX_STREAM_CHARS,
+      );
+      return { ...resolved.state, text: capped.displayed, textDroppedChars: capped.dropped };
     }
 
     case 'server/agent:thinking': {
       const resolved = resolveScopedConversation(state, action.payload.conversationId);
       if (!resolved.active) return state;
+      const capped = capAppendStream(
+        resolved.state.thinking,
+        resolved.state.thinkingDroppedChars,
+        asString(action.payload.text),
+        MAX_STREAM_CHARS,
+      );
       return {
         ...resolved.state,
-        thinking: capAppendString(
+        thinking: capped.displayed,
-          resolved.state.thinking,
+        thinkingDroppedChars: capped.dropped,
-          asString(action.payload.text),
-          MAX_STREAM_CHARS,
-        ),
       };
     }
 
@@ -413,12 +539,20 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
             sending: false,
             streaming: false,
             approvalRequestPending: false,
+            armedTurnToken: null,
             error: CONVERSATION_START_FAILURE,
           };
         }
         return state;
       }
       const next = resolved.state;
+      if (isRecognizedStaleTerminal(next)) {
+        // A same-conversation agent:end recognized as stale must be a true
+        // no-op — it must not finalize the stale turn's leftover
+        // text/thinking into a message or reset streaming, both of which
+        // legitimately belong to the still in-flight later turn.
+        return next;
+      }
       const hasContent = next.text.length > 0 || next.thinking.length > 0;
       const messages = hasContent
         ? capPush(
@@ -435,12 +569,23 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
             MAX_MESSAGES,
           )
         : next.messages;
+      // The wire carries only conversationId, not a turn id — a stale
+      // agent:end left over from an EARLIER turn on this SAME conversation
+      // is indistinguishable from this turn's own by conversationId alone.
+      // Only release `sending` when this turn's own accepted ack/start armed
+      // the current token; otherwise this is treated as a stale echo and the
+      // lock stays held (fail closed) so it cannot unlock a later, still
+      // in-flight turn.
+      const canRelease = next.armedTurnToken === next.turnToken;
       return {
         ...next,
         streaming: false,
-        sending: false,
+        sending: canRelease ? false : next.sending,
+        armedTurnToken: canRelease ? null : next.armedTurnToken,
         text: '',
         thinking: '',
+        textDroppedChars: 0,
+        thinkingDroppedChars: 0,
         usage: payload.usage ?? next.usage,
         messages,
         messageSeq: hasContent ? next.messageSeq + 1 : next.messageSeq,
@@ -448,9 +593,23 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
     }
 
     case 'server/session:info': {
-      const resolved = resolveScopedConversation(state, action.payload.conversationId);
+      const { payload } = action;
+      const resolved = resolveScopedConversation(state, payload.conversationId);
       if (!resolved.active) return state;
-      return { ...resolved.state, sessionInfo: action.payload };
+      return {
+        ...resolved.state,
+        sessionInfo: {
+          ...payload,
+          // A hostile/malfunctioning gateway can flood this list; cap it
+          // before it ever reaches state so a render site (e.g. the
+          // thinking-level <select>) can never be forced to lay out an
+          // unbounded number of options.
+          availableThinkingLevels: asStringArray(payload.availableThinkingLevels).slice(
+            0,
+            MAX_MANIFEST_ITEMS,
+          ),
+        },
+      };
     }
 
     case 'server/commands:manifest': {
@@ -512,12 +671,24 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
 
     case 'server/system:reload': {
       const { payload } = action;
+      // Computed once and reused for both `systemReload` and `manifest` —
+      // spreading the raw `payload` into `systemReload` first and only
+      // capping the copy handed to `manifest` left the raw, uncapped
+      // commands/skills sitting in `state.systemReload`. The sanitized
+      // fields are placed after the spread below so they always win.
+      const commands = capList<CommandDef>(payload.commands, MAX_MANIFEST_ITEMS);
+      const skills = capList<SkillCommandDef>(payload.skills, MAX_MANIFEST_ITEMS);
       return {
         ...state,
-        systemReload: { ...payload, message: asString(payload.message, 'Commands reloaded.') },
+        systemReload: {
+          ...payload,
+          commands,
+          skills,
+          message: asString(payload.message, 'Commands reloaded.'),
+        },
         manifest: {
-          commands: capList<CommandDef>(payload.commands, MAX_MANIFEST_ITEMS),
+          commands,
-          skills: capList<SkillCommandDef>(payload.skills, MAX_MANIFEST_ITEMS),
+          skills,
           version: state.manifest?.version ?? 0,
         },
       };
@@ -534,16 +705,31 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
             sending: false,
             streaming: false,
             approvalRequestPending: false,
+            armedTurnToken: null,
             error: CONVERSATION_START_FAILURE,
           };
         }
         return state;
       }
+      const next = resolved.state;
+      if (isRecognizedStaleTerminal(next)) {
+        // Same true-no-op guard as `server/agent:end` above: a
+        // same-conversation error recognized as stale must not display/store
+        // its message, touch streaming, or clear approvalRequestPending —
+        // doing so would re-arm the approve UI for a request that belongs to
+        // the still in-flight later turn while the first remains outstanding.
+        return next;
+      }
+      // Same fail-closed turn-token guard as `server/agent:end` above: a
+      // same-conversation error left over from an earlier, already-finished
+      // turn must not release a later turn's still-in-flight send lock.
+      const canRelease = next.armedTurnToken === next.turnToken;
       return {
-        ...resolved.state,
+        ...next,
         error: asString(payload.error, 'An error occurred.'),
         streaming: false,
-        sending: false,
+        sending: canRelease ? false : next.sending,
+        armedTurnToken: canRelease ? null : next.armedTurnToken,
         // A turn-scoped error also invalidates any approval request awaiting
         // a response — the gateway that just errored is unlikely to still
         // answer it, and the synchronous approveLockRef mirrors this field.
@@ -566,6 +752,12 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
         messageSeq: state.messageSeq + 1,
         error: null,
         sending: true,
+        // Sending a new turn mints a fresh token and immediately clears
+        // terminal eligibility — only THIS turn's own accepted ack/start may
+        // arm it, so a same-conversation terminal left over from the turn
+        // that just finished can never be mistaken for this one's.
+        turnToken: state.turnToken + 1,
+        armedTurnToken: null,
         pendingSend: state.conversationId === null ? true : state.pendingSend,
       };
     }
@@ -579,6 +771,7 @@ function reduce(state: ChatConnectionState, action: Action): ChatConnectionState
         sending: false,
         pendingSend: false,
         approvalRequestPending: false,
+        armedTurnToken: null,
       };
     }
 
@@ -766,12 +959,24 @@ export function useChatConnection(): ChatConnectionValue {
       if (approval?.success !== true) return;
       if (typeof approval.approvalId !== 'string' || approval.approvalId.length === 0) return;
       if (!pendingApproval || pendingApproval.command !== approval.command) return;
-      if (executedApprovalIds.current.has(approval.approvalId)) return;
+      if (executedApprovalIds.current.has(approval.approvalId)) {
+        dispatch({ type: 'local/consume-approval' });
+        return;
+      }
       if (executedApprovalIds.current.size >= MAX_EXECUTED_APPROVAL_IDS) {
-        // Bounded dedup set: evict the oldest entry (Sets iterate in
+        // Security tradeoff, chosen deliberately: this dedup set never
-        // insertion order) so this can never grow without limit.
+        // evicts. Evicting the oldest entry to make room (the old behavior)
-        const oldest = executedApprovalIds.current.values().next().value;
+        // would let a replay of that forgotten ID execute again once it
-        if (oldest !== undefined) executedApprovalIds.current.delete(oldest);
+        // scrolled out of the set — a false negative that lets a privileged
+        // command run twice. Once the set is full, every *unseen* approval
+        // is denied instead. The mounted hook remains fail-closed until
+        // unmounted (lifecycle reset), not recoverable by re-approving — a
+        // false positive/availability cost but a genuine replay of any ID
+        // ever seen by this hook can never execute a second time. Consuming
+        // (rather than silently no-op'ing) releases the UI lock so the
+        // denial is visible/recoverable by remounting.
+        dispatch({ type: 'local/consume-approval' });
+        return;
       }
       executedApprovalIds.current.add(approval.approvalId);
       const socket = getSocket();

apps/web/src/spa/pages/chat-error-boundary.spec.tsx

@@ -2,7 +2,16 @@ import { act } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { createMemoryRouter, RouterProvider, type RouteObject } from 'react-router-dom';
 import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from 'vitest';
-import { ChatRouteErrorBoundary } from './chat-error-boundary';
+
+const { useSessionMock } = vi.hoisted(() => ({
+  useSessionMock: vi.fn(),
+}));
+
+vi.mock('@/lib/auth-client', () => ({
+  useSession: useSessionMock,
+}));
+
+import { routes } from '@/routes';
 
 beforeAll(() => {
   Object.defineProperty(globalThis, 'IS_REACT_ACT_ENVIRONMENT', {
@@ -19,6 +28,25 @@ function Boom(): never {
   throw new Error('render blew up');
 }
 
+/** Recursively clones the real exported route table, replacing only the
+ * `/chat` route's `element` with `<Boom />` — every other route (including
+ * the real `AuthGuard` nesting and the real `/chat` `errorElement`) is left
+ * exactly as exported. This is what makes the test fail if a future change
+ * removes the real route's `errorElement`, unlike a hand-built independent
+ * route tree that could drift from production undetected. */
+function replaceChatElementWithBoom(nodes: RouteObject[]): RouteObject[] {
+  return nodes.map((node) => {
+    const cloned: RouteObject = { ...node };
+    if (cloned.path === '/chat') {
+      cloned.element = <Boom />;
+    }
+    if (cloned.children) {
+      cloned.children = replaceChatElementWithBoom(cloned.children);
+    }
+    return cloned;
+  });
+}
+
 let root: Root | null;
 let container: HTMLElement;
 
@@ -28,13 +56,14 @@ afterEach(async () => {
   });
   document.body.replaceChildren();
   root = null;
+  useSessionMock.mockReset();
 });
 
 describe('ChatRouteErrorBoundary', () => {
   it('renders a recoverable, non-blank fallback when the /chat route element throws during render', async () => {
-    const routeObjects: RouteObject[] = [
+    useSessionMock.mockReturnValue({ data: { user: { id: 'user-1' } }, isPending: false });
-      { path: '/chat', element: <Boom />, errorElement: <ChatRouteErrorBoundary /> },
+
-    ];
+    const routeObjects = replaceChatElementWithBoom(routes);
     const router = createMemoryRouter(routeObjects, { initialEntries: ['/chat'] });
 
     container = document.createElement('div');

apps/web/src/spa/pages/chat.spec.tsx

@@ -2,6 +2,7 @@ import { act } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it, vi } from 'vitest';
 import { createFakeChatSocket } from '@/spa/chat/test-support/fake-chat-socket';
+import { MAX_MANIFEST_ITEMS } from '@/spa/chat/limits';
 
 const { getSocketMock, destroySocketMock } = vi.hoisted(() => ({
   getSocketMock: vi.fn(),
@@ -233,7 +234,7 @@ describe('ChatPage', () => {
     });
   });
 
-  it('shows visible alert surfaces for a server error and a stable failure copy for a failed command result', async () => {
+  it('shows visible alert surfaces for a server error and the structured contract reason for a failed command result', async () => {
     await act(async () => {
       fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
       fake.serverEmit('error', { conversationId: 'c1', error: 'The model is unavailable' });
@@ -241,16 +242,52 @@ describe('ChatPage', () => {
         conversationId: 'c1',
         command: 'model',
         success: false,
-        message: 'raw internal detail: stack trace at line 42',
+        message: 'Unknown model',
       });
     });
 
     const alerts = [...container.querySelectorAll('[role="alert"]')];
     const alertText = alerts.map((node) => node.textContent).join(' ');
     expect(alertText).toContain('The model is unavailable');
-    // Sanitized client copy, not the raw server-provided detail.
+    // The structured, contract-provided denial reason is visibly rendered.
+    expect(alertText).toContain('Unknown model');
+  });
+
+  it('falls back to a stable "Command failed." copy when a failed command result has no usable message', async () => {
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmitRaw('command:result', {
+        conversationId: 'c1',
+        command: 'model',
+        success: false,
+        message: { bad: 'object' },
+      });
+    });
+
+    const alerts = [...container.querySelectorAll('[role="alert"]')];
+    const alertText = alerts.map((node) => node.textContent).join(' ');
     expect(alertText).toContain('Command failed.');
-    expect(alertText).not.toContain('raw internal detail');
+  });
+
+  it('caps availableThinkingLevels before storing and rendering a hostile session payload', async () => {
+    const hostileLevels = Array.from({ length: MAX_MANIFEST_ITEMS + 50 }, (_, i) => `level-${i}`);
+
+    await act(async () => {
+      fake.serverEmit('message:ack', { conversationId: 'c1', messageId: 'm1' });
+      fake.serverEmit('session:info', {
+        conversationId: 'c1',
+        provider: 'anthropic',
+        modelId: 'claude',
+        thinkingLevel: 'level-0',
+        availableThinkingLevels: hostileLevels,
+      });
+    });
+
+    const select = container.querySelector(
+      'select[aria-label="Thinking level"]',
+    ) as HTMLSelectElement;
+    expect(select).toBeTruthy();
+    expect(select.options.length).toBeLessThanOrEqual(MAX_MANIFEST_ITEMS);
   });
 
   it('renders a safe fallback when session:info arrives with a malformed (non-array) availableThinkingLevels, without throwing', async () => {

pnpm-lock.yaml

@@ -253,6 +253,9 @@ importers:
       '@mosaicstack/design-tokens':
         specifier: workspace:^
         version: link:../../packages/design-tokens
+      '@mosaicstack/types':
+        specifier: workspace:^
+        version: link:../../packages/types
       better-auth:
         specifier: ^1.5.5
         version: 1.5.5([email protected])([email protected])([email protected](@electric-sql/[email protected])(@opentelemetry/[email protected])(@types/[email protected])(@types/[email protected])([email protected])([email protected])([email protected]))([email protected]([email protected]))([email protected](@opentelemetry/[email protected])(@playwright/[email protected])([email protected]([email protected]))([email protected]))([email protected]([email protected]))([email protected])([email protected](@types/[email protected])(@types/[email protected])([email protected](@noble/[email protected]))([email protected]))