Fixes #756 (#763)

plugins/discord/src/index.test.ts

@@ -0,0 +1,950 @@
+import { EventEmitter } from 'node:events';
+import type {
+  ChannelConversationRouteDto,
+  ChannelEgressDto,
+  ChannelIngressDto,
+  ChannelIngressPort,
+} from '@mosaicstack/types';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import {
+  createDiscordIngressEnvelope,
+  DiscordPlugin,
+  parseDiscordInteractionBindings,
+  resolveDiscordInteractionActorId,
+  resolveDiscordInteractionBinding,
+  verifyDiscordIngressEnvelope,
+  type DiscordIngressEnvelope,
+  type DiscordInteractionRole,
+  type DiscordPluginConfig,
+} from './index.js';
+
+const SERVICE_TOKEN = 'test-service-token';
+
+interface FakeDiscordMessageOptions {
+  id?: string;
+  guildId?: string;
+  content: string;
+  mentioned?: boolean;
+  userId?: string;
+  channelId?: string;
+  parentChannelId?: string | null;
+  isThread?: boolean;
+  hasThread?: boolean;
+  existingThreadId?: string;
+  fetchedThreadId?: string;
+  createdThreadId?: string;
+  attachments?: Map<string, FakeDiscordAttachment>;
+}
+
+interface FakeDiscordAttachment {
+  id: string;
+  name: string;
+  url: string;
+  contentType: string | null;
+  size?: number;
+}
+
+interface FakeDiscordMessage {
+  id: string;
+  guildId: string;
+  channelId: string;
+  author: { id: string; bot: boolean };
+  mentions: { has(user: { id: string }): boolean };
+  content: string;
+  createdAt: Date;
+  channel: {
+    parentId: string | null;
+    isThread(): boolean;
+    threads?: { fetch(id: string): Promise<{ id: string }> };
+  };
+  attachments: Map<string, FakeDiscordAttachment>;
+  hasThread: boolean;
+  thread: { id: string } | null;
+  startThread: ReturnType<typeof vi.fn>;
+}
+
+interface FakeGatewaySocket extends EventEmitter {
+  connected: boolean;
+  disconnect?: ReturnType<typeof vi.fn>;
+}
+
+interface FakeLifecycleClient extends EventEmitter {
+  user: { id: string; tag: string };
+  login: ReturnType<typeof vi.fn>;
+  destroy: ReturnType<typeof vi.fn>;
+  isReady(): boolean;
+  guilds: { cache: Map<string, object> };
+  channels: { cache: Map<string, object> };
+}
+
+interface DiscordPluginInternals {
+  client: {
+    user: { id: string };
+    isReady(): boolean;
+    channels?: {
+      cache: { get(id: string): { send(options: unknown): Promise<void> } | undefined };
+    };
+  };
+  socket: {
+    connected: boolean;
+    emit: ReturnType<typeof vi.fn>;
+  } | null;
+  conversationRoutes: Map<string, ChannelConversationRouteDto>;
+  handleDiscordMessage(message: FakeDiscordMessage): void | Promise<void>;
+  sendToDiscord(conversationId: string, text: string): Promise<void>;
+}
+
+function lifecyclePlugin(): {
+  plugin: DiscordPlugin;
+  socket: FakeGatewaySocket;
+  client: FakeLifecycleClient;
+} {
+  const socket = Object.assign(new EventEmitter(), {
+    connected: false,
+    disconnect: vi.fn(),
+  });
+  const client = Object.assign(new EventEmitter(), {
+    user: { id: 'bot-001', tag: 'mosaic-bot' },
+    login: vi.fn().mockResolvedValue('token'),
+    destroy: vi.fn().mockResolvedValue(undefined),
+    isReady: (): boolean => true,
+    guilds: { cache: new Map<string, object>() },
+    channels: { cache: new Map<string, object>() },
+  });
+  const plugin = new DiscordPlugin(
+    {
+      token: 'unused',
+      gatewayUrl: 'http://gateway.invalid',
+      serviceToken: SERVICE_TOKEN,
+      allowedGuildIds: ['guild-001'],
+      allowedChannelIds: ['channel-001'],
+      allowedUserIds: ['user-001'],
+      interactionBindings: [
+        {
+          instanceId: 'Nova',
+          agentConfigId: 'agent-config-nova',
+          guildId: 'guild-001',
+          channelId: 'channel-001',
+          pairedUsers: {
+            'user-001': { role: 'operator', mosaicUserId: 'mosaic-user-001' },
+          },
+        },
+      ],
+    },
+    {
+      client: client as never,
+      socketFactory: vi.fn().mockReturnValue(socket) as never,
+    },
+  );
+  return { plugin, socket, client };
+}
+
+function createPlugin(
+  role: DiscordInteractionRole = 'operator',
+  paired = true,
+  ingressPort?: ChannelIngressPort,
+  configOverrides: Partial<DiscordPluginConfig> = {},
+): {
+  plugin: DiscordPlugin;
+  internals: DiscordPluginInternals;
+  emit: ReturnType<typeof vi.fn>;
+} {
+  const plugin = new DiscordPlugin(
+    {
+      token: 'unused',
+      gatewayUrl: 'http://unused',
+      serviceToken: SERVICE_TOKEN,
+      allowedGuildIds: ['guild-001'],
+      allowedChannelIds: ['channel-001'],
+      allowedUserIds: ['user-001'],
+      interactionBindings: [
+        {
+          instanceId: 'Nova',
+          agentConfigId: 'agent-config-nova',
+          guildId: 'guild-001',
+          channelId: 'channel-001',
+          pairedUsers: paired
+            ? {
+                'user-001': { role, mosaicUserId: 'mosaic-user-001' },
+              }
+            : {},
+        },
+      ],
+      ...configOverrides,
+    },
+    { ingressPort },
+  );
+  const emit = vi.fn();
+  const internals = plugin as unknown as DiscordPluginInternals;
+  internals.client = { user: { id: 'bot-001' }, isReady: (): boolean => true };
+  internals.socket = { connected: true, emit };
+  return { plugin, internals, emit };
+}
+
+function fakeMessage(options: FakeDiscordMessageOptions): FakeDiscordMessage {
+  const channelId = options.channelId ?? 'channel-001';
+  const parentChannelId = options.parentChannelId;
+  const existingThreadId = options.existingThreadId;
+  return {
+    id: options.id ?? 'message-001',
+    guildId: options.guildId ?? 'guild-001',
+    channelId,
+    author: { id: options.userId ?? 'user-001', bot: false },
+    mentions: { has: (): boolean => options.mentioned ?? false },
+    content: options.content,
+    createdAt: new Date('2026-07-14T12:00:00.000Z'),
+    channel: {
+      parentId: parentChannelId ?? null,
+      isThread: (): boolean =>
+        options.isThread ?? (parentChannelId !== undefined && parentChannelId !== null),
+      ...(options.fetchedThreadId
+        ? {
+            threads: {
+              fetch: vi.fn().mockResolvedValue({ id: options.fetchedThreadId }),
+            },
+          }
+        : {}),
+    },
+    attachments: options.attachments ?? new Map<string, FakeDiscordAttachment>(),
+    hasThread: options.hasThread ?? existingThreadId !== undefined,
+    thread: existingThreadId ? { id: existingThreadId } : null,
+    startThread: vi.fn().mockResolvedValue({ id: options.createdThreadId ?? 'thread-created-001' }),
+  };
+}
+
+function emittedEnvelope(emit: ReturnType<typeof vi.fn>): DiscordIngressEnvelope {
+  const call = emit.mock.calls[0] as [string, DiscordIngressEnvelope] | undefined;
+  expect(call?.[0]).toBe('message');
+  expect(call?.[1]).toBeDefined();
+  return (
+    call?.[1] ??
+    createDiscordIngressEnvelope(
+      {
+        correlationId: 'unreachable',
+        messageId: 'unreachable',
+        guildId: 'unreachable',
+        channelId: 'unreachable',
+        userId: 'unreachable',
+        conversationId: 'unreachable',
+        content: 'unreachable',
+      },
+      SERVICE_TOKEN,
+    )
+  );
+}
+
+afterEach((): void => {
+  vi.useRealTimers();
+  vi.restoreAllMocks();
+});
+
+describe('Discord binding configuration', () => {
+  it('parses role-only and Mosaic-linked pairings', () => {
+    const bindings = parseDiscordInteractionBindings(
+      JSON.stringify([
+        {
+          instanceId: 'Nova',
+          agentConfigId: 'agent-config-nova',
+          guildId: 'guild-001',
+          channelId: 'channel-001',
+          pairedUsers: {
+            'legacy-user': 'operator',
+            'linked-user': { role: 'admin', mosaicUserId: 'mosaic-admin-001' },
+            'linked-without-id': { role: 'operator' },
+          },
+        },
+      ]),
+    );
+
+    expect(bindings).toHaveLength(1);
+    expect(resolveDiscordInteractionActorId(bindings[0]!, 'legacy-user')).toBeNull();
+    expect(resolveDiscordInteractionActorId(bindings[0]!, 'linked-user')).toBe('mosaic-admin-001');
+    expect(resolveDiscordInteractionActorId(bindings[0]!, 'linked-without-id')).toBeNull();
+    expect(resolveDiscordInteractionActorId(bindings[0]!, 'missing-user')).toBeNull();
+    expect(
+      resolveDiscordInteractionBinding(bindings, 'guild-001', 'channel-001', 'linked-user', 'bind'),
+    ).toBe(bindings[0]);
+    expect(
+      resolveDiscordInteractionBinding(
+        bindings,
+        'guild-001',
+        'channel-001',
+        'linked-without-id',
+        'attach',
+      ),
+    ).toBe(bindings[0]);
+    expect(
+      resolveDiscordInteractionBinding(
+        bindings,
+        'other-guild',
+        'channel-001',
+        'linked-user',
+        'send',
+      ),
+    ).toBeNull();
+  });
+
+  it.each([
+    ['missing value', undefined],
+    ['empty array', '[]'],
+    ['non-object binding', '[null]'],
+    ['missing binding fields', '[{"instanceId":"Nova"}]'],
+    [
+      'empty Discord user ID',
+      '[{"instanceId":"Nova","guildId":"g","channelId":"c","pairedUsers":{"":"operator"}}]',
+    ],
+    [
+      'invalid role-only pairing',
+      '[{"instanceId":"Nova","guildId":"g","channelId":"c","pairedUsers":{"u":"owner"}}]',
+    ],
+    [
+      'non-object pairing',
+      '[{"instanceId":"Nova","guildId":"g","channelId":"c","pairedUsers":{"u":42}}]',
+    ],
+    [
+      'invalid linked pairing',
+      '[{"instanceId":"Nova","guildId":"g","channelId":"c","pairedUsers":{"u":{"role":"admin","mosaicUserId":" "}}}]',
+    ],
+  ])('rejects %s', (_case: string, value: string | undefined) => {
+    expect(() => parseDiscordInteractionBindings(value)).toThrow();
+  });
+});
+
+describe('Discord ingress integrity', () => {
+  it.each([
+    ['guild', { guildIds: ['other'], channelIds: ['channel-001'], userIds: ['user-001'] }],
+    ['channel', { guildIds: ['guild-001'], channelIds: ['other'], userIds: ['user-001'] }],
+    ['user', { guildIds: ['guild-001'], channelIds: ['channel-001'], userIds: ['other'] }],
+  ])('rejects an unallowlisted %s', (_field: string, allowlists) => {
+    const payload = {
+      correlationId: 'correlation-001',
+      messageId: 'message-001',
+      guildId: 'guild-001',
+      channelId: 'channel-001',
+      userId: 'user-001',
+      conversationId: 'Nova:discord:channel-001',
+      content: 'hello',
+    };
+    const envelope = createDiscordIngressEnvelope(payload, SERVICE_TOKEN);
+
+    expect(verifyDiscordIngressEnvelope(envelope, SERVICE_TOKEN, allowlists)).toBeNull();
+  });
+});
+
+describe('Discord adapter lifecycle', () => {
+  it('starts while the in-process gateway is still connecting, then reports connected', async () => {
+    const { plugin, socket, client } = lifecyclePlugin();
+
+    await plugin.start();
+
+    expect(client.login).toHaveBeenCalledWith('unused');
+    expect(await plugin.health()).toEqual({ status: 'degraded' });
+    socket.connected = true;
+    socket.emit('connect');
+    expect(await plugin.health()).toEqual({ status: 'connected' });
+    await plugin.stop();
+    expect(socket.disconnect).toHaveBeenCalledOnce();
+    expect(client.destroy).toHaveBeenCalledOnce();
+  });
+
+  it('keeps running while Socket.IO reconnects after an initial gateway error', async () => {
+    const { plugin, socket } = lifecyclePlugin();
+    const error = vi.spyOn(console, 'error').mockImplementation((): void => undefined);
+
+    await plugin.start();
+    socket.emit('connect_error', new Error('gateway not listening yet'));
+
+    expect(error).toHaveBeenCalledWith(
+      '[discord] Gateway connection error: gateway not listening yet',
+    );
+    expect(await plugin.health()).toEqual({ status: 'degraded' });
+  });
+
+  it('cleans up when Discord login fails', async () => {
+    const { plugin, socket, client } = lifecyclePlugin();
+    client.login.mockRejectedValueOnce(new Error('Discord authentication rejected'));
+
+    await expect(plugin.start()).rejects.toThrow('Discord authentication rejected');
+
+    expect(socket.disconnect).toHaveBeenCalledOnce();
+    expect(client.destroy).toHaveBeenCalledOnce();
+  });
+});
+
+describe('Discord project channel provisioning', () => {
+  it('returns null without a configured guild or visible guild', async () => {
+    const { plugin } = createPlugin();
+    await expect(
+      plugin.createProjectChannel({ id: 'project-1', name: 'Alpha' }),
+    ).resolves.toBeNull();
+
+    const { client } = lifecyclePlugin();
+    const configured = new DiscordPlugin(
+      {
+        token: 'unused',
+        gatewayUrl: 'http://unused',
+        serviceToken: SERVICE_TOKEN,
+        guildId: 'missing-guild',
+        allowedGuildIds: ['guild-001'],
+        allowedChannelIds: ['channel-001'],
+        allowedUserIds: ['user-001'],
+        interactionBindings: [],
+      },
+      { client: client as never },
+    );
+    await expect(
+      configured.createProjectChannel({ id: 'project-1', name: 'Alpha' }),
+    ).resolves.toBeNull();
+  });
+
+  it('creates a normalized Discord project channel', async () => {
+    const create = vi.fn().mockResolvedValue({ id: 'created-channel-001' });
+    const { client } = lifecyclePlugin();
+    client.guilds.cache.set('guild-001', { channels: { create } });
+    const plugin = new DiscordPlugin(
+      {
+        token: 'unused',
+        gatewayUrl: 'http://unused',
+        serviceToken: SERVICE_TOKEN,
+        guildId: 'guild-001',
+        allowedGuildIds: ['guild-001'],
+        allowedChannelIds: ['channel-001'],
+        allowedUserIds: ['user-001'],
+        interactionBindings: [],
+      },
+      { client: client as never },
+    );
+
+    await expect(
+      plugin.createProjectChannel({
+        id: 'project-1',
+        name: ' Project Alpha! ',
+        description: 'Alpha workspace',
+      }),
+    ).resolves.toEqual({ channelId: 'created-channel-001' });
+    expect(create).toHaveBeenCalledWith(
+      expect.objectContaining({ name: 'mosaic-project-alpha', topic: 'Alpha workspace' }),
+    );
+
+    await plugin.createProjectChannel({ id: 'project-2', name: 'Beta' });
+    expect(create).toHaveBeenLastCalledWith(
+      expect.objectContaining({ topic: 'Mosaic project: Beta' }),
+    );
+  });
+});
+
+function egressFor(
+  route: ChannelConversationRouteDto,
+  content = 'agent response',
+): ChannelEgressDto {
+  return {
+    correlationId: 'egress-correlation-001',
+    route,
+    message: {
+      id: 'egress-message-001',
+      channelName: 'discord',
+      channelId: route.responseTarget.channelId,
+      senderId: route.logicalAgentId,
+      senderKind: 'agent',
+      content,
+      contentKind: 'markdown',
+      timestamp: '2026-07-14T12:00:00.000Z',
+      metadata: {},
+    },
+  };
+}
+
+describe('official Discord channel routing', () => {
+  it('normalizes an authorized turn through the shared channel ingress port', async () => {
+    const receive = vi.fn<(ingress: ChannelIngressDto) => Promise<void>>().mockResolvedValue();
+    const { internals, emit } = createPlugin('operator', true, { receive });
+    internals.socket = null;
+
+    await internals.handleDiscordMessage(fakeMessage({ content: 'normalized turn' }));
+
+    expect(emit).not.toHaveBeenCalled();
+    expect(receive).toHaveBeenCalledWith(
+      expect.objectContaining({
+        operation: 'message.send',
+        principal: {
+          channelUserId: 'user-001',
+          role: 'operator',
+          mosaicUserId: 'mosaic-user-001',
+        },
+        message: expect.objectContaining({
+          channelName: 'discord',
+          channelId: 'channel-001',
+          content: 'normalized turn',
+          senderKind: 'user',
+        }),
+        route: expect.objectContaining({
+          logicalAgentId: 'Nova',
+          conversationId: 'Nova:discord:channel-001',
+        }),
+      }),
+    );
+  });
+
+  it('releases a response route when typed ingress rejects', async () => {
+    const receive = vi.fn().mockRejectedValue(new Error('gateway rejected ingress'));
+    const { internals } = createPlugin('operator', true, { receive });
+
+    await expect(
+      internals.handleDiscordMessage(fakeMessage({ content: 'rejected typed ingress' })),
+    ).rejects.toThrow('gateway rejected ingress');
+
+    expect(internals.conversationRoutes).toHaveLength(0);
+  });
+
+  it('routes an authorized untagged parent-channel message and responds in that channel', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({ content: 'channel conversation' });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    const payload = verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN);
+    expect(payload).toMatchObject({
+      channelId: 'channel-001',
+      conversationId: 'Nova:discord:channel-001',
+      content: 'channel conversation',
+    });
+    expect(payload?.threadId).toBeUndefined();
+  });
+
+  it('creates a thread for a mentioned parent-channel message and routes the response there', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({
+      content: '<@bot-001> investigate this topic',
+      mentioned: true,
+      createdThreadId: 'thread-created-001',
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).toHaveBeenCalledOnce();
+    const payload = verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN);
+    expect(payload).toMatchObject({
+      channelId: 'channel-001',
+      conversationId: 'Nova:discord:thread-created-001',
+      content: 'investigate this topic',
+      threadId: 'thread-created-001',
+    });
+  });
+
+  it('fetches and reuses an existing thread that is missing from the cache', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({
+      content: '<@bot-001> continue uncached topic',
+      mentioned: true,
+      hasThread: true,
+      fetchedThreadId: 'thread-fetched-001',
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    expect(verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN)).toMatchObject({
+      conversationId: 'Nova:discord:thread-fetched-001',
+      threadId: 'thread-fetched-001',
+    });
+  });
+
+  it('delivers the agent response to the thread selected by the mentioned turn', async () => {
+    const { internals } = createPlugin();
+    const send = vi.fn().mockResolvedValue(undefined);
+    internals.client = {
+      user: { id: 'bot-001' },
+      isReady: (): boolean => true,
+      channels: {
+        cache: {
+          get: (id: string): { send(options: unknown): Promise<void> } | undefined =>
+            id === 'thread-response-001' ? { send } : undefined,
+        },
+      },
+    };
+
+    await internals.handleDiscordMessage(
+      fakeMessage({
+        content: '<@bot-001> threaded response',
+        mentioned: true,
+        createdThreadId: 'thread-response-001',
+      }),
+    );
+    await internals.sendToDiscord('Nova:discord:thread-response-001', 'agent answer');
+
+    expect(send).toHaveBeenCalledWith(
+      expect.objectContaining({ content: 'agent answer', enforceNonce: true }),
+    );
+  });
+
+  it('reuses a thread already attached to a mentioned message instead of creating another', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({
+      content: '<@bot-001> continue existing topic',
+      mentioned: true,
+      existingThreadId: 'thread-existing-001',
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    expect(verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN)).toMatchObject({
+      conversationId: 'Nova:discord:thread-existing-001',
+      threadId: 'thread-existing-001',
+    });
+  });
+
+  it('keeps an untagged follow-up inside an authorized thread without nesting threads', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({
+      content: 'thread follow-up',
+      channelId: 'thread-001',
+      parentChannelId: 'channel-001',
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    expect(verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN)).toMatchObject({
+      channelId: 'channel-001',
+      conversationId: 'Nova:discord:thread-001',
+      content: 'thread follow-up',
+      threadId: 'thread-001',
+    });
+  });
+
+  it.each([
+    ['guild', { guildId: 'guild-not-allowed' }],
+    ['channel', { channelId: 'channel-not-allowed' }],
+    ['user', { userId: 'user-not-allowed' }],
+  ])(
+    'rejects an unauthorized %s before thread creation or gateway dispatch',
+    async (_boundary: string, override: Partial<FakeDiscordMessageOptions>) => {
+      const { internals, emit } = createPlugin();
+      const message = fakeMessage({
+        content: '<@bot-001> unauthorized topic',
+        mentioned: true,
+        ...override,
+      });
+
+      await internals.handleDiscordMessage(message);
+
+      expect(message.startThread).not.toHaveBeenCalled();
+      expect(emit).not.toHaveBeenCalled();
+    },
+  );
+
+  it.each([
+    ['parent channel', {}],
+    ['existing thread', { channelId: 'thread-unpaired-001', parentChannelId: 'channel-001' }],
+  ])(
+    'rejects an allowlisted but unpaired user in %s',
+    async (_location: string, override: Partial<FakeDiscordMessageOptions>) => {
+      const { internals, emit } = createPlugin('operator', false);
+      const message = fakeMessage({ content: 'unpaired message', ...override });
+
+      await internals.handleDiscordMessage(message);
+
+      expect(message.startThread).not.toHaveBeenCalled();
+      expect(emit).not.toHaveBeenCalled();
+    },
+  );
+
+  it('rejects a paired viewer before thread creation or gateway dispatch', async () => {
+    const { internals, emit } = createPlugin('viewer');
+    const message = fakeMessage({
+      content: '<@bot-001> viewer cannot send',
+      mentioned: true,
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    expect(emit).not.toHaveBeenCalled();
+  });
+
+  it('uses a normal channel ID rather than its category parent for authorization', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({
+      content: 'message from categorized channel',
+      parentChannelId: 'category-001',
+      isThread: false,
+    });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN)).toMatchObject({
+      channelId: 'channel-001',
+      conversationId: 'Nova:discord:channel-001',
+    });
+  });
+
+  it.each([
+    ['parent channel', {}],
+    ['existing thread', { channelId: 'thread-attachment-001', parentChannelId: 'channel-001' }],
+  ])(
+    'preserves an attachment-only turn in an authorized %s',
+    async (_location: string, override: Partial<FakeDiscordMessageOptions>) => {
+      const { internals, emit } = createPlugin();
+      const attachments = new Map<string, FakeDiscordAttachment>([
+        [
+          'attachment-001',
+          {
+            id: 'attachment-001',
+            name: 'diagram.png',
+            url: 'https://cdn.example.invalid/diagram.png',
+            contentType: 'image/png',
+            size: 4_096,
+          },
+        ],
+      ]);
+
+      await internals.handleDiscordMessage(fakeMessage({ content: '', attachments, ...override }));
+
+      expect(verifyDiscordIngressEnvelope(emittedEnvelope(emit), SERVICE_TOKEN)).toMatchObject({
+        content: '',
+        attachments: [
+          {
+            id: 'attachment-001',
+            name: 'diagram.png',
+            contentType: 'image/png',
+            sizeBytes: 4_096,
+          },
+        ],
+      });
+    },
+  );
+
+  it('does not dispatch when Discord cannot create the requested thread', async () => {
+    const { internals, emit } = createPlugin();
+    const message = fakeMessage({ content: '<@bot-001> new topic', mentioned: true });
+    message.startThread.mockRejectedValueOnce(new Error('missing thread permission'));
+
+    await expect(internals.handleDiscordMessage(message)).rejects.toThrow(
+      'missing thread permission',
+    );
+    expect(emit).not.toHaveBeenCalled();
+  });
+
+  it.each(['/approve', '/stop approval-001'])(
+    'rejects operator use of privileged command %s before gateway dispatch',
+    async (command: string) => {
+      const { internals, emit } = createPlugin('operator');
+      const message = fakeMessage({ content: `<@bot-001> ${command}`, mentioned: true });
+
+      await internals.handleDiscordMessage(message);
+
+      expect(message.startThread).not.toHaveBeenCalled();
+      expect(emit).not.toHaveBeenCalled();
+    },
+  );
+
+  it('keeps runtime control commands on the current durable session', async () => {
+    const { internals, emit } = createPlugin('admin');
+    const message = fakeMessage({ content: '<@bot-001> /approve', mentioned: true });
+
+    await internals.handleDiscordMessage(message);
+
+    expect(message.startThread).not.toHaveBeenCalled();
+    expect(emit).toHaveBeenCalledWith('discord:approve', expect.any(Object));
+  });
+
+  it('keeps the stable conversation address independent of a runtime harness', async () => {
+    const first = createPlugin();
+    const second = createPlugin();
+
+    await first.internals.handleDiscordMessage(
+      fakeMessage({ id: 'message-claude', content: 'before runtime handoff' }),
+    );
+    await second.internals.handleDiscordMessage(
+      fakeMessage({ id: 'message-pi', content: 'after runtime handoff' }),
+    );
+
+    const firstPayload = verifyDiscordIngressEnvelope(emittedEnvelope(first.emit), SERVICE_TOKEN);
+    const secondPayload = verifyDiscordIngressEnvelope(emittedEnvelope(second.emit), SERVICE_TOKEN);
+    expect(firstPayload?.conversationId).toBe('Nova:discord:channel-001');
+    expect(secondPayload?.conversationId).toBe(firstPayload?.conversationId);
+  });
+
+  it('rate-limits authorized turns before thread creation or dispatch', async () => {
+    const { internals, emit } = createPlugin('operator', true, undefined, {
+      messageRateLimitPerMinute: 1,
+      threadRateLimitPerMinute: 1,
+    });
+    const error = vi.spyOn(console, 'error').mockImplementation((): void => undefined);
+    const first = fakeMessage({ id: 'rate-first', content: 'first turn' });
+    const second = fakeMessage({
+      id: 'rate-second',
+      content: '<@bot-001> second turn',
+      mentioned: true,
+    });
+
+    await internals.handleDiscordMessage(first);
+    await internals.handleDiscordMessage(second);
+
+    expect(emit).toHaveBeenCalledOnce();
+    expect(second.startThread).not.toHaveBeenCalled();
+    expect(error).toHaveBeenCalledWith(expect.stringContaining('Message rate limit reached'));
+  });
+
+  it('applies a stricter mention-thread rate limit before Discord side effects', async () => {
+    const { internals, emit } = createPlugin('operator', true, undefined, {
+      messageRateLimitPerMinute: 10,
+      threadRateLimitPerMinute: 1,
+    });
+    vi.spyOn(console, 'error').mockImplementation((): void => undefined);
+    const first = fakeMessage({ id: 'thread-rate-first', content: 'first topic', mentioned: true });
+    const second = fakeMessage({
+      id: 'thread-rate-second',
+      content: 'second topic',
+      mentioned: true,
+    });
+
+    await internals.handleDiscordMessage(first);
+    await internals.handleDiscordMessage(second);
+
+    expect(first.startThread).toHaveBeenCalledOnce();
+    expect(second.startThread).not.toHaveBeenCalled();
+    expect(emit).toHaveBeenCalledOnce();
+  });
+
+  it('rejects unconfigured egress and handles missing or failed Discord destinations', async () => {
+    const { plugin, internals } = createPlugin();
+    const route: ChannelConversationRouteDto = {
+      bindingId: 'guild-001:channel-001:Nova',
+      logicalAgentId: 'Nova',
+      conversationId: 'Nova:discord:channel-001',
+      channelName: 'discord',
+      authorizationChannelId: 'channel-001',
+      responseTarget: { channelId: 'channel-001' },
+    };
+
+    await expect(
+      plugin.send(
+        egressFor({
+          ...route,
+          bindingId: 'forged-binding',
+        }),
+      ),
+    ).rejects.toMatchObject({ code: 'invalid_route' });
+    await expect(
+      plugin.send(
+        egressFor({
+          ...route,
+          conversationId: 'Nova:discord:unrelated-conversation',
+        }),
+      ),
+    ).rejects.toMatchObject({ code: 'invalid_route' });
+    await expect(
+      plugin.send({
+        ...egressFor(route),
+        message: { ...egressFor(route).message, channelId: 'other-channel' },
+      }),
+    ).rejects.toMatchObject({ code: 'invalid_route' });
+
+    const forgedSend = vi.fn().mockResolvedValue(undefined);
+    internals.client = {
+      user: { id: 'bot-001' },
+      isReady: (): boolean => true,
+      channels: {
+        cache: {
+          get: (): { send(options: unknown): Promise<void> } => ({ send: forgedSend }),
+        },
+      },
+    };
+    await expect(
+      plugin.send(
+        egressFor({
+          ...route,
+          conversationId: 'Nova:discord:forged-channel',
+          responseTarget: { channelId: 'forged-channel', threadId: 'forged-channel' },
+        }),
+      ),
+    ).rejects.toMatchObject({ code: 'invalid_route' });
+    expect(forgedSend).not.toHaveBeenCalled();
+
+    internals.client = {
+      user: { id: 'bot-001' },
+      isReady: (): boolean => true,
+      channels: { cache: { get: (): undefined => undefined } },
+    };
+    await expect(plugin.send(egressFor(route))).rejects.toMatchObject({
+      code: 'destination_unavailable',
+    });
+    await expect(
+      internals.sendToDiscord('missing-conversation', 'missing route'),
+    ).rejects.toMatchObject({ code: 'invalid_route' });
+
+    vi.useFakeTimers();
+    const send = vi
+      .fn()
+      .mockRejectedValue(Object.assign(new Error('Discord unavailable'), { status: 503 }));
+    internals.client.channels = {
+      cache: { get: (): { send(options: unknown): Promise<void> } => ({ send }) },
+    };
+    const delivery = plugin.send(egressFor(route));
+    const rejection = expect(delivery).rejects.toMatchObject({
+      code: 'delivery_failed',
+      retryable: true,
+    });
+    await vi.runAllTimersAsync();
+    await rejection;
+
+    expect(send).toHaveBeenCalledTimes(3);
+    expect(new Set(send.mock.calls.map(([options]) => options.nonce)).size).toBe(1);
+    expect(send).toHaveBeenCalledWith(
+      expect.objectContaining({ enforceNonce: true, content: 'agent response' }),
+    );
+
+    const permanentSend = vi
+      .fn()
+      .mockRejectedValue(Object.assign(new Error('Discord forbidden'), { status: 403 }));
+    internals.client.channels = {
+      cache: {
+        get: (): { send(options: unknown): Promise<void> } => ({ send: permanentSend }),
+      },
+    };
+    await expect(plugin.send(egressFor(route))).rejects.toMatchObject({
+      code: 'delivery_failed',
+      retryable: false,
+    });
+    expect(permanentSend).toHaveBeenCalledOnce();
+  });
+
+  it('chunks long egress responses at Discord-safe boundaries', async () => {
+    const { plugin, internals } = createPlugin();
+    const send = vi.fn().mockResolvedValue(undefined);
+    internals.client = {
+      user: { id: 'bot-001' },
+      isReady: (): boolean => true,
+      channels: {
+        cache: { get: (): { send(options: unknown): Promise<void> } => ({ send }) },
+      },
+    };
+    const route: ChannelConversationRouteDto = {
+      bindingId: 'guild-001:channel-001:Nova',
+      logicalAgentId: 'Nova',
+      conversationId: 'Nova:discord:channel-001',
+      channelName: 'discord',
+      authorizationChannelId: 'channel-001',
+      responseTarget: { channelId: 'channel-001' },
+    };
+
+    await plugin.send(egressFor(route, `${'a'.repeat(1_500)}\n${'b'.repeat(1_500)}`));
+
+    expect(send).toHaveBeenCalledTimes(2);
+  });
+
+  it('reports channel adapter health without exposing runtime-provider state', async () => {
+    const { plugin, internals } = createPlugin();
+
+    expect(await plugin.health()).toEqual({ status: 'connected' });
+    internals.socket = { connected: false, emit: vi.fn() };
+    expect(await plugin.health()).toEqual({ status: 'degraded' });
+    internals.client = { user: { id: 'bot-001' }, isReady: (): boolean => false };
+    expect(await plugin.health()).toEqual({ status: 'disconnected' });
+    internals.socket = { connected: true, emit: vi.fn() };
+    expect(await plugin.health()).toEqual({ status: 'degraded' });
+  });
+});

plugins/discord/src/index.ts

@@ -1,10 +1,38 @@
-import { createHmac, randomUUID, timingSafeEqual } from 'node:crypto';
-import { ChannelType, Client, GatewayIntentBits, type Message as DiscordMessage } from 'discord.js';
+import { createHash, createHmac, randomUUID, timingSafeEqual } from 'node:crypto';
+import { ChannelDeliveryError } from '@mosaicstack/types';
+import type {
+  ChannelAdapterHealthDto,
+  ChannelAuthorizedPrincipalDto,
+  ChannelConversationRouteDto,
+  ChannelEgressDto,
+  ChannelEgressPort,
+  ChannelIngressDto,
+  ChannelIngressPort,
+  ChannelMessageDto,
+  OfficialChannelAdapter,
+} from '@mosaicstack/types';
+import {
+  ChannelType,
+  Client,
+  GatewayIntentBits,
+  ThreadAutoArchiveDuration,
+  type Message as DiscordMessage,
+} from 'discord.js';
 import { io, type Socket } from 'socket.io-client';
 
+export interface DiscordPluginDependencies {
+  ingressPort?: ChannelIngressPort;
+  client?: Client;
+  socketFactory?: (url: string, options: Parameters<typeof io>[1]) => Socket;
+}
+
 export interface DiscordPluginConfig {
   token: string;
   gatewayUrl: string;
+  /** Maximum authorized turns per Discord user/channel per minute. */
+  messageRateLimitPerMinute?: number;
+  /** Maximum mention-triggered thread routes per Discord user/channel per minute. */
+  threadRateLimitPerMinute?: number;
   /** Shared service credential injected by the approved secret mechanism. */
   serviceToken: string;
   /** Which guild to bind to (single-guild only for v0.1.0). */
@@ -30,13 +58,23 @@ export interface DiscordInteractionUserBinding {
 export type DiscordInteractionPairing = DiscordInteractionRole | DiscordInteractionUserBinding;
 
 export interface DiscordInteractionBinding {
+  /** Stable logical agent identity used in channel conversation routes. */
   instanceId: string;
+  /** Trusted gateway database agent-config ID selected for this binding. */
+  agentConfigId: string;
   guildId: string;
   channelId: string;
   /** Pairing roster keyed by Discord user ID. */
   pairedUsers: Readonly<Record<string, DiscordInteractionPairing>>;
 }
 
+const DEFAULT_MESSAGE_RATE_LIMIT_PER_MINUTE = 30;
+const DEFAULT_THREAD_RATE_LIMIT_PER_MINUTE = 5;
+const RATE_LIMIT_WINDOW_MS = 60_000;
+const DELIVERY_MAX_ATTEMPTS = 3;
+const DELIVERY_RETRY_BASE_MS = 50;
+const MAX_CONVERSATION_ROUTES = 1_000;
+
 const operationRoles: Readonly<
   Record<DiscordInteractionOperation, readonly DiscordInteractionRole[]>
 > = {
@@ -90,6 +128,7 @@ export function parseDiscordInteractionBindings(
     const candidate = binding as Partial<DiscordInteractionBinding>;
     if (
       !candidate.instanceId ||
+      !candidate.agentConfigId ||
       !candidate.guildId ||
       !candidate.channelId ||
       !candidate.pairedUsers ||
@@ -130,6 +169,7 @@ export function parseDiscordInteractionBindings(
     ) as Record<string, DiscordInteractionPairing>;
     return {
       instanceId: candidate.instanceId,
+      agentConfigId: candidate.agentConfigId,
       guildId: candidate.guildId,
       channelId: candidate.channelId,
       pairedUsers,
@@ -154,6 +194,7 @@ export interface DiscordAttachment {
   name: string;
   url: string;
   contentType: string | null;
+  sizeBytes?: number;
 }
 
 export interface DiscordIngressEnvelope {
@@ -229,27 +270,37 @@ export function verifyDiscordIngressEnvelope(
   return envelope.payload;
 }
 
-export class DiscordPlugin {
+export class DiscordPlugin implements OfficialChannelAdapter, ChannelEgressPort {
+  readonly name = 'discord';
+
   private client: Client;
   private socket: Socket | null = null;
-  /** Map Discord channel ID → Mosaic conversation ID. */
-  private channelConversations = new Map<string, string>();
+  /** Bounded last-authorized routes for response-target egress validation. */
+  private conversationRoutes = new Map<string, ChannelConversationRouteDto>();
   /** Track in-flight responses to avoid duplicate streaming. */
   private pendingResponses = new Map<string, string>();
+  private readonly messageRateWindows = new Map<string, number[]>();
+  private readonly threadRateWindows = new Map<string, number[]>();
 
-  constructor(private readonly config: DiscordPluginConfig) {
-    this.client = new Client({
-      intents: [
-        GatewayIntentBits.Guilds,
-        GatewayIntentBits.GuildMessages,
-        GatewayIntentBits.MessageContent,
-        GatewayIntentBits.DirectMessages,
-      ],
-    });
+  constructor(
+    private readonly config: DiscordPluginConfig,
+    private readonly dependencies: DiscordPluginDependencies = {},
+  ) {
+    this.client =
+      dependencies.client ??
+      new Client({
+        intents: [
+          GatewayIntentBits.Guilds,
+          GatewayIntentBits.GuildMessages,
+          GatewayIntentBits.MessageContent,
+          GatewayIntentBits.DirectMessages,
+        ],
+      });
   }
 
   async start(): Promise<void> {
-    this.socket = io(`${this.config.gatewayUrl}/chat`, {
+    const socketFactory = this.dependencies.socketFactory ?? io;
+    this.socket = socketFactory(`${this.config.gatewayUrl}/chat`, {
       auth: { discordServiceToken: this.config.serviceToken },
       transports: ['websocket'],
     });
@@ -276,11 +327,13 @@ export class DiscordPlugin {
 
     this.socket.on('agent:end', (data: { conversationId: string }) => {
       const text = this.pendingResponses.get(data.conversationId);
+      this.pendingResponses.delete(data.conversationId);
       if (text) {
-        this.pendingResponses.delete(data.conversationId);
-        this.sendToDiscord(data.conversationId, text).catch((err: unknown) => {
+        this.sendAgentResponse(data.conversationId, text).catch((err: unknown) => {
           console.error(`[discord] Error sending response for ${data.conversationId}:`, err);
         });
+      } else {
+        this.conversationRoutes.delete(data.conversationId);
       }
     });
 
@@ -288,15 +341,33 @@ export class DiscordPlugin {
       this.pendingResponses.set(data.conversationId, '');
     });
 
-    this.client.on('messageCreate', (message: DiscordMessage) =>
-      this.handleDiscordMessage(message),
-    );
+    this.socket.on('error', (data: { conversationId?: unknown }) => {
+      if (typeof data.conversationId !== 'string') return;
+      this.pendingResponses.delete(data.conversationId);
+      this.conversationRoutes.delete(data.conversationId);
+    });
+
+    this.client.on('messageCreate', (message: DiscordMessage) => {
+      void Promise.resolve(this.handleDiscordMessage(message)).catch((error: unknown): void => {
+        const errorName = error instanceof Error ? error.name : 'UnknownError';
+        console.error(
+          `[discord] Message routing failed. channel=${message.channelId} message=${message.id} error=${errorName}`,
+        );
+      });
+    });
 
     this.client.on('ready', () => {
       console.log(`[discord] Bot logged in as ${this.client.user?.tag}`);
     });
 
-    await this.client.login(this.config.token);
+    try {
+      await this.client.login(this.config.token);
+    } catch (error: unknown) {
+      this.socket.disconnect();
+      this.socket = null;
+      await this.client.destroy();
+      throw error;
+    }
   }
 
   async stop(): Promise<void> {
@@ -304,6 +375,14 @@ export class DiscordPlugin {
     await this.client.destroy();
   }
 
+  async health(): Promise<ChannelAdapterHealthDto> {
+    const discordReady = this.client.isReady();
+    const gatewayConnected = this.socket?.connected === true;
+    if (discordReady && gatewayConnected) return { status: 'connected' };
+    if (discordReady || gatewayConnected) return { status: 'degraded' };
+    return { status: 'disconnected' };
+  }
+
   async createProjectChannel(project: {
     id: string;
     name: string;
@@ -325,77 +404,224 @@ export class DiscordPlugin {
       topic: project.description ?? `Mosaic project: ${project.name}`,
     });
 
-    this.channelConversations.set(channel.id, `discord-${channel.id}`);
+    // A project channel has no logical-agent conversation until a configured
+    // binding authorizes a message. Do not seed a legacy channel-only key.
     return { channelId: channel.id };
   }
 
-  private handleDiscordMessage(message: DiscordMessage): void {
-    if (message.author.bot || !this.client.user) return;
-    if (!message.guildId || !this.isAllowedMessage(message)) return;
+  private handleDiscordMessage(message: DiscordMessage): void | Promise<void> {
+    if (message.author.bot || !this.client.user || !message.guildId) return;
+
+    const authorizationChannelId = this.authorizationChannelId(message);
+    if (!this.isAllowedMessage(message, authorizationChannelId)) return;
 
     const isMention = message.mentions.has(this.client.user);
-    if (!isMention) return;
+    const content = isMention
+      ? message.content.replace(new RegExp(`<@!?${this.client.user.id}>`, 'g'), '').trim()
+      : message.content.trim();
+    if (!content && message.attachments.size === 0) return;
+    const operation = this.interactionOperation(content);
+    const binding = resolveDiscordInteractionBinding(
+      this.config.interactionBindings ?? [],
+      message.guildId,
+      authorizationChannelId,
+      message.author.id,
+      operation,
+    );
+    // Pairing and operation-specific role checks happen before thread creation
+    // or any gateway dispatch, including privileged control events.
+    if (!binding) return;
 
-    const content = message.content
-      .replace(new RegExp(`<@!?${this.client.user.id}>`, 'g'), '')
-      .trim();
-    if (!content) return;
-    if (!this.socket?.connected) {
+    const rateKey = `${message.guildId}:${authorizationChannelId}:${message.author.id}`;
+    if (
+      !this.consumeRateLimit(
+        this.messageRateWindows,
+        rateKey,
+        this.config.messageRateLimitPerMinute ?? DEFAULT_MESSAGE_RATE_LIMIT_PER_MINUTE,
+      )
+    ) {
+      console.error(
+        `[discord] Message rate limit reached. guild=${message.guildId} channel=${authorizationChannelId} user=${message.author.id}`,
+      );
+      return;
+    }
+
+    const createThread = isMention && operation === 'send';
+    if (
+      createThread &&
+      !this.consumeRateLimit(
+        this.threadRateWindows,
+        rateKey,
+        this.config.threadRateLimitPerMinute ?? DEFAULT_THREAD_RATE_LIMIT_PER_MINUTE,
+      )
+    ) {
+      console.error(
+        `[discord] Thread rate limit reached. guild=${message.guildId} channel=${authorizationChannelId} user=${message.author.id}`,
+      );
+      return;
+    }
+
+    if (!this.dependencies.ingressPort && !this.socket?.connected) {
       console.error(
         `[discord] Cannot forward message: not connected to gateway. channel=${message.channelId} message=${message.id}`,
       );
       return;
     }
 
-    const channelId = message.channelId;
-    const parentChannelId = 'parentId' in message.channel ? message.channel.parentId : null;
-    const bindingChannelId = parentChannelId ?? channelId;
-    const binding = resolveDiscordInteractionBinding(
-      this.config.interactionBindings ?? [],
-      message.guildId,
-      bindingChannelId,
-      message.author.id,
-      'send',
+    // Approval/stop commands act on the current durable session. They remain
+    // at the current channel/thread target rather than creating a new topic.
+    const route = this.resolveConversationRoute(
+      message,
+      binding,
+      authorizationChannelId,
+      createThread,
     );
-    if (!binding) return;
-    const conversationId =
-      this.channelConversations.get(channelId) ?? `${binding.instanceId}:discord:${channelId}`;
-    this.channelConversations.set(channelId, conversationId);
+    if (route instanceof Promise) {
+      return route.then((resolved: ChannelConversationRouteDto): void | Promise<void> =>
+        this.dispatchDiscordIngress(message, content, operation, binding, resolved),
+      );
+    }
+    return this.dispatchDiscordIngress(message, content, operation, binding, route);
+  }
 
+  private dispatchDiscordIngress(
+    message: DiscordMessage,
+    content: string,
+    operation: 'send' | 'approve' | 'stop',
+    binding: DiscordInteractionBinding,
+    route: ChannelConversationRouteDto,
+  ): void | Promise<void> {
+    const guildId = message.guildId;
+    if (!guildId) return;
+    if (operation === 'send') this.rememberConversationRoute(route);
+    const correlationId = randomUUID();
+    const ingress: ChannelIngressDto = {
+      correlationId,
+      nativeMessageId: message.id,
+      operation:
+        operation === 'approve'
+          ? 'approval.create'
+          : operation === 'stop'
+            ? 'session.stop'
+            : 'message.send',
+      principal: this.authorizedPrincipal(binding, message.author.id),
+      message: this.channelMessage(message, content, route),
+      route,
+    };
+    if (this.dependencies.ingressPort) {
+      return this.dependencies.ingressPort.receive(ingress).catch((error: unknown) => {
+        if (operation === 'send') this.conversationRoutes.delete(route.conversationId);
+        throw error;
+      });
+    }
+    const socket = this.socket;
+    if (!socket?.connected) {
+      console.error(
+        `[discord] Cannot dispatch routed message: gateway disconnected. channel=${message.channelId} message=${message.id}`,
+      );
+      return;
+    }
+    this.emitDiscordIngress(socket, ingress);
+  }
+
+  private authorizedPrincipal(
+    binding: DiscordInteractionBinding,
+    channelUserId: string,
+  ): ChannelAuthorizedPrincipalDto {
+    const pairing = binding.pairedUsers[channelUserId];
+    if (!pairing) throw new Error('Authorized Discord pairing is unavailable');
+    if (typeof pairing === 'string') return { channelUserId, role: pairing };
+    return {
+      channelUserId,
+      role: pairing.role,
+      ...(pairing.mosaicUserId ? { mosaicUserId: pairing.mosaicUserId } : {}),
+    };
+  }
+
+  private channelMessage(
+    message: DiscordMessage,
+    content: string,
+    route: ChannelConversationRouteDto,
+  ): ChannelMessageDto {
+    const attachments = Array.from(message.attachments.values()).map((attachment) => ({
+      id: attachment.id,
+      name: attachment.name,
+      url: attachment.url,
+      mimeType: attachment.contentType,
+      sizeBytes: attachment.size,
+    }));
+    const firstContentType = attachments[0]?.mimeType;
+    return {
+      id: randomUUID(),
+      channelName: this.name,
+      channelId: route.responseTarget.channelId,
+      senderId: message.author.id,
+      senderKind: 'user',
+      content,
+      contentKind:
+        content.length > 0 ? 'markdown' : firstContentType?.startsWith('image/') ? 'image' : 'file',
+      timestamp:
+        message.createdAt instanceof Date
+          ? message.createdAt.toISOString()
+          : new Date().toISOString(),
+      ...(route.responseTarget.threadId ? { threadId: route.responseTarget.threadId } : {}),
+      ...(attachments.length > 0 ? { attachments } : {}),
+      metadata: {
+        channelMessageId: message.id,
+        guildId: message.guildId ?? '',
+      },
+    };
+  }
+
+  private emitDiscordIngress(socket: Socket, ingress: ChannelIngressDto): void {
     const envelope = createDiscordIngressEnvelope(
       {
-        correlationId: randomUUID(),
-        messageId: message.id,
-        guildId: message.guildId,
-        channelId: bindingChannelId,
-        userId: message.author.id,
-        conversationId,
-        content,
-        threadId: parentChannelId ? channelId : undefined,
-        attachments: Array.from(message.attachments.values()).map((attachment) => ({
+        correlationId: ingress.correlationId,
+        messageId: ingress.nativeMessageId,
+        guildId: String(ingress.message.metadata['guildId'] ?? ''),
+        channelId: ingress.route.authorizationChannelId,
+        userId: ingress.principal.channelUserId,
+        conversationId: ingress.route.conversationId,
+        content: ingress.message.content,
+        ...(ingress.route.responseTarget.threadId
+          ? { threadId: ingress.route.responseTarget.threadId }
+          : {}),
+        attachments: ingress.message.attachments?.map((attachment) => ({
           id: attachment.id,
           name: attachment.name,
           url: attachment.url,
-          contentType: attachment.contentType,
+          contentType: attachment.mimeType,
+          ...(attachment.sizeBytes !== undefined ? { sizeBytes: attachment.sizeBytes } : {}),
         })),
       },
       this.config.serviceToken,
     );
-    this.socket.emit(
-      /^\/approve$/i.test(content)
+    socket.emit(
+      ingress.operation === 'approval.create'
         ? 'discord:approve'
-        : content.startsWith('/stop ')
+        : ingress.operation === 'session.stop'
           ? 'discord:stop'
           : 'message',
       envelope,
     );
   }
 
-  private isAllowedMessage(message: DiscordMessage): boolean {
+  private authorizationChannelId(message: DiscordMessage): string {
+    // A normal guild channel can itself have a category parent. Only Discord
+    // threads inherit authorization from a configured parent text channel.
+    const channel = message.channel as DiscordMessage['channel'] & {
+      isThread?: () => boolean;
+      parentId?: string | null;
+    };
+    const isThread =
+      typeof channel.isThread === 'function'
+        ? channel.isThread()
+        : channel.parentId !== undefined && channel.parentId !== null;
+    return isThread && channel.parentId ? channel.parentId : message.channelId;
+  }
+
+  private isAllowedMessage(message: DiscordMessage, authorizationChannelId: string): boolean {
     const guildId = message.guildId;
-    const parentChannelId = 'parentId' in message.channel ? message.channel.parentId : null;
-    // Threads inherit their authorization boundary from their configured parent.
-    const authorizationChannelId = parentChannelId ?? message.channelId;
     return (
       guildId !== null &&
       includesId(this.config.allowedGuildIds, guildId) &&
@@ -404,31 +630,282 @@ export class DiscordPlugin {
     );
   }
 
-  private async sendToDiscord(conversationId: string, text: string): Promise<void> {
-    const channelId = Array.from(this.channelConversations.entries()).find(
-      ([, convId]) => convId === conversationId,
-    )?.[0];
-
-    if (!channelId) {
-      console.error(`[discord] No channel found for conversation ${conversationId}`);
-      return;
+  private resolveConversationRoute(
+    message: DiscordMessage,
+    binding: DiscordInteractionBinding,
+    authorizationChannelId: string,
+    createThread: boolean,
+  ): ChannelConversationRouteDto | Promise<ChannelConversationRouteDto> {
+    if (authorizationChannelId !== message.channelId) {
+      return this.createConversationRoute(
+        binding,
+        authorizationChannelId,
+        message.channelId,
+        message.channelId,
+      );
+    }
+    if (!createThread) {
+      return this.createConversationRoute(binding, authorizationChannelId, message.channelId);
     }
 
+    if (message.hasThread) {
+      const cachedThread = message.thread;
+      if (cachedThread) {
+        return this.createConversationRoute(
+          binding,
+          authorizationChannelId,
+          cachedThread.id,
+          cachedThread.id,
+        );
+      }
+      if (!('threads' in message.channel)) {
+        return Promise.reject(new Error('Existing Discord thread manager is unavailable'));
+      }
+      return message.channel.threads
+        .fetch(message.id)
+        .then((thread): ChannelConversationRouteDto => {
+          if (!thread) throw new Error('Existing Discord thread is unavailable');
+          return this.createConversationRoute(
+            binding,
+            authorizationChannelId,
+            thread.id,
+            thread.id,
+          );
+        });
+    }
+    return message
+      .startThread({
+        name: `Mosaic conversation ${message.id.slice(-8)}`,
+        autoArchiveDuration: ThreadAutoArchiveDuration.OneHour,
+        reason: 'Authorized Mosaic mention',
+      })
+      .then(
+        (thread): ChannelConversationRouteDto =>
+          this.createConversationRoute(binding, authorizationChannelId, thread.id, thread.id),
+      );
+  }
+
+  private createConversationRoute(
+    binding: DiscordInteractionBinding,
+    authorizationChannelId: string,
+    responseChannelId: string,
+    threadId?: string,
+  ): ChannelConversationRouteDto {
+    // Recompute from configuration on every turn so a stale in-memory map can
+    // never carry a channel-only or differently bound agent identity forward.
+    const conversationId = `${binding.instanceId}:discord:${responseChannelId}`;
+    return {
+      bindingId: `${binding.guildId}:${binding.channelId}:${binding.instanceId}`,
+      logicalAgentId: binding.instanceId,
+      conversationId,
+      channelName: this.name,
+      authorizationChannelId,
+      responseTarget: {
+        channelId: responseChannelId,
+        ...(threadId ? { threadId } : {}),
+      },
+    };
+  }
+
+  private consumeRateLimit(
+    windows: Map<string, number[]>,
+    key: string,
+    limit: number,
+    now = Date.now(),
+  ): boolean {
+    const active = (windows.get(key) ?? []).filter(
+      (timestamp: number): boolean => now - timestamp < RATE_LIMIT_WINDOW_MS,
+    );
+    if (active.length >= Math.max(1, limit)) {
+      windows.set(key, active);
+      return false;
+    }
+    active.push(now);
+    windows.set(key, active);
+    return true;
+  }
+
+  private interactionOperation(content: string): 'send' | 'approve' | 'stop' {
+    if (/^\/approve$/i.test(content)) return 'approve';
+    if (/^\/stop\s+\S+/i.test(content)) return 'stop';
+    return 'send';
+  }
+
+  async send(egress: ChannelEgressDto): Promise<void> {
+    if (!this.isConfiguredRoute(egress.route) || !this.isMessageAlignedWithRoute(egress)) {
+      throw new ChannelDeliveryError(
+        'invalid_route',
+        `Discord egress route is not authorized for conversation ${egress.route.conversationId}`,
+      );
+    }
+    const channelId = egress.route.responseTarget.channelId;
     const channel = this.client.channels.cache.get(channelId);
     if (!channel || !('send' in channel)) {
-      console.error(
-        `[discord] Channel ${channelId} not sendable for conversation ${conversationId}`,
+      throw new ChannelDeliveryError(
+        'destination_unavailable',
+        `Discord destination is unavailable for conversation ${egress.route.conversationId}`,
       );
-      return;
     }
 
-    for (const chunk of this.chunkText(text, 1900)) {
+    const chunks = this.chunkText(egress.message.content, 1900);
+    for (const [chunkIndex, chunk] of chunks.entries()) {
+      await this.sendChunkWithRetry(
+        channel as {
+          send(options: { content: string; nonce: string; enforceNonce: true }): Promise<unknown>;
+        },
+        chunk,
+        egress.correlationId,
+        chunkIndex,
+        egress.route.conversationId,
+      );
+    }
+  }
+
+  private async sendChunkWithRetry(
+    channel: {
+      send(options: { content: string; nonce: string; enforceNonce: true }): Promise<unknown>;
+    },
+    chunk: string,
+    correlationId: string,
+    chunkIndex: number,
+    conversationId: string,
+  ): Promise<void> {
+    const nonce = createHash('sha256')
+      .update(`${correlationId}:${chunkIndex}`)
+      .digest('hex')
+      .slice(0, 25);
+    let lastError: unknown;
+    for (let attempt = 1; attempt <= DELIVERY_MAX_ATTEMPTS; attempt += 1) {
       try {
-        await (channel as { send: (content: string) => Promise<unknown> }).send(chunk);
-      } catch (err: unknown) {
-        console.error(`[discord] Failed to send message to channel ${channelId}:`, err);
+        await channel.send({ content: chunk, nonce, enforceNonce: true });
+        return;
+      } catch (error: unknown) {
+        lastError = error;
+        const retryable = this.isTransientDeliveryError(error);
+        if (!retryable) {
+          throw new ChannelDeliveryError(
+            'delivery_failed',
+            `Discord delivery failed for conversation ${conversationId}`,
+            false,
+            { cause: error },
+          );
+        }
+        if (attempt < DELIVERY_MAX_ATTEMPTS) {
+          await new Promise<void>((resolve): void => {
+            setTimeout(resolve, DELIVERY_RETRY_BASE_MS * 2 ** (attempt - 1));
+          });
+        }
       }
     }
+    throw new ChannelDeliveryError(
+      'delivery_failed',
+      `Discord delivery failed for conversation ${conversationId}`,
+      true,
+      { cause: lastError },
+    );
+  }
+
+  private isTransientDeliveryError(error: unknown): boolean {
+    if (typeof error !== 'object' || error === null) return false;
+    const candidate = error as { status?: unknown; code?: unknown };
+    if (
+      typeof candidate.status === 'number' &&
+      (candidate.status === 429 || candidate.status >= 500)
+    ) {
+      return true;
+    }
+    return (
+      typeof candidate.code === 'string' &&
+      ['ECONNRESET', 'ETIMEDOUT', 'EAI_AGAIN', 'UND_ERR_CONNECT_TIMEOUT'].includes(candidate.code)
+    );
+  }
+
+  private async sendAgentResponse(conversationId: string, text: string): Promise<void> {
+    const route = this.conversationRoutes.get(conversationId);
+    if (!route) {
+      throw new ChannelDeliveryError(
+        'invalid_route',
+        `Discord response route is unavailable for conversation ${conversationId}`,
+      );
+    }
+    try {
+      await this.send({
+        correlationId: randomUUID(),
+        route,
+        message: {
+          id: randomUUID(),
+          channelName: this.name,
+          channelId: route.responseTarget.channelId,
+          senderId: route.logicalAgentId,
+          senderKind: 'agent',
+          content: text,
+          contentKind: 'markdown',
+          timestamp: new Date().toISOString(),
+          ...(route.responseTarget.threadId ? { threadId: route.responseTarget.threadId } : {}),
+          metadata: {},
+        },
+      });
+    } finally {
+      this.conversationRoutes.delete(conversationId);
+    }
+  }
+
+  /** Compatibility wrapper while Socket.IO agent events carry only conversation ID. */
+  private async sendToDiscord(conversationId: string, text: string): Promise<void> {
+    await this.sendAgentResponse(conversationId, text);
+  }
+
+  private rememberConversationRoute(route: ChannelConversationRouteDto): void {
+    if (
+      !this.conversationRoutes.has(route.conversationId) &&
+      this.conversationRoutes.size >= MAX_CONVERSATION_ROUTES
+    ) {
+      throw new ChannelDeliveryError(
+        'delivery_failed',
+        'Discord has reached its active response-route limit',
+        true,
+      );
+    }
+    this.conversationRoutes.set(route.conversationId, route);
+  }
+
+  private isConfiguredRoute(route: ChannelConversationRouteDto): boolean {
+    if (
+      route.channelName !== this.name ||
+      route.conversationId !==
+        `${route.logicalAgentId}:${this.name}:${route.responseTarget.channelId}`
+    ) {
+      return false;
+    }
+    const bindingMatches = (this.config.interactionBindings ?? []).some(
+      (binding): boolean =>
+        route.bindingId === `${binding.guildId}:${binding.channelId}:${binding.instanceId}` &&
+        route.logicalAgentId === binding.instanceId &&
+        route.authorizationChannelId === binding.channelId,
+    );
+    if (!bindingMatches) return false;
+    if (
+      route.responseTarget.channelId === route.authorizationChannelId &&
+      route.responseTarget.threadId === undefined
+    ) {
+      return true;
+    }
+    const observed = this.conversationRoutes.get(route.conversationId);
+    return (
+      observed?.bindingId === route.bindingId &&
+      observed.logicalAgentId === route.logicalAgentId &&
+      observed.authorizationChannelId === route.authorizationChannelId &&
+      observed.responseTarget.channelId === route.responseTarget.channelId &&
+      observed.responseTarget.threadId === route.responseTarget.threadId
+    );
+  }
+
+  private isMessageAlignedWithRoute(egress: ChannelEgressDto): boolean {
+    return (
+      egress.message.channelName === this.name &&
+      egress.message.channelId === egress.route.responseTarget.channelId &&
+      egress.message.threadId === egress.route.responseTarget.threadId
+    );
   }
 
   private chunkText(text: string, maxLength: number): string[] {