feat(gateway): add plugin host module

apps/gateway/package.json

@@ -18,6 +18,7 @@
     "@mosaic/brain": "workspace:^",
     "@mosaic/coord": "workspace:^",
     "@mosaic/db": "workspace:^",
+    "@mosaic/discord-plugin": "workspace:^",
     "@mosaic/log": "workspace:^",
     "@mosaic/memory": "workspace:^",
     "@mosaic/types": "workspace:^",

apps/gateway/src/app.module.ts

@@ -13,6 +13,7 @@ import { CoordModule } from './coord/coord.module.js';
 import { MemoryModule } from './memory/memory.module.js';
 import { LogModule } from './log/log.module.js';
 import { SkillsModule } from './skills/skills.module.js';
+import { PluginModule } from './plugin/plugin.module.js';
 
 @Module({
   imports: [
@@ -29,6 +30,7 @@ import { SkillsModule } from './skills/skills.module.js';
     MemoryModule,
     LogModule,
     SkillsModule,
+    PluginModule,
   ],
   controllers: [HealthController],
 })

apps/gateway/src/plugin/plugin.interface.ts

@@ -0,0 +1,5 @@
+export interface IChannelPlugin {
+  readonly name: string;
+  start(): Promise<void>;
+  stop(): Promise<void>;
+}

apps/gateway/src/plugin/plugin.module.ts

@@ -0,0 +1,90 @@
+import {
+  Global,
+  Inject,
+  Logger,
+  Module,
+  type OnModuleDestroy,
+  type OnModuleInit,
+} from '@nestjs/common';
+import { DiscordPlugin } from '@mosaic/discord-plugin';
+import { PluginService } from './plugin.service.js';
+import type { IChannelPlugin } from './plugin.interface.js';
+
+export const PLUGIN_REGISTRY = Symbol('PLUGIN_REGISTRY');
+
+class DiscordChannelPluginAdapter implements IChannelPlugin {
+  readonly name = 'discord';
+
+  constructor(private readonly plugin: DiscordPlugin) {}
+
+  async start(): Promise<void> {
+    await this.plugin.start();
+  }
+
+  async stop(): Promise<void> {
+    await this.plugin.stop();
+  }
+}
+
+const DEFAULT_GATEWAY_URL = 'http://localhost:4000';
+
+function createPluginRegistry(logger: Logger): IChannelPlugin[] {
+  const plugins: IChannelPlugin[] = [];
+  const discordToken = process.env['DISCORD_BOT_TOKEN'];
+  const discordGuildId = process.env['DISCORD_GUILD_ID'];
+  const discordGatewayUrl = process.env['DISCORD_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+
+  if (discordToken) {
+    plugins.push(
+      new DiscordChannelPluginAdapter(
+        new DiscordPlugin({
+          token: discordToken,
+          guildId: discordGuildId,
+          gatewayUrl: discordGatewayUrl,
+        }),
+      ),
+    );
+  }
+
+  const telegramToken = process.env['TELEGRAM_BOT_TOKEN'];
+  const telegramGatewayUrl = process.env['TELEGRAM_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+
+  if (telegramToken) {
+    logger.warn(
+      `Telegram plugin requested for ${telegramGatewayUrl}, but @mosaic/telegram-plugin is not implemented yet.`,
+    );
+  }
+
+  return plugins;
+}
+
+@Global()
+@Module({
+  providers: [
+    {
+      provide: PLUGIN_REGISTRY,
+      useFactory: (): IChannelPlugin[] => createPluginRegistry(new Logger('PluginModule')),
+    },
+    PluginService,
+  ],
+  exports: [PluginService, PLUGIN_REGISTRY],
+})
+export class PluginModule implements OnModuleInit, OnModuleDestroy {
+  private readonly logger = new Logger(PluginModule.name);
+
+  constructor(@Inject(PLUGIN_REGISTRY) private readonly plugins: IChannelPlugin[]) {}
+
+  async onModuleInit(): Promise<void> {
+    for (const plugin of this.plugins) {
+      this.logger.log(`Starting plugin: ${plugin.name}`);
+      await plugin.start();
+    }
+  }
+
+  async onModuleDestroy(): Promise<void> {
+    for (const plugin of [...this.plugins].reverse()) {
+      this.logger.log(`Stopping plugin: ${plugin.name}`);
+      await plugin.stop();
+    }
+  }
+}

apps/gateway/src/plugin/plugin.service.ts

@@ -0,0 +1,16 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { PLUGIN_REGISTRY } from './plugin.module.js';
+import type { IChannelPlugin } from './plugin.interface.js';
+
+@Injectable()
+export class PluginService {
+  constructor(@Inject(PLUGIN_REGISTRY) private readonly plugins: IChannelPlugin[]) {}
+
+  getPlugins(): IChannelPlugin[] {
+    return this.plugins;
+  }
+
+  getPlugin(name: string): IChannelPlugin | undefined {
+    return this.plugins.find((plugin: IChannelPlugin) => plugin.name === name);
+  }
+}

docs/scratchpads/41-plugin-host.md

@@ -0,0 +1,30 @@
+# Scratchpad — P5-001 Plugin Host
+
+- Task: P5-001 / issue #41
+- Branch: feat/p5-plugin-host
+- Objective: add global NestJS plugin host module, wire Discord import, register active plugins from env, and attach to AppModule.
+- TDD: skipped as optional for module wiring/integration work; relying on targeted typecheck/lint and module-level situational verification.
+- Constraints: ESM .js imports, explicit @Inject(), follow existing gateway patterns, do not touch TASKS.md.
+
+## Progress Log
+
+- 2026-03-13: session started in worktree; loading gateway/plugin package context.
+- 2026-03-13: implemented initial plugin module, service, interface, and AppModule wiring; pending verification.
+- 2026-03-13: added `@mosaic/discord-plugin` as a gateway workspace dependency and regenerated `pnpm-lock.yaml`.
+- 2026-03-13: built gateway dependency chain so workspace packages exported `dist/*` for clean TypeScript resolution in this fresh worktree.
+- 2026-03-13: verification complete.
+
+## Verification
+
+- `pnpm --filter @mosaic/gateway... build` ✅
+- `pnpm --filter @mosaic/gateway typecheck` ✅
+- `pnpm --filter @mosaic/gateway lint` ✅
+- `pnpm format:check` ✅
+- `pnpm typecheck` ✅
+- `pnpm lint` ✅
+
+## Review
+
+- Automated review: `~/.config/mosaic/tools/codex/codex-code-review.sh --uncommitted`
+- Manual review: diff inspection of gateway plugin host changes
+- Result: no blocker findings

pnpm-lock.yaml

@@ -59,6 +59,9 @@ importers:
       '@mosaic/db':
         specifier: workspace:^
         version: link:../../packages/db
+      '@mosaic/discord-plugin':
+        specifier: workspace:^
+        version: link:../../plugins/discord
       '@mosaic/log':
         specifier: workspace:^
         version: link:../../packages/log