diff --git a/apps/gateway/package.json b/apps/gateway/package.json
index ec9c2a0..3498fa4 100644
--- a/apps/gateway/package.json
+++ b/apps/gateway/package.json
@@ -14,6 +14,7 @@
   "dependencies": {
     "@mariozechner/pi-coding-agent": "~0.57.1",
     "@mosaic/auth": "workspace:^",
+    "@mosaic/brain": "workspace:^",
     "@mosaic/db": "workspace:^",
     "@nestjs/common": "^11.0.0",
     "@nestjs/core": "^11.0.0",
diff --git a/apps/gateway/src/app.module.ts b/apps/gateway/src/app.module.ts
index 19e0e85..02adb52 100644
--- a/apps/gateway/src/app.module.ts
+++ b/apps/gateway/src/app.module.ts
@@ -2,11 +2,26 @@ import { Module } from '@nestjs/common';
 import { HealthController } from './health/health.controller.js';
 import { DatabaseModule } from './database/database.module.js';
 import { AuthModule } from './auth/auth.module.js';
+import { BrainModule } from './brain/brain.module.js';
 import { AgentModule } from './agent/agent.module.js';
 import { ChatModule } from './chat/chat.module.js';
+import { ConversationsModule } from './conversations/conversations.module.js';
+import { ProjectsModule } from './projects/projects.module.js';
+import { MissionsModule } from './missions/missions.module.js';
+import { TasksModule } from './tasks/tasks.module.js';
 
 @Module({
-  imports: [DatabaseModule, AuthModule, AgentModule, ChatModule],
+  imports: [
+    DatabaseModule,
+    AuthModule,
+    BrainModule,
+    AgentModule,
+    ChatModule,
+    ConversationsModule,
+    ProjectsModule,
+    MissionsModule,
+    TasksModule,
+  ],
   controllers: [HealthController],
 })
 export class AppModule {}
diff --git a/apps/gateway/src/brain/brain.module.ts b/apps/gateway/src/brain/brain.module.ts
new file mode 100644
index 0000000..41dba54
--- /dev/null
+++ b/apps/gateway/src/brain/brain.module.ts
@@ -0,0 +1,19 @@
+import { Global, Module } from '@nestjs/common';
+import { createBrain, type Brain } from '@mosaic/brain';
+import type { Db } from '@mosaic/db';
+import { DB } from '../database/database.module.js';
+
+export const BRAIN = 'BRAIN';
+
+@Global()
+@Module({
+  providers: [
+    {
+      provide: BRAIN,
+      useFactory: (db: Db): Brain => createBrain(db),
+      inject: [DB],
+    },
+  ],
+  exports: [BRAIN],
+})
+export class BrainModule {}
diff --git a/apps/gateway/src/conversations/conversations.controller.ts b/apps/gateway/src/conversations/conversations.controller.ts
new file mode 100644
index 0000000..1e64eac
--- /dev/null
+++ b/apps/gateway/src/conversations/conversations.controller.ts
@@ -0,0 +1,83 @@
+import {
+  Body,
+  Controller,
+  Delete,
+  Get,
+  HttpCode,
+  HttpStatus,
+  Inject,
+  NotFoundException,
+  Param,
+  Patch,
+  Post,
+  UseGuards,
+} from '@nestjs/common';
+import type { Brain } from '@mosaic/brain';
+import { BRAIN } from '../brain/brain.module.js';
+import { AuthGuard } from '../auth/auth.guard.js';
+import { CurrentUser } from '../auth/current-user.decorator.js';
+import type {
+  CreateConversationDto,
+  UpdateConversationDto,
+  SendMessageDto,
+} from './conversations.dto.js';
+
+@Controller('api/conversations')
+@UseGuards(AuthGuard)
+export class ConversationsController {
+  constructor(@Inject(BRAIN) private readonly brain: Brain) {}
+
+  @Get()
+  async list(@CurrentUser() user: { id: string }) {
+    return this.brain.conversations.findAll(user.id);
+  }
+
+  @Get(':id')
+  async findOne(@Param('id') id: string) {
+    const conversation = await this.brain.conversations.findById(id);
+    if (!conversation) throw new NotFoundException('Conversation not found');
+    return conversation;
+  }
+
+  @Post()
+  async create(@CurrentUser() user: { id: string }, @Body() dto: CreateConversationDto) {
+    return this.brain.conversations.create({
+      userId: user.id,
+      title: dto.title,
+      projectId: dto.projectId,
+    });
+  }
+
+  @Patch(':id')
+  async update(@Param('id') id: string, @Body() dto: UpdateConversationDto) {
+    const conversation = await this.brain.conversations.update(id, dto);
+    if (!conversation) throw new NotFoundException('Conversation not found');
+    return conversation;
+  }
+
+  @Delete(':id')
+  @HttpCode(HttpStatus.NO_CONTENT)
+  async remove(@Param('id') id: string) {
+    const deleted = await this.brain.conversations.remove(id);
+    if (!deleted) throw new NotFoundException('Conversation not found');
+  }
+
+  @Get(':id/messages')
+  async listMessages(@Param('id') id: string) {
+    const conversation = await this.brain.conversations.findById(id);
+    if (!conversation) throw new NotFoundException('Conversation not found');
+    return this.brain.conversations.findMessages(id);
+  }
+
+  @Post(':id/messages')
+  async addMessage(@Param('id') id: string, @Body() dto: SendMessageDto) {
+    const conversation = await this.brain.conversations.findById(id);
+    if (!conversation) throw new NotFoundException('Conversation not found');
+    return this.brain.conversations.addMessage({
+      conversationId: id,
+      role: dto.role,
+      content: dto.content,
+      metadata: dto.metadata,
+    });
+  }
+}
diff --git a/apps/gateway/src/conversations/conversations.dto.ts b/apps/gateway/src/conversations/conversations.dto.ts
new file mode 100644
index 0000000..db7fd04
--- /dev/null
+++ b/apps/gateway/src/conversations/conversations.dto.ts
@@ -0,0 +1,15 @@
+export interface CreateConversationDto {
+  title?: string;
+  projectId?: string;
+}
+
+export interface UpdateConversationDto {
+  title?: string;
+  projectId?: string | null;
+}
+
+export interface SendMessageDto {
+  role: 'user' | 'assistant' | 'system';
+  content: string;
+  metadata?: Record<string, unknown>;
+}
diff --git a/apps/gateway/src/conversations/conversations.module.ts b/apps/gateway/src/conversations/conversations.module.ts
new file mode 100644
index 0000000..19f3912
--- /dev/null
+++ b/apps/gateway/src/conversations/conversations.module.ts
@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { ConversationsController } from './conversations.controller.js';
+
+@Module({
+  controllers: [ConversationsController],
+})
+export class ConversationsModule {}
diff --git a/apps/gateway/src/missions/missions.controller.ts b/apps/gateway/src/missions/missions.controller.ts
new file mode 100644
index 0000000..e7e4c02
--- /dev/null
+++ b/apps/gateway/src/missions/missions.controller.ts
@@ -0,0 +1,60 @@
+import {
+  Body,
+  Controller,
+  Delete,
+  Get,
+  HttpCode,
+  HttpStatus,
+  Inject,
+  NotFoundException,
+  Param,
+  Patch,
+  Post,
+  UseGuards,
+} from '@nestjs/common';
+import type { Brain } from '@mosaic/brain';
+import { BRAIN } from '../brain/brain.module.js';
+import { AuthGuard } from '../auth/auth.guard.js';
+import type { CreateMissionDto, UpdateMissionDto } from './missions.dto.js';
+
+@Controller('api/missions')
+@UseGuards(AuthGuard)
+export class MissionsController {
+  constructor(@Inject(BRAIN) private readonly brain: Brain) {}
+
+  @Get()
+  async list() {
+    return this.brain.missions.findAll();
+  }
+
+  @Get(':id')
+  async findOne(@Param('id') id: string) {
+    const mission = await this.brain.missions.findById(id);
+    if (!mission) throw new NotFoundException('Mission not found');
+    return mission;
+  }
+
+  @Post()
+  async create(@Body() dto: CreateMissionDto) {
+    return this.brain.missions.create({
+      name: dto.name,
+      description: dto.description,
+      projectId: dto.projectId,
+      status: dto.status,
+    });
+  }
+
+  @Patch(':id')
+  async update(@Param('id') id: string, @Body() dto: UpdateMissionDto) {
+    const mission = await this.brain.missions.update(id, dto);
+    if (!mission) throw new NotFoundException('Mission not found');
+    return mission;
+  }
+
+  @Delete(':id')
+  @HttpCode(HttpStatus.NO_CONTENT)
+  async remove(@Param('id') id: string) {
+    const deleted = await this.brain.missions.remove(id);
+    if (!deleted) throw new NotFoundException('Mission not found');
+  }
+}
diff --git a/apps/gateway/src/missions/missions.dto.ts b/apps/gateway/src/missions/missions.dto.ts
new file mode 100644
index 0000000..4c0519b
--- /dev/null
+++ b/apps/gateway/src/missions/missions.dto.ts
@@ -0,0 +1,14 @@
+export interface CreateMissionDto {
+  name: string;
+  description?: string;
+  projectId?: string;
+  status?: 'planning' | 'active' | 'paused' | 'completed' | 'failed';
+}
+
+export interface UpdateMissionDto {
+  name?: string;
+  description?: string | null;
+  projectId?: string | null;
+  status?: 'planning' | 'active' | 'paused' | 'completed' | 'failed';
+  metadata?: Record<string, unknown> | null;
+}
diff --git a/apps/gateway/src/missions/missions.module.ts b/apps/gateway/src/missions/missions.module.ts
new file mode 100644
index 0000000..530bf95
--- /dev/null
+++ b/apps/gateway/src/missions/missions.module.ts
@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { MissionsController } from './missions.controller.js';
+
+@Module({
+  controllers: [MissionsController],
+})
+export class MissionsModule {}
diff --git a/apps/gateway/src/projects/projects.controller.ts b/apps/gateway/src/projects/projects.controller.ts
new file mode 100644
index 0000000..1d6761f
--- /dev/null
+++ b/apps/gateway/src/projects/projects.controller.ts
@@ -0,0 +1,61 @@
+import {
+  Body,
+  Controller,
+  Delete,
+  Get,
+  HttpCode,
+  HttpStatus,
+  Inject,
+  NotFoundException,
+  Param,
+  Patch,
+  Post,
+  UseGuards,
+} from '@nestjs/common';
+import type { Brain } from '@mosaic/brain';
+import { BRAIN } from '../brain/brain.module.js';
+import { AuthGuard } from '../auth/auth.guard.js';
+import { CurrentUser } from '../auth/current-user.decorator.js';
+import type { CreateProjectDto, UpdateProjectDto } from './projects.dto.js';
+
+@Controller('api/projects')
+@UseGuards(AuthGuard)
+export class ProjectsController {
+  constructor(@Inject(BRAIN) private readonly brain: Brain) {}
+
+  @Get()
+  async list() {
+    return this.brain.projects.findAll();
+  }
+
+  @Get(':id')
+  async findOne(@Param('id') id: string) {
+    const project = await this.brain.projects.findById(id);
+    if (!project) throw new NotFoundException('Project not found');
+    return project;
+  }
+
+  @Post()
+  async create(@CurrentUser() user: { id: string }, @Body() dto: CreateProjectDto) {
+    return this.brain.projects.create({
+      name: dto.name,
+      description: dto.description,
+      status: dto.status,
+      ownerId: user.id,
+    });
+  }
+
+  @Patch(':id')
+  async update(@Param('id') id: string, @Body() dto: UpdateProjectDto) {
+    const project = await this.brain.projects.update(id, dto);
+    if (!project) throw new NotFoundException('Project not found');
+    return project;
+  }
+
+  @Delete(':id')
+  @HttpCode(HttpStatus.NO_CONTENT)
+  async remove(@Param('id') id: string) {
+    const deleted = await this.brain.projects.remove(id);
+    if (!deleted) throw new NotFoundException('Project not found');
+  }
+}
diff --git a/apps/gateway/src/projects/projects.dto.ts b/apps/gateway/src/projects/projects.dto.ts
new file mode 100644
index 0000000..8294975
--- /dev/null
+++ b/apps/gateway/src/projects/projects.dto.ts
@@ -0,0 +1,12 @@
+export interface CreateProjectDto {
+  name: string;
+  description?: string;
+  status?: 'active' | 'paused' | 'completed' | 'archived';
+}
+
+export interface UpdateProjectDto {
+  name?: string;
+  description?: string | null;
+  status?: 'active' | 'paused' | 'completed' | 'archived';
+  metadata?: Record<string, unknown> | null;
+}
diff --git a/apps/gateway/src/projects/projects.module.ts b/apps/gateway/src/projects/projects.module.ts
new file mode 100644
index 0000000..3398bf8
--- /dev/null
+++ b/apps/gateway/src/projects/projects.module.ts
@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { ProjectsController } from './projects.controller.js';
+
+@Module({
+  controllers: [ProjectsController],
+})
+export class ProjectsModule {}
diff --git a/apps/gateway/src/tasks/tasks.controller.ts b/apps/gateway/src/tasks/tasks.controller.ts
new file mode 100644
index 0000000..7437c73
--- /dev/null
+++ b/apps/gateway/src/tasks/tasks.controller.ts
@@ -0,0 +1,79 @@
+import {
+  Body,
+  Controller,
+  Delete,
+  Get,
+  HttpCode,
+  HttpStatus,
+  Inject,
+  NotFoundException,
+  Param,
+  Patch,
+  Post,
+  Query,
+  UseGuards,
+} from '@nestjs/common';
+import type { Brain } from '@mosaic/brain';
+import { BRAIN } from '../brain/brain.module.js';
+import { AuthGuard } from '../auth/auth.guard.js';
+import type { CreateTaskDto, UpdateTaskDto } from './tasks.dto.js';
+
+@Controller('api/tasks')
+@UseGuards(AuthGuard)
+export class TasksController {
+  constructor(@Inject(BRAIN) private readonly brain: Brain) {}
+
+  @Get()
+  async list(
+    @Query('projectId') projectId?: string,
+    @Query('missionId') missionId?: string,
+    @Query('status') status?: string,
+  ) {
+    if (projectId) return this.brain.tasks.findByProject(projectId);
+    if (missionId) return this.brain.tasks.findByMission(missionId);
+    if (status)
+      return this.brain.tasks.findByStatus(
+        status as Parameters<typeof this.brain.tasks.findByStatus>[0],
+      );
+    return this.brain.tasks.findAll();
+  }
+
+  @Get(':id')
+  async findOne(@Param('id') id: string) {
+    const task = await this.brain.tasks.findById(id);
+    if (!task) throw new NotFoundException('Task not found');
+    return task;
+  }
+
+  @Post()
+  async create(@Body() dto: CreateTaskDto) {
+    return this.brain.tasks.create({
+      title: dto.title,
+      description: dto.description,
+      status: dto.status,
+      priority: dto.priority,
+      projectId: dto.projectId,
+      missionId: dto.missionId,
+      assignee: dto.assignee,
+      tags: dto.tags,
+      dueDate: dto.dueDate ? new Date(dto.dueDate) : undefined,
+    });
+  }
+
+  @Patch(':id')
+  async update(@Param('id') id: string, @Body() dto: UpdateTaskDto) {
+    const task = await this.brain.tasks.update(id, {
+      ...dto,
+      dueDate: dto.dueDate ? new Date(dto.dueDate) : dto.dueDate === null ? null : undefined,
+    });
+    if (!task) throw new NotFoundException('Task not found');
+    return task;
+  }
+
+  @Delete(':id')
+  @HttpCode(HttpStatus.NO_CONTENT)
+  async remove(@Param('id') id: string) {
+    const deleted = await this.brain.tasks.remove(id);
+    if (!deleted) throw new NotFoundException('Task not found');
+  }
+}
diff --git a/apps/gateway/src/tasks/tasks.dto.ts b/apps/gateway/src/tasks/tasks.dto.ts
new file mode 100644
index 0000000..3acaa07
--- /dev/null
+++ b/apps/gateway/src/tasks/tasks.dto.ts
@@ -0,0 +1,24 @@
+export interface CreateTaskDto {
+  title: string;
+  description?: string;
+  status?: 'not-started' | 'in-progress' | 'blocked' | 'done' | 'cancelled';
+  priority?: 'critical' | 'high' | 'medium' | 'low';
+  projectId?: string;
+  missionId?: string;
+  assignee?: string;
+  tags?: string[];
+  dueDate?: string;
+}
+
+export interface UpdateTaskDto {
+  title?: string;
+  description?: string | null;
+  status?: 'not-started' | 'in-progress' | 'blocked' | 'done' | 'cancelled';
+  priority?: 'critical' | 'high' | 'medium' | 'low';
+  projectId?: string | null;
+  missionId?: string | null;
+  assignee?: string | null;
+  tags?: string[] | null;
+  dueDate?: string | null;
+  metadata?: Record<string, unknown> | null;
+}
diff --git a/apps/gateway/src/tasks/tasks.module.ts b/apps/gateway/src/tasks/tasks.module.ts
new file mode 100644
index 0000000..0bf92cf
--- /dev/null
+++ b/apps/gateway/src/tasks/tasks.module.ts
@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { TasksController } from './tasks.controller.js';
+
+@Module({
+  controllers: [TasksController],
+})
+export class TasksModule {}
diff --git a/docs/TASKS.md b/docs/TASKS.md
index 2d93b72..7ba69bb 100644
--- a/docs/TASKS.md
+++ b/docs/TASKS.md
@@ -17,8 +17,8 @@
 | P1-002 | done        | Phase 1   | Auth middleware — BetterAuth session validation               | #71 | #11   |
 | P1-003 | done        | Phase 1   | @mosaic/brain — migrate from v0, PG backend                   | #71 | #12   |
 | P1-004 | done        | Phase 1   | @mosaic/queue — migrate from v0                               | #71 | #13   |
-| P1-005 | not-started | Phase 1   | Gateway routes — conversations CRUD + messages                | —   | #14   |
-| P1-006 | not-started | Phase 1   | Gateway routes — tasks, projects, missions CRUD               | —   | #15   |
+| P1-005 | done        | Phase 1   | Gateway routes — conversations CRUD + messages                | #72 | #14   |
+| P1-006 | done        | Phase 1   | Gateway routes — tasks, projects, missions CRUD               | #72 | #15   |
 | P1-007 | done        | Phase 1   | WebSocket server — chat streaming                             | #61 | #16   |
 | P1-008 | done        | Phase 1   | Basic agent dispatch — single provider                        | #61 | #17   |
 | P1-009 | not-started | Phase 1   | Verify Phase 1 — gateway functional, API tested               | —   | #18   |
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index d336b64..8e3b27c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -47,6 +47,9 @@ importers:
       '@mosaic/auth':
         specifier: workspace:^
         version: link:../../packages/auth
+      '@mosaic/brain':
+        specifier: workspace:^
+        version: link:../../packages/brain
       '@mosaic/db':
         specifier: workspace:^
         version: link:../../packages/db