nexus/.planning/phases/21-chat-foundation/21-03-PLAN.md

---
phase: 21-chat-foundation
plan: 03
type: execute
wave: 2
depends_on: ["21-01"]
files_modified:
  - server/src/services/chat.ts
  - server/src/routes/chat.ts
  - server/src/app.ts
autonomous: true
requirements: [CHAT-04, CHAT-05, CHAT-06]

must_haves:
  truths:
    - "POST /api/companies/:companyId/conversations creates a conversation row in DB"
    - "GET /api/companies/:companyId/conversations returns paginated list sorted by updatedAt DESC"
    - "POST /api/conversations/:id/messages creates a message and bumps conversation updatedAt"
    - "First message on a title-less conversation auto-sets the title to the first 60 chars"
    - "PATCH /api/conversations/:id can set pinnedAt, archivedAt, and title"
    - "DELETE /api/conversations/:id soft-deletes by setting deletedAt"
  artifacts:
    - path: "server/src/services/chat.ts"
      provides: "chatService factory with all CRUD methods"
      exports: ["chatService"]
    - path: "server/src/routes/chat.ts"
      provides: "chatRoutes factory returning Express Router"
      exports: ["chatRoutes"]
  key_links:
    - from: "server/src/routes/chat.ts"
      to: "server/src/services/chat.ts"
      via: "chatService(db) instantiation"
      pattern: "chatService\\(db\\)"
    - from: "server/src/app.ts"
      to: "server/src/routes/chat.ts"
      via: "api.use(chatRoutes(db))"
      pattern: "chatRoutes\\(db\\)"
    - from: "server/src/services/chat.ts"
      to: "packages/db/src/schema/chat_conversations.ts"
      via: "Drizzle query on chatConversations table"
      pattern: "chatConversations"
---

<objective>
Build the server-side chat service and REST API routes.

Purpose: Provide the backend for conversation CRUD (create, list, update, pin, archive, soft-delete) and message CRUD (create, list) with cursor-based pagination. This is the data layer the UI consumes.
Output: Working API endpoints mounted on the Express app.
</objective>

<execution_context>
@$HOME/.claude/get-shit-done/workflows/execute-plan.md
@$HOME/.claude/get-shit-done/templates/summary.md
</execution_context>

<context>
@.planning/PROJECT.md
@.planning/ROADMAP.md
@.planning/phases/21-chat-foundation/21-RESEARCH.md
@.planning/phases/21-chat-foundation/21-01-SUMMARY.md

<interfaces>
From packages/db/src/schema/chat_conversations.ts (created in Plan 01):
```typescript
export const chatConversations = pgTable("chat_conversations", {
  id: uuid("id").primaryKey().defaultRandom(),
  companyId: uuid("company_id").notNull().references(() => companies.id),
  title: text("title"),
  agentId: uuid("agent_id").references(() => agents.id, { onDelete: "set null" }),
  pinnedAt: timestamp("pinned_at", { withTimezone: true }),
  archivedAt: timestamp("archived_at", { withTimezone: true }),
  deletedAt: timestamp("deleted_at", { withTimezone: true }),
  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
  updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
});
```

From packages/db/src/schema/chat_messages.ts (created in Plan 01):
```typescript
export const chatMessages = pgTable("chat_messages", {
  id: uuid("id").primaryKey().defaultRandom(),
  conversationId: uuid("conversation_id").notNull().references(() => chatConversations.id, { onDelete: "cascade" }),
  role: text("role").notNull(),
  content: text("content").notNull(),
  agentId: uuid("agent_id"),
  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
});
```

From packages/shared/src/validators/chat.ts (created in Plan 01):
```typescript
export const createConversationSchema = z.object({ title: z.string().max(200).optional(), agentId: z.string().uuid().optional() });
export const updateConversationSchema = z.object({ title: z.string().max(200).optional(), agentId: z.string().uuid().nullable().optional(), pinnedAt: z.string().datetime().nullable().optional(), archivedAt: z.string().datetime().nullable().optional() });
export const createMessageSchema = z.object({ role: z.enum(["user", "assistant", "system"]), content: z.string().min(1).max(100_000), agentId: z.string().uuid().optional() });
```

From server/src/routes/authz.ts:
```typescript
export function assertBoard(req: Request): void;
export function assertCompanyAccess(req: Request, companyId: string): void;
```

From server/src/errors.ts:
```typescript
export function notFound(message?: string): HttpError;
export function unprocessable(message: string, issues?: unknown): HttpError;
```
</interfaces>
</context>

<tasks>

<task type="auto">
  <name>Task 1: Create chat service with CRUD operations</name>
  <files>server/src/services/chat.ts</files>
  <read_first>
    - server/src/services/documents.ts (reference for service factory pattern, Drizzle query patterns)
    - server/src/services/activity.ts (reference for simpler service pattern)
    - packages/db/src/schema/chat_conversations.ts (table definition — will exist from Plan 01)
    - packages/db/src/schema/chat_messages.ts (table definition — will exist from Plan 01)
  </read_first>
  <action>
Create `server/src/services/chat.ts` following the `function chatService(db: Db)` factory pattern:

```typescript
import { and, asc, desc, eq, isNull, lt, sql, count } from "drizzle-orm";
import type { Db } from "@paperclipai/db";
import { chatConversations, chatMessages } from "@paperclipai/db";
import { notFound } from "../errors.js";

export function chatService(db: Db) {
  return {
    async listConversations(companyId: string, opts: { cursor?: string; limit?: number; includeArchived?: boolean }) {
      // ...
    },
    async createConversation(companyId: string, data: { title?: string; agentId?: string }) {
      // ...
    },
    async getConversation(id: string) {
      // ...
    },
    async updateConversation(id: string, data: { title?: string; agentId?: string | null; pinnedAt?: string | null; archivedAt?: string | null }) {
      // ...
    },
    async softDeleteConversation(id: string) {
      // ...
    },
    async listMessages(conversationId: string, opts: { cursor?: string; limit?: number }) {
      // ...
    },
    async addMessage(conversationId: string, data: { role: string; content: string; agentId?: string }) {
      // ...
    },
  };
}
```

Implementation details for each method:

**listConversations:**
- `limit` defaults to 30, max 100: `const limit = Math.min(opts.limit ?? 30, 100);`
- Filter: `companyId` matches, `deletedAt IS NULL`. If `includeArchived` is false (default), also filter `archivedAt IS NULL`.
- Cursor: if `opts.cursor` provided, add `lt(chatConversations.updatedAt, new Date(opts.cursor))`
- Order: `desc(chatConversations.updatedAt)`
- Pagination: fetch `limit + 1`, if `rows.length > limit` then `hasMore = true`, return `rows.slice(0, limit)`
- Also do a lateral subquery or second query to get `lastMessagePreview`: for each conversation, get the most recent message content truncated to 100 chars. If that's too complex, return `lastMessagePreview: null` for now and add it in a follow-up.

**createConversation:**
- Insert into `chatConversations` with `companyId`, optional `title`, optional `agentId`
- Return the inserted row

**getConversation:**
- Select where `id` matches and `deletedAt IS NULL`
- Throw `notFound("Conversation not found")` if no row

**updateConversation:**
- Build a partial update object from provided fields
- For `pinnedAt` and `archivedAt`: if value is a string, convert to `new Date(value)`. If value is `null`, set column to `null`.
- Also set `updatedAt: new Date()` on every update
- Use `RETURNING *` to get the updated row

**softDeleteConversation:**
- `UPDATE chat_conversations SET deleted_at = now(), updated_at = now() WHERE id = $id AND deleted_at IS NULL`
- Return the updated row or throw notFound

**listMessages:**
- `limit` defaults to 50, max 200
- Filter: `conversationId` matches
- Cursor: if `opts.cursor` provided, add `lt(chatMessages.createdAt, new Date(opts.cursor))`
- Order: `desc(chatMessages.createdAt)` (most recent first)
- Same pagination pattern as conversations

**addMessage:**
- Insert into `chatMessages` with `conversationId`, `role`, `content`, optional `agentId`
- CRITICAL (Pitfall 3 from RESEARCH.md): After inserting the message, also UPDATE the conversation's `updatedAt` to `now()`:
  ```typescript
  await db.update(chatConversations)
    .set({ updatedAt: new Date() })
    .where(eq(chatConversations.id, conversationId));
  ```
- CRITICAL (Pitfall 5 from RESEARCH.md): Auto-title generation — if this is the first message (role === "user") and the conversation has no title:
  ```typescript
  await db.update(chatConversations)
    .set({ title: data.content.slice(0, 60), updatedAt: new Date() })
    .where(and(eq(chatConversations.id, conversationId), isNull(chatConversations.title)));
  ```
  Use `WHERE title IS NULL` to make it idempotent.
- Return the inserted message row
  </action>
  <verify>
    <automated>cd /opt/nexus && grep -q "export function chatService" server/src/services/chat.ts && grep -q "listConversations" server/src/services/chat.ts && grep -q "addMessage" server/src/services/chat.ts && grep -q "isNull(chatConversations.title)" server/src/services/chat.ts && echo "OK"</automated>
  </verify>
  <acceptance_criteria>
    - server/src/services/chat.ts contains `export function chatService(db: Db)`
    - Contains methods: listConversations, createConversation, getConversation, updateConversation, softDeleteConversation, listMessages, addMessage
    - addMessage updates `chatConversations.updatedAt` after inserting message (Pitfall 3)
    - addMessage auto-sets title when `title IS NULL` using `data.content.slice(0, 60)` (Pitfall 5)
    - listConversations filters `isNull(chatConversations.deletedAt)`
    - listConversations uses `desc(chatConversations.updatedAt)` ordering
    - Pagination uses `limit + 1` pattern with `hasMore` boolean
  </acceptance_criteria>
  <done>Chat service exports a factory function with 7 CRUD methods covering conversation lifecycle (create, list, get, update, soft-delete) and message operations (list, add), including auto-title generation and updatedAt bumping.</done>
</task>

<task type="auto">
  <name>Task 2: Create chat routes and mount in app.ts</name>
  <files>server/src/routes/chat.ts, server/src/app.ts</files>
  <read_first>
    - server/src/routes/activity.ts (reference route factory pattern: function activityRoutes(db: Db): Router)
    - server/src/routes/authz.ts (assertBoard, assertCompanyAccess imports)
    - server/src/app.ts (existing route mounting pattern: api.use(fooRoutes(db)))
    - server/src/middleware/validate.ts (if exists — validation middleware pattern)
  </read_first>
  <action>
Create `server/src/routes/chat.ts`:

```typescript
import { Router } from "express";
import type { Db } from "@paperclipai/db";
import { assertBoard, assertCompanyAccess } from "./authz.js";
import { chatService } from "../services/chat.js";
import { createConversationSchema, updateConversationSchema, createMessageSchema } from "@paperclipai/shared";

export function chatRoutes(db: Db): Router {
  const router = Router();
  const svc = chatService(db);

  // GET /api/companies/:companyId/conversations
  router.get("/companies/:companyId/conversations", async (req, res) => {
    assertBoard(req);
    assertCompanyAccess(req, req.params.companyId!);
    const { cursor, limit, includeArchived } = req.query;
    const result = await svc.listConversations(req.params.companyId!, {
      cursor: cursor as string | undefined,
      limit: limit ? Number(limit) : undefined,
      includeArchived: includeArchived === "true",
    });
    res.json(result);
  });

  // POST /api/companies/:companyId/conversations
  router.post("/companies/:companyId/conversations", async (req, res) => {
    assertBoard(req);
    assertCompanyAccess(req, req.params.companyId!);
    const data = createConversationSchema.parse(req.body);
    const conversation = await svc.createConversation(req.params.companyId!, data);
    res.status(201).json(conversation);
  });

  // GET /api/conversations/:id
  router.get("/conversations/:id", async (req, res) => {
    assertBoard(req);
    const conversation = await svc.getConversation(req.params.id!);
    res.json(conversation);
  });

  // PATCH /api/conversations/:id
  router.patch("/conversations/:id", async (req, res) => {
    assertBoard(req);
    const data = updateConversationSchema.parse(req.body);
    const conversation = await svc.updateConversation(req.params.id!, data);
    res.json(conversation);
  });

  // DELETE /api/conversations/:id
  router.delete("/conversations/:id", async (req, res) => {
    assertBoard(req);
    await svc.softDeleteConversation(req.params.id!);
    res.status(204).end();
  });

  // GET /api/conversations/:id/messages
  router.get("/conversations/:id/messages", async (req, res) => {
    assertBoard(req);
    const { cursor, limit } = req.query;
    const result = await svc.listMessages(req.params.id!, {
      cursor: cursor as string | undefined,
      limit: limit ? Number(limit) : undefined,
    });
    res.json(result);
  });

  // POST /api/conversations/:id/messages
  router.post("/conversations/:id/messages", async (req, res) => {
    assertBoard(req);
    const data = createMessageSchema.parse(req.body);
    const message = await svc.addMessage(req.params.id!, data);
    res.status(201).json(message);
  });

  return router;
}
```

NOTE: Check if existing routes wrap async handlers with a try/catch or rely on Express 5's built-in async error handling. Express 5.1.0 natively handles rejected promises in async route handlers, so no manual try/catch wrapper is needed unless the existing pattern uses one.

Mount in `server/src/app.ts`:
1. Add import at the top with the other route imports: `import { chatRoutes } from "./routes/chat.js";`
2. Add `api.use(chatRoutes(db));` in the route mounting section, after the `activityRoutes` line (around line 158).
  </action>
  <verify>
    <automated>cd /opt/nexus && grep -q "chatRoutes" server/src/routes/chat.ts && grep -q "chatRoutes" server/src/app.ts && grep -q 'companies/:companyId/conversations' server/src/routes/chat.ts && grep -q 'conversations/:id/messages' server/src/routes/chat.ts && echo "OK"</automated>
  </verify>
  <acceptance_criteria>
    - server/src/routes/chat.ts contains `export function chatRoutes(db: Db): Router`
    - server/src/routes/chat.ts contains route `GET /companies/:companyId/conversations`
    - server/src/routes/chat.ts contains route `POST /companies/:companyId/conversations`
    - server/src/routes/chat.ts contains route `GET /conversations/:id`
    - server/src/routes/chat.ts contains route `PATCH /conversations/:id`
    - server/src/routes/chat.ts contains route `DELETE /conversations/:id`
    - server/src/routes/chat.ts contains route `GET /conversations/:id/messages`
    - server/src/routes/chat.ts contains route `POST /conversations/:id/messages`
    - server/src/routes/chat.ts calls `assertBoard(req)` on every route
    - server/src/routes/chat.ts calls `assertCompanyAccess(req, req.params.companyId!)` on company-scoped routes
    - server/src/app.ts contains `import { chatRoutes } from "./routes/chat.js"`
    - server/src/app.ts contains `chatRoutes(db)`
  </acceptance_criteria>
  <done>Chat API routes are mounted on the Express app with 7 endpoints covering conversation CRUD and message CRUD, all gated by assertBoard auth.</done>
</task>

</tasks>

<verification>
- `cd /opt/nexus && pnpm --filter @paperclipai/server exec -- tsc --noEmit` passes
- Routes follow the factory pattern used by all other route files
- Service correctly handles all pitfalls from RESEARCH.md (updatedAt bump, auto-title, soft delete)
</verification>

<success_criteria>
- Chat service has 7 methods covering full conversation + message CRUD
- Chat routes mounted in app.ts with proper auth
- Pagination uses cursor-based approach with hasMore
- Auto-title and updatedAt bump implemented per RESEARCH.md pitfalls
</success_criteria>

<output>
After completion, create `.planning/phases/21-chat-foundation/21-03-SUMMARY.md`
</output>