# @core/ai — rules for AI agents

## Purpose
Streaming chat endpoint on the Vercel AI SDK, with versioned system prompts, a tool-calling scaffold and per-response
usage logging (tokens and cost) in the database. Provider and model come from env: nothing is hardcoded. No RAG,
embeddings or chat history storage (store `UIMessage[]` yourself if you need it).

## Map
- `index.ts` — public API: `streamChat`, `getModel`, `setModel`, `recordUsage`, `prompts`, `tools`, `PRICES`.
- `prompts.ts` — **your config**: system prompts with `version`. Bump `version` whenever you change a prompt.
- `tools.ts` — **your config**: tools the model can call (zod `inputSchema` + server-side `execute`).
- `prices.ts` — **your config**: USD per million tokens per `AI_MODEL`, for cost logging.
- `schema.ts` — `ai_usage` table. Depends on `../db` (@core/db).
- `adapters/hono.ts`, `adapters/next.ts` — `POST /ai/chat` returning a UI message stream for `useChat`.

## Integration
1. Requires Node 22+ (AI SDK 7). Env: `AI_MODEL` as `<provider>:<model-id>` plus `AI_PROVIDER_API_KEY`, and install
   that provider package: `anthropic` → `@ai-sdk/anthropic`, `openai` → `@ai-sdk/openai`, also `google`, `mistral`,
   `groq`, `xai`. Or `AI_MODEL=<provider>/<model-id>` with `AI_GATEWAY_API_KEY` (Vercel AI Gateway, no extra package).
   Ask the user which provider and model to use; do not pick one for them.
2. Generate and apply migrations (see `src/lib/db/AGENTS.md`).
3. Hono: `app.route('/ai', aiRoutes({ getUserId: (c) => c.get('user')?.id, requireUser: true }))` after
   `@core/auth`'s `sessionMiddleware` (omit both options without auth).
   Next.js: `app/api/ai/chat/route.ts` → `export const POST = chatRoute({ getUserId, requireUser: true })`.
   Delete the adapter of the framework you don't use.
4. Frontend: `useChat({ transport: new DefaultChatTransport({ api: '/ai/chat' }) })` from `@ai-sdk/react`.
5. Verify: `curl -N -X POST localhost:3000/ai/chat -H 'content-type: application/json' -d '{"messages":[{"id":"1","role":"user","parts":[{"type":"text","text":"hi"}]}]}'`.

## Conventions
- One prompt per use case in `prompts.ts`; pass it with `streamChat({ prompt: 'assistant', … })`.
- Tools authorize inside `execute` using the user id; never trust ids sent by the model.
- Query `ai_usage` for quotas (e.g. tokens per user per day) before calling `streamChat`.
- Tests: `setModel(new MockLanguageModelV4(...))` from `ai/test`.

## Don't
- Don't hardcode a model or API key, and don't call the provider from the browser.
- Don't log prompts or completions with user data in production.
- Don't let tools run destructive actions without an explicit user confirmation step.