56 lines
3.8 KiB
Markdown
56 lines
3.8 KiB
Markdown
# Server CLAUDE.md
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Agent-facing guide for `server/apps/api`.
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## Overview
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Hono-based Node.js backend. Owns auth, billing, chat sync, LLM gateway forwarding, and observability. **Multi-instance deployed on Railway** — design all features assuming N>1 instances sharing the same Postgres and Redis.
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## Deployment Model
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- Hosted on **Railway**, multiple instances behind a load balancer.
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- Single CLI role: `api` (see `src/bin/run.ts`). No background polling loops, no fire-and-forget tasks — every write happens inside the request thread.
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- Stateless per-instance: no local state that matters across requests.
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- Cross-instance coordination via Redis Pub/Sub (WebSocket broadcast). DB-level idempotency (`(userId, requestId)` partial unique index on `flux_transaction`) covers retries.
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- Rate limiting is currently **in-memory** (not distributed) — keep this in mind when adding rate-sensitive features.
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## Tech Stack
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Hono, Better Auth (OIDC provider, RS256 JWT), Drizzle ORM, PostgreSQL, Redis, Stripe, OpenTelemetry, Valibot, injeca (DI), tsx.
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## Commands
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```sh
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pnpm -F @proj-airi/api-server dev # dev with dotenvx (.env.local)
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pnpm -F @proj-airi/api-server typecheck
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pnpm -F @proj-airi/api-server exec vitest run # all API tests
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pnpm exec vitest run server/apps/api/src/... # single test file
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pnpm -F @proj-airi/api-server db:generate # drizzle-kit generate
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pnpm -F @proj-airi/api-server db:push # drizzle-kit push
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pnpm -F @proj-airi/api-server auth:generate # better-auth → src/schemas/accounts.ts
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```
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Local API, PostgreSQL, and Redis: `pnpm dev:backend`
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## Architecture Summary
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**Entry & DI**: `src/app.ts` (`createApp()`) → logger, env, OTel, Postgres/Redis, DB migrations, services via `injeca`, routes/middleware. CLI entry `src/bin/run.ts`.
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**Layering**:
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- **Routes** (`src/routes/`): thin — param validation (Valibot), auth guards, error mapping. No business logic here.
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- **Services** (`src/services/`): core business logic and DB transactions.
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- **Schemas** (`src/schemas/`): Drizzle table definitions. Migrations in `@proj-airi/drizzle-migration`.
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**Middleware chain** (`/api/*`): CORS → hono/logger → optional otel → sessionMiddleware → bodyLimit(1MB) → per-route guards. WebSocket `/ws/chat` registered before bodyLimit.
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**Error model**: `ApiError(statusCode, errorCode, message, details)` in `src/utils/error.ts`.
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## Key Design Decisions
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- **Flux read/write separation**: `FluxService` reads (Redis cache-aside), `BillingService` writes (single Postgres tx that mutates `user_flux` and writes the matching `flux_transaction` ledger row). Never put write-balance logic in `flux.ts`.
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- **No async billing pipeline**: debits and credits update balance + ledger in one transaction. The `(user_id, request_id)` partial unique index gives DB-level idempotency for retries; LLM `request log` rows are written best-effort right after the response is delivered.
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- **In-process LLM/TTS router**: `/api/v1/openai` is dispatched by `services/domain/llm-router` reading `LLM_ROUTER_CONFIG` (per-model upstream chain + envelope-encrypted keys). `chat/completions` walks LLM upstreams with key fallback; `audio/speech` delegates to a TTS adapter (`azure` / `dashscope-cosyvoice` / `volcengine`); `audio/voices` returns the adapter's compiled-in catalog. Server handles auth/billing/logging, not model execution.
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- **Redis is cache + pub/sub, not truth**: balance cache, app_settings read cache, WebSocket cross-instance pub/sub. Truth is always Postgres.
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- **Auth**: Better Auth + OIDC. `sessionMiddleware` fills context but doesn't block; `authGuard` returns 401.
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- **Multi-instance safe**: all writes go through Postgres transactions; cross-instance messaging uses Redis Pub/Sub. No async work, no in-process singletons — admin flux grants happen synchronously inside the POST that triggered them.
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