# AGENTS.md

Compact, repo-specific notes for AI agents. Generic language/framework knowledge is omitted — only things that will bite you if you don't know. Pair this with `README.md` (user-facing quick-start + add-a-feature checklist + deploy flow).

## Stack & runtime

- **Bun-only** (`mise.toml` pins `bun = 1.3.13`). Never invoke `npm`/`npx`/`node`/`yarn`/`pnpm`. Use `bun run <script>` (bare `bun <script>` can collide with Bun built-in subcommands).
- TanStack Start (React 19 SSR, file-routed) + Vite 8 + Nitro (nightly, preset `bun`). Vite dev port is **strict 3000**.
- PostgreSQL + **Drizzle ORM `0.45.2` (0.x, NOT 1.0 beta)** — see "Drizzle" section, this matters a lot.
- ORPC (contract-first), TanStack Query v5, Tailwind v4.

## Scripts

```bash
bun run dev          # bunx --bun vite dev  (localhost:3000)
bun run build        # bunx --bun vite build → .output/
bun run compile      # bun compile.ts → out/server-<target> (standalone CLI binary)
bun run cli <cmd>    # bun bin.ts <cmd>  — run a CLI subcommand in source (dev)
bun run typecheck    # tsc --noEmit
bun run test         # bun test  — runs all *.test.ts files (colocated with source)
bun run fix          # biome check --write  (lint + format + organize imports)
bun run db:push      # dev only — push schema to DB, no migration file
bun run db:generate  # drizzle-kit generate && embed-migrations.ts (regenerates migrations.gen.ts)
bun run db:embed     # embed-migrations.ts only — regenerate migrations.gen.ts from ./drizzle/
bun run db:migrate   # apply migrations via drizzle-kit (local dev convenience; prod uses ./server migrate)
bun run db:studio    # Drizzle Studio
```

Cross-compile targets live under `compile:{linux,darwin,windows}[:arch]`. `compile.ts` accepts `--target bun-<os>-<arch>`; default derives from host.

Before committing: `bun run fix && bun run typecheck && bun run test`. No CI, no pre-commit hooks, no lint-staged — so these are on you.

## Drizzle (v0.x — critical)

**Why it matters:** the project was on 1.0 beta and was rolled back. Online docs default to 1.0 beta APIs that do NOT exist here. If typecheck complains, you are probably importing a 1.0 beta API.

- Driver: `drizzle-orm/postgres-js`. Do NOT use `drizzle-orm/bun-sql`.
- `drizzle()` is called with `{ connection, schema }` where `schema = import * as schema from '@/server/db/schema'`. There is **no `relations.ts`** and **no `defineRelations`** in 0.x.
- Zod generators live in the separate `drizzle-zod` package (`^0.8.3`). Import from `drizzle-zod`, **not** `drizzle-orm/zod` (that subpath only exists in 1.0 beta).
- Relational queries use **RQB v1 callback syntax**:
  ```ts
  db.query.todoTable.findMany({
    orderBy: (t, { desc }) => desc(t.createdAt),
  })
  ```
  Do NOT use the v2 object form (`orderBy: { createdAt: 'desc' }`, `where: { id }`) — it won't type-check.
- To add relations later: declare per-table with `relations()` from `drizzle-orm` and export them from the same file as the table; they get picked up automatically because `index.ts` does `drizzle({ schema })` via `import *`.
- Every table must spread `...generatedFields` from `src/server/db/fields.ts` (`id` UUIDv7 via `$defaultFn(uuidv7)`, `createdAt`, `updatedAt` with `$onUpdateFn`). `generatedFieldKeys` (hand-written `as const`) feeds `createInsertSchema(...).omit(...)`.
- `src/server/db/index.ts` exports a module-level `const db = drizzle(...)` — not a lazy singleton. On Bun this is a long-lived process, so top-level side effects are fine and requested. Don't reintroduce `getDB/closeDB` ceremony; the Nitro shutdown plugin calls `db.$client.end()` directly. (Cloudflare Workers would need per-request init — we don't support that deployment target.)
- `drizzle.config.ts` runs outside Vite — `@/*` path aliases do NOT resolve there. It currently does `import { env } from './src/env'` (relative). Preserve that.
- **Migrations are embedded in the binary, not read from disk.** `bun run db:generate` chains `drizzle-kit generate && bun embed-migrations.ts`, which regenerates `src/server/db/migrations.gen.ts` (committed, AUTO-GENERATED header) by `import sql_<idx> from '../../../drizzle/<tag>.sql' with { type: 'text' }`. `src/cli/migrate.ts` reads `embeddedMigrations`, computes SHA-256 hashes at runtime, and applies pending entries via `db.execute(sql\`...\`)` + `db.transaction(...)` against the `drizzle.__drizzle_migrations` book-keeping table — public APIs only, no `db.dialect`/`db.session` (those are `@internal`). Dev helpers `db:push` / `drizzle-kit migrate` still read `./drizzle/`.

## CLI & single-binary deploy

`bun run compile` produces a single executable that dispatches subcommands via [citty](https://github.com/unjs/citty). Entry is `bin.ts` at repo root, subcommands live in `src/cli/`.

```
./server [serve]   # default — start the HTTP server
./server migrate   # apply migrations from ./drizzle
./server --help
```

**Nitro side-effect pitfall (important).** Under the `bun` preset, `.output/server/index.mjs` has a top-level `serve(...)` call — merely importing it starts the HTTP server. `bin.ts` therefore must not eager-import any subcommand module, and `src/cli/serve.ts` reaches `.output/server/index.mjs` through the `src/cli/_serve-nitro.mjs` bridge (with `_serve-nitro.d.mts` for types, since `.output/` doesn't exist at typecheck time). Citty's `subCommands: { x: () => import('...') }` lazy-loader is what keeps `--help` and `migrate` from booting the server.

**Citty eager-loads subcommand modules for `--help`** to read each subcommand's `meta`. So every `src/cli/*.ts` module body must be side-effect-free: do NOT static-import `@/env`, `@/server/db/*`, or anything that reads env at module-load time. Use `await import('@/env')` inside `run()`. Otherwise `./server --help` (or any subcommand's help) will fail with env validation errors before printing.

Add a subcommand: drop a file in `src/cli/` that default-exports `defineCommand({...})`, then register it in `bin.ts`'s `subCommands` with a `() => import(...)` thunk. Keep top-level imports limited to `citty` + Node built-ins; pull env / db / etc. via `await import(...)` inside `run()`.

**Deploy flow is always migrate-then-serve.** Migrations are embedded in the binary (see "Drizzle" section), so the binary is the only artifact — no `./drizzle/` directory at runtime. Dockerfile copies just `./server`. `compose.yaml` models the pattern with a one-shot `migrate` service that `app` `depends_on: service_completed_successfully`. On k8s, run `./server migrate` as an initContainer or a Helm `pre-upgrade` Job; run `./server` (= `./server serve`) as the main container.

## Compile flags

`compile.ts` builds with `--minify --bytecode --sourcemap=inline`:

- **`bytecode`** — pre-compiles JS to bytecode and embeds it in the binary; ~2x startup on app-sized binaries (Bun docs benchmark). Requires `--compile`; top-level `await` must live inside `async` functions (it already does in this repo).
- **`minify`** — shrinks the binary and the bytecode it derives from.
- **`sourcemap: 'inline'`** — embeds the source map in the binary so error stack traces stay decodable. Bun also writes a residual `out/bin.js.map` next to the output; `compile.ts` removes it so the binary is the only artifact.

## ORPC

Contract → Router → Handler → Client, all type-safe from a single contract.

- `os` is built in `src/server/api/server.ts` via `implement(contract).$context<BaseContext>()`. **Always import `os` from `@/server/api/server`**, never from `@orpc/server` directly. `ORPCError`, `onError`, `ValidationError` come from `@orpc/server`.
- Contracts (`src/server/api/contracts/*.contract.ts`) generate Zod from Drizzle tables via `drizzle-zod`:
  ```ts
  const insertSchema = createInsertSchema(todoTable).omit(generatedFieldKeys)
  ```
  Barrel-aggregated in `contracts/index.ts` as `export const contract = { todo }`.
- Routers (`src/server/api/routers/*.router.ts`) import `db` directly from `@/server/db` in their handlers. There is **no `middlewares/` directory** by default — `db` doesn't need one (module-level const). When you actually need per-request context (auth, tenant, rate-limit), create `src/server/api/middlewares/<name>.middleware.ts` with `os.middleware(...)` and extend `BaseContext` in `context.ts`.
- **Interceptors are attached at the handler level, not in `server.ts` and not on `os`.** Both `src/routes/api/rpc.$.ts` (`RPCHandler`) and `src/routes/api/$.ts` (`OpenAPIHandler`) register `[onError(logError)]` (server) and `[onError(handleValidationError)]` (client). The validation interceptor rewrites `BAD_REQUEST + ValidationError` into `INPUT_VALIDATION_FAILED` (422) and output validation errors into `OUTPUT_VALIDATION_FAILED`. `logError` calls `logger.error` from `@/server/logger` — never `console.*` directly.
- OpenAPI/Scalar: docs at `/api/docs`, spec at `/api/spec.json` (handler prefix `/api`, plugin paths `/docs` and `/spec.json`).
- **SSR isomorphism** (`src/client/orpc.ts`): `createIsomorphicFn().server(createRouterClient(...)).client(new RPCLink(...))`. Server branch reads `getRequestHeaders()` for context; client branch POSTs to `${origin}/api/rpc`.
- **Mutation invalidation is colocated at the call site** via `mutationOptions({ onSuccess })`, not in `src/client/orpc.ts`. `orpc` in `src/client/orpc.ts` is a plain `createTanstackQueryUtils(client)` — no `experimental_defaults`. Per-feature query helpers live in `src/client/queries/<feature>.ts` (e.g. `useInvalidateTodos`); routes/components compose those hooks rather than holding query keys inline. See `src/client/queries/todo.ts` + `src/routes/index.tsx` for the canonical shape.
- SSR prefetch in route loaders: `await context.queryClient.ensureQueryData(orpc.todo.list.queryOptions())`. Components use `useSuspenseQuery(orpc.feature.list.queryOptions())`.

## Code style (Biome)

- 2-space, LF, single quotes, **semicolons as-needed** (omitted unless required), 120-col, arrow parens always, `useArrowFunction: "error"` (covers function *expressions* only). Also `noReactPropAssignments: "error"`.
- **Route components use `function Foo()` declarations**, placed below the `Route` config so the file reads top-down (route on top, component below). This is the official TanStack Router/Start pattern and relies on hoisting — `const Foo = () => {}` would TDZ-error when referenced from `createFileRoute({ component: Foo })` above it. Inline arrows are fine for trivial leaf components (e.g. plain redirect routes). Non-route components (UI primitives in `src/components/`) use `const Foo = () => {}`.
- Imports are auto-organized into two groups (external, then `@/*`), each alphabetical, with `import type` interleaved (NOT a separate group). `bun run fix` handles this; don't hand-sort.
- Files: utils `kebab-case.ts`, components `PascalCase.tsx`.
- `routeTree.gen.ts` is generated — ignored by Biome, never edit.

## Testing

`bun test` runs all `*.test.ts` files. Tests are colocated next to the source they exercise (e.g. `src/server/api/contracts/todo.contract.test.ts`). Use `import { describe, expect, test } from 'bun:test'`. The `@/*` alias resolves in tests via tsconfig paths. No Vitest, no Jest, no separate test config — keep it that way unless you need a browser/JSDOM environment.

## Endpoints

- `/` — Todos UI (file route).
- `/health` — bare `GET` returning `ok` (200, `text/plain`). Liveness only — no DB check, so it stays green even when Postgres is down. Add a separate `/ready` if you ever need readiness.
- `/api/rpc` — ORPC RPC handler (POST).
- `/api/*` — ORPC OpenAPI handler. Docs at `/api/docs`, spec at `/api/spec.json`.

## TypeScript

Strict mode, plus `noUncheckedIndexedAccess`, `verbatimModuleSyntax`, `erasableSyntaxOnly`, `noImplicitOverride`. No `as any` / `@ts-ignore` / `@ts-expect-error`.

Path alias: `@/* → src/*`. For files outside `src/` use `@/../<file>` (example in the codebase: `src/routes/api/$.ts` imports `name, version` from `@/../package.json`).

## Env

`src/env.ts` via `@t3-oss/env-core`. Server: `DATABASE_URL` (required, `z.url()`). `client: {}` is empty by default — any client-side env must be `VITE_`-prefixed. Never commit `.env`.

## Docker / deploy

- Multi-stage: `oven/bun:1.3.13` builds and runs `bun compile.ts`, then `gcr.io/distroless/cc-debian13:nonroot` runs the single `./server` binary. The `cc` (glibc) distroless variant is required because Bun's compiled binary links glibc.
- `compose.yaml`: one-shot `migrate` service runs `./server migrate` with `restart: "no"`, then `app` starts (`depends_on: migrate: service_completed_successfully`). `DATABASE_URL=postgres://postgres:postgres@db:5432/postgres` for both.
- Distroless has no shell, so any init-then-serve pattern must use exec-form `command: [...]`, not `sh -c`.

## Layout (non-obvious parts only)

```
src/
├── client/
│   ├── orpc.ts                 # isomorphic ORPC client + TanStack Query utils (no global invalidation defaults)
│   └── queries/                # per-feature query hooks: keys, options, `useInvalidate<Feature>` helpers
├── cli/                        # CLI subcommands (loaded lazily by bin.ts via citty)
│   ├── serve.ts                # `./server serve` — imports the Nitro bridge on demand
│   ├── migrate.ts              # `./server migrate` — drizzle migrate against ./drizzle
│   ├── _serve-nitro.mjs        # bridge: `import('../../.output/server/index.mjs')`
│   └── _serve-nitro.d.mts      # types for the bridge (build output has no .d.ts)
├── routes/
│   ├── __root.tsx              # root route + RootDocument shell
│   ├── index.tsx               # Todos UI
│   ├── health.ts               # GET /health → "ok" (no DB)
│   └── api/
│       ├── $.ts                # OpenAPI + Scalar; interceptors registered here
│       └── rpc.$.ts            # RPC; interceptors registered here
├── server/
│   ├── logger.ts               # the only log entrypoint — wrap before swapping to pino/otel
│   ├── api/
│   │   ├── server.ts           # the ONLY place to build `os`
│   │   ├── context.ts          # BaseContext (add per-request fields when you add middlewares)
│   │   ├── interceptors.ts     # logError (→ logger), handleValidationError
│   │   ├── types.ts            # Router{Client,Inputs,Outputs} derived from Contract
│   │   ├── contracts/          # Zod schemas from Drizzle tables (barrel: contract); colocated *.test.ts
│   │   └── routers/            # os.* handlers (barrel: router) — import db directly
│   ├── db/
│   │   ├── index.ts            # module-level `export const db = drizzle({...})`
│   │   ├── fields.ts           # generatedFields (id/createdAt/updatedAt) + generatedFieldKeys
│   │   ├── migrations.gen.ts   # AUTO-GENERATED by `bun run db:embed`; embeds ./drizzle/*.sql via `with { type: 'text' }`
│   │   └── schema/             # pgTable definitions; also put `relations()` here when adding
│   └── plugins/
│       └── shutdown.ts         # SIGINT/SIGTERM → db.$client.end() with 500ms delay (prod only)
├── components/                 # non-route UI primitives (PascalCase, arrow const)
├── env.ts                      # t3-oss env validation
├── router.tsx                  # QueryClient + setupRouterSsrQueryIntegration
├── styles.css                  # Tailwind v4 entry
└── routeTree.gen.ts            # auto-generated, do not edit
bin.ts                          # citty entry (root) — keep imports minimal (see "CLI" section)
compile.ts                      # `bun build --compile` driver; resolves --target; sets minify/bytecode/sourcemap
embed-migrations.ts             # codegen: scans ./drizzle/meta/_journal.json → src/server/db/migrations.gen.ts
drizzle/                        # SQL migrations (source of truth for `db:generate`; not shipped in binary)
```

Nitro plugins are wired in `vite.config.ts` (`nitro({ plugins: [...] })`), not via a Nitro config file.

## Don'ts (specific, non-obvious)

- Don't edit `routeTree.gen.ts` or `src/server/db/migrations.gen.ts`.
- Don't eager-import anything from `.output/` in `bin.ts` or any module it statically imports — it starts the HTTP server as a side effect. Subcommands must be lazy via citty's `() => import(...)` thunks.
- Don't re-add an auto-migrate Nitro plugin. Migrations are an explicit deploy step via `./server migrate`.
- Don't reach into `db.dialect`/`db.session` from `migrate.ts` — they're `@internal`. The current implementation uses public `db.execute(sql)` + `db.transaction(...)` against the documented `drizzle.__drizzle_migrations` schema.
- Don't add `./drizzle/` back to the runtime image — migrations are embedded into the binary.
- Don't reintroduce `getDB/closeDB` or any "lazy DB init" pattern — that's a Cloudflare Workers shape; we deploy on Bun processes.
- Don't import `os` from `@orpc/server` in middleware/routers — always `@/server/api/server`.
- Don't import from `drizzle-orm/zod` (1.0 beta only). Use `drizzle-zod`.
- Don't use RQB v2 object syntax, `defineRelations`, or pass `relations` to `drizzle()`. All are 1.0 beta.
- Don't use `drizzle-orm/bun-sql`.
- Don't use `@/*` aliases in `drizzle.config.ts`.
- Don't commit `.env`.

## Room-to-grow rules (discipline for the first real feature)

These keep the starter from setting bad precedents as it grows. Append, don't restructure.

1. Per-feature client query code — keys, options, `useInvalidate<Feature>` helpers — lives in `src/client/queries/<feature>.ts`. Routes/components compose these hooks; they don't hold query keys inline.
2. Mutation invalidation stays explicit at the mutation call site (`mutationOptions({ onSuccess })`) or in a feature query helper. Do not reintroduce global `experimental_defaults` or any implicit cache policy.
3. Client state defaults to route/component local state. Create a store (zustand or equivalent) only when state is shared across routes or needs persistence.
4. Middlewares (`src/server/api/middlewares/<name>.middleware.ts`) derive request-scoped context or gate access. They do NOT orchestrate business flow, hold side effects, or replace handlers/services.
5. Interceptors (`src/server/api/interceptors.ts`) do cross-cutting error logging, transport normalization, and validation rewrites. They do NOT read business data.
6. One file per Drizzle table. Relations live in the same file and are exported as `<entity>Relations`. No global `relations.ts`.
7. One router file per feature (`routers/<feature>.router.ts`). Only introduce `routers/<domain>/index.ts` when a domain grows past ~5 router files or needs shared domain helpers.
8. All server-side logging goes through `src/server/logger.ts`. Do not call `console.error/info/warn` directly from business code.
9. CLI subcommand modules keep top-level imports to `citty` + Node built-ins. Env, db, and server code are `await import(...)`-ed inside `run()` (see `bin.ts` comment for why).
10. Every new business feature ships with at least one `bun test` covering a contract schema, a pure helper, or a router behavior.