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remix

Build and review Remix 3 applications using the `remix` npm package and subpath imports. Use when working on Remix app structure, routes, controllers, middleware, validation, data access, auth, sessions, file uploads, server setup, UI components, hydration, navigation, or tests.

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---name: remixdescription:  Build and review Remix 3 applications using the `remix` npm package and  subpath imports. Use when working on Remix app structure, routes, controllers,  middleware, validation, data access, auth, sessions, file uploads, server  setup, UI components, hydration, navigation, or tests.--- # Build a Remix App Use this skill for end-to-end Remix app work. It should help the agent choosethe right layer first, reach for the right package, and avoid the most commonRemix-specific mistakes. ## What Remix Is Remix 3 is a server-first web framework built on Web APIs such as `Request`,`Response`, `URL`, and `FormData`. All packages ship from a single npm package,`remix`, and are imported via subpath. There is no top-level `remix` import. A Remix app has four main pieces: - **Routes** in `app/routes.ts` define the typed URL contract and power `href()`  generation.- **Controllers and actions** implement that contract and return `Response`  objects.- **Middleware** composes request lifecycle behavior and populates typed context  via `context.set(Key, value)`.- **Components** render UI with `remix/ui`. This is not React. A component  receives a `handle`, reads current props from `handle.props`, and returns a  render function. ## When To Use This Skill Use this skill for: - new features or refactors that touch routing, controllers, middleware, data,  auth, sessions, UI, or tests- reviewing Remix app code for correctness, architecture, or framework usage- answering "how should this be structured in Remix?" questions- finding the right package, reference doc, or default pattern for a task ## Load Only The References You Need Classify the task first, then load the smallest useful reference set. Eachreference file starts with a "What This Covers" section that lists the topicsinside it — read that first to confirm the file is relevant before reading therest. Use the table below to find candidates. Loading more than two or three files atonce is usually a sign that the task hasn't been narrowed enough yet. | Task involves...                                                              | Start with                                  || ----------------------------------------------------------------------------- | ------------------------------------------- || Defining URLs, writing controllers and actions, returning responses           | `references/routing-and-controllers.md`     || Composing the request lifecycle, ordering middleware, bridging to a server    | `references/middleware-and-server.md`       || Compiling and serving browser modules, asset URL namespaces, preloads         | `references/assets-and-browser-modules.md`  || Parsing input, validating with schemas, defining tables, querying, migrations | `references/data-and-validation.md`         || Per-browser state, login flows, route protection, identity                    | `references/auth-and-sessions.md`           || Component setup, state, lifecycle, updates, `queueTask`, context              | `references/component-model.md`             || Event handlers, styles, refs, click/key behavior, simple animations           | `references/mixins-styling-events.md`       || `clientEntry`, `run`, `<Frame>`, navigation, `<head>`                         | `references/hydration-frames-navigation.md` || Router tests, component tests, test isolation                                 | `references/testing-patterns.md`            || Spring physics, tweens, layout transitions                                    | `references/animate-elements.md`            || Authoring custom reusable mixins                                              | `references/create-mixins.md`               | Common bundles: - **Form or CRUD feature** -> routing, data and validation, testing; add auth if  user-specific- **Protected area** -> auth and sessions, routing, testing- **Interactive widget** -> component model, mixins and styling; add hydration  only if it runs in the browser- **Browser asset pipeline** -> assets and browser modules, hydration,  middleware and server- **File upload** -> middleware and server, data and validation, testing- **Navigation or frames** -> hydration, frames, navigation ## Default Workflow 1. **Classify the change.** Decide whether it changes the route contract,   request lifecycle, data model, auth or session behavior, or only UI.2. **Start from the server contract.** Add or update `app/routes.ts` before   wiring handlers or UI.3. **Put code in the narrowest owner.** Favor route-local code first, then   promote only when reuse is real.4. **Make the server path correct before adding browser behavior.** A route   should return the right `Response` via `router.fetch(...)` before you add   `clientEntry(...)`, animations, or DOM effects.5. **Add middleware deliberately.** Keep fast-exit middleware early and   request-enriching middleware later. Export a typed `AppContext` from the root   middleware stack and use it in controllers.6. **Validate input at the boundary.** Parse and validate `Request`, `FormData`,   params, cookies, and external payloads before they reach rendering or   persistence logic.7. **Hydrate only when necessary.** Prefer server-rendered UI. Use   `clientEntry(...)` and `run(...)` only for real browser interactivity or   browser-only APIs.8. **Test the narrowest meaningful layer.** Prefer router tests for route   behavior. Use component tests when the behavior is truly interactive or   DOM-specific.9. **Finish with verification.** Re-read the route flow, confirm auth and   authorization boundaries, and run the smallest relevant test and typecheck   loop. ## Project Layout Use these root directories consistently: - `app/` for runtime application code- `db/` for migrations and local database files- `public/` for static assets served as-is- `test/` for shared helpers, fixtures, and integration coverage- `tmp/` for uploads, caches, local session files, and other scratch data Inside `app/`, organize by responsibility: - `assets/` for client entrypoints and client-owned browser behavior- `controllers/` for route-owned handlers and route-local UI- `data/` for schema, queries, persistence setup, migrations, and runtime data  initialization- `middleware/` for request lifecycle concerns such as auth, sessions, uploads,  and database injection- `ui/` for shared cross-route UI primitives- `utils/` only for genuinely cross-layer helpers that do not clearly belong  elsewhere- `routes.ts` for the route contract- `router.ts` for router setup and wiring ### Placement Precedence When code could live in multiple places: 1. Put it in the narrowest owner first.2. If it belongs to one route, keep it with that route.3. If it is shared UI across route areas, move it to `app/ui/`.4. If it is request lifecycle setup, keep it in `app/middleware/`.5. If it is schema, query, persistence, or startup data logic, keep it in   `app/data/`.6. Use `app/utils/` only as a last resort for truly cross-layer helpers. ### Route Ownership - Use a flat file in `app/controllers/` for a simple leaf action, such as  `app/controllers/home.tsx`- Use a folder with `controller.tsx` when a route owns nested routes or multiple  actions, such as `app/controllers/account/controller.tsx`- Mirror nested route structure on disk, such as  `app/controllers/auth/login/controller.tsx`- Keep route-local UI next to its owner, such as  `app/controllers/contact/page.tsx`- Move shared UI to `app/ui/`- If a flat leaf grows child routes or multiple actions, promote it to a  controller folder ### Layout Anti-Patterns - Do not create `app/lib/` as a generic dumping ground- Do not create `app/components/` as a second shared UI bucket when `app/ui/`  already owns that role- Do not put shared cross-route UI in `app/controllers/`- Do not put middleware or persistence helpers in `app/utils/` when they have a  clearer home- Do not create folders for simple leaf actions unless they are real controllers ## Core Remix Rules - Import from `remix/<subpath>`, never `import { ... } from 'remix'`- Treat `app/routes.ts` as the source of truth for URLs. Use  `routes.<name>.href(...)` for redirects, links, tests, and internal URL  construction- Controllers and actions should return explicit `Response` objects, including  redirects, 404s, and validation failures. At the route boundary, prefer  returning a `Response` for expected outcomes (validation errors, conflicts,  not found) over throwing for control flow- Model HTTP behavior explicitly. Status codes, headers, redirects, cache rules,  and content types are part of the route contract- Make the server route correct first. A POST should already return the right  HTML, redirect, or error response on its own before `clientEntry(...)` layers  interactivity on top- Validate input at the boundary using `remix/data-schema` (and  `remix/data-schema/form-data` for forms). `parseSafe` makes the failure path a  return value instead of an exception- Derive `AppContext` from the root middleware stack so `get(Database)`,  `get(Session)`, `get(Auth)`, and similar keys stay typed. If the controller  never reads from context, it doesn't need the harness- Outside actions and controllers, only use `getContext()` when `asyncContext()`  is in the middleware stack- Remix Component is not React: read props from `handle.props`, keep state in  setup-scope variables, call `handle.update()` explicitly, and do DOM-sensitive  work in event handlers or `queueTask(...)`, not in render- Prefer host-element mixins via `mix={mixin(...)}` for behavior and styling  instead of inventing custom host prop conventions. Use `mix={[...]}` only when  composing multiple mixins- Hydrated `clientEntry(...)` props must be serializable. Do not pass functions,  class instances, or opaque runtime objects ## Security And Session Defaults - Never ship demo secrets. In non-test environments, require session and  provider secrets from the environment and fail fast if they are missing- Use hardened cookies: `httpOnly` always, `sameSite` by default, and `secure`  when serving over HTTPS- Regenerate session IDs on login, logout, and privilege changes- Use `requireAuth()` to protect authenticated route areas, but still authorize  resource ownership inside handlers and data writes- Add CSRF protection when browser forms mutate state using cookie-backed  sessions- Add CORS only for endpoints that must be called cross-origin. Prefer  same-origin by default- Prefer JSX or `remix/html-template` for HTML generation so escaping stays  correct- Validate uploads for size, type, and destination. Treat filenames and content  as untrusted input ## Testing Defaults - Prefer server and router tests first. Drive the app with  `router.fetch(new Request(...))` and assert on the returned `Response`- Build a fresh router per test or per suite so sessions, in-memory storage, and  database state stay isolated- Use `routes.<name>.href(...)` in tests so URLs stay coupled to the route  contract- For auth or session scenarios, use a test cookie and  `createMemorySessionStorage()` instead of production storage- Use component tests only for interactive or DOM-specific behavior. Render with  `createRoot(...)`, interact with the real DOM, and call `root.flush()` between  steps- Prefer one representative behavior test over many repetitive assertion  variants ## Common Mistakes To Avoid - Treating Remix Component like React and reaching for hooks or implicit  rerendering- Importing from a top-level `remix` entry instead of a subpath- Adding `clientEntry(...)` before the server-rendered route behavior is correct- Passing non-serializable props into `clientEntry(...)`- Calling `getContext()` without `asyncContext()` in the middleware stack- Getting middleware order wrong; fast exits like static files belong early,  request enrichment later- Skipping boundary validation and trusting raw `FormData`, params, cookies, or  external payloads- Letting route-local domain errors leak out of the controller. Translate  expected outcomes (validation, conflicts, not-found) into the HTTP `Response`  the route means to return rather than throwing a custom `Error` subclass and  catching it elsewhere- Reaching for `createCookie` when a tamper-sensitive or server-managed  per-browser fact really wants `remix/session`. If editing the value would be a  bug, use a session- Building a JSON-only RPC layer when a normal form POST, redirect, or resource  route would be simpler. Fetch-from-the-client is a layer on top of sound route  behavior, not a replacement for it- Treating JSON state endpoints and `<Frame>` reloads as mutually exclusive  patterns. Pick the lightest sync mechanism that fits the UX; small widgets may  reasonably poll a JSON endpoint- Assuming authentication is enough without per-resource authorization checks- Dropping shared code into vague buckets like `utils.ts`, `helpers.ts`, or  `common.ts` when ownership is known- Writing only component tests for a feature whose main behavior is really an  HTTP route concern ## Package Map Use this map to find the right package quickly. Each entry says what the packageis for, not just what it exports. Open the linked reference file when you needfull examples. ### Routing, Server, and Responses - `remix/router` — the router itself. Use for `createRouter`, controller and  middleware types, and registering routes. A URL that matches a route pattern  but not the request method gets `405 Method Not Allowed` with an `Allow`  header (it does not reach `defaultHandler`); register an `ANY` route for a  per-URL catch-all. `GET` routes also serve `HEAD` with the same status and  headers and an empty body — do not add explicit `HEAD` routes just for that- `remix/routes` — declarative route builders. Use for `route`, `get`, `post`,  `put`, `del`, `form`, `resources` when defining `app/routes.ts`- `remix/node-fetch-server` — adapter from Node's `http` module to a Fetch-style  router. Use for `createRequestListener` in `server.ts`- `remix/assets` — browser asset server. Use for `createAssetServer` when  serving compiled scripts and styles. Scripts resolve imports through import  maps: read `getScriptEntry()` and render `<ImportMap value={importMap} />`  (from `remix/ui/server`) before the preloads and module script; use  `fingerprint: true` (content hashes) plus `files.cacheKey` for persistent  caches, and directory `mounts` (default `{ app, npm }`). Shared compiler  options such as `target`, `sourceMaps`, `sourceMapSourcePaths`, and `minify`  live at the top level. Kody's origin website does not use this: hydration URLs  come from Pitlane `?assets=`- `remix/multiple-import-maps-polyfill` — `importModule()`,  `detectMultipleImportMapSupport()`, `preloadShim()` for browsers without  native multiple-import-map support. Only relevant with `remix/assets`- `remix/middleware/render` — pairs `createAssetServer` with frame rendering for  Node apps. Do not use it on the origin Worker; Kody owns `renderToStream` plus  Workers Assets- `remix/spa` — client-only `run(router)` for apps with no server document. Kody  keeps a custom client router on top of server-rendered HTML: it runs the  destination's loader before committing the URL, and route components read the  payload through `createRouteData` (`#client/route-data.tsx`) so the previous  page stays until the next one is ready — see  `docs/contributing/no-flash-navigation.md` before adding a client route- `remix/headers` — typed header parsers and builders. Use when reading  `Accept`, `Cookie`, or setting `CacheControl`, `Vary`, etc., instead of  hand-formatting strings- `remix/response/redirect` — `redirect(href, status?)`. Use for the canonical  "POST then redirect" pattern and other location changes- `remix/response/html` — `createHtmlResponse`. Use when you need an HTML  `Response` from a string or stream without rendering through `remix/ui`- `remix/response/compress` — `compressResponse`. Use when compressing one-off  responses outside the global `compression()` middleware- `remix/response/file` — file-download responses. Use for  `Content-Disposition: attachment` responses- `remix/route-pattern` — low-level URL matching and generation. Use when  working with raw patterns outside the router (custom matchers, scripts)- `remix/fetch-proxy` — Fetch-based HTTP proxying. Use to forward a request to  another origin; pass `xForwardedHeaders` when the upstream needs forwarded  proto, host, and port ### Data, Validation, and Persistence - `remix/data-schema` — schema builders for runtime validation. Use for `parse`  and `parseSafe` to validate any input that crosses a trust boundary, and  `.transform(...)` when validated output should map to a different value or  type- `remix/data-schema/checks` — common check helpers (`email`, `minLength`,  `maxLength`, etc.). Use to compose into a schema- `remix/data-schema/coerce` — coercion helpers for strings, numbers, booleans,  dates, and ids. Use when input arrives as a string but should be a typed value- `remix/data-schema/form-data` — `f.object` and `f.field` for parsing  `FormData` directly. Use in actions that read browser forms- `remix/data-table` — typed tables and a `Database` interface. Use for `table`,  `column`, and `new Database(driver)` when modeling persisted data- `remix/data-table/sqlite`, `remix/data-table/postgres`,  `remix/data-table/mysql` — official drivers. Use `createSqliteDatabase(...)`  for Node, Bun, and compatible synchronous SQLite clients. Remix does not ship  a D1 factory; Kody owns `D1DatabaseDriver` and passes it to `new Database`- `remix/data-table/migrations` — migration authoring and runners. Use for  `createMigration`, `createMigrationRunner`- `remix/data-table/migrations/node` — `loadMigrations` from disk. Use in  startup scripts that apply migrations- `remix/data-table/operators` — query operators such as `inList(...)`. Use when  `where` clauses need set or comparison logic ### Auth, Sessions, and Cookies - `remix/session` — the `Session` object: `get`, `set`, `flash`, `unset`,  `regenerateId`. Use for any per-browser state where tampering would be a bug  (login, "I submitted this form already", cart, flash messages)- `remix/middleware/session` — `session(cookie, storage)`. Use to wire a session  cookie and storage backend into the root middleware stack- `remix/session-storage/fs`, `remix/session-storage/memory`,  `remix/session-storage/cookie` — storage backends. Use `fs-storage` for  single-process apps, `memory-storage` for tests, `cookie-storage` for  stateless deployments where data fits in a cookie- `remix/session-storage/redis` — Redis-backed storage. Use for multi-process or  multi-host deployments- `remix/session-storage/memcache` — Memcache-backed storage. Same multi-host  use case as Redis- `remix/cookie` — `createCookie` for plain signed/unsigned cookies. Use for  non-sensitive preferences where the client is allowed to control the value  (theme, locale, dismissed banner). For state where tampering matters, prefer  `remix/session`- `remix/auth` — credentials, OAuth, and OIDC providers. Use to define how  identity is verified, start/finish external login, and refresh stored  OAuth/OIDC token bundles with `refreshExternalAuth(...)`. Use `OAuthTokens`.  There is no built-in Atmosphere/atproto provider.- `remix/middleware/auth` — `auth({ schemes })`, `requireAuth`, the `Auth`  context key. Use to resolve identity into the request context and to gate  routes ### UI, Hydration, and Browser Behavior - `remix/ui` — the component runtime: components, core mixins, `clientEntry`,  `run`, `<Frame>`, navigation helpers, and `createRoot`. Use for app UI  behavior. Framework attributes are `data-rmx-*` (`data-rmx-target`,  `data-rmx-document`, `data-rmx-history`, …). Listen with native  `target.addEventListener(type, listener, { signal })`; there is no  `addEventListeners()` helper. Server-rendered `<script>` elements must have a  single string child (or stay empty with `src`); non-string children render  empty and error. `handle.update()` during setup warns and is skipped — move it  to an event handler or `handle.queueTask()`. Optional `run({ resolveFrame })`  defaults to fetching the frame source as HTML and rendering `3xx`/`4xx` HTML  responses in the frame; Kody keeps a custom resolver for the frame registry,  prefetch cache, and retries but mirrors that status acceptance. `run()` falls  back to document navigation when the Navigation API is missing, so no  `window.navigation` stub is needed.- `remix/ui/server` — server rendering: `renderToStream`, `renderToString`. Use  in the `render(...)` helper that returns HTML responses- `remix/ui/animation` — animation APIs: `animateEntrance`, `animateExit`,  `animateLayout`, `spring`, `tween`, and `easings`- `remix/ui/<primitive>` — UI primitives, mixins, glyphs, and theme helpers.  Import from `remix/ui/accordion`, `remix/ui/button`, `remix/ui/select`, etc.- `remix/ui/test` — component test rendering helpers such as `render`- `remix/ui/jsx-runtime` — JSX transform target. Configured in `tsconfig.json`,  rarely imported directly- `remix/html-template` — escaped HTML template literals. Use when generating  HTML outside the component system (RSS feeds, email bodies, error pages)- `remix/file-storage` — backend-agnostic `File` storage interface. Use as the  type bound for upload destinations- `remix/file-storage/fs`, `remix/file-storage/memory`, `remix/file-storage-s3`  — storage backends. Use to implement an upload destination ### Middleware - `remix/middleware/static` — `staticFiles(dir)`. Use to serve files from  `public/` exactly as they exist on disk- `remix/middleware/form-data` — `formData()`. Use to parse `FormData` once and  expose it via `get(FormData)` instead of calling `await request.formData()` in  each action- `remix/form-data-parser` — lower-level `parseFormData`, `FileUpload`. Use when  implementing custom upload handlers. Upload handler errors propagate directly- `remix/multipart-parser` and `remix/multipart-parser/node` — low-level  multipart stream parsing. `MultipartPart.headers` is a plain object keyed by  lower-case header name; read values with bracket notation such as  `part.headers['content-type']`- `remix/middleware/compression` — `compression()`. Use globally for text-like  responses- `remix/middleware/logger` — `logger()`. Use in development for request logs;  pass `colors` to force terminal color output on or off- `remix/middleware/method-override` — `methodOverride()`. Use when HTML forms  need `PUT`, `PATCH`, or `DELETE`- `remix/middleware/async-context` — `asyncContext()`, `getContext()`. Use when  helpers outside actions need request context without threading it through  every call- `remix/middleware/cors` — `cors(opts?)`. Use for endpoints called cross-origin- `remix/middleware/csrf` — `csrf(opts?)`. Use when session-backed forms mutate  state and need synchronizer-token CSRF protection- `remix/middleware/cop` — cross-origin protection. Use to reject unsafe  cross-origin browser requests ### Test - `remix/test` — `describe`, `it`, and lifecycle hooks. Use as the test  framework- `remix/test/cli` — programmatic test runner APIs such as `runRemixTest`- `remix/cli` — programmatic Remix CLI API. Use the `remix` executable for  project commands such as `remix test`, `remix routes`, and `remix doctor`- `remix/assert` — assertion helpers. Use in place of `node:assert` so messages  render cleanly in the runner- `remix/terminal` — ANSI styles, color detection, style factories, and testable  terminal streams. Use for CLIs and terminal output instead of hand-rolled  escape sequences ## Canonical Patterns ### Define routes first ```typescriptimport { form, get, post, resources, route } from 'remix/routes' export const routes = route({	home: '/',	contact: form('contact'),	books: {		index: '/books',		show: '/books/:slug',	},	auth: route('auth', {		login: form('login'),		logout: post('logout'),	}),	admin: route('admin', {		index: get('/'),		books: resources('books', { param: 'bookId' }),	}),})``` ### Type controllers against the route contract ```typescriptimport type { Controller } from 'remix/router' import type { AppContext } from '../router.ts'import { routes } from '../routes.ts' export default {  actions: {    async index({ get }) {      let db = get(Database)      let allBooks = await db.findMany(books, { orderBy: ['id', 'asc'] })      return render(<BooksIndexPage allBooks={allBooks} />)    },    async show({ get, params }) {      let db = get(Database)      let book = await db.findOne(books, { where: { slug: params.slug } })      if (!book) return new Response('Not Found', { status: 404 })      return render(<BookShowPage book={book} />)    },  },} satisfies Controller<typeof routes.books, AppContext>``` ### Compose middleware deliberately ```typescriptimport {	createRouter,	type AnyParams,	type MiddlewareContext,	type WithParams,} from 'remix/router' export type RootMiddleware = [	ReturnType<typeof formData>,	ReturnType<typeof session>,	ReturnType<typeof loadDatabase>,	ReturnType<typeof loadAuth>,] export type AppContext<params extends AnyParams = AnyParams> = WithParams<	MiddlewareContext<RootMiddleware>,	params> let middleware = [] if (process.env.NODE_ENV === 'development') {	middleware.push(logger())} middleware.push(compression())middleware.push(staticFiles('./public'))middleware.push(formData())middleware.push(methodOverride())middleware.push(session(cookie, storage))middleware.push(asyncContext())middleware.push(loadDatabase())middleware.push(loadAuth()) let router = createRouter({ middleware })``` ### Mutate, validate, and respond ```typescriptimport { redirect } from 'remix/response/redirect'import * as s from 'remix/data-schema'import * as f from 'remix/data-schema/form-data'import { Session } from 'remix/session'import { Database } from 'remix/data-table' let bookSchema = f.object({  slug: f.field(s.string()),  title: f.field(s.string()),}) export default {  actions: {    async create({ get }) {      let parsed = s.parseSafe(bookSchema, get(FormData))      if (!parsed.success) {        return render(<NewBookPage errors={parsed.issues} />, { status: 400 })      }       let db = get(Database)      let book = await db.create(books, parsed.value)       let session = get(Session)      session.flash('message', `Added ${book.title}.`)       return redirect(routes.books.show.href({ slug: book.slug }))    },  },} satisfies Controller<typeof routes.books, AppContext>``` This shape works without JavaScript, returns a `Response` for every outcome, andis ready for `clientEntry(...)` interactivity when the UI needs it. ### Build UI from handle props plus render ```tsximport { on, type Handle } from 'remix/ui' function Counter(handle: Handle<{ initialCount?: number; label: string }>) {	let count = handle.props.initialCount ?? 0 	return () => (		<button			mix={on('click', () => {				count++				handle.update()			})}		>			{handle.props.label}: {count}		</button>	)}``` Only add `clientEntry(...)` and `run(...)` when the component needs browserinteractivity or browser-only APIs.
Referenced from AGENTS.md

These references come from AGENTS.md at the skill snapshot.

AGENTS.md · same revision ↗
Source excerpt starting at line 43.
  - [docs/contributing/remix.md](./docs/contributing/remix.md) and the    repo-local [Remix skill](./.agents/skills/remix/SKILL.md)  - [docs/contributing/no-flash-navigation.md](./docs/contributing/no-flash-navigation.md)
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