Public dir

A publicdir serves files from disk verbatim — same name, same bytes, at the route you mount them on. You configure it per side (client or server), point source at a directory, and set outdir to where those files are copied at build time. In production it's also what serves your whole built client bundle at /.

// examples/basic/src/engine.ts — on the client side
publicdir: {
  source: [
    '../public', // every file under public/ → served at /
    {
      // virtual files: the function's return value is the file body
      '.well-known/appspecific/com.chrome.devtools.json': () => '{}',
      'robots.txt': () => 'User-agent: *\nDisallow: /',
    },
  ],
  outdir: '../dist/client',
},

With this, public/favicon.ico is served at /favicon.ico, and /robots.txt returns the inline string — no route, no point, no compiler involvement.

Naming: the key is publicdir (one lowercase word), not publicDir.

The simplest form

Most apps just point source at one directory and copy it into the client build:

publicdir: {
  source: '../public', // mounts public/ at /
  outdir: '../dist/client',
},

A bare string mounts that directory at /. Relative paths resolve against the engine's cwd.

Where it goes in the config

publicdir is a property of a side, not a top-level engine option. Both the server and each client (including entries in clients[]) take their own publicdir:

Engine.create({
  server: {
    /* ... */
    publicdir: { source: '../public-server', outdir: '../dist/server/public' },
  },
  client: {
    /* ... */
    publicdir: { source: '../public', outdir: '../dist/client' },
  },
})

The examples ship publicdir on the client side, since that's where the web assets live. The server side accepts the same shape, so use it when the server origin needs to serve its own static files.

source — what to serve

source accepts a string, an object map, an array, or any mix. A string is a directory mounted at /. An object maps route paths to directories or functions. An array combines both, plus [routePath, value] tuples:

source: [
  '../public', //                         directory → mounted at /
  { '/assets': '../other/dir/assets' }, // a directory elsewhere → mounted at /assets
  ['/static', '../shared/static'], //      tuple form, same effect
  { 'robots.txt': () => 'User-agent: *' }, // function → one virtual file
]

The value behind a route is one of two things:

• A directory path (string). Every file under it is walked recursively and mounted under the route prefix. { '/a': '../public-a' } serves ../public-a/one.txt at /a/one.txt.
• A function () => string | Promise<string>. It produces a single virtual file whose body is the return value, served at the function's route path. Sync or async both work:

source: {
  'robots.txt': () => 'User-agent: *\nDisallow: /',
  'config.json': async () => JSON.stringify(await loadConfig()),
}

Route paths are normalized: a leading slash is added, a trailing slash stripped, repeated slashes collapsed. So 'robots.txt' and '/robots.txt' resolve to the same /robots.txt.

Note — when a function file is re-invoked. In dev, where files are read live, a function entry is re-invoked per request and never cached — only real files (directory entries) hit the in-memory cache — so keep dev-time function bodies cheap. A build invokes each function once and writes its output as a real file into outdir (see below); in production that file is indexed, served, and cached like any other, and the function never runs per request.

Gotcha — a typo'd source path fails silently. A missing or permission-denied source directory yields zero files with no warning — the route just 404s. Double-check relative paths.

outdir — required, or nothing serves

publicdir: {
  source: '../public',
  outdir: '../dist/client', // copy target at build time
},

outdir is the directory the publicdir's files are copied into at build time. In every example it equals the client build outdir, so static files land next to the JS bundle.

Gotcha — no outdir, no publicdir. If you omit outdir, the whole publicdir resolves to null and nothing is served, even with a valid source — silently, with no default. If your static files 404, check that outdir is set.

At build time, directory entries are copied file-by-file into outdir, and function entries are invoked and their output written as real files — so () => '{}' becomes an actual .json file in dist. When the client JS build and the publicdir build write to the same directory, the JS build wins (dist files override publicdir files on a name clash).

cacheLimit — the in-memory cache

Served real files are cached in memory keyed by absolute path (an LRU); each entry holds the file's bytes and content type. cacheLimit bounds it:

publicdir: {
  source: '../public',
  outdir: '../dist/client',
  cacheLimit: 64 * 1024 * 1024, // 64 MB; or `false`/`0` to disable; `true`/omit = auto
},

A single file larger than the whole limit is never cached. The cache clears whenever the file index is rebuilt.

Gotcha — auto can hold up to 512 MB. On a host with lots of RAM and a big static dir, the auto limit (5% of RAM) climbs toward its 512 MB cap. Set an explicit number, or false, to bound memory.

Note: the publicdir cache is an in-memory server cache only. The responses themselves carry no HTTP cache headers (Cache-Control / ETag / max-age).

For browser/CDN caching, mount the cacheControl() middleware on your root. It leans on the engine's own classification of static files: a served file whose name carries a content hash (a build chunk, /_point0/assets/*) is the asset request variant and caches forever; a stable-name file is publicdir and gets a short revalidate. Both values are configurable per variant:

.middleware(cacheControl({ publicdir: 'public, max-age=86400' }))

How it differs from imported assets

Static files reach the browser two ways:

// 1. Imported asset — compiler-managed, content-hashed
import logo from './logo.png'
// → served at /_point0/assets/<hash>.png, filename hashed

// 2. publicdir file — served verbatim, original name
// public/logo.png → served at /logo.png

Imported assets go through the compiler: the URL is content-addressed (/_point0/assets/<hash>.png), so the browser can cache them forever. A publicdir file is served as-is at the route you declared, with its original name — no hashing, no compiler.

In production they converge. The compiler writes hashed asset bytes into dist/client/_point0/assets/…, and after a build the canonical publicdir: { source: '../public', outdir: '../dist/client' } serves all of dist/client at /. That one config serves your public/ files and the compiler-emitted hashed assets — both live in dist/client. See assets for the asset pipeline.

Practically: put files you reference by a fixed, predictable URL (favicon, robots.txt, manifest, .well-known/…) in publicdir. Let import handle anything you reference from code and want cache-busted.

Serving semantics

A publicdir matches before pages and endpoints, and only for GET, HEAD, and OPTIONS:

// request flow for GET /foo:
//   1. each publicdir is checked in order (server publicdir first, then client
//      publicdirs in clients[] order) — first match wins, served as a file
//   2. only if none match → pages / endpoints

Gotcha — a static file wins a route collision. If a publicdir file and a page share a path, a GET/HEAD/OPTIONS request gets the file, not the page. POST and other methods fall through to endpoints.

The matched response is exposed to your code as the 'publicdir' request variant.

The file index is lazy — the directory walk happens on the first matching request, not at startup, so a publicdir never blocks the server from coming up. The engine also warms the index in the background, and you can force it eagerly with engine.preparePublicdirs().

When two publicdirs (e.g. server + client) claim the same route, the first in that order wins. There is no cross-publicdir conflict validation — the collision is silent, and the first match simply serves.

Content type

Content type is inferred from the file. For real files it comes from Bun's file detection; for function files it's inferred from the route's extension (.json → application/json, .css → text/css, …).

Client publicdir and serving

A server publicdir always serves. A client publicdir inherits the client's serving option (default true):

client: {
  serving: 'app.example.com', // this client's publicdir only serves on this host
  publicdir: { source: '../public', outdir: '../dist/client' },
}

serving is true (always) / false (never) / a host string (serve only when request.location.host matches exactly) / a function (decide per request). In a multi-client app, each client's publicdir is gated by its own serving.

Production serving

There is no point0 start command. You start production by running the built server directly:

// examples/basic/package.json
"start": "cross-env NODE_ENV=production bun run ./dist/server/index.server.js"

When the engine config is re-imported after a build, the publicdir source is rewritten to serve the built outdir itself — effectively [['/', dist/client]]. That's the mechanism behind "the built server serves dist/client at /": your public/ files, the hashed assets, and the JS bundle all sit in dist/client and are served from there. This auto-rewrite is on by default and controlled by the engine's autoFixBuiltPaths option.

The built server can serve dist/client directly, or sit behind a CDN or reverse proxy — point0 prescribes no host-specific config either way. The publicdir responses carry no HTTP cache headers, so if you front them with a CDN, set caching there or attach headers in a middleware (see the cacheLimit section). See Deploy for the production run-and-serve story.

The --no-publicdir build flag

One CLI flag touches the publicdir, on build:

point0 build                  # builds JS and copies public files into outdir
point0 build --no-publicdir   # builds JS only — skips the publicdir copy
point0 build -P               # short form of --no-publicdir

Use --no-publicdir when your static files are managed separately or haven't changed. There is no equivalent flag for dev — dev always serves the publicdir live (files are read on the fly, never copied).

Reference

Config shape

publicdir lives on server and on each client:

publicdir?: {
  source: EngineOptionsPublicdir // string | object map | array (mix)
  outdir: string //                required — copy target; omit it ⇒ nothing serves
  cacheLimit?: number | boolean // bytes; false/0 off; true/omit = auto (32–512 MB)
}

source forms

A directory value is walked recursively; a function value (() => string \| Promise<string>) is one virtual file, re-run per request.

Behavior at a glance

Related engine methods

• engine.preparePublicdirs() — eager-load every publicdir's file index (otherwise lazy on first request).
• engine.build({ publicdir: false }) — the programmatic equivalent of --no-publicdir.
• engine.clean() — clean every outdir (each side's outdir and its publicdir, plus the server outdir). It takes no arguments; there is no engine.clean({ publicdir }) overload. The publicdir-only clean is the internal publicdir.clean() on a Publicdir instance, not an engine method.

Binary files

The build-time copy is binary-safe. Directory entries are copied with Bun.write(dest, Bun.file(src)) — a native byte-for-byte copy, never a UTF-8 .text() round-trip — so images, fonts, and other binaries land in outdir intact regardless of where outdir points.

Range requests and large files

With caching on (the default) a real file is read into memory on its first request (file.arrayBuffer()), cached, and served from that ArrayBuffer; later requests hit the cache. With caching off the file is streamed as new Response(Bun.file(...)), where Bun handles range requests natively.