fetch

Global fetch makes requests from the cloud runtime. Use it to call public APIs, upload data, and stream responses without importing a module. For services on a client's own machine or private network, use host.fetch in lexmount:remote.

const response = await fetch('https://example.com');
if (!response.ok) throw new Error(`HTTP ${response.status}`);
console.log(await response.text());

fetch(input, init?)

Function: sends a request and returns a response once its headers arrive. Reading the body is a separate asynchronous operation.

declare function fetch(input: string | URL | Request, init?: RequestInit): Promise<Response>;

Return value: Promise<Response>. HTTP 4xx / 5xx responses resolve normally; inspect ok or status. Network, DNS, TLS, or destination validation failures reject the promise. Invalid methods and already-used bodies can also cause TypeError.

For FormData, let the runtime generate a Content-Type containing its boundary. For JSON, use JSON.stringify() and set the appropriate header. Upload ReadableStreams must yield byte chunks.

These RequestInit fields are also accepted, but currently only retained on the request object. They do not implement the corresponding browser cache, cookie, CORS, or integrity facilities:

Network scope and request options

HTTP(S) requests allow public destinations only. DNS results and every redirect target are checked. Loopback, private, and other non-public addresses are rejected. data: and blob: URLs can read inline data or objects in the current environment without HTTP networking.

Server-side requests have no page-relative URL base, browser login Cookie Jar, or browser HTTP cache. Browser-side options such as credentials, mode, and cache do not establish those facilities. Set authentication headers explicitly. Host proxies and certificate trust are managed by the platform; application environment variables cannot reconfigure the request client.

Response

The response returned by fetch() exposes these properties:

Body methods

These methods take no arguments. Except for clone(), each consumes the whole body and returns a promise. A body can be consumed only once.

For streaming reads, use response.body.getReader() and release the reader lock afterward. If you do not need the body, call await response.body?.cancel(); cancel through the reader if it holds the lock. Full-body reads require corresponding memory. Consume or cancel both branches of a clone as well.

Cancellation and timeouts

fetch() has no timeoutMs option. Pass AbortSignal.timeout(milliseconds) or call AbortController.abort(reason?). Cancellation affects the request and its response body, rejecting the promise or a pending read.

const response = await fetch('https://example.com', {
  signal: AbortSignal.timeout(10000),
});
console.log(await response.text());

A timeout signal normally rejects with TimeoutError; a controller without a custom reason uses AbortError. Handle a supplied reason as that value. Task stop or expiry also cleans up network resources. Cancellation cannot undo an operation already performed by the destination service.

For serving HTTP with a default export, see the public HTTP example.