[miniflare] Fix requests failing after 5 minutes due to undici Pool default timeouts

.changeset/miniflare-disable-pool-timeouts.md

@@ -0,0 +1,9 @@
+---
+"miniflare": patch
+---
+
+fix: disable undici Pool request timeouts for local dev
+
+Miniflare's undici `Pool` instances were using the default `headersTimeout` and `bodyTimeout` of 300 seconds (5 minutes). Any request taking longer than that — streaming responses, large uploads, long-polling, or compute-heavy Workers — would be silently killed with a "request failed" error.
+
+Setting both timeouts to `0` disables them entirely, which is the correct behaviour for a local development tool where there is no reason to enforce request timeouts.

packages/miniflare/src/index.ts

@@ -2143,6 +2143,10 @@ export class Miniflare {
 		if (previousEntryURL?.toString() !== this.#runtimeEntryURL.toString()) {
 			this.#runtimeDispatcher = new Pool(this.#runtimeEntryURL, {
 				connect: { rejectUnauthorized: false },
+				// Disable timeouts for local dev — long-running responses (streaming,
+				// slow uploads, long-polling) should not be killed by undici defaults.
+				headersTimeout: 0,
+				bodyTimeout: 0,
 			});
 		}
 		if (this.#proxyClient === undefined) {

packages/miniflare/src/plugins/core/proxy/fetch-sync.ts

@@ -54,6 +54,10 @@ port.addEventListener("message", async (event) => {
     dispatcherUrl = url;
     dispatcher = new Pool(url, {
       connect: { rejectUnauthorized: false },
+      // Disable timeouts for local dev — long-running responses (streaming,
+      // slow uploads, long-polling) should not be killed by undici defaults.
+      headersTimeout: 0,
+      bodyTimeout: 0,
     });
   }
   headers["${CoreHeaders.OP_SYNC}"] = "true";