Bun.serve: HTTP/3 (QUIC) support via h3: true

packages/bun-types/serve.d.ts

@@ -757,6 +757,21 @@ declare module "bun" {
        */
       ipv6Only?: boolean;
 
+      /**
+       * Also listen for HTTP/3 (QUIC) on the same port. Requires {@link tls}.
+       *
+       * Not supported on Windows.
+       * @default false
+       */
+      h3?: boolean;
+
+      /**
+       * Listen for HTTP/1.1 (and HTTP/2) over TCP. Set to `false` together
+       * with `h3: true` to serve HTTP/3 only.
+       * @default true
+       */
+      h1?: boolean;
+
       /**
        * Sets the number of seconds to wait before timing out a connection
        * due to inactivity.

packages/bun-usockets/src/loop.c

@@ -665,13 +665,15 @@ void us_internal_dispatch_ready_poll(struct us_poll_t *p, int error, int eof, in
             }
 
             if (events & LIBUS_SOCKET_WRITABLE && !error && !u->closed) {
+                /* Clear WRITABLE before on_drain so a callback that re-arms it
+                 * (e.g. QUIC packets_out hitting EAGAIN) keeps the re-arm. We
+                 * still default to one-shot drain semantics for callers that
+                 * don't touch the poll mask. */
+                us_poll_change(&u->p, u->loop, us_poll_events(&u->p) & LIBUS_SOCKET_READABLE);
                 u->on_drain(u);
                 if (u->closed) {
                     break;
                 }
-                // We only poll for writable after a read has failed, and only send one drain notification.
-                // Otherwise we would receive a writable event on every tick of the event loop.
-                us_poll_change(&u->p, u->loop, us_poll_events(&u->p) & LIBUS_SOCKET_READABLE);
             }
 
 #if defined(__linux__)