Fix race condition in bearer-rejection retry that caused "link chain completed without emitting a value"#11754
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…k chain completed without emitting a value" When the server sends X-Bearer-Token-Rejected, BatchHttpLink calls observer.next(result) and then observer.complete() synchronously in the same Promise .then(). The next handler detected the rejection and kicked off an async token refresh without forwarding the value — but the synchronous complete: () => observer.complete() fired before the retry could emit, triggering Apollo Client 4's validateDidEmitValue guard. Fix: call activeSubscription.unsubscribe() synchronously inside the next handler the moment bearer rejection is detected. This marks the rxjs Subscriber as isStopped before BatchHttpLink's .complete() runs, so that call becomes a no-op. The retry then proceeds normally and emits a value through a fresh subscription. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Purpose
Apollo was throwing "The link chain completed without emitting a value" when loading pages in background tabs (or whenever the server sends
X-Bearer-Token-Rejected: trueon a response).The root cause was a race condition in
buildRefreshOnRejectedBearerLink.BatchHttpLinkcallsobserver.next(result)and then immediately callsobserver.complete()synchronously in the same Promise.then()callback. When thenexthandler detected a bearer rejection, it kicked off an async token refresh and returned — without ever callingobserver.next()on the outer observable. But the synchronouscomplete: () => observer.complete()handler fired before the retry had a chance to emit anything. Apollo Client 4'svalidateDidEmitValueguard sees this and throws.The intended defense (calling
activeSubscription.unsubscribe()at the top ofrunOnce()) only ran afterensureFreshAccessToken()resolved asynchronously — too late.Changes
💻 Engineer-facing
nexthandler, callactiveSubscription.unsubscribe()synchronously the moment rejection is detected. This marks the rxjsSubscriberasisStoppedbeforeBatchHttpLink's.complete()runs, making that call a no-op. The retry proceeds normally and emits a value through a fresh subscription.Background tabs were the most common trigger because bearer rejection is more likely when a token is near expiry — tabs that have been sitting open for a while naturally hit this more often.
Release plan and notes
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