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6.27.0 (shipped in 2026.9.1) fetches its new remote config on the Bugsnag IO thread at startup. When that request stalls, a Bugsnag worker holds the NDK lock in synchronizeState while it waits behind the request for the free-disk reading. Every native addBreadcrumb call needs the same lock, so a breadcrumb from the main thread (our trace() in RealSessionController.onAppInForeground, or Bugsnag's own ActivityBreadcrumbCollector in MainActivity.onCreate) ANRs. All eight breadcrumb ANRs on 9.1 show this chain. 6.27.1 queues the native addBreadcrumb on a background task instead of taking the lock on the caller's thread.
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Bugsnag 6.27.0, which shipped in 2026.9.1, can freeze the main thread in
NativeBridge.addBreadcrumb. On 9.1 this accounts for eight ANRs across six devices. Each one shows the same chain across threads:RemoteConfigRequest.requestNewConfig(DNS lookup, connect, or read). Remote config fetching is new in 6.27.0.NativeBridge.synchronizeState, holding the NDK environment lock and parked onDeviceDataCollector.calculateFreeDisk, whose future is queued behind that request.addBreadcrumb. The breadcrumb comes either from ourtrace()inRealSessionController.onAppInForegroundor from Bugsnag'sActivityBreadcrumbCollectorinMainActivity.onCreate.6.27.1 changes
NativeBridgeto queue the nativeaddBreadcrumbas a background task instead of taking the lock on the caller's thread, which removes the frame the main thread blocks in.synchronizeStatestill holds the lock while it collects device data, so other main-thread calls that go straight to the native side could still wait on it. None of the ANRs above took that path.All four Bugsnag artifacts (
bugsnag-android,-core,plugin-android-ndk,plugin-android-anr) resolve to 6.27.1.