fix(session-replay): prevent blob worker errors from surfacing as uncaught#1561
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lewgordon-amplitude wants to merge 2 commits intomainfrom
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fix(session-replay): prevent blob worker errors from surfacing as uncaught#1561lewgordon-amplitude wants to merge 2 commits intomainfrom
lewgordon-amplitude wants to merge 2 commits intomainfrom
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…aught When new Worker(blobUrl) fails (e.g. Firefox ETP, private browsing), the onerror handler correctly falls back to sync compression but was not calling e.preventDefault(). Per the Worker spec this causes the ErrorEvent to re-fire on window.onerror, making a graceful degradation appear as an unhandled crash in the console and error monitoring. Fixes SR-2657 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Adds a test that properly verifies e.preventDefault() is called when the blob worker fires an error, using a MockWorker with an onerror setter to capture and invoke the handler with a real mock ErrorEvent. The existing test.each error case was passing incidentally — the TypeError from calling preventDefault on a plain object was silently swallowed by addCompressedEvent's DataCloneError try/catch. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
When new Worker(blobUrl) fails (e.g. Firefox ETP, private browsing), the onerror handler correctly falls back to sync compression but was not calling e.preventDefault(). Per the Worker spec this causes the ErrorEvent to re-fire on window.onerror, making a graceful degradation appear as an unhandled crash in the console and error monitoring. This is related to a sentry error we're seeing on Amplitude: https://amplitude.sentry.io/explore/releases/2b6289da0df5804a5c2ae4d63fdfb90d8876744e/?project=78869
Checklist
Note
Low Risk
Low risk: a small change to web worker error handling plus a targeted unit test; behavior remains a graceful fallback to non-worker compression.
Overview
Fixes session replay web-worker compression fallback by calling
preventDefault()inEventCompressor’sworker.onerrorhandler, preventing worker errors from bubbling towindow.onerroras uncaught.Adds a unit test to assert
preventDefault()is invoked and that the existing fallback behavior still terminates the worker and clearseventCompressor.worker.Written by Cursor Bugbot for commit a95307d. This will update automatically on new commits. Configure here.