Fail closed on GitHub API errors during the sync workflow.

[vorporeal]

Description

get_pr_for_commit() was silently catching CalledProcessError and returning None on GitHub API failures. The loop detection code in is_sync_originated() treated this the same as "no PR found," causing it to fail-open: sync-originated commits were not filtered out, and the sync workflow created reverse-direction PRs that should never have existed.

This was the root cause of warpdotdev/warp#9591 (and 3 other PRs created on 2026-04-30), where public→private sync commits were synced back to public.

The fix removes the blanket except from get_pr_for_commit() so API errors propagate. In the loop detection path this aborts the sync run; in non-critical call sites (PR description building, reviewer lookup) the callers now catch and degrade gracefully with logging.

Testing

Added test_api_failure_propagates_when_trailer_present to verify that is_sync_originated raises on API failure instead of returning False. All existing loop detection tests continue to pass.

Co-Authored-By: Oz oz-agent@warp.dev

[vorporeal]

• Fail closed on GitHub API errors during the sync workflow. #38 👈 (View in Graphite)
• main

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