Google: Old TODO comments send coding agents chasing bugs fixed years ago

Google engineer Sam Saccone reports that stale TODO(bug/...) comments distract coding agents in Google's internal traces. About 13% of file-reading sessions encountered one; agents acted on 6% of encounters, mostly unprompted. Of those detours, roughly 41% chased closed tickets. Regression estimates put the cost at 70% more steps, 77% more tokens and 105% more wait time per session, though these figures are unverified and the causal framing rests on observational data. Google's cleanup agent has removed thousands of obsolete references, with over 95% reviewer acceptance.