Legacy Code

You'll learn how old comments, fixtures, docs and error strings in a legacy repo can act as prompt injection for coding agents, how to find and triage them, and how to limit the damage when one slips through.

You'll learn why coding agents copy the patterns in your existing code instead of following the rules in CLAUDE.md, and how a four-step exemplar audit finds and fixes the files they copy most.

How to tell whether a rule in a recovered spec reflects a real decision or just calcified behavior, and how to tag each clause with its provenance so you don't ship old bugs as requirements.

Every signal a reviewer — human or agent — could see said the function was safe to delete; the only thing that said otherwise lived in a Slack thread a workspace reorg had already erased.