Claude Code Made 6 Mistakes on Legacy Code. None Reached a Commit.

Free checklist (12 checks, plus a fill-in CLAUDE.md template): https://legacy2latest.kit.com/83f5e476d0 Claude Code made 6 mistakes during a full framework upgrade of a legacy service (a Java 11 / Spring Boot 2.7 demo API, built to look like real legacy code, taken to Java 25 / Spring Boot 4.1). Here is each one, from the real session transcripts, and the guardrail that caught it before it reached a commit. Chapters 00:00 Six mistakes, zero commits 00:34 The legacy service 01:43 Mistake 1: the test count 02:25 Mistake 2: two false claims in a plan 03:39 Mistake 3: a decision it shouldn't have made 04:54 Mistake 4: a broken API contract, with a green build 06:15 Mistake 5: a confident, wrong root cause 07:20 Mistake 6: a check that hid a failing build 08:31 The pattern 09:14 Next video Every Claude Code session in this video is a real run, replayed from its transcript. I'm Daniel, a senior full-stack engineer. Views are my own. #ClaudeCode #AICoding #LegacyCode