Professional Agentic Product Engineering

Chapter

Common failure patterns — catch them before they cost you

The coach plugin catches these in real time. The table is the fast index; each "Tip T.N" links to the full Instead/Prefer in the guide.

The habit The fix Tip
Handing the agent a file list ("create these 15 files…") Hand over the outcome + constraints, not a file list Tip 1.1
Writing a vague ask ("clean up", "improve", "make it work") Be specific — name the symbol/file/change Tip 1.2
Phrasing it as "don't do X" Say what to do, not what to avoid Tip 1.3
Giving a rule with no reason Add the why — motivation makes it generalize Tip 1.4
Describing a bug or layout issue in prose Show, don't tell — paste the screenshot + @Component.tsx; pipe raw logs straight in Tip 1.8
Begging "think hard / ultrathink" everywhere Dial effort instead; reserve ultrathink for one hard turn Tip 1.13
Firing a one-liner and steering the whole task turn by turn Say it all in your first message — one complete brief beats ten corrections Tip 1.14
Jumping straight to code in unfamiliar areas Investigate first (read-only), then edit Tip 2.1
Letting the agent touch many files unsupervised Force an approval checkpoint + blast radius Tip 2.3
Asking for one big feature in one pass Slice vertically — thin end-to-end increments Tip 2.5
Dumping the whole repo / huge context Feed high-signal context, not everything Tip 3.1
Keeping secrets/keys in the repo, or pasting a key Keep secrets out of git and context (.env + gitignore) Tip 3.2
Re-fixing the same bug over and over in one session /clear and rewrite the opening prompt Tip 3.3
Re-explaining the same conventions each session Put them in CLAUDE.md Tip 3.5
Working with no checkable "done" Make the Definition of Done executable Tip 4.1
Implementing without a failing test first Do TDD — failing test first; don't edit tests to pass Tip 4.2
Accepting "done, it works" with no proof Demand evidence — the test command + its output Tip 4.5
Asking for a "conservative" review Ask for all findings, severity-labeled — a conservative prompt suppresses real ones Tip 4.6
Running long work that loses progress Commit every green step — checkpoints to revert to Tip 5.1
Putting one agent on a huge audit/refactor Let it self-orchestrate parallel subagents Tip 6.1