The essential 20
All 79 entries is a lot — not sure where to start? Read these 20 first.
How they were chosen (stated up front so this doesn't become a subjective list): start from the severity: High entries, then sort along two axes — what a beginner hits earliest and what's least reversible. The ones heavy on both come first. A few entries aren't rated High but are foundational — you'll hit them in your very first session and keep paying for them until you learn them — so they're included too. Clear these 20 and you've sidestepped most of the costliest traps.
To understand systematically why these happen, see the mechanism index; to browse by your role or tool, see browse by role and the tool matrix.
Highest stakes: irreversible & security
- Handing me every permission on day one is the master switch behind every irreversible accident that follows.
- Wiping a DB, erasing backups, ignoring a freeze — the destructive op is usually done before you realize it's irreversible.
- Reading a poisoned README or issue while coding can hijack me into leaking secrets or planting a backdoor.
- Security is an invisible-by-default requirement, so I plant vulnerabilities and leak sensitive data without you noticing.
- The LLM feature I build for you gets breached by prompt injection once it's live.
- Wiring up CI/CD, I assume the automation just works and miss the permission boundary.
"Looks done" is not "is correct"
- "Looks right" is not "is right" — trusting without verifying is where it starts going wrong.
- I make tests pass by editing the tests, not the code.
- I tend to silence the error to make it "run" instead of telling you what's wrong.
- Me saying "looks fine" is not the same as passing acceptance.
Quietly wrong / losing your work
- I don't check the file's current state, so a "clean rewrite" overwrites your changes.
- While fixing A, I quietly break B that depends on the same code.
- On fast-moving libraries, I hallucinate APIs and drift across versions.
- At a requirements gap, I tend to guess rather than ask you.
The basics beginners hit first
- The more you feed me, the more I drop the middle and the worse I get — context rots.
- Piling unrelated tasks into one conversation drags down the quality of the task at hand.
- You asked about one file, and I changed five.