Principle Prove It Works

---
name: principle-prove-it-works
description: "Prove it works. Apply when before declaring a task done, or when judging a claim that something works."
license: MIT
metadata:
  source: "pstack principle-prove-it-works, MIT, Copyright (c) 2026 Lauren Tan, github.com/cursor/plugins, adapted; checked against pstack 0.15.36 at commit 0bb6f37"
---

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# Prove it works

Verify the result by checking the real thing directly. Do not infer it from a proxy, a self-report or "it compiles".

**Why.** Unverified work has unknown correctness. Indirect checks (a file's timestamp, fresh-looking output, an agent's own report, a cached screenshot) feel cheaper than direct observation, and acting on a wrong inference costs far more.

**Check the real thing.**
- Run the feature and inspect the diff.
- Read the actual value, not a cached or derived copy of it.
- Check that a process is alive directly, not through state derived from it.
- When a check fails, suspect the way you observed before you suspect the system.

**Script the check when you can.** The strongest proof is a command that re-runs the same comparison, not a one-time look. Write it, run it, and keep its output visible to the user, where a reviewer can re-run it. Commit it only when a large change, such as a port or a migration, needs a trail that someone can audit later.

**Stop** claiming when the evidence stops. Say what you ran and what you saw, and what you did not verify.