Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add niels-emmer/myace --skill regression-disciplinegit clone --depth 1 https://github.com/niels-emmer/myaceWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/niels-emmer/myace/regression-discipline)<a href="https://agentmods.dev/skills/niels-emmer/myace/regression-discipline"><img src="https://agentmods.dev/badge/skills/niels-emmer/myace/regression-discipline/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/niels-emmer/myace/regression-discipline"><img src="https://agentmods.dev/badge/skills/niels-emmer/myace/regression-discipline.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00033 | $0.00482 |
| Opus 5 | $0.00016 | $0.00241 |
| Sonnet 5 | $0.00007 | $0.00096 |
| Haiku 4.5 | $0.00003 | $0.00048 |
Grade A, and why
Regression Discipline scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Purpose
A bug fix without a regression test isn't confirmed to have fixed anything — it's confirmed to compile. The regression test is what proves the fix works and what stops the bug from coming back. This skill is a checklist for writing regression tests that actually guard the behavior.
When to use it
Every time a bug is fixed. Also when reviewing a fix to confirm the regression test is real, not a formality.
Checklist
- Write the test against the bug, not the fix. The test should reproduce the reported failure mode — the input that triggered the bug, the behavior that was wrong. It should fail on the old code and pass on the new.
- Confirm it fails first. Run the test against the code before the fix and watch it fail. A regression test that passes on broken code isn't testing the bug.
- Name it for the behavior. The test name should say what behavior is guarded ("rejects empty input", "rolls back on partial failure"), not "test_fix_123".
- Cover the boundary, not just the example. If the bug was an off-by-one, test the boundary values, not just the one that happened to fail.
- Check for related paths. If the bug was a null dereference in one call site, the same root cause may exist elsewhere — a regression test on the shared path guards all of them.
- Don't weaken assertions. A regression test that asserts less than the bug demonstrated (e.g. "doesn't crash" instead of "returns the correct value") lets the bug half-return.
Expected output
For every bug fix, a test that reproduces the reported failure, fails on the old code, passes on the new, and is named for the behavior it guards — so the fix is proven and the regression is caught if it ever returns.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 28 lines · 33 tokens per session scan A 1e9872663b3d
Regression Discipline is a skill published in the GitHub repository niels-emmer/myace (1 stars, last pushed 4d ago), licensed MIT. It adds 33 tokens to every session and 482 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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