How do I install the Backprop skill?

Run npx skillmds@latest add netvar1337/backprop in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

What does the Backprop skill do?

Use when a bug/test failure should become a new invariant and bug-log entry in SPEC.md. It is listed under Coding & Dev Tools on SkillMD.

Is Backprop safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Backprop?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Backprop free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under MIT.

Who published Backprop?

netvar1337 (@netvar1337) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Backprop by netvar1337 — Agent Skill

Name: Backprop
Author: netvar1337

File contents

Bundled with Unleash skills pack. Source: C:\Users\Admin.agents\skills\backprop\SKILL.md

backprop — bug → spec

Plan-then-execute fixes the code & forgets. SDD fixes the code AND edits spec so recurrence is impossible. That edit is backprop.

WHEN TO BACKPROP

Test failed at /build verification.
User reports bug.
Post-mortem after production incident.
/check flags VIOLATE with root cause found.

SIX STEPS

1. TRACE

Read failure output / bug report. Find exact file:line of wrong behavior. Name root cause in one caveman sentence.

2. ANALYZE

Ask three questions:

Would a new §V invariant catch this class of bug? (most common: yes)
Is §I wrong — did spec claim shape the code cannot deliver? (sometimes)
Is §T wrong — did we build the wrong thing? (rare but real)

3. PROPOSE

Draft the spec change. Never skip §B; §V/§I/§T are case-by-case.

Template:

§B row: B<next>|<date>|<root cause>|V<N>
§V line: V<next>: <testable rule that would have caught it>

Example:

§B row: B3|2026-04-20|refund job ran twice on retry|V7
§V line: V7: ∀ refund → idempotency key check before charge reversal

4. GENERATE TEST

New invariant without test = lie. Add failing test first. Name test so it cites the invariant: TestV7_RefundIdempotent.

5. VERIFY

Fix code. Run test. Must pass. Run full suite. Must not regress.

6. LOG

Commit spec edit + test + code fix together. Commit msg: backprop §B.<n> + §V.<N>: <one-line cause>.

WHAT MAKES A GOOD INVARIANT

Testable in code (grep-able or assert-able).
Scoped to a behavior, not a file.
Stated positively when possible (! hold over ⊥ forbid).
References §I surface where it applies.

Bad: V8: code should be correct. Good: V8: ∀ pg_query ! params interpolated via driver, ⊥ string concat.

WHEN NOT TO ADD §V

Bug was purely mechanical typo with no class (i++ vs i-- in throwaway).
Fix is a one-time migration.
Root cause is external dep (upgrade deps instead, note in §C).

Still append §B entry — record that this failure mode was considered. Future bug with same smell → §B search shows precedent.

OUTPUT SHAPE

Every backprop run produces:

§B entry (always).
§V entry (usually).
Test file (when §V added).
Code fix.
One commit.

No dashboards. No log files. SPEC.md + git is the full history.

---name: backpropdescription: Use when a bug/test failure should become a new invariant and bug-log entry in SPEC.md.license: MIT---> Bundled with Unleash skills pack. Source: C:\Users\Admin\.agents\skills\backprop\SKILL.md# backprop — bug → specPlan-then-execute fixes the code & forgets.SDD fixes the code AND edits spec so recurrence is impossible.That edit is backprop.## WHEN TO BACKPROP- Test failed at `/build` verification.- User reports bug.- Post-mortem after production incident.- `/check` flags VIOLATE with root cause found.## SIX STEPS### 1. TRACERead failure output / bug report.Find exact file:line of wrong behavior.Name root cause in one caveman sentence.### 2. ANALYZEAsk three questions:- Would a new §V invariant catch this class of bug? (most common: yes)- Is §I wrong — did spec claim shape the code cannot deliver? (sometimes)- Is §T wrong — did we build the wrong thing? (rare but real)### 3. PROPOSEDraft the spec change. Never skip §B; §V/§I/§T are case-by-case.Template:```§B row: B<next>|<date>|<root cause>|V<N>§V line: V<next>: <testable rule that would have caught it>```Example:```§B row: B3|2026-04-20|refund job ran twice on retry|V7§V line: V7: ∀ refund → idempotency key check before charge reversal```### 4. GENERATE TESTNew invariant without test = lie. Add failing test first.Name test so it cites the invariant: `TestV7_RefundIdempotent`.### 5. VERIFYFix code. Run test. Must pass. Run full suite. Must not regress.### 6. LOGCommit spec edit + test + code fix together.Commit msg: `backprop §B.<n> + §V.<N>: <one-line cause>`.## WHAT MAKES A GOOD INVARIANT- Testable in code (grep-able or assert-able).- Scoped to a behavior, not a file.- Stated positively when possible (`! hold` over `⊥ forbid`).- References §I surface where it applies.**Bad**: V8: code should be correct.**Good**: V8: ∀ pg_query ! params interpolated via driver, ⊥ string concat.## WHEN NOT TO ADD §V- Bug was purely mechanical typo with no class (`i++` vs `i--` in throwaway).- Fix is a one-time migration.- Root cause is external dep (upgrade deps instead, note in §C).Still append §B entry — record that this failure mode was considered. Future bug with same smell → §B search shows precedent.## OUTPUT SHAPEEvery backprop run produces:1. §B entry (always).2. §V entry (usually).3. Test file (when §V added).4. Code fix.5. One commit.No dashboards. No log files. SPEC.md + git is the full history.

Frequently asked questions

Backprop