---
title: "backprop - bug → spec - Air Market"
description: "A test just failed or someone filed a bug. Instead of fixing it and moving on, this walks you back to the cause and asks whether a written rule in your spec would have caught it, then records the bug…"
canonical: "https://airmarket.ai/app/backprop"
---

[Air Market](/) / [Developer Tools](/category/devtools) / backprop - bug → spec

Skill by [Julius Brussee](/@juliusbrussee)

# backprop - bug → spec

Turn each bug you fix into a rule that catches the next one

## What this does

A test just failed or someone filed a bug. Instead of fixing it and moving on, this walks you back to the cause and asks whether a written rule in your spec would have caught it, then records the bug there. Reach for it after a failure, a bug report, or a post-mortem.

### Top 3 things it does for you

- Trace a failing test back to its cause
- Decide whether this bug deserves a new rule
- Record what went wrong in the spec

## Information

**backprop - bug → spec at a glance**

|  |  |
| --- | --- |
| Kind | Skill |
| Publisher | [Julius Brussee](/@juliusbrussee) |
| Category | [Developer Tools](/category/devtools) |
| Works with | Agent Skills - an open standard supported by 40+ agents |
| Size | 3 KB |
| Licence | MIT |
| Repository | [JuliusBrussee/cavekit](https://github.com/JuliusBrussee/cavekit/tree/028643f913996cfe1c59f261627d167d4ab5477f/skills/backprop) |
| GitHub stars | 1,142 (as of Nov 2026) |

## Security report

**Verified.** AIR scanned this exact version of backprop - bug → spec and flagged nothing. AIR's verdict: **safe**.

**What backprop - bug → spec's check was run against**

|  |  |
| --- | --- |
| Commit | 028643f913996cfe1c59f261627d167d4ab5477f |
| Content hash | 54f0516bec004f30fff36e490ed7ac29fff05a1096ef0db307d8b77754ed1fd0 |
| Files read | [Browse the files at this exact commit](https://github.com/JuliusBrussee/cavekit/blob/028643f913996cfe1c59f261627d167d4ab5477f/skills/backprop/SKILL.md) |

A scan is named by the exact content it read, not by a version number. A different version is a different artifact, and nothing here applies to a version AIR has not scanned.

[Read the full security report for backprop - bug → spec](/security/backprop)

## About backprop - bug → spec

When something breaks, the fix is only half the work. This is a protocol for the other half: trace the cause, then judge whether a new invariant in the spec would catch the problem coming back, and append the bug to the spec's bug section.

It kicks in on a failing test, a reported bug, a post-mortem, or whenever you ask for it directly. Its authors call it the one non-obvious thing spec-driven development does that plain plan-then-execute does not.

## What's inside

- SKILL.md - instructions

## Questions

### Is backprop - bug → spec safe to install?

AIR scanned this exact version of backprop - bug → spec and flagged nothing. AIR's verdict: safe. The verdict is named by the content that was read, at commit 028643f91399, so it cannot drift onto a version nobody scanned. The full report is at https://airmarket.ai/security/backprop.

### How do I install backprop - bug → spec?

Open https://airmarket.ai/app/backprop on Air Market and use the install action: Air Market hands Claude a prompt naming this exact skill, and Claude sets it up. Source, pinned to the exact commit this listing describes: https://github.com/JuliusBrussee/cavekit/tree/028643f913996cfe1c59f261627d167d4ab5477f/skills/backprop. Install from that link, not the branch.

## Related on Air Market

- [More Developer Tools listings](/category/devtools)
- [Everything by Julius Brussee](/@juliusbrussee)

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Canonical URL: <https://airmarket.ai/app/backprop>