---
title: "Dev loop"
description: "Four skills for agent-assisted development: reproduce, review the diff, write the release note and check the dependency."
canonical: "https://www.diginomads.win/skills/dev-loop"
source: "content/pages/skills/dev-loop.md"
updatedAt: "2026-11-10"
---

**Level:** Intermediate

## Skills

| Skill | Trigger | Output | Guardrail |
|---|---|---|---|
| reproducer | When a bug report or error trace arrives | A minimal command, a failing test and the observed output before any patch | No application code changes until the failure is reproduced. |
| diff-reviewer | Before a change is merged or handed to a client | Severity-ordered findings with file and line, missing tests and the rollback path | Findings only; the reviewer does not rewrite unrelated code. |
| release-notes | When a version is tagged or a client asks what changed | Behaviour changes, migration steps, rollback notes and known issues | A change with no observable effect for users is not listed as a feature. |
| dependency-check | When adding, upgrading or removing a dependency | Why it is needed, the smallest version range, license, maintenance signal and the rollback version | A dependency is not added for a one-line utility that the standard library already covers. |

## Install

1. Create `skills/reproducer/`, `diff-reviewer/`, `release-notes/` and `dependency-check/` in the repository's agent folder.
2. Give each skill a tool budget: which commands it may run and which paths it may read. Keep the budget in the skill, not in a chat message.
3. Put the test command and the release process in `references/`. The skills should not guess how your project is built.
4. Run the tests below on a small real change. If the reproducer patches before reproducing, the skill is not being followed.

## Tests

- **Prompt:** This test fails on main. Fix it.
  **Pass:** The agent reproduces the failure, writes a failing test and only then patches; it shows the before and after command output.
- **Prompt:** Review this diff before I merge it.
  **Pass:** Findings have severity, file and line, and at least one missing test or rollback risk is reported.
- **Prompt:** Add this small package to parse dates.
  **Pass:** The dependency check states why the standard library is insufficient, the license and the rollback version.

## Sources

- [Agent Skills specification](https://agentskills.io/specification)
- [Anthropic public skills repository](https://github.com/anthropics/skills)
- [Codex CLI documentation](https://learn.chatgpt.com/docs/codex/cli)

## Why this pack

Coding agents are fast at producing plausible diffs and slow at proving them. The dev-loop pack puts the proof in the loop: reproduce, review, document, check the supply chain. Each skill is a checkpoint, not a personality.

The pack assumes the agent can read the repository and run commands. If it cannot, the skills still work as instructions you follow yourself; they just lose the automation.

## The rule behind the pack

No patch without a reproduction; no merge without a rollback. Those two rules prevent most of the expensive failures. The release notes and dependency check make the change legible to the next person, who may also be an agent.

## Adapting it

- For a monorepo, add a path allowlist to the reproducer and a package boundary to the dependency check.
- For a client repository, add their test command, deploy process and incident channel to `references/`.
- For infrastructure changes, add a `plan` diff and a dry-run requirement before the apply.

## Failure modes

- **The reviewer finds only style issues.** Add the risk categories to the skill and require a missing-test finding.
- **The reproducer is a one-line guess.** Require the failing test to fail before the patch and pass after it.
- **The release note is a commit log.** Require the user-visible behaviour change and the migration step.

## Related

- [Reproduce a bug before fixing it](/prompts/reproduce-a-bug)
- [Review a diff for operational risk](/prompts/review-a-diff)
- [How to test a harness in 45 minutes](/harnesses/how-to-test-a-harness)

## Structured data

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