pstack: Claude Code proves the bug is fixed before it says done
- GitHub stars
- 3.3K
- skills for Claude Code
- 65
- free, open-source license
- MIT
Claude says "fixed" and the bug is still there. pstack changes the order: Claude first reproduces the failure, then finds the cause, fixes it and runs the same case again, and you get the failing and the passing output as proof. It's a free plugin, and one prompt installs it for you.
What it is
pstack is a free, open-source plugin for Claude Code, MIT license. It's Michael Denyer's port of pstack, the skill stack Lauren Tan (poteto) made for Cursor, and it adds 65 skills to Claude Code.
Its center is poteto-mode. You tell it your goal, and it picks a playbook for the task: bug fix, feature, refactoring, performance issue, investigation and others. Then it follows that playbook step by step.
The bug fix playbook starts with reproducing the failure, even before anyone looks at the code. Then Claude narrows down the cause with evidence from the running program instead of guesses, and only then writes the fix.
After the fix, Claude runs the same case again on the same surface. The original repro has to pass; "inconclusive" or a check on something else doesn't count as a pass.
At the end you get what was broken, the root cause, the fix and how it was verified, with the failing and the passing output quoted.
After the install, a small startup hook tells Claude to use poteto-mode for bugs with an unknown cause, performance issues, design choices and changes across several files. Small tasks it still does directly.
Steps
Step 1. Open Claude Code in your project
Open Claude Code in the folder of the project that has the bug. pstack needs Claude Code 2.1.292 or newer; the prompt checks your version first.
Step 2. Paste the prompt
Claude adds the plugin from one pinned release, checks that it got exactly that version and installs it. Then it asks you to restart Claude Code and tells you what to type in the new window.
Step 3. Describe the bug
Say what happens and what should happen, in plain words, for example: the search filter resets when I change pages. Claude reproduces it and shows you the failing output before it fixes anything.
Step 4. Check the proof
You get the cause, the fix and the same check twice: failing before the fix and passing after it. Nothing is committed, pushed or published without your OK.
Copy this into Claude Code
Install the pstack plugin for Claude Code for me (github.com/michael-denyer/pstack-claude, MIT license), pinned to release v0.9.102. Work step by step: 1. Check my Claude Code version. pstack needs 2.1.292 or newer. If mine is older, tell me how to update it and wait. 2. Add the plugin marketplace from https://github.com/michael-denyer/pstack-claude.git#v0.9.102 (its name is pstack-claude). Check that its checkout is at commit 356c6e0f978df729eb16f227d795f34d221c5aad. If it isn't, remove that marketplace, stop and tell me. 3. Install the plugin pstack@pstack-claude and check that it shows version 0.9.102 and is enabled. Install nothing else: the optional extras pstack mentions (GitHub CLI, Bun, plugin-dev) only if I ask. 4. If a step can only be done by me, give me the exact line to paste into Claude Code and wait. When the plugin is installed, tell me to restart Claude Code and what to type in the new window so you continue from step 5. 5. Ask me to describe one bug in this project: what happens and what should happen. Fix it with pstack's poteto-mode bug fix playbook: reproduce the bug first and show me the failing output, find the cause, fix it, then run the same check again and show me that it passes. Before you change any file, work on a new git branch, or make a backup copy of the project if it isn't in git. Don't commit to my main branch, push, open a pull request or deploy anything without my OK. Explain in plain words what you're doing. I'm not a developer: do everything you can do yourself and tell me only what I have to do by hand.
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Good to know
Other playbooks
poteto-mode also has playbooks for new features, refactoring, performance issues, investigations and prototypes. Describe the task the same way, and it picks the playbook.
Understand code before you change it
The how skill walks you through how a part of your code works, and the why skill looks into why it was built that way. Useful before you touch something you didn't write.
Not only Claude Code
The README also has install steps for Codex, GitHub Copilot, Pi, Muse, OpenCode and Gemini CLI.
The honest read
- pstack makes Claude show the proof on the same check it reproduced, instead of promising a fix. It still depends on that check: if the bug doesn't show up on your computer, Claude adds logging or narrows down the conditions, and asks you only for a specific detail it can't reach.
- It's built for code in a git project. Its playbooks normally end with commits and a pull request; the prompt tells Claude to ask you before it commits, pushes or opens one.
- The bug fix playbook hands the investigation and the fix to subagents (the default model for the fix is Opus), so one fix uses more of your Claude plan's limits than a plain request.
- On every session start, a short script from the plugin adds the instruction to use pstack. I read it before writing this guide: it reads pstack's own settings file and prints that instruction, nothing else. setup-pstack turns this automatic routing off.
- The README says pstack has no server and no telemetry: what its skills read goes to your model provider, and its scripts run on your computer.
- The prompt pins release v0.9.102 from October 22, 2026 and checks its exact commit. The project ships new releases often; to move to a newer one later, ask Claude to do the same with the new version.
- It's a third-party project, not from Anthropic. It runs on your own Claude plan and uses your limits.
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I build AI agents and automations for businesses, and do 1:1 consulting calls. Message me on Instagram with what your business does, and I'll tell you what can be automated.
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