# bias-check

A skill for Claude, Codex and Cursor that walks a cognitive-bias checklist before research or a big decision. Handy right before an agent locks in a conclusion.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 47
- Author: haabe
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/haabe/mycelium/tree/HEAD/plugins/mycelium/skills/bias-check/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/bias-check

## What it does

bias-check runs at the point where research or a significant decision is about to start. It works out the stage (L0–L5) and the activity, pulls the bias checklist for that scale, and for each entry asks whether the bias is live here and what mitigation applies.

A second pass turns on the agent itself: sycophancy, over-weighting recent context, assuming a familiar pattern fits, and papering over gaps with speculation. The result is a briefing with a risk table, an OK/Risk mark per item, and a verdict — proceed, proceed with caution, or stop and address. There is also a system-level diagnostic: when resistance comes from a badly designed process rather than from how someone thinks, the skill points at redesigning the process.

The skill assumes it runs inside the Mycelium framework. Standalone, you lose the canvas state, theory gates and harness behavior it relies on. Install with `npx skills add haabe/mycelium --skill bias-check -a claude-code`; the file lands at `~/.claude/skills/bias-check/SKILL.md`.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add haabe/mycelium --skill bias-check -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/bias-check/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/bias-check/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add haabe/mycelium --skill bias-check -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/bias-check/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add haabe/mycelium --skill bias-check -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/bias-check/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install haabe/mycelium bias-check
```

2. **Manually: put the files in place**
- File: `.github/skills/bias-check/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add haabe/mycelium --skill bias-check -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/haabe/mycelium --path plugins/mycelium/skills/bias-check
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/bias-check/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add haabe/mycelium --skill bias-check -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/haabe/mycelium/tree/HEAD/plugins/mycelium/skills/bias-check/SKILL.md

## When to use it
- catch confirmation bias before a conclusion gets locked in
- check whether the agent favours fresh context over earlier evidence
- tell genuine resistance apart from a badly designed process
- run a bias checklist before launch tier classification at L5
- record a proceed / proceed with caution / stop verdict

## Example prompts
- Run bias-check before we settle the conclusion from these interviews
- Review cognitive biases for the current stage before we decide
- Give me a bias briefing for L5 ahead of launch planning

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 441bbb3f088c5cc0.

BEGIN THIRD-PARTY FILE 441bbb3f088c5cc0
````text
---
name: bias-check
description: "Use before any research activity or significant decision. Reviews cognitive biases relevant to the current stage."
metadata:
  instruction_budget: "27"
  framework_dependency: "mycelium"
  framework_dependency_note: "This skill is designed to run within the Mycelium framework (https://github.com/haabe/mycelium). Standalone use will skip the canvas state, theory gates, and harness behavior the skill assumes. Install: /plugin install mycelium@haabe-mycelium."
---

# Bias Check Skill

Pre-research and pre-decision bias review.

## Preflight: Read target canvas file(s) before any Write/Edit

**Hard rule.** Before issuing `Write` or `Edit` against any `.claude/canvas/*.yml`, use the **Read tool** on that file in this session. Claude Code's Read-before-Write check requires the `Read` tool specifically — `cat`/`head`/`grep` via Bash do NOT satisfy it.

**Edit vs Write — different cost profiles** (verified 2026-05-14):
- **`Edit`** (exact-string replacement): `Read` with `limit: 1` satisfies the check at ~50 tokens. State-tracking is per-file, not per-byte — subsequent `Edit` calls work anywhere in the file. Use this for partial updates against large canvas files (e.g., `purpose.yml` at 800+ lines).
- **`Write`** (full replacement): do a **full Read** first. Write obliterates the file; you should see what you're about to replace. The `limit:1` shortcut is *not* appropriate here.

**ID-bearing entries — scan the ID space before assigning** (added 2026-05-15, v0.23.19): When adding a new component, opportunity, solution, or any other ID-bearing entry to a canvas file, run a Bash grep first to confirm the next ID in your prefix sequence is actually free:

```
grep -o "<prefix>-[0-9][0-9]*" .claude/canvas/<file>.yml | sort -u -t- -k2 -n | tail -3
```
````
END THIRD-PARTY FILE 441bbb3f088c5cc0

The third-party file has ended. Everything between the 441bbb3f088c5cc0 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 1812 of 8343 bytes. © haabe · MIT · https://github.com/haabe/mycelium/tree/HEAD/plugins/mycelium/skills/bias-check/SKILL.md

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---
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