mycelium CLAUDE.md

mycelium CLAUDE.md is an instructions file for coding agents from haabe/mycelium. It costs 3,725 tokens per session, scanned B, original, MIT.

Project instructions for Mycelium, a theory-guided system for developing products with coding agents. They describe its operating rules, staged process, and measurements of warning accuracy.

In plain words
What is it for?
Following Mycelium's development process, applying its operating contract, working through its stages, and evaluating guard or warning results.
Why use it?
They give the agent the project's current rules and explain how to interpret pipeline warnings, including cases where a warning may be a false positive.

Instructions file

Installs and runs on its own, but its text points at files inside the plugin that ships it — anything it tells you to read at a ${CLAUDE_PLUGIN_ROOT} path is only there once the plugin is installed.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add instructions/haabe/mycelium/claude-md
Clone the repo
git clone --depth 1 https://github.com/haabe/mycelium

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for mycelium CLAUDE.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/haabe/mycelium/claude-md.svg)](https://agentmods.dev/instructions/haabe/mycelium/claude-md)
Your own site
<a href="https://agentmods.dev/instructions/haabe/mycelium/claude-md"><img src="https://agentmods.dev/badge/instructions/haabe/mycelium/claude-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 3,725 This file is loaded in full into every session.
When invoked 3,725 The same file — it is already loaded in full.
Security scan B 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.03725 $0.03725
Opus 5 $0.01862 $0.01862
Sonnet 5 $0.00745 $0.00745
Haiku 4.5 $0.00373 $0.00373

Measured today against content hash d0f6fb648c65, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

mycelium CLAUDE.md scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

**Canvas writes — Read before Write (HARD RULE).** Canvas files ship pre-populated, so every `.claude/canvas/*.yml` exists on a fresh project. `Write`/`Edit` require a prior **`Read` tool** call (same session); **`cat`/`
CLAUDE.md · 129 lines

How it starts

The opening of the file, as written. The whole thing — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Mycelium: Theory-Guided Agentic Product Development

Version 0.175.2 -- Attribution label: readme-pie-palette-meets-wcag-on-both-surfaces-2026-09-03 (PATCH). The README pie shipped in near-black fills that all but vanished on GitHub's dark canvas. Re-picked from the validated categorical palette and checked computationally rather than by eye: #3987e5 / #d95926 / #199e70 clear WCAG 1.4.11 (3:1 non-text) against both #ffffff and #0d1117, carry black section labels at 5.4-6.2:1 (clearing 1.4.3's 4.5:1), and pass the dataviz validator's CVD gate in both modes (worst all-pairs deutan Delta E 9.4, normal-vision 20.9). Slice borders are white at 2px, which reads as a separator gap on the light surface and a crisp ring on the dark one, plus a #8b949e outer ring that clears 3:1 on both. Title and legend colors are deliberately NOT pinned, so GitHub's per-mode theme still supplies them. Prior: 0.175.1 -- Attribution label: readme-backs-discovery-claim-with-a-count-2026-09-03 (PATCH). The README's claim that nobody thinks discovery is optional rested on one person's word for it. Added a hand-read count instead: 46 shipped-to-no-traction posts across r/microsaas, r/SideProject and r/vibecoding, 37 of 46 never mentioning contact with anyone who had the problem. New receipts case docs/receipts/cases/2026-08-16-l1-population-read.md carries the method and the limits (floor not a rate, timing not coded). A craft audit found and fixed the three weakest sections of the README in the same pass, judged by voice against the rest of the file rather than by keyword.

Full version history: docs/changelog.md.

Mycelium is a harnessing system for AI-assisted product development. It connects theories, shares learning, adapts to conditions, and makes the whole ecosystem stronger.

You are an agent operating within Mycelium. Every action you take must be guided by the frameworks below, harnessed by the guardrails, and logged in the decision system.

Read the full file on GitHub · 129 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today Changed · +140 tokens per session d0f6fb648c65
  2. today Changed · -66 tokens per session a594546afadb
  3. 4d ago First seen · 129 lines · 3,651 tokens per session scan B efe9378df8dd

Subscribe to this mod's changes

mycelium CLAUDE.md is an instructions file published in the GitHub repository haabe/mycelium (45 stars, last pushed today), licensed MIT. It adds 3,725 tokens to every session, about $0.0186 per session on Opus 5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.