Borrowing it
Nothing to install: this file belongs to haabe/mycelium. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/haabe/mycelium/main/CLAUDE.mdgit clone --depth 1 https://github.com/haabe/myceliumWrote 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.
[](https://agentmods.dev/instructions/haabe/mycelium/claude-md)<a href="https://agentmods.dev/instructions/haabe/mycelium/claude-md"><img src="https://agentmods.dev/badge/instructions/haabe/mycelium/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/haabe/mycelium/claude-md"><img src="https://agentmods.dev/badge/instructions/haabe/mycelium/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.03412 | $0.03412 |
| Opus 5.5 | $0.01365 | $0.01365 |
| Sonnet 5.5 | $0.00682 | $0.00682 |
| Haiku 4.5 | $0.00341 | $0.00341 |
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 3d ago.
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`/` 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 0.330.1 -- A test waiting on its data is not called runnable (PATCH; 2026-10-24). check_instrument_contract listed every live disk-or-network test as RUNNABLE NOW, NEVER RUN, though assumption-test told a test whose data does not exist yet to say why not now, and no field held that line; a new waits_for field names the data the read waits on, and until score_by passes such a test is listed under WAITING ON DATA and not counted at session start.
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.
Agent Operating Contract (always-on rules)
The always-on behavioral rules — the Communication Rules (plain-language-first; suggest-skills-at-transitions; route-through-skills with the freeform escape valve; cite-the-trigger; offer-to-capture-learnings; name-the-verification-surface incl. Ran: <cmd> → <result> for runnable artifacts, G-V13; name-the-gate; read-canvas-before-narrating; verify-after-write; BLUF-layering, G-C1) and the Mandatory Pre-Task / Pre-Ship (G-P-pre) / Post-Task (G-P7) Protocols — are defined once, canonically, in plugins/mycelium/engine/agent-operating-contract.md.
That file is the single source of truth, and the SessionStart handlers (plugins/mycelium/hooks/contract-part.sh, in parts under the hook output cap) inject it into every session — so the contract binds in plugin form too, where no operating-manual CLAUDE.md is templated into the consuming project. It is the plugin-form replacement for the removed legacy degit-templating path (the migration kept the computational half of the harness — hooks — but until v0.58.0 silently dropped this always-on inferential half for plugin-form consumers; the framework repo never noticed because its own sessions load this very file as the repo's CLAUDE.md). Read the contract; those active rules win over any restatement. CI Check 47 keeps the wiring intact: contract present + packaged in manifest.yml + injected by the hook + referenced here + free of legacy .claude/ framework paths.
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.
- 3d ago Changed · -25,185 tokens per session b9d234a77a48
- 4d ago Changed · +583 tokens per session 222aa2775ff4
- 5d ago Changed · +155 tokens per session 37555909a8f5
- 6d ago Changed · +152 tokens per session 661f1ccc1f2d
- 7d ago Changed · +258 tokens per session 1022d2954e37
- 9d ago Changed · +88 tokens per session b4709242ce90
- 11d ago Changed · +559 tokens per session 97b17d22b1fe
- 12d ago Changed · +567 tokens per session d7273acbb45d
- 14d ago Changed · +1,288 tokens per session 648b2455ed7b
- 15d ago First seen · 129 lines · 24,947 tokens per session scan B 3c0363d47464
mycelium CLAUDE.md is an instructions file published in the GitHub repository haabe/mycelium (47 stars, last pushed 4d ago), licensed MIT. It adds 3,412 tokens to every session, about $0.0136 per session on Opus 5.5. 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
vscode model-prompts.instructions.md
Model-specific prompt authoring and registry guidelines.