Mycelium
Your AI agent should think before it codes.
AI has made building cheap. It hasn't made deciding cheap. Agents will jump from an idea to a pull request without asking why, who for, or whether anyone needs it. Other tools accelerate delivery — Mycelium makes the agent earn the right to start.
# Recommended (post-v0.20.0): install as a Claude Code plugin
/plugin marketplace add haabe/mycelium
/plugin install mycelium@haabe-mycelium
/mycelium:start # one command: setup + 10-minute discovery
Plugin install is brownfield-safe: no project-root files are modified. Skills are namespaced as /mycelium:<name>. See docs/get-started.md for details.
On the namespace prefix. Anthropic's plugin convention requires /<plugin>:<skill>, so every Mycelium skill is /mycelium:foo. Two ergonomics that take the typing tax down:
- Tab completion — type
/myc<Tab> in Claude Code and it expands to /mycelium:. Then a few letters of the skill name + <Tab> finishes it. /mycelium:diamond-assess is six keystrokes.
- Natural-language invocation — you can also just say "run mycelium setup" or "have mycelium assess where we are." Claude Code routes to the right skill. The
/... form is faster once you know the name; prose is fine when you don't.
Legacy install (pre-v0.20.0, still supported during transition):
npx degit haabe/mycelium my-project && cd my-project
# Start Claude Code, then:
/interview
What it is in 5 lines
Build to learn, then build to earn (Patton). 30+ established frameworks, connected by theory gates so critical steps cannot be skipped. The agent does not progress until the evidence says it should. Discovery to market feedback at six scales (Purpose → Strategy → Opportunity → Solution → Delivery → Market), the same four-phase diamond at every scale. Configuration files plus orchestrated prompts — not a software library.
Who it's for
Builders — solo developers or small teams using AI agents to build products. If you can't afford to burn runway on the wrong thing, Mycelium helps you find the right thing before you build it.
Works for software, online courses, AI tools, and services. One command to start. The agent guides you from there.
Who it's not for
Mycelium is for work where deciding what to build is the hard part. Some use cases are better served elsewhere — saying so up front saves frustration:
- Triage-lane work — stale-ticket sweepers, board monitors, fixed-template brief generators. The decision of what to do is already made; you need execution velocity, not discovery. Paddo's boring agents patterns fit these directly.
- Pure execution acceleration in a known scope — the build is decided; just ship it faster. Tools like Addy Osmani's agent-skills optimize this. They compose with Mycelium when discovery is missing, but if discovery is settled, use them directly.
- Projects where the ceremony feels heavier than the value it adds. Mycelium scales gates to project size, but if your project genuinely lacks wrong-build risk, the discipline reads as bureaucracy. That's a fit signal — listen to it.
Time-constrained projects ARE supported as of 2026-04-30: /interview Phase 0 picks <8h inline discovery, 8-48h sprint mode, or 48h+ full interview. The path is selected by your answer to "How much time do you have?"
What it feels like
Not 45 skills dumped on you at once. Three modes that show up at the right time:
| When | Experience | Example |
|---|
| During a phase | Mentor | "Have you considered who your real user is? Here's what the research says about purpose statements." |
| At boundaries | Guardrail | "You're about to skip the bias check. The evidence gate requires this before progressing." |
| At transitions | Checklist | "Before moving forward: evidence ✓, bias check ✗, corrections ✓" |
A small project sees fewer gates and lighter guidance. A complex product gets the full treatment.
How Mycelium got smarter
Mycelium has been dogfooded on three small projects AND tested by one outside user under realistic time pressure. Each session taught the framework something different — and most of what they taught is in the version you're looking at right now.
