fan-out

fan-out is a skill for Claude Code from haabe/mycelium. It costs 27 tokens per session (523 once invoked), scanned A, original, MIT.

A way to split several solution explorations or research tasks among separate agents, then bring their results together for comparison. The process is called fan-out and fan-in because work spreads out in parallel and then returns to a lead agent.

In plain words
What is it for?
Use it when multiple solutions, delivery tasks, or research streams can be explored independently, including comparing competing options and recording the final decision.
Why use it?
It reduces the delay of handling independent options one at a time and gives decisions a common evidence-based comparison.

Skill for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable. Also seen: mentions subagents.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the mycelium plugin — 61 skills, 6 hooks shipped together

Good fit Use it when multiple solutions, delivery tasks, or research streams can be explored independently, including comparing competing options and recording the final decision.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add haabe/mycelium
Claude Code
/plugin install mycelium

Made for: Claude Code.

Or install mycelium, the plugin that ships this one along with the rest of its 61 skills, 6 hooks.

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 fan-out

README.md
[![agentmods](https://agentmods.dev/badge/skills/haabe/mycelium/fan-out.svg)](https://agentmods.dev/skills/haabe/mycelium/fan-out)
Your own site
<a href="https://agentmods.dev/skills/haabe/mycelium/fan-out"><img src="https://agentmods.dev/badge/skills/haabe/mycelium/fan-out.svg" alt="Measured on agentmods" height="20"></a>
Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 523 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00027 $0.00523
Opus 5 $0.00014 $0.00262
Sonnet 5 $0.00005 $0.00105
Haiku 4.5 $0.00003 $0.00052

Measured 8d ago against content hash ade6396f7edc, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

fan-out scanned grade A with 0 findings 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 8d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/mycelium/skills/fan-out/SKILL.md · 54 lines

What it actually says

Fan-Out / Fan-In Orchestration

When to Use

  • OST has 2+ solutions for the same opportunity that need parallel exploration
  • Independent delivery work items that can be parallelized
  • Multiple research streams needed simultaneously

Workflow

1. Prepare (Lead Agent)

  • Read .claude/canvas/opportunities.yml
  • Identify solutions needing parallel work
  • For each: identify riskiest assumption and design test

2. Fan-Out (Spawn Workers)

For each solution:

  • Spawn subagent or Agent Team member
  • Provide: clear task, read-only canvas context, worktree isolation, time bound
  • Each worker runs independently

3. Fan-In (Collect Results)

  • Collect all worker results
  • Update ICE scores in canvas
  • Run /mycelium:bias-check on combined findings
  • Select winner(s) based on evidence
  • Log decision in .claude/harness/decision-log.md

Leaf Bakeoff Mode

When comparing competing OST leaves for the same opportunity:

  • Each worker returns a structured scorecard (Four Risks + ICE + assumption test result + segment fit)
  • Lead agent applies winner selection rules: clear winner (>20% ICE delta), close race (tiebreaker), segment split (both advance), both fail (archive and re-evaluate)
  • Losers are archived to .claude/canvas/archived-solutions.yml with full evidence snapshot

See ${CLAUDE_PLUGIN_ROOT}/orchestration/leaf-bakeoff.md for the complete bakeoff protocol.

Rules

  • Workers NEVER write to canvas (lead agent does)
  • Workers NEVER progress diamonds
  • Lead agent ALWAYS runs bias check on combined results
  • Minimum 2 workers for meaningful comparison
  • Maximum 3 leaves per bakeoff (respects L3 WIP ceiling)

See ${CLAUDE_PLUGIN_ROOT}/orchestration/agent-teams.md for full orchestration patterns.

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. 8d ago First seen · 54 lines · 27 tokens per session scan A ade6396f7edc

Subscribe to this mod's changes

fan-out is a skill published in the GitHub repository haabe/mycelium (45 stars, last pushed 2d ago), licensed MIT. It adds 27 tokens to every session and 523 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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