reflexion

reflexion is a skill for Claude Code, Codex from haabe/mycelium. It costs 34 tokens per session (1,269 once invoked), scanned A, original, MIT.

A self-correction loop for implementation work: build the deliverable, validate it, review it critically, and retry when needed, for up to three iterations.

In plain words
What is it for?
Use it when producing code, content, prompts, or service workflows that need validation and a limited retry cycle.
Why use it?
It creates explicit opportunities to catch failed requirements, test problems, security issues, and other mistakes before delivery.

Skill for Claude CodeCodex

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

Part of the mycelium plugin — 54 skills, 6 hooks shipped together

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 skills/haabe/mycelium/reflexion
Any agent
npx skills add haabe/mycelium --skill reflexion
Clone the repo
git clone --depth 1 https://github.com/haabe/mycelium

Made for: Claude Code, Codex.

Or install mycelium, the plugin that ships this one along with the rest of its 54 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 reflexion

README.md
[![agentmods](https://agentmods.dev/badge/skills/haabe/mycelium/reflexion.svg)](https://agentmods.dev/skills/haabe/mycelium/reflexion)
Your own site
<a href="https://agentmods.dev/skills/haabe/mycelium/reflexion"><img src="https://agentmods.dev/badge/skills/haabe/mycelium/reflexion.svg" alt="Measured on agentmods" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,269 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00034 $0.01269
Opus 5 $0.00017 $0.00634
Sonnet 5 $0.00007 $0.00254
Haiku 4.5 $0.00003 $0.00127

Measured 4d ago against content hash 722b96a3d071, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

reflexion 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 4d 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/reflexion/SKILL.md · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Reflexion Skill

Self-correcting implementation loop from the n-trax pattern.

Workflow

Iteration Loop (max 3)

Step 1: Implement

  • Create the deliverable according to the specification/acceptance criteria.
    • Software: write code. Content: write/produce content. AI tool: write prompts/configs. Service: document workflow.
  • Follow ${CLAUDE_PLUGIN_ROOT}/harness/engineering-principles.md (principles apply to all product types).
  • Apply patterns from patterns.md.
  • Check corrections.md for relevant past mistakes.

Step 2: Validate

  • Software: Run tests, linter, type checker, security scan, accessibility checks (if UI).
    • Security validation (OWASP): Check input validation, output encoding, parameterized queries, no hardcoded secrets, authentication/authorization patterns, dependency vulnerabilities. Reference OWASP Top 10:2025 categories for each check.
  • Content: Review against learning objectives/editorial standards, check accessibility (captions, alt text), fact-check claims.
  • AI tool: Run eval test cases, red-team testing, bias assessment.
  • Service: Walk through the service blueprint end-to-end, verify documentation completeness.
  • All: Verify acceptance criteria.

Step 3: Self-Critique Review the implementation against (select items relevant to product_type):

  • Engineering principles: DRY, KISS, YAGNI, SoC (apply to all product types)
  • Security: Input validation, output encoding, no secrets, parameterized queries (software, ai_tool)
  • Accessibility: Semantic HTML, keyboard nav, contrast, screen reader (software); captions, transcripts, alt text (content)
  • Edge cases: What happens with unexpected input? Empty? Adversarial? (software, ai_tool)
  • Error handling / user recovery: Are errors handled gracefully? Can users recover? (software, service)
  • Quality: Factual accuracy, style consistency, source attribution (content); eval scores, safety scores (ai_tool)
  • Naming / clarity: Do names reveal intent? Would a new reader understand this? (all)
  • Completeness: Is anything missing that the user would expect? (all)

Read the full file on GitHub · 95 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. 4d ago First seen · 95 lines · 34 tokens per session scan A 722b96a3d071

Subscribe to this mod's changes

reflexion is a skill published in the GitHub repository haabe/mycelium (45 stars, last pushed today), licensed MIT. It adds 34 tokens to every session and 1,269 once invoked, about $0.0002 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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