prompt-optimizer SKILL.md skillA
prompt-optimizer from haabe/mycelium is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add haabe/mycelium/prompt-optimizer@git:20260704.7639f18Pins git:20260704.7639f18 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- haabe/mycelium
- Path
plugins/mycelium/skills/prompt-optimizer/SKILL.md- Versions recorded
- 5
- Latest version
- git:20260704.7639f18, committed Jul 4, 2026
- First version recorded
- May 9, 2026
- Size
- 2,186 bytes
- Repository stars
- 51
- License
- MIT
A/B test CLAUDE.md instruction changes against eval benchmarks. Capture baselines, test variants, compare results.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Prompt Optimizer Systematically improve Mycelium instructions through measurement. Adapted from n-trax. ## Commands ### `baseline` -- Capture current performance 1. Run `/mycelium:eval-runner run-split optimization` — record as optimization scores 2. Run `/mycelium:eval-runner run-split holdout` — record as holdout scores 3. Record both to `.claude/optimization/baseline.json`: timestamp, CLAUDE.md hash, optimization metrics, holdout metrics, overall and per-category metrics ### `test <variant>` -- Test a variant 1. Read variant from `.claude/optimization/variants/<variant>.md` 2. Apply the CLAUDE.md changes described 3. Run `/mycelium:eval-runner run-split optimization` — this is the hill-climbing signal 4. Run `/mycelium:eval-runner run-split holdout` — this validates generalization 5. Store results in `.claude/optimization/results/<variant>.json` 6. Compare against baseline. Flag **overfitting** if optimization improves but holdout degrades. 7. Do NOT auto-revert -- let user decide ### `report` -- Compare all variants Generate comparison table with split-aware columns: ``` | Variant | Opt Pass Rate | Holdout Pass Rate | Delta Opt | Delta Holdout | Overfit? | Decision | …
Read the whole file at its exact version.
How to install
mdr add haabe/mycelium/prompt-optimizer@sha256:b253c400e961eaf8The line at the top of this page pins the label git:20260704.7639f18, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_koih44n6vip6jczv)
5 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 5 versions of this file, between May 9, 2026 and Jul 4, 2026, about one every 14 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260704.7639f18 latest | 2026-07-04 | 7639f18 | 2,186 B | A | view · diff |
| git:20260525.9fac942 | 2026-05-25 | 9fac942 | 2,186 B | A | view · diff |
| git:20260522.1825b22 | 2026-05-22 | 1825b22 | 1,876 B | A | view · diff |
| git:20260509.0d17210 | 2026-05-09 | 0d17210 | 1,862 B | A | view · diff |
| git:20260509.4656910 | 2026-05-09 | 4656910 | 1,826 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (2186 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
haabe/mycelium · 51 stars · license MIT · pushed 2026-11-06 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_koih44n6vip6jczv GET https://markdownregistry.com/api/v1/resolve?ref=haabe/mycelium/prompt-optimizer GET https://markdownregistry.com/api/v1/blob/b253c400e961eaf89aca958ee22c389a0de78a74c16703516f6c7f68da7dc8c4
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.