Harness Gepa

Surfaces the GEPA (genetic-evolution prompt-adaptation) library exports from @metaharness/darwin/gepa. Unlike the other skills in this plugin there is no CLI binary behind this — the script dynamic-imports the library (local resolution first, versioned cache install as fallback) and calls the subprocess-safe subset.

When to use

• Adopting an evolved policy: --op render shows the actual system prompt a genome compiles to — read THAT, not the raw JSON, before wiring a genome into a harness.
• Auditing a promotion: --op genome loads + validates the shipped cand-6 genome (first holdout-confirmed cheap-tier promotion; provenance ships in the package) or any genome file you point at.
• CI gate on genome edits: --op validate --alert-on-invalid exits 1 on structural errors.
• Debugging a bad run: --op analyze --transcript run.json classifies failure modes (GEPA's failure-class taxonomy) from a transcript array.

What is deliberately NOT here

gepaOptimize — the optimization loop takes an in-process evaluate(candidate) callback ("bring your own evaluator") that cannot cross a subprocess boundary. Two supported paths instead:

1. Library consumers: import { gepaOptimize, loadCand6Genome } from '@metaharness/darwin/gepa'
2. Sandbox-scored evolution: harness-evolve (darwin CLI evolve), which pairs GEPA with its own sandbox evaluators.

Algorithm

Implementation: scripts/gepa.mjs.

1. import('@metaharness/darwin/gepa'); on MODULE_NOT_FOUND fall back to a one-time npm install --prefix ~/.ruflo/darwin-cache-0.8.0 and import the cached dist/gepa/index.js (versioned dir → pin bumps invalidate).
2. Dispatch --op:
   • genome → loadGenome(fs, path) or loadCand6Genome() + validateGenome
   • validate → validateGenome(rawJson) (raw parse so broken files reach the validator instead of throwing in the loader)
   • render → buildSystemFromGenome(genome, ext?, glob?)
   • analyze → analyzeTranscript(entries)
3. Emit one JSON object; exit 0 (or 1 under --alert-on-invalid, 2 on bad input).

Examples

node scripts/gepa.mjs --op genome                          # cand-6 + validation
node scripts/gepa.mjs --op render | jq -r .system         # what does cand-6 SAY?
node scripts/gepa.mjs --op validate --path my-genome.json --alert-on-invalid
node scripts/gepa.mjs --op analyze --transcript run.json

Exit codes

• 0 — op completed (or degraded — darwin not installable)
• 1 — --alert-on-invalid and validation found errors
• 2 — config error (unknown op, missing/broken input file)