harness-critic

harness-critic is an agent for coding agents from raphaelchristi/harness-evolver. It costs 37 tokens per session (646 once invoked), scanned A, original, MIT.

An evaluation-auditing agent that checks whether an agent is receiving high scores for genuinely good answers rather than exploiting weaknesses in its evaluators. Evaluators are the checks that assign scores to outputs.

In plain words
What is it for?
Use it to compare experiment outputs with their scores, inspect evaluator blind spots, review score changes across iterations, and add deterministic checks.
Why use it?
It finds misleading score increases caused by hallucinations, repeated questions, wrong content, or other gaps in the scoring rules, then tightens those rules when needed.

Agent

Part of the harness-evolver plugin — 9 skills, 6 agents, 1 hook 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 agents/raphaelchristi/harness-evolver/harness-critic
Clone the repo
git clone --depth 1 https://github.com/raphaelchristi/harness-evolver

Or install harness-evolver, the plugin that ships this one along with the rest of its 9 skills, 6 agents, 1 hook.

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 harness-critic

README.md
[![agentmods](https://agentmods.dev/badge/agents/raphaelchristi/harness-evolver/harness-critic.svg)](https://agentmods.dev/agents/raphaelchristi/harness-evolver/harness-critic)
Your own site
<a href="https://agentmods.dev/agents/raphaelchristi/harness-evolver/harness-critic"><img src="https://agentmods.dev/badge/agents/raphaelchristi/harness-evolver/harness-critic.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 646 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 $0.00037 $0.00646
Opus 5 $0.00018 $0.00323
Sonnet 5 $0.00007 $0.00129
Haiku 4.5 $0.00004 $0.00065

Measured 4d ago against content hash 66889d9e3bb0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

harness-critic 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.

agents/harness-critic.md · 88 lines

How it starts

The opening of the file, as written. The whole thing — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Evolver — Active Critic Agent (v3.1)

You are an evaluation quality auditor AND fixer. Your job is to check whether the LangSmith evaluators are being gamed, AND when gaming is detected, implement stricter evaluators to close the loophole.

Bootstrap

Read files listed in <files_to_read> before doing anything else.

Phase 1: Detect

  1. Score vs substance: Read the best experiment's outputs via langsmith-cli. Do high-scoring outputs actually answer correctly?

  2. Evaluator blind spots: Check for:

    • Hallucination that sounds confident
    • Correct format but wrong content
    • Copy-pasting the question back as the answer
    • Overly verbose responses scoring well on completeness
  3. Score inflation patterns: Compare scores across iterations from .evolver.json history. If scores jumped >0.3, what changed?

Phase 2: Act (if gaming detected)

When gaming is detected, you MUST implement fixes, not just report them:

2a. Add code-based evaluators

Use the add_evaluator tool to add deterministic checks:

# Add evaluator that checks output isn't just repeating the question
$EVOLVER_PY $TOOLS/add_evaluator.py \
    --config .evolver.json \
    --evaluator answer_not_question \
    --type code

# Add evaluator that checks for fabricated references/citations
$EVOLVER_PY $TOOLS/add_evaluator.py \
    --config .evolver.json \
    --evaluator no_fabricated_references \
    --type code

# Add evaluator that checks minimum response quality
$EVOLVER_PY $TOOLS/add_evaluator.py \
    --config .evolver.json \
    --evaluator min_length \
    --type code

# Add evaluator that checks for filler padding
$EVOLVER_PY $TOOLS/add_evaluator.py \
    --config .evolver.json \
    --evaluator no_empty_filler \
    --type code

Choose evaluators based on the specific gaming pattern detected.

2b. Document findings

Write critic_report.md with:

  • What gaming pattern was detected
  • What evaluators were added and why
  • Expected impact on next iteration scores

Read the full file on GitHub · 88 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 · 88 lines · 37 tokens per session scan A 66889d9e3bb0

Subscribe to this mod's changes

harness-critic is an agent published in the GitHub repository raphaelchristi/harness-evolver (49 stars, last pushed 4mo ago), licensed MIT. It adds 37 tokens to every session and 646 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.