critic

critic is an agent for Claude Code from rennf93/opus-fable-playbook. It costs 48 tokens per session (306 once invoked), scanned A, original, MIT.

An adversarial verifier that tests claims about code changes by reading the actual files, running relevant checks, and probing edge cases. It labels each claim confirmed, refuted, or unverifiable.

In plain words
What is it for?
Use it before claiming a substantial change is fixed or passing, especially for checking tests, error paths, boundary cases, and concurrency behavior.
Why use it?
It reduces the risk of declaring a fix complete based only on assumptions or descriptions. It looks specifically for counterexamples and requires observed evidence.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the fable-mode plugin — 3 skills, 2 commands, 1 agent, 7 hooks shipped together

Good fit Use it before claiming a substantial change is fixed or passing, especially for checking tests, error paths, boundary cases, and concurrency behavior.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/rennf93/opus-fable-playbook/critic
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.

Clone the repo
git clone --depth 1 https://github.com/rennf93/opus-fable-playbook

Made for: Claude Code.

Or install fable-mode, the plugin that ships this one along with the rest of its 3 skills, 2 commands, 1 agent, 7 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 critic

README.md
[![agentmods](https://agentmods.dev/badge/agents/rennf93/opus-fable-playbook/critic/github.svg)](https://agentmods.dev/agents/rennf93/opus-fable-playbook/critic)
Your own site
<a href="https://agentmods.dev/agents/rennf93/opus-fable-playbook/critic"><img src="https://agentmods.dev/badge/agents/rennf93/opus-fable-playbook/critic/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for critic

Your own site · 80×15
<a href="https://agentmods.dev/agents/rennf93/opus-fable-playbook/critic"><img src="https://agentmods.dev/badge/agents/rennf93/opus-fable-playbook/critic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 48 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 306 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 $0.00048 $0.00306
Opus 5 $0.00024 $0.00153
Sonnet 5 $0.00010 $0.00061
Haiku 4.5 $0.00005 $0.00031

Measured 9d ago against content hash 3a579803e212, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

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 9d 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/critic.md · 27 lines

What it actually says

You are an adversarial verifier. You receive a claim (e.g. "the race condition in worker.py is fixed and all tests pass") plus pointers to the relevant code. Your mission is to REFUTE it.

Procedure:

  1. Restate the claim as falsifiable statements.
  2. Attack each: read the actual code (not the description of it), run the tests/commands yourself, probe edge cases the claim glosses over (boundaries, concurrency, empty inputs, error paths).
  3. Verdict per statement: CONFIRMED (you tried to break it and failed — cite the evidence), REFUTED (here is the counterexample or failing output, verbatim), or UNVERIFIABLE (say exactly what's missing).

Rules: never modify files; never accept "should work" reasoning — only observed behavior counts; quote failing output verbatim; if you are uncertain, that is UNVERIFIABLE, not CONFIRMED.

Your final message is your return value for the caller: a verdict list with evidence and file:line references, raw findings — not a human-facing narrative.

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. 9d ago First seen · 27 lines · 48 tokens per session scan A 3a579803e212

Subscribe to this mod's changes

critic is an agent published in the GitHub repository rennf93/opus-fable-playbook (34 stars, last pushed 2mo ago), licensed MIT. It adds 48 tokens to every session and 306 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.

Related

Other agents, from other repositories

architect

Deep technical work. Use for complex implementation, deep debugging, cross-module reasoning, architecture review, and risky or security-sensitive changes (auth, billing, migrations, concurrency, caching, data consistency, public APIs). Also reviews work from cheaper agents for hidden flaws.

realgarit/fable-baton · 54 tokens

qc-lead

QC team lead — the truth audit. Verifies factual claims in every team's outputs by running commands, and prepares evidence for verification reviews.

MohamedEmbarak/Supreme-Leader · 31 tokens

software-development-lead

Development team lead. Architecture, implementation, and code review. Ships diffs, not essays.

MohamedEmbarak/Supreme-Leader · 24 tokens

reflection-judge

Post-processes reflect candidates — validates that cross-session evidence citations actually exist in S-NNN-REPORT.md before proposals or micro-approvals are queued. Returns ACCEPT | DOWNGRADE: | SUPPRESS per observation.

gtapps/claude-code-hermit · 50 tokens

symfony-security-auditor

Read-only security audit of Symfony authentication and authorization: firewalls, accesscontrol, voters, API Platform security, rate limiting, CSRF, password hashing, and input validation. Use proactively after changes to security.yaml, voters, controllers, forms, or API resources.

dev-toolings/superpowers-symfony · 60 tokens

architecture-reviewer

Architecture and design review agent — read-only. Evaluates structural decisions, identifies design smells, and flags risks before implementation. Never modifies code. Use before merging architectural changes or after a planner produces a plan.

FlorianBruniaux/claude-code-plugins · 45 tokens