fable-fact-check

fable-fact-check is a skill for Claude Code, Codex from rhein1/fable5-codex. It costs 76 tokens per session (579 once invoked), scanned A, original, MIT.

A claim-by-claim review that checks statements in documents against source code, tests, files, and runtime evidence. It focuses on claims such as “done,” “tested,” “working,” or “live.”

In plain words
What is it for?
Use it to verify READMEs, changelogs, launch reports, status updates, runbooks, and other claims about a system.
Why use it?
It helps prevent reports and documentation from presenting unverified work as complete or working.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions subagents; mentions Codex.

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/rhein1/fable5-codex/fable-fact-check
Any agent
npx skills add rhein1/fable5-codex --skill fable-fact-check
Clone the repo
git clone --depth 1 https://github.com/rhein1/fable5-codex

Made for: Claude Code, Codex.

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 fable-fact-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/rhein1/fable5-codex/fable-fact-check.svg)](https://agentmods.dev/skills/rhein1/fable5-codex/fable-fact-check)
Your own site
<a href="https://agentmods.dev/skills/rhein1/fable5-codex/fable-fact-check"><img src="https://agentmods.dev/badge/skills/rhein1/fable5-codex/fable-fact-check.svg" alt="Measured on agentmods" height="20"></a>
Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 579 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 5.1 $0.00076 $0.00579
Opus 5 $0.00038 $0.00290
Sonnet 5 $0.00015 $0.00116
Haiku 4.5 $0.00008 $0.00058

Measured 6d ago against content hash 9794f234b4d1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

fable-fact-check 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 6d 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/fable5-codex/skills/fable-fact-check/SKILL.md · 45 lines

How it starts

The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fable Fact Check

Verify claims against actual evidence. Do not edit claims unless the user asks for a correction pass.

For ECF-style governed runs, use ../../references/ecf-run-contract.md. For large or high-risk fact checks, use real Codex subagents when the runtime exposes a subagent tool and the user has not opted out; treat multi-document, launch/status, security/privacy/money/data/API, release-readiness, or many-claim checks as large by default. Otherwise run single-agent multi-lens and say why no subagents were used.

For large or high-risk Fable tasks, recommend running the parent task on gpt-5.6-sol with Ultra (model_reasoning_effort = "ultra") when available. Ultra may delegate proactively, but still explicitly request parallel delegation for disjoint Fable lenses when the runtime supports subagents; otherwise use single-agent multi-lens and report the reason.

Workflow

  1. Identify the document, status report, or claim set.
  2. Restate authority boundaries and declare the ECF run mode: multi-agent only with real spawned subagents, otherwise single-agent multi-lens.
  3. Extract checkable claims. Prioritize words like done, shipped, live, tested, working, complete, supports, secure, verified, deployed, public, and automated.
  4. For each claim, find the implementing source, tests, artifacts, deployment config, or runtime surface that would make it true.
  5. Classify each claim:
    • true
    • false
    • partial
    • stale
    • unverifiable
  6. Cite exact evidence for every classification.
  7. Separate docs/source mismatch from environment/tooling failure.
  8. If asked to fix docs, patch only the claims that evidence disproves or bounds.

Evidence Safety

Never print raw secrets, tokens, private keys, wallet keys, credential files, or .env values. Redact secret-like values and cite only the file/path/key name needed to explain the issue.

Output

Use a compact table when many claims are checked:

Claim | Verdict | Evidence | Correction

Read the full file on GitHub · 45 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. 6d ago First seen · 45 lines · 76 tokens per session scan A 9794f234b4d1

Subscribe to this mod's changes

fable-fact-check is a skill published in the GitHub repository rhein1/fable5-codex (4 stars, last pushed 16d ago), licensed MIT. It adds 76 tokens to every session and 579 once invoked, about $0.0004 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 2026-08-31.

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