Borrowing it
Nothing to install: this file belongs to rhein1/fable5-codex. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/rhein1/fable5-codex/main/AGENTS.mdgit clone --depth 1 https://github.com/rhein1/fable5-codexWrote 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.
[](https://agentmods.dev/instructions/rhein1/fable5-codex/agents-md)<a href="https://agentmods.dev/instructions/rhein1/fable5-codex/agents-md"><img src="https://agentmods.dev/badge/instructions/rhein1/fable5-codex/agents-md/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.
<a href="https://agentmods.dev/instructions/rhein1/fable5-codex/agents-md"><img src="https://agentmods.dev/badge/instructions/rhein1/fable5-codex/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00372 | $0.00372 |
| Opus 5.5 | $0.00149 | $0.00149 |
| Sonnet 5.5 | $0.00074 | $0.00074 |
| Haiku 4.5 | $0.00037 | $0.00037 |
Grade A, and why
fable5-codex AGENTS.md 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 2mo 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.
What it actually says
Fable-5 Repo Instructions
Use this repository to develop and validate the Fable-5 Codex plugin.
Working Method
For substantive engineering tasks, prefer the Fable-5 workflow style:
- Map the target before changing it.
- Split discovery into independent lenses when the task benefits from broader coverage.
- Require evidence for claims: file path, line number when available, and quoted source or observed behavior.
- Verify candidate findings adversarially before reporting them as real.
- Preserve unknowns, refuted findings, and coverage gaps instead of hiding them.
- For audits, reviews, fact-checks, sweeps, and design choices, use the installed Fable-5 Codex skills:
$fable-audit$fable-deep-review$fable-fact-check$fable-understand$fable-design-options$fable-sweep
Use real Codex subagents for large or high-risk Fable tasks when the runtime exposes a subagent tool and the user has not opted out. Treat repo-wide, cross-package, security/privacy/money/data/API, migration, release, exhaustive audit, deep review, and broad sweep tasks as large by default. For routine edits, use the rigor rules without spawning extra agents.
Package Rules
- Keep plugin code under
plugins/fable5-codex/. - Keep the repo marketplace at
.agents/plugins/marketplace.json. - Keep marketplace
source.pathrelative and./-prefixed. - Do not introduce absolute user-specific paths into repo docs or marketplace files except in examples clearly labeled as local paths.
- Run
scripts/validate-package.ps1after changing packaging, skills, schemas, scripts, or custom-agent profiles.
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.
- 2mo ago First seen · 31 lines · 372 tokens per session scan A 0c585c10bb7a
fable5-codex AGENTS.md is an instructions file published in the GitHub repository rhein1/fable5-codex (4 stars, last pushed 6d ago), licensed MIT. It adds 372 tokens to every session, about $0.0015 per session on Opus 5.5. 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.
Other instructions, from other repositories
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