What is Cecil AGENTS.md?

A set of working instructions for agents contributing to Cecil, a software project. It describes the project layout, important commands, architecture, and coding conventions.

Use it when navigating the Cecil repository, choosing where to edit, running its checks, understanding its components, and following its versioning and Git practices.

It gives contributors the project context they need before editing files. Following it helps avoid changing generated or restricted areas and keeps development steps consistent.

How Cecilapp/Cecil configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to Cecilapp/Cecil. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/Cecilapp/Cecil/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/Cecilapp/Cecil

Made for: Codex, OpenCode.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/cecilapp/cecil/agents-md/github.svg)](https://agentmods.dev/instructions/cecilapp/cecil/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/cecilapp/cecil/agents-md"><img src="https://agentmods.dev/badge/instructions/cecilapp/cecil/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/cecilapp/cecil/agents-md"><img src="https://agentmods.dev/badge/instructions/cecilapp/cecil/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,348 This file is loaded in full into every session.

When invoked 1,348 The same file — it is already loaded in full.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.01348	$0.01348
Opus 5.5	$0.00539	$0.00539
Sonnet 5.5	$0.00270	$0.00270
Haiku 4.5	$0.00135	$0.00135

Measured 10d ago against content hash bf60d0422199, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Cecil AGENTS.md scanned grade A with 1 finding 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 10d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- When updating code in `src/`, update API documentation with `php phpdoc` command (download `phpdoc` binary with `curl -Lo phpdoc https://phpdoc.org/phpDocumentor.phar` if necessary).

AGENTS.md · 90 lines

The source is not reproduced here

Licensed EUPL-1.2

The repository is licensed EUPL-1.2, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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.

10d ago Changed · +6 lines · +192 tokens per session bf60d0422199
15d ago Changed · +20 lines · +319 tokens per session a8e089c16ea6
26d ago Changed · +5 lines · +136 tokens per session ee31de2b4894
1mo ago Changed · -1 lines · -17 tokens per session ff69c8f23d30
2mo ago First seen · 60 lines · 718 tokens per session scan A eebf12058eb5

Subscribe to this mod's changes

Cecil AGENTS.md is an instructions file published in the GitHub repository Cecilapp/Cecil (299 stars, last pushed yesterday), licensed EUPL-1.2. It adds 1,348 tokens to every session, about $0.0054 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

PHP Planning agent-skills flat-file markdown static-site-generator twig

Cecil AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
Cecil AGENTS.mdCecilapp/Cecil	Instructions file	299	yesterday	EUPL-1.2	A	1,348	Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	yesterday	MIT	A	7,461	Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	today	MIT	A	4,680	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	275k	2d ago	MIT	A	4,313	Codex, OpenCode

Cecil: Instructions file for Codex

Borrowing it

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Makes network callslowCapability

The source is not reproduced here

Licensed EUPL-1.2

What this file has done since we first saw it

Cecil AGENTS.md compared with instructions from other repositories