What is opal AGENTS.md?

Project instructions for Opal, a coding-agent framework written in Elixir. They describe its architecture, command-line interface, built-in tools, and development commands.

Use them when working on Opal's agent engine, terminal interface, file and shell tools, child agents, or task tracker, and when running its development checks.

They give an agent the project-specific context needed to modify Opal consistently. They also document the commands used to run, test, lint, and release the project.

How matteing/opal configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to matteing/opal. 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/matteing/opal/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/matteing/opal

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/matteing/opal/agents-md/github.svg)](https://agentmods.dev/instructions/matteing/opal/agents-md)

Your own site

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

Per session 206 This file is loaded in full into every session.

When invoked 206 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00206	$0.00206
Opus 5.5	$0.00082	$0.00082
Sonnet 5.5	$0.00041	$0.00041
Haiku 4.5	$0.00021	$0.00021

Measured 2mo ago against content hash 893cb4e8609c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

opal 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.

AGENTS.md · 31 lines

What it actually says

Opal Project Guide

Opal is a coding agent harness built with Elixir/OTP for AI coding agents.

Architecture

Everything is a Process - Agent loops, sessions, and tools are GenServers
Cross-Platform - Works on macOS, Linux, and Windows

Components

opal/ - Elixir SDK (agent engine, tools, providers)
cli/ - Terminal UI application

Built-in Tools

read_file, write_file, edit_file - File operations with hashline tags
grep - Cross-platform search with glob filtering
shell - Cross-platform command execution
sub_agent - Spawn child agents for parallel work
tasks - Task tracker for planning

Development

mise run dev    # Run TUI
mise run test   # Run tests
mise run lint   # Check code quality
mise run release # Release

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.

2mo ago First seen · 31 lines · 206 tokens per session scan A 893cb4e8609c

Subscribe to this mod's changes

opal AGENTS.md is an instructions file published in the GitHub repository matteing/opal (62 stars, last pushed 2mo ago), licensed MIT. It adds 206 tokens to every session, about $0.0008 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 2026-08-30.

Building agents LLM agents ai ai-agents cli elixir

opal AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
opal AGENTS.mdmatteing/opal	Instructions file	62	2mo ago	MIT	A	206	Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	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	yesterday	MIT	A	4,680	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	274k	2d ago	MIT	A	4,313	Codex, OpenCode

opal: Instructions file for Codex