mosaic AGENTS.md

mosaic AGENTS.md is an instructions file for Codex, OpenCode from hexxla/mosaic. It costs 1,785 tokens per session, scanned A, original, MIT.

Development rules for Mosaic, a Go codebase organized with hexagonal architecture. This design keeps business rules separate from outside systems such as databases, web requests, and third-party services.

In plain words
What is it for?
Guiding code structure, dependency direction, security, testing, and the roles of the domain, ports, and adapters.
Why use it?
It helps agents keep code responsibilities separate, which makes the project easier to test, maintain, and change safely.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md. Also seen: 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 instructions/hexxla/mosaic/agents-md
Clone the repo
git clone --depth 1 https://github.com/hexxla/mosaic

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.

agentmods badge for mosaic AGENTS.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/hexxla/mosaic/agents-md.svg)](https://agentmods.dev/instructions/hexxla/mosaic/agents-md)
Your own site
<a href="https://agentmods.dev/instructions/hexxla/mosaic/agents-md"><img src="https://agentmods.dev/badge/instructions/hexxla/mosaic/agents-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 1,785 This file is loaded in full into every session.
When invoked 1,785 The same file — it is already loaded in full.
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 $0.01785 $0.01785
Opus 5 $0.00892 $0.00892
Sonnet 5 $0.00357 $0.00357
Haiku 4.5 $0.00178 $0.00178

Measured 5d ago against content hash fbd3839deccf, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

mosaic 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 5d 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 · 179 lines

How it starts

The opening of the file, as written. The whole thing — 179 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Project Instructions

You are working on a production-grade Go codebase that follows strict Hexagonal Architecture (Ports & Adapters).

Your Responsibilities as an Agent

  • Strictly adhere to architectural rules, coding standards, and best practices. Never cut corners.
  • Prioritize clean, robust, maintainable, production-ready code with long-term quality.
  • Refactor messy or unclear solutions properly. Security, testability, and separation of concerns are non-negotiable.

Hexagonal Architecture

This project uses Hexagonal Architecture (also known as Ports & Adapters), originally introduced by Alistair Cockburn.

Core Concepts

  • The domain is the heart of the application and must remain completely independent.
  • All dependencies point inward toward the domain.
  • External concerns (databases, HTTP, third-party APIs, etc.) are pushed to the edges as adapters.
  • The core business logic is decoupled from frameworks, databases, and delivery mechanisms.

Layer Responsibilities & Rules

  • core/domain/ — Pure business entities, value objects, and domain rules. Must have zero dependencies on any other internal package.

  • core/ports/ — Defines clean interfaces (contracts).

    • core/ports/primary/ → Driving ports (inbound use cases)
    • core/ports/secondary/ → Driven ports (outbound contracts)
  • core/services/ — Application services that implement use cases. Depends only on core/domain/ and core/ports/.

  • adapter/ — Concrete implementations of ports.

    • adapter/primary/ → Inbound (HTTP, CLI, gRPC, etc.)
    • adapter/secondary/ → Outbound (databases, external APIs, cache, etc.)
  • config/ — Centralized configuration structures and loading.

Strict Rules

  • Never import adapter/ from core/domain/, core/ports/, or core/services/
  • Never import core/services/ from core/domain/ or core/ports/
  • core/domain/ must remain pure at all times
  • All external interactions must go through ports
  • Follow .golangci.yml (especially depguard rules)

Read the full file on GitHub · 179 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. 5d ago First seen · 179 lines · 1,785 tokens per session scan A fbd3839deccf

Subscribe to this mod's changes

mosaic AGENTS.md is an instructions file published in the GitHub repository hexxla/mosaic (5 stars, last pushed 9d ago), licensed MIT. It adds 1,785 tokens to every session, about $0.0089 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.