tiny-agent-sandbox: Instructions file for Codex

AGENTS.md

tiny-agent-sandbox AGENTS.md is an instructions file for Codex, OpenCode from wesleyzhangwq/tiny-agent-sandbox. It costs 203 tokens per session, scanned A, original, Apache-2.0.

A guide for AI coding agents working on a small MCP server that runs code inside a restricted sandbox. MCP is a way for an agent to use tools from another program.

In plain words
What is it for?
Maintaining and testing the sandbox, including its isolation limits, resource bounds, Docker behavior, lint checks, and tests.
Why use it?
It records security rules and validation commands, helping contributors avoid unsafe sandbox changes and check their work consistently.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md.

This is wesleyzhangwq/tiny-agent-sandbox's own configuration. It tells Codex and OpenCode how to work on tiny-agent-sandbox itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything tiny-agent-sandbox configures →

Reuse

Borrowing it

Nothing to install: this file belongs to wesleyzhangwq/tiny-agent-sandbox. 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/wesleyzhangwq/tiny-agent-sandbox/main/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/wesleyzhangwq/tiny-agent-sandbox

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 tiny-agent-sandbox AGENTS.md

README.md
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Your own site
<a href="https://agentmods.dev/instructions/wesleyzhangwq/tiny-agent-sandbox/agents-md"><img src="https://agentmods.dev/badge/instructions/wesleyzhangwq/tiny-agent-sandbox/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.

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Your own site · 80×15
<a href="https://agentmods.dev/instructions/wesleyzhangwq/tiny-agent-sandbox/agents-md"><img src="https://agentmods.dev/badge/instructions/wesleyzhangwq/tiny-agent-sandbox/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 203 This file is loaded in full into every session.
When invoked 203 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00203 $0.00203
Opus 5.5 $0.00081 $0.00081
Sonnet 5.5 $0.00041 $0.00041
Haiku 4.5 $0.00020 $0.00020

Measured 2mo ago against content hash b4e510541a5f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

tiny-agent-sandbox 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 · 25 lines

What it actually says

Agent Guide

Purpose

This repository is a small educational sandbox that exposes bounded code execution through MCP.

Security invariants

  • Never accept arbitrary images, commands, Docker flags, environment variables, or host mounts from a tool caller.
  • Keep network disabled by default.
  • Keep the root filesystem read-only, run as a non-root user, and drop all Linux capabilities.
  • Bound input, output, time, memory, CPU, and process count.
  • On timeout or output overflow, remove the named container instead of only killing the Docker client.
  • Describe this project as a development/learning boundary, not a production multi-tenant sandbox.

Validation

uv sync --no-editable --extra dev
uv run --no-editable ruff check .
uv run --no-editable pytest -m "not integration"
docker pull python:3.12-alpine node:22-alpine alpine:3.22
uv run --no-editable pytest -m integration
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. 2mo ago First seen · 25 lines · 203 tokens per session scan A b4e510541a5f

Subscribe to this mod's changes

tiny-agent-sandbox AGENTS.md is an instructions file published in the GitHub repository wesleyzhangwq/tiny-agent-sandbox (0 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 203 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 2026-08-31.

Related

tiny-agent-sandbox AGENTS.md compared with instructions from other repositories

tiny-agent-sandbox AGENTS.md next to 6 instructions from other repositories
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tiny-agent-sandbox AGENTS.mdwesleyzhangwq/tiny-agent-sandboxInstructions file03mo agoApache-2.0A203Codex, OpenCode
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next.js AGENTS.mdvercel/next.jsInstructions file143kyesterdayMITA7,461Codex, OpenCode
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vscode oss-third-party-notices.instructions.mdmicrosoft/vscodeInstructions file195kyesterdayMITA5,516GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscodeInstructions file195kyesterdayMITA3,093GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harnessInstructions file274k2d agoMITA4,313Codex, OpenCode