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rubber-duck: Instructions file for Codex

AGENTS.md

rubber-duck AGENTS.md is an instructions file for Codex, OpenCode from sprngr/rubber-duck. It costs 1,513 tokens per session, scanned A, original, MIT.

Repository instructions for Rubber Duck, a Socratic AI assistant project focused on evidence-based decisions and carefully limited changes.

In plain words
What is it for?
Use them when developing Rubber Duck, verifying generated artifacts, running validation, or installing it for a supported coding client.
Why use it?
They explain the project layout and the commands for building, checking, validating, and installing its generated files.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md. Also seen: mentions AGENTS.md; mentions OpenCode.

This is sprngr/rubber-duck's own configuration. It tells Codex and OpenCode how to work on rubber-duck 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 rubber-duck configures →

not rated 8repo 16d ago A scan 1,513 tokens original MIT
View source ↗ sprngr/rubber-duck
Reuse

Borrowing it

Nothing to install: this file belongs to sprngr/rubber-duck. 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/sprngr/rubber-duck/main/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/sprngr/rubber-duck

Made for: Codex, OpenCode.

Wrote this? Show the measurements

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README.md
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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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Per session 1,513 This file is loaded in full into every session.
When invoked 1,513 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 $0.01513 $0.01513
Opus 5.5 $0.00605 $0.00605
Sonnet 5.5 $0.00303 $0.00303
Haiku 4.5 $0.00151 $0.00151

Measured 1mo ago against content hash a5e36795042d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

rubber-duck 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 1mo 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 · 156 lines

How it starts

The opening of the file, as written. The whole thing — 156 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

What this is

Rubber Duck is a Socratic AI assistant project. It focuses on decision quality, evidence-first reasoning, and bounded safe changes.
This repository contains source prompts, assembled skills, generated harness artifacts, installers, validation fixtures, and policy docs.

Quick Start (5 minutes)

  1. Verify tools: bash, pwsh, python3, node/npx, jq, make
  2. Build generated artifacts:
    • make build
  3. Verify generated artifacts are clean:
    • make check
  4. Run validation suite:
    • make validation
  5. Install locally (example):
    • Bash: ./scripts/rubber-duck.sh install --opencode
    • PowerShell: ./scripts/rubber-duck.ps1 install -OpenCode

Layout

  • src/ - source-of-truth for agents, skills, and shared snippets
    • src/install/scripts/ - sync wrapper templates
    • src/install/templates/ - manifest template
  • skills/ - built skill artifacts generated from src/skills/*
  • dist/ - built harness artifacts generated from src/agents/*
    • dist/scripts/ - generated sync wrapper scripts
    • dist/templates/ - generated manifest template
  • scripts/ - build, check, and installer scripts (rubber-duck.sh, rubber-duck.ps1)
  • docs/ - architecture and supporting documentation
  • validation/ - prompt validation suite, fixtures, and runner
  • tests/ - fixture-style behavior tests and expected outputs
  • .github/ - tracked CI/workflow config
  • .agents/, .claude/, .opencode/ - local harness install targets (untracked, populated by installers)
  • build/ - assembly/check rules

Tooling and Runtimes

  • Bash (Linux/macOS/CI script runtime)
  • PowerShell (pwsh) for Windows installer runtime
  • Python 3 (validation runner and build checks)
  • Node.js + npx (skills CLI install/remove/list flows)
  • jq (required for harness artifact build rendering)
  • make (task entrypoints for build/check workflows)

Commands & Scripts

  • Build everything:
    • make build
  • Verify generated artifacts + guardrails drift:
    • make check
  • Build/check skills only:
    • make build-skills
    • make check-skills
  • Build/check harness artifacts only:
    • make build-harness
    • make check-harness
  • Run validation suite:
    • make validation
    • or python3 validation/run-validation-tests.py
  • Installers:
    • Bash: ./scripts/rubber-duck.sh install --opencode
    • PowerShell: ./scripts/rubber-duck.ps1 install -OpenCode

Read the full file on GitHub · 156 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. 1mo ago First seen · 156 lines · 1,513 tokens per session scan A a5e36795042d

Subscribe to this mod's changes

rubber-duck AGENTS.md is an instructions file published in the GitHub repository sprngr/rubber-duck (8 stars, last pushed 16d ago), licensed MIT. It adds 1,513 tokens to every session, about $0.0061 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.

Claude Codeagent-skillsai-agentsantivibedecision-qualitydeveloper-tools
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