What is harness CLAUDE.md?

Repository instructions for harness, a library that gives several AI coding-agent command-line programs one shared interface. A monorepo is a single repository containing multiple related projects; here it contains Python and TypeScript versions kept in sync.

Use it when working on harness, reading its cross-language contract, checking adapter-specific behavior, running shared fixtures, or adding support for another command-line agent.

It explains the repository’s layout and the rules needed to keep both language versions behaving the same way. This reduces inconsistencies when adding or changing an adapter for a coding agent.

How twaldin/harness configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to twaldin/harness. 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/twaldin/harness/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/twaldin/harness

Made for: Claude Code.

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/twaldin/harness/claude-md/github.svg)](https://agentmods.dev/instructions/twaldin/harness/claude-md)

Your own site

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

Per session 2,116 This file is loaded in full into every session.

When invoked 2,116 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	$0.02116	$0.02116
Opus 5.5	$0.00846	$0.00846
Sonnet 5.5	$0.00423	$0.00423
Haiku 4.5	$0.00212	$0.00212

Measured 1mo ago against content hash e8326c124ed5, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

harness CLAUDE.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.

CLAUDE.md · 162 lines

How it starts

The opening of the file, as written. The whole thing — 162 lines — stays where its author put it; the contents beside it link to each section on GitHub.

harness

harness is a dual-language (Python + TypeScript) adapter library that wraps twenty-six AI coding-agent CLIs — claude-code, openclaude, opencode, codex, gemini, aider, amp, auggie, swe-agent, mini-swe-agent, qwen, continue-cli, pi, omp, factory-droid, kilo, crush, hermes, goose, cline, copilot, cursor, mistral-vibe, kimi-code, kiro, qoder — behind a shared RunSpec → RunResult contract. Both implementations sit in this monorepo. SPEC.md defines the shared contract and distinguishes shipped CLI behavior from future RPC/SDK implementation requirements.

Authoritative references in this repo:

SPEC.md — the cross-language contract. Public API, types, error rules.
ADAPTER-MATRIX.md — per-CLI flags, cost reporting, output shapes.
CONTRIBUTING.md — code conventions and the "add an adapter" guide.

Repository layout

harness/
├── SPEC.md                      cross-language contract (THE source of truth)
├── ADAPTER-MATRIX.md            per-adapter quirk reference
├── tests/fixtures/*.json        shared golden fixtures (Py + TS both consume)
├── src/harness/                 Python implementation (see src/harness/CLAUDE.md)
│   ├── base.py                  RunSpec / RunResult / Adapter dataclasses
│   ├── registry.py              run / list_adapters / get_adapter
│   ├── cli.py                   Typer CLI entrypoint (harness.cli:app)
│   ├── model_normalization.py   per-harness canonical model resolution
│   ├── pricing.py               cost derivation from token counts
│   ├── _subproc.py              subprocess runner
│   ├── _instructions.py         owned instruction projection lifecycle
│   └── adapters/                26 adapter modules, one per CLI
├── ts/                          TypeScript implementation (see ts/CLAUDE.md)
│   ├── package.json             @twaldin/harness-ts (Bun build + test)
│   ├── src/base.ts              mirror of Python base.py types
│   ├── src/registry.ts          mirror of Python registry.py
│   ├── src/model-normalization.ts
│   ├── src/pricing.ts
│   ├── src/subproc.ts
│   ├── src/instructions.ts      owned instruction projection lifecycle
│   ├── src/util.ts
│   └── src/adapters/            26 adapter modules, one per CLI
├── tests/                       pytest suite (Python)
└── ts/tests/                    bun test suite (TypeScript)

Read the full file on GitHub · 162 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.

1mo ago Changed · -13 tokens per session e8326c124ed5
1mo ago Changed a42f5e26c9c6
1mo ago Changed · +17 lines · +311 tokens per session 831a13047edc
2mo ago Changed · +9 lines · +114 tokens per session b265cb19e3d4
2mo ago First seen · 136 lines · 1,704 tokens per session scan A dd36d206e335

Subscribe to this mod's changes

harness CLAUDE.md is an instructions file published in the GitHub repository twaldin/harness (29 stars, last pushed 1mo ago), licensed MIT. It adds 2,116 tokens to every session, about $0.0085 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.

harness CLAUDE.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
harness CLAUDE.mdtwaldin/harness	Instructions file	29	1mo ago	MIT	A	2,116	Claude Code
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

harness: Instructions file for Claude Code