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.
npx agentmods add instructions/boldblackai/harness/agents-mdgit clone --depth 1 https://github.com/boldblackai/harnessWhat 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 | $0.03641 | $0.03641 |
| Opus 5 | $0.01820 | $0.01820 |
| Sonnet 5 | $0.00728 | $0.00728 |
| Haiku 4.5 | $0.00364 | $0.00364 |
Grade A, and why
harness 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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.
harness
Project Overview
Harness is a portable containerized environment for running coding agents. See README.md for more project details.
Documentation website: Built with Zensical from docs/. Config in zensical.toml. Deploys to GitHub Pages via .github/workflows/docs.yml, which also runs a build-only check on PRs that touch docs/, zensical.toml, or the workflow itself (so doc build failures are caught before merge). Build locally with pip install zensical && zensical build --clean (CI uses uv tool install zensical==0.0.43).
Commands
pnpm build # Compile TypeScript → bin/harness.js
make build # Same via Makefile
make image # Build all Docker images (base + opencode + hermes variants)
make image-base # Build base image only
make image-opencode # Build opencode variant
make image-hermes # Build hermes variant
pnpm link --global # Make `harness` CLI available globally for local testing
pnpm lint # Run all linters (biome, markdownlint, shellcheck, hadolint, actionlint)
pnpm format # Auto-format with Biome
pnpm test:e2e # Run e2e CLI tests (uses a docker shim, no real docker needed)
System linters (shellcheck, hadolint, actionlint) must be installed separately (brew install shellcheck hadolint actionlint).
Architecture
All CLI logic lives in src/harness.ts (compiles to bin/harness.js). It:
- Parses CLI args via
minimist - Selects an adapter (
PiAdapter,OpenCodeAdapter, orHermesAdapter) based on--agentflag - Constructs and spawns a
<runtime> runcommand (dockerby default, or Apple'scontainerwhenHARNESS_CONTAINER_RUNTIME=apple) that mounts$PWDand passes the prompt via stdin or-e
Adapter pattern: Each adapter implements how to invoke the agent binary inside the container (command, flags, env vars). Adding a new agent means adding a new adapter class and registering it in the ADAPTERS map.
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.
- 2d ago First seen · 131 lines · 3,641 tokens per session scan A f7db8e04d30d
harness AGENTS.md is an instructions file published in the GitHub repository boldblackai/harness (10 stars, last pushed 3d ago), licensed MIT. It adds 3,641 tokens to every session, about $0.0182 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.