Agent Harness Engineering

Agent Harness Engineering

Use this skill when the goal is to make a repository easier for coding agents to understand, change, and maintain over time.

This skill turns the main ideas from OpenAI's harness-engineering article into a reusable project pattern:

• AGENTS.md stays short and acts as a router
• durable knowledge moves into docs/
• context is disclosed progressively instead of dumped all at once
• quality rules become mechanical checks instead of tribal knowledge
• optional garbage collection keeps agent-generated entropy under control

When to use it

Use this skill when the user asks to:

• create a reusable engineering skill for many repos
• bootstrap a repo for agent-first or AI-assisted development
• redesign AGENTS.md so it routes to structured docs
• add repo-readable architecture, spec, quality, reliability, or security docs
• add mechanical checks for doc freshness, structure, and agent guardrails
• add a low-friction cleanup loop for drift, stale docs, and code sprawl

Choose a rollout mode

Pick the least invasive mode that still improves the repo.

• overlay: Default for existing repos. Add docs/agent/ as an agent-readable overlay without rewriting existing docs.
• full: Use for greenfield repos or when the user explicitly wants a broader doc reorganization.

For most mature repos, start with overlay.

First-use workflow

When applying this pattern to a repo for the first time, do the following in order:

1. Inspect the repo's current AGENTS.md, docs/, CI, and lint/test commands.
2. Run the bundled bootstrap script in overlay or full mode.
3. Review the generated AGENTS.md block and adapt command names to the repo.
4. Keep existing project-specific instructions, but move durable detail from AGENTS.md into the generated docs.
5. Wire the generated validation script into the repo's native check flow.
6. If the repo moves fast or uses many agents, optionally enable garbage collection.

Bootstrap command

Run the bundled script from this skill directory:

python3 scripts/bootstrap_project.py --repo /path/to/repo --mode overlay

Optional flags:

• --mode overlay|full
• --with-gc to scaffold the garbage-collection report
• --dry-run to preview changes
• --force to overwrite generated files
• --no-claude-link to skip the CLAUDE.md -> AGENTS.md symlink

What the bootstrap adds

On first application, the scaffold normally creates or updates:

• AGENTS.md with a short agent-navigation block
• CLAUDE.md symlink to AGENTS.md unless disabled
• docs/agent/index.md
• docs/agent/architecture.md
• docs/agent/specs.md
• docs/agent/plans.md
• docs/agent/quality.md
• docs/agent/reliability.md
• docs/agent/security.md
• scripts/agent_repo_check.py
• optionally docs/agent/garbage-collection.md
• optionally scripts/agent_gc_report.py

Operating rules

1. AGENTS.md is a router

Do not turn AGENTS.md into a giant handbook.

• keep it short
• link outward to durable docs
• update links when docs move
• reserve AGENTS.md for task-routing instructions and repo-specific operational constraints

2. Durable knowledge lives in docs

Put medium- and long-lived repo knowledge in docs/agent/ or the repo's main docs tree.

Examples:

• architecture boundaries
• product or integration specs
• current plans
• quality gates and invariants
• reliability expectations
• security assumptions and trust boundaries

3. Progressive disclosure beats giant prompts

Only read the docs needed for the task.

• start at docs/agent/index.md
• open the relevant leaf docs
• avoid loading unrelated docs into context
• add new docs to the index so future agents can discover them quickly

4. Mechanical checks beat soft reminders

Prefer checks that can fail fast in CI or local validation:

• missing required docs
• missing frontmatter fields
• stale review dates
• docs not linked from the index
• AGENTS.md missing navigation links

5. Garbage collection is optional but useful

Enable the GC loop when the repo has high change velocity, many generated edits, or recurring drift.

The default GC report looks for:

• stale docs
• oversized files
• suspicious filenames like final-final or v2
• lingering TODO or FIXME clusters
• docs that are not linked from the index

References to read only when needed

• Read references/bootstrap-playbook.md when planning the first rollout for a repo.
• Read references/docs-blueprint.md when adapting the doc taxonomy or frontmatter.
• Read references/quality-gates.md when wiring checks into CI or repo-native tooling.
• Read references/garbage-collection.md when enabling scheduled cleanup or review loops.

Acceptance checklist

Before you finish a rollout, confirm:

• AGENTS.md routes to docs instead of duplicating them
• docs/agent/index.md points to every active leaf doc
• the generated docs have owners and last_reviewed dates
• scripts/agent_repo_check.py passes
• the repo's native check command includes the validation script or an equivalent wrapper
• garbage collection is either enabled intentionally or documented as deferred

Do not do this

• do not rewrite a mature doc system unless the user asks
• do not duplicate the same guidance in AGENTS.md and docs/agent/*
• do not add stack-specific CI assumptions without checking the repo
• do not enable automatic destructive cleanup; GC should surface candidates, not delete code blindly