N Agentic Harnesses For Codex

Use this skill as a router for designing, building, and evaluating agentic harnesses.

Read only the files you need. Do not load the entire reference set unless the request genuinely spans multiple subsystems.

Default posture:

• Bias toward lean, solo-maintainable architecture.
• Start with a single-agent design unless clear constraints justify more.
• Require an evaluation plan even for greenfield builds.
• Prefer explicit system boundaries, permission policy, and workflow state over prompt cleverness.
• Translate ideas into implementation phases, success criteria, and failure tests.

Step 1: Classify The Request

Choose one mode before reading reference files.

design

Use when the user is creating a new harness, planning a major rebuild, or asking for architecture, MVP, or implementation sequencing.

Default reads:

• references/01-principles-and-solo-dev-defaults.md
• references/02-harness-shapes-and-architecture.md
• references/08-design-and-build-playbook.md

Add subsystem files only as needed.

evaluation

Use when the user already has a harness and wants gaps, risks, missing primitives, UX upgrades, or architectural cleanup.

Default reads:

• references/01-principles-and-solo-dev-defaults.md
• references/09-evaluation-and-improvement-playbook.md

Add subsystem files only for the parts under review.

design + evaluation

Use when the user wants a target architecture and a way to verify it, compare it with an existing system, or define acceptance criteria before building.

Default reads:

• references/01-principles-and-solo-dev-defaults.md
• references/02-harness-shapes-and-architecture.md
• references/08-design-and-build-playbook.md
• references/09-evaluation-and-improvement-playbook.md

Step 2: Classify The Product Shape

Determine the closest product shape before going deeper: