implement-codex

Implement approved multi-phase software plans by running Codex in a writable sandbox with Claude verification.

Updated Aug 27, 2026
One-click install
npx skills add https://github.com/KMakayee/playbook --skill implement-codex
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: implement-codex
Source: https://github.com/KMakayee/playbook/tree/main/.claude/skills/implement-codex
Command: npx skills add https://github.com/KMakayee/playbook --skill implement-codex

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

It helps you implement an already-approved plan by having Codex generate code changes phase-by-phase in a sandbox while Claude verifies that each phase stays aligned with the plan and produces coherent, expected outputs.

Core Features & Use Cases

  • Phase-by-phase implementation: Executes each unchecked phase in tasks/plan.md with a controlled workflow that captures baselines, runs Codex, and evaluates results.
  • Tight plan adherence via contracts: Uses explicit mismatch and blocked contracts to prevent Codex from editing when the plan premise is wrong or when the phase needs capabilities like network access.
  • Robust verification gates: Enforces output schema checks, parses Codex JSON logs, detects verification-command violations, cross-checks diff scope, and updates phase checkmarks and metrics.
  • Recovery and escalation: Supports mismatch re-research, blocked-state Claude takeover, and crash diagnosis with either manual escalation or a limited retry path.

Quick Start

Run implement-codex after you have a finalized tasks/plan.md and the required tasks/research-codebase.md in place, so each phase can be implemented with Codex and verified against the plan.

Frequently Asked Questions about implement-codex

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I implement a multi-phase coding plan with Codex and verify the diffs?▼

To implement a multi-phase coding plan with Codex, execute unchecked phases in a writable sandbox while a separate verifier checks JSON logs, validates output schemas, and cross-checks diff scope to ensure strict surgical edits.

What is needed to start automated code implementation using a sandboxed agent workflow?▼

Automated code implementation requires a finalized tasks/plan.md defining phase structure, plus tasks/research-codebase.md and tasks/design-decision.md citing relevant files and outlining success criteria before execution begins.

How do agent workflows handle plan adherence when Codex makes unexpected code changes?▼

Agent workflows enforce plan adherence by applying mismatch and blocked contracts that prevent Codex from editing when the plan premise is wrong, triggering a re-research phase or a manual escalation path instead.

Can I use network access or custom test commands during sandboxed code generation?▼

Sandboxed code generation applies strict network and test-command constraints, blocking execution if a phase requires capabilities like network access and detecting verification-command violations to maintain diff scope integrity.

What happens when Codex crashes or produces invalid JSON output during phase implementation?▼

When Codex crashes or outputs invalid JSON, the workflow supports crash diagnosis with either manual escalation or a limited retry path, while a blocked-state allows a verifier takeover to recover the phase.

Does implement-codex work for updating metrics and checkmarks after each coding phase?▼

Yes, implement-codex updates phase-level metrics and checkmarks in tasks/plan.md after verifying output schemas and cross-checking real-diff scope against the approved plan's success criteria.