Constellation · The Forge

Codex: OpenAI's coding agent, decoded

Sixteen guides to working with Codex: AGENTS.md, prompting, harness configuration, loop engineering, the full CLI, MCP, cloud and CI automation, the SDK and subagents, code review across every surface, the extension ecosystem, TUI personalization, and an honest comparison with Claude Code.

16 of 16 guides live · fact-checked against official docs

Chapter 0

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Codex 101

Understand Codex across the CLI, IDE, ChatGPT desktop app, and cloud — then get running.

8 minbasics / install / codex

Chapter 1

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AGENTS.md

Write the instruction file Codex actually follows — and nest it right.

10 minagents.md / configuration / memory

Chapter 2

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Prompting

Frame tasks so Codex plans, implements, and verifies the way you want.

9 minprompting / patterns / templates

Chapter 3

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Playbook

Apply OpenAI's own best practices — context, planning, review, MCP.

9 minbest practices / workflow / codex

Chapter 4

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CLI Config

Configure approvals, sandboxing, profiles, and MCP — once, correctly.

10 mincli / configuration / security

Chapter 5

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The Bridge

Know which agent fits which job — and how to run both in one repo.

11 mincomparison / claude / codex

Chapter 6

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CLI Reference

Drive Codex from the terminal with the core subcommands, flags, and slash commands.

11 mincli / reference / codex

Chapter 7

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Cloud & CI

Delegate to isolated cloud containers, review the diffs, and wire Codex into GitHub and CI.

11 mincloud / ci / automation

Chapter 8

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Codex MCP

Connect Codex to your tools the right way — stdio vs HTTP, OAuth, per-tool approval, and Codex-as-server.

10 minmcp / integrations / codex

Chapter 9

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SDK & Subagents

Drive Codex from TypeScript or Python and fan tasks out to parallel sub-agents.

11 minsdk / subagents / codex

Chapter 10

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Surfaces

Pick the right Codex surface — and use the IDE, app, and web features most people miss.

8 minsurfaces / ide / codex

Chapter 11

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Extensions

Codex’s extension ecosystem — apps, plugins, hooks, memories, and experimental flags — installed, scoped, and managed.

8 minextensions / plugins / codex

Chapter 12

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TUI Tuning

Turn Codex’s catalogued-but-unexplained UI commands into real habits — personality, themes, Vim, keymaps, and the fast lane.

7 mininterface / customization / codex

Chapter 13

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Code Review

Make Codex review every pull request and only surface the issues that matter.

11 mincodex / code-review / github / ci / agents-md / automation

Chapter 14

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Loop Engineering

Use /goal, automations, AGENTS.md, skills, subagents, and review gates as one control system.

21 minloop engineering / goal / automations / agents.md / subagents

Chapter 15

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Harness Config

Build a repeatable Codex harness with AGENTS.md, config.toml, skills, MCP, approvals, sandboxing, goals, and validation.

18 minharness engineering / configuration / codex / agents.md / sandboxing