# codex

Simon Willison finally defines Agentic Engineering after 11 hands-on chapters: using coding agents to help build software. The interesting part is why he needed the patterns first before the simple definition felt earned.

A guide to Codex best practices from prompting and planning to MCP, Skills, and Automations — building a more reliable agent workflow.

OpenClaw's ACP lets you spawn Codex, Claude Code, and Gemini from Discord/Telegram chat. Now with Telegram topic binding, persistent bindings that survive restarts, ACP Provenance for audit trails, and more. (Updated 2026-03-09)

Developer Kangwook Lee used just 2 API calls and 35 lines of Python to crack open Codex's hidden context compaction API via prompt injection — revealing the secret system prompts behind the encryption.

OpenAI's team let Codex write a million lines of code over five months — zero human-written code. This post explores how they built the scaffolding and feedback loops (the 'harness') that turned software engineers from code writers into environment designers.

Karpathy spent a weekend running 4 Claude + 4 Codex agents as an ML research team on GPUs. The result: agents are S-tier at implementation but F-tier at experiment design. His key insight — 'You are now programming an organization' — might define agentic engineering in 2026.

Indie hacker Elvis Sun uses an OpenClaw agent, Zoe, to orchestrate Codex and Claude Code agents: 50 commits per day, seven PRs in 30 minutes, three layers of AI review, and proactive Sentry bug fixes. Cost: $190/month.

Simon Willison launched Agentic Engineering Patterns, a playbook for coding agents like Claude Code and Codex. Lesson one: writing code got cheap, but good code remains expensive. Lesson two: red/green TDD is the six-word spell.

Peter Steinberger shares a high-scale PR triage workflow: run 50 Codex agents in parallel, emit structured JSON for every PR, then consolidate in one large-context session. Clean reports can beat premature vector database architecture.

Drexel/Missouri S&T analyzed 33,596 agent-authored GitHub PRs from 5 coding agents. Overall merge rate: 71%. Codex: 83%, Claude Code: 59%, Copilot: 43%. Rejection cause: no review. LeadDev warns PR flood is crushing monorepos/CI.

GitHub's Agent HQ now offers multi-agent support (Claude, Codex, Copilot) for Copilot Pro+ & Enterprise users. Run multiple AIs simultaneously in GitHub/VS Code to tackle problems from different angles. Outputs become Draft PRs. A paradigm shift for code review.

OpenAI released three primitives for long-running agents: Skills (reusable SKILL.md instruction packs), Shell (hosted container runtime), and Compaction (automatic context compression). Includes 10 battle-tested tips and Glean's production data.

Hook up Codex as an MCP server inside Claude Code with a single command. Why fight Codex CLI's rough edges when you can plug its brain into a better body?

OpenAI released GPT-5.3-Codex-Spark, its first model on Cerebras chips. It's incredibly fast (>1000 tokens/sec, 80% lower latency), but smaller, no auto-tests, Pro-only. This marks OpenAI's first production deployment on non-Nvidia hardware, redrawing the AI compute landscape.

Karel (OpenAI researcher) shares how he burns billions of Codex tokens: agents writing their own notes, crawling Slack, analyzing data, and generating 700+ hypotheses. He now talks to one agent that orchestrates everything else.

OpenAI co-founder Greg Brockman publicly reveals how OpenAI is transforming to agentic software development internally. By March 31st, agents should become the first resort for all technical tasks. Includes six concrete recommendations, including 'Say no to slop' on code quality.

Claude Code is a Templar — steady and reliable. Codex is a Glass Cannon Mage — explosive output but easy to blow up. Pick your quest, then pick your character.