OpenAI Codex App: Run Multiple AI Coding Agents in Parallel (2026 Guide)
OpenAI just dropped the Codex app for macOS - a desktop app that lets you run multiple AI coding agents simultaneously, each working on different tasks in your codebase. Think of it as a "command center for AI developers." Here's everything founders need to know.
What is the Codex App?
The Codex app is OpenAI's new macOS application for agentic coding - AI that doesn't just suggest code, but actively builds, tests, and debugs it. Unlike ChatGPT or Copilot where you prompt and wait, Codex agents run autonomously for up to 30 minutes, returning completed code when done.
The key innovation: parallelism. You can spin up multiple agents working on different parts of your codebase simultaneously - one fixing bugs, another writing tests, another implementing a new feature - all without context switching.
The Big Idea
Codex transforms AI coding from "chat with an assistant" to "manage a team of AI developers." Each agent gets its own thread, worktree, and can work independently while you review and merge their output.
Key Features
Multi-Agent Threads
Run agents in separate threads organized by project. Switch between tasks without losing context. Each agent maintains its own state.
Git Worktree Support
Multiple agents can work on the same repo without conflicts. Each operates on an isolated copy, preventing merge disasters.
Built-in Code Review
Review agent changes inline, comment on diffs, and open in your editor for manual tweaks before accepting.
Integrated Terminal
Open a terminal per thread to test changes, run dev servers, or execute custom commands alongside agent work.
Skills: The Power-Up System
Skills are pre-built capabilities that extend what Codex agents can do. They bundle instructions, resources, and scripts so agents can reliably connect to external tools and complete complex workflows.
Available Skills Library
| Skill | What It Does | Use Case |
|---|---|---|
| Figma | Fetch design context from Figma files | Design-to-code workflows |
| Linear | Manage projects and issues in Linear | Issue triage and updates |
| Vercel | Deploy web apps to Vercel | Automated deployments |
| Cloudflare | Deploy to Cloudflare Pages/Workers | Edge deployments |
| GPT Image | Generate images using DALL-E | Asset creation in code |
| Documents | Create PDFs, spreadsheets, Word docs | Report generation |
MCP Integration
Codex supports the Model Context Protocol (MCP), so you can connect agents to additional services beyond the built-in skills. This is huge for custom enterprise workflows.
Automations: AI That Works While You Sleep
Automations let you schedule agents to run tasks in the background on a recurring basis. Results appear in a review queue for human approval when you return.
Example Automations
- CI Failure Summarizer - Automatically analyze and summarize CI failures every morning
- Issue Triager - Review new GitHub issues and suggest priorities/assignments
- Dependency Updater - Check for security updates and prepare PRs weekly
- Code Quality Scanner - Run nightly analysis and flag potential issues
- Documentation Keeper - Update docs when code changes are detected
# Example: Automation config for daily CI summaries { "name": "Daily CI Summary", "schedule": "0 8 * * *", // 8am daily "instructions": "Check CI failures from the last 24 hours, summarize root causes, and suggest fixes", "skills": ["github", "linear"] }
Agent Personalities
A unique feature: you can select different "personalities" for your Codex agents depending on your working style:
- Pragmatic - Focus on getting things done, minimal explanation
- Thorough - Detailed explanations and comprehensive solutions
- Empathetic - More conversational, considers context and feelings
- Concise - Minimum viable communication, maximum efficiency
What Powers Codex Under the Hood
The Codex app is powered by specialized models optimized for coding:
- GPT-5.2-Codex - Fine-tuned version of GPT-5.2 for complex coding and agent behaviors (desktop app)
- codex-1 - Custom version of OpenAI's o3 model for cloud/web interface
These models are specifically trained on software engineering tasks, repo-level understanding, and multi-step reasoning required for autonomous code generation.
How to Get Started
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1
Download the App Visit openai.com/codex and download the macOS app (Apple Silicon required)
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2
Sign In Log in with your ChatGPT account or OpenAI API key
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3
Connect Your Repo Point Codex at your local repository to give it context
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4
Create a Thread Start a new thread and give your first task to an agent
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5
Review & Merge Review the agent's work, provide feedback, and merge approved changes
Pricing & Availability
Current Pricing (February 2026)
- ChatGPT Free & Go users: Limited-time free access to celebrate launch
- ChatGPT Plus ($20/mo): Full access + 2x rate limits during launch
- ChatGPT Pro ($200/mo): Full access + 2x rate limits + priority
- Business/Enterprise: Full access + team features + 2x rate limits
- API users: Pay per token usage
The free access for Free/Go users is temporary - OpenAI hasn't announced when it ends, so try it now if you're curious.
Codex App vs CLI vs IDE Extension
Codex is available in multiple forms. Here's when to use each:
| Interface | Best For | Key Advantage |
|---|---|---|
| Codex App (macOS) | Managing multiple parallel agents | Visual multi-threading, Automations |
| Codex CLI | Terminal-native developers | Pipeline integration, scripting |
| IDE Extension | In-editor assistance | Context-aware suggestions while coding |
| Web Interface | Quick tasks, mobile access | No installation required |
Session history and configuration sync across all interfaces, so you can start on web and continue in the app.
Use Cases for Founders
Parallel Feature Development
Have one agent build the frontend while another implements the API. Review both PRs and merge together.
Test Coverage Sprints
Spin up agents to write tests for different modules simultaneously. Go from 40% to 80% coverage in a day.
Bug Squashing
Feed a list of bugs to separate agents. Each investigates and proposes fixes. You review and merge.
Migration Projects
Parallelize boring migrations (React class to hooks, Python 2 to 3, etc.) across your codebase.
Limitations to Know
- macOS only (for now) - Windows and Linux support not announced
- Apple Silicon required - Won't run on Intel Macs
- 30-minute agent limit - Complex tasks may need to be broken up
- Not magic - Agents still make mistakes; human review is essential
- Rate limits apply - Even with 2x boost, heavy parallel use can hit limits
The Bigger Picture
Codex represents OpenAI's vision for the future of software development: humans as reviewers and architects rather than line-by-line coders. The shift is from:
"I write code with AI assistance" to "I manage AI agents that write code"
Whether this excites or concerns you probably depends on your role. For founders, it's clearly an opportunity - the ability to multiply your development capacity without hiring is a significant advantage.
Getting the Most Out of Codex
Pro Tips
- Start small - Give agents well-scoped tasks before complex ones
- Use worktrees - Don't let agents work on your main branch directly
- Review carefully - Agents can introduce subtle bugs; test everything
- Build skills - Create custom skills for your team's recurring workflows
- Set up Automations - Let agents handle routine tasks overnight
Bottom Line
The Codex app is OpenAI's most ambitious developer tool yet. The ability to run multiple AI agents in parallel, combined with Skills and Automations, makes it more than just another coding assistant - it's the beginning of AI-managed development workflows.
For founders building with small teams, this could be a force multiplier. The free launch period makes it risk-free to explore. Download it, run a few parallel agents, and see if it fits your workflow.
The future of coding isn't writing more code faster. It's managing AI that writes code for you.
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