20 Real-World Codex Scenarios

Your sprint backlog has nine tickets, three of them are blockers, and your team lead just asked if anyone can “quickly” audit the auth module for security issues. You could context-switch all day and finish two of those tickets. Or you could open the Codex App, spin up parallel worktrees, and let agents work on four of them simultaneously while you focus on the architecture that actually needs a human brain.

These 20 lessons are built from real development workflows where Codex’s multi-surface approach — App, CLI, IDE extension, cloud, GitHub, Slack, and Linear — changes how you decompose and parallelize work.

What You’ll Walk Away With

• A multi-surface development workflow that runs tasks in parallel across isolated worktrees
• Copy-paste prompts for every phase of the development lifecycle, tuned for Codex’s unique capabilities
• Patterns for delegating work through GitHub comments, Slack messages, and Linear issues
• Automation recipes that run overnight — code reviews, dependency updates, and bug hunts on schedule

Foundation: From Zero to Shipping

Start here. These four lessons take you from an empty repository to production-ready code, using the Codex surfaces that match each task best.

Starting Projects

Bootstrap full-stack projects in the Codex App. Set up AGENTS.md, configure local environments, and scaffold your codebase from a single thread. Start Building

Codebase Analysis

Onboard to a large monorepo without reading every file. Use Codex across surfaces to map architecture, trace data flows, and understand unfamiliar code. Explore Codebases

Feature Development

Build features with parallel agents in separate worktrees. Plan locally, delegate implementation to cloud tasks, and merge results back into your branch. Build Features

Bug Hunting

Debug across the Codex App, CLI, and cloud. Reproduce locally, delegate deep investigation to cloud tasks, and tag @codex on GitHub issues to fix CI failures. Fix Bugs

Daily Development: The Workflows You’ll Use Every Day

These are the bread-and-butter patterns. The workflows you reach for at 10 AM and again at 4 PM.

Testing

Generate test suites that match your existing patterns. Run tests in worktrees so the agent does not interfere with your working directory. Write Tests

Refactoring

Large-scale refactoring across hundreds of files using worktrees for isolation. Plan locally, execute in parallel, and sync results safely. Refactor Code

Code Review

AI-powered code review with /review in the CLI and App, plus @codex review on GitHub pull requests for automatic review comments. Review Code

Documentation

Generate API docs, architecture diagrams, and README files from your codebase. Set up automations to keep docs current on a schedule. Document Code

Backend Development: APIs, Databases, and Infrastructure

Server-side workflows where Codex’s cloud execution and parallel agents shine.

API Development

Scaffold REST and GraphQL endpoints with validation, auth middleware, and error handling. Test endpoints in the CLI without leaving Codex’s session. Build APIs

Database Work

Design schemas, generate migrations, write complex queries, and seed test data. Delegate migration testing to cloud environments with real databases. Work with Data

Deployment

Automate deployment workflows from Dockerfiles to production. Use cloud tasks and the Codex GitHub Action to validate deployments in CI. Deploy Apps

Security Audit

Scan for vulnerabilities, audit dependencies, and generate security reports. Schedule daily security sweeps with automations. Secure Code

Advanced: Performance, CI/CD, and Scale

For the senior engineers who want to push Codex to its limits across every surface.

Performance

Profile bottlenecks, optimize database queries, and benchmark changes. Use cloud tasks with best-of-N attempts to explore optimization strategies. Optimize Performance

CI/CD Pipelines

Run Codex in GitHub Actions with the official codex-action. Automate code review, test generation, and quality gates on every pull request. Configure Pipelines

PR Automation

Automate the entire pull request lifecycle from creation through review to merge. Tag @codex to fix CI failures and request reviews directly on GitHub. Automate PRs

Parallel Development

Run multiple agents simultaneously in separate worktrees. Coordinate work across agents to ship an entire feature set in hours instead of days. Go Parallel

Automation and Integration: Multiply Your Output

Stop doing things twice. These lessons turn manual workflows into scheduled, repeatable automation across your entire toolchain.

Codebase Modernization

Migrate legacy code at scale using cloud tasks with multiple attempts. Modernize frameworks, upgrade dependencies, and refactor patterns systematically. Modernize Code

Slack and Linear

Delegate coding tasks from Slack channels and Linear issues. Mention @Codex where your team already works and get pull requests back. Integrate Services

Scheduled Automation

Set up recurring automations for daily code reviews, weekly dependency updates, and nightly bug hunts. Combine automations with skills for complex workflows. Automate Tasks

System Architecture

Use Codex for architectural decisions. Plan in the IDE, validate with cloud tasks, and iterate across surfaces until the design is right. Design Systems

How to Get the Most from These Lessons

Note

Every lesson follows the same structure: a real problem you recognize, the Codex workflow that solves it, copy-paste prompts you can use immediately, and the failure modes you need to watch for. Read them in order for a complete learning path, or jump to whichever one matches the problem on your screen right now.

If you are new to Codex

Start with Starting Projects to get comfortable with the App, worktrees, and thread modes. Then move through Codebase Analysis, Feature Development, and Bug Hunting in order. By the end of those four, you will have a workflow that covers most daily development tasks across multiple Codex surfaces.

If you are already using Codex

Jump to the lesson that matches your current bottleneck. Most experienced users find the biggest wins in Parallel Development (multi-agent worktree workflows), Scheduled Automation (set-it-and-forget-it recurring tasks), and PR Automation (GitHub integration patterns).

If you lead a team

Focus on CI/CD Pipelines and Slack and Linear for org-wide impact. The GitHub Action and integration patterns let you embed Codex into existing team workflows without requiring everyone to install the App or CLI.

Start with Project Setup Bootstrap your first project in the Codex App and learn the multi-surface workflow you will use every day