How To Use Openai Codex, A Complete 2025 Workflow

You can feel it the moment you stop wrestling your editor and start shipping again. Openai Codex turns that switch for a lot of developers, not through magic, through a clean workflow that starts in your terminal, continues in your IDE, and scales into the cloud when you need more muscle. If you came here to learn how to use Openai Codex fast, you’re in the right place. We’ll get you from zero to productive, then we’ll push into the deeper features that separate casual prompts from real software work.

Openai Codex is not a single button. It’s a system that reads, edits, runs, and reasons about code across surfaces. You sign in once, then move between local and cloud work without losing state. If that sounds like the missing piece in your toolbelt, let’s set it up and put it to work.

1. What Is Openai Codex In 2025

Openai Codex is a coding agent that can read your repository, make focused edits, run commands, and open pull requests. It meets you where you work: the terminal, the IDE, the web interface, GitHub, and even the ChatGPT iOS app. Think of it as one brain that follows you, not three different tools you have to juggle.

If you want the short version of what is Openai Codex, here it is. It is a context-aware coding partner that understands your project structure, proposes changes as diffs, runs checks, and iterates until the task completes. When people search for “what is Oopenai codex,” they’re usually trying to confirm if it’s a model, a plugin, or a cloud agent. It’s all three, connected by your account.

2. Getting Access And Openai Codex Pricing

You can use Openai Codex on paid ChatGPT plans, Plus, Pro, Team, Edu, and Enterprise. Local and cloud tasks both draw from your allowance, and the allowance depends on your plan and the complexity of the work. Smaller scripts use less. Multi-file refactors and long sessions use more. If you outgrow your plan’s cadence, you can switch the local tools to API-key billing and keep going.

2.1 Plan Snapshot

If you plan to run long local sessions on Openai Codex CLI and you hit caps, set an API key and pay as you go for those local runs. That way, your Openai Codex pricing stays predictable for the team, while you maintain momentum on the machine in front of you.

3. Quickstart, Setup, And Your First Run

You have three ways to begin, and they play nicely together.

1. Cloud agent. Create or connect a GitHub repo. Launch tasks from the web. Review diffs, iterate, and open PRs.
2. IDE. Install the Codex IDE extension, sign in, and work against the files you have open.
3. CLI. Install Openai Codex CLI, authenticate, and operate inside your repository from the terminal.

A simple first task demonstrates the flow. Ask Openai Codex to add a feature flag to a small service. It will scan the project, propose a plan, edit guarded code paths, run the tests you already have, and show a diff. You accept or iterate, then open a PR. That’s the baseline rhythm you’ll use every day.

4. Using An API Key When You Need More Headroom

Openai Codex works great with your ChatGPT login. If you need more local capacity, switch the local tools to API billing.

1. Grab an API key from your OpenAI dashboard.
2. Set it globally, for example in your shell profile.
3. Point the tools at the key.

CLI configuration looks like this:

# ~/.codex/config.toml

preferred_auth_method = "apikey"

For a one-off run:

codex --config preferred_auth_method="apikey"

To return to account login:

codex --config preferred_auth_method="chatgpt"

The IDE offers the same choice on sign-in. Pick your path, then get back to work.

5. Openai Codex CLI, A Power User’s Companion

Openai Codex CLI is the fast lane. It reads files, edits precisely, and runs commands inside your repo. It shines for scaffolding, refactors, and scripted tasks.

5.1 Install And Authenticate

• macOS or Linux with npm:

npm install -g @openai/codex

• macOS with Homebrew:

brew install codex

• Windows is experimental today. Use WSL for the best experience.

Then run:

codex

You’ll sign in with ChatGPT or the API key method you configured. Once you see the prompt, you’re in.

5.2 Your First Useful Commands

• Refactor a module:

codex "Refactor src/auth/token.ts to isolate JWT signing and verification. Keep tests green."

• Add a health endpoint:

codex "Add GET /health to the FastAPI app, return {status:'ok'} and wire to router."

• Generate tests:

codex "Create unit tests for utils/date.ts. Aim for edge cases around timezones."

5.3 Approval Modes And Safety

You control how much autonomy Openai Codex has on your machine.

• Chat mode reads context and drafts changes, you apply.
• Agent mode reads, edits, and runs commands in the working directory with approvals for sensitive steps.
• Agent, Full Access skips many prompts, use this wisely. Keep changes in a feature branch.

Make small commits, checkpoint often. Review diffs like you would from a teammate.

5.4 Reasoning Effort

Openai Codex lets you nudge how hard it thinks. Low reasoning effort returns quickly. High reasoning effort spends more time to reason through complex changes. Use higher effort for multi-file edits, migrations, and thorny bug hunts.

5.5 Session Habits That Save Time

• Start with a crisp brief. “Add optimistic UI for cart updates, tests included,” works better than a vague goal.
• Provide a plan file for bigger work. Ask Openai Codex to propose plan.md, review it, then run.
• Keep scripts discoverable. Codex will call make test if it finds a Makefile, so name scripts clearly.
• Split work into parallelizable tasks. The CLI and cloud agent both benefit from smaller units.

6. Codex IDE Extension In Practice

The codex ide extension brings the agent into your editor. It reads selected files, proposes edits as a preview, and lets you apply them with a click.

6.1 Install And Sign In

You can install for Visual Studio Code, Cursor, Windsurf, and VS Code Insiders. After install, sign in with your ChatGPT account, or switch to an API key if you prefer that path. On Windows, restart the editor if the panel doesn’t appear. On Cursor, pin the panel so it stays in view.

6.2 Edit With Confidence

Open a file, select the relevant block, then ask directly. “Find the off-by-one in paginate() and fix the unit test” is enough context when the file is open. The codex ide extension tracks the working directory and shows a diff before changes land. You can undo from the editor, though you should still commit before and after each task.

6.3 Approval Modes And Reasoning, Right In The Panel

Use Chat for drafting and reviews. Use Agent to read, edit, and run commands in the project. Turn up reasoning when the task spans multiple files or subtle cross-module contracts. Keep it lower for quick edits and doc updates.

6.4 Referencing Files

You can direct Openai Codex at specific files without pasting paths.

Use @server/routes.ts to add a new route for /resources built from @server/data/resources.ts

The result is focused and repeatable.

7. Delegating To The Cloud And GitHub

Some tasks deserve more compute and isolation. Send those to the cloud agent. Connect your GitHub repo in the web interface, launch a task, and watch logs as it works. When a change is ready, you’ll see diffs and a PR you can review like any teammate’s work.

Openai Codex can also review your pull requests. Mention the agent on a PR, ask for a targeted review, and it will analyze the diff, run checks you’ve configured, and propose improvements. Many teams treat this as a strong first pass before human review.

8. A Simple, Repeatable Multi-Surface Workflow

A lot of developers follow a predictable rhythm.

1. Use Openai Codex CLI to spike a feature branch, scaffold folders, and write the first pass.
2. Switch to the IDE to polish, tighten typings, and adjust UX details with the codex ide extension.
3. Delegate larger or independent tasks to the cloud. Let the agent run tests and open PRs.
4. Review, iterate, and merge.
5. Repeat, with more parallel tasks once the repo has clean script entry points.

This workflow keeps you in control while letting Openai Codex lift the heavy parts.

9. Repository Hygiene That Makes Codex Shine

Openai Codex respects clarity. Give it structure and it rewards you with speed and accuracy.

• Name scripts consistently. npm test, npm run lint, and npm run e2e are easy to discover.
• Keep modules small and cohesive. Agents handle clear boundaries better than sprawling files.
• Add agents.md to document project conventions. Where to put new features, how to run services, and non-obvious rules.
• Use worktrees or feature branches to isolate parallel tasks.
• Write tests. Openai Codex gets stronger when it can run and trust them.

10. The Knobs That Matter When You Hit Limits

Every tool has limits. You can stretch Openai Codex far with a few simple adjustments.

• Raise reasoning when a task demands deeper analysis.
• Lower it for speed when you already know the approach.
• Split long tasks into steps. “Plan, then implement, then test” is faster than a giant monologue.
• Switch the CLI to API billing on heavy local days.
• Keep an eye on weekly cadence. Save cloud tasks for changes that benefit from isolation and logs.

11. Codex Vs Claude Code, A Pragmatic Comparison

Both tools can build real software. The choice depends on your priorities. Here’s a snapshot that reflects how many teams evaluate them today.

If you live in the terminal and want a single account to tie your day together, Openai Codex offers a clean path. If you prefer a mix of providers, you can still pair them. Many developers ask Openai Codex to implement, then ask another tool to review or benchmark. Use the combination that keeps you shipping.

12. Windows, WSL, And Environments

If you’re on Windows, run Openai Codex CLI from WSL for a smooth Unix-like environment. Inside containers, you can operate the CLI in your own images, or use the web agent’s managed environment. The IDE extension supports VS Code forks. JetBrains support is a common request. Keep an eye on the marketplace and official notes for any updates.

13. Troubleshooting That Actually Helps

• Authentication loop. Restart the IDE or clear the browser session used for sign-in, then try again.
• Missing diffs. Ensure the editor has write permissions in the repo and you’re on a branch.
• Long-running tasks. Raise reasoning, then break the task into two steps. Ask for a plan file first.
• Tests failing. Ask Openai Codex to run the test command you use locally, then to iterate only on failing specs.
• Session organization. Use clear branch names and commit often. The history becomes your best debugging tool.

14. Two Real-World Walkthroughs

14.1 From Bug To Green Tests In Minutes

• In the IDE, select the broken paginate() function.
• Ask the codex ide extension to find and fix the off-by-one, write one new test, and update the snapshot.
• Review the diff, apply, and run npm test.
• If the suite reveals a second edge case, ask Openai Codex to handle that specific input and update the tests again.
• Commit and push.

The key here is brief, scope, and iteration. You stay in control while Openai Codex does the precise edits.

14.2 From Idea To PR Through The Cloud

• In the web interface, connect the repo and start a task. “Add a /health endpoint, wire to router, add a simple check to CI.”
• Watch logs. When done, review diffs and open a PR.
• Ask Openai Codex to review the PR with a focus on security or performance.
• Pull the branch locally, run your end-to-end checks, and merge.

Once you trust the rhythm, you can queue a few tasks at a time and keep your day moving.

15. The Mental Model That Keeps You Productive

Treat Openai Codex like a smart teammate who thrives on clarity. Tell it what success looks like. Show it where scripts live. Give it a plan for large changes. Ask it to check itself with your tests. Keep edits scoped, iterate quickly, and use the cloud when local work would block your flow.

You’ll notice something after a few days. Your codebase gets cleaner. Your scripts get sharper. The agent gets faster because your repository reads like a map. That’s not an accident. It’s the result of steady, thoughtful habits that compound.

16. Keep Your Momentum, Starting Today

Install the tools, sign in, and ship a small improvement before you close this tab. Add one endpoint. Tighten a flaky test. Document a convention in agents.md. Use the CLI to spike, the codex ide extension to polish, and the cloud to scale your effort. If you need more local capacity, switch Openai Codex CLI to API billing and keep going.

You’re here to build. Openai Codex gives you leverage, not ceremony. Set your workflow once, then let it carry you through the dull parts while you focus on the ideas that matter.

Call to action
Start now. Install Openai Codex CLI, add the Codex IDE extension, connect your repo, and complete one task. Repeat tomorrow. You’ll ship more this week than last, and you’ll do it with a calmer brain and a cleaner codebase.