> ## Documentation Index
> Fetch the complete documentation index at: https://docs.llmeasy.ru/llms.txt
> Use this file to discover all available pages before exploring further.

# What is Codex CLI?

> Understand what Codex CLI is, how it works, when to use it, and how it differs from Codex App and Codex Web.

## Short answer

Codex CLI is OpenAI's local command-line coding agent. It runs in your terminal, reads the selected workspace, edits files, runs commands, and follows your sandbox and approval settings while working on development tasks.

It is useful when you want an agent to help with code changes, code review, test fixes, scripts, and multi-step engineering work inside a local repository.

Codex CLI is different from a normal ChatGPT conversation. It does not only suggest code. It works with the current directory, project instructions, tool results, and local execution permissions.

## When this matters

* You are installing `@openai/codex` for the first time
* You are comparing Codex CLI, Codex App, and Codex Web
* You want an agent to edit files in a local project
* You need to configure a custom API provider, Base URL, or model
* You want to understand sandbox, approval, and `AGENTS.md`

## Core concepts

| Concept       | Meaning                                                                                    |
| ------------- | ------------------------------------------------------------------------------------------ |
| Codex CLI     | The Codex coding agent running in your local terminal                                      |
| Workspace     | The directory Codex can read, search, and modify                                           |
| `config.toml` | The local Codex config file for models, providers, sandbox, approvals, and other behavior  |
| `AGENTS.md`   | A project instruction file that tells Codex repository rules and collaboration preferences |
| Sandbox       | The local security boundary for filesystem, network, and command access                    |
| Approval      | The policy that decides which actions need confirmation                                    |

## Recommended workflow

1. Start Codex CLI inside the project directory you want to change.
2. Ask it to inspect relevant files or instructions before making broad edits.
3. For complex work, ask for a plan before letting it change files.
4. Pick sandbox and approval settings based on the risk of the task.
5. Put durable project rules in `AGENTS.md` and one-time requirements in the current conversation.

If you use a third-party API provider, focus on `model_provider`, `base_url`, `wire_api`, and model fields in `config.toml`. Codex and other OpenAI-compatible tools usually use an OpenAI-compatible endpoint, which is `https://www.llmeasy.ru/v1` in this documentation.

## Common mistakes

* Treating Codex CLI as a chat-only assistant.
* Assuming Codex CLI, Codex App, and Codex Web run in the same environment.
* Changing only `model` without configuring the matching provider and Base URL.
* Relaxing sandbox and approval settings without tests, review, or command boundaries.
* Mixing OpenAI-compatible and Anthropic-compatible Base URLs.

## About LLMEasy

When you use a custom OpenAI-compatible provider, LLMEasy can act as the model API layer for Codex CLI. It handles the API Key, Base URL, model routing, balance, and usage records.

LLMEasy does not replace Codex CLI's local sandbox, approvals, `AGENTS.md`, or command execution policy.

## Related docs

* [Codex LLMEasy setup guide](/en/ai-tools/codex)
* [Codex CLI vs Codex App vs Codex Web](/en/faq/codex/codex-cli-vs-app-vs-web)
* [How to configure Codex CLI config.toml](/en/faq/codex/config-toml)
* [OpenAI-compatible API vs Anthropic-compatible API](/en/faq/concepts/openai-compatible-vs-anthropic-compatible)

## References

* [Codex CLI documentation](https://developers.openai.com/codex/cli)
* [OpenAI Codex GitHub repository](https://github.com/openai/codex)
* [Codex configuration reference](https://developers.openai.com/codex/config-reference)