> ## 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.

# OpenAI-Compatible API vs Anthropic-Compatible API

> Understand how OpenAI-compatible and Anthropic-compatible APIs differ, and how to choose the right Base URL for Claude Code, Codex, Cursor, and Cline.

## Quick answer

OpenAI-compatible API and Anthropic-compatible API are two different compatibility layers. Both can be used for model requests, but their request formats, fields, tool semantics, and client expectations differ.

Codex CLI, Cursor, Cline, OpenCode, and OpenClaw usually use OpenAI-compatible endpoints. Claude Code and some Claude Desktop Gateway paths use Anthropic-compatible endpoints.

Do not choose only by model name. Choose by the protocol expected by the tool, then use the matching Base URL, API Key, and Model ID.

## When this matters

* You see two Base URLs and do not know which one to use
* Claude Code works, but Codex or Cursor fails
* Codex works, but Claude Code reports endpoint or auth errors
* You want to use one API Key across multiple tools
* You are configuring an API gateway, model router, or local proxy

## Key concepts

| Concept                  | Meaning                                                                                    |
| ------------------------ | ------------------------------------------------------------------------------------------ |
| OpenAI-compatible API    | An endpoint that follows OpenAI-style request conventions                                  |
| Anthropic-compatible API | An endpoint that follows Anthropic / Claude request conventions                            |
| Base URL                 | The API root address used by the client                                                    |
| API Key                  | The credential for the selected provider                                                   |
| Model ID                 | The model identifier available under that provider and protocol                            |
| Gateway                  | A layer for compatibility, routing, billing, or observability between client and providers |

## Recommended choice

Start with the tool:

| Tool                   | Common protocol direction           | Base URL in this documentation |
| ---------------------- | ----------------------------------- | ------------------------------ |
| Claude Code            | Anthropic-compatible                | `https://www.llmeasy.ru`       |
| Claude Desktop Gateway | Anthropic-compatible or local route | Follow the Gateway setup       |
| Codex CLI              | OpenAI-compatible / Responses       | `https://www.llmeasy.ru/v1`    |
| Cursor                 | OpenAI-compatible                   | `https://www.llmeasy.ru/v1`    |
| Cline                  | OpenAI-compatible provider          | `https://www.llmeasy.ru/v1`    |
| OpenCode / OpenClaw    | OpenAI-compatible                   | `https://www.llmeasy.ru/v1`    |

If a tool expects OpenAI-style APIs, do not use the Claude Code Anthropic Base URL. If a tool expects Anthropic-style APIs, do not use the OpenAI-compatible `/v1` endpoint.

## Common mistakes

* Assuming one model name can be used unchanged across every protocol.
* Putting the OpenAI-compatible Base URL into Claude Code.
* Putting the Anthropic-compatible Base URL into Codex, Cursor, or Cline.
* Treating a Claude.ai or ChatGPT subscription as an API Key.
* Changing only the API Key while leaving the Base URL and Model ID mismatched.

## About LLMEasy

LLMEasy provides both Anthropic-compatible and OpenAI-compatible access patterns. You can manage API Keys, balance, and usage history in one dashboard, but each client still needs the protocol it actually supports.

A simple rule: Claude Code uses Anthropic-compatible; Codex, Cursor, Cline, OpenCode, and OpenClaw usually use OpenAI-compatible.

## Related docs

* [Claude Code setup guide](/en/ai-tools/claude-code)
* [Codex setup guide](/en/ai-tools/codex)
* [Cursor setup guide](/en/ai-tools/cursor)
* [How to configure API Key and Base URL in Claude Code](/en/faq/claude-code/api-key-base-url)

## References

* [Anthropic OpenAI SDK compatibility](https://docs.anthropic.com/en/api/openai-sdk)
* [Anthropic API versioning](https://docs.anthropic.com/en/api/versioning)
* [OpenAI Responses API reference](https://developers.openai.com/api/reference/responses/overview/)
* [Anthropic-compatible API explanation](https://bentoml.com/llm/model-interaction/anthropic-compatible-api)