How do I configure a third-party API in Cursor?

Steps — open Settings (Cmd/Ctrl + Shift + J) → Models on the left → turn off the built-in default models → Add Model and enter a custom model ID (e.g. `claude-opus-5`, `gpt-5.6-sol`, `glm-5.2`) → turn on OpenAI API Key and paste your `sk-` key → turn on Override OpenAI Base URL and enter `https://api.lmuai.com/v1` → click Verify → press Cmd/Ctrl + L to open the Chat panel and switch to that model. Note that **only the Chat / Plan panel uses the third-party API**; Cursor's native features like Composer / Tab autocomplete still use the official backend.

Which third-party API protocol does Cursor support?

Only the **OpenAI-compatible protocol** (`/v1/chat/completions`), overridden via Settings → Models → Override OpenAI Base URL. There is currently no native "Override Anthropic Base URL" toggle; to use Claude models in the Chat panel, add the Claude model ID as a custom model over the OpenAI-compatible endpoint, and the LMU AI backend performs the OpenAI ↔ Anthropic protocol translation.

Is a third-party relay cheaper for Cursor?

Usually yes. A relay bills by actual token usage, which is more cost-effective than a Cursor Pro monthly subscription for heavy users (especially frequent Opus / GPT-5 usage); one key also serves Claude / GPT / GLM / Qwen / DeepSeek at once. Note that Cursor's Composer / Tab autocomplete cannot use a third-party API and still consume the Cursor subscription quota.

Can Cursor use a third-party relay API?

Yes, but **only for the Chat / Plan panel**. Cursor's Settings → Models has an "Override OpenAI Base URL" toggle; once on, requests from the Chat / Plan panel (Cmd/Ctrl + L) go through the third-party relay, while native agent features like Composer / Tab autocomplete / Apply / Inline Edit stay locked to the Cursor official backend.

How do I use Claude / GLM / Qwen in Cursor?

Open Settings → Models (Cmd/Ctrl + Shift + J) → add a custom model (model ID `claude-opus-5` / `claude-sonnet-5` / `glm-5.2`, etc.) → turn on Override OpenAI Base URL → set Base URL to `https://api.lmuai.com/v1` → set the API Key to the `sk-` key generated in the LMU AI console.

Can Cursor's Composer / Tab autocomplete use LMU AI?

No. Cursor's core agent features — Composer, Tab autocomplete, Apply, Inline Edit — are locked to the Cursor official backend and cannot be taken over by a third-party relay. For a "full-capability" LMU AI experience, install the [official Codex extension](/en/docs/tools/vscode-plugin) or the [Claude Code for VS Code extension](/en/docs/tools/claude-code-vscode) in Cursor (Cursor is compatible with the VS Code extension marketplace).

Verify fails when I add a model?

Common — non-official OpenAI model names (e.g. `claude-opus-5`, `glm-5.2`) do not pass Cursor's connection check. Workaround: first add an official OpenAI name like `gpt-4` to pass Verify (confirming the Base URL + key connect), then add the custom model IDs you want separately; Verify warns but **it runs fine in practice**.

Do I need a VPN to use LMU AI with Cursor?

The part of the Chat panel configured for LMU AI does not — `api.lmuai.com` is a direct domestic connection. But Cursor's account sign-in, Composer, and Tab autocomplete use the Cursor official backend, which may still need network optimization in China.

Configure Cursor with a third-party API

Q: Does the Base URL need `/v1`?

Yes. Enter `https://api.lmuai.com/v1`, and Cursor appends `/chat/completions` for a final request to `https://api.lmuai.com/v1/chat/completions`. Omitting `/v1` gives a 404.

Configure a third-party API in Cursor — turn on Override OpenAI Base URL, enter your sk- key, and use Claude, GPT, and more in the Chat panel.

Cursor can point the Chat / Plan panel's requests at a third-party relay API via Override OpenAI Base URL. This page explains how to use that native method to connect to LMU AI.

Key limitation: only the Chat / Plan panel is affected

Cursor's Override OpenAI Base URL only affects the Chat / Plan panel (the conversation opened with Cmd/Ctrl + L). Cursor's core agent features — Composer, Tab autocomplete, Apply, Inline Edit — are all locked to the Cursor official backend and cannot be taken over by a third-party relay.

If you need a "full-capability" agent experience in Cursor (including Composer-type features), install instead (Cursor is compatible with the VS Code extension marketplace):

Official Codex extension — a Codex agent over the LMU AI OpenAI protocol
Claude Code for VS Code extension — a Claude Code agent over the LMU AI Anthropic protocol

Configuration steps

Step 1 — Open Cursor Settings

Press Cmd + Shift + J (macOS) or Ctrl + Shift + J (Windows / Linux) to open Settings, and click Models in the left sidebar.

Step 2 — Turn off the default models (recommended)

Cursor ships with many default models (GPT-4 / Claude-3.5, etc.); leaving them enabled conflicts with custom routing. In the model list on the Models page, turn them all off (toggle grayed out on the left).

Step 3 — Add custom models

Click Add Model and enter the LMU AI model IDs you want, for example:

claude-opus-5
claude-sonnet-5
gpt-5.6-sol
glm-5.2
qwen3.8-max-preview
deepseek-v4-pro
kimi-k3

Add each model once. For the full list of available models, see the Model Gallery.

Step 4 — Turn on Override OpenAI Base URL

Scroll to the OpenAI API Key area on the Models page:

Turn on the OpenAI API Key toggle
Paste the LMU AI console key (starts with sk-) into the API Key box
Turn on the Override OpenAI Base URL toggle
Set Base URL to:
```
https://api.lmuai.com/v1
```
Click Verify to check the connection

A failed Verify doesn't mean it's misconfigured

Cursor's Verify checks using the model name you entered, and non-official OpenAI names (claude-opus-5, glm-5.2, etc.) won't pass. Workaround: add a gpt-4 first to pass Verify (confirming the Base URL + key connect), then add the custom model IDs you want separately; Verify warns but it runs fine in practice.

Step 5 — Switch model and use it

Press Cmd/Ctrl + L to open the Chat panel → pick the custom model you added in Step 3 from the model dropdown at the top → start chatting, and requests will go through LMU AI.

Common model IDs

Model ID	Description
`claude-opus-5`	Claude Opus 5 (flagship, recommended)
`claude-sonnet-5`	Claude Sonnet 5 (balanced)
`claude-haiku-4-5`	Claude Haiku 4.5 (high-speed)
`gpt-5.6-sol`	GPT-5.6 Sol
`glm-5.2`	Zhipu GLM-5.2
`qwen3.8-max-preview`	Qwen 3.8 Max Preview
`deepseek-v4-pro`	DeepSeek V4 Pro
`kimi-k3`	Kimi K3
`claude-opus-4-8`	Claude Opus 4.8 (previous generation)
`claude-sonnet-4-6`	Claude Sonnet 4.6 (previous generation)
`gpt-5.5`	GPT-5.5 (previous generation)
`glm-5.1`	Zhipu GLM-5.1 (previous generation)

For the full list, see the Model Gallery.

Common issues

Want Composer / Tab autocomplete to use LMU AI too?

Native Override OpenAI Base URL can't do it — these Cursor core features are locked to the official backend. To route everything through LMU AI, use:

Official Codex extension — an OpenAI-protocol agent
Claude Code for VS Code extension — an Anthropic-protocol agent

Cursor is compatible with the VS Code extension marketplace, so both extensions install directly in Cursor.

Does the Base URL need `/v1`?

Yes. Enter https://api.lmuai.com/v1. Cursor appends /chat/completions for a final request to https://api.lmuai.com/v1/chat/completions. Omitting /v1 gives a 404.

Built-in Claude 3.5 errors out after turning on Override?

This is a known Cursor routing conflict — turning on the OpenAI Base URL override interrupts the Anthropic branch. To keep using Claude in the Chat panel, add the Claude model ID (e.g. claude-opus-5) as a custom model, and the LMU AI backend does the OpenAI ↔ Anthropic protocol translation.

401 / 403 errors?

Check in order:

Is the API Key the sk- key generated in the LMU AI console (not an official OpenAI key)?
Is the Base URL https://api.lmuai.com/v1 (must include /v1)?
Is the model ID one LMU AI supports (see the Model Gallery)?
Does your current plan / billing group include the model you're calling?

Does BYOK affect my Cursor subscription?

BYOK usage does not consume Cursor's monthly fast-request quota
Core features like Composer / Tab autocomplete still consume the Cursor subscription quota (because they don't use BYOK)
To drop the Cursor subscription entirely, see the Codex / Claude Code extension approach above

Last updated: 2026-08-26