Cursor
Custom base URL settings and the limits of current verification.
Reference only
2026-10-10. Installed Cursor 3.20.17 was inspected for configuration labels; no inference session was run. Cursor routes these requests through its servers, so an isolated local gateway is not reachable from that path.
Cursor is a code editor with AI chat and agents. Its custom-key support does not guarantee that every selected model uses the Chat Completions protocol required here.
Before you start
Complete the Quickstart: add credits, create a key, and copy a model ID from Marketplace. Choose a model with tool support for agent tasks. The example ID is claude-sonnet-5-5; replace it with your selection. Use the Claude Code or Aider guide if you need a locally tested setup.
Configure the tool
These are the candidate settings for a Cursor version that exposes the override. Configure them in the UI on macOS, Linux, or Windows; no configuration-file recipe has been verified.
- Open Cursor Settings → Models.
- Enter your gateway key in OpenAI API Key.
- Enable Override OpenAI Base URL and enter
https://unused.market/v1. - Use Add Custom Model to enter the canonical ID from Marketplace, then select it in chat.
TODO(verify): Confirm an end-to-end request with Cursor 3.20.17 and the selected model. The current official help page documents API keys but does not specify the override's current wire-format selection.
Verify the connection
Ask: “Say hello in one sentence without using tools.” Then open Analytics → Requests. Find the new request by time and model. A response and a matching row confirm that traffic reached your account. This checks the connection, not the quality of repository edits. If a request targets /responses, this connection is incompatible with the gateway; use a supported client.
Limits and troubleshooting
Custom API keys apply to chat models; Cursor's Tab completion uses its own models. An older official support response describes GPT requests using Responses when a base URL is overridden. Do not assume that changing the hostname changes that behavior.
| Symptom | Next step |
|---|---|
| Missing override field | Check your Cursor version and account settings; use a tested guide if the field is unavailable. |
/responses or input-format error | The selected path uses a different protocol. Use a Chat Completions client. |
| Response with no row in Requests | Check which model and provider are selected before making further calls. |
Sources and verification
Checked 2026-10-10: locally installed version 3.20.17, configuration labels only. Current official API-key help; official support discussion of the Responses mismatch. The support discussion is historical evidence, not a successful test of this version.