Setup Guideline

Manual setup · Windows and macOS

Cursor + Space Router

Cursor lets you bring your own key. Point it at Space Router and the Chat and Agent windows call Claude or GPT models on your balance instead of a Cursor subscription.

Gateway: https://space.stationine.com · Last checked:

Keep your API key private. Never share a real API key in screenshots, chat messages, repositories, project files, or public documents. If a key has been exposed, revoke or rotate it in Space Router and create a new one.

There is no one-command installer for Cursor. Everything below is typed into Cursor's own settings window, so the five steps are identical on Windows and macOS. Budget about five minutes.

Before you start

Install Cursor from cursor.com if you have not already. Then decide which key group you are using, because it decides both the provider section you fill in and the model slugs available to you.

Key groupCursor provider sectionModel slugs
GPT (group 4) OpenAI gpt-6-astra, gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna, gpt-5.5, gpt-5.4, gpt-5.4-mini
Claude (group 3) Anthropic claude-opus-5, claude-sonnet-5, claude-opus-4-8, claude-opus-4-7, claude-opus-4-6, claude-sonnet-4-6
Claude Fable 5 (group 5) Anthropic claude-fable-5

A key only works inside its own group. A Claude key asking for gpt-5.5, or a Claude key asking for claude-fable-5, gets a hard error rather than a fallback — Fable is a separate purchase. The live catalogue is published at /models.json.

If you are not sure which to start with: claude-sonnet-5 on a Claude key, gpt-5.6-sol on a GPT key.

Step 1 · Create the key

  1. Open the dashboard

    Go to space.stationine.com and sign in. If you have a redeem code and have not used it yet, open Redeem in the left menu, paste the code, and press Redeem Code. The balance updates immediately.

  2. Open API Keys and create one

    Click API Keys in the left menu, then Create API Key. Type any name. In the Group selector choose the group from the table above. Leave the other options at their defaults and press Create.

    Space Router Create API Key dialog with the Name field and the Group selector
    Name it anything. The Group is the part that matters.

  3. Copy the sk- value

    Select it carefully. A space copied in front of or behind the key is the most common reason a correct key still returns 401.

Step 2 · Open the model settings

  1. Open Cursor Settings

    Windows

    Press Ctrl + Shift + J, or click the gear icon at the top right of the window.

    macOS

    Press ⌘ + Shift + J, or click the gear icon at the top right of the window.

  2. Go to Models

    In the settings sidebar click Models. If you cannot see it, type Models into the settings search box at the top. The page has two parts you will use: a list of models, and further down an API Keys area with one section per provider.

Step 3 · Add the model slug

Do this before switching the provider on. Cursor only offers models it already knows about, and Space Router's slugs are not in its built-in list, so you add them yourself.

  1. Open the model list

    In the Models page, find the list of model names with checkboxes beside them and the control for adding one — labelled + Add model or Add custom model depending on your Cursor version.

  2. Type the slug exactly

    Enter the slug from the table above and confirm. Use the slug, not a display name: claude-sonnet-5 works, Claude Sonnet 5 does not. Repeat for each model you want available.

  3. Make sure it is ticked

    A newly added model is not always enabled. Confirm its checkbox is on, or it will not appear in the chat model picker later.

Step 4 · Key and override base URL

Fill in only the section that matches your key group, and leave the other providers switched off. Mixing two providers on one key is the second most common cause of a 404.

  1. Switch the provider on

    In the API Keys area, turn on the toggle beside OpenAI API Key (GPT group) or Anthropic API Key (Claude and Fable groups).

  2. Paste the key

    Paste the sk- value into that section's key field.

  3. Open the base URL override and enter the address

    Tick Override Base URL — in some versions it is behind a small Override link or a disclosure arrow next to the key field. Then enter the value for your group:

    GPT key → OpenAI section

    https://space.stationine.com/v1

    Ends at /v1, because Cursor appends /chat/completions itself.

    Claude or Fable key → Anthropic section

    https://space.stationine.com

    No suffix, because this path appends /v1/messages itself.

    Three details decide whether this works: no trailing slash, https with the s, and no stray space from the copy.

  4. Press Verify

    A pass means Cursor reached the gateway and the key was accepted. It does not prove your chosen model works — that is the next step.

The values in one place, if you just want to copy them:

Step 5 · Send a real message

  1. Open a normal Chat window

    Press Ctrl + L on Windows or ⌘ + L on macOS.

  2. Pick your model in the picker

    Use the model selector at the bottom of the chat box and choose the slug you added. If it is not listed, go back to step 3 — it was added but not ticked.

  3. Send Reply with OK

    A reply means the key, the base URL and the model slug are all correct together. This is the only check that proves the whole route.

Using Agent

Test plain Chat before you trust Agent. Agent sends tool calls that exercise more of the protocol, so it is the wrong place to discover a configuration mistake. Once Chat replies, switch the same conversation to Agent and give it a small, reversible task first.

Tab completion is unaffected by any of this. It runs on Cursor's own internal models, so it neither uses your Space Router balance nor stops working when the override is set.

Where the settings live

Cursor keeps the key and the base URL in its own application settings, not in a file you are meant to edit by hand. Change them through the same Settings window. To undo this setup, clear the override base URL field, remove the key, and switch the provider toggle back off.

Field labels drift between Cursor versions. The same box has been called Base URL, Override Base URL and Custom Base URL at different times, and the override has sat behind a checkbox, a link and a disclosure arrow. If a label does not match this page exactly, match on meaning — there is one key field, one URL field and one model list to fill in.

Troubleshooting

What you seeWhat it means
401 or 403 The key is wrong, revoked, or out of balance. Re-copy it from the dashboard and check for a leading or trailing space.
404, or the model is missing The slug is misspelled, it belongs to a group your key does not have, or the base URL has the wrong /v1 treatment for the section you filled in.
Verify passes, Agent fails Basic connectivity is fine. Confirm plain Chat replies first, then retry Agent; a model without tool-calling support cannot drive Agent.
The model is not in the chat picker It was added to the Models list but its checkbox is off. See step 3.
Tab completion unchanged Expected. Tab completion runs on Cursor's own internal models and is not affected by a base-URL override.
The setting reverts after a restart Fully quit Cursor — not just the window — and reopen it, then re-enter the value once. Cursor writes model settings on a clean exit.

What is Space Router?

Space Router is an AI API relay operated by Station Nine. Its base URL is https://space.stationine.com. It accepts Anthropic Messages requests at POST /v1/messages, OpenAI Chat Completions requests at POST /v1/chat/completions, and OpenAI Responses requests at POST /v1/responses, and it provides OpenAI GPT and Anthropic Claude model families. See the full Space Router overview for service and account details.

Need credentials? Get your API key from Space Router.