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Cursor is Anysphere’s AI code editor. It has two independent things worth wiring to Opper: the model endpoint it calls, and the rules file that teaches it the Opper SDKs.

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Run Cursor on Opper models

Cursor takes a custom OpenAI base URL in its settings:
1

Open model settings

Settings → Models, then enable Override OpenAI Base URL.
2

Set the base URL

3

Add your API key

Paste an Opper key from platform.opper.ai into the OpenAI API key field, then add the model IDs you want — for example anthropic/claude-sonnet-4-6. Verify the key to activate the override.
Cursor’s BYOK path drives chat and inline edits. Some Cursor-specific features — Tab completion and Composer’s agent mode among them — run on Anysphere’s own infrastructure and ignore the override. That’s a Cursor product decision, not a gateway limitation.

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Add Opper rules to your project

Separately from the endpoint, you can give Cursor context about the Opper SDKs so it writes correct Opper code:
  1. Download the .mdc file for your language:
  2. Place it in your project at .cursor/rules/opper.mdc.
  3. In Cursor, set the rule to Always.

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Troubleshooting

Cursor needs each model ID added by hand under Settings → Models — it doesn’t fetch the catalog. Copy IDs from the catalog.
Expected. The base URL override covers chat and edits; Tab runs on Anysphere’s own service.
Cursor verifies by making a real call against the first model in your list. If that model ID is wrong or your model access rules deny it, verification fails even though the key is valid.

Skills

Drop Opper context into other AI editors.

All integrations

Every app that runs on Opper.