I’m using Cursor Pro and I have also added my own API keys for OpenAI and Anthropic in the settings.
In the settings, I selected Composer 2.5 as the Explore subagent model. However, as shown in the screenshot, when Cursor creates Explore subagents, it still uses Opus 4.8 Extra High instead of Composer 2.5.
I’m also experiencing a separate issue when trying to use Composer 2.5, which I have already mentioned in another topic.
Could anyone please let me know if I’m missing a setting, or if this is expected behavior? Is there any way to force Cursor to use Composer 2.5 for Explore subagents when using my own API keys?
I would really appreciate any guidance or suggestions.
Hey, thanks for the report. This isn’t a bug, it’s expected behavior. I’ll explain.
When you have your own API keys enabled OpenAI or Anthropic, Cursor pins all subagents, including Explore, to the parent agent’s model. Your parent is Opus 4.8 Extra High, so the Explore subagents inherit that, and the Explore subagent model picker won’t apply in this mode.
Also, Composer 2.5 is a Cursor proprietary model, so it can’t be served through your own OpenAI or Anthropic keys at all. So even if you picked it, it still wouldn’t work with BYOK enabled.
What you can do is if you want Explore subagents to use Composer 2.5, turn off the API Keys toggles in settings. Then requests will go through your Cursor subscription, and Composer 2.5 will be available. This is the same root cause as in your other thread about This model does not support custom API keys.
Composer 2.5 is Cursor’s proprietary model, and it can’t run when a custom OpenAI key is enabled. The backend rejects requests with This model does not support custom API keys. So when the OpenAI key is on, Composer 2.5 isn’t available for the Explore subagent, and it falls back to the parent model, which for you is Opus 4.8.
When the OpenAI key is off and only Anthropic is enabled, Composer 2.5 becomes available again. That’s why the Explore subagent uses it correctly in that mode.
So the working setup for your case is to keep the OpenAI key disabled, then Composer 2.5 for Explore subagents works as expected. If you want to keep BYOK enabled, another option is Auto mode, since in Auto mode BYOK credentials aren’t sent for Composer routing.
Having to toggle the key back and forth is annoying, agreed. We’ve logged an improvement for this, but there’s no exact timeline yet. Let me know if anything else comes up.
