Can't spawn subagent of different family

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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Since updating to 3.12.x, agents can no longer spawn subagents from a different model family than the parent chat’s model. The subagent model list offered to the agent is filtered to the parent’s family plus Composer:

  • Claude parent chat → only Claude models + composer-2.5-fast offered; asking for a GPT 5.6 Sol subagent fails as unavailable.
  • GPT 5.6 Sol parent chat → only GPT (inherit) + composer-2.5-fast; no Claude models.

On 3.11 and earlier, a Claude-model chat could spawn GPT 5.6 Sol subagents.

This isn’t a settings issue: toggles in Settings → Models propagate to the agent’s list live, but cross-family models never appear regardless of what’s enabled. The restriction isn’t mentioned in the 3.12 changelog.

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Steps to Reproduce

  1. Update to Cursor 3.12.17.
  2. In Settings → Models, make sure both Claude models and GPT 5.6 Sol are enabled.
  3. Start a new agent chat with a Claude model selected as the chat model.
  4. Ask the agent: “Which models can you access for subagents?” — it lists only Claude models + Composer.
  5. Ask it to spawn a GPT 5.6 Sol subagent — it declines, saying the model isn’t in its available list.
  6. Switch the chat model to GPT 5.6 Sol (or start a fresh chat with it) and ask the same question — now only GPT (via inheritance) + Composer are available, and Claude models are gone.

Operating System

MacOS

Version Information

Version: 3.12.17 (stable)
Commit: 0fb762053c34788bb7760d5673f8a6d4c8589d50
Build Date: 2026-07-17T02:53:53.006Z
Electron: 40.10.3
OS: Darwin arm64 24.6.0 (macOS 15.6.1)

For AI issues: which model did you use?

Fable 5

Does this stop you from using Cursor

No - Cursor works, but with this issue

6

Hey there!

The good news: this is on our side, not your settings, and there’s no by-design family restriction. A subagent can use any agent-capable model you’ve enabled in Settings → Models (plus Composer), regardless of the parent chat’s model, so cross-family spawns are supported. The subagents docs even show a subagent pinned to a GPT model.

What you ran into lines up with a recent change to how the agent selects subagent models, where it was being too conservative about reaching into another family, rather than an actual account or settings block. We’ve been improving this since, so please try again in a fresh chat. It should already behave better.

If you want a guaranteed cross-family subagent, define it explicitly in a file like .cursor/agents/reasoner.md with model: gpt-5.6-sol in the frontmatter. That pins the model regardless of the parent chat.

If an enabled model still comes back as “unavailable” after that, reply here and I’ll dig in.

7

Hello!

Thanks for the response. Seems like the issue is still there. I’m on 3.12.17 (latest).

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