Composer 1 can't use Sub Agent

Support Bug Reports
,
1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Composer seems not to see or be able to use sub-agents.
Sonnet 4.5 and even Gemini Flash can use sub-agents.

Steps to Reproduce

Ask Composer to run a sub-agent.
It will say it can’t find the Task tool.

Expected Behavior

Composer 1 and all modles should be able to use sub agents

Operating System

MacOS

Version Information

Version: 2.4.21
VSCode Version: 1.105.1
Commit: dc8361355d709f306d5159635a677a571b277bc0
Date: 2026-01-22T16:57:59.675Z
Build Type: Stable
Release Track: Default
Electron: 39.2.7
Chromium: 142.0.7444.235
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Darwin arm64 25.2.0

For AI issues: which model did you use?

Composer 1

For AI issues: add Request ID with privacy disabled

Not possible to disable privacy

Additional Information

It’s a shame that your in-house model isn’t tested to ensure it works correctly with new features.

Does this stop you from using Cursor

Yes - Cursor is unusable

3 Likes
3

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4

My subagents are using composer automaticly instead of the model i used in the main chat

1 Like
5

I think you may have misread the topic. It seems that Composer 1 can’t use sub-agents or spawn sub-agents.

6

Hey, thanks for the report. I can see the screenshot with the error “Cannot find the ‘Task’ tool”.

The team is aware of issues with subagents and model selection. Right now there are two known points:

  1. UI bug: the subagent chat may show “Composer 1” no matter which model is actually being used
    [Nightly] The subagent chat displays an incorrect AI model - #3 by deanrie

  2. Model behavior: not all models support subagents the same way

In your case we need to figure out if Composer 1 really can’t call a subagent (a functional bug), or if the UI is just showing the wrong model name.

Can you grab the Request ID? I know Privacy Mode is enabled (Business account?), but please try turning it off temporarily:

  • Open the Chat context menu (three dots in the top right)
  • Copy Request ID

This will help the engineers confirm which model was actually used.

@anonix98: I saw your comment that subagents automatically use Composer. That’s likely the same issue. Similar reports are here:

7

@deanrie The issue here is that it’s impossible to tell Composer 1 to spawn a sub-agent. Did you intentionally remove the sub-agent tool for this model?

2 Likes
8

Same issue here. :thinking:
It is impossible to spawn a subagent when you are using Composer or Auto on main chat. It never able to do. I am using latest stable update (2.4.22)

1 Like
10

same on 2.4.28, very annoying.

11

Same with composer 1.5 btw.

2 Likes
12

I’m having the same problem with composer 1.5. I have a comment that has a step like this:

Spawn off n=10 (unless specified otherwise) task agents to dig deeper into the codebase…

It works fine with sonnet, opus and GPT codex, but composer 1.5 just straight up ignores this and never spawns any agents.

13

Hi all, I can 110% confirm that the Composer models (1 and 1.5) don’t have access to the “Task” tool that allows them to spawn sub-agents.

Composer also seems to have access to a special toolset that is different from Codex/Claude (for example, the shell tool have different args for Composer, old ones).

I believe that due to the intense RL training on these models, they can’t properly use those tools, and Composer needs to be retrained with RL to use these newer tools effectively.

14

Confirmed still an issue on 2.5.17. FYI @Colin related to issue: My subagents can't be used in auto model - #14 by Steven_Padfield

@deanrie you can look at my request IDs if it helps:

Failure case (Composer): cb80b34e-4d6d-4cd2-9885-477ab6820fa6

Success case (Sonnet): 7eda7723-8c30-4ce3-abce-2544491ec11b

1 Like