Task tool `model` parameter only accepts "fast" — cannot specify model IDs for subagents

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1

Where does the bug appear (feature/product)?

Cursor CLI

Describe the Bug

The Task tool’s model parameter only accepts "fast". Passing any specific model ID (e.g. claude-sonnet-4-6, claude-opus-4-6) returns:

Invalid model selection. Available models are: - fast

This contradicts the subagents documentation which states the model field supports three options: inherit, fast, or a specific model ID like claude-4-sonnet or claude-opus-4-6.

Custom subagent frontmatter with model: claude-sonnet-4-6 is also ignored — the tool schema enforces enum: ["fast"] at the parameter level, so the agent cannot even attempt to pass the value.

Steps to Reproduce

  1. Create a custom subagent at ~/.cursor/agents/test-model.md:
---
name: test-model
model: claude-sonnet-4-6
description: Test model selection
---
Say "hello, I am running on claude-sonnet-4-6" and stop.

  1. In an agent conversation, ask the agent to dispatch a Task with model: "claude-sonnet-4-6".

  2. The tool returns the error: Invalid model selection. Available models are: - fast

  3. With model: "fast", the subagent runs but self-reports as Sonnet 4.5, not the requested Sonnet 4.6.

  4. Without the model parameter, the subagent inherits the parent model — there is no way to target a middle-tier model.

Expected Behavior

The Task tool should accept specific model IDs as documented, e.g. claude-sonnet-4-6, claude-opus-4-6, matching the model configuration docs and the agent frontmatter spec.

Error output from Task tool:

Error: Invalid arguments:
model: Invalid model selection. Available models are:
  - fast: Extremely fast, moderately intelligent model...

Tool schema (as presented to the agent):

"model": {
  "description": "Optional model to use for this agent...",
  "enum": ["fast"],
  "type": "string"
}

Operating System

MacOS

Version Information

  • Cursor Agent (CLI): 2026.03.30-a5d3e17
  • Cursor IDE: 2.6.22 (c6285feaba0ad62603f7c22e72f0a170dc8415a0)

For AI issues: which model did you use?

claude-4.6-opus (parent agent), attempting to dispatch claude-sonnet-4-6 (subagent)

Additional Information

it prevents a key workflow. Orchestrator-pattern agents (documented in the subagents docs) rely on dispatching subagents on a middle-tier model for cost/capability balance. The only options today are fast (too weak for complex tasks) or omitting the param (inherits Opus — too expensive for routine work).

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

1 Like
5

This is a known limitation. The Task tool’s model parameter currently only supports "fast" for most users. Expanded model selection for subagents (allowing specific model IDs like claude-sonnet-4-6) is not yet generally available.

The model field in subagent frontmatter (.cursor/agents/*.md) is parsed, but if the specified model ID isn’t recognized, the system silently falls back to the parent model. This explains why your subagent runs on the parent’s model rather than the one configured in frontmatter.

A few related threads with the same report:

Our team is aware of this gap and it’s being tracked for the subagents feature. No ETA yet, but reports like yours help with prioritization.

In the meantime, the only model options for subagents are: omit the model parameter (inherits the parent model) or use "fast" (a lighter model optimized for quick tasks).

7

why did you deprecate/remove the multiple model toggle?!?!?!?! :frowning:

please bring it back!!! please :frowning: