Empty thinking delta with composer-1 model when using cursor-agent

Bug Reports
1

Where does the bug appear (feature/product)?

Cursor CLI

Describe the Bug

When using cursor-agent with composer-model and streaming json, the delta for thinking process is an empty string.

{"type":"thinking","subtype":"delta","text":"","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617660}
{"type":"thinking","subtype":"delta","text":"","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617664}
{"type":"thinking","subtype":"delta","text":"","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617675}
{"type":"thinking","subtype":"delta","text":"","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617695}
{"type":"thinking","subtype":"delta","text":"","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617695}
{"type":"thinking","subtype":"completed","session_id":"9d86d830-7d2d-4fa5-992b-4a8a7ac576b9","timestamp_ms":1762389617734}

Steps to Reproduce

Run the following command:

cursor-agent -p --model composer-1 --force --output-format stream-json "create a new html with hello world"

it’s the same for “–stream-partial-output”

cursor-agent -p --model composer-1 --force --output-format stream-json --stream-partial-output  'create a new html with hello world'

Expected Behavior

The delta should not be an empty string

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

2025.10.28-0a91dc2

For AI issues: which model did you use?

composer-1

Does this stop you from using Cursor

No - Cursor works, but with this issue

2

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