Cannot start sub agent

Support Bug Reports
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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

When the main agent triggers a sub-agent, the parent agent gets stuck at “Planning next step” for a while. After it times out, Cursor shows “Couldn’t start”. Then the parent agent retries starting the sub-agent.

When I open the sub-agent content/chat, it shows:
“This chat could not be loaded”

This seems related to the existing sub-agent “Starting up” / “Loading Chat” issues, but in my case the sub-agent appears to fail starting and the sub-agent chat cannot be loaded afterwards.

Steps to Reproduce

ask llm trigger subagent in agent view

Expected Behavior

the subagent work correctly

Screenshots / Screen Recordings

螢幕擷取畫面 2026-05-13 145528
螢幕擷取畫面 2026-05-13 145528758×138 2.35 KB

螢幕擷取畫面 2026-05-13 145700.png
螢幕擷取畫面 2026-05-13 145700.png729×737 4.24 KB

Operating System

Windows 10/11

Version Information

Version: 3.3.30 (system setup)
VSCode Version: 1.105.1
Commit: 3dc559280adc5f931ade8e25c7b85393842acf30
Date: 2026-05-09T18:28:42.332Z
Layout: glass
Build Type: Stable
Release Track: Nightly
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.22631

For AI issues: which model did you use?

auto

For AI issues: add Request ID with privacy disabled

c0c57a22-07b5-43d6-b8ce-bbf17a4860f9

Does this stop you from using Cursor

No - Cursor works, but with this issue

5

Hey, thanks for the detailed report. The Request ID, version, and screenshots really help. I can see This chat could not be loaded in the preview tray, and the parent stuck on Planning next step.

This is a known issue in the Glass layout when the subagent preview opens before the child agent has time to register. I’ve reported it internally, but there’s no ETA for a fix yet.

Workaround for now: if the parent retries after Couldn’t start and the subagent eventually launches, wait for the retry, then try opening the subagent chat again. If it won’t start at all, starting a New Chat in the parent agent can help.

If you notice a specific pattern, like it always fails on the same task type, send it here and I’ll pass it to the team. Once we have an update on the fix, we’ll reply in this thread.

7

Thanks for your reply!

9

Hey @cy_c!

We’ve made some changes in the sub-agent preview area since you posted — could you update to the latest Cursor (3.6.31+) and let me know if the parent still gets stuck on “Planning next step” and the sub-agent chat still fails to load?