[BUG] [Bug] Interrupting Ultraplan thinking turn stops/crashes cloud container and ends session

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug Description
When using Ultraplan, interrupting a thinking period on the web session (with the GUI stop button, maybe with Esc in past instances) stops the cloud container and ends the session.
Intent: Interrupt the thinking period, force it to read the queued messages before proceeding.
Reproducibility: Reliable, 4/4 times so far. I've never gotten more than three messages into an Ultraplan session before this happened. It makes Ultraplan basically unusable IME.

Long-term effect: I'm currently trying to resume the conversation, but that was hanging 17m and counting at the 'resume your container' step when I gave up. Starting the container fresh took less than a minute; I tentatively think it's not recoverable.

Sessions (recovered 1.5/4):

session_01XaaxKC3HvmoyQZan7NuJd4
Spawn: Jun 30, 2026, 3:41:59 PM
Stop: Unrecorded

session_015arwqbvwn9Pqt9xWPKEMsJ
Spawn: Jul 16, 2026, 6:43:13 PM PDT
Stop: Jul 16, 2026, 6:48 PM PDT

Comparing to non-Ultraplan web Code: Don't know, never seen any reason to use that. Can try it if you want.

Environment Info (autopopulated, likely not relevant)

• Platform: linux
• Terminal: tmux
• Version: 2.1.211 (Claude Code CLI)
• Feedback ID: b7eedab7-03f1-42d2-b84b-2419fc81f473

Ultraplan Info (me guessing relevance)

• Browser: firefox
• Version: 152.0.5 (64-bit)
• Relevant Extensions: uBlock Origin, Tampermonkey (nothing active)

Errors
All on web, and unfortunately nothing I can capture after the fact, AFAICT. Can probably replicate it while catching network logs if you need it.

What Should Happen?

Interrupt the thinking period, force it to read the queued messages before proceeding.

Error Messages/Logs

All on web, and unfortunately nothing I can capture after the fact, AFAICT. Can probably replicate it while catching network logs if you need it.

Steps to Reproduce

Reliable, 4/4 times so far. I've never gotten more than three messages into an Ultraplan session before this happened. It makes Ultraplan basically unusable IME.

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

0

Platform

Anthropic API

Operating System

Other

Terminal/Shell

Other

Additional Information

_No response_