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

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.