/model: switching models mid-session hangs the CLI until switching back to the original model

Description

Switching models mid-session via /model works, but afterwards revoking / switching the model selection again causes the app to hang — it stays unresponsive until I switch back to the original model, at which point it recovers.

Repro (as experienced, mid-session with an active conversation):

1. Start a session on one model (Opus 4.8, 1M context).
2. /model → switch to another model (Fable 5) mid-session — works, saved as default.
3. Attempt to revoke/switch the model selection again → the CLI hangs.
4. Only recovers after switching back to the original model.

Environment

• Claude Code: 2.1.215
• OS: Windows 11 Home 10.0.26200
• Shell: PowerShell (Git Bash also in use)
• Session was mid-conversation (long-running session with subagents/background tasks earlier in it)
• Note: I may be on an RC/preview build

Notes

Filed via Claude Code on my behalf at my request (the exact wording of my in-session report: switching/revoking the model hangs the app until going back to the original). Happy to provide more repro detail if needed.