token drain loop

### What happened?

[ACTION REQUIRED] 📎 PLEASE ATTACH THE EXPORTED CHAT HISTORY JSON FILE TO THIS ISSUE IF YOU FEEL COMFORTABLE SHARING IT.

### What did you expect to happen?

loop detection to stop problem and this shipped missing template.py causing errors repeatedly.

### Client information

* **CLI Version:** 0.50.0
* **Git Commit:** 8d9733d53
* **Session ID:** f17d5d2e-1e07-4f3d-a19d-a87f1adffe32
* **Operating System:** win32 v25.9.0
* **Sandbox Environment:** no sandbox
* **Model Version:** auto
* **Auth Type:** gemini-api-key
* **Memory Usage:** 376.0 MB
* **Terminal Name:** Unknown
* **Terminal Background:** #0c0c0c
* **Kitty Keyboard Protocol:** Unsupported

### Login information

_No response_

### Anything else we need to know?

_No response_

Start by reproducing the token-drain loop in the CLI using the reported v0.50.0 environment and, if available, the exported chat history JSON. Inspect the loop-detection path and the missing template.py failure; done means repeated errors stop instead of draining tokens.

索引モデルが issue の本文から書いたものです。