[BUG] Session degrades silently after version update mid-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?

Summary

When a Claude Code version update lands while a session is active, the session silently degrades — hallucinated actions, confused responses — with no warning to the user. /clear does not fix it. Only a full restart resolves it.

Steps to Reproduce

1. Start a Claude Code session and verify it's working well.
2. Leave the session open and wait for a version update to land.
3. After the update, continue working in the same session.
4. Observe degraded responses — hallucinations, confused actions.
5. Try /clear — does not resolve it.
6. Restart Claude Code — immediately back to normal.

Why This Matters

• Users trust Claude's output and may not notice the degradation for a while.
• Work done during the degraded window may need to be reverted.
• It burns through context and rate limits on bad output.
• It reflects poorly on Claude's perceived reliability.

Proposed Solutions

Option A — Hot swap: Apply the update to the running session seamlessly.

Option B — Restart prompt (minimum viable fix): Display a visible warning:

⚠️ A new version is available — restart recommended for best results.

Option B alone would prevent most of the damage.

Environment

• Claude Code: v2.1.84
• Model: Opus 4.6 (1M context)
• Plan: Claude Max
• OS: Ubuntu (Dell Precision 7820)

What Should Happen?

Proposed Solutions

Option A — Hot swap: Apply the update to the running session seamlessly.

Option B — Restart prompt (minimum viable fix): Display a visible warning:

⚠️ A new version is available — restart recommended for best results.

Option B alone would prevent most of the damage.

Error Messages/Logs

No error messages.

Steps to Reproduce

1. Start a Claude Code session and verify it's working well.
2. Leave the session open and wait for a version update to land.
3. After the update, continue working in the same session.
4. Observe degraded responses — hallucinations, confused actions.
5. Try /clear — does not resolve it.
6. Restart Claude Code — immediately back to normal.

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.84 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

Terminal: VS Code Integrated Terminal (Remote SSH)
Shell: bash (Ubuntu)