[BUG] v1.1.3963 regression: multiple sessions in same cwd cross-contaminate prompt routing Version: 1.1.3963 (regressed from 1.1.3918 which worked correctly) #27666

Preflight Checklist

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

What's Wrong?

Open 2+ session tabs in the same directory. Submit a prompt. It routes to the wrong/multiple sessions.

What Should Happen?

Each session tab should only receive and process prompts submitted within that specific tab. Prompts submitted in Session A should never appear in or be processed by Session B.

Error Messages/Logs

From %APPDATA%\Claude\logs\main.log — rapid focus switching during tab change:

2026-02-22 08:42:47 [info] [CCD] LocalSessions.setFocusedSession: sessionId=null
2026-02-22 08:42:47 [info] [CCD] LocalSessions.setFocusedSession: sessionId=local_01c58e4e-3966-4b98-9603-ee5a3161446f
2026-02-22 08:42:53 [info] [CCD] LocalSessions.setFocusedSession: sessionId=null
2026-02-22 08:42:53 [info] [CCD] LocalSessions.setFocusedSession: sessionId=local_e71a84b2-f1de-4107-a629-4ad4acb5f4b1

API 500 errors (coinciding with multi-session load):
oauth failed: authorize returned 500 {"type":"error","error":{"type":"api_error","message":"Internal server error"},"request_id":"req_011CYL5rxSUfamfwSwbxTj6s"}

Steps to Reproduce

1. Open Claude Code Desktop v1.1.3963 on Windows 11
2. Open two or more session tabs pointed at the same working directory
3. Click between session tabs (triggering focus switching)
4. Type a prompt and press Enter in Session A
5. Observe: the prompt is processed by Session B (or both sessions simultaneously)

Note: This is a confirmed regression. Version 1.1.3918 did not exhibit this behavior.
The update from 1.1.3918 → 1.1.3963 occurred on 2026-02-21 at ~19:33–19:35 local time,
confirmed via app_version entries in main.log.

Root cause appears to be: when setFocusedSession transitions through null during a tab
switch, a prompt submitted during that null window routes to the wrong session.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1.3918

Claude Code Version

2.1.50 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Claude Code Desktop (CCD) — not CLI/terminal
This is a Claude Code Desktop (CCD) GUI bug, not a CLI issue. The bug occurs in the
Desktop app's session tab management, not the terminal/shell environment.

• App version confirmed via %APPDATA%\Claude\logs\main.log: 1.1.3963
• Regression introduced via auto-update on 2026-02-21 between 19:33–19:35 local time
• Previous version 1.1.3918 did not have this issue (confirmed in same log file)
• All affected sessions were running in the same working directory: C:\Users...\project
• 9 claude.exe processes observed simultaneously consuming ~2GB RAM
• System free memory dropped to ~49MB during multi-session use
• Workaround: keep only one session tab open at a time