Copilot-Chat Pane not possible to "Move to new Window" with current session has >1 Window

[DevTKSS]

Type: Bug

Prerequisites:
Monitor Setup I am using:

• 2x (Gawfolk) 2560 x 1440
• 1x (Samsung) 1920 x 1080
  VS Code Application is opened on the smaller one with a .slnx Solution Repo opened where I am working on a PR

What I done:

• opened the Repo

• Explorer Pane Folders as only expanded

• opened 2 Files (./docs/etsy.md + ./samples/Mcp.Client/Controllers/AuthenticationController.cs)

• Explorer Pane Solution Explorer as only expanded (Folders is now collapsed on the bottom)

• drag + droped the etsy.md from the small screen to (the middle) one of the two larger screens, so it created by that a new Window

• Both VS Windows of the session are maximized, but none is in "Compact Mode"

• As the main Instance Window of this session is on the small screen, I decided that I would prefer to have the Copilot (Agent+Auto Model choosage) Chat Pane on the bigger Window / Screen

• Copilot Chat Pane > ...-Button > Click on Move Chat into new Window

  

  and this is the Window Top on the large screen

  

And exactly at this point I got the error of this issue we are talking about:

Log output

2025-11-22 12:52:00.749 [error] [Window] ChatSessionStore: Error reading chat session file 23573900-5bed-4e29-9ffc-5690c355ffe8 Unable to read file 'c:\Users\Sonja\AppData\Roaming\Code\User\workspaceStorage\5e7d612403532f2846184d15a22cc767\chatSessions\23573900-5bed-4e29-9ffc-5690c355ffe8.json' (Error: Unable to resolve nonexistent file 'c:\Users\Sonja\AppData\Roaming\Code\User\workspaceStorage\5e7d612403532f2846184d15a22cc767\chatSessions\23573900-5bed-4e29-9ffc-5690c355ffe8.json')
2025-11-22 12:52:00.749 [error] [Window] Error: Failed to get model for chat editor. resource: vscode-chat-session://local/MjM1NzM5MDAtNWJlZC00ZTI5LTlmZmMtNTY5MGMzNTVmZmU4
    at ZIe.setInput (vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:2216:9184)
    at async rJe.S (vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:697:58520)
    at async rJe.L (vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:697:57080)
    at async rJe.openEditor (vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:697:56162)
    at async vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:809:23355
    at async x1i (vscode-file://vscode-app/c:/Users/Sonja/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:2216:12059)

System information:

VS Code version: Code 1.106.2 (1e3c50d, 2025-11-19T16:56:50.023Z)
OS version: Windows_NT x64 10.0.26200
Modes:

System Info

Item	Value
CPUs	Intel(R) Core(TM) i9-14900K (32 x 3187)
GPU Status	2d_canvas: enabled direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off trees_in_viz: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	63.72GB (45.96GB free)
Process Argv	--crash-reporter-id f663ca38-9d63-4591-9c64-126106c8e367
Screen Reader	no
VM	0%

Extensions (11)

Extension	Author (truncated)	Version
vscode-markdownlint	Dav	0.60.0
gitlens	eam	17.7.1
copilot	Git	1.388.0
copilot-chat	Git	0.33.2
vscode-pull-request-github	Git	0.122.1
csdevkit	ms-	1.80.7
csharp	ms-	2.100.11
dotnet-maui	ms-	1.11.215
vscode-dotnet-runtime	ms-	2.3.7
vscode	uno	0.23.6
markdown-all-in-one	yzh	3.6.3

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