Model Selection Resets in Agents UX

[ElliotChong-MS]

Type: Bug

Window: Agents

When using the Agents UX embedded within VS Code, sessions connected to Copilot CLI intermittently switch to a different model than the one originally selected.

Example:

• Start a session with Opus 4.7
• Dispatch a task to the agent
• Return later to the session
• The selected model has changed (e.g., now shows Sonnet 4.6)

Expected behavior:
The session should persist and display the originally selected model unless explicitly changed by the user.

Actual behavior:
The model selection appears to reset or switch without user action.

VS Code version: Code - Insiders 1.120.0-insider (Universal) (70b1a96, 2026-05-11T18:12:37-07:00)
OS version: Darwin arm64 24.6.0
Modes:

System Info

Item	Value
CPUs	Apple M1 Max (10 x 2400)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M1 Max, Version 15.7.5 (Build 24G624))], DRIVER_VENDOR=Apple, DRIVER_VERSION=15.7.5 ACTIVE Machine model name: MacBookPro Machine model version: 18.2 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: enabled_on trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	15, 17, 16
Memory (System)	64.00GB (0.19GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions (7)

Extension	Author (truncated)	Version
markdown-mermaid	bie	1.32.0
mermaid-markdown-syntax-highlighting	bpr	1.8.0
auto-close-tag	for	0.5.15
output-colorizer	IBM	0.1.2
vscode-remote-extensionpack	ms-	0.26.0
indent-rainbow	ode	8.3.1
vscode-todo-highlight	way	1.0.5

(1 theme extensions excluded)

[Chulong-Li]

Thanks for reporting this issue! I opened a PR that should fix this: #316876.

From my testing, the selected model is now preserved for Copilot CLI sessions, so cases like starting with GPT-5.5 or Opus 4.7 should no longer switch to Claude Sonnet 4.6 Medium during startup or processing.

@lostintangent @DonJayamanne Since this touches the Agent Host session startup/model-selection flow, would you be able to take a look when convenient?