Copilot Chat — Agent mode silently active despite Ask mode selected

Type: Bug

Issue:
When selecting "Ask" mode in the Copilot Chat panel, the session appears to silently continue running in Agent mode for subsequent requests within the same session — even after opening a new chat window. This is not visible from the UI mode selector, which continues to show "Ask" as selected.

Impact:
Agent mode consumes significantly more tokens/premium requests per turn than Ask mode (multiple sequential tool-calling steps vs a single response). Because the mode silently drifts without user awareness, token/credit usage is inflated without any indication in the UI that this is happening.

Workaround found:
Setting "chat.agent.enabled": false in settings.json, followed by a window reload (Developer: Reload Window), forces the session back to Ask-only behavior. This is confirmed via the debug logs (requests return to [panel/unknown]) and a corresponding drop in token usage. Re-enabling the setting and reloading restores Agent mode when genuinely needed.

VS Code version: Code 1.128.0 (fc3def6774c76082adf699d366f31a557ce5573f, 2026-07-07T15:14:24-07:00)
OS version: Windows_NT x64 10.0.26100
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz (8 x 1382)|
|GPU Status|2d_canvas: enabled
GPU0: VENDOR= 0x8086, DEVICE=0x9a49 [Intel(R) Iris(R) Xe Graphics], DRIVER_VENDOR=Intel, DRIVER_VERSION=31.0.101.5333 *ACTIVE*
GPU1: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8521
Machine model name:
Machine model version:
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
webgl: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|undefined|
|Memory (System)|7.75GB (1.14GB free)|
|Process Argv|--crash-reporter-id 6c3cab9b-d339-409e-85f1-43a2079fc31f|
|Screen Reader|no|
|VM|0%|
Extensions (9)

Name|Identifier|Author|Version
---|---|---|---
Tailwind CSS IntelliSense|bradlc.vscode-tailwindcss|bradlc|0.14.29
C# Dev Kit|ms-dotnettools.csdevkit|ms-dotnettools|3.20.199
C#|ms-dotnettools.csharp|ms-dotnettools|2.140.9
.NET Install Tool|ms-dotnettools.vscode-dotnet-runtime|ms-dotnettools|3.1.0
Python Debugger|ms-python.debugpy|ms-python|2026.6.0
Python|ms-python.python|ms-python|2026.4.0
Pylance|ms-python.vscode-pylance|ms-python|2026.2.1
Python Environments|ms-python.vscode-python-envs|ms-python|1.36.0
Live Server|ritwickdey.liveserver|ritwickdey|5.7.10

A/B Experiments

```
vsliv368cf:30146710
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
6abeh943:31336334
envsactivate1:31538736
cloudbuttont:31379625
3efgi100_wstrepl:31403338
ec5jj548:31422691
cp_cls_t_966_ss:31526232
4je02754:31466945
c3h7c220:31478652
ge8j1254_inline_auto_hint_haiku:31490510
38bie571_auto:31478678
cp_cls_t_1081:31454832
conptydll_true:31498968
ia-use-proxy-models-svc:31452481
e9c30283:31461165
test_treatment2:31471001
c9b86496:31447327
capi_bxe_098a3278:31544980
idci7584:31464702
e3e4d672:31494082
ei9d7968:31496641
nes-extended-on:31455476
chat:31457767
8hig5102:31480529
89g7j272:31518289
7e187181:31503455
i2gc6536:31499202
52612955:31516516
ghj88844:31499326
ddid_t:31478206
hmra_i5g22:31518061
ja75b849:31547460
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
db5d2638:31499441
jb_cp_cls_t_632:31543129
b1ei0813:31506238
748c7209:31512887
32d76977:31512328
ha629193:31508444
cdk-lw-on:31524445
f9bf7985:31543584
jh5f2457_c:31540921
api_cot_ctrl:31513533
g4a0e106:31529594
41836166:31537719
prpt_ctrl:31518467
jbcp_cls_pctr_t:31531130
61138546:31518536
cp_intellij_t_nes:31548657
jf4hg949:31526829
nes-curr-leftover-1500:31538366
h561g132:31533256
session_8:31532895
chatquotatrajectorynudge-enabled:31548355
ihg5j128:31534457
jh7i3328:31546038
7g2b5551:31542111
nes-nc-lc-2k:31546583

```