Code Generation Instructions Not Working in Dev Containers

[serialprimate]

Type: Bug

1. Set a file for github.copilot.chat.codeGeneration.instructions
2. Verify working outside of dev container
   • see file in chat's used references drop-down
   • ask copilot about its instructions: success
3. Verify not working inside dev container
   • see setting and cog icon in chat's used references drop-down
   • ask copilot about its instructions: fails, discusses system prompt only

VS Code version: Code 1.101.0 (dfaf441, 2025-06-11T15:00:50.123Z)
OS version: Windows_NT x64 10.0.26100
Modes:
Remote OS version: Linux x64 5.15.167.4-microsoft-standard-WSL2

System Info

Item	Value
CPUs	Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz (12 x 2904)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on 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 video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	31.74GB (17.03GB free)
Process Argv	--folder-uri=vscode-remote://wsl+Ubuntu-24.04/home/matt/dev/test --remote=wsl+Ubuntu-24.04 --crash-reporter-id 05dfa3f3-d27e-4628-9552-acb212ea8a1f
Screen Reader	no
VM	0%

Item	Value
Remote	Dev Container: Full-Stack Development
OS	Linux x64 5.15.167.4-microsoft-standard-WSL2
CPUs	Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz (12 x 0)
Memory (System)	15.49GB (13.43GB free)
VM	0%

Extensions (5)

Extension	Author (truncated)	Version
remote-containers	ms-	0.417.0
remote-wsl	ms-	0.99.0
errorlens	use	3.26.0
copilot	Git	1.335.0
copilot-chat	Git	0.28.0

A/B Experiments

vsliv368:30146709
vspor879:30202332
vspor708:30202333
vspor363:30204092
vscod805:30301674
binariesv615:30325510
c4g48928:30535728
azure-dev_surveyone:30548225
962ge761:30959799
2e7ec940:31000449
pythontbext0:30879054
cppperfnew:31000557
dwnewjupyter:31046869
pythonrstrctxt:31112756
nativeloc1:31192215
5fd0e150:31155592
dwcopilot:31170013
6074i472:31201624
dwoutputs:31242946
customenabled:31248079
9064b325:31222308
copilot_t_ci:31222730
e5gg6876:31282496
pythoneinst12:31285622
bgtreat:31268568
4gafe986:31271826
c7cif404:31314491
pythonpulldiag:31325930
996jf627:31283433
pythonrdcb7cf:31303019
usemplatestapi:31297334
0aa6g176:31307128
7bj51361:31289155
747dc170:31275177
aj953862:31281341
generatesymbolt:31295002
convertfstringf:31295003
pylancequickfixf:31329273
0g0a1943:31327026
useunpkg:31328953
1292j425:31329156
4f60g487:31327383

[serialprimate]

I retested this bug and it reliably happens (i.e. fails) even with this trivial devcontainer.json:

{
    "name": "Ubuntu Test Container",
    "image": "ubuntu:latest",
    "customizations": {
        "vscode": {
            "extensions": [ ]
        }
    }
}

[serialprimate]

Problem solved -- somehow github.copilot.chat.codeGeneration.instructions was overridden in the local machine settings each time. I don't understand how this happened especially in the trivial case of my last comment.