Copilot File Editing Problems

Type: Bug

Using Copilot has some problems when editing source files. It often gets confused and needs to rebuild all files from scratch which results in corrupt builds as too much code needs to be updated. Used GPT-5.4 for the moment.

VS Code version: Code 1.138.0 (Universal) (7debcd0e2acdea1c52de81bf9ee1620444407dda, 2026-09-15T07:24:32Z)
OS version: Darwin arm64 27.0.0
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Apple M5 (10 x 2400)|
|GPU Status|2d_canvas: enabled
GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M5, Version 27.0 (Build 26A428))], DRIVER_VENDOR=Apple, DRIVER_VERSION=27.0 *ACTIVE*
Machine model name: Mac
Machine model version: 17.2
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
webgpu: enabled
webnn: disabled_off|
|Load (avg)|3, 3, 3|
|Memory (System)|32.00GB (0.68GB free)|
|Process Argv|--crash-reporter-id f7417475-8cd5-466d-813b-5be7b3a74acf|
|Screen Reader|no|
|VM|0%|
Extensions (50)

Name|Identifier|Author|Version
---|---|---|---
Better Comments|aaron-bond.better-comments|aaron-bond|3.0.2
Project Manager|alefragnani.project-manager|alefragnani|13.1.0
Tailwind CSS IntelliSense|bradlc.vscode-tailwindcss|bradlc|0.16.0
Toggle Quotes|britesnow.vscode-toggle-quotes|BriteSnow|0.3.6
Path Intellisense|christian-kohler.path-intellisense|christian-kohler|2.10.0
Git History|donjayamanne.githistory|donjayamanne|0.6.20
Prettier - Code formatter|esbenp.prettier-vscode|esbenp|12.4.0
DevTool+|fuzionix.devtool-plus|Fuzionix|0.6.0
Markdown+Math|goessner.mdmath|goessner|2.7.4
Todo Tree|gruntfuggly.todo-tree|Gruntfuggly|0.0.226
Draw.io Integration|hediet.vscode-drawio|hediet|1.9.0
Headwind|heybourn.headwind|heybourn|1.7.0
REST Client|humao.rest-client|humao|0.25.1
AppleScript|idleberg.applescript|idleberg|0.32.2
Typescript React code snippets|infeng.vscode-react-typescript|infeng|1.3.1
Edit CSV|janisdd.vscode-edit-csv|janisdd|0.11.9
SVG|jock.svg|jock|1.5.4
Peacock|johnpapa.vscode-peacock|johnpapa|4.4.1
Rainbow CSV|mechatroner.rainbow-csv|mechatroner|3.24.1
DotENV|mikestead.dotenv|mikestead|1.0.1
autopep8|ms-python.autopep8|ms-python|2026.4.0
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|2026.3.1
Python Environments|ms-python.vscode-python-envs|ms-python|1.36.0
Jupyter|ms-toolsai.jupyter|ms-toolsai|2025.9.1
Jupyter Keymap|ms-toolsai.jupyter-keymap|ms-toolsai|1.1.2
Jupyter Notebook Renderers|ms-toolsai.jupyter-renderers|ms-toolsai|1.3.0
Jupyter Cell Tags|ms-toolsai.vscode-jupyter-cell-tags|ms-toolsai|0.1.9
Jupyter Slide Show|ms-toolsai.vscode-jupyter-slideshow|ms-toolsai|0.1.6
Remote - SSH|ms-vscode-remote.remote-ssh|ms-vscode-remote|0.128.0
Remote - SSH: Editing Configuration Files|ms-vscode-remote.remote-ssh-edit|ms-vscode-remote|0.87.0
C/C++|ms-vscode.cpptools|ms-vscode|1.34.4
Live Preview|ms-vscode.live-server|ms-vscode|0.4.20
Remote Explorer|ms-vscode.remote-explorer|ms-vscode|0.5.0
UUID Generator|netcorext.uuid-generator|netcorext|0.0.5
Ollama|ollama.ollama|Ollama|0.0.9
PlatformIO IDE|platformio.platformio-ide|platformio|3.3.4
R|reditorsupport.r|REditorSupport|2.8.8
R Syntax|reditorsupport.r-syntax|REditorSupport|0.1.4
Live Server|ritwickdey.liveserver|ritwickdey|5.7.10
ES7 React/Redux/GraphQL/React-Native snippets|rodrigovallades.es7-react-js-snippets|rodrigovallades|1.9.3
Ayu|teabyii.ayu|teabyii|1.1.12
vscode-input-sequence|tomoki1207.vscode-input-sequence|tomoki1207|0.2.0
Lorem ipsum|tyriar.lorem-ipsum|Tyriar|1.3.1
Error Lens|usernamehw.errorlens|usernamehw|3.28.0
GistPad|vsls-contrib.gistfs|vsls-contrib|0.9.6
change-case|wmaurer.change-case|wmaurer|1.0.0
Markdown PDF|yzane.markdown-pdf|yzane|2.2.0
Markdown All in One|yzhang.markdown-all-in-one|yzhang|3.6.3

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
envsactivate1:31551504
cloudbuttont:31379625
3efgi100_wstrepl:31403338
bj468946:31457056
ec5jj548:31422691
cp_cls_t_966_ss:31526232
4je02754:31572277
8hhj4413:31478653
ge8j1254_inline_auto_hint_haiku:31490510
cp_cls_c_1081:31454833
conptydll_true:31498968
core-renderer-profiling-on:31440367
e9c30283:31461165
c9b86496:31447327
capico_axe_098a3278:31582664
ei9d7968:31496641
chat:31457767
8hig5102:31480529
89g7j272:31518289
i2gc6536:31499202
52612955:31516516
ddid_t:31478206
hmra_i5g22:31518061
m11_d0di3990:31580636
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
db5d2638:31499441
jb_cp_cls_t_632:31543129
56dj4588:31512888
32d76977:31512328
ha629193:31508444
jh5f2457_c:31540921
jbcp_cls_pctr_t:31531130
cp_intellij_t_nes:31548657
jf4hg949:31526829
ahp-both-windows:31556933
ihg5j128:31534457
7g2b5551:31542111
sandbox-ui-on-2:31543161
enable_editor_pane_layout:31569726
allow-none:31555437
ac562147:31564510
c7c27ce7:31554789
1h923230:31564177
treatment-23-1:31555779
unuse_dynamic_mcp:31555281
0d8dfbc3:31570291
a1hcc538:31559322
0c1h4866:31566224
session-archive:31558132
5b8j3302:31564601
autotiers:31584978
mangle-name-control:31572633
allow-signed-out:31584137
intellij_nes_preview_t:31580086
multiv2:31574985
2bfb8b39:31585911
outline:31581109
aw-autom-on:31583758
revealsession_control_7ed7e840:31582193
4ab0b639:31584543
codex-agent-host-stable-control:31585316
66c8a39e-e7a5-4b4c-a3c0-41b161c795c4:31586113
permission_prompt_treatment:1332566
ccr_pr_nudge_control:1319470
vsc_wsm_c:1340633
cfee5631:1379228
3aced641:1389836

```

Start by reproducing the Copilot editing workflow in VS Code 1.138.0 on macOS with the reported extensions, then inspect the resulting build when source files are rewritten. Done means identifying a repeatable failure and a scoped fix that prevents corrupt builds; the report currently names no source file, entry point, or test.

Written by the indexing model from the issue text.