textDocument/formatting fails: 'end' must not be less than 'start'

[mustufaeshaq]

Type: Bug

Issue Description

Steps to Reproduce

Expected Behavior

Actual Behavior

Extension version: 2.140.9
VS Code version: Code 1.128.0 (fc3def6774c76082adf699d366f31a557ce5573f, 2026-07-07T15:14:24-07:00)
OS version: Darwin arm64 25.6.0
Modes:

Logs

C# log

Details

2026-07-08 20:31:12.814 [info] Locating .NET runtime version 10.0.5
2026-07-08 20:31:12.955 [info] Dotnet path: /Users/mustufalakdawala/Library/Application Support/Code/User/globalStorage/ms-dotnettools.vscode-dotnet-runtime/.dotnet/10.0.9~arm64~aspnetcore/dotnet
2026-07-08 20:31:12.955 [info] Activating C# + C# Dev Kit...
2026-07-08 20:31:13.191 [info] info: Program[0]
2026-07-08 20:31:13.191 [info]       Server started with process ID 2859
2026-07-08 20:31:13.806 [info] [Program] Language server initialized
2026-07-08 20:31:13.807 [info] [Program] Monitoring client process 2110 for exit
2026-07-08 20:31:14.023 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in '/Users/mustufalakdawala/Documents/PROJECTS/WEB_APPLICATIONS/BFC' in 4 milliseconds
2026-07-08 20:31:15.605 [info] [serviceBroker/connect] [WorkspaceProjectFactoryService] Project /Users/mustufalakdawala/Documents/PROJECTS/WEB_APPLICATIONS/BFC/BFC.Web/BFC.Web.csproj loaded by C# Dev Kit
2026-07-08 20:50:18.697 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='2000' end='1975'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-08 21:46:20.106 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='6386' end='6361'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-08 21:46:59.839 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='6324' end='6299'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-08 21:48:47.994 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='6167' end='6142'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-08 21:50:47.866 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='6202' end='6177'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-08 21:52:13.831 [info] Locating .NET runtime version 10.0.5
2026-07-08 21:52:13.899 [info] Dotnet path: /Users/mustufalakdawala/Library/Application Support/Code/User/globalStorage/ms-dotnettools.vscode-dotnet-runtime/.dotnet/10.0.9~arm64~aspnetcore/dotnet
2026-07-08 21:52:13.899 [info] Activating C# + C# Dev Kit...
2026-07-08 21:52:14.029 [info] info: Program[0]
2026-07-08 21:52:14.029 [info]       Server started with process ID 7165
2026-07-08 21:52:14.432 [info] [Program] Language server initialized
2026-07-08 21:52:14.434 [info] [Program] Monitoring client process 7102 for exit
2026-07-08 21:52:14.681 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in '/Users/mustufalakdawala/Documents/PROJECTS/WEB_APPLICATIONS/BFC' in 4 milliseconds
2026-07-08 21:52:16.338 [info] [serviceBroker/connect] [WorkspaceProjectFactoryService] Project /Users/mustufalakdawala/Documents/PROJECTS/WEB_APPLICATIONS/BFC/BFC.Web/BFC.Web.csproj loaded by C# Dev Kit
2026-07-08 21:52:37.001 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='6202' end='6177'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-09 12:40:17.142 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='2098' end='2073'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-09 12:44:55.193 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='2001' end='1976'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-09 14:40:39.754 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='4255' end='4230'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-09 17:02:53.113 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='4255' end='4230'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-09 17:13:51.998 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='4258' end='4233'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-10 12:16:19.856 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='4153' end='4128'. (Parameter 'end')
  Code: -32000 
[object Object]
2026-07-10 13:08:08.743 [error] Request textDocument/formatting failed.
  Message: 'end' must not be less than 'start'. start='4217' end='4192'. (Parameter 'end')
  Code: -32000 
[object Object]

C# LSP Trace Logs log

Details

Environment Information

VSCode version: 1.128.0
C# Extension: 2.140.9
Using OmniSharp: false

Dotnet Information

Host:
Version: 10.0.9
Architecture: arm64
Commit: 901ca94124
RID: osx-arm64

.NET SDKs installed:
No SDKs were found.

.NET runtimes installed:
Microsoft.AspNetCore.App 10.0.9 [/Users/mustufalakdawala/Library/Application Support/Code/User/globalStorage/ms-dotnettools.vscode-dotnet-runtime/.dotnet/10.0.9arm64aspnetcore/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 10.0.9 [/Users/mustufalakdawala/Library/Application Support/Code/User/globalStorage/ms-dotnettools.vscode-dotnet-runtime/.dotnet/10.0.9arm64aspnetcore/shared/Microsoft.NETCore.App]

Other architectures found:
x64 [/usr/local/share/dotnet/x64]
registered at [/etc/dotnet/install_location_x64]

Environment variables:
DOTNET_CLI_UI_LANGUAGE [en-US]
DOTNET_NOLOGO [true]

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Visual Studio Code Extensions

Extension	Author	Version	Folder Name
color-highlight	naumovs	2.8.0	naumovs.color-highlight-2.8.0
csdevkit	ms-dotnettools	3.20.199	ms-dotnettools.csdevkit-3.20.199-darwin-arm64
csharp	ms-dotnettools	2.140.9	ms-dotnettools.csharp-2.140.9-darwin-arm64
dart-code	Dart-Code	3.138.0	dart-code.dart-code-3.138.0
data-workspace-vscode	ms-mssql	0.6.3	ms-mssql.data-workspace-vscode-0.6.3
debugpy	ms-python	2026.6.0	ms-python.debugpy-2026.6.0-darwin-arm64
flutter	Dart-Code	3.138.0	dart-code.flutter-3.138.0
gitlens	eamodio	18.2.0	eamodio.gitlens-18.2.0
material-icon-theme	PKief	5.36.1	pkief.material-icon-theme-5.36.1
mssql	ms-mssql	1.43.0	ms-mssql.mssql-1.43.0
powerplatform-vscode	microsoft-IsvExpTools	2.0.145	microsoft-isvexptools.powerplatform-vscode-2.0.145
prettier-vscode	esbenp	12.4.0	esbenp.prettier-vscode-12.4.0
python	ms-python	2026.4.0	ms-python.python-2026.4.0-darwin-arm64
sarif-viewer	MS-SarifVSCode	3.4.5	ms-sarifvscode.sarif-viewer-3.4.5
sql-bindings-vscode	ms-mssql	0.4.1	ms-mssql.sql-bindings-vscode-0.4.1
sql-database-projects-vscode	ms-mssql	1.6.1	ms-mssql.sql-database-projects-vscode-1.6.1
vim	vscodevim	1.32.4	vscodevim.vim-1.32.4
vscode-codeql	GitHub	1.17.7	github.vscode-codeql-1.17.7
vscode-dotnet-runtime	ms-dotnettools	3.1.0	ms-dotnettools.vscode-dotnet-runtime-3.1.0
vscode-pylance	ms-python	2026.2.1	ms-python.vscode-pylance-2026.2.1
vscode-python-envs	ms-python	1.36.0	ms-python.vscode-python-envs-1.36.0-darwin-arm64

C# Settings

Setting	Value
preferCSharpExtension	false
compilerDiagnosticScope	openFiles
analyzerDiagnosticScope	openFiles
enableXamlTools	true
useServerGC	true

System Info

Item	Value
CPUs	Apple M3 (8 x 2400)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M3, Version 26.6 (Build 25G5057c))], DRIVER_VENDOR=Apple, DRIVER_VERSION=26.6 ACTIVE Machine model name: Mac Machine model version: 15.12 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)	2, 2, 2
Memory (System)	16.00GB (0.06GB free)
Process Argv	--crash-reporter-id 75df1212-d9e5-4c1b-a09d-344c2ed62119
Screen Reader	no
VM	0%

A/B Experiments

vsliv368cf:30146710
pythonvspyt551:31249599
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
6abeh943:31336334
envsdeactivate2:31538737
cloudbuttont:31379625
3efgi100_wstrepl:31403338
ec5jj548:31422691
cp_cls_t_966_ss:31526232
8hhj4413:31478653
cp_cls_c_1081:31454833
conptydll_true:31498968
e9c30283:31461165
test_treatment2:31471001
46204921:31447328
idci7584:31464702
e3e4d672:31494082
ei9d7968:31496641
chat:31457767
7e187181:31503455
ghj88844:31499326
ddid_c:31478207
hmra_i5g22:31518061
ie3bb177:31543534
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
db5d2638:31499441
jb_cp_cls_t_632:31543129
b1ei0813:31506238
56dj4588:31512888
32d76977:31512328
ha629193:31508444
cdk-lw-on:31524445
f9bf7985:31543584
31fi7170_t:31522396
jh5f2457_c:31540921
g4a0e106:31529594
8hfba999:31537718
jbcp_cls_pctr_t:31531130
61138546:31518536
cp_intellij_c_nes:31533503
d7b18187:31526828
h561g132:31533256
sessions_3:31532893
ihg5j128:31534457
jh7i3328:31546038
9gg7f176:31542112
sandbox-ui-on-2:31543161
nes-nc-lc-2k:31546583

[dibarbet]

Could you attach the C# file that triggers this error, or provide a minimal reproduction and C# LSP trace? The formatter input is needed to determine which generated edit has an invalid range.

[dotnet-policy-service]

Closing due to 14 days of inactivity while waiting for more information. If you can provide the requested details, please comment and re-open.