Language server fails to recognize new files added via relative path outside project root

Type: Bug

## Issue Description ##
I have a workspace configured where a csproj file is stored in a different root than the actual source files. I then use a .code-workspace and `` to make the source files visible to the language server. When I create a new source file, VSCode doesn't recognize it properly and I get the error "The active document is not part of the open workspace. Not all language features will be available." Interestingly enough, I have a similar problem when I open my solution in Visual Studio and create a new file. Restarting the entire IDE solves the issue but only until the next file is created.

## Steps to Reproduce ##
[I have my setup on Github.](https://github.com/etkramer/BmSDK/tree/main/bin/BmGame/ScriptsDev)
1. Create a multi-root workspace
```json
{
"folders": [
{
"name": "ScriptsDev",
"path": "."
},
{
"name": "Scripts",
"path": "./../Scripts"
}
]
}
```
2. Write a csproj that includes external files using globbing
```xml

```
3. Now try adding a new .cs file in Scripts. It will show up in VSCode but when you try editing it, the C# extension will show the aforementioned error message.

## Expected Behavior ##
The language server should recognize the newly created file and import it into the project. I should then be able to use all language features without needing to restart VSCode.

## Actual Behavior ##
When I open the new file, I cannot access my dependencies or my own types. Then, the C# extension shows a pop up with this error: `The active document is not part of the open workspace. Not all language features will be available.`

### Logs ###

**Extension version**: 2.140.8
**VS Code version**: Code 1.121.0 (f6cfa2ea2403534de03f069bdf160d06451ed282, 2026-05-19T11:51:53+02:00)
**OS version**: Windows_NT x64 10.0.26100
**Modes**:

### C# log ###

```
2026-05-29 20:32:34.070 [info] Locating .NET runtime version 10.0.5
2026-05-29 20:32:34.196 [info] Dotnet path: C:\Program Files\dotnet\dotnet.exe
2026-05-29 20:32:34.196 [info] Activating C# + C# Dev Kit...
2026-05-29 20:32:34.336 [info] info: Program[0]
2026-05-29 20:32:34.336 [info] Server started with process ID 3712
2026-05-29 20:32:34.999 [info] [Program] Language server initialized
2026-05-29 20:32:35.000 [info] [Program] Monitoring client process 4984 for exit
2026-05-29 20:32:35.859 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in 'c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\ScriptsDev' in 6 milliseconds
2026-05-29 20:32:38.071 [info] [serviceBroker/connect] [WorkspaceProjectFactoryService] Project C:\Program Files\Epic Games\BatmanArkhamCity\BmGame\ScriptsDev\ScriptsDev.csproj loaded by C# Dev Kit
2026-05-29 20:43:37.551 [warning] [textDocument/diagnostic] [LSP] Ignoring diagnostics request for untracked document: file:///c:/Program Files/Epic Games/BatmanArkhamCity/BmGame/Mods/CharacterSwappingScript/scripts/Patches/test.cs
2026-05-29 20:43:37.551 [warning] [textDocument/diagnostic] [LSP] Ignoring diagnostics request for untracked document: file:///c:/Program Files/Epic Games/BatmanArkhamCity/BmGame/Mods/CharacterSwappingScript/scripts/Patches/test.cs
2026-05-29 20:43:37.551 [warning] [textDocument/diagnostic] [LSP] Ignoring diagnostics request for untracked document: file:///c:/Program Files/Epic Games/BatmanArkhamCity/BmGame/Mods/CharacterSwappingScript/scripts/Patches/test.cs
2026-05-29 20:44:21.297 [info] Locating .NET runtime version 10.0.5
2026-05-29 20:44:21.499 [info] Dotnet path: C:\Program Files\dotnet\dotnet.exe
2026-05-29 20:44:21.499 [info] Activating C# + C# Dev Kit...
2026-05-29 20:44:21.668 [info] info: Program[0]
2026-05-29 20:44:21.668 [info] Server started with process ID 15312
2026-05-29 20:44:22.227 [info] [Program] Language server initialized
2026-05-29 20:44:22.239 [info] [Program] Monitoring client process 12200 for exit
2026-05-29 20:44:22.641 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in 'c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\ScriptsDev' in 6 milliseconds
2026-05-29 20:44:22.666 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in 'c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\Scripts' in 2 milliseconds
2026-05-29 20:44:22.675 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in 'c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\Mods' in 8 milliseconds
2026-05-29 20:44:24.798 [info] [serviceBroker/connect] [WorkspaceProjectFactoryService] Project C:\Program Files\Epic Games\BatmanArkhamCity\BmGame\ScriptsDev\ScriptsDev.csproj loaded by C# Dev Kit
2026-05-29 20:44:32.306 [info] [textDocument/diagnostic] [Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager] .NET BuildHost started from c:\Users\Jonkler\.vscode\extensions\ms-dotnettools.csharp-2.140.8-win32-x64\.roslyn\Microsoft.CodeAnalysis.LanguageServer.exe reloading to start from C:\Program Files\dotnet\dotnet.exe to match necessary SDK location.
2026-05-29 20:44:33.160 [warning] [textDocument/diagnostic] [LanguageServerProjectLoader] Project C:\Users\Jonkler\AppData\Local\Temp\roslyn-canonical-misc\c8f30402-aff3-4a4f-b03b-723166e14ed6\Canonical.csproj has unresolved dependencies
2026-05-29 20:44:33.189 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Successfully completed load of c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\Scripts\Test.cs
2026-05-29 20:44:33.206 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.csproj: Running dotnet restore on C:\Users\Jonkler\AppData\Local\Temp\roslyn-canonical-misc\c8f30402-aff3-4a4f-b03b-723166e14ed6\Canonical.csproj
2026-05-29 20:44:33.206 [info] [textDocument/diagnostic] [Microsoft.CodeAnalysis.LanguageServer.DotnetCliHelper] Using dotnet executable configured on the PATH
2026-05-29 20:44:33.745 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.csproj: Determining projects to restore...
2026-05-29 20:44:34.029 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.csproj: Restored C:\Users\Jonkler\AppData\Local\Temp\roslyn-canonical-misc\c8f30402-aff3-4a4f-b03b-723166e14ed6\Canonical.csproj (in 69 ms).
2026-05-29 20:44:34.054 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restore complete
2026-05-29 20:44:34.054 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Completed (re)load of all projects in 00:00:01.9633818
2026-05-29 20:44:34.551 [info] [workspace/didChangeWatchedFiles] [LanguageServerProjectLoader] Successfully completed load of c:\Program Files\Epic Games\BatmanArkhamCity\BmGame\Scripts\Test.cs
2026-05-29 20:44:34.551 [info] [workspace/didChangeWatchedFiles] [LanguageServerProjectLoader] Completed (re)load of all projects in 00:00:00.0060601

```

### C# LSP Trace Logs log ###

```

```

## Environment Information ##
**VSCode version**: 1.121.0
**C# Extension**: 2.140.8
**Using OmniSharp**: false

Dotnet Information
.NET SDK:
Version: 10.0.204
Commit: e7aa4b537d
Workload version: 10.0.200-manifests.e0989437
MSBuild version: 18.3.3+e7aa4b537

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26100
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.204\

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.8
Architecture: x64
Commit: 94ea82652c

.NET SDKs installed:
10.0.204 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 10.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.27 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
DOTNET_CLI_TELEMETRY_OPTOUT [true]
DOTNET_CLI_UI_LANGUAGE [en-US]
DOTNET_MULTILEVEL_LOOKUP [0]

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|
|---|---|---|---|
|catppuccin-vsc|Catppuccin|3.19.0|catppuccin.catppuccin-vsc-3.19.0|
|catppuccin-vsc-icons|Catppuccin|1.26.0|catppuccin.catppuccin-vsc-icons-1.26.0|
|catppuccin-vsc-pack|catppuccin|1.0.2|catppuccin.catppuccin-vsc-pack-1.0.2|
|clang-format|xaver|1.9.0|xaver.clang-format-1.9.0|
|cmake-tools|ms-vscode|1.23.52|ms-vscode.cmake-tools-1.23.52|
|cpp-devtools|ms-vscode|0.5.13|ms-vscode.cpp-devtools-0.5.13|
|cpptools|ms-vscode|1.32.2|ms-vscode.cpptools-1.32.2-win32-x64|
|cpptools-extension-pack|ms-vscode|1.5.1|ms-vscode.cpptools-extension-pack-1.5.1|
|cpptools-themes|ms-vscode|2.0.0|ms-vscode.cpptools-themes-2.0.0|
|csdevkit|ms-dotnettools|3.20.199|ms-dotnettools.csdevkit-3.20.199-win32-x64|
|csharp|ms-dotnettools|2.140.8|ms-dotnettools.csharp-2.140.8-win32-x64|
|csharpier-vscode|csharpier|10.0.3|csharpier.csharpier-vscode-10.0.3|
|even-better-toml|tamasfe|0.21.2|tamasfe.even-better-toml-0.21.2|
|intellij-idea-keybindings|k--kato|1.7.7|k--kato.intellij-idea-keybindings-1.7.7|
|powershell|ms-vscode|2025.4.0|ms-vscode.powershell-2025.4.0|
|uc|EliotVU|0.8.4|eliotvu.uc-0.8.4|
|vscode-dotnet-runtime|ms-dotnettools|3.0.2|ms-dotnettools.vscode-dotnet-runtime-3.0.2|;

C# Settings

|Setting|Value|
|---|---|
|preferCSharpExtension|false|
|compilerDiagnosticScope|openFiles|
|analyzerDiagnosticScope|openFiles|
|enableXamlTools|true|
|useServerGC|true|;

System Info

|Item|Value|
|---|---|
|CPUs|AMD Ryzen 7 3700X 8-Core Processor (16 x 3600)|
|GPU Status|2d_canvas: enabled
GPU0: VENDOR= 0x10de, DEVICE=0x2504 [NVIDIA GeForce RTX 3060], DRIVER_VENDOR=NVIDIA, DRIVER_VERSION=32.0.15.9186 *ACTIVE*
GPU1: VENDOR= 0x10de, DEVICE=0x2504 [NVIDIA GeForce RTX 3060], DRIVER_VERSION=32.0.15.9186
GPU2: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8328
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
webgl2: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|undefined|
|Memory (System)|15.93GB (9.40GB free)|
|Process Argv||
|Screen Reader|no|
|VM|0%|