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claude-code - 💡(How to fix) Fix Custom URI scheme _claude_vscode_fs_right breaks C#/Roslyn analyzer (UriFormatException) [2 comments, 2 participants]

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anthropics/claude-code#48966•Fetched 2026-04-17 08:54:31
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The Claude Code VSCode extension's custom filesystem scheme _claude_vscode_fs_right:// causes System.UriFormatException in the C# language server (Roslyn/OmniSharp), breaking IntelliSense and diagnostics.

This is the same root cause as #1522, #21713, #7606, and #3381 — but affecting the C#/Roslyn language server, which has not been reported before.

Error Message

System.UriFormatException: Failed create URI from '_claude_vscode_fs_right:/path/to/workspace/...'

Repeated diagnostic request failures in the Roslyn analyzer whenever Claude Code diff views are active.

Root Cause

The _claude_vscode_fs_right:// URIs leak into workspace/didChangeWatchedFiles LSP notifications broadcast to all language servers. The _ prefix violates RFC 3986 / LSP spec, so any language server that validates URIs throws.

Code Example

System.UriFormatException: Failed create URI from '_claude_vscode_fs_right:/path/to/workspace/...'
RAW_BUFFERClick to expand / collapse

Description

The Claude Code VSCode extension's custom filesystem scheme _claude_vscode_fs_right:// causes System.UriFormatException in the C# language server (Roslyn/OmniSharp), breaking IntelliSense and diagnostics.

This is the same root cause as #1522, #21713, #7606, and #3381 — but affecting the C#/Roslyn language server, which has not been reported before.

Error

System.UriFormatException: Failed create URI from '_claude_vscode_fs_right:/path/to/workspace/...'

Repeated diagnostic request failures in the Roslyn analyzer whenever Claude Code diff views are active.

Root Cause

The _claude_vscode_fs_right:// URIs leak into workspace/didChangeWatchedFiles LSP notifications broadcast to all language servers. The _ prefix violates RFC 3986 / LSP spec, so any language server that validates URIs throws.

Environment

  • VSCode 1.115.0
  • Remote-SSH (Linux host)
  • C# extension with Roslyn analyzer
  • Claude Code VSCode extension (latest)

Impact

  • C# IntelliSense breaks during/after diff views
  • Roslyn analyzer emits repeated diagnostic failures
  • In the observed case, errors started ~3 minutes before a Remote-SSH connection reset (not necessarily causal, but the error spam is disruptive)

Related Issues

  • #1522 — rust-analyzer (closed by inactivity bot)
  • #21713 — rust-analyzer (closed as dup)
  • #7606 — Python LSP (closed as dup)
  • #3381 — Windows variant (still open, 150+ comments)

All closed issues were auto-closed without a fix. The underlying bug persists across multiple language servers.

extent analysis

TL;DR

The issue can be fixed by modifying the Claude Code VSCode extension to use a valid URI scheme that complies with RFC 3986, instead of the current _claude_vscode_fs_right:// scheme.

Guidance

  • Identify the source of the _claude_vscode_fs_right:// URI scheme in the Claude Code VSCode extension and modify it to use a valid scheme.
  • Verify that the modified URI scheme does not cause System.UriFormatException in the C# language server (Roslyn/OmniSharp).
  • Consider filtering out or handling invalid URI schemes in the C# language server to prevent diagnostic failures.
  • Review related issues (#1522, #21713, #7606, #3381) for potential solutions or workarounds that may apply to the C# language server.

Example

No code snippet is provided as the issue does not specify the exact code changes required to fix the problem.

Notes

The issue affects multiple language servers, and a fix may require coordination with the maintainers of the Claude Code VSCode extension and the C# language server.

Recommendation

Apply a workaround by modifying the Claude Code VSCode extension to use a valid URI scheme, as this is the most direct way to address the issue and prevent System.UriFormatException in the C# language server.

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