`URI::InvalidURIError` crash from VS Code extensions using custom URI schemes (e.g. Claude Code)

[zerocool4u2]

Description

Description

Hi, I'm having trouble with Claude Code when using VS Code as my IDE with the ruby-lsp extension. Every time Claude suggests a code change (which opens an inline diff view), it crashes my ruby-lsp server. Here's the general problem:

VS Code extensions that register custom document URI schemes can crash the ruby-lsp server. The Claude Code extension uses _claude_fs_right: and _claude_fs_left: schemes for inline diff views. These have a leading underscore, which is invalid per RFC 3986 §3.1 (schemes must start with a letter).

The crash occurs in two code paths:

1. Main thread (base_server.rb:51): URI(uri) raises URI::InvalidURIError, but the begin/rescue only catches Store::NonExistingDocumentError. The unrescued exception kills the server (exit code 1).

2. Worker thread (server.rb run_combined_requests): Feature handlers call URI() independently, crashing the worker thread.

Once the server dies, all requests fail with "Connection is disposed."

Ruby LSP Information

VS Code Version

1.116.0

Ruby LSP Extension Version

0.8.12

Ruby LSP Server Version

0.26.9

Ruby LSP Addons

Ruby Version

3.4.8

Ruby Version Manager

rvm

Installed Extensions

Click to expand

• Bookmarks (14.1.1)
• EditorConfig (0.18.2)
• LogFileHighlighter (3.5.1)
• better-comments-2 (2.1.0)
• claude-code (2.1.109)
• code-spell-checker (4.5.6)
• codesnap (1.3.4)
• debugpy (2025.18.0)
• dotenv (1.0.1)
• elixir-ls (0.30.0)
• git-graph (1.30.0)
• gitignore (0.10.0)
• gitlens (17.12.0)
• go (0.52.2)
• haml (1.4.1)
• headwind (1.7.0)
• latex-support (3.10.0)
• latex-workshop (10.14.1)
• markfiles (1.1.4)
• phoenix (0.1.3)
• pinboard (0.0.28)
• prettier-vscode (12.4.0)
• python (2026.4.0)
• rails-routes (0.6.3)
• rails-snippets (1.0.8)
• remote-containers (0.447.0)
• ruby-lsp (0.8.12)
• solargraph (0.25.0)
• sql-formatter-vsc (4.2.5)
• svg (1.5.4)
• transpose (0.0.6)
• vscode-better-align (1.4.5)
• vscode-containers (2.4.1)
• vscode-docker (2.0.0)
• vscode-erb-beautify (0.5.0)
• vscode-eslint (3.0.24)
• vscode-github-actions (0.31.3)
• vscode-kubernetes-tools (1.3.29)
• vscode-latex (2.0.0)
• vscode-markdownlint (0.61.2)
• vscode-postcss-sorting (3.0.1)
• vscode-pylance (2026.2.1)
• vscode-settings-cycler (1.0.1)
• vscode-sort-json (1.20.0)
• vscode-tailwindcss (0.14.29)
• vscode-yaml (1.21.0)
• vscode-yaml-sort (6.6.4)

Ruby LSP Settings

Click to expand

Workspace

{}

User

{
  "enableExperimentalFeatures": false,
  "enabledFeatures": {
    "codeActions": true,
    "diagnostics": true,
    "documentHighlights": true,
    "documentLink": true,
    "documentSymbols": true,
    "foldingRanges": true,
    "formatting": true,
    "hover": true,
    "inlayHint": true,
    "onTypeFormatting": true,
    "selectionRanges": true,
    "semanticHighlighting": true,
    "completion": true,
    "codeLens": true,
    "definition": true,
    "workspaceSymbol": true,
    "signatureHelp": true,
    "typeHierarchy": true
  },
  "featuresConfiguration": {},
  "addonSettings": {},
  "rubyVersionManager": {
    "identifier": "rvm"
  },
  "customRubyCommand": "",
  "formatter": "rubocop",
  "linters": null,
  "bundleGemfile": "",
  "testTimeout": 30,
  "branch": "",
  "pullDiagnosticsOn": "both",
  "useBundlerCompose": false,
  "bypassTypechecker": false,
  "rubyExecutablePath": "",
  "indexing": {},
  "erbSupport": true,
  "useLauncher": false
}

Reproduction steps

1. Have a Ruby project with ruby-lsp in the Gemfile
2. Open the project in VS Code with the Ruby LSP extension active
3. Install the Claude Code VS Code extension, or start claude in an external terminal and run /ide to connect it to VS Code
4. Ask Claude to make a code change to any Ruby file — it opens an inline diff view using _claude_fs_right: / _claude_fs_left: URI schemes
5. Ruby LSP server crashes with exit code 1
6. All LSP features stop working with "Connection is disposed" errors

Code snippet or error message

# Main thread crash (kills the server):
/gems/ruby-lsp-0.26.9/lib/ruby_lsp/base_server.rb:51:in 'block (2 levels) in RubyLsp::BaseServer#start'
URI::RFC3986_Parser#split: bad URI (is not URI?): "_claude_fs_right:/path/to/file.rb" (URI::InvalidURIError)
    from uri-1.1.1/lib/uri/rfc3986_parser.rb:130:in 'URI::RFC3986_Parser#split'
    from uri-1.1.1/lib/uri/common.rb:915:in 'Kernel#URI'
    from ruby-lsp-0.26.9/lib/ruby_lsp/base_server.rb:51

# Worker thread crash (separate code path):
URI::RFC3986_Parser#split: bad URI (is not URI?): "_claude_fs_right:/path/to/file.rb" (URI::InvalidURIError)
    from ruby-lsp-0.26.9/lib/ruby_lsp/server.rb:449:in 'RubyLsp::Server#run_combined_requests'
    from ruby-lsp-0.26.9/lib/ruby_lsp/server.rb:32:in 'RubyLsp::Server#process_message'
    from ruby-lsp-0.26.9/lib/ruby_lsp/base_server.rb:181:in 'RubyLsp::BaseServer#handle_incoming_message'

Suggested Fix

Add rescue URI::InvalidURIError to the existing begin/rescue in base_server.rb:

# base_server.rb - inside the begin/rescue block in #start
+           rescue URI::InvalidURIError
+             # Skip URIs with unsupported schemes (e.g. custom VS Code document providers)
            rescue Store::NonExistingDocumentError
              # If we receive a request for a file that no longer exists, we don't want to fail

And guard process_message in server.rb to reject unparseable URIs early:

# server.rb
  def process_message(message)
+   uri = message.dig(:params, :textDocument, :uri)
+   if uri.is_a?(String)
+     begin
+       URI(uri)
+     rescue URI::InvalidURIError
+       id = message[:id]
+       send_message(Result.new(id: id, response: nil)) if id
+       return
+     end
+   end
+
    case message[:method]

Workaround

A project-local addon that patches Kernel#URI and Server#process_message at runtime. Place at ruby_lsp/claude_code_uri_fix/addon.rb:

Click to expand

# frozen_string_literal: true

module RubyLsp
  module ClaudeCodeUriFix
    module KernelUriPatch
      def URI(uri)
        super
      rescue ::URI::InvalidURIError
        raise unless uri.is_a?(String) && uri.start_with?("_claude_fs_")
        raise ::RubyLsp::Store::NonExistingDocumentError, uri
      end
    end

    module ServerPatch
      def process_message(message)
        uri = message.dig(:params, :textDocument, :uri)
        if uri.is_a?(String) && uri.start_with?("_claude_fs_")
          id = message[:id]
          send_message(Result.new(id: id, response: nil)) if id
          return
        end
        super
      end
    end

    class Addon < ::RubyLsp::Addon
      def activate(_global_state, _outgoing_queue)
        ::Kernel.prepend(KernelUriPatch)
        ::RubyLsp::Server.prepend(ServerPatch)
      end

      def deactivate; end
      def name = "Claude Code URI Fix"
      def version = "1.0.0"
    end
  end
end

[vinistock]

Thanks for the bug report! Do you have any configuration either for Claude code or the Claude extension?

If I edit the code using Claude, I can see the diffs with no crashes.

[zerocool4u2]

Hi!, nothing configured on the claude extension, I just have it for IDE integration. I do use claude code by executing it in the terminal on the terminal panel, not on the claude code panel from the extension, do you think that might be the difference? Other custom things I have are zsh, and rvm with a gemset for my project, but nothing crazy. I'm also using an M1 mac

[vinistock]

That's the same workflow I've been using with Claude running in the VS Code integrated terminal and not its own panel. Honestly, I'm not sure what's going on.

Do you happen to have Claude itself running the Ruby LSP as a tool? Or is the LSP only connected to VS Code?

I would assume the former might cause issues like these since Claude is interacting directly with the language server. For the latter, I would assume that the Claude extension uses the VS Code API to open a file diff, which would mean that VS Code itself would be sending the textDocument/didOpen requests and it wouldn't allow for an invalid URI.

[zerocool4u2]

Do you happen to have Claude itself running the Ruby LSP as a tool? Or is the LSP only connected to VS Code?

just VS Code. I don’t know how Claude interacts with the IDE, I just do /ide and select it when it happens to disconnect. Maybe I do have something different in my setup. I switched back from Cursor to VS Code a couple of weeks ago, and the issue started for me last week, around when I updated my gems, so naturally I thought it was related to either a release in ruby-lsp or Claude itself, which gets updates every day 😂

If the issue is just happening to me, I can just close the ticket. The workaround I have isn’t intrusive to my day-to-day work

[vinistock]

It could be a real bug, but at the moment we haven't understood the root cause and so there's no way to determine what's behind it. Ideally, if there's a way that we can reproduce it, then we can do a deeper investigation into it, but so far I haven't been able to.