TypeError in Svelte Language Server (VS Code Extension)

[lecramr]

Describe the bug

Description:
The Svelte Language Server crashes repeatedly during initialization when working with a multi-app TypeScript monorepo setup. The crash occurs in the TypeScript service cleanup phase (cleanupSemanticCache) due to an undefined registry entry.

Environment

• Svelte Language Server version: svelte.svelte-vscode-109.11.1
• VS Code version: (latest stable at time of issue)
• Node.js version: v22.18.0
• Operating System: macOS
• Project setup: Multi-app monorepo using multiple Svelte and TypeScript configurations

Example:

• /apps/frontend
• /apps/designer
• /apps/qrcode
• /packages/shared

Logs / Stacktrace

Initialize language server at  file:///Users/<username>/Desktop/<projectname>/apps/frontend, file:///Users/<username>/Desktop/<projectname>/apps/designer, file:///Users/<username>/Desktop/<projectname>/apps/qrcode, file:///Users/<username>/Desktop/<projectname>/packages
Initialize new ts service at  /Users/<username>/Desktop/<projectname>/apps/frontend/tsconfig.json
Trying to load configs for /Users/<username>/Desktop/<projectname>/apps/frontend
Loaded config at  /Users/<username>/Desktop/<projectname>/apps/frontend/svelte.config.js
SnapshotManager File Statistics:
Project files: 866
Svelte files: 455
From node_modules: 0
Total: 866
/Users/<username>/.vscode/extensions/svelte.svelte-vscode-109.11.1/node_modules/typescript/lib/typescript.js:143850
  return !!entry.sourceFile;
                 ^

TypeError: Cannot read properties of undefined (reading 'sourceFile')
    at isDocumentRegistryEntry (typescript.js:143850:18)
    at getDocumentRegistryEntry (typescript.js:143926:19)
    at Object.releaseDocumentWithKey (typescript.js:144021:19)
    at typescript.js:152976:65
    at forEach (typescript.js:2305:22)
    at cleanupSemanticCache (typescript.js:152976:7)
    at Object.dispose (typescript.js:152981:5)
    at Object.dispose (service.js:630:25)
    at service.js:962:33
    at async Promise.all (index 0)

Node.js v22.18.0
[Error - 4:49:06 PM] Server process exited with code 1.
[Error - 4:49:06 PM] The Svelte server crashed 5 times in the last 3 minutes. The server will not be restarted.

Reproduction

Example Structure:

• /apps/frontend
• /apps/designer
• /apps/qrcode
• /packages/shared

Expected behaviour

Well, to not crash :)

System Info

Environment

• Svelte Language Server version: svelte.svelte-vscode-109.11.1
• VS Code version: (latest stable at time of issue)
• Node.js version: v22.18.0
• Operating System: macOS
• Project setup: Multi-app monorepo using multiple Svelte and TypeScript configurations

Which package is the issue about?

Svelte for VS Code extension

Additional Information, eg. Screenshots

No response

[jasonlyu123]

Please provide a reproduction repository. This is likely related to the config in your tsconfig.json. Please try to copy it to an empty project to see if you can create a reproduction.

The latest version of the extension may have fixed the startup crash, but it might still occur if you add whitespace to your tsconfig.json and save it.