Workspace Not Loading After Upgrading Theia from 1.66.1 to 1.71.0

[Prayanand]

Question

Hi Eclipse Theia team,

I’m upgrading my custom browser-based code editor from Theia 1.66.1 to Theia 1.71.0.

In my use case, I launch the Theia code editor from my application when the user clicks a button. The application creates a workspace in a local directory, customizes the browser URL with the workspace information, and then launches that workspace in the code editor.

Behavior in Theia 1.66.1

With Theia 1.66.1, the workspace is created and loaded successfully in the code editor, and everything works as expected.

Behavior after upgrading to Theia 1.71.0

After upgrading to Theia 1.71.0, the workspace is still created successfully in the specified local directory, but the workspace is not loaded in the editor. The UI remains stuck on the loading spinner indefinitely.

I don't see any significant errors in the browser console. The only relevant messages I found are:

**default-window-service.ts:108 [Violation] Permissions policy violation: unload is not allowed in this document.
registerUnloadListeners @ default-window-service.ts:108

logger-protocol.ts:118 2026-08-22T12:58:28.566Z root WARN Linked preference "workbench.colorCustomizations" not found.

logger-protocol.ts:118 2026-08-22T12:58:28.566Z root WARN Linked preference "editor.experimental.preferTreeSitter" not found.**

The workspace directory is created correctly, so the issue seems to occur during the workspace loading/initialization phase.

My questions
Are there any changes between Theia 1.66.1 and 1.71.0 related to workspace initialization/loading that could cause this behavior?
Could the unload is not allowed in this document permissions-policy violation prevent the workspace from being loaded?
Are there any changes to the workspace URL format, workspace service, frontend initialization, or browser application configuration that I should consider when upgrading from 1.66.1 to 1.71.0?
Is there any additional logging/debug configuration I can enable to identify why the workspace remains stuck on the loading spinner?
Could the two warnings about workbench.colorCustomizations and editor.experimental.preferTreeSitter be related to the workspace loading issue?

Any guidance on where I should investigate or what changed between these versions would be greatly appreciated.

Thanks!

[github-actions[bot]]

Hi @Prayanand, thanks for starting this discussion! 👋

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• 📖 Theia Documentation
• ❓ FAQ
• 💬 Previous Discussions

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[ndoschek]

Hi @Prayanand,

Thanks for the question.
First, the messages you found are not the cause: the unload is not allowed line is just a deprecated-event warning, and the two Linked preference "..." not found warnings are harmless too. A spinner that never resolves usually means a frontend startup promise (layout or workspace restore) never completes, rather than a thrown error, which is why the console looks clean.

To narrow it down:

1. Check the backend log, not just the browser console.
2. Check the Network tab for a request that stays pending.
3. How do you encode the workspace in the URL? The supported way is the hash fragment, e.g. http://<host>:3000/#/path/to/workspace.

Also, both versions are already fairly old (we released 1.75 yesterday). Is there a reason you are pinned to them? We do not backport to older releases, so I would recommend upgrading to the latest and checking whether it still reproduces. If it does, a minimal reproduction on the browser example would help us investigate. Thanks!