Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.120.0 (main branch, commit 89fc639)
• OS Version: All platforms

Bug

In GettingStartedPage (the Welcome/Walkthrough editor), a configurationService.onDidChangeConfiguration listener for REDUCED_MOTION_KEY is registered inside the onDidProgressStep event callback using this._register(). Each time a walkthrough step is completed, a new permanent configuration listener accumulates in the disposable store and is never cleaned up.

After completing N walkthrough steps across any walkthroughs, N identical onDidChangeConfiguration listeners exist, each toggling the same CSS class on every config change. This grows without bound for the lifetime of the editor.

This is the exact anti-pattern the project's own coding guidelines warn about:

Do NOT register a disposable to the containing class if the object is created within a method that is called repeatedly to avoid leaks. Instead, return an IDisposable from such method and let the caller register it.

Affected code

File: src/vs/workbench/contrib/welcomeGettingStarted/browser/gettingStarted.ts:275

this._register(this.gettingStartedService.onDidProgressStep(step => {
    // ... step handling ...

    // BUG: registered inside event callback, accumulates on every step completion
    this._register(this.configurationService.onDidChangeConfiguration(e => {
        if (e.affectsConfiguration(REDUCED_MOTION_KEY)) {
            this.container.classList.toggle('animatable', this.shouldAnimate());
        }
    }));

    ourStep.done = step.done;
    // ...
}));

Steps to Reproduce

1. Open the Welcome tab (Getting Started page)
2. Complete several walkthrough steps (e.g., toggle "Choose your Theme", "Rich Language Support", etc.)
3. Each step completion fires onDidProgressStep, which registers a new onDidChangeConfiguration listener
4. After completing 10 steps, there are 10 identical config listeners in the disposable store
5. These listeners remain until the Getting Started editor is closed
6. Reopening the Getting Started editor and completing more steps adds more listeners

Impact

• Memory grows linearly with walkthrough step completions
• Each redundant listener runs on every configuration change event, wasting CPU
• Users who explore multiple walkthroughs accumulate dozens of dead listeners

Fix

A PR is available: #314636

The fix moves the onDidChangeConfiguration subscription to the constructor, alongside the other config/event listeners, so it is registered exactly once.