Enable `window.autoDetectColorScheme` by default

[joaomoreno]

It would be fantastic if VS Code would switch themes automatically by default. We could do some migration:

• If a user doesn't have a theme configured, or they have any of the Light* or Dark* themes configured, we would automatically onboard them to autoDetectColorScheme: true.
• Otherwise, we'd set autoDetectColorScheme: false.

[vs-code-engineering]

Hi @joaomoreno. As a member of the team, you can help us triage this issue by referring to https://github.com/microsoft/vscode-copilot/wiki/Copilot-Inbox-Tracker and assigning an owner directly.

[joaomoreno]

From @isidorn:

@joaomoreno thanks! And what would be the default out of the box?

I know @bpasero has concerns if we respect the OS setting we would change to light theme on macOS. But that might be fine? What is the default theme on windows?

[joaomoreno]

Funny how our website already does this:

Screen.Recording.2025-09-23.at.09.49.13.mov

[joaomoreno]

From @joaomoreno:

Current defaults are light for web, dark otherwise:

vscode/src/vs/workbench/services/themes/common/themeConfiguration.ts

Line 37 in 79f7310

default: isWeb ? ThemeSettingDefaults.COLOR_THEME_LIGHT : ThemeSettingDefaults.COLOR_THEME_DARK,

[isidorn]

This makes a lot of sense to me. Though it would mean that we change to default to be light theme.
Imho that is fine. But if we want to be on the safe side, we could run an ExP to roll-out (and see if it affects user behaviour).

Speaking of the website, I created this one https://github.com/microsoft/vscode-website/issues/2335

[bpasero]

I would not suggest to do this. We have shipped with dark theme ever since, and that would mean changing the default to light theme on macOS at least.

If we could detect that "Auto" is configured in this setting on macOS then maybe we could flip the default because thats a good hint that the user cares about changing between dark and light themes in certain conditions:

[joaomoreno]

that would mean changing the default to light theme on macOS at least

Why macOS specifically? I think this would rather mean changing the default to light theme, on all users who (('haven't switched their theme' OR 'are on default themes') AND 'OS prefers light mode').

If we could detect that "Auto" is configured in this setting on macOS then maybe we could flip the default because thats a good hint that the user cares about changing between dark and light themes in certain conditions:

I really like this idea. I don't think there's a DOM API for it. But there sure is something for macOS:

~ ➜ defaults read -g AppleInterfaceStyleSwitchesAutomatically
1