One use of isCompatibilityMode today is in the getDefaultLimitsForAdapter helper function in the CTS. We'll need to figure out if there's a good alternative that doesn't require it.

IIRC the CTS assumes if you pass in the "compatibility" flag to the CTS, then it requests compat adapters and expects it got compat adapters. It doesn't check the adapter itself. It just assumes via globalTestConfig.compatibility

I'm not sure that can really change. The CTS needs to test devices that are actually running in compatibility mode.

ps: if that wasn't clear. I meant to say that getDefaultAdapterLimits is effectively passed globalTestConfig.compatibility, not any info from the adapter.

And, I'm wrong. I guess I don't remember this part of the code 😅

Np, but maybe we can change it to use that strategy instead. Depends on exactly how we use that helper function.

For the record, linking related point: #5012 (comment)

I strongly feel that items should only be in GPUAdapterInfo if they also apply to the device, because we expose device.adapterInfo. That's true of vendor/etc., and of isFallbackAdapter (so indeed it probably should be duplicated there), but not features/limits. Similarly it is not necessarily true of featureLevel, because whether the device is "compatibility mode" depends on what features/limits are enabled on it. This is another reason I don't really think we should expose something like adapter.isCompatibilityMode/adapter.featureLevel and should instead expose it via the features system. Example:

I'm going to flatten this into #5036 while updating it, since the WG discussed all together.