Hello API owners,
The speculation rules experiment has been flagged as exceeding the usage limit, presumably due to the private prefetch proxy Early Access Program which uses the feature.
I don't believe this risks burn-in and we should not disable the trial, for the following reasons:
1. The effective usage is likely much lower than the UseCounter suggests. At the moment only certain origins that have opted in can receive prefetch proxy traffic, but this detection happens after the UseCounter for using speculation rules has fired.
Ideally we would have a UseCounter for not only the use of the speculation rules syntax, but for that syntax actually resulting in a connection to the origin server. We can look into that if API owners want (it shouldn't be terribly complicated) but it's not something that exists today.
2. This usage arises from a partner with whom we are coordinating closely and can modify or revert their usage of the feature. This tends to reduce the risk of burn-in, as opposed to usage by a large number of developers who could not make such changes.
3. Unshipping the feature would not break sites. Since this prefetching is a performance enhancement and calling code has no effect in browsers without this shipped, unshipping it even if developers don't remove their usage won't break the web.
4. Disabling the trial would reduce our ability for developers to gather data about the impact of this feature. We'd prefer not to be disruptive if possible.
For these reasons, I believe the OT usage limit to prevent burn-in is inapplicable here and request an exception.