> But in the background of the article is clearly the goal to make sessions portable, not just being able to inspect it. It's partially implied even in the title.

But not on the level that providers need to agree to a common format. Within Pi we are able to model portable sessions between providers even if they have provider specific APIs. For instance most models do not agree on how to do deferred tool loading. But they now have some support for that even if it diverges between models and APIs. So we can model deferred tool loading specifically for different providers without having to align on a common set of APIs or similar.

What cannot be made portable, is when information is sealed in the transcript or the information is entirely locked away on the provider's servers (store = true).