alt Hacker NewsYes, I agree with your point and article regarding hidden or sealed state.
So, I'm aware that this is a separate point from the article, and I'm well aware of Pi's model abstraction layer, which is one of the best (others are a big pain... looking at you LangChain). I've come to the conclusion that full session portability will come to an end very soon, and really already has. Partially because of the hidden state stuff, partially because of feature divergence. We can still kinda patch over it right now, but it's getting harder by the week. Some examples: computer use structures in OAI responses, until recently MCP tunnels were only supported by OAI, not Anthropic, and tool discovery/search API is also getting very difficult to model fully in a unified abstraction (still possible as you point out), automatic compaction is also getting gnarly, etc.
It definitely is getting quite challenging. That said, a lot of user experiences are modelled around retaining transcripts for longer than a few minutes. Every claw or chat based application creates a very real user experience desire of that conversation being something you can continue, even weeks after when the model might have gone away / have been replaced.
Now unless you fully want to commit yourself to one provider, you will on the application layer need to deal with this anyways in one form or another. We want to at least try to address most of this on the harness layer, regardless of how tricky that is.