Hi,
I have been a bit busy and out of the loop but did want to take a look at what this meant from the perspective of ara, to see if it broke anything or meant new opportunities.
My full notes and screenshots so far are here but I am giving you a condensed update here.
Everything seems to work with the current latest fallible (2025.3.11). That’s a relief 
ara’s integration tests are passing just the same and I must say I like the newer exception, deprecation and error messages, both in stdout and from a callback perspective, being in separate fields. Nice.
I have tried to measure the performance improvement claim:
Most nested/recursive templating operations are now fully lazy, vastly improving performance in complex scenarios.
From a very naive benchmark that does a debug 10000 times on 100 hosts the performance is about the same:
I would be willing to believe it does not exercise that code path but I would be curious to try something that does.
Do you have an example “nested/recursive templating” somewhere ?
I have tried to find if something like that existed in the integration test targets from the PR but it’s a bit hard to navigate.