bobmcn

This mirrors my experience also. I want to use embassy, and have tried several times. It gets recommended to me by people whose opinions I trust, so I keep trying. But Zephyr just works.

Why not add an optional arena in the ctx? Then there would be no api break.

This Saturated Fat below 10% requirement is a direct contradiction of the earlier requirements to include more meat and whole fat dairy. You can't do both.

Why not just define a higher level proto that contains all possible (maybe repeated) protos you might want to include? Then if one of the included protos is not present, the higher level proto will efficiently encode that, and nothing gets broken.

I know you mentioned C in your original question, but some of the techniques discussed in low latency presentations at C++ conferences will be broadly applicable. Many are available on line. I have recently watched presentations by Timur Doumler and Fedor Pikus from the last few years that would probably close to what you are looking for.