Nice try franky1. A few posts ago you were not talking about private channels at all, so I assumed that all channels are public, which is the most common case. You are trying to prove me wrong by changing your assumptions. That's no bueno, my dear.
i mentioned private channels as one example, due to your assumption everything is public as if there is a central 'mempool' of channels that everyone has access to. so that in your view commitments can be signed without checking with peers or recipients
i simple used an example of where:
1. its a pass the parcel game not central mempool all users talk with
2. due to not only private channels,(other examples apply) not all channels are passed back to a node (pass the parcel game)
3. parameters do change. EG.. if alice knows of ABCDE. in them few minutes because she is only a few hops away, her data is not accurate. when she tries she gets a error and the node then updates with its actual stuff.
i would have mentioned many other examples, but seeing as for pages of posts you have had particular issues getting yourself out of the direct payment to channel partner scenario.. i thought i would take things slowly on you. give you a chance to gently come out of your box.
EG one step, realise its not just commitment signings but actually lots of messages
EG two step, messages are in msat and not blockchain formatted transaction templates
EG three step, not all nodes psychicly know everything when they open the app or minutes/hours later(things change)
EG four step, show more messages and scenarios that contravene your commitment signing thoughts of how LN work
your fluctuating between step 2-3, but your trying to pull it back to step minus 0
EG your "update_add_htlc forces commitment update. thinking the only messages are update_add_htlc (again facepalm)
here is something for you to think about outside of your box
until an incoming HTLC has been irrevocably committed:
MUST NOT offer the corresponding outgoing HTLC (update_add_htlc) in response to that incoming HTLC.
take a second. and think.
an incoming HTLC. how is that formed(what data is inside this incoming htlc).
how is the data in that incoming HTLC collated/determined/checked/viewed before alice sends it to bob
(before bob sees it)
yep before alice even sends bob an (incoming to bob) alice needs to do stuff, which requires lots of messages