Where is this post-final challenge player action window coming from? If the final active player has no more available challenges, a strict reading of the timing structure would force the end of phase framework to begin. There is no "next active player" or "next challenge opportunity" at that point (the requirement for the player action window).

Was there an official ruling that I'm missing?

Yes, and a frequent one at that.

The official ruling has clarified how you are supposed to read the timing chart. You keep following the "Active Player's Next Challenge Opportunity" arrow back to the "pre-challenge" player action window, no matter how many challenges they have already initiated that phase. So, for example, the final active player does not have to play their Citadel Politics event until after they have initiated their 3 standard challenges for the phase. It's not until the active player says "no challenge" that you jump down to the framework window that starts with "Active Player is finished with challenges."

FFG has clarified and ruled on this many times. It's not a "play by convention" mentality; it's FFG's rules/policy.

And yeah, to reiterate what duolos2k says: you are misunderstanding the way challenges are initiated if you think a player can say "I do my military challenge, but I declare no attackers." A challenge cannot be initiated unless you both call the challenge type and kneel an attacking character. As the rules say "You must declare at least one attacking character to initiate a challenge," meaning that if you do not declare at least one attacking character, the challenge doesn't "fizzle," it NEVER EXISTED. Declaring 3 challenges per phase is optional, not mandatory.

Where?

Where?

Send it to FFG for a personal "where" if you'd like. Or search the forums.

Does that mean it's not officially stated somewhere in the rules or FAQ that there is a player action window after the final challenge (even in the examples)?

This is clearly an interpretation issue and that's all of the guideline that FFG has provided that I'm aware of. The question is - when does the Active Player declare "No more challenges?" Does the AP bypass the loop and go straight to the no more challenges framework or does the loop ALWAYS occur and then when it's time to declare a challenge the AP says no more challenges - which then jumps you to the end of challenges framework?

Seems both could be true. The guidance we've been given is that the latter is true. The loop back ALWAYS occurs regardless of the number of challenges the AP makes because there is no way to know if the AP has a card effect that would allow them to make yet another challenge, so you have to assume they will make another one until they say they have no more to make.

So, no, no FAQ entry, but guidance to how the flowchart is interpreted. For most of us... this is acceptable. If you don't think it is - then take ktom's advice and take it up with FFG.

Does that mean it's not officially stated somewhere in the rules or FAQ that there is a player action window after the final challenge (even in the examples)?

Depends on how you look at it. FFG's stance is that it is , in fact, in the FAQ on the flow chart. So it is "officially stated" in the rules and/or FAQ and all of the "rulings" they have made have really only been clarifications on how the flowchart is supposed to be read. So it isn't stated word-for-word "there is a player action window after each challenge," but there is an arrow on the flow chart you are supposed to follow to a player action window after each challenge resolves.

Bolzano was nice enough to find a post/email from Nate illustrating this. Note that it is exactly what we have been saying - a "clarification" on how to read the FAQ as it already exists.