It is written in the explainer (not currently in the seller guide) that top-level auctionSignals, when component sellers exist, are not shared with any buyer. We've been told if the top-level auction runner wants to share a signal with each component buyer, they should re-write the component sellers' auctionSignals objects to include it. This feels awkward.

Why even have top-level level auctionSignals exist in the component workflow? There doesn't seem to be an obvious consumer of it.

Why not just have top-level auction signals do a json merge with component signal auctionSignals? Or perhaps, in component auctions, toplevelAuctionSignals and auctionSignals could both be exposed to buyers as different objects? Or perhaps, a third signals object (beyond auctionSignals and sellerSignals) could be added to the top level, that is explicitly for component buyers, eg componentAuctionSignals?

It seems any of these solutions is more elegant than the toplevel seller being responsible for awkward re-writes of contributed component seller config.

Use cases: (1) the ad server is running the top-level auction and has information to share with each component buyer, for example, the price of the contextual winner, a publisher-provided signal (aka seller-defined audience), visibility indicator, or a calculated floor.

(2) the publisher is running the top-level auction and wants to share their banned advertisers, categories, floors, or contextual signals with each buyer but is not running any component auction.

(3) the top level seller can take responsibility for propagating / validating the structure or contents of certain page level descriptions, eg referer, and forming them into a, for example, openrtb or openrtb like request object. This third use case would make it so component sellers aren't competing on things like page description standards adherence and should be good for all parties in the transaction.