[jevansnyc]

Summary

• First take of the design spec for issue Support Video in OpenRTB requests #361: linear instream video requested directly through POST /auction, auctioned through standard and prebid-server providers that opt in, and returned as inline VAST to the caller's player.
• Uses the implementation in Support instream video through the auction API #1325 as input for the request contract and admission rules, and restates them in the shape the rest of the auction subsystem uses (validated domain types, explicit bid media, per-provider media opt-in).
• Opened as a draft: round 1 of agent review found blocking issues, which are fixed, and CONTRIBUTING requires another round before review.

Changes

File	Change
docs/superpowers/specs/2026-10-20-361-instream-video-auction-api-design.md	New spec, ending in a review log

Key decisions in the spec:

• Video is off by default. Each provider opts in with media = ["banner", "video"], validated against the media its profile declares. A service with no video provider behaves as main.
• Banner admission keeps every bid main admits, apart from bids that explicitly declare non-banner media.
• VAST is returned byte for byte after a structural check (quick-xml, new dependency).
• A configured mediator plus a video provider is a configuration error.
• First-price requests (at: 1) are a blocking prerequisite, because the caller substitutes ${AUCTION_PRICE} with the returned price.
• PBS video impressions clear every field outside the contract so stored impressions cannot reintroduce them.

Closes

Refs #361. Target design for #1325.

Spec

Spec: docs/superpowers/specs/2026-10-20-361-instream-video-auction-api-design.md

Test plan

• Docs format: Prettier check passes on the spec
• Other: review round 2 in a fresh agent session

Checklist

• Feature PRs: spec linked above, ending in a review log of two or more agent review rounds (one round so far)
• No secrets or credentials committed