- SubmitChain rejects NaN/±Inf segment seconds with ErrUnsupported (previously an obscure json.Marshal error; NaN fails every comparison and +Inf passed the >= 0 check). - ChainStatus skips segment entries with no usable id — JSON null (which no-op-unmarshals into a string, previously appending ""), empty strings, and id-less objects; the unfiltered list survives in Raw. ChainJob.SegmentIDs doc now also says ChainSegmentResult takes the segment index, not an id string. - jobPath rejects '%' in job ids — %2F/%2E%2E percent-escapes decode back into path structure server-side, bypassing the literal check on this upstream-echoed value. - singleVideoResult moves to video.go next to videoMIME, and the two remaining hand-rolled copies of the video-result validation (videoModel.Generate, Interpolate) now use it — one validation, one message shape. - videogen.LipSyncer renamed to videogen.Lipsyncer for consistency with the rest of the surface's Lipsync* naming (LipsyncProvider, LipsyncModel, LipsyncRequest); not yet consumed downstream, so the rename is free now and never again. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01WWCQcYStWXBYUy5sZWnbLT