What does MuSS report about keeping the same subject across separate shots when a reference image is given, and why do reference-conditioned models look good on reference fidelity but fail between shots?

MuSS (arXiv 2604.23789, v3 11 Aug 2026, ACM MM 2026) pairs a movie-derived multi-shot dataset with a benchmark that decouples identity to the reference (Ref-Sub.Con) from identity between generated shots (Inter-Sub.Con, DINOv2 and InsightFace) and adds ACP-Var and CP-Rate for copy-paste. On 50 Track-2 test items the authors report Phantom 75.16 / 55.20 and VACE-14B 72.10 / 52.40 (Ref / Inter) versus their own EchoShot-based fine-tune 78.50 / 62.27, with CP-Rate 18.50% (Phantom), 21.68% (VACE-14B) and 7.35% (theirs). Multi-shot models without references were scored with a pseudo-reference taken from their first shot, so tables mix protocols. Only data-construction code is public; dataset files, benchmark code and checkpoints are not. Curator qualifications: All reported numbers and quotes verify in the pinned v3 HTML. v1 and v3 report identical Track 2 values; v3 adds the EchoShot implementation detail and the limitations audit (E4 and E6 exist only in v3). The pseudo-reference protocol caveat is confirmed. Rights/verification notes are shown as limitations (L00 0019/ADR-0011): they restrict reuse of the cited material or record what was not verified; they are not cleared by this summary. Limitations: [component_reuse_restriction] Dataset licence pending (README); source clip rights third-party. [component_reuse_restriction] Paper text CC BY 4.0 (arXiv line); code licence not stated. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

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