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The backlog asked what makes a bundle a screen rather than a fragment, and the obvious suspect was the 32-byte header. Swept over all 2859 composable bundles with a real declaration table. The answer to the question is NO, and it is asserted rather than argued: no bit of the flags word at +0x10 labels a screen. The best any bit manages is bit 13 - 403 bundles, 179 of them carrying a full-screen element, a 44% hit rate against a 12.8% base - and the commonest bit is set on 91% of everything. Enrichment, not a marker. The sweep found more than it was asked for, though. The header is not dead space: +0x18 is 1280 on 2829 bundles and +0x1c is 720 on 2823 - the design resolution at bundle level, the same pair the parser already reads out of a .rat record, and asserted here. And +0x04 takes only three values, 0x3C0000 on 2843 and 0x1E0000 on 12, which are exactly 60.0 and 30.0 in 16.16 fixed point, with +0x08 taking 30/1200/120/60 - a frame rate and a duration in frames would fit a format whose records are keyframe lists. That reading is marked amber: it comes from the values alone and is not verified against an animation. Also recorded, since the file will not say: element counts are min 1, median 2, p75 5, p95 23, max 56, and only 365 bundles carry a full-screen element. The population is mostly fragments and the separation is shape. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE