BTC 78500 Put OI Surges 125 Contracts, But the Tape Just Flipped to Sellers

BTC 78500P (07SEP26, ~3.3% OTM at spot $81,221) posted the single largest OI build across the entire expiry's strike ladder in the last 24h — +125.6 contracts, more than double the next largest mover (81000P, +122). Cross-referencing the aggressor tape shows the move wasn't a clean directional bet.

Window	Dominant side	Buyer aggression	Net premium
Sep 3, 14:00–22:00	Buyer	~1.00	+$20.6k peak bucket
Sep 4, 08:00–11:00	Seller	0.00–0.21	-$2.4k to -$0.2k

Aggregated over the full 24h window, buyer aggression nets to 0.85, but that's almost entirely front-loaded from Sep 3 evening; the tape has since inverted, with sellers dominating every bucket since Sep 4 08:00 UTC. Across the same expiry, dominant OI flow is labeled "put_buying" in aggregate, yet the strike-level reversal suggests dealers or a single large account are unwinding what looks like it was built via block-adjacent flow rather than retail conviction. Total put delta across the expiry's top strikes hit +539.5 contracts against zero net call delta — a lopsided skew worth tracking into expiry.