What happens on days SPX crosses the zero-gamma flip two or more times?

SPX sessions with two or more flip crossings · 393 sessions · the archive filtered by the dealer book · all sessions · the calendar

393 of 1,103 sessions match. Of them 62% closed above the flip (archive 84%), 19% held the expected-hold band (archive 60%), mean open-to-close move 0.82% (archive 0.60%).

Every row is a finished SPX session and links to its page, where the same numbers stand with the day's events and a free minute-by-minute replay. The filters are the closing measurements those pages print: the zero-gamma flip against the close and the open, the net-gamma percentile, how often the flip was crossed, whether the expected-hold band held, and the calendar event the day carried. The shares above are counts over the matched days next to the same counts over the whole archive; a share that matches the archive is a base rate, not a pattern.

Showing the first 200 of 393; the JSON carries all of them.

Turn a filter into a rule

A count is where a question starts. The Lab takes a rule in plain words ("sell the 0DTE straddle at 10:00 on days that opened below the flip with the percentile under 20"), compiles it against every archived session and reports the out-of-sample verdict with day-clustered intervals. An assistant with the MCP server can page through the same archive with list_sessions and get_session.

Measurements are model output derived from public trade and quote data; they are approximations and can be wrong. Nothing here is investment advice; see the Terms.