Cboe Splits Market Protections: Session-by-Session Trading Tweak
Published Date: 3/31/2026
Notice
Summary
Cboe Exchange is updating its rules to apply its wide market protection separately for each trading session, like regular hours or after-hours. This change helps keep trading fair and smooth throughout the day for all traders. It’s effective immediately, so market participants should be ready for this new way of protecting trades during different sessions.
Analyzed Economic Effects
3 provisions identified: 2 benefits, 1 costs, 0 mixed.
Wide Market Protection Applied Per Session
Cboe will apply its wide market protection mechanism separately for each trading session (Regular Trading Hours, Global Trading Hours, and Curb Trading Hours) under amended Rule 5.34(a)(5). The mechanism can now be turned on or configured for each session and is effective immediately after the Exchange filed the change on March 20, 2026.
Session-Specific NBBO 'Wide' Thresholds
The Exchange may set the NBBO width threshold used to determine when the NBBO is considered “wide” on a trading session-by-trading session basis (in addition to class-by-class), as reflected in the amendment to Rule 5.34(a)(5)(A)(i). When the NBBO is deemed wide, the Exchange may initiate drill-through pauses for applicable inbound market or limit orders and elected Stop or Stop-Limit orders.
No Protection Just Before RTH/Curb Close
The wide market protection mechanism will continue to not apply during a predetermined amount of time prior to the close of the Regular Trading Hours and Curb trading sessions (the Exchange will determine that time), consistent with language moved into Rule 5.34(a)(4)(D). This scheduling detail is part of the Exchange's consolidated session rules.
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