BOX delays HSVF retransmission rollout for options market data feeds

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BOX delays HSVF rollout

Highlights

BOX Exchange delays HSVF TCP retransmission protocol changes initially set for September 28, 2026, affecting market data feed message handling.
Revised specifications allow data recipients to request retransmissions for messages over sequence number 9,999,999,999 using the RX Retransmission Request Extended message.
Technical updates convert ImprovementProcessExpiryDuration to a filler field in option and complex order messages, requiring firms to update their message processing systems.

Revised deployment timeline and protocol changes

As reported by BOX Exchange, the delayed deployment covers modifications to the High Speed Vendor Feed, or HSVF, and its TCP retransmission capability, which had previously been set to take effect on September 28, 2026. The exchange now says data recipients will gain the ability to submit retransmission requests for messages beyond sequence number 9,999,999,999 by using the existing RX Retransmission Request Extended message.

The RX message will apply in two retransmission scenarios, one covering total HSVF message counts from 1,000,000,000 to 9,999,999,999 and another covering totals from 10,000,000,000 to 999,999,999,999. BOX says additional guidance and examples are included in section 2.5.1, titled "Retransmission Before and After the Billion Message-Mark," of the updated BOX SOLA HSVF Multicast Specifications.

Operational impact for market data users

The exchange says the core HSVF protocol continues to roll over normally and is not affected by the delayed deployment. That means the update is focused on extending retransmission handling for large message volumes rather than changing the underlying rollover behavior.

BOX also says the technical specifications have been revised to convert the ImprovementProcessExpiryDuration field into a filler field in the M, Improvement Process Beginning (Option), and MS, Improvement Process Beginning (Complex Order), messages. For firms consuming BOX market data, the changes require updates to message handling and specification review ahead of the phased rollout.

Our previous coverage of MEMX’s MX2 options exchange fee update explained the planned shift to a new membership fee schedule starting November 2, 2026, subject to SEC filing, with some charges waived until January 1, 2027. It detailed the monthly fees for member categories and the tiered lead market maker pricing tied to prior-month consolidated volume coverage, highlighting the budgeting and planning impact for options participants.

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