TXSE to Introduce SEED Self-Match Enhancement and Two OPTIONAL FIX CONFIGURATION ENHANCEMENTS Related to Execution Reports and Drop Copy

Dear Member,

TXSE will introduce enhancements to its SEED protocol and two OPTIONAL FIX configuration enhancements in the UAT environment on Thursday, August 20, 2026, with production deployment planned for Monday, August 31, 2026. Updated technical specifications are now updated on the TXSE website.

1. SEED Enhancement – Self Match Prevention

TXSE is extending SelfMatchPreventionInstruction to SelfMatchPrevented messages on SEED. This change will apply automatically to all SEED users and does not require configuration or activation. Members that plan to use the new field should implement and validate their handling of the updated SelfMatchPrevented message in UAT before the production deployment. For more details on Message Extensibility, please refer to Section 1.2 of the SEED specification.

1. FIX Enhancements — Optional Configurations

The following FIX enhancements are optional and will not be enabled by default. Customers who do not elect to enable these configurations will see no change to their existing FIX Drop Copy behavior.

Customers interested in enabling either configuration should contact marketops@txse.com.

A. Additional ExecutionReport Fields

Customers may elect to enable the following additional fields on FIX ExecutionReport messages:

· UserData (Tag 9002)- included on all ExecutionReport messages.

· SelfMatchPreventionInstruction (Tag 2964)- included on ExecutionReportSelfMatchPrevented messages.

These two enhancements are offered together as a single FIX configuration. At a later date, these fields will become part of the standard FIX implementation and will no longer be optional. Firms should plan to update their FIX applications to accept and process these tags. TXSE will provide additional notice prior to making this functionality mandatory.

B. ExecutionReportTrade- Drop Copy Configuration Only

FIX Drop Copy customers may elect to configure their sessions to receive ExecutionReportTrade messages only.

If you have any questions, please contact the TXSE Market Operations team.

Sincerely,

TXSE Market Operations