| 1.0.0 | 11/16/18 | Initial draft in support of FLEX Options on Cboe Options Exchange. |
| 1.0.1 | 02/14/19 | Added certification environment IP port and unit distribution information. |
| 1.0.2 | 04/02/19 | - Added C1 Certification data center rendezvous point IP address.
- Corrected C1 Symbol Range.
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| 1.0.3 | 04/17/19 | Added Production IP addresses for C1 Options. |
| 1.0.4 | 05/08/19 | - Removed Trading Status field value S = Exchange Specific Suspension from Trading Status message, as this was added in error.
- Corrected C1 Production WAN-Shaped [CAF] and [CBF] source network IP addresses.
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| 1.0.5 | 06/12/19 | - Added additional proprietary products to matching unit 31 in C1.
- Corrected certification and production C1 symbol range for units 9 and 20.
- Corrected example for FLEX Instrument Definition message.
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| 1.0.6 | 06/21/19 | Added Trade(short) message type and example message. |
| 1.0.7 | 09/06/19 | Clarified Price field in Auction Notification message that the field value will be zero when Auction Type = B or F. |
| 1.0.8 | 09/25/19 | Customer Indicator will be blank when Auction Type = F. |
| 1.0.9 | 10/11/19 | - Clarified description of Time message.
- Corrected
Auction Notification Price field description.
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| 1.1.0 | 05/26/20 | - Corrected Unit Symbol Distribution tables to indicate QQQ is an exception for C1 Unit 20, as it has a dedicated location on Unit 28.
- Added DAC Auction Notification and DAC Trade messages (effective 07/20/20 effective 09/14/20 TBD ).
- Added Options Trade Condition Codes section.
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| 1.1.1 | 07/08/20 | Updated effective date for FLEX DAC to 09/14/20. |
| 1.1.2 | 09/08/20 | Updated effective date for FLEX DAC to TBD. |
| 1.1.3 | 11/5/20 | - Added SPESG to Unit Distribution Exception entries.
- Updated effective date for FLEX DAC to 12/2/20.
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| 1.1.4 | 02/01/21 | - Added MRUT to Unit/Symbol Distribution tables for C1 unit 31 (effective 03/01/21).
- Added new updated Unit/Symbol Distribution tables with harmonized symbol ranges (effective 3/22/21).
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| 1.1.5 | 03/25/21 | - Updated the Unit Symbols Distribution Exceptions entries (effective 3/22/21).
- Added Binary Date field type to Section 2.2 - Data Types (effective 10/10/21 TBD 09/27/21 Q3 2021).
- Added new Time Reference message (effective 10/10/21 TBD 09/27/21 Q3 2021).
- Updated description of GTH Trading Status field on Trading Status message (effective 01/24/22 TBD 09/27/21 Q3 2021).
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| 1.1.6 | 05/13/21 | - Clarified that when the system fails to receive two consecutive heartbeat messages within the specified interval the client connection is terminated.
- Updated effective date for Curb session to 02/07/22 TBD 09/27/21.
- Added v=Extended Hours Trade Trade Condition code (effective 01/24/22 TBD 09/27/21).
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| 1.1.7 | 06/15/21 | Updated effective date for extended GTH session to 11/21/21. |
| 1.1.8 | 08/25/21 | Updated Curb session effective date to 02/07/22 TBD. |
| 1.1.9 | 09/09/21 | - Added Trading Status field value L=Curb Trading (C1 Only) for Trading Status messages (effective 01/24/22 TBD).
- GTH Trading Status field will not be used for Curb session.
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| 1.1.10 | 10/01/21 | - Updated effective date for new Time Reference message, EpochTime field to Time message, and Binary Date field type to Section 2.2 - Data Types to 10/10/21.
- Added new section 1.2 - '24x5 Feed Hours and System Restart' (effective 10/10/21).
- Updated Cboe Symbology Reference link.
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| 1.1.11 | 11/04/21` | - Corrected example Time message values.
- Updated Curb session effective date to 02/07/22.
- Updated effective date for v=Extended Hours Trade Trade Condition code to 01/24/22.
- Updated effective date for Trading Status field value ‘ L=Curb Trading' to 01/24/22.
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| 1.1.12 | 02/02/22 | Added NANOS to the C1 unit 32 Unit/Product Distribution tables (effective 03/14/22). |
| 1.1.13 | 11/07/22 | Moved XSP to the C1 unit 32 Unit/Production Distribution table (effective 12/04/22). |
| 1.1.14 | 03/30/23 | Removed past effective dates. |
| 1.1.15 | 01/10/24 | Added ‘E’ value to Complex Instrument Type and Leg Security Type fields in the Complex FLEX Instrument Definition message (effective 04/29/24 03/11/24). |
| 1.1.16 | 01/29/24 | Added MXACW, MXUSA, and MXWLD to unit 31 Unit/Product Distribution tables (effective 03/18/24). |
| 1.1.17 | 03/08/24 | Updated effective date for ‘E’ value addition to Complex Instrument Type and Leg Security Type fields in the Complex FLEX Instrument Definition message to 04/29/24. |
| 1.1.18 | 07/22/24 | Effective 08/26/24, GTH will be extended until 9:25 a.m. ET. |
| 1.1.19 | 09/25/24 | Added NDX and XND to C1 unit 31 symbol range. |
| 1.1.20 | 11/22/24 | Added CBTX, CBTXW, MBTX, and MBTXW to unit 31 Unit/Product Distribution tables (effective 12/02/24). |
| 1.1.21 | 12/13/24 | Added new Unit/Product Distribution for Units 1-30 (effective 03/31/25). |
| 1.1.22 | 01/15/25 | Updated with Cboe Titanium branding. |
| 1.1.23 | 03/25/25 | Added SPEQX to C1 unit 31 unit/product distribution (effective 04/14/25). |
| 1.1.24 | 04/24/25 | Added new message: Symbol Mapping (effective 06/23/25). |
| 1.1.25 | 07/08/26 | Added Time Offset data type. Effective 09/08/25, Time Offset fields will be populated to nanosecond precision. |
| 1.1.26 | 10/20/25 | - Added MGTN and MGTNW to unit 31 in C1 Unit/Product Distribution and excluded MGTN and MGTNW from unit 14 (effective 12/08/25
- TBD 11/17/25). Updated Trading Status Message Fields to remove references to specific products traded during Curb and GTH sessions, replacing it with "Curb-eligible Products" and "GTH-eligible Products", respectively.
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| 1.1.27 | 11/06/25 | Updated MGTN and MGTNW effective date to TBD. |
| 1.1.28 | 11/18/25 | - Updated Price to indicate that Trade price. If instrument trades in percentage terms, then this represents the traded percentage with two implied decimals in Auction Trade.
- Updated Price hexadecimal bytes to 0A 28 00 00 00 00 00 00 in Auction Trade Example messages.
- Updated Trading Status value to 0x31 in FLEX Feed messages.
- Updated Price to $0.00 (not disclosed) for DAC Auction Notification messages.
- Updated Price description to clarify that if instrument trades in percentage terms, then this represents the traded percentage with two implied decimals in Trade (Short) messages.
- Updated MGTN and MGTNW effective date to 12/08/25.
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| 1.1.29 | 01/12/26 | Updated 24x5 Feed Hours and System Restart to document the new time at which persisted orders are added back into the order book (effective 02/02/26). |
| 1.1.30 | 04/01/26 | - Removed references to MXEA, MXEF, MXACW, MXUSA, and MXWLD.
- Updated Time description in Time and Time Reference messages.
- Added XSPBW to C1 unit 32 Unit/Product Distribution tables (effective 06/15/26 06/01/26).
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| 1.1.31 | 04/15/26 | Updated Trading Status to reflect planned expansion of C1 trading hours for select equity options, including the addition of a morning Global Trading Hours (GTH) session and afternoon Curb session, subject to regulatory review (effective 07/13/26 08/17/26 TBD). |
| 1.1.32 | 05/14/26 | - Updated XSPBW effective date to 06/15/26.
- Updated C1 Unit/Product Distribution to include DJXW (effective 05/18/26).
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| 1.1.33 | 06/12/26 | Updated planned expansion of C1 trading hours for select equity options to 08/17/26. |
| 1.1.34 | 07/27/26 | Removed VIX and VIXW exclusion from unit 23 and added VIX and VIXW exclusion to unit 24 C1 Unit/Product Distribution tables. |
| 1.1.35 | 08/10/26 | Updated planned expansion of C1 trading hours for select equity options to TBD. |
