Coinbase Prime FIX 4.2 → FIX 5.0 SP2 Order Entry Migration Guide

Overview

This guide covers every breaking change and behavioral difference you need to address when migrating your Coinbase Prime FIX integration from version 4.2 to FIX 5.0 SP2. Changes are organized by area so you can work through your codebase systematically.

Biggest Changes

FIX 5.0 SP2 uses a transport-layer split (FIXT.1.1) that separates session-level and application-level protocol versioning. This is the most foundational change and affects your session config before anything else.
We now have published dictionaries. See the FIX 5.0 order entry docs for the detailed specification.
Multiple security type support is the other major structural addition. SecurityType (167) is now required on every outbound order related message:
- Add SecurityType (167) to every NewOrderSingle, OrderCancelRequest, OrderCancelReplaceRequest, and OrderStatusRequest
- For all existing spot orders, set SecurityType = SPOT.
Fill reporting now follows the FIX standard. In FIX 4.2, all fills used ExecType = 1 (Partial Fill) regardless of whether the order was fully complete, and multi-fill orders received OrdStatus = 1 (Partial Fill) on their final fill. FIX 5.0 SP2 corrects both:
- ExecType (150) is now F (Trade) on every fill
- OrdStatus (39) now correctly reflects the true state of the order at the time of each fill — 1 (Partial Fill) while open quantity remains, 2 (Filled) on the final fill

What Has Not Changed

Connection endpoint. FIX 5.0 order entry is serviced at the same URL and port as FIX 4.2: tcp+ssl://fix.prime.coinbase.com:4198
Message types. All message types from FIX 4.2 are present in FIX 5.0. Some have tag and value level changes which are noted in full detail below.

1. Session / Logon (35=A)

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
BeginString (8)	`FIX.4.2`	`FIXT.1.1`	Required change. FIX 5.0 SP2 uses the FIXT transport layer which separates session and application protocol versioning
DefaultApplVerID (1137)	(not set)	`9`	New — required. Must be set alongside `FIXT.1.1` to declare the application version
AccessKey (9407)	API key ID	(remove)	Removed. Tag 9407 is no longer read — remove it from your Logon message
Username (553)	(not set)	API key ID	New — required. Replaces tag 9407 as the field for your API key ID

2. NewOrderSingle (35=D)

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
SecurityType (167)	(not set)	`SPOT` / `FUT` / `PERP`	New — required. Must be present on every order. Use `SPOT` for all existing spot orders
HandlInst (21)	`1` (required)	(remove)	Removed. No longer read by the server. Sending it will not cause a reject but it is not required
TargetStrategy (847)	Required on every order	Only needed for TWAP and VWAP	Omit TargetStrategy (847) for Market, Limit Orders, Stop-Limit and PEG Orders Update TargetStrategy (847) values — update TWAP from `T` to `1001`, and VWAP from `V` to `1`.
Iceberg/display size	MaxShow (210)	DisplayQty (1138)	Replace MaxShow (210) with DisplayQty (1138) for iceberg orders

3. OrderCancelRequest (35=F)

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
SecurityType (167)	(not set)	`SPOT` / `FUT` / `PERP`	New — required. Must be present on every cancel request

4. OrderCancelReplaceRequest (35=G)

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
HandlInst (21)	`1` (required)	(remove)	Removed. No longer read by the server — remove it
SecurityType (167)	(not set)	`SPOT` / `FUT` / `PERP`	New — required. Must be present on every replace request

5. OrderStatusRequest (35=H)

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
SecurityType (167)	(not set)	`SPOT` / `FUT` / `PERP`	New — required. Must be present on every status request

6. ExecutionReport (35=8)

Sent by Prime on fills and order status changes.

Field	FIX 4.2 Value	FIX 5.0 SP2 Value	Notes
SecurityType (167)	(not present)	`SPOT` / `FUT` / `PERP`	New. Now included on all execution reports — ensure your handler does not reject it as an unexpected field
ExecType (150)	`1` (Partial Fill) on all fills	`F` (Trade) on all fills	Breaking change. See fill status behavior below
OrdStatus (39)	`2` (Filled) on single-fill completion; `1` (Partial Fill) on final fill of a multi-fill order	Reflects true order state at time of fill — `1` (Partial Fill) while open quantity remains; `2` (Filled) when fully complete	Breaking change. See fill status behavior below

Fill Status Behavior

This is one of the most significant changes in FIX 5.0 SP2 Execution Reports and affects any code that branches on ExecType or OrdStatus to determine fill state.

ExecType (150)

FIX 5.0 SP2 aligns with the FIX standard — ExecType = F (Trade) is sent on every fill regardless of whether it is the first, intermediate, or final fill of an order.

Scenario	FIX 4.2 ExecType	FIX 5.0 SP2 ExecType
Any fill (partial or complete)	`1` (Partial Fill)	`F` (Trade)

OrdStatus (39)

FIX 5.0 SP2 also changes the final-fill OrdStatus for multi-fill orders. In 4.2, the final fill of a multi-fill order carried OrdStatus = 1 (Partial Fill). In 5.0, OrdStatus always reflects the true state of the order at the time of the fill.

Scenario	FIX 4.2 OrdStatus	FIX 5.0 SP2 OrdStatus
Single fill, order fully complete	`2` (Filled)	`2` (Filled)
Intermediate fill, open quantity remains	`1` (Partial Fill)	`1` (Partial Fill)
Final fill of a multi-fill order	`1` (Partial Fill) ⚠️	`2` (Filled) ✅

How to Detect Fills in FIX 5.0 SP2

# FIX 5.0 SP2 — detect a fill
ExecType (150) == F

# FIX 5.0 SP2 — detect order fully complete
ExecType (150) == F AND OrdStatus (39) == 2

# FIX 5.0 SP2 — detect a partial fill with open quantity remaining
ExecType (150) == F AND OrdStatus (39) == 1

7. Migration Checklist

Session / Logon

Set BeginString = FIXT.1.1
Set DefaultApplVerID = 9
Move API key from AccessKey (9407) → Username (553)

NewOrderSingle (35=D)

Add SecurityType (167) to every order (SPOT for existing spot orders)
Remove HandlInst (21)
Replace MaxShow (210) with DisplayQty (1138) on iceberg orders
Market orders: Remove TargetStrategy (847) = M
Limit orders: Remove TargetStrategy (847) = L
TWAP orders: Change TargetStrategy (847) from T → 1001
VWAP orders: Change TargetStrategy (847) from V → 1
Stop-Limit orders: Remove TargetStrategy (847) = SL
PEG orders: Remove TargetStrategy (847) = P

OrderCancelRequest (35=F)

Add SecurityType (167)

OrderCancelReplaceRequest (35=G)

Remove HandlInst (21)
Add SecurityType (167)

OrderStatusRequest (35=H)

Add SecurityType (167)

ExecutionReport (35=8)

Handle new SecurityType (167) field — ensure your handler does not reject it as unexpected
Handle new Fill detection and status changes

REST API

Websocket Feed

FIX 4.2 API

FIX 5.0 API

Coinbase Prime FIX 4.2 → FIX 5.0 SP2 Order Entry Migration Guide

Overview

Biggest Changes

What Has Not Changed

1. Session / Logon (35=A)

2. NewOrderSingle (35=D)

3. OrderCancelRequest (35=F)

4. OrderCancelReplaceRequest (35=G)

5. OrderStatusRequest (35=H)

6. ExecutionReport (35=8)

Fill Status Behavior

ExecType (150)

OrdStatus (39)

How to Detect Fills in FIX 5.0 SP2

7. Migration Checklist

​Overview

​Biggest Changes

​What Has Not Changed

​1. Session / Logon (35=A)

​2. NewOrderSingle (35=D)

​3. OrderCancelRequest (35=F)

​4. OrderCancelReplaceRequest (35=G)

​5. OrderStatusRequest (35=H)

​6. ExecutionReport (35=8)

​Fill Status Behavior

​ExecType (150)

​OrdStatus (39)

​How to Detect Fills in FIX 5.0 SP2

​7. Migration Checklist

Overview

Biggest Changes

What Has Not Changed

1. Session / Logon (35=A)

2. NewOrderSingle (35=D)

3. OrderCancelRequest (35=F)

4. OrderCancelReplaceRequest (35=G)

5. OrderStatusRequest (35=H)

6. ExecutionReport (35=8)

Fill Status Behavior

ExecType (150)

OrdStatus (39)

How to Detect Fills in FIX 5.0 SP2

7. Migration Checklist