AggressorIndicator (FIX tag 1057)

BooleanFIX 5.0 SP2

AggressorIndicator (tag 1057) is a Boolean field defined in FIX 5.0 SP2. It appears in 3 message types, always optionally. It is an enumerated field with 2 defined values.

At a glance

Tag: 1057
Name: AggressorIndicator
Datatype: Boolean (char)
Dialects: FIX 5.0 SP2
Messages: 3
Valid values: 2

What the specification says

Used to identify whether the order initiator is an aggressor or not in the trade.

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 1057

ExecutionReport · FIX 5.0 SP2

Tag	Field	Wire value	Meaning
8	BeginString	FIXT.1.1
9	BodyLength	130
35	MsgType	8	ExecutionReport
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
37	OrderID	ORD-10042
17	ExecID	EXEC-88117
150	ExecType	0	New
39	OrdStatus	0	New
54	Side	1	Buy
1057	AggressorIndicator	N	Order initiator is passive
151	LeavesQty	0
14	CumQty	1000000
10	CheckSum	233

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 5.0 SP2 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Valid values

A value outside this list is not a parse error — the message still decodes — but validate() reports it as validate/value-not-in-enum.

Value	Meaning	Symbolic name
Y	Order initiator is aggressor	ORDER_INITIATOR_IS_AGGRESSOR
N	Order initiator is passive	ORDER_INITIATOR_IS_PASSIVE

Where tag 1057 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	Requiredness	Where in the message
ExecutionReport	8	Optional	directly on the message body
TradeCaptureReport	AE	Optional	inside the TrdCapRptSideGrp component
TradeCaptureReportAck	AR	Optional	inside the TrdCapRptAckSideGrp component

Wire format

Y or N. Not 1/0, and not true/false. @boarteam/fix keeps the value as a string and, for enumerated fields, reports validate/value-not-in-enum when it is not a defined value.

Read tag 1057 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix50sp2";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const aggressorIndicator = message.fields[1057]?.raw;// e.g. "Y" — Order initiator is aggressor// The dictionary also carries the labels:const label = fix.dictionary  .fieldByTag(1057)  ?.enumValues?.find((e) => e.value === aggressorIndicator)  ?.description;

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix50sp2

Try the decoder Source on GitHub