FIX Protocol

This page is the FIX session and message contract for the RFQ Network: which ports and dictionaries to use, how Logon authenticates, the four application messages you can send, the Kairos extension tags, and how rejections are reported. Read it if you connect over FIX; the same domain rules are described for HTTP clients in REST and streaming. Kairos exposes TLS-protected FIX endpoints for clients that require session sequencing, resend semantics, and low-latency RFQ commands.

Connectivity

Protocol	Port	Dictionary
FIX 4.4 compatibility	`9820`	`spec/kairos/FIX44.xml`
FIXT 1.1 transport	`9821`	`spec/kairos/FIXT11.xml`
FIX 5.0 SP2 application	`9821`	`spec/kairos/FIX50SP2.xml`

Both listeners terminate TLS 1.2/1.3 at the network load balancer and are source-CIDR allowlisted; the regional RFQ listeners sit behind <region>.rfq.kairos.trade, and the unified Kairos FIX edge is fix.kairos.trade. Contact Kairos onboarding for connectivity, certificates, credentials, and the versioned dictionary bundle.

Gotcha: the unified edge has two extra requirements. Clients connecting through fix.kairos.trade are provisioned as static counterparty sessions with a mandatory per-session AllowedRemoteAddresses, and every application message on that edge must additionally carry KairosProduct(9200)=RFQ. That gateway loads a strict union dictionary covering RFQ, auction, order-entry, and drop-copy messages; the RFQ bundle below is the scoped client subset.

Download the current Kairos RFQ FIX v1 dictionary bundle. Each release contains both session variants, the application dictionary, the protocol README, and SHA256SUMS. Versioned archives are immutable; the v1 URL tracks the latest backwards-compatible v1 release.

Logon

Credentials

Tag	Field	Value
49	`SenderCompID`	The API credential client ID (`ApiCredential.clientId`)
56	`TargetCompID`	`KAIROS`
553	`Username`	The API key plaintext
554	`Password`	The API secret plaintext
1137	`DefaultApplVerID`	`9` (FIX 5.0 SP2) — FIXT sessions only

Credentials are the ordinary Kairos API credential pair, created and revoked through the admin API-key procedures; Kairos stores only hashes and returns the plaintext once.

Session parameters

Setting	Value
Heartbeat interval	30 seconds
`CheckLatency`	On, with a 30-second `MaxLatency` — a skewed clock is rejected at the session layer
Session hours	24 hours a day (`StartTime` = `EndTime` = `00:00:00`)
`ResetOnLogon`	Off by default, so sequence numbers and the resend window survive a reconnect
`RefreshOnLogon`	Reloads persisted state on each Logon
Sequence / resend / gap fill	QuickFIX semantics, persisted in a file store independent of RFQ domain state

Authorization

The credential’s scopes gate every application message, and its ipWhitelist is revalidated during authentication, so a Logon from an unlisted source is refused even on an allowlisted CIDR. Revoked credentials reject new Logons immediately; existing sessions reauthenticate when their five-minute relay token expires. Aegis checks bearer JWT revocation for HTTP/WebSocket clients and is not on the FIX Logon path.

Gotcha: scopes are enforced per message, not at Logon. A session logs on successfully and then has individual commands rejected. The one exception is a credential whose scopes entitle it to no product at all, which is refused at Logon.

Logon failures

Logon reject text	When it happens	What to do
`invalid FIX credentials`	Credential or source-address failure	Verify `Username`/`Password` and that the source IP is on the credential’s allowlist
`FIX authentication is unavailable`	The credential authority could not be reached	Retry with backoff; this is not a credential problem

A failed Logon is answered with a Logon reject and a disconnect.

Application messages

Direction	MsgType	Message	Scope
Client → Kairos	`R`	QuoteRequest	`rfq:create`
Client → Kairos	`S`	Quote (create or revise)	`rfq:quote`
Client → Kairos	`AJ`	QuoteResponse (`694=1`)	`rfq:accept`
Client → Kairos	`Z`	QuoteCancel	`rfq:create` or `rfq:quote`
Kairos → Client	`AI`	QuoteStatusReport	—
Either	`j`	BusinessMessageReject	—

Session messages 0 Heartbeat, 1 TestRequest, 2 ResendRequest, 3 Reject, 4 SequenceReset, 5 Logout, and A Logon are also supported. Any other application MsgType is rejected as unsupported. Command identifiers double as idempotency keys: QuoteReqID(131) for R, QuoteID(117) for S, and QuoteRespID(693) for AJ.

QuoteRequest (`35=R`)

Creates a requester RFQ.

Tag	Field	Required	Values	Description
131	`QuoteReqID`	Y	—	Idempotency key and `client_rfq_id`
15	`Currency`	Y	—	—
38	`OrderQty`	Y	positive decimal	Package quantity
126 / 62	`ExpireTime` / `ValidUntilTime`	*	—	One of 126 or 62 is required
9002	`KairosLegsJSON`	Y	—	Non-empty JSON leg array
9001	`KairosRequestedSides`	*	`bid`, `offer`, `bid,offer`	—
54	`Side`	*	—	Fallback when 9001 is absent
9003	`KairosVenues`	N	—	CSV venue fanout
9004	`KairosPriorityVenue`	N	—	—
9007	`KairosMinimumPartial`	N	—	—

Example — a two-sided RFQ, one tag per line for readability (a real message is SOH-delimited on the wire):

8=FIX.4.4
9=<body length>
35=R                                     # MsgType — QuoteRequest
49=<your-client-id>                      # SenderCompID
56=KAIROS                                # TargetCompID
34=2                                     # MsgSeqNum
52=20260810-17:00:00.000                 # SendingTime (UTC)
131=desk-rfq-20260810-001                # QuoteReqID — idempotency key
15=USD                                   # Currency
38=100                                   # OrderQty — package quantity
126=20260810-18:00:00.000                # ExpireTime
9001=bid,offer                           # KairosRequestedSides
9002=[{"leg_id":"yes","ratio":"1","source_venue":"kalshi","market_id":"MARKET-TICKER","outcome":"yes"}]
9003=kalshi                              # KairosVenues
9004=kalshi                              # KairosPriorityVenue
9007=10                                  # KairosMinimumPartial
10=<checksum>

On fix.kairos.trade, add 9200=RFQ (KairosProduct) to this and every other application message.

Quote (`35=S`)

Creates or revises a market-maker quote.

Tag	Field	Required	Values	Description
117	`QuoteID`	Y	—	Idempotency key; on a revision it also names the quote
9000	`KairosRFQID`	*	—	One of 9000 or 131 is required
131	`QuoteReqID`	*	—	—
126 / 62	`ExpireTime` / `ValidUntilTime`	Y	—	Applies to every priced side
132 + 134	`BidPx` + `BidSize`	N	—	Must be supplied together
133 + 135	`OfferPx` + `OfferSize`	N	—	Must be supplied together
9011	`KairosMinimumQuoteQuantity`	N	—	Falls back to 110 `MinQty`, then `1`
9010	`KairosSourceVenue`	N	—	Only valid on a venue-originated RFQ
9006	`KairosQuoteRevision`	N	`1` or absent creates; `>1` revises	A revision must be exactly `current + 1`

At least one complete price/size pair is required. Example — a two-sided quote against a venue-originated RFQ:

8=FIX.4.4
9=<body length>
35=S                                     # MsgType — Quote
49=<your-client-id>
56=KAIROS
34=7
52=20260810-17:01:12.000
117=mm-quote-0001                        # QuoteID — idempotency key
9000=rfq_01H…                            # KairosRFQID
126=20260810-17:06:00.000                # ExpireTime — applies to both sides
132=0.47                                 # BidPx
134=50                                   # BidSize
133=0.52                                 # OfferPx
135=50                                   # OfferSize
9010=kalshi                              # KairosSourceVenue
9011=5                                   # KairosMinimumQuoteQuantity
10=<checksum>

To revise it, resend 35=S with the same QuoteID(117) and 9006=<current + 1>.

QuoteResponse (`35=AJ`)

Accepts (hits or lifts) a quote.

Tag	Field	Required	Values	Description
693	`QuoteRespID`	Y	—	Idempotency key
694	`QuoteRespType`	Y	`1` only	Hit/lift. No other value is supported
117	`QuoteID`	Y	—	—
54	`Side`	Y	`1` = take the offer, `2` = take the bid	—
38	`OrderQty`	Y	—	—
44	`Price`	Y	—	Must equal the quoted level price
9005	`KairosMappingSnapshotID`	Y	—	—
9006	`KairosQuoteRevision`	Y	positive integer	—

Acceptance binds the quote revision, side, quantity, expected price, and mapping snapshot. Example — lifting the offer for 25:

8=FIX.4.4
9=<body length>
35=AJ                                    # MsgType — QuoteResponse
49=<your-client-id>
56=KAIROS
34=11
52=20260810-17:02:03.000
693=accept-0001                          # QuoteRespID — idempotency key
694=1                                    # QuoteRespType — hit/lift
117=mm-quote-0001                        # QuoteID
54=1                                     # Side — 1 selects the offer
38=25                                    # OrderQty
44=0.52                                  # Price — must equal the quoted level
9005=snap_01H…                           # KairosMappingSnapshotID
9006=1                                   # KairosQuoteRevision
10=<checksum>

QuoteCancel (`35=Z`)

Withdraws a quote or cancels an RFQ, depending on which identifier you send.

Tag sent	Effect	Scope
`QuoteID(117)`	Withdraws that quote	`rfq:quote`
`KairosRFQID(9000)`	Cancels that RFQ	`rfq:create`
`QuoteReqID(131)`	Cancels that RFQ (fallback when 9000 is absent)	`rfq:create`

One of the three is required.

Gotcha: QuoteCancel derives its idempotency key from the resource ID, not from a client-supplied identifier — unlike every other command on this session.

QuoteStatusReport (`35=AI`)

Sent for every accepted command.

Tag	Field	Description
131	`QuoteReqID`	—
117	`QuoteID`	—
9000	`KairosRFQID`	—
9005	`KairosMappingSnapshotID`	—
9008	`KairosAcceptanceID`	—
9009	`KairosState`	The RFQ, quote, or acceptance state, from the same vocabulary the REST API uses — see Lifecycle states
9006	`KairosQuoteRevision`	—

Empty values are omitted rather than sent blank.

Kairos extension tags

Tags 9000–9011 are the version 1.0 Kairos extension range.

Tag	Name	Type	Meaning
9000	`KairosRFQID`	STRING	Stable RFQ ID
9001	`KairosRequestedSides`	STRING	`bid`, `offer`, or `bid,offer`
9002	`KairosLegsJSON`	STRING	Normalized non-empty leg array
9003	`KairosVenues`	STRING	CSV venue targets
9004	`KairosPriorityVenue`	STRING	Preferred home-region venue
9005	`KairosMappingSnapshotID`	STRING	Immutable mapping snapshot
9006	`KairosQuoteRevision`	INT	Positive quote revision
9007	`KairosMinimumPartial`	QTY	Minimum RFQ partial quantity
9008	`KairosAcceptanceID`	STRING	Acceptance/execution ID
9009	`KairosState`	STRING	Current lifecycle state
9010	`KairosSourceVenue`	STRING	Originating venue
9011	`KairosMinimumQuoteQuantity`	QTY	Minimum executable quote quantity

Data formats

Kind	Format
Decimals	FIX decimal strings
Timestamps	UTC, `YYYYMMDD-HH:MM:SS[.sss]`. RFC 3339 is also accepted on inbound expiries
IDs	Case-sensitive opaque strings

The server loads these dictionaries with unknown messages, unknown fields, out-of-order fields, and invalid messages rejected. Rules that XML cannot express — such as requiring either an RFQ ID or request ID, or at least one complete bid/offer pair — are enforced by the same deterministic application validator used by REST.

Rejections

Session-layer: `Reject(35=3)`

Standard SessionRejectReason(373) values:

`373`	When it happens	What to do
`0`	Invalid tag number	Remove the tag; it is not in the loaded dictionary
`1`	Required tag missing	Add the tag named in the message’s field tables above
`2`	Tag not defined for this message type	Move the value to the message that defines it
`4`	Tag specified without a value	Send a value or omit the tag
`5`	Value is incorrect	Check the Values column for that tag
`6`	Incorrect data format for value	Check Data formats
`11`	Invalid MsgType	Send only `R`, `S`, `AJ`, `Z`, or a session message
`13`	Tag appears more than once	De-duplicate the tag
`14`	Tag specified out of required order	Emit fields in dictionary order

Application-layer: `BusinessMessageReject(35=j)`

BusinessRejectRefID(379) echoes QuoteReqID(131) or, failing that, QuoteID(117).

`BusinessRejectReason(380)`	When it happens	What to do
`0` (Other)	An application message arrived on a session that has not authenticated	Complete Logon before sending commands
`3` (Unsupported Message Type)	Application `MsgType` outside `R`, `S`, `AJ`, `Z`	Send a supported message
`5` (Conditionally Required Field Missing)	Every business failure: missing or malformed tag, unsupported `Side(54)` or `QuoteRespType(694)`, missing scope, and any domain rejection — stale revision, expired quote, insufficient remaining quantity, unknown resource, or conflicting state	Read `Text(58)`; `380` alone does not distinguish these

Gotcha: 380=5 is not a reliable discriminator. Nearly every business failure arrives under it, so branch on Text(58) rather than on the reason code.

On the unified edge (`fix.kairos.trade`)

RFQ commands are relayed to the RFQ service, and a rejection returns 380=0 with a stable machine-readable code in Text(58):

`Text(58)` code	When it happens	What to do
`RFQ_COMMAND_INVALID`	Envelope or field validation failed	Fix the message against the field tables above
`RFQ_COMMAND_REJECTED`	Domain validation failed	Re-read the resource state
`RFQ_RESOURCE_NOT_FOUND`	Unknown RFQ, quote, or acceptance	Confirm the id and that it is yours
`RFQ_RESOURCE_CONFLICT`	Terminal or otherwise conflicting state	Re-read the resource; do not retry blindly
`RFQ_COMMAND_FAILED`	Anything else, including stale revision, expired quote, and insufficient size	Re-read the quote and resubmit against the current revision
`RFQ_RELAY_NOT_ENABLED`	Inbound RFQ command execution is not enabled on that deployment	Contact onboarding; retrying will not help

An idempotent replay is acknowledged with QuoteStatusReport(AI) carrying KairosState(9009) of duplicate.

Machine-readable contract

The complete message-by-message field contract and business rules are included in spec/kairos/README.md beside the dictionary files.

Overview

Market Data API

Data API

Execution API

Agora Auction API

REST Guides

Market Data Guides

RPC Guides

RFQ Guides

WebSocket Guides

Krisis Guides

Connectivity

Logon

Credentials

Session parameters

Authorization

Logon failures

Application messages

QuoteRequest (`35=R`)

Quote (`35=S`)

QuoteResponse (`35=AJ`)

QuoteCancel (`35=Z`)

QuoteStatusReport (`35=AI`)

Kairos extension tags

Data formats

Rejections

Session-layer: `Reject(35=3)`

Application-layer: `BusinessMessageReject(35=j)`

On the unified edge (`fix.kairos.trade`)

Machine-readable contract

​Connectivity

​Logon

​Credentials

​Session parameters

​Authorization

​Logon failures

​Application messages

​QuoteRequest (35=R)

​Quote (35=S)

​QuoteResponse (35=AJ)

​QuoteCancel (35=Z)

​QuoteStatusReport (35=AI)

​Kairos extension tags

​Data formats

​Rejections

​Session-layer: Reject(35=3)

​Application-layer: BusinessMessageReject(35=j)

​On the unified edge (fix.kairos.trade)

​Machine-readable contract

Connectivity

Logon

Credentials

Session parameters

Authorization

Logon failures

Application messages

QuoteRequest (`35=R`)

Quote (`35=S`)

QuoteResponse (`35=AJ`)

QuoteCancel (`35=Z`)

QuoteStatusReport (`35=AI`)

Kairos extension tags

Data formats

Rejections

Session-layer: `Reject(35=3)`

Application-layer: `BusinessMessageReject(35=j)`

On the unified edge (`fix.kairos.trade`)

Machine-readable contract