CHAT - rooms, members and what they say

Generated from chat-wire.json - do not edit this file. Run python generate.py after changing the registry.

The one protocol in this folder that Norsk Data never shipped. It is written down for the same reason as the others: so the next change is made against a statement rather than a re-reading of the source. Federation (task 58) adds message kinds to it, and constraint 5 of that design says both ends move in the SAME commit - this file is where a new kind is declared before it is built.

Where it sits: A chat message is the BODY of a SINTRAN datagram (see sintran-wire.json). Nothing about the body is COSMOS; everything carrying it is.

Status	Means
MEASURED	Observed on the wire or carved from the kernel, with the evidence named.
inferred	Follows from something measured, or read from the ND manuals, but not itself observed here.
UNKNOWN	We copy it, mirror it, or leave it alone. NOT safe to compute or vary.
~~superseded~~	A reading that was believed and is now disproved. Kept so it is not re-derived.

message_prefix

Word	Byte	Field	What it is	Status	Evidence
	0	kind	which message this is - see message_kinds	MEASURED	ChatMessageGoldenBytesTests pins the encoding both directions
	1	nickname_length	how many ASCII bytes of nickname follow. Zero is legal and means the message carries no name.	MEASURED	ChatMessageGoldenBytesTests; a /who request carries kind 11 with an empty name field

Flows

Generated from the registry, so a ladder cannot name an operation that does not exist.

A client joins a room and says something

The whole client path. Only the first step goes through XROUT; everything after it is port to port.

Proved: two users at once on D100, 2026-08-18

sequenceDiagram
    autonumber
    participant client
    participant XROUT
    participant server
    client->>XROUT: Join
    Note over client,XROUT: the room is known by NAME, not address - this is the only chat message that is
    XROUT->>server: Join
    Note over XROUT,server: forwarding SPENDS one of the server's free connections
    server->>client: Welcome
    Note over server,client: sent to the address read OFF the arrived letter - the server is never told it separately
    client->>server: Say
    Note over client,server: direct, port to port; XROUT is out of the picture
    server->>client: Said
    Note over server,client: fanned out to every member of the room
    client->>server: Leave
    Note over client,server: or just terminate - SINTRAN clears the port either way

A member changes nickname

A request, not a statement: the server can refuse it for the same reason it refuses a join.

Proved: /nick on D100, 2026-08-19 - BJORN became OLAV and the name survived a restart via CHAT:CNFG

sequenceDiagram
    autonumber
    participant member
    participant server
    participant room
    member->>server: Rename
    Note over member,server: carries the wanted name
    server->>room: Renamed
    Note over server,room: carries BOTH names, so a client holding a transcript can connect the old to the new

Still open

#	Question	Status	What would settle it
C1	Does a trunk carry ONE room or ALL rooms?	UNKNOWN	phase B - bring one trunk up and see whether a per-room trunk buys anything a room field does not
C2	How does a system-qualified name travel?	UNKNOWN	phase C, and it changes message_prefix - the golden-byte tests must move in the same commit
C3	Where do origin system and hop count live?	UNKNOWN	phase D - three machines, one pair reachable only through the third, and a message that must arrive exactly once
C4	What frees a remote member's seat when the machine holding half a room goes away?	UNKNOWN	stop a peer server mid-conversation and watch what the other side does