Reference

WebSocket Events

The current Socket.IO event contract implemented by Fusion's WebSocket server.

Fusion's WebSocket server is a Socket.IO server.

This page documents the events actually emitted by the backend.

Client-to-server events

Event	Payload	Notes
`subscribe:intent`	`intentId: string`	Joins the room for a specific intent. If the intent already exists, the server immediately emits `intent:status`.
`unsubscribe:intent`	`intentId: string`	Leaves a specific intent room.
`subscribe:all`	none	Joins the admin-style all-intents room and immediately receives `mempool:stats`.
`unsubscribe:all`	none	Leaves the all-intents room.
`ping`	none	Used for heartbeat; the server replies with `pong`.

Server-to-client events

`intent:status`

Primary per-intent update payload.

Current fields:

intentId
status
proofStatus
solver
fromChain
toChain
amount
createdAt
updatedAt
matchedAt
completedAt
htlcState
txHashes
error
failureReason
timestamp

The status value is already normalized for frontend use. Common values include:

proofs_pending
proofs_verified
matched
waiting_for_source_lock
executing
completed
failed

`intent:proof`

Current fields:

intentId
proofStatus
oldProofStatus
proofGeneratedAt
timestamp

`intent:new`

Broadcast to subscribe:all listeners when a new intent is added.

Payload shape matches the same formatted intent update used for intent:status.

`intent:status_changed`

Broadcast to subscribe:all listeners when the internal intent status changes.

Current fields:

the formatted intent update fields
oldStatus

Note that oldStatus comes from the backend's internal enum, not the normalized frontend status string.

`intent:proof_changed`

Broadcast to subscribe:all listeners when proof status changes.

Current fields:

intentId
proofStatus
oldProofStatus
proofGeneratedAt
timestamp

`intent:removed`

Current fields:

intentId
timestamp

`intent:not_found`

Current fields:

intentId

`mempool:stats`

Current fields:

total
submitted
matched
executing
completed
failed
cancelled

`pong`

Current fields:

timestamp

`error`

Used for invalid client payloads such as a bad intentId.

Important scope note

Some clients also listen for intent:settlement_proof.

As of today, that event is not emitted by the backend WebSocket server. If you are building a client, treat the events on this page as the implemented server contract.

Minimal subscription example

import { io } from 'socket.io-client';

const socket = io(BACKEND_URL, {
  transports: ['websocket', 'polling'],
});

socket.on('connect', () => {
  socket.emit('subscribe:intent', intentId);
});

socket.on('intent:status', (update) => {
  console.log(update.status, update.proofStatus, update.txHashes);
});

Related docs: