Chance History

Real-time probability updates and chart history

Use this stream for live probability updates and chart backfill.

Endpoint

wss://chance-history-service.outpoll.com/ws

Authentication

No authentication required.

Message envelope

{
  "t": "<TYPE>",
  "e": "<EVENT_ID>",
  "o": ["<OUTCOME_ID>"],
  "d": { ... },
  "r": "<ERROR_MESSAGE>"
}

Field	Type	Description
t	string	Message type
e	string	Event ID
o	string[]	Outcome IDs
d	object	Message payload
r	string	Error message for failed calls

Subscribe

{
  "t": "SUBSCRIBE",
  "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
  "o": [
    "b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76",
    "97b06d16-aeff-4dd4-b08b-1ba30a2b8895"
  ]
}

After subscribe, the server sends:

1. probability with the latest known value

2. success with subscribe confirmation

Live updates

Probability update

{
  "t": "probability",
  "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
  "o": ["b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"],
  "d": {
    "t": 1712160300,
    "p": 0.67
  }
}

History update

{
  "t": "UPDATE_HISTORY",
  "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
  "o": ["b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"],
  "d": {
    "t": 1712160300,
    "p": 0.67
  }
}

Field	Type	Description
d.t	number	Unix timestamp in seconds
d.p	number	Probability from 0.0 to 1.0

Unsubscribe

{
  "t": "UNSUBSCRIBE",
  "o": [
    "b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"
  ]
}

Success response:

{
  "t": "success",
  "o": ["b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"],
  "d": { "message": "unsubscribe successful" }
}

Request history

{
  "t": "HISTORY",
  "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
  "o": [
    "b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"
  ],
  "d": {
    "p": "1H",
    "f": "2026-01-01T00:00:00Z",
    "t": "2026-01-01T12:00:00Z"
  }
}

Supported periods

Code
1s
5s
5M
10M
30M
1H
3H
4H
6H
1d
7d
1m

You can also pass a custom number of seconds as a string.

History response

{
  "t": "HISTORY_RESPONSE",
  "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
  "o": ["b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"],
  "d": {
    "b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76": [
      { "t": 1735689600, "p": 0.50 },
      { "t": 1735693200, "p": 0.52 },
      { "t": 1735696800, "p": 0.55 }
    ]
  }
}

Each point includes:

Field	Type	Description
t	number	Period end in Unix time
p	number	Close probability value

The first point is an anchor value at or before from. If no data exists in range, the service returns a flat line.

REST parity

The same history is available over REST:

GET /api/events/{eventId}/outcomes/{outcomeId}/history

Python example

chance_history.py

import asyncio, json, websockets

async def chart_stream():
    uri = "wss://chance-history-service.outpoll.com/ws"
    async with websockets.connect(uri) as ws:
        await ws.send(json.dumps({
            "t": "SUBSCRIBE",
            "e": "54ccea1a-16fd-469c-8018-84b375243e8a",
            "o": ["b21f6fd8-b9d1-4b9f-bb79-ef141e3dcb76"],
        }))

        async for msg in ws:
            data = json.loads(msg)
            print(data["t"], data["d"])