Streaming Quotes

Overview

The streaming-quotes endpoint emits Server-Sent Events as each protocol returns a quote, instead of waiting for all protocols to complete. Use this for snappy UI — display the first quote in ~200ms instead of waiting 5+ seconds for the slowest aggregator. For a hands-on walkthrough see the Streaming Quotes guide.

Endpoint

GET /leokit/streaming-quotes

Request

Authentication

EventSource cannot set custom headers reliably, so authentication accepts both styles:

Method	Example
`Api-Key` header	`Api-Key: YOUR_API_KEY` (preferred when possible)
`api_key` query parameter	`?api_key=YOUR_API_KEY`

Query Parameters

Parameter	Type	Required	Description
`from_asset`	string	Yes	Source asset in `CHAIN.SYMBOL-ADDRESS` format
`to_asset`	string	Yes	Destination asset in `CHAIN.SYMBOL-ADDRESS` format
`amount`	string	Yes	Amount in source-asset base units (wei, sats, etc.)
`origin`	string	No	Source wallet address (improves quote accuracy)
`destination`	string	No	Destination wallet address
`streaming_interval`	number	No	THORChain/MAYAChain streaming interval (default `1`)
`streaming_quantity`	number	No	THORChain/MAYAChain streaming sub-swap count
`api_key`	string	No	Alternative to `Api-Key` header (see above)

Response

Headers

Content-Type: text/event-stream
Cache-Control: no-cache
Connection: keep-alive

Event Sequence

Events are sent as data: <json>\n\n chunks (legacy SSE format — no named event: fields).

Order	Event payload `type`	Description
1	`init`	Stream opened, includes `quote_id` and total protocols being queried
2..N	`quote`	One per protocol that returns a valid quote
N+1	`final`	Aggregated, sorted, deduplicated payload (after all settle)
N+2	`finished`	Stream closing

If no protocols return a usable quote, an error event is sent in place of final.

Event Payloads

init
quote
final
error
finished

{
  "type": "init",
  "quote_id": "01953c9a-...",
  "timestamp": "2026-04-28T12:00:00.000Z",
  "total": 7
}

{
  "type": "quote",
  "protocol": "chainflip",
  "data": {
    "expected_amount_out": "0.0498",
    "fees": [...],
    "out_asset_decimal": 18,
    "in_asset_decimal": 8
  }
}

{
  "type": "final",
  "quote_id": "01953c9a-...",
  "timestamp": "2026-04-28T12:00:00.000Z",
  "quotes": [
    {
      "protocol": "chainflip",
      "data": { "...": "..." },
      "expectedAmountOutNum": 0.0498,
      "totalFeesUsd": 1.23,
      "totalSwapSeconds": 120,
      "flags": ["FASTEST"]
    }
  ]
}

{
  "type": "error",
  "code": "UNABLE_TO_RETRIEVE_QUOTES",
  "message": "...",
  "details": [
    { "protocol": "thorchain", "message": "Pool unavailable" }
  ]
}

{ "type": "finished" }

Quote Object Fields (in `final` event)

Field	Description
`expectedAmountOutNum`	Numeric expected output (for sorting)
`totalFeesUsd`	Total combined fees in USD
`totalSwapSeconds`	Estimated time-to-settle
`flags`	Tags like `FASTEST`, `CHEAPEST`, `BEST_OUTPUT`

Timeouts

Total budget: 8 seconds. Protocols that haven’t responded by then are dropped.
Per-protocol circuit breaker: 5 seconds. Protocols that fail repeatedly are skipped.

Examples

Browser (EventSource)

const url = new URL("https://api.leokit.dev/leokit/streaming-quotes");
url.searchParams.set("from_asset", "ETH.ETH");
url.searchParams.set("to_asset", "BTC.BTC");
url.searchParams.set("amount", "1000000000000000000");
url.searchParams.set("api_key", "YOUR_API_KEY");

const es = new EventSource(url.toString());

es.onmessage = (e) => {
  const event = JSON.parse(e.data);
  switch (event.type) {
    case "init":     console.log("started", event.quote_id); break;
    case "quote":    console.log("got", event.protocol);     break;
    case "final":    console.log("done", event.quotes.length); break;
    case "finished": es.close(); break;
    case "error":    console.error(event); es.close(); break;
  }
};

Server (fetch)

const res = await fetch(
  "https://api.leokit.dev/leokit/streaming-quotes?from_asset=ETH.ETH&to_asset=BTC.BTC&amount=1000000000000000000",
  { headers: { "Api-Key": "YOUR_API_KEY" } }
);

const reader = res.body.getReader();
const decoder = new TextDecoder();

while (true) {
  const { value, done } = await reader.read();
  if (done) break;
  const chunk = decoder.decode(value);
  for (const line of chunk.split("\n\n")) {
    if (!line.startsWith("data: ")) continue;
    const event = JSON.parse(line.slice(6));
    // handle event
  }
}

Errors

Status	Code	Description
`400`	`BAD_REQUEST`	Missing or malformed `from_asset`, `to_asset`, or `amount`
`400`	`INVALID_ASSET_FORMAT`	Asset string not in `CHAIN.SYMBOL-ADDRESS` format
`401`	`INVALID_API_KEY`	Missing or invalid API key

The UNABLE_TO_RETRIEVE_QUOTES error is delivered inside the SSE stream as a type: "error" event, not as an HTTP error. See the error codes catalog for the full list.

Authorizations

Api-Key

string

header

required

Demo API-Key (Sandbox): 7037d2b3-9c76-4f62-b730-c544f7570fa4

Query Parameters

from_asset

string

required

Input asset identifier.

to_asset

string

required

Output asset identifier.

origin

string

required

From wallet address.

destination

string

required

To wallet address.

amount

string

required

Amount to swap.

api_key

string

Alternative to Api-Key header (useful for EventSource which cannot set headers).

Response

Server-Sent Events stream. Events are sent as data: {json}\n\n format.

SSE stream with events: init, quote (per protocol), final (sorted), finished.

Core Endpoints

Endpoint Details

Explorer API

Overview

Endpoint

Request

Authentication

Query Parameters

Response

Headers

Event Sequence

Event Payloads

Quote Object Fields (in `final` event)

Timeouts

Examples

Browser (EventSource)

Server (fetch)

Errors

Authorizations

Query Parameters

Response

Core Endpoints

Endpoint Details

Explorer API

Documentation Index

​Overview

​Endpoint

​Request

​Authentication

​Query Parameters

​Response

​Headers

​Event Sequence

​Event Payloads

​Quote Object Fields (in final event)

​Timeouts

​Examples

​Browser (EventSource)

​Server (fetch)

​Errors

Authorizations

Query Parameters

Response

Overview

Endpoint

Request

Authentication

Query Parameters

Response

Headers

Event Sequence

Event Payloads

Quote Object Fields (in `final` event)

Timeouts

Examples

Browser (EventSource)

Server (fetch)

Errors