Providers

A provider is a read-only adapter that fetches from one source and returns the normalized Market shape. PredictionKit ships two; you can add your own.

Polymarket

import { polymarket } from '@prediction-kit/core';
polymarket({ baseUrl?, minIntervalMs?, fetchImpl? });

Backed by the public Gamma API (no auth). Notable handling:

• Parses Polymarket's stringified-JSON array fields (outcomes, outcomePrices).
• Probability comes from the Yes outcome price (already 0–1).
• Links resolve to the parent event page (/event/<event-slug>).

Kalshi

import { kalshi } from '@prediction-kit/core';
kalshi({ baseUrl?, minIntervalMs?, fetchImpl? });

Backed by the public v2 REST API (no auth). Notable handling:

• Discovers markets via the events endpoint — the bare markets listing is dominated by auto-generated parlay markets with no volume and concatenated titles.
• Uses the post-2026 fixed-point *_dollars price fields; probability is the Yes bid/ask midpoint.
• Sorts client-side (Kalshi has no server-side sort) and throttles to respect rate limits.
• Links resolve to the series page (/markets/<series-ticker>).

The unified client

const client = createClient({ providers: [polymarket(), kalshi()] });

• getMarket(id) routes by the id prefix ("kalshi:..." → Kalshi).
• getMarkets() / getTrendingMarkets() fan out in parallel and merge by descending volume. A failing provider is skipped, not fatal.

Custom providers

Implement the PredictionProvider interface and pass it to createClient — every component and hook works with it unchanged.

import type { PredictionProvider } from '@prediction-kit/core';

const myProvider: PredictionProvider = {
  source: 'polymarket', // a registered ProviderSource
  async getMarket(nativeId) {
    /* ... */
  },
  async getMarkets(opts) {
    /* ... */
  },
  async getTrendingMarkets(opts) {
    /* ... */
  },
};