> ## Documentation Index
> Fetch the complete documentation index at: https://docs.0xarchive.io/llms.txt
> Use this file to discover all available pages before exploring further.

# HIP-4 Data Provider: Historical Outcome-Market Data API

> HIP-4 data provider for Hyperliquid outcome markets: order books, trades, OI, and outcome settlement status from May 2026, priced in the [0, 1] range.

HIP-4 outcome markets use side identifiers and probability-priced fields. `mark_price` and `mid_price` represent implied probability in `[0, 1]`, not USD.

HIP-4 outcome-market history starts May 2026 and covers more than 500 outcome series across order books, trades, open interest, and per-outcome settlement status, continuous to the current hour.

```bash theme={"theme":"github-dark"}
curl "https://api.0xarchive.io/v1/hyperliquid/hip4/orderbook/%230" \
  -H "X-API-Key: $OXARCHIVE_API_KEY"
```

<CardGroup cols={2}>
  <Card title="HIP-4 REST" icon="binary" href="/rest-api/hip4">
    Outcome-market route family.
  </Card>

  <Card title="Response schemas" icon="braces" href="/schemas">
    Shared field rules and envelope behavior.
  </Card>
</CardGroup>

## Why 0xArchive Fits

HIP-4 data is easy to misuse if it is treated like a normal perp or Spot market. 0xArchive separates HIP-4 into `/v1/hyperliquid/hip4/*`, documents the probability-price caveat, and keeps outcome-market routes visible in the REST taxonomy.

Use HIP-4 routes for outcome discovery, outcome lookup by slug, question lookup, side-level order books, trades, candles, open interest, and historical probability analysis where Endpoint Reference exposes the relevant endpoint. Store the outcome identifier, question identifier or slug, venue family, timestamp, and request ID with every output.

## Implementation Pattern

Start by discovering or confirming the question, outcome slug, or outcome side, then pull a small order-book, trade, or candle request. If the output feeds a model, alert, or backtest, check data-quality routes and label price fields as probabilities. If a coding agent generates code, instruct it to preserve `#` identifiers and URL encoding.

## Next Step

Open [HIP-4 REST](/rest-api/hip4), then pair it with [Schemas](/schemas) and [Reliability and gaps](/guides/reliability-and-gaps).

## Buyer Fit

Use this route family when the application needs outcome-market state rather than a normal perp or Spot market. The strongest use cases are probability-history analysis, outcome liquidity monitoring, outcome-market dashboards, and route-safe agent workflows that need the probability-price rule spelled out before code is generated.

## Data Safety

Keep HIP-4 output separate from dollar-priced series in storage and analytics. A downstream chart or strategy should know it is reading outcome probability-like data. Add data-quality checks before a model or alert acts on the result.

Agent answers should repeat the probability caveat when HIP-4 prices appear in generated code.