Player-prop matching and settlement rules

Two markets can ask the same player to exceed the same line and still pay differently when that player does not play. PredictorSDK separates prop identity from settlement equivalence. These options apply to player props only. Moneylines, spreads, and game totals publish a smaller matrix of their own (tie, overtime, push), with its rows only when you send include_rules=true; a player prop's matrix is always there. See game-line rules.

Choose a policy

Use the existing sports matching endpoint.

Both policies work with list pagination, lookups (event_id and source_id on GET /v1/matching-markets/sports/lookup), and include_settled=true. A cursor belongs to one policy and cannot be reused after switching policies. Lookup still accepts at most 100 unique identifiers and remains unpaginated. Without include_submarkets=true, each event carries only its full-game moneyline, never player-prop outcomes.

GET /v1/matching-markets/sports?include_submarkets=true&player_prop_match=same_prop

For a known event, call GET /v1/matching-markets/sports/lookup?event_id=<canonical-event-id>; do not search every page to rediscover it. A result requires at least two distinct providers, not two markets from the same venue. An event whose only matches are player props is listed only when the policy admits its props: with include_submarkets=true&player_prop_match=same_prop today, because the strict policy currently admits none.

What must match in both modes

The sport and league, both teams, game date, player, statistic, full-game period, threshold, and native selection meanings must agree. NFL kickoff dates are normalized to America/New_York; Polymarket's UTC-dated slug is not used as the Eastern game date. Player names are resolved against both teams' ESPN rosters to an unambiguous athlete ID, and exactly one ESPN fixture must corroborate the matchup and Eastern game day. An explicit source kickoff that conflicts with ESPN is refused. Explicit full/display-name aliases and individually reviewed, athlete-bound spellings may match; initials, surname-only guesses, suffix removal, and arbitrary collision resolution do not.

For integer statistics, 250+ means Over 249.5, not Over 250. A contract requiring more than 10 points is not the same as 10+ points. Only verified nonnegative half-point thresholds are admitted in this release; whole-number push contracts, exact-value/range bets, fractional statistics, weekly accumulation, season props, and D/ST units are not player-prop matches. Passing touchdowns and touchdowns scored are separate statistics.

Roster checks are performed during sports ingestion, with a five-minute cache and bounded requests. A missing or stale roster, a team conflict, or an ambiguous athlete removes that prop, not ordinary game lines. Current rosters cannot certify historical membership: ingestion does not newly admit props more than 48 hours past their scheduled start. Previously verified archived props remain eligible under include_settled=true; older snapshots without identity verification do not acquire it retroactively.

Read the rule matrix

Every returned player prop has settlement_equivalence and rule_comparisons.

Each rule_comparisons row has a machine-readable rule, readable label, comparison, and source_values. Each source value names its exact provider and market_id, a machine-readable value, a plain-language description, and an evidence_url when verified. The matrix always covers:

Filter rows with comparison=different to find known differences. Filter unverified rows to find evidence gaps. Values are extensible strings; display the description rather than guessing an unfamiliar value's meaning. A row can have a known difference and still contain an unknown source value. Agreement on observed clauses is not a complete contract review, and unknown values never mean equivalent or unrestricted.

Rule evidence is attached to individual source contracts, not assumed from the provider's name. Market clauses are observed at ingestion. Kalshi product terms require the current series to link to the reviewed document; ProphetX requires its filings index to retain the reviewed NFL filing. Both require the document's SHA-256 to match the reviewed version; these checks are cached for at most five minutes. Changed or unavailable documents leave affected dimensions unknown. Known unresolved wording is not assigned an invented precedence. Read the evidence link for additional applicable terms.

Example: a no-play difference

The September 2026 audit found Josh Allen passing-yard props with matching game/player/249.5 identities, but different non-participation treatment:

A fair-price settlement, a 50-50 split, and a purchase-price refund are not interchangeable. A same-prop match is useful for discovery and comparison; it does not establish a risk-free arbitrage or a perfect hedge.

For a comparison UI, show the prop's display_name, an overall settlement_equivalence badge, and the descriptions from each rule row. Keep unknown rows visible. A simplified excerpt (the actual response contains all nine rows and exact source market references) looks like:

{
  "display_name": "Josh Allen Passing yards O/U 249.5",
  "settlement_equivalence": "different",
  "rule_comparisons": [
    {
      "rule": "non_participation",
      "label": "Player does not participate",
      "comparison": "different",
      "source_values": [
        {
          "provider": "kalshi",
          "market_id": "KXNFLPASSYDS-26SEP13BUFHOU-BUFJALLEN17-250",
          "value": "active_no_snap_pregame_fair_price",
          "description": "If active but never takes a snap, settles at the pregame fair price. Inactive-player handling has not been verified here.",
          "evidence_url": "https://api.elections.kalshi.com/trade-api/v2/markets/KXNFLPASSYDS-26SEP13BUFHOU-BUFJALLEN17-250"
        },
        {
          "provider": "polymarket",
          "market_id": "4080510",
          "value": "under_wins",
          "description": "If the player does not participate or is inactive, Under/No wins and Over/Yes loses.",
          "evidence_url": "https://gamma-api.polymarket.com/markets/4080510"
        }
      ]
    }
  ]
}

Coverage and limitations

These are supported families, not a promise of a matching line at every venue. ProphetX alternate strikes are not exposed under the primary market ID: its market-detail response selects one current primary strike. Both selection labels and structured strike values must agree, including every order-book level's outcome identity. A whole-number primary line is excluded even when an alternate half-point line exists.

The September 14 audit read all seven upstreams. Predict's 20 NFL statistical props were weekly passing-yard or anytime-touchdown contracts, not single-game contracts. SX Bet's 386 NFL markets, AlphaArcade's current NFL game children, and Hyperliquid's NFL outcomes provided no verified player-stat pairing. Provider tags alone are insufficient: AlphaArcade even carried an NFL tag on a SpaceX IPO question. Missing coverage stays explicit rather than creating a player match from unrelated or ambiguous data.

The Chiefs' published roster names Kenneth Walker, while ESPN calls athlete 4567048 Kenneth Walker III. This reviewed alias is tied to that exact athlete and still requires a fresh matching-team roster. It does not remove suffixes from other players or resolve a name collision automatically.

Availability is dynamic. NBA points inventory was empty on Kalshi during this audit; basketball evidence includes historical Polymarket contracts and the current published Kalshi terms, not a certified live NBA pair. This release does not claim a complete settlement profile for any audited provider pair; strict mode can legitimately return no player props. Previous NBA/WNBA name-and-line groupings are not grandfathered into strict equivalence.

Canonical player keys use espn_<league>_<athlete-id>. Same-prop keys identify the base prop; strict keys additionally identify a reviewed settlement group. One base prop can contain several equivalent subsets: strict mode emits each qualifying subset separately and never pulls in an incompatible third venue. Join native market/outcome IDs to market detail for current data; this endpoint adds no prices, liquidity, or execution advice.

ProphetX market detail converts its Trading API's American-odds offers into probabilities: the cheapest available back offer is the named selection's ask, and the opposite selection's ask supplies the complementary bid. price is the midpoint when both are present, not a last trade or a guaranteed fill. A one-sided book remains one-sided, and an empty book has null quotes. These quote conventions do not establish settlement equivalence or make an alternate strike interchangeable with the current primary strike.