kalshi-predictit-arb

Pay-per-call HTTP API that matches Kalshi markets to PredictIt contracts and returns both arbitrage directions priced after each venue's real fee drag, with worst-case net across settlement outcomes.

Base URL: https://x402.bankr.bot/0x69fb671637ed68881f66b9ebf305ec3ef5574f65/kalshi-predictit-arb
Operator: built and operated by Team Takatini · Status: live · No UI, no execution — data only.

What it computes (server-side)

Entity resolution: Kalshi markets matched to PredictIt contracts, gated on state, district, office, party, numeric strike, and cycle year. A party mismatch is a hard reject.
Both arb directions priced with real fee drag: Kalshi taker fee ceil(7 · P · (1−P))¢ per contract per leg; PredictIt 10% of winning-leg profit + 5% withdrawal drag.
Worst-case net across settlement outcomes. executable: true only at ≥ 1¢ net after all fee drag.
Depth: Kalshi order book walked to $100 / $500 / $1,000 notional. (PredictIt publishes no public depth; size within its $850/contract position limit.)
Annualized ROC to the later settlement date.

Gaps are indicative until checked against live depth, current fees, and resolution equivalence. This API makes no profit claims.

Request

GET /kalshi-predictit-arb?q=governor&limit=10&mode=opportunities

Parameter	Type	Default	Description
`q`	string	—	Keyword filter (e.g. `governor`, `senate`).
`limit`	1–25	10	Max pairs evaluated per call.
`mode`	`opportunities` \| `all`	`opportunities`	`opportunities` returns only executable pairs; `all` returns every evaluated pair.

Price & payment (x402)

$0.02 USDC per call, settled on Base via the x402 v2 exact scheme.
First request returns 402 with machine-readable payment requirements. Respond with a signed TransferWithAuthorization (EIP-3009) in the PAYMENT-SIGNATURE header (base64url-encoded JSON).
Your key never leaves your machine: sign offline, the facilitator submits (gasless for you). Refuse anything that isn't Base / exact / Base USDC / within your per-call cap.
Reference client: https://github.com/mastertyrone/kalshi-predictit-arb — offline EIP-712 signing, per-call cap, refusal checks. Key via X402_WALLET_KEY, never hardcoded.

Response schema (live sample, 2026-09-29)

{
  "q": "senate governor president house fed",
  "mode": "opportunities",
  "opportunities": [
    {
      "event": "Florida governor party winner? — Republican",
      "match_score": 0.71,
      "kalshi": { "ticker": "GOVPARTYFL-26-R", "yes_bid_c": 77, "yes_ask_c": 78 },
      "predictit": { "market": "Florida governor party winner?", "contract": "Republican", "yes_ask_c": 83, "no_ask_c": 18, "position_limit_usd": 850 },
      "best_direction": {
        "direction": "YES_KALSHI__NO_PREDICTIT",
        "kalshi_price_c": 78, "predictit_price_c": 18, "stake_c": 96,
        "raw_spread_c": 4, "net_if_yes_wins_c": 2, "net_if_no_wins_c": 7.21,
        "net_yield_c": 2, "net_yield_pct": 2.08,
        "fees": { "kalshi_taker_c": 2, "predictit_profit_fee_c": 8.2, "predictit_withdrawal_drag_c": 4.59 }
      },
      "days_to_settlement": 400, "roc_annualized_pct": 1.9, "executable": true,
      "liquidity": { "vwap_buy_c": { "100": 78, "500": 78, "1000": 78 }, "book_depth_usd": 857553.52 },
      "slippage_ok_100": true
    }
  ],
  "stats": { "pairs_evaluated": 22, "executable": 1, "kalshi_markets_scanned": 25, "predictit_contracts_scanned": 526, "duration_ms": 12616 },
  "fetched_at": "2026-09-30T03:12:02.667Z"
}

Live sample. Captured 2026-09-29 at 9:12 PM MDT ($0.02 call). Gaps move with the market — response shape and one real datapoint, not a standing opportunity.

Limits

Political markets only (Kalshi ↔ PredictIt overlap).
PredictIt depth is not public — size positions within its $850/contract limit.
Cold starts can take several seconds; allow a ~30s timeout.

Contact

Built and operated by Team Takatini. Client library: https://github.com/mastertyrone/kalshi-predictit-arb.