River Markets: Smart Order Routing & Liquidity for Polymarket, Kalshi

River Markets Overview

River Markets Key features

• Liquidity aggregation

  River merges order books from Kalshi, Polymarket, and Polymarket US into one view for contracts that resolve on the same outcome. Traders see full depth across venues without watching separate interfaces.

• Smart order routing

  The routing engine splits orders and sends them to the venue with the best available price and size. River reports average savings of about two cents per contract compared with single venue execution.

• Advanced order types

  Icebergs, pegs, take profit, and stop loss orders run server side, so larger traders can hide size and control market impact. Canceling a parent order unwinds the entire structure.

• Unified order management

  A multi book blotter handles hundreds of orders across venues from one screen. Traders place, amend, and cancel orders while they track consolidated fills, positions, and real time P&L.

• Strategy subaccounts

  Desks can isolate strategies, teams, or capital pools in separate subaccounts. P&L attribution stays separate, so each book gets measured on its own.

• Standardized contract IDs

  One river_id schema replaces venue specific tickers across the terminal and the API. Teams write integration code once instead of rebuilding it for every exchange.

• Institutional API

  REST and WebSocket endpoints use Ed25519 signed authentication, and private keys never leave the client. An official Python SDK, historical order book data, and programmatic access to advanced order types support systematic strategies.

• Non custodial design

  River never takes custody of funds. Positions and balances stay in the trader's own accounts at each exchange.

River Markets Fees

• No public schedule River Markets does not publish a fee schedule and sets pricing on a custom basis for institutional and professional clients.
• Venue fees apply Users still pay the trading fees charged by the underlying venues such as Kalshi or Polymarket.
• Platform charges Any platform level charges for connectivity, routing, or advanced execution features are discussed during onboarding.

How to use River Markets

1. 1

   Request access

   Request access on the River Markets website or book a demo with the team. The product targets professional and institutional traders, so expect an onboarding conversation rather than a self-serve signup.

2. 2

   Connect your exchange accounts

   Link your existing accounts at Kalshi, Polymarket, or Polymarket US. River routes orders without taking custody, so your funds and positions stay under your control at each venue.

3. 3

   Search for markets

   Search markets in the terminal or through the API. Contracts appear under river_ids that map the same event across venues, so you see one market instead of separate tickers per exchange.

4. 4

   Choose order type and size

   Set your size and pick a market or limit order, or submit advanced types like icebergs and pegs that run server side. Canceling a parent order unwinds the whole structure.

5. 5

   Enable smart routing

   Turn on smart routing when several venues list equivalent contracts. The system splits your order and sends each piece to the book with the best available price, which the company reports saves around two cents per contract on average.

6. 6

   Track fills and P&L

   Watch fills, positions, and real time P&L in the multi book blotter, or stream them over WebSocket. The blotter handles hundreds of orders across all connected venues in one view.

7. 7

   Create subaccounts

   Open subaccounts to isolate individual strategies, desks, or capital pools. P&L stays attributed to each subaccount so you can measure performance without mixing unrelated books.

8. 8

   Automate with the Python SDK

   Install the official Python SDK for systematic strategies. It supports synchronous and asynchronous clients, Ed25519 signed authentication, historical book and trade data, and the same advanced order types you get in the terminal.

River Markets Demo video

River Markets Screenshots

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River Markets Updates

1. 

   River Markets Aug 11, 2026 · 17:45
   Today, River Markets announced an $8.5M seed round led by @HaunVentures
   We’re building the prime broker for prediction markets, giving professional trading firms unified execution and risk across venues.
   Thanks to @FortuneMagazine and @c_grigera for covering what we're building
   https://fortune.com/2026/08/11/exclusive-river-markets-seed-round-prediction-market-trading-tools-institutions
   • 6 replies
   • 1 reposts
   • 21 likes
   • 2.3K views
2. 

   River Markets Aug 11, 2026 · 16:29
   Institutions trading on event contracts need deep liquidity and powerful tools that ensure they execute trades efficiently.
   We’re excited to lead the seed round of @river_markets as they build the prime brokerage layer for prediction markets.
   More here: https://www.haun.co/writing/the-execution-layer-for-prediction-markets
   • 1 replies
   • 2 reposts
   • 19 likes
   • 1.4K views
3. 

   River Markets Aug 11, 2026 · 14:43
   While prediction markets continue to gain rapid adoption, its pro trading infrastructure has lagged behind... until today!
   Excited to back @oscar_lvy @antonin_parrot and the @river_markets team as they build the prime brokerage for prediction markets. Congrats, team!
   • 3 replies
   • 2 reposts
   • 23 likes
   • 1.9K views
4. 

   River Markets Aug 11, 2026 · 14:08
   Today, River Markets announced an $8.5M seed round led by @HaunVentures .
   We’re building the prime broker for prediction markets, giving professional trading firms unified execution and risk across venues.
   Blog post : https://www.rivermarkets.com/blog/announcing-our-8-5m-seed-round.html

   

   2 more in this thread

   We launched on May 1st with trading teams that included several of the top 10 traders by volume on Kalshi and Polymarket.
   Today, leading hedge funds and proprietary trading firms use River Markets to trade prediction markets at scale.

   The round includes @ycombinator , @cbventures , @ufo_holdings , Qube Research and Technology (QRT), TENET, Humbition, Kima Ventures, Cherry Ventures, Stack Asset Management and Perpetual Strategies, alongside Mark Kornfilt, Jacob Fortinsky (Novig) and an exceptional group of angel investors.
   Trading prediction markets professionally?
   See how River Markets saves firms 2% on each trade:
   https://calendar.app.google/RRBxj2cHBHUKQukj9
   • 26 replies
   • 15 reposts
   • 152 likes
   • 30.5K views
5. 

   River Markets Aug 11, 2026 · 14:01
   Prediction markets are becoming a global asset class, but their trading infrastructure has not kept pace.
   Firms still manage separate accounts, balances, APIs, and risk systems across fragmented venues.
   River Markets brings that into one institutional platform.
   • 40 views
6. 

   River Markets Aug 2, 2026 · 14:58
   🆕 New project added to the prediction markets wiki
   River Markets
   @river_markets is building the institutional trading infrastructure for prediction markets, aggregating all venues into a single stack 📈🏦
   Built for funds, quants and professional trading desks.

   
   • 3 replies
   • 2 reposts
   • 11 likes
   • 685 views
7. 

   River Markets Jul 15, 2026 · 20:55
   On the latest episode of Prediction Market Movers, @GerlacherC sits down with @river_markets CEO @oscar_lvy to talk through how his company is building prime brokerage infrastructure for prediction markets. https://youtu.be/O2mEk_gA1CM?si=n3-gYi0AImA6H9my
   • 4 reposts
   • 12 likes
   • 3.5K views
8. 

   River Markets Jun 16, 2026 · 17:45
   River Markets: Prime brokerage for prediction markets, the fastest-growing asset class in finance. Aggregates every major event-contract venue into one account: best execution, portfolio + order management, a unified API.
   http://rivermarkets.com
   @river_markets
   • 1 replies
   • 1 reposts
   • 5 likes
   • 693 views
9. 

   River Markets Jun 4, 2026 · 18:39
   Up and to the right
   • 3 replies
   • 7 likes
   • 1.6K views
10. 

    River Markets May 26, 2026 · 14:25
    Excited to announce the most advanced trading platform for prediction markets. This is only the beginning.
    • 4 replies
    • 12 likes
    • 3.3K views
11. 

    River Markets May 19, 2026 · 01:06
    Join us Wednesday in San Francisco
    • 2 replies
    • 8 likes
    • 1.6K views

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