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 Sep 30, 2026 · 17:19
   River Markets 🤝 RFQs
   • 3 replies
   • 1 reposts
   • 33 likes
   • 5.3K views
2. 

   River Markets Sep 23, 2026 · 18:35
   In the wake of @kalshi and @polymarket taking sports volume, @draftkings, @underdog, and @fanduel have recently started to operate their own native prediction market products (DCM or FCM).
   “Sportsbooks vs prediction markets” is the wrong question.
   The two categories are converging.
   • 7 replies
   • 1 reposts
   • 17 likes
   • 1.8K views
3. 

   River Markets Sep 22, 2026 · 18:55
   A 2c improvement on 50,000 contracts is $1,000. Now multiply that by every game in the season.
   For any serious trading firm, checking every exchange for the best price & fills not optional.
   River Markets handles this all for you, giving you an average price improvement of 2c, letting you focus on your models and trading.
   • 4 replies
   • 2 reposts
   • 15 likes
   • 2.2K views
4. 

   River Markets Sep 21, 2026 · 19:14
   NFL Week 1 generated more than $1B in volume.
   Demand showed across @Kalshi, @Polymarket, @Novig, Rothera, @ProphetX, etc...
   Sports trading has quickly become a multi-venue market.
   If you’re only trading on one venue, you’re leaving better prices and liquidity on the table.

   
   • 3 replies
   • 1 reposts
   • 22 likes
   • 2.7K views
5. 

   River Markets Sep 21, 2026 · 12:13
   if you're building in prediction markets, here are 5 things you need to get right:
   1. solve an actual execution or pricing problem-
   the venues already exist. kalshi, polymarket, limitless, pred….
   and a dozen smaller books already cover the popular events and a decent slice of the long tail
   what's missing is the layer underneath:
   liquidity that's fragmented across books pricing the same event as if they were different instruments.
   build the layer that tackles this, a good example is @river_markets, @magicmarkets and @uselotusxyz
   if your product is another frontend for trading markets…
   be specific about which inefficiency in execution, pricing, discovery or resolution you're actually fixing before you even write a deck
   the idea really to make sure, you are not competing in a saturated niche
   —-
   2. have a real answer for why this needs to be onchain or offchain
   the truth is a prediction market app doesn't need a blockchain to let people bet on an election
   what crypto rails can actually give you is permissionless listing, verifiable and trustless settlement, a more global distribution and composability with existing defi infras.
   and if you are going through the offchain path to target a more defined geography or market, you need to have good reasons for it also
   for example: are you an onchain sport exchange like @predofficial? or just an sportsbook
   this will also help you map your core competitors
   —-
   3. resolution design is the most important part-
   resolution and settlement is the actual product. who writes the rules, how ambiguous wording gets handled, what the challenge window looks like, who eats the loss when a market resolves ugly
   for example sports has clean data feeds and results within minutes.
   politics has ambiguous wording and adverse selection that shows up weeks later
   a poor resolution event can send your product to zero in a single week
   you need to factor all these in.
   —-
   4. liquidity bootstrapping is the real distribution problem here-
   the usual crypto playbook (grow on x, run points, do an airdrop) gets you traders, not depth
   what a market needs on day one is market makers willing to post two-sided quotes on thin books, with real answers on inventory limits, hedging,
   and what happens when a news shock moves the book faster than anyone can react. a book with no depth doesn't get traded
   @Outcomexyz is a good example of projects worth studying here, study how they designed their liquidity rewards program from day one
   —-
   5. token and fee design should compound the market, not just pay people to show up
   builder codes, lp incentives, and rebates work when they make the next market easier to list and the next quote tighter
   an emissions schedule that's only rewarding volume doesn't survive being turned off
   most importantly, ask whether your incentive structure still holds once the rewards stop
   I personally don’t see any reason why a pm should tokenize but that is just my opinion
   there is a still a lot things worth checking but i believe getting these 5 right will give your product a solid foundation

   
   • 6 replies
   • 9 reposts
   • 41 likes
   • 1.4K views
6. 

   River Markets Sep 17, 2026 · 18:28
   It feels like there's a new prediction market every week. @Kalshi @Polymarket @OG_com @Novig
   The same market has a different book depending on where you're trading
   Anyone moving big size indirectly loses thousands due to not optimizing their venues
   If this is you, we can help
   • 1 replies
   • 1 reposts
   • 21 likes
   • 1.5K views
7. 

   River Markets Sep 17, 2026 · 16:54
   Excited to be joining @AlpacaHQ and @tryconviction this Sunday in SF
   • 1 replies
   • 15 likes
   • 993 views
8. 

   River Markets Sep 16, 2026 · 17:42
   The same @NFL lines on @Kalshi and @Polymarket have different prices and liquidity depth.
   We've addressed this & let you merge order books, always routing your trades for the best price and fills.
   • 3 replies
   • 1 reposts
   • 14 likes
   • 1K views
9. 

   River Markets Sep 15, 2026 · 15:53
   100M event contracts traded.
   Four months after launch.
   We’re honored to be the trusted execution partner for the top funds in prediction markets.
   Thank you to all of our partners trading with River Markets.
   Book a demo today
   → https://rivermarkets.com
   • 5 replies
   • 1 reposts
   • 28 likes
   • 3.9K views
10. 

    River Markets Sep 14, 2026 · 21:54
    Saturday morning, @DarioAmodei posted, saying AI labs should slow, expressing worries of AGI.
    After, @elonmusk and @sama agreed.
    Soon, markets on @Polymarket and @Kalshi shifted to reflect this news.
    Tradfi only runs Mon-Fri, but market-moving info doesn't cease on weekends.

    
    • 1 replies
    • 4 reposts
    • 19 likes
    • 1.5K views
11. 

    River Markets Sep 14, 2026 · 17:54
    What happens when a PM settles before the event is over?
    The clock hit zero, and @Kalshi paid out @WMU_Football holders
    Officials reviewed the final play and restored one second
    Michigan used it to complete a Hail Mary, winning 13–12...
    Read article: https://www.rivermarkets.com/insights/kalshi-michigan-premature-settlement.html

    
    • 2 reposts
    • 17 likes
    • 1.1K views
12. 

    River Markets Sep 11, 2026 · 16:59
    Placing any large order on @Kalshi or @Polymarket tells your counterparty your thesis.
    Use iceberg orders to get better, gradual fills which don't shock the book.
    • 5 replies
    • 3 reposts
    • 39 likes
    • 5.3K views
13. 

    River Markets Sep 10, 2026 · 18:55
    This is a strong example of what prediction markets are becoming: not isolated venues, but fragmented liquidity that can be intelligently routed.
    If the same outcome is priced differently across Kalshi and Polymarket, the edge isn't just choosing the right event, it's finding the best execution.
    That's where River Markets gets particularly interesting: aggregating markets, improving price discovery and reducing friction for the user.
    As prediction markets mature, the infrastructure connecting them could become just as important as the markets themselves.
    One to watch. 👀 @river_markets
    • 3 reposts
    • 4 likes
    • 238 views
14. 

    River Markets Sep 10, 2026 · 17:01
    The same event can trade at entirely different prices on @Kalshi and @Polymarket
    Stop overpaying on each trade.
    Always get the best price on http://rivermarkets.com

    
    • 3 replies
    • 4 reposts
    • 25 likes
    • 1.9K views
15. 

    River Markets Sep 9, 2026 · 17:08
    Stop leaking money on @Kalshi @Polymarket
    Get a 4% price improvement on each trade 👇
    • 3 replies
    • 4 reposts
    • 16 likes
    • 868 views
16. 

    River Markets Sep 8, 2026 · 16:39
    Focus on trading, not maintaining adapters.
    Every prediction market has its own API, market identifiers, order syntax, and updates. Adding another venue means another integration to build, monitor, and fix.
    River gives you one API across prediction markets, so you can spend your time finding alpha, not building infra.
    Read more:
    https://www.rivermarkets.com/insights/unified-prediction-market-api.html
    • 2 replies
    • 2 reposts
    • 13 likes
    • 765 views
17. 

    River Markets Aug 18, 2026 · 14:59
    The hidden 2.4% tax on your prediction market trades
    If you trade size in prediction markets, you already know the drill: the bigger your order, the worse your fill. We ran 50k contracts through every major venue during the July fed decision, all fees in.
    Polymarket US was $3,033 more expensive than River. Polymarket , $1,425. Kalshi, $945.
    Check out the full article below ⬇️
    https://www.rivermarkets.com/insights/prediction-market-execution-economics.html

    
    • 6 replies
    • 2 reposts
    • 28 likes
    • 3.2K views
18. 

    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
    • 34 replies
    • 8 reposts
    • 125 likes
    • 18.8K views
19. 

    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
    • 17 replies
    • 4 reposts
    • 61 likes
    • 8.5K views
20. 

    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!
    • 11 replies
    • 2 reposts
    • 41 likes
    • 3.6K views

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