# Role of a Solver

On SYMMIO, traders don’t match against a central order book. They express intents, which are requests which say “I want to go long or short this market, here’s my size, my price, and the counterparties I wish to trade with.*”* Those intents are picked up by a network of independent counterparties called [solvers](https://docs.symm.io/getting-started/glossary-of-terms). A solver is the party that decides whether to take the other side of a trade, quote prices, and manage the risk that comes with it.

When you run a solver, you are acting as the [Party B](https://docs.symm.io/getting-started/glossary-of-terms) in the protocol. Your address is whitelisted on the SYMMIO contracts so you are allowed to lock quotes, open positions, and hold shared risk with traders. Once a trader sends a quote on-chain, your infrastructure listens for the event, pulls in the quote details, and runs internal checks: is this symbol supported, is the account allowed, do you have enough collateral, and does the price fit your strategy? If everything passes, you lock the quote and open the position on-chain, optionally hedging the exposure elsewhere at the same time.

Solvers are also responsible for collateral management and solvency on their side. Before opening or closing a position, the contracts and [Muon oracle](https://docs.symm.io/api-endpoints-and-deployments/muon-api) verify that both you and the trader have enough margin, and that the prices you’re using are valid. You decide how much capital to allocate to each trader, how much open interest to allow per market, and when to settle unrealized profits so that positions can be safely closed. Your risk model is entirely up to you, however it must conform to the protocol's solvency rules enforced on the contracts.

Solvers also play a key role in the user experience. Frontend Applications rely on solver APIs to show things like markets, prices and funding data. When a trader wishes to do things like [instantly open a trade](https://docs.symm.io/trader-documentation/how-trading-works-in-symmio/instant-trading), they delegate certain functions to you so that you can open and close positions without asking them to sign every transaction. When they'd like to set a [take profit or stop loss](https://docs.symm.io/trader-documentation/how-trading-works-in-symmio/using-take-profit-and-stop-loss), your **conditional orders** service will watch the market and submit the close request when their conditions are hit. From the trader’s perspective, the frontend application feels like a fast, seamless exchange.
