> For the complete documentation index, see [llms.txt](https://docs.propellerheads.xyz/tycho/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.propellerheads.xyz/tycho/for-solvers/execution.md). # Execution
Tycho Execution provides tools for **encoding and executing swaps** against Tycho Router and protocol executors. It is divided into two main components: * **Encoding**: A Rust crate that encodes swaps and generates calldata for execution. * **Executing**: Solidity contracts for executing trades on-chain. The source code for **Tycho Execution** lives at [`crates/tycho-execution`](https://github.com/propeller-heads/tycho-indexer/tree/main/crates/tycho-execution) inside the [Tycho monorepo](https://github.com/propeller-heads/tycho-indexer). For a practical example of its usage, please refer to our [Quickstart](/tycho/readme.md). ## Token transfers You can transfer tokens in one of three ways with Tycho Execution: * Permit2 * Standard ERC20 Approvals * Using Vault funds See how to change between these options when encoding [here](/tycho/for-solvers/execution/encoding.md#usertransfertype). ### Permit2 Tycho Execution supports **Permit2** for token approvals. Before executing a swap via our router, you must approve the **Permit2 contract** for the specified token and amount. This ensures the router has the necessary permissions to execute trades on your behalf. Permit2 handling is **not** part of the encoding step. You are responsible for creating and signing the permit yourself. The `Permit2` utility struct is publicly exported from the encoding crate, so you can use it to build the `PermitSingle` and obtain the data needed for signing. For more details on Permit2 and how to use it, see the [**Permit2 official documentation**](https://docs.uniswap.org/contracts/permit2/overview). ### **Standard ERC20 Approvals** Tycho also supports traditional ERC20 approvals. In this model, you explicitly call `approve` on the token contract to grant the router permission to transfer tokens on your behalf. This is widely supported and may be preferred in environments where Permit2 is not yet available. ### Using the Vault The TychoRouter includes a built-in vault ([ERC6909](https://eips.ethereum.org/EIPS/eip-6909)) that lets you deposit, hold, and withdraw tokens directly in the router contract. The vault tracks per-user balances, so your tokens are only accessible by you. The router draws from your deposited balance instead of performing a `transferFrom` on your wallet. This saves gas (no approval or external transfer needed) and lets you use fees, proceeds from previous trades, or pre-positioned liquidity directly. Fees earned through the fee-taking system are automatically credited to the fee receiver's vault balance, making them immediately available for future swaps or withdrawals. More on the Vault [here](/tycho/for-solvers/execution/vault.md). ## Security and Audits The Tycho Router V2 and V3 have been audited by [Maximilian Krüger](https://snd.github.io/). Past audits are [here](https://github.com/propeller-heads/tycho-indexer/tree/main/crates/tycho-execution/docs/audits). ### Security Checklist Follow this checklist when using TychoRouter. It covers essential security requirements but is not exhaustive. * **Always set `minAmountOut`** on TychoRouter's `swap...` functions to the minimum acceptable output amount. * Example: if you expect 1000 USDC and accept 5% slippage, set `minAmountOut` to `950 * 10**6`. * Setting `minAmountOut` to `1` means you may receive just `1` due to faulty swap sequences, slippage or an attack. * **Verify the price data used for `minAmountOut`** against at least one other independent price source. Incorrect price data may set `minAmountOut` too low, resulting in significant losses. * **Never approve infinite allowances**, including those for Permit2. * **Set Permit2 allowance and deadline as low as is practical.** If you discover potential security issues or have suggestions for improvements, please reach out through our official channels.