Executing the solutions

Once you have Fynd running, it's time to get some solutions, validate them, and execute, if desired.

Tutorial: Quote, Simulate & Execute Swaps

This example shows how to get swap quotes from a running Fynd instance, simulate them, and optionally execute on-chain using tycho-execution.

Prerequisites

1. Running solver: Start Fynd first. If you haven't, see Quickstart

2. Tycho API key: Required to load token data from the Tycho API

3. RPC URL: Required for simulation and execution (Ethereum mainnet or other supported chain)

4. Private key: Required only for execution or Permit2 simulation. For basic simulation, use --sender to impersonate any account.

Environment Variables

Variable	Required	Description
TYCHO_URL	No	Tycho indexer URL (defaults to tycho-beta.propellerheads.xyz)
TYCHO_API_KEY	Yes	API key for Tycho indexer
RPC_URL	For simulation/execution	Ethereum RPC endpoint
PRIVATE_KEY	For execution	Wallet private key (hex, no 0x prefix)
TENDERLY_ACCESS_KEY	For Tenderly	Tenderly API access key
TENDERLY_ACCOUNT	For Tenderly	Tenderly account slug
TENDERLY_PROJECT	For Tenderly	Tenderly project slug

Tutorial

1. Start Fynd

In one terminal:

export TYCHO_URL=tycho-beta.propellerheads.xyz
export TYCHO_API_KEY=your_api_key
export RPC_URL=https://your-rpc-provider.com/v1/your_key

RUST_LOG=info cargo run --release -- \
  --tycho-url tycho-beta.propellerheads.xyz \
  --protocols uniswap_v2,uniswap_v3,uniswap_v3,vm:curve \
  --min-tvl 50

Wait for it to be ready: Quickstart

2. Get a quote (no private key needed)

In another terminal:

export TYCHO_URL=tycho-beta.propellerheads.xyz
export TYCHO_API_KEY=your_api_key
cargo run --example tutorial -- --sell-amount 100

This displays a quote for swapping 100 USDC to WETH (default tokens). Customize with --sell-token and --buy-token.

3. Simulate without private key

Use --sender to simulate as any address without exposing a private key:

export RPC_URL=https://your-rpc-provider.com/v1/your_key
cargo run --example tutorial -- \
  --sell-amount 100 \
  --simulate-only \
  --sender 0xYourAddressHere

This simulates using standard ERC-20 transferFrom (not Permit2). The simulation fails if the sender lacks token balance.

4. Simulate with private key (Permit2)

For full Permit2 simulation with signature:

export PRIVATE_KEY=your_private_key_hex
export RPC_URL=https://your-rpc-provider.com/v1/your_key
cargo run --example tutorial -- \
  --sell-amount 100 \
  --simulate-only

5. Simulate with Tenderly

export TENDERLY_ACCESS_KEY=your_tenderly_key
export TENDERLY_ACCOUNT=your_account
export TENDERLY_PROJECT=your_project
cargo run --example tutorial -- \
  --sell-amount 100 \
  --simulate-only \
  --use-tenderly

6. Execute a swap (mainnet!)

export PRIVATE_KEY=your_private_key_hex
cargo run --example tutorial -- --sell-amount 10

You'll be prompted to choose: Simulate, Execute, or Cancel.

7. Custom tokens and protocols

cargo run --example tutorial -- \
  --sell-token 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 \
  --buy-token 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 \
  --sell-amount 1000 \
  --protocols "uniswap_v2,uniswap_v3"

CLI Reference

Flag	Default	Description
--sell-token	USDC address	Token address to sell
--buy-token	WETH address	Token address to buy
--sell-amount	10.0	Amount to sell (human readable)
--chain	ethereum	Blockchain (currently only ethereum is available)
--solver-url	http://localhost:3000	Solver API URL
--tvl-threshold	10.0	Min pool TVL in ETH
--simulate-only	false	Only simulate, don't prompt for execution
--use-tenderly	false	Use Tenderly instead of eth_simulate
--slippage-bps	50	Slippage tolerance (50 = 0.5%)
--protocols	(all available)	Comma-separated protocol systems (fetched from API if not specified)
--sender	-	Sender address for simulation (use with --simulate-only)

Security Notes

1. Never expose your private key. Use environment variables, never CLI arguments.

2. Simulate first. Always test with --simulate-only before executing real transactions.

3. Slippage protection. The default 0.5% slippage may not work for large trades or volatile markets. Adjust --slippage-bps accordingly.

4. Mainnet warning. Executing swaps sends real transactions. Start with small amounts. All routes execute through the Tycho Router contract.

5. Verify routes. Review the displayed route before execution. Multi-hop routes through low-liquidity pools can result in worse execution.

6. Prices are indicative. Quotes reflect the best route at query time but are not guaranteed on-chain. On-chain pool states change every block, and RFQ quotes have short expiry windows. The longer you wait to execute, the more the price may drift.

Troubleshooting

"Solver is not healthy": Wait for the solver to finish loading market data. Check the solver terminal for progress.

"Sell/buy token not found": Ensure the token address is correct and the token exists on Tycho's indexer.

"Simulation failed": Your RPC provider may not support eth_simulate. Try --use-tenderly or a different RPC.

"No route found": Fynd couldn't find a path between your tokens. Try adjusting --tvl-threshold or check that both tokens have enough on-chain liquidity.

"Swap encoder not found for protocol": The route uses a protocol not included in --protocols. Either add the protocol or the component wasn't fetched from the API.