Uniswap V4

Swap tokens and read pool state on Uniswap V4 (Base, Ethereum). Use when the agent needs to: (1) swap ERC20 tokens or ETH via Uniswap V4, (2) get pool info (price, tick, liquidity, fees), (3) find the best pool for a token pair, (4) quote expected swap output via the on-chain V4Quoter, (5) set up Permit2 approvals for the Universal Router, or (6) execute exact-input swaps with proper slippage protection. Supports Base and Ethereum mainnet, plus Base Sepolia testnet. TypeScript with strict types. Write operations need a private key via env var.

Swap tokens and read pool state on Uniswap V4 via the Universal Router.

Chains: Base (8453), Ethereum (1), Base Sepolia (84532)

Contract	Base	Ethereum
PoolManager	0x498581fF718922c3f8e6A244956aF099B2652b2b	0x000000000004444c5dc75cB358380D2e3dE08A90
UniversalRouter	0x6ff5693b99212da76ad316178a184ab56d299b43	0x66a9893cC07D91D95644AEDD05D03f95e1dBA8Af
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3	0x000000000022D473030F116dDEE9F6B43aC78BA3
StateView	0xa3c0c9b65bad0b08107aa264b0f3db444b867a71	0x7ffe42c4a5deea5b0fec41c94c136cf115597227
V4Quoter	0x0d5e0f971ed27fbff6c2837bf31316121532048d	0x52f0e24d1c21c8a0cb1e5a5dd6198556bd9e1203

Addresses from docs.uniswap.org/contracts/v4/deployments, verified 2026-02-08.

Decision Tree

1. Read pool state? → src/pool-info.ts (free, no gas, no key)
2. Get swap quote? → src/quote.ts (free, uses on-chain V4Quoter)
3. Approve tokens? → src/approve.ts (write, ~100K gas, needs PRIVATE_KEY)
4. Execute swap? → src/swap.ts (write, ~300-350K gas, needs PRIVATE_KEY)
5. First time with an ERC20? → Run approve first, or use --auto-approve on swap

Scripts Reference

All scripts in src/. Run with npx tsx. Pass --help for usage.

pool-info.ts — Read Pool State (free)

Returns pool ID, sqrtPriceX96, tick, liquidity, fees, token symbols/decimals. Auto-detects the best pool by liquidity (or specify --fee/--tick-spacing).

npx tsx src/pool-info.ts --token0 ETH --token1 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 --chain base --rpc $BASE_RPC_URL

Env: BASE_RPC_URL or ETH_RPC_URL (or pass --rpc)

quote.ts — Quote Swap Amounts (free)

Quotes exact input amounts via the on-chain V4Quoter contract (simulation, no tx). Returns expected output amount and gas estimate.

npx tsx src/quote.ts \
  --token-in ETH \
  --token-out 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --amount 10000000000000000 \
  --chain base \
  --rpc $BASE_RPC_URL

Env: BASE_RPC_URL or ETH_RPC_URL

approve.ts — Set Up Token Approvals (write)

Two-step Permit2 flow: ERC20 → Permit2, then Permit2 → Universal Router. Skips if already approved. Only needed for ERC20 tokens (not ETH).

PRIVATE_KEY=0x... npx tsx src/approve.ts \
  --token 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --chain base \
  --rpc $BASE_RPC_URL \
  --json

Env: PRIVATE_KEY (required), BASE_RPC_URL

swap.ts — Execute Swap (write)

Exact-input swap via Universal Router. Quotes expected output first, applies slippage, then sends the transaction.

PRIVATE_KEY=0x... npx tsx src/swap.ts \
  --token-in ETH \
  --token-out 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --amount 10000000000000000 \
  --slippage 50 \
  --chain base \
  --rpc $BASE_RPC_URL \
  --json

With auto-approval (sets up Permit2 if needed):

PRIVATE_KEY=0x... npx tsx src/swap.ts \
  --token-in 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --token-out ETH \
  --amount 25000000 \
  --slippage 100 \
  --auto-approve \
  --chain base \
  --rpc $BASE_RPC_URL

Options: --slippage <bps> (default 50 = 0.5%), --recipient <addr>, --auto-approve, --json Env: PRIVATE_KEY (required), BASE_RPC_URL

Token Input

• ETH or eth → native ETH (address(0) in V4)
• Contract address → ERC20 token
• Common Base tokens: USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, WETH 0x4200000000000000000000000000000000000006

Environment Variables

Variable	Used By	Required	Description
PRIVATE_KEY	approve, swap	Yes*	Wallet private key (never CLI!)
BASE_RPC_URL	all (Base)	No	Base mainnet RPC URL
ETH_RPC_URL	all (Ethereum)	No	Ethereum mainnet RPC URL
BASE_SEPOLIA_RPC_URL	all (testnet)	No	Base Sepolia RPC URL

* Only required for write operations. Read operations (pool-info, quote) don't need a key.

V4 Architecture Notes

• Singleton PoolManager holds all pools in one contract
• State read via StateView contract (wraps PoolManager storage)
• Swaps: Universal Router → PoolManager via V4_SWAP command
• Approvals: ERC20 → Permit2 → Universal Router (two-step)
• Pool ID: keccak256(abi.encode(currency0, currency1, fee, tickSpacing, hooks))
• Currency ordering: currency0 < currency1 by numeric value. ETH = address(0)
• Action sequence: SWAP_EXACT_IN_SINGLE (0x06) + SETTLE_ALL (0x0c) + TAKE_ALL (0x0f)
• See references/v4-encoding.md for full encoding reference

Error Handling

Error	Cause	Fix
No V4 pool found	Pair not listed on V4 for this chain	Check token addresses
Quote failed	Pool exists but can't simulate swap	Check amount, pool may lack liq
PRIVATE_KEY required	Missing env var for write operation	export PRIVATE_KEY=0x...
No RPC URL	Missing RPC config	Pass --rpc or set env var
Tx reverts	Insufficient balance, expired, slippage	Check balance, increase slippage
uint128 max	Amount too large for V4	Use smaller amount

SECURITY

• PRIVATE_KEY must be provided via an environment variable or secret manager only.

• NEVER paste or send PRIVATE_KEY in chat.

• NEVER commit PRIVATE_KEY (or .env files) to git.

• Treat stdout/stderr as public logs (CI, terminals, chat). CI tests ensure the PRIVATE_KEY value is never printed.

• NEVER pass private keys as CLI arguments (rejected by all scripts)

• Private keys accepted via PRIVATE_KEY env var only

• All inputs validated: addresses (format), amounts (BigInt bounds), slippage (0-10000)

• No eval(), no exec(), no shell commands — pure TypeScript

• BigInt used everywhere for token amounts (no floating point, no overflow)

Testing

npm run test:unit      # Unit tests (no network)
npm run test:fork      # Fork tests (needs: anvil --fork-url https://mainnet.base.org)
npm run test:testnet   # Testnet reads (Base Sepolia)
npm run test:mainnet   # Mainnet smoke tests (read-only)
npm run security       # Security scan

References

• V4 encoding reference: references/v4-encoding.md
• Contract addresses: references/addresses.md
• V4 architecture: references/v4-architecture.md