Smart Contract

The on-chain component of Opentip. Written in Solidity, deployed on Base.

Deployment

Testnet (Base Sepolia)

0xeD13dB8234d437771e115419BF7498Ddef90Dc8DBasescan →

Mainnet (Base)

Not yet deployed

Solidity

^0.8.26

License

MIT

Lines

298

USDC (Testnet)

0x036CbD53842c5426634e7929541eC2318f3dCF7e

Inheritance

The contract inherits from four OpenZeppelin libraries:

Ownable2Step

Two-step ownership transfer for safety

Pausable

Emergency pause/unpause mechanism

ReentrancyGuard

Protection against reentrancy attacks

EIP712

Off-chain typed signature verification

Constants

Constant	Value	Description
MIN_TIP	1e6	Minimum tip: 1 USDC ($1)
MAX_FEE_BPS	1000	Maximum fee: 10%
MAX_REPO_ID_LENGTH	200	Maximum characters for a repo ID

Functions

User Functions

Function	Parameters	Returns	Modifier	Description
registerRepo	repoId, payoutAddress, expiry, nonce, signature	—	whenNotPaused	Register a repo with an EIP-712 signed permit. Validates format, expiry, and signature.
updatePayoutAddress	repoId, newAddress	—	whenNotPaused	Rotate the payout wallet for a registered repo. Only callable by current payout address.
receiveTip	repoId, usdcAmount	—	nonReentrant, whenNotPaused	Accept a USDC tip. Pulls USDC from msg.sender, splits fee, credits pending balance.
claim	repoId	—	nonReentrant, whenNotPaused	Withdraw all pending USDC for a repo. Only callable by the payout address.

Admin Functions

Function	Parameters	Returns	Modifier	Description
pause	—	—	onlyOwner	Emergency pause. Blocks register, update, tip, and claim.
unpause	—	—	onlyOwner	Resume operations after a pause.
setFeeBps	newFeeBps	—	onlyOwner	Update platform fee. Capped at MAX_FEE_BPS (1000 = 10%).
setTreasuryAddress	newTreasury	—	onlyOwner	Change the treasury address. Migratable to Gnosis Safe.
withdrawTreasury	amount	—	onlyOwner, nonReentrant	Withdraw accumulated fees to the treasury address.
setRegistrarSigner	newSigner	—	onlyOwner	Rotate the EIP-712 registrar signer. Old key is immediately invalidated.
adminReassignPayout	repoId, newAddress	—	onlyOwner	Emergency recovery: reassign payout address if wallet key is lost.

View Functions

Function	Parameters	Returns	Modifier	Description
getPendingBalance	repoId	uint256	view	USDC available to claim for a repo.
getPayoutAddress	repoId	address	view	The wallet that can claim tips for a repo.
getTotalTipped	repoId	uint256	view	Lifetime gross tip amount for a repo.
getTotalTipCount	repoId	uint256	view	Lifetime tip count for a repo.
getFeeBps	—	uint256	view	Current platform fee in basis points.
getTreasuryBalance	—	uint256	view	Accumulated unwithdrawn fees.
isRegistered	repoId	bool	view	Whether a repo has been registered.

Events

Event	Parameters	Description
RepoRegistered	repoId, payoutAddress (indexed), timestamp	Emitted when a new repo is registered.
PayoutAddressUpdated	repoId, oldAddress, newAddress (indexed)	Emitted when a payout wallet is rotated.
TipReceived	tipper (indexed), repoId, usdcAmount, feeAmount, timestamp	Emitted on every tip.
Claimed	payoutAddress (indexed), repoId, amount, timestamp	Emitted when a developer claims tips.
TreasuryWithdrawn	to (indexed), amount, timestamp	Emitted when treasury funds are withdrawn.
FeeUpdated	oldFeeBps, newFeeBps	Emitted when the platform fee changes.
TreasuryAddressUpdated	oldTreasury (indexed), newTreasury (indexed)	Emitted when the treasury address changes.
RegistrarSignerUpdated	oldSigner (indexed), newSigner (indexed)	Emitted when the registrar signer is rotated.
AdminPayoutReassigned	repoId, oldAddress, newAddress, admin (indexed)	Emitted when an admin reassigns a payout address.

Fee Structure

The platform fee is expressed in basis points (bps). 500 bps = 5%. The fee is capped at 1000 bps (10%) and enforced in both the constructor and setFeeBps.

How fees flow

Tipper sends USDC via receiveTip()
Fee = usdcAmount * feeBps / 10000
Fee credited to treasuryBalance
Net amount (usdcAmount - fee) credited to repo's pendingBalance
Developer calls claim() to withdraw their share
Owner calls withdrawTreasury() to collect fees

Registration Flow

Registration uses EIP-712 typed signatures to prevent squatting. The process:

Server verifies GitHub ownership (owner or write collaborator)
Server signs a Register typed struct with the registrar key
User submits the signature on-chain via registerRepo()
Contract verifies the registrar signer matches, stores the repo

Repo ID validation rules

Must be lowercase (no uppercase A-Z)
Must contain exactly one / separator
Minimum 3 characters, maximum 200
No leading or trailing /
Must not be already registered

EIP-712 domain

{
  name: "Opentip",
  version: "1",
  chainId: 84532,
  verifyingContract: "0xeD13dB8234d437771e115419BF7498Ddef90Dc8D"
}

Security Properties

Reentrancy protection

All state-changing external functions (receiveTip, claim, withdrawTreasury) use nonReentrant.

Pausable

The owner can pause the contract in an emergency. Paused contract blocks registration, tip updates, tips, and claims.

Two-step ownership

Uses Ownable2Step — ownership transfer requires the new owner to accept. Prevents accidental transfer to a wrong address.

Checks-effects-interactions

All functions update state before making external calls (USDC transfers), following the CEI pattern.

Minimum tip enforcement

The contract rejects tips below 1 USDC (MIN_TIP = 1e6) to prevent dust attacks.

Source code

The full contract source is available at contracts/src/Opentip.sol in the repository.

View on GitHub →