Sablier Flow

This repository contains the smart contracts for Sablier Flow protocol. Flow is a debt tracking protocol that tracks tokens owed between two parties, enabling indefinite token streaming. A Flow stream is characterized by its rate per second (rps). The relationship between the amount owed and time elapsed is linear and can be defined as:

$$\text{amount owed} = rps \cdot \text{elapsed time}$$

Flow protocol can be used in several areas of everyday finance, such as payroll, distributing grants, insurance premiums, loans interest, token ESOPs etc. If you are looking for vesting and airdrops, please refer to our Lockup protocol.

Features

1. Flexible deposit: A stream can be funded with any amount, at any time, by anyone, in full or in parts.
2. Flexible duration: A stream can be created with no specific start or end time. It can run indefinitely.
3. Pause: A stream can be paused by the sender and can later be restarted without losing track of previously accrued debt.
4. Refund: Unstreamed amount can be refunded back to the sender at any time.
5. Void: Voiding a stream implies it cannot be restarted anymore. Voiding an insolvent stream forfeits the uncovered debt. Either party can void a stream at any time.
6. Withdraw: it is publicly callable as long as to is set to the recipient. However, a stream’s recipient is allowed to withdraw funds to any address.

Install

Node.js

This is the recommended approach.

Install Flow using your favorite package manager, e.g. with Bun:

bun add @sablier/flow

Then, if you are using Foundry, you need to add these to your remappings.txt file:

@sablier/flow/=node_modules/@sablier/flow/
@openzeppelin/contracts/=node_modules/@openzeppelin/contracts/
@prb/math/=node_modules/@prb/math/

Git Submodules

This installation method is not recommended, but it is available for those who prefer it.

Install the submodule using Forge:

forge install --no-commit sablier-labs/flow

Then, install the project's dependencies:

forge install --no-commit OpenZeppelin/openzeppelin-contracts@v5.0.2 PaulRBerg/prb-math#95f00b2

Finally, add these to your remappings.txt file:

@sablier/flow/=lib/flow/
@openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/
@prb/math/=lib/prb-math/

Usage

This is just a glimpse of Sablier Flow. For more guides and examples, see the documentation and the technical file.

import { ISablierFlow } from "@sablier/flow/src/interfaces/ISablierFlow.sol";

contract MyContract {
  ISablierFlow immutable flow;

  function doSomethingWithFlow(uint256 streamId) external {
    uint128 totalDebt = flow.totalDebtOf(streamId);
    // ...
  }
}

Contributing

Feel free to dive in! Open an issue, start a discussion or submit a PR. For any concerns or feedback, please join our Discord server.

Refer to CONTRIBUTING guidelines if you wish to create a PR.

License

The primary license for Sablier Flow is the Business Source License 1.1 (BUSL-1.1), see LICENSE.md. However, there are exceptions:

• All files in src/ with the exception of SablierFlow.sol are licensed under GPL-3.0-or-later. Refer to LICENSE-GPL.md for preamble.
• All files in script/ are licensed under GPL-3.0-or-later.
• All files in tests/ are unlicensed (as indicated in their SPDX headers).