Developers

Reactivate: Automated Monitoring and Funding for Reactive Contracts

Reactive Network

Dec 2, 2025 — 6 min read

Keeping Reactive Contracts (RCs) funded is a constant maintenance task. If a contract runs out of tokens, it stops executing. Thus, missed calls, stalled logic, and broken integrations follow. For developers working with RCs that fire on frequent events, this becomes a persistent operational load.

Most builders end up watching balances manually and refilling contracts before they go dark. It works for small projects, but it doesn’t hold up in production. One missed top-up can translate into hours of lost execution.

Reactivate removes this upkeep. It monitors your contracts, tracks their token balances, and refills them automatically when they drop below the threshold. If a contract does slip into an inactive state, Reactivate detects it and invokes the functions needed to bring it back online.

The first version of Reactivate was built during Reactive Network’s Hackathon in September 2025.

Try Reactivate | See GitHub Project | Watch Loom Demo

DApp Flow

Here’s what the DApp flow looks like:

Create Funding AccountA dedicated account is generated and funded with REACT for Reactive Contracts, or ETH/USDC for callback contracts on Base and other supported chains.
Configure DeploymentContract addresses are registered, events to watch are defined, balance thresholds are set, and top-up amounts are chosen. The monitoring infrastructure is deployed from these inputs.
Automatic MonitoringMonitoring contracts track the configured events and check balances. When a threshold is reached, the system transfers the required tokens automatically.
Instant ReactivationIf any monitored contract becomes inactive, the system automatically triggers `coverDebt()` to restore it and maintain application responsiveness.

Under the Hood

Funder Contract

RCs need a steady supply of funds to remain operational. The funder contract automates this by watching balances and replenishing them when they fall below the set threshold. It listens for events emitted by the callback contract, checks the balances of both the Reactive and callback contracts, and performs top-ups when necessary. If either contract becomes inactive due to accumulated debt, the funder invokes `coverDebt()` to clear it.

Deployment of a new funder instance performs several setup steps: determining the developer’s account, validating its balance, withdrawing initial funds, whitelisting the funder, and emitting a setup event.

function createFunder(
address dev,
address callbackContract,
address reactiveContract,
uint256 refillValue,
uint256 refillThreshold
) payable external {
address devAccount = IAccountFactory(accountFactory).devAccounts(dev);
uint256 devAccountBalance = devAccount.balance;
uint256 withdrawAmount = (refillValue * 2);
uint256 initialFundAmount = withdrawAmount + 2 ether;

require(devAccountBalance >= withdrawAmount, "Not enough REACT in dev account");

Funder newReactiveFunder = new Funder{value: initialFundAmount}(
callbackContract,
reactiveContract,
refillValue,
refillThreshold,
devAccount
);

address funderAddress = address(newReactiveFunder);
IDevAccount(devAccount).withdraw(address(this), initialFundAmount);
IDevAccount(devAccount).whitelist(funderAddress);
latestDeployed = funderAddress;

emit Setup(dev, funderAddress);
}

Reactive Contract

The RC observes callback events and initiates the funder’s logic. Deployment provides it with an initial balance and registers the funder, callback contract, and event topic it should react to.

function createReactive(
address funderContract,
address callbackContract,
uint256 eventTopic
) payable external {
Reactive newReactive = new Reactive{value: 2 ether}(
funderContract,
callbackContract,
eventTopic
);
latestDeployed = address(newReactive);

emit Setup(msg.sender, address(newReactive));
}

Automatic Balance Refills

When a monitored contract’s balance drops below the threshold, the funder refills it automatically. It sends the required amount and withdraws the same value from the developer account. Each refill emits a dedicated event; if no refill is needed, the funder emits a simple callback-handled event.

Reactivating Inactive Contracts

If the callback or Reactive ontract accumulates debt and becomes inactive, the funder resolves it by calling `coverDebt()` on the affected contract.

Bridging Tokens

To supply developer accounts with ETH from Base, the system uses a Bridge contract. Developers send ETH to the bridge; deposits trigger a `Received(address,uint256)` event. The RC listens for these events and initiates a callback that transfers the appropriate amount of REACT to the recipient.

Deposits above a fixed threshold are refunded immediately; valid deposits emit the event that drives the downstream flow.

receive() external payable {
if (msg.value > 0.00024 ether) {
(bool success, ) = msg.sender.call{value: msg.value}("");
require(success, "Payment value exceeded.");
} else {
emit Received(
msg.sender,
msg.value
);
}
}

When the RC receives a `Received` event, it invokes `react()`. It extracts the depositor and amount, encodes the callback payload, and emits a `Callback` event.

function react(LogRecord calldata log) external vmOnly {
address recipient = address(uint160(log.topic_1));
uint256 sentValue = uint256(log.topic_2);

bytes memory payload = abi.encodeWithSignature(
"callback(address, address, uint256)",
address(0),
recipient,
sentValue
);

emit Callback(
REACT_ID,
callbackHandler,
GAS_LIMIT,
payload
);
}

The callback contract then determines whether the depositor has a dedicated developer account. Funds are forwarded accordingly, using the configured conversion rate in both cases.

Closing Note

Reactivate reduces the operational load of maintaining Reactive on-chain systems by removing the need for constant manual balance checks. Automated monitoring, refills, and recovery keep contracts responsive even under high-frequency execution. By coordinating funders, Reactive Contracts, callback logic, and bridging flows, the system preserves continuity across chains and event types. Developers can focus on building instead of managing thresholds, refills, or downtime.

The app also shows that writing the Solidity logic for Reactive Contracts is entirely within reach. Hackathon participants built it under pressure, which means it’s doable — demanding, but doable. If you want to push your limits, consider joining Reactive Bounties.

About Reactive Network

Reactive is an EVM-compatible execution layer for dApps built with Reactive contracts. These contracts differ from traditional smart contracts by using inversion-of-control for the transaction lifecycle, triggered by data flows across blockchains rather than by direct user input.

Reactive contracts listen for event logs from multiple chains and execute Solidity logic in response. They can determine autonomously when to transmit data to destination chains, enabling conditional cross-chain state changes. The network delivers fast and cost-effective computation via a proprietary parallelized EVM implementation.

Build once — react everywhere!