ERC20 Cumulative Outflow Breaker

When to Use This Pattern

Monitors and limits cumulative token outflows to prevent catastrophic asset loss during exploits, creating a response window for protocol operators. Use it for lending reserves, vault custody, bridge escrows, treasuries, liquidity pools, and other contracts where rapid ERC20 withdrawals are a critical risk. This is a V2 Reshiram circuit-breaker pattern. The trigger/precompile machinery collects token outflow into one bucket per block and evaluates those per-block buckets over the rolling window. The assertion does not need its own storage for this accounting.

What This Pattern Checks

Registers a percentage-based cumulative outflow limit:

registerAssertionSpec(AssertionSpec.Reshiram): Registers the assertion as a Reshiram assertion.
watchCumulativeOutflow(token, thresholdBps, windowDuration, assertFn): Collects ERC20 outflow into one bucket per block and watches the buckets over a rolling window.
ph.outflowContext(): Reads the token context inside the triggered assertion.
Reverts when cumulative outflow breaches the configured threshold.

The assertion does not manually store balances or rolling counters. The Reshiram circuit-breaker trigger tracks the per-block buckets across the window and invokes the assertion when the limit is exceeded.

The current Phylax app and Linea deployment support the V1 assertion specification. Treat this V2 Reshiram pattern as a local or development example until the target deployment supports V2.

For more information about cheatcodes, see the Cheatcodes Documentation.

Assertion Pattern

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import {Assertion} from "credible-std/Assertion.sol";
import {AssertionSpec} from "credible-std/SpecRecorder.sol";
import {PhEvm} from "credible-std/PhEvm.sol";

contract ERC20CumulativeOutflowBreakerAssertion is Assertion {
    address public immutable monitoredToken;
    uint256 public immutable outflowThresholdBps;
    uint256 public immutable outflowWindowDuration;

    constructor(address monitoredToken_, uint256 outflowThresholdBps_, uint256 outflowWindowDuration_) {
        registerAssertionSpec(AssertionSpec.Reshiram);

        monitoredToken = monitoredToken_;
        outflowThresholdBps = outflowThresholdBps_;
        outflowWindowDuration = outflowWindowDuration_;
    }

    function triggers() external view override {
        watchCumulativeOutflow(
            monitoredToken,
            outflowThresholdBps,
            outflowWindowDuration,
            this.assertCumulativeOutflow.selector
        );
    }

    /// @notice Reverts when cumulative token outflow breaches the rolling-window limit.
    /// @dev The Reshiram trigger tracks the window and calls this function only after breach.
    function assertCumulativeOutflow() external view {
        PhEvm.OutflowContext memory ctx = ph.outflowContext();
        require(ctx.token == monitoredToken, "ERC20Outflow: wrong token context");

        revert("ERC20Outflow: cumulative outflow breaker tripped");
    }
}

Full examples and mock protocol code are available in credible-std.

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Explanation

Reference

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What This Pattern Checks

Assertion Pattern

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