# BreakerBox

**BreakerBox** is an on-chain circuit breaker for oracle feeds. It maintains a state per price feed (e.g. trading allowed or suspended) and supports modular addition of price feeds and breaker logic. In **Mento V3**, the **OracleAdapter** reads from BreakerBox when supplying the FPMM pool with a valid rate; if a breaker has tripped, the adapter returns invalid and swaps revert. This protects pools from trading on stale or out-of-bounds oracle data.

For **FX pairs**, Mento also uses a **MarketHoursBreaker**. This aligns on-chain trading with reference FX market hours: Chainlink FX feeds typically stop updating on weekends and certain holidays, so Mento can reject FX trading even if the last reported rate is still recent enough by timestamp.

**Contract:** [mento-protocol/mento-core](https://github.com/mento-protocol/mento-core) — `contracts/oracles/BreakerBox.sol`

Integrators typically **do not** call BreakerBox directly; the [OracleAdapter](/mento-v3/build/smart-contracts/oracleadapter.md) uses it. If you need to check trading mode (e.g. for a status UI), use the adapter’s `getRate(rateFeedID)` and inspect `tradingMode`, or call `getTradingMode(rateFeedID)` on the adapter if exposed.

### MedianDeltaBreaker

**MedianDeltaBreaker** is a circuit breaker that trips when the current median oracle rate compared to an exponential moving average over previous median rates exceeds a configured relative threshold.

{% embed url="<https://github.com/mento-protocol/mento-core/blob/main/contracts/oracles/breakers/MedianDeltaBreaker.sol>" %}
MedianDeltaBreaker.sol
{% endembed %}

### ValueDeltaBreaker

**ValueDeltaBreaker** is a circuit breaker that trips when the current median oracle rate compared to a fixed reference rate exceeds a configured relative threshold.

{% embed url="<https://github.com/mento-protocol/mento-core/blob/main/contracts/oracles/breakers/ValueDeltaBreaker.sol>" %}
ValueDeltaBreaker.sol
{% endembed %}

### MarketHoursBreaker

**MarketHoursBreaker** is a special breaker for **FX market-hours gating**. Instead of comparing prices, it checks whether the current block timestamp falls inside the configured FX trading window. The current implementation treats the FX market as closed:

* from **Friday 21:00 UTC** until **Sunday 23:00 UTC**
* on **Christmas Day (Dec 25)** and **New Year's Day (Jan 1)**
* after **22:00 UTC** on **Dec 24** and **Dec 31**

When this breaker says the FX market is closed, `OracleAdapter.getFXRateIfValid()` reverts and FX-priced FPMM swaps revert too. This is especially relevant for GBP/USD, EUR/USD, and similar fiat FX feeds, whose Chainlink rates generally do not update during those closure windows.

{% embed url="<https://github.com/mento-protocol/mento-core/blob/main/contracts/oracles/breakers/MarketHoursBreaker.sol>" %}
MarketHoursBreaker.sol
{% endembed %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.mento.org/mento-v3/build/smart-contracts/breakerbox.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.