# Rex3

This page is an informative summary of the Rex3 specification. For the full normative definition, see the Rex3 spec in the mega-evm repository.

## Summary

Rex3 addresses two issues with [oracle](https://docs.megaeth.com/spec/system-contracts/oracle) [gas detention](https://docs.megaeth.com/spec/megaevm/gas-detention) and fixes a gap in [keyless deploy](https://docs.megaeth.com/spec/system-contracts/keyless-deploy) resource accounting.

The oracle access [compute gas](https://docs.megaeth.com/spec/reference/glossary#compute-gas) cap is increased from 1M to **20M**, matching the block environment cap. The 1M cap was too restrictive for legitimate use cases, causing frequent `VolatileDataAccessOutOfGas` halts in contracts that need meaningful computation after reading oracle data.

Oracle detention is also changed from CALL-based to **SLOAD-based** triggering — simply calling the oracle contract without reading its storage no longer activates gas detention. Finally, the keyless deploy sandbox overhead (100K gas) is now properly tracked as compute gas.

## What Changed

### Oracle Access Compute Gas Limit Increase

#### Previous behavior

* Oracle access (triggered by CALL or STATICCALL to the oracle address) caps compute gas at 1,000,000 (1M).

#### New behavior

* Oracle storage reads (SLOAD from the oracle contract) cap compute gas at 20,000,000 (20M).
* The block environment access cap remains at 20M (unchanged).
* When both block environment and oracle storage are accessed, neither is more restrictive than the other.

### Oracle Gas Detention Triggers on SLOAD

#### Previous behavior

* CALL or STATICCALL to the oracle contract address triggers gas detention.
* Any CALL or STATICCALL to the oracle triggers detention even without reading storage.

#### New behavior

* SLOAD from the oracle contract's storage triggers gas detention.
* CALL to the oracle contract address alone does not trigger gas detention — only an SLOAD from the oracle's storage triggers it.
* The SLOAD-based trigger is caller-agnostic: any SLOAD reading the oracle contract's storage triggers detention regardless of call depth.
* DELEGATECALL to the oracle does not trigger detention — SLOAD in a DELEGATECALL context reads the caller's storage, not the oracle's.
* Transactions from `MEGA_SYSTEM_ADDRESS` are exempted from oracle gas detention (unchanged, but the exemption now checks the transaction sender rather than the call-frame-level caller).

### Keyless Deploy Compute Gas Tracking

#### Previous behavior

* The 100K overhead gas for keyless deploy sandbox execution is deducted from call frame gas but not recorded as compute gas.
* Keyless deploy transactions do not count the overhead toward the per-transaction compute gas limit.

#### New behavior

* The 100K keyless deploy overhead is recorded as compute gas.
* If recording the overhead causes the compute gas limit to be exceeded, execution halts.

## Developer Impact

**Contracts that read oracle data can now perform more computation.** The oracle access cap increased from 1M to 20M, providing 20× more post-access compute budget. Contracts that previously hit `VolatileDataAccessOutOfGas` after oracle reads should no longer encounter this issue.

**Simply calling the oracle no longer triggers detention.** Only actual SLOAD reads from oracle storage activate the cap. Contracts that call the oracle contract for hint operations or other non-storage-reading functionality are no longer penalized.

**The gas detention cap is still absolute in Rex3.** Transactions that have consumed more than 20M compute gas before an oracle SLOAD will halt immediately. Rex4 changes this to a relative cap — see the [Rex4 upgrade page](https://docs.megaeth.com/spec/network-upgrades/rex4).

## Safety and Compatibility

All pre-Rex3 behavior is unchanged.

The shift from CALL-based to SLOAD-based oracle detection more accurately captures actual oracle data access. DELEGATECALL to the oracle is excluded because SLOAD in a DELEGATECALL context reads the caller's storage, not the oracle's — this is consistent with Rex2 behavior.

The [`MEGA_SYSTEM_ADDRESS`](https://docs.megaeth.com/spec/system-contracts/system-tx) exemption now checks `TxEnv.caller` (the transaction sender) rather than the call-frame-level caller, meaning the entire transaction from the system address is exempted regardless of call depth.

## References

* [mega-evm repository](https://github.com/megaeth-labs/mega-evm)
* [Gas Detention](https://docs.megaeth.com/spec/megaevm/gas-detention) — background on the gas detention mechanism
* [Oracle Service](https://docs.megaeth.com/spec/system-contracts/oracle) — oracle contract documentation