Reference

API surface of GasKillerSDK (BLS scheme). Inheriting it gives your contract everything on this page.

abstract contract GasKillerSDK is StateTracker, TransitionGuard, IGasKillerSDK

Constants

Constant	Value	Meaning
`QUORUM_THRESHOLD`	`66`	Minimum share of each quorum's stake that must sign
`THRESHOLD_DENOMINATOR`	`100`	Denominator for the above — so 66%
—	`300`	Default `blockStaleMeasure`, in blocks, when unset
ERC-165 id	`0x93de4531`	`type(IGasKillerSDK).interfaceId`; the router requires it

The threshold is checked per quorum, not across their union: every quorum in quorumNumbers must independently clear 66%.

`verifyAndUpdate`

The settlement entrypoint. The router builds this call for you (you never encode it by hand), but its parameters explain every failure mode.

function verifyAndUpdate(
    bytes32 msgHash,
    bytes calldata quorumNumbers,
    uint32 referenceBlockNumber,
    bytes calldata storageUpdates,
    uint256 transitionIndex,
    bytes4 targetFunction,
    IBLSSignatureCheckerTypes.NonSignerStakesAndSignature calldata nonSignerStakesAndSignature
) external payable guardTransition trackState;

Parameter	Purpose
`msgHash`	The signed digest; recomputed on-chain and compared
`quorumNumbers`	Which quorums must clear the threshold
`referenceBlockNumber`	Block the operator set was snapshotted at
`storageUpdates`	ABI-encoded `(StateUpdateType[], bytes[])` — the diff to apply
`transitionIndex`	Counter value this payload was computed against
`targetFunction`	Selector of the tracked function that was simulated
`nonSignerStakesAndSignature`	Aggregate signature plus per-non-signer stake proofs

It executes in this order, so an earlier check masks any later one:

referenceBlockNumber < block.number → else FutureBlockNumber
referenceBlockNumber + blockStaleMeasure >= block.number → else StaleBlockNumber
transitionIndex + 1 == stateTransitionCount() → else InvalidTransitionIndex
Digest matches msgHash → else InvalidSignature
checkSignatures on the configured checker, then the 66% test per quorum
Apply the updates

The signed digest

sha256(abi.encode(transitionIndex, address(this), targetFunction, storageUpdates))

Available as a view for off-chain cross-checking:

function getMessageHash(
    uint256 transitionIndex,
    bytes4 targetFunction,
    bytes calldata storageUpdates
) external view returns (bytes32);

Binding address(this) means a payload cannot be replayed against a different contract, and binding transitionIndex means it cannot be replayed against a different state of the same one.

State update types

storageUpdates decodes to a list of operations applied in order.

Type	Effect
`STORE`	Write a 32-byte value to a storage slot
`CALL`	External call, optionally with ETH value
`LOG0`–`LOG4`	Emit a log with 0–4 indexed topics
`CREATE`	Deploy a contract, nonce-derived address
`CREATE2`	Deploy a contract, salt-derived address

Most integrations only ever produce STORE and LOG*. See Tracked functions for the funding rules that apply to the value-bearing types.

Inherited members

From StateTracker:

Member	Description
`trackState`	Modifier; increments the transition counter before the body
`stateTransitionCount()`	Transitions applied so far

From TransitionGuard:

Member	Description
`guardTransition`	Modifier; reverts re-entry, holds the in-transition latch
`inTransition()`	True while a transition is applying

Both use fixed hashed slots, and TransitionGuard uses EIP-1153 transient storage, so a Cancun-or-later EVM is required.

Revert selectors

What a failed settlement means. Reverts from the SDK:

Selector	Error	Cause	Fix
`0x252f8a0e`	`FutureBlockNumber`	Reference block is not yet mined	Retry; usually a node lagging behind head
`0x305c3e93`	`StaleBlockNumber`	Payload older than `blockStaleMeasure`	Submit a new task — the payload expired
`0x7376e0a2`	`InvalidTransitionIndex`	Contract state advanced since signing	Submit a new task; another transition landed first
`0x8baa579f`	`InvalidSignature`	Recomputed digest ≠ `msgHash`	Payload was altered, or the target's ABI differs from the router's
`0x6d8605db`	`InsufficientQuorumThreshold`	Signers hold under 66% of a quorum	Transient: too many operators missed the round
`0xfbbb7b2b`	`InvalidStorageUpdates`	Updates could not be decoded	Report it — malformed payload
`0x398d4d32`	`InvalidOperation`	Unrecognised update type	Report it — version mismatch
`0x287cdced`	`ReentrantTransition`	`verifyAndUpdate` re-entered mid-transition	A `CALL` update re-entered the contract; see `inTransition()`
`0x493f09c4`	`RevertingContext`	A `CALL` update reverted	Often under-funded `msg.value`; carries the inner revert data
`0x30116425`	`DeploymentFailed`	A `CREATE`/`CREATE2` update failed	Usually under-funded `msg.value`
`0x5f6f132c`	`InvalidArguments`	Update arguments malformed	Report it
`0x25773e13`	`MalformedLogPayload`	Log update malformed	Report it

Reverts that come from the restaking middleware's signature checker, not the SDK:

Selector	Error	What it usually means
`0xe1310aed`	`InvalidQuorumApkHash`	Your `blsSignatureChecker` is bound to a different operator set than the router signs with. See Configuration
`0x4b874f45`	`InvalidReferenceBlocknumber`	Reference block outside the checker's usable range
`0xaffc5edb`	`StaleStakesForbidden`	Stake snapshot too old for the checker's policy
`0x43714afd`	`InputArrayLengthMismatch`	Malformed non-signer arrays — report it

Decode an unknown selector with cast 4byte <selector>, or recover a revert locally by replaying the payload at a block inside its validity window:

cast call "$TO" "$DATA" --from "$FROM" --block <n> --rpc-url "$RPC_URL"

A payload that reverts at every block in its window is not a timing problem: it is a configuration problem.

Source

gas-killer/solidity-sdk — the SDK
gas-killer/example-contracts — worked examples of progressively richer targets