feat: implement forkchoice is_head_weak()#9654
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This pull request refactors the fork choice implementation to support the Gloas fork's modified is_head_weak specification. It splits the tracking of node weights into two separate components: attestationScore (representing attester votes only) and weight (which includes proposer boost). The isHeadWeak logic is extracted into a private helper method in ForkChoice that handles both pre-Gloas and post-Gloas specifications, including adding back the weight of equivocating validators for post-Gloas blocks. Additionally, deltas has been renamed to attestationDeltas across the codebase for clarity, and comprehensive unit tests have been added to verify the new behavior. I have no feedback to provide.
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Performance Report✔️ no performance regression detected Full benchmark results
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## unstable #9654 +/- ##
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- Coverage 52.49% 52.48% -0.02%
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Files 848 848
Lines 60485 60458 -27
Branches 4466 4459 -7
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- Hits 31754 31732 -22
+ Misses 28670 28665 -5
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ensi321
reviewed
Jul 16, 2026
| // The default variant is PENDING for gloas, FULL pre-gloas. PENDING is the variant gloas measures | ||
| // support on, ie. support for the beacon block root regardless of its payload status. | ||
| // Only ever called on a block already in fork choice, so a miss is a broken invariant. | ||
| const node = this.protoArray.getNodeDefaultStatus(blockRoot); |
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So we already have an established pattern of getDefaultNodeIndex + getNodeByIndex in the code ie.
lodestar/packages/fork-choice/src/protoArray/protoArray.ts
Lines 695 to 699 in ea1ba2d
lodestar/packages/fork-choice/src/protoArray/protoArray.ts
Lines 880 to 885 in ea1ba2d
and
lodestar/packages/fork-choice/src/protoArray/protoArray.ts
Lines 1175 to 1189 in ea1ba2d
So we either keep that pattern, or refactor so these 3 places also use this.protoArray.getNodeDefaultStatus
| const parentStrongVariant = isGloasBlock(parentBlock) ? PayloadStatus.PENDING : PayloadStatus.FULL; | ||
| const parentNode = this.protoArray.getNode(parentBlock.blockRoot, parentStrongVariant); | ||
| // If parentNode is unavailable, give up reorg | ||
| if (parentNode === undefined || parentNode.weight <= parentThreshold) { |
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Make sure is_parent_strong is using parentNode.attestationScore post-gloas, and keep parentNode.weight pre-gloas.
Because gloas's spec uses get_attestation_score
| for (let index = 0; index < state.getBeaconCommitteeCountPerSlot(epoch); index++) { | ||
| for (const validatorIndex of state.getBeaconCommittee(node.slot, index)) { | ||
| if (equivocatingIndices.has(validatorIndex)) { | ||
| headWeight += this.fcStore.justified.balances[validatorIndex] ?? 0; |
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We can't store's justified balances here because it's 0 for equivocating validators.
Because we zero them here
lodestar/packages/state-transition/src/util/balance.ts
Lines 72 to 75 in ea1ba2d
that ultimately get propagated to store's justified balances.
We need the justified state's effectiveBalanceIncrements to get the non-zero'ed balance of equivocators.
ensi321
reviewed
Jul 16, 2026
| node.weight += nodeDelta; | ||
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| // Update the parent delta (if any) | ||
| const isInvalid = node.executionStatus === ExecutionStatus.Invalid; |
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We probably need a unit test to test the code branch of node.executionStatus === ExecutionStatus.Invalid
| // Only ever called on a block already in fork choice, so a miss is a broken invariant. | ||
| const node = this.protoArray.getNodeDefaultStatus(blockRoot); | ||
| if (node === undefined) { | ||
| throw new ForkChoiceError({code: ForkChoiceErrorCode.MISSING_PROTO_ARRAY_BLOCK, root: blockRoot}); |
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Note that if we throw error from this function, the error is uncaught all the way up to produceBlockV4 and produceEngineOrBuilderBlock leading to the entire block not being produced. I think if there is error, we should not re-org. We probably need to add a NotReorgedReason.ErrorEncountered or something similar if this happens.
Same with BEACON_STATE_ERROR below
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