forkchoice: seed anchor checkpoints from the anchor slot#677
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tcoratger merged 1 commit intoleanEthereum:mainfrom Apr 23, 2026
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Store.from_anchor previously built the store's justified/finalized checkpoints by copying the slot from the anchor state's embedded latest_justified/latest_finalized (which can be strictly less than the anchor slot) while overriding only the root to the anchor block root. That produced a slot/root-inconsistent checkpoint: the slot pointed at pre-anchor history while the root identified the anchor block itself. Seed both checkpoints from the anchor itself: slot = anchor.slot, root = anchor_root. The anchor state's embedded checkpoints are intentionally ignored, matching the "store treats the anchor as the new genesis" framing already used at the checkpoint-sync entry point. Genesis initialization is unaffected: at genesis the anchor state's embedded checkpoints already sit at slot 0 = anchor.slot, so the new seeding produces identical values. Also updates the checkpoint-sync tests and a misleading inline comment that described the previous (pre-anchor-slot) behavior.
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tcoratger
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Ports leanEthereum/leanSpec#677 into nlean's checkpoint-sync anchor creation. CreateCheckpointHeadState used to build the justified and finalized checkpoints by copying the slot from the anchor state's embedded latest_justified / latest_finalized while overriding only the root to the anchor block root. The two fields went out of sync: the slot still pointed at pre-anchor history while the root identified the anchor block itself. Externally the inconsistency surfaced on leanpoint as "finalized slot > justified slot" once the checkpoint-synced node advanced past its anchor — leanpoint reads the state.slot field from /states/finalized and compared it with the justified checkpoint JSON. Seed both checkpoints from the anchor block directly, matching the beacon chain fork-choice spec the leanSpec PR references.
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🗒️ Description
Store.from_anchorpreviously built the store's justified/finalized checkpoints by copying the slot from the anchor state's embeddedlatest_justified/latest_finalized(which can be strictly less than the anchor slot) while overriding only the root to the anchor block root. That produced a slot/root-inconsistent checkpoint: the slot pointed at pre-anchor history while the root identified the anchor block itself.This PR changes
Store.from_anchorto use the anchor block as the justified/finalized checkpoints of theStore, following the beacon chain specs.Also updates the checkpoint-sync tests and a misleading inline comment that described the previous (pre-anchor-slot) behavior.
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✅ Checklist
toxchecks to avoid unnecessary CI fails:uvx tox