fix: skip finalization advance for stale finalized sources#802
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latifkasuli wants to merge 3 commits into
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fix: skip finalization advance for stale finalized sources#802latifkasuli wants to merge 3 commits into
latifkasuli wants to merge 3 commits into
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@latifkasuli Please let me know when ready for review |
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Ready for review now. I re-ran the focused validation:
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Rebase the stale-source finalization fix onto current main: the spec file moved under the spec/ package and attestation specs renamed validator_ids to validator_indices. Also fix the new test expectation. Building justified_slots via model_copy(update=...) bypassed Pydantic validation, leaving data as a list instead of a tuple, so the post-state comparison failed even with the fix applied. Use the canonical constructor instead. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Add the boundary case raised in review: a source whose slot equals the finalized slot. Such a source is already final, so it may justify a newer target but must never re-finalize. This locks the > (not >=) intent of the finalization-advance guard. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
tcoratger
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May 30, 2026
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Summary
This fixes an Lstar finalization edge case where an attestation with a source checkpoint at or behind the current finalized boundary could justify a newer target, then incorrectly enter the finalization-advance scan from below the finalized boundary.
Finalized sources are valid justification anchors:
JustifiedSlots.is_slot_justified()treats slots at or belowlatest_finalized.slotas already justified. But once such an attestation crossed the supermajority threshold, the finalization logic scannedsource.slot + 1 .. target.slotand calledSlot.is_justifiable_after(finalized_slot)on candidate slots beforefinalized_slot, triggeringCandidate slot must not be before finalized slot.The fix gates finalization advancement on
source.slot > finalized_slot. Stale finalized sources may still justify newer targets, but they no longer try to rewind or scan below the finalized boundary.Validation
uv run --group test fill tests/consensus/lstar/state_transition/test_finalization.py --fork=Lstar --clean -quv run --group lint ruff check src/lean_spec/forks/lstar/spec.py tests/consensus/lstar/state_transition/test_finalization.pyuv run --group lint ruff format --check src/lean_spec/forks/lstar/spec.py tests/consensus/lstar/state_transition/test_finalization.py