Validator Set Dynamic Reorganization During Epoch Boundary Produces Inconsistent Committee Roots

[JamesEjembi]

Problem Statement / Feature Objective

When the validator set is dynamically reorganized mid-epoch (triggered by an irregular exit or a late-inclusion activation), the committee root computed from get_beacon_committee() diverges between the pre-reorg and post-reorg view. This causes attestation verification to fail spuriously for validators assigned to different shard committees before and after the boundary.

Technical Invariants & Bounds

• Epoch length: 32 slots (SHARD_COMMITTEE_PERIOD = 256 epochs).
• Validator set size: bounded by 2^19 (~524k) entries.
• Committee root is SHA-256 over the sorted list of validator indices.
• Reorg window: slots where state.slot % SLOTS_PER_EPOCH < 4.
• Cross-reorg attestations must be verifiable under both pre and post committee root.

Codebase Navigation Guide

• src/validator/committee-assignment.rs - get_beacon_committee() and committee root derivation.
• src/validator/validator-set.rs - reorg_validator_set() entry point for dynamic changes.
• src/attestation/verifier.rs - attestation verification that consumes committee root.
• src/state/epoch-transition.rs - epoch boundary state recalculation.
• src/db/committee-cache.rs - cached committee root store.

Implementation Blueprint

1. In src/validator/validator-set.rs, introduce a PendingReorg struct that records the slot range during which a reorg is active.
2. Modify get_beacon_committee() to check the PendingReorg - if the current slot falls in the reorg window, compute the committee root from both the old and new set and return a CommitteeView::Ambiguous(old_root, new_root).
3. In src/attestation/verifier.rs, accept an Ambiguous committee view and verify the attestation against either root; if one matches, accept.
4. After the reorg window closes (slot >= reorg_end), finalize to the new committee root and evict the old cache entry.
5. Write integration tests that simulate a mid-epoch exit and verify cross-boundary attestations still pass.

[pauljuliet9900-netizen]

Hello maintainer i would like to work on this issue

[grantfox-oss]

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[grantfox-oss]

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@pauljuliet9900-netizen's PR #47 was approved and merged by @JamesEjembi.

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👏 Great work, @pauljuliet9900-netizen! Keep contributing to VeriNode-Labs.