[DEFERRED] Advanced SSE replay, reorg, and competing-root reconciliation

[krisoshea-eth]

Status

Tracking shell only. This is not current core work and must not be started without explicit maintainer promotion and bounded rescoping.

Why it remains useful

Long disconnects, deeper reorgs, and competing roots require more reconciliation than the bounded same-source-BN restart path. The Beacon API event contract defines no SSE id or Last-Event-ID resumption, so conforming clients cannot be assumed to identify or replay events missed during a disconnect.

Activation trigger

• The basic block-event path and REL-01 are stable.
• Specific replay or reorg failures are reproduced.
• Required retention and deduplication windows are measured.
• Bounded REL-01 reconciliation is proven insufficient and an alternate history source/window is specified.
• A scoped Conditional package with owner, reviewer, evidence, and stop rule is approved.

Boundary

Core supports bounded event-before-block retry, deduplication, head-change resubmission, and explicit same-source-BN restart reconciliation only. It does not claim exact EventSource replay, long-gap history recovery, or competing-root reconciliation.

[linear-code]

LOD-41