🤖 [claude] Derive Firehose finality from the block's Parlia attestation (fixes wrong LIB on fork blocks)

[Johnaverse]

Summary

Root-cause fix for the finality signal reported by Phantom (bsc mainnet block 120653740, 2026-09-08 08:24 UTC) and for two related production symptoms.

Defect. reth-firehose stamped every traced block with the node's canonical finalized head at execution time (canonical_in_memory_state().get_finalized_num_hash() in the engine payload validator; provider().finalized_block_num_hash() in the ExEx runner). That is node state — it depends on which Parlia votes this node had received — and it is not necessarily an ancestor of a side-chain block being traced. On BSC fast finality (head−1…3) this produced:

• Fork block marked final downstream: fork block 120653743 (e3d67571) was emitted with LIB 120653740; on its own ancestry that height is 2c97928d, which Phantom's forkdb then finalized and locked onto the dead branch.
• Readers disagree on LIB for identical blocks (129 of 263 recent pairs differ between x91 and x827), so the merger sees two canonical names for one block and files one as "forked" — ~50k such files in bsc-sf-v5-forked-blocks.
• LIB stepping backwards within one reader (e.g. x91: 120772186→LIB …184, 120772187→LIB …183), the same behaviour the geth-era tracer clamped.

Fix.

• pinax-network/bnb-reth firehose/develop @ 73cdbc6 (tag bnb-bf76323c-fh3.1-2): new ChainTracingConfig::finalized_for_block resolver; mapper::finalized_ref_for_block() uses it exclusively when set (a None result emits no finalized ref — fireeth falls back to block − 200 — never node state); both engine call sites and the ExEx runner switched. Chains without the hook and the staged-sync path are unchanged.
• This repo: firehose_finalized_for_block() in main.rs reads the Parlia snapshot of the emitted block and returns its attestation's finalized checkpoint (Snapshot::get_finalized_number() = vote_data.source, the same rule parlia_getFinalizedNumber exposes) with the matching hash. Deterministic per block, identical on every node, on the block's own ancestry by construction.
• Pins → bnb-bf76323c-fh3.1-2; Cargo.lock same crate set, new commit. CHANGELOG for dev-049d306-fh3.1-2.

Compiled only by CI (no local toolchain) — expect this PR's checks to be the first build.

Test plan

• CI green (incl. Docker build) — compiles both layers
• Tag dev-049d306-fh3.1-2, bump eosn-sf-bsc4-test, deploy on bsc-sfdm40 (test mode)
• Once live: x40 one-block names carry LIB = attestation source (head−2 steady state); no LIB regressions; test-mode diff shows only the known size deltas
• File upstream to StreamingFast with the evidence

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🤖 Created by Claude Code Fable 5.1 (effort: high)

🤖 Generated with Claude Code

https://claude.ai/code/session_01YHvxpuVpZfzefJgwgqjAzn