KarpelesLab / libwallet / 24829314022

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wltnet: freshness-aware RPC picker for Ethereum mainnet

Bug report: a user's wallet showed 0 ETH despite holding 0.001 ETH on
mainnet (0x144f98372516a1fd3B85E327f0A988EF12c09624). The
modchain.net RPC pinned for chainId 1 was 23 days behind chain head
(block 0x17a150f vs publicnode's 0x17c9558 — ~168k blocks) and was
returning 0x0 for any account funded after its last sync. Previous
hardcode pinned modchain unconditionally with no fallback.

Replace the unconditional pin with `pickFreshestRPC` that:

  1. Fires eth_blockNumber concurrently against modchain + every
     RPC in the chain-info registry's curated list.
  2. Determines network head from the highest responder.
  3. Returns the FIRST candidate within `maxLag` blocks of head
     (preserves caller-supplied priority order — modchain stays
     preferred when healthy, falls back to the chain-info pool
     when stale).
  4. If all candidates are >maxLag behind, returns the freshest
     of them (still serves something rather than failing).
  5. If every candidate errored, returns a plain client built
     from the first candidate so the next RPC attempt surfaces
     the upstream error instead of an opaque selection failure.

`maxLag = 100` blocks ≈ 20 minutes on Ethereum's 12s block time —
absorbs normal sync drift, trips on real staleness like the
incident this fix addresses.

Polygon (chainId 137) used to pin the same modchain endpoint, but
the modchain operator removed the polygon node, so polygon now
falls through to the standard chain-info Evaluate path
(unchanged behavior aside from the missing modchain attempt).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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