22_state_overlay_consistency_skill

Overview

This skill detects and prevents state-visibility violations that occur when execution frames within a single transaction do not inherit their parent overlays. It ensures deployed code, storage writes, warm slot sets, and gas accounting remain consistent and observable across CREATE/CREATE2 and subsequent CALL/DELEGATECALL/STATICCALL frames. Use it to catch silent gas under-charging and consensus-risking execution paths before they reach production.

How this skill works

The checker inspects transaction-scoped execution frames and validates a set of core invariants: code visibility, overlay inheritance, gas propagation sanity, and write-then-read consistency. It walks the frame hierarchy, compares code hashes, storage roots, warm slot sets, and gas accounting between parent and child frames, and flags any divergence as a failure. Heuristic gas checks detect cases where a call appears to have been charged base gas only despite a non-empty target.

When to use it

• Pre-deployment testing of contracts that create other contracts and immediately call them (CREATE/CREATE2 → CALL).
• Automated transaction inspection in CI to detect invisible code or storage after writes.
• Runtime monitoring during fuzzing or adversarial scenario generation that involves nested frames.
• Safety gating before accepting blocks or transactions in environments where consensus divergence is critical.
• Postmortem analysis when unexpected balance or gas anomalies appear.

Best practices

• Run checks on every single-transaction trace that includes CREATE, CREATE2, SSTORE, or TSTORE operations.
• Fail fast: immediately flag and block transactions where a read does not observe a prior write within the same transaction.
• Include warm slot, code hash, and storage root comparisons to avoid false negatives from partial checks.
• Correlate gas-accounting anomalies with code visibility checks to raise high-confidence alerts.
• Integrate with pre-action guards to stop effects that could lead to consensus divergence.

Example use cases

• Detect a CREATE2 followed by CALL where the callee executes as if empty because deployed code was not visible.
• Find SSTORE then SLOAD within a transaction where the load returns the pre-transaction value.
• Flag a child frame that forked from the base snapshot instead of inheriting the parent overlay.
• Alert when CALL gas charged equals base cost but target address actually has non-empty code.
• Block transactions during automated testing that would produce inconsistent final balances.