Gas Optimization Review

Skill: gas-optimization-review

Purpose

Identify safe and justified gas optimizations in Solidity code while preserving:

• correctness
• accounting integrity
• readability
• auditability

This skill proposes optimizations. It does not apply them unless explicitly requested.

When to Invoke

• After correctness is established
• After tests and invariants are in place
• During performance tuning or cost-reduction phases
• Before deployment or audit finalization

Gas optimization must never precede correctness.

Inputs Required

• Target Solidity contracts
• Critical execution paths (hot paths)
• Context on expected usage patterns (optional)

Actions

1) Identify gas hotspots

Analyze:

• frequently called functions
• loops and repeated storage access
• redundant computations
• unnecessary external calls
• storage reads and writes

Focus on measurable impact, not theoretical savings.

2) Propose optimizations

For each proposed optimization:

• describe the change clearly
• explain the gas-saving mechanism
• estimate relative impact (low/medium/high)
• specify whether it is:
  • purely mechanical
  • logic-adjacent
  • logic-sensitive

3) Flag risk and correctness sensitivity

Explicitly flag optimizations that:

• rely on assumptions about token behavior
• change evaluation order
• alter arithmetic or rounding behavior
• depend on compiler or EVM subtleties
• reduce readability or debuggability

Risky optimizations must be clearly labeled and justified.

Constraints and Safety Rules

• Must not change observable behavior
• Must not change arithmetic semantics or rounding
• Must not weaken safety checks or invariants
• Must not obscure logic for marginal gas gains
• Must not introduce assembly unless explicitly justified
• Must comply with all rules in .codex/constraints/solidity-style.md

If an optimization risks correctness, it must be presented as optional and high-risk.

Outputs

• A structured list of gas optimization suggestions, each including:
  • description
  • affected code paths
  • expected gas impact (qualitative)
  • risk level (low/medium/high)
  • rationale and trade-offs

The output must be suitable for review by:

• protocol engineers
• auditors
• reviewers evaluating cost vs risk

Verification

• Suggested optimizations preserve behavior under existing tests
• Risky suggestions are explicitly marked
• No recommendation contradicts documented assumptions or invariants

Handoff

After review, optimizations may be applied via:

• safe-refactor for non-upgradeable contracts

Any applied optimization must be followed by:

• unchanged test suite passing
• explicit confirmation of no behavior change

Example Prompts

• “Use gas-optimization-review on Vault.sol and clearly flag any logic-sensitive suggestions.”
• “Identify low-risk gas optimizations for the deposit path without reducing readability.”

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