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.”