Start with the operating model
A useful comparison begins before either agent writes code. Decide where the work should run, what repository context it may inspect, which commands require permission, and who owns the final release decision. Codex spans app, editor, and terminal surfaces; Claude Code emphasizes project work through terminal and desktop workflows. Those are verified product differences, not outcome evidence.
The right first candidate therefore depends on how the builder already works. A repository operated from an editor may value a different review loop from a terminal-first project. Neither interface proves that the resulting code is more correct, maintainable, secure, or economical.
Decision questions before testing
Context
Can the agent discover project rules, existing tests, and relevant files without broad unrelated edits?
Control
Are command permissions, network access, sensitive files, and destructive operations visible and bounded?
Review
Does the workflow produce a compact diff, clear assumptions, and fresh verification output a human can audit?
Recovery
Can the builder identify and reverse a wrong turn without losing unrelated work or restarting the entire task?
The benchmark ShipStackLab will run
- Start both agents from the same clean repository commit and dependency state.
- Provide the same feature brief, constraints, project instructions, and acceptance checks.
- Record prompts, permissions, commands, failed attempts, corrections, elapsed work, and attributable cost.
- Run the same test, lint, build, diff, accessibility, and production-smoke gates.
- Publish the artifacts and limitations before making any fit recommendation.
Until that controlled run exists, this page is a decision framework and test plan. Vendor descriptions establish capabilities; they do not establish which agent ships the better result.