Claude Code vs OpenAI Codex

4 posts from X ran Claude Code and OpenAI Codex on the same task. 1 keep the model fixed; in the rest each side used its own model. Models: Gemini 4 Argon, Claude Opus 5.5, GPT-6 Astra, GPT-5.6 Sol, Claude Opus 5, Claude Opus 4.1, GPT-5. All harness comparisons.