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I Ran Codex and Claude Side by Side
The setup takes 5 minutes. The compliance question takes longer.
Last week I installed OpenAI’s Codex plugin inside Claude Code. Four commands, five minutes, and suddenly I had two competing AI systems running in the same terminal session — one drafting, one critiquing.
It felt like a parlor trick. Then I read what Microsoft shipped the same day.
Copilot Cowork, now live for enterprise Microsoft 365 customers, does the same thing at a completely different scale. GPT drafts a research report. Claude audits it. A third model synthesizes both.
It reports a 13.8% benchmark improvement over its nearest competitor — measured by the competitor’s own test, graded by the vendor’s own model. And for those of us working inside regulated institutions, it contains a compliance gap that nobody in tech press has written about yet.
This article covers both levels:
- First, the practical: how to pair Claude Code and Codex in your own workflow today, with a before/after example that shows exactly where second opinions matter.
- Then the architectural: what Microsoft actually built, why the benchmark story is more complicated than it looks, and the specific…
