Codex has been post-trained for coding, including agentic coding tasks.

It's certainly not impossible that the better long-horizon agentic performance in Codex overcomes any deficiencies in outright banking knowledge that Codex 5.2 has vs plain 5.2.

It could be problem specific. There are certain non program things that opus seems better than sonnet at as well

Swapped sonnet and opus on my last reply, oops