GPT-5.3 Codex vs GPT-5.4

Not a same-generation comparison — GPT-5.3 Codex is the agentic-coding-specialized model, GPT-5.4 the general frontier model from the generation right after it — and the gap between them looks a lot like the site's headline Sol-versus-Codex comparison in miniature.

The shape of the tradeoff

GPT-5.4 carries a meaningfully larger context window and a more recent knowledge cutoff. GPT-5.3 Codex costs substantially less per token on both input and output, and it's the only model on this entire roster with published reasoning-effort control. Both sit in the same rate-limit group, so — as with the Sol comparison — throughput isn't part of this tradeoff at all.

What's explicitly unpublished

GPT-5.4 states the long-context repricing rule outright. GPT-5.3 Codex's own page doesn't state it either way, recorded honestly as not published rather than assumed absent or assumed inherited. Neither Batch nor Flex pricing is published for GPT-5.3 Codex, while GPT-5.4 publishes both — a real asymmetry in which delivery options each model actually offers, not just a pricing difference.

How to actually decide

If your task needs GPT-5.4's larger window or its newer knowledge specifically, that's the deciding factor regardless of price. If cost matters more and your work fits inside GPT-5.3 Codex's window, its lower price and its reasoning-effort control are both real, concrete reasons to prefer it — not just "the cheaper option," a genuinely different set of controls.