GPT-5.6 Luna vs GPT-5.4 Nano

The two cheapest models on this site, from consecutive generations — and the newer one wins on more than just being newer.

Window and recency both favour Luna

Luna's context window is substantially larger than Nano's, and its knowledge cutoff is considerably more recent. For a workload that was sized against Nano's smaller window out of necessity, Luna removes that constraint at a price that, while higher than Nano's rock-bottom rate, still undercuts most of the rest of the roster.

The rate-limit picture is closer than the price gap suggests

Both sit in rate-limit groups with a genuinely generous top-tier ceiling relative to their price — this is one of the few pairings on this roster where neither model is the throughput-constrained option. Luna's group is the more generous of the two at the highest tiers, but Nano's own ceiling is still real headroom for its price point, not a token-cost model punished with a matching throughput penalty.

Fast mode splits them again

Luna offers Fast mode. Nano doesn't offer it at all — the same split that shows up between Nano and its own generation's Mini tier.

How to actually decide

For anything genuinely price-sensitive where Nano's smaller window is enough, Nano's rock-bottom rate is hard to beat on cost alone. For nearly everything else at this end of the roster — larger context, more recent knowledge, an actual Fast-mode option — Luna is worth the modest price step up.