GPT-5.6 Sol vs GPT-5.6 Terra

Same family, same window, same rate-limit group — the entire comparison between these two comes down to price, which makes this one of the cleaner decisions on this site's whole roster rather than a genuine multi-axis tradeoff.

What's identical

Context window, maximum output length, knowledge cutoff and rate-limit tier all match exactly between these two. Neither offers more headroom or more recent training data than the other — picking one over the other changes nothing on those axes at all.

What actually differs

Terra costs meaningfully less than Sol across every service tier, on both input and output, in both the short- and long-context bands. That's the entire decision: identical capability specs, different price.

How to actually decide

If nothing about your workload specifically needs Sol — and given the identical specs, it's worth asking honestly whether it does — Terra is the straightforward default, since there's no capability being traded away for the lower price here the way there usually is elsewhere on this roster. The one legitimate reason to stay on Sol despite the price gap is exactly that it's what the CLI ships with by default: a workflow that hasn't deliberately chosen Terra is very likely running Sol as an accident of the default, not a decision, and switching costs nothing but a config change worth making deliberately rather than leaving to inertia.