Sol, Terra or Luna?
The GPT-5.6 tier selection guide
As of 2026-10-07, the GPT-5.6 tier choice is unchanged: Terra for daily work, Luna for volume, Sol only when the task is actually hard. OpenAI list prices: Sol $4/$20 (promotional at least through 2026-11-21), Terra $2/$12, and Luna is the cheapest of the three. Note that OpenAI has since released GPT-6 Astra (2026-09-03), GPT-6 Sol and GPT-6 Luna (2026-09-22) and GPT-6.1 Sol (2026-09-29); its models page now features GPT-6 Astra, GPT-6.1 Sol and GPT-6 Luna.
Luna is now $0.20/$1.20 (was $1/$6) and Terra $2/$12 (was $2.50/$15). Sol stayed at $5/$30 as of 2026-08-02 (the 2026-09-12 archive of the official pricing page shows $4/$20, promotional at least through 2026-11-21). Codex/ChatGPT Work usage counting for Luna/Terra reflects the lower rates; plan stickers and quotas were not cut.
The three tiers, side by side
Figures from OpenAI's official release and docs (verified 2026-07-10).
| Metric | Sol | Terra | Luna |
|---|---|---|---|
| Positioning | Flagship — for the hardest problems | Balanced everyday tier — about half the price | Fastest and cheapest |
| Terminal-Bench 2.1 | 88.8% | 84.3% | 82.5% |
| Price (input / output, per 1M tokens) | $5 / $30 | $2 / $12 | $0.20 / $1.20 |
| Cached reads (−90%) | $0.50 | $0.20 | $0.02 |
| API context / max output | 1.05M / 128K | 1.05M / 128K | 1.05M / 128K |
| Speed | Up to ~750 tokens/s on Cerebras from July | Standard serving speed | Fastest of the three |
Note: Sol Ultra is Sol's high-compute mode (91.9% on Terminal-Bench 2.1), not a separate price tier.
Pick a tier by scenario
Choose Sol: the hardest engineering and reasoning work
Cross-repo refactors, long agent runs, hard debug. Sol is 88.8% on Terminal-Bench 2.1. OpenAI’s @thsottiaux, 2026-07-29 (fetched 2026-08-30): Sol was using Codex limits faster than expected; more willing to work longer, make additional tool calls, and launch subagents; High on Sol can use more tokens than High on GPT-5.5; limits were reset for all ChatGPT Work / Codex users; typical Sol use around 18% longer. Freeze the task scope before making it the default.
Choose Terra: the everyday default
Above-GPT-5.5 quality at about half of Sol's price (Terminal-Bench 84.3% vs GPT-5.5's 83.4%). For day-to-day feature work, code review and test generation, Terra is the best value default.
Choose Luna: high-volume, low-latency, batch
Completions, commit messages, bulk jobs, light CI. After 07-30 the API list is $0.20/$1.20. OpenAI Codex pricing page (fetched 2026-08-30) prices Codex at 5 credits per 1M input for Luna vs 100 for Sol. The same @thsottiaux post of 2026-07-29 (fetched 2026-08-30) says OpenAI has not reduced usage on any subscription plans and that typical Sol use should last around 18% longer. Luna is not free — it is the low-credit tier.
Cost examples
A typical agentic coding session (800K input + 60K output tokens): about $2.32 on Terra, about $5.80 on Sol, and about $0.23 on Luna at short-context list rates as of 2026-08-02 (illustrative).
Switch per request — no commitment
The tiers are three model ids: gpt-5.6-sol, gpt-5.6-terra and gpt-5.6-luna. Switch any time with /model in Codex CLI, or per request in the API. On QCode, as of 2026-10-07, gpt-5.6-sol and gpt-5.6-terra share one key and are billed by token (per-model rates on /models); QCode does not currently support gpt-6-luna or gpt-5.6-luna (both removed from /models), so please use another GPT model — for volume work, gpt-5.6-terra.
Tier selection FAQ
Not sure which tier? What should the default be?
Make Terra your default: better than GPT-5.5 at half of Sol's price. Escalate to Sol when Terra gets stuck, and drop to Luna for high-frequency light tasks. This Terra-first strategy is the cost optimum for most teams.
Do the tiers share the same context window and output limit?
Yes. OpenAI's docs confirm all three share the 1.05M-token API context window, 128K max output, the same February 16, 2026 knowledge cutoff and the same reasoning-effort options (none through max). Clients may hand out a lower session cap than that spec; the widely quoted 400K is third-party arithmetic (a 272K input budget plus 128K output), not a figure in OpenAI's model page.
What is Sol Ultra? Is it billed separately?
Sol Ultra is Sol's high-compute mode (91.9% on Terminal-Bench 2.1), not a separate price tier. It burns more reasoning tokens, so a task costs more at the same rates. When you see 91.9% quoted, note that it is the Ultra-mode score.
How are the tiers billed on QCode?
As of 2026-10-07, gpt-5.6-sol and gpt-5.6-terra share one QCode key and are billed by token; per-model rates are on /models. QCode does not currently support gpt-6-luna or gpt-5.6-luna (both removed from /models); please use another GPT model, such as gpt-6.1-sol, gpt-6-sol or gpt-5.6-terra. Switching tiers needs no account changes — just use a different model id.
GPT-5.6 Sol and Terra are callable on QCode
gpt-5.6-sol / terra share one key with the Claude lineup (QCode does not currently support Luna). Plans from $8.57/mo; the key goes live the moment payment clears.