GPT-5.6 Terra vs GPT-5.6 Luna
OpenAI's GPT-5.6 Terra and OpenAI's GPT-5.6 Luna both target production language workloads, but they price and behave differently. Here is the side-by-side.
Pricing checked against provider documentation on . How we verify
The short answer
GPT-5.6 Luna is the cheaper option — roughly 10.0x less on a blended workload, and it suits high-volume work on a tight budget. GPT-5.6 Terra justifies its premium when you need balanced production workloads.
OpenAI • GPT-5.6
$2.00 / $12.00
/ 1M tokens (input / output)
The everyday tier of the GPT-5.6 family, roughly corresponding to the old 'mini' slot but benchmarking above the previous generation's flagship. For most application backends this is the default worth trying before reaching for Sol, since it clears Claude Fable 5 on several evals at a fraction of the cost.
OpenAI • GPT-5.6
$0.20 / $1.20
/ 1M tokens (input / output)
After an 80% price cut in July 2026, Luna became the value outlier among frontier-family models: it outperforms the previous generation's top-end Opus tier on coding evals while costing about a fiftieth of Fable 5 per input token. This is the model to route bulk traffic through in a tiered architecture.
Input price
GPT-5.6 Luna is 90% cheaper than GPT-5.6 Terra on input tokens.
Output price
GPT-5.6 Luna is 90% cheaper than GPT-5.6 Terra on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | GPT-5.6 Terra | GPT-5.6 Luna | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $4 | $0 | $4 |
| Moderate — 10M in / 2M out | $44 | $4 | $40 |
| Heavy — 100M in / 20M out | $440 | $44 | $396 |
Specification comparison
| Attribute | GPT-5.6 Terra | GPT-5.6 Luna |
|---|---|---|
| Input (/ 1M tokens) | $2.00 | $0.20 |
| Output (/ 1M tokens) | $12.00 | $1.20 |
| Cached input | $0.20 | $0.02 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-02 | 2026-02 |
| Relative latency | medium | low |
| Open weights | No | No |
| API model ID | gpt-5.6-terra | gpt-5.6-luna |
| Status | stable | stable |
GPT-5.6 Terra: Cut 20% from the $2.50/$15 launch price on 2026-07-30.
GPT-5.6 Luna: Cut 80% from the $1/$6 launch price on 2026-07-30.
Choose GPT-5.6 Terra if…
- Customer support and chat backends
- RAG and document processing pipelines
- Mid-complexity coding tasks
- Tool-calling agents at scale
Choose GPT-5.6 Luna if…
- Classification and content moderation
- High-frequency agent subtasks
- Bulk summarization
- Cost-sensitive chat features
Frequently asked
Is GPT-5.6 Terra or GPT-5.6 Luna cheaper?
GPT-5.6 Luna is cheaper. On a blended 3:1 input-to-output workload it costs about 10.0x less than GPT-5.6 Terra.
Which has the larger context window, GPT-5.6 Terra or GPT-5.6 Luna?
Both accept up to 1.05M tokens, so context is not a differentiator here.
Should I use GPT-5.6 Terra or GPT-5.6 Luna?
Pick GPT-5.6 Terra for balanced production workloads. Pick GPT-5.6 Luna for high-volume work on a tight budget. If cost dominates the decision, GPT-5.6 Luna wins; if you need the capability ceiling, benchmark both on your own evals before committing.