GPT-5.6 Luna vs GPT-5.6 Terra
The two efficiency tiers of GPT-5.6 head to head.
What the numbers say
- GPT-5.6 Luna is about 2.5x cheaper on output tokens (66.0 vs 165 credits per 1M).
- Both take the same 1.1M-token context window.
- GPT-5.6 Luna is the newer release (July 2026 vs July 2026).
Derived from the live registry Zeplik routes and bills against. Credits: 1 credit = $0.10, raw provider rate with a 1.10x margin.
Side by side
GPT-5.6 Luna
OpenAI
GPT-5.6 Luna is a fast, cost-efficient model in OpenAI's GPT-5.6 series. It is suited for high-volume, latency-sensitive tasks such as chat, classification, and lightweight agentic workflows, providing capable reasoning for...
- Provider
- OpenAI
- Context window
- 1.1M tokens
- Input price
- 11.0 credits / 1M tokens ($1.00 raw)
- Output price
- 66.0 credits / 1M tokens ($6.00 raw)
- Vision (image input)
- Yes
- Tool calling
- Yes
- Extended reasoning
- No
Best for
- Hard problems where answer quality matters more than cost: strategy, analysis, difficult writing
- Very long documents and codebases: a 1.1M-token window fits entire books or repositories in one conversation
- Working with images: screenshots, charts, photos and scanned documents alongside text
- Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows
GPT-5.6 Terra
OpenAI
GPT-5.6 Terra is a balanced model in OpenAI's GPT-5.6 series, positioned between the flagship Sol tier and the cost-efficient Luna tier. It is suited for everyday coding, reasoning, and agentic...
- Provider
- OpenAI
- Context window
- 1.1M tokens
- Input price
- 27.5 credits / 1M tokens ($2.50 raw)
- Output price
- 165 credits / 1M tokens ($15.00 raw)
- Vision (image input)
- Yes
- Tool calling
- Yes
- Extended reasoning
- No
Best for
- Hard problems where answer quality matters more than cost: strategy, analysis, difficult writing
- Very long documents and codebases: a 1.1M-token window fits entire books or repositories in one conversation
- Working with images: screenshots, charts, photos and scanned documents alongside text
- Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows
Try both on Zeplik
The honest answer to most model debates is to run your own prompt on both. Zeplik puts GPT-5.6 Luna and GPT-5.6 Terra in the same chat, so you can switch mid-conversation and compare answers on the work you actually do.