GPT-5.6 Terra vs GPT-6 Luna
GPT-5.6 Terra and GPT-6 Luna are closely matched at 50.3 and 44.5 on the LLM Stats Score. GPT-6 Luna is 22.5x cheaper per token.
OpenAI · OpenAI · Updated for 2026
Which is better?
GPT-5.6 Terra and GPT-6 Luna are closely matched on the overall LLM Stats Score at 50.3 and 44.5.
In the 4 individual benchmarks reported for both models, GPT-6 Luna wins 3; this is a narrower head-to-head signal than the composite indexes.
On price, GPT-6 Luna is roughly 22.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-5.6 Terra
- you want predictable pricing at $2.00/M input and $12.00/M output
Choose GPT-6 Luna
- you value its reported benchmark strengths — it wins 3 of 4 exact shared results
- cost matters — it's about 22.5x cheaper per token
- you want the most recent training data — it shipped Sep 2026
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
45 reported for GPT-5.6 Terra · 5 for GPT-6 Luna
GPT-5.6 Terra outperforms in 1 benchmarks (DeepSWE 1.1), while GPT-6 Luna is better at 3 benchmarks (Agents' Last Exam, FrontierCode 1.1, OSWorld 2.0).
GPT-6 Luna shows notably better performance in the majority of benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.6 Terra ($2.00/1M tokens) is 20.0x more expensive than GPT-6 Luna ($0.10/1M tokens).
For output processing, GPT-5.6 Terra ($12.00/1M tokens) is 24.0x more expensive than GPT-6 Luna ($0.50/1M tokens).
In conclusion, GPT-5.6 Terra is more expensive than GPT-6 Luna.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Both models have the same input context window of 1,050,000 tokens. Both models can generate responses up to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both GPT-5.6 Terra and GPT-6 Luna support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.6 Terra
GPT-6 Luna
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
GPT-5.6 Terra was released on 2026-07-09, while GPT-6 Luna was released on 2026-09-22.
GPT-6 Luna is 3 months newer than GPT-5.6 Terra.
Jul 9, 2026
2 months ago
Sep 22, 2026
0 days ago
2mo newerKnowledge Cutoff
When training data ends
GPT-5.6 Terra has a knowledge cutoff of 2026-02-16, while GPT-6 Luna has a cutoff of 2026-05-18.
GPT-6 Luna has more recent training data (up to 2026-05-18), making it potentially better informed about events through that date compared to GPT-5.6 Terra (2026-02-16).
Feb 2026
May 2026
3 mo newerProvider Availability
GPT-5.6 Terra is available from OpenAI. GPT-6 Luna is available from OpenAI.
GPT-5.6 Terra
GPT-6 Luna
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.6 Terra and GPT-6 Luna side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.6 Terra vs GPT-6 Luna.