GPT-5.6 Luna vs GPT-6 Astra
GPT-6 Astra leads the LLM Stats Score 59.9 to 45.1. GPT-5.6 Luna is 44.4x cheaper per token.
OpenAI · OpenAI · Updated for 2026
Which is better?
GPT-6 Astra leads the overall LLM Stats Score 59.9 to 45.1, ranking #1 overall.
In the 17 individual benchmarks reported for both models, GPT-6 Astra wins 17; this is a narrower head-to-head signal than the composite indexes.
On price, GPT-5.6 Luna is roughly 44.4x 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 Luna
- cost matters — it's about 44.4x cheaper per token
Choose GPT-6 Astra
- overall performance matters — it scores 59.9 and ranks #1 on LLM Stats
- your work emphasizes reasoning and coding — it leads those capability indexes
- you value its reported benchmark strengths — it wins 17 of 17 exact shared results
- 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 Luna · 22 for GPT-6 Astra
GPT-5.6 Luna outperforms in 0 benchmarks, while GPT-6 Astra is better at 17 benchmarks (Agents' Last Exam, ARC-AGI-3, AutomationBench, BenchCAD (with Python tool), BrowseComp, DeepSWE 1.1, ExploitBench, ExploitGym, FrontierCode 1.1, FrontierMath Tier 4 (v2), GeneBench-Pro, GPQA, HealthBench Professional, LifeSciBench, OSWorld 2.0, SEC-bench Pro, Terminal-Bench 4.0).
GPT-6 Astra significantly outperforms across most 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 Luna ($0.20/1M tokens) is 50.0x cheaper than GPT-6 Astra ($10.00/1M tokens).
For output processing, GPT-5.6 Luna ($1.20/1M tokens) is 41.7x cheaper than GPT-6 Astra ($50.00/1M tokens).
In conclusion, GPT-6 Astra is more expensive than GPT-5.6 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 Luna and GPT-6 Astra support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.6 Luna
GPT-6 Astra
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 Luna was released on 2026-07-09, while GPT-6 Astra was released on 2026-09-04.
GPT-6 Astra is 2 months newer than GPT-5.6 Luna.
Jul 9, 2026
2 months ago
Sep 4, 2026
1 weeks ago
1mo newerKnowledge Cutoff
When training data ends
GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while GPT-6 Astra has a cutoff of 2026-04-30.
GPT-6 Astra has more recent training data (up to 2026-04-30), making it potentially better informed about events through that date compared to GPT-5.6 Luna (2026-02-16).
Feb 2026
Apr 2026
2 mo newerProvider Availability
GPT-5.6 Luna is available from OpenAI. GPT-6 Astra is available from OpenAI.
GPT-5.6 Luna
GPT-6 Astra
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.6 Luna and GPT-6 Astra side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.6 Luna vs GPT-6 Astra.