Punches far above its price: GPQA Diamond 92.3%, SWE-bench Pro 62.7%, Terminal-Bench 2.1 84.7%
$0.20/$1.20 per 1M after the July 30, 2026 price cut — dramatically cheaper per token than Gemini 3.6 Flash
Full 1.05M-token context at budget pricing — larger than most rival small models
Weaknesses
Long-context recall collapses at scale: 41.3% on 512K–1M token tasks vs Terra's 72.5%
Text and image input only — no video, audio, or native PDF ingestion like Gemini 3.6 Flash
Real-world use cases
What people actually use GPT-5.6 Luna for.
High-volume summarization and drafting at $0.20/1M input
Routine steps in agent pipelines where Sol/Terra would be overkill
Budget coding assistance — 62.7% SWE-bench Pro within ~2 points of Sol at 1/25th the output cost
How GPT-5.6 Luna compares
The nearest models people weigh against it, and what actually separates them.
vs GPT-6 Astra — Against GPT-6 Astra (OpenAI), GPT-5.6 Luna runs about 98% cheaper per token and answers faster. Take GPT-5.6 Luna unless you specifically need what GPT-6 Astra does better.
vs GPT-5.4 — Against GPT-5.4 (OpenAI), GPT-5.6 Luna runs about 92% cheaper per token, takes 3.9x the context and answers faster. Take GPT-5.6 Luna unless you specifically need what GPT-5.4 does better.
vs GPT-5.5 — Against GPT-5.5 (OpenAI), GPT-5.6 Luna runs about 96% cheaper per token, takes 1.1x the context and answers faster. Take GPT-5.6 Luna unless you specifically need what GPT-5.5 does better.
Price History
GPT-5.6 Luna pricing over time
↑100% since Aug 7
25 data points · tracked daily since Aug 7, 2026
Ready to try it?
Start using GPT-5.6 Luna
Cheap high-throughput summarization, drafting, and routine agent steps. Start free — no card required.
OpenAI's September 3, 2026 frontier release — the first GPT-6 model and OpenAI's answer to Claude Fable 5.1 two days earlier. State of the art on computer use (OSWorld 2.0 72.6% in ~47% less time than GPT-5.6 Sol), agentic coding (Terminal-Bench 4.0 57.9%), and frontier math (FrontierMath Tier 4 97.6%). $10/$50 per 1M tokens, 1.05M context, 128K output, knowledge cutoff April 30, 2026.
Verdict
OpenAI's frontier answer to Fable 5.1 — computer-use and agentic-coding leader at $10/$50.
Quality score
99%
Pricing
$10.00/1M in
$50.00/1M out
Speed
Deliberate
2/5 speed
Context
1.1M tokens
Released September 3, 2026. API ID gpt-6-astra; rolling out over the coming days to ChatGPT Plus, Pro, Business and Enterprise (usage inside existing allowances; GPT-6 Astra Pro for Pro/Business/Enterprise; Enterprise off by default), the OpenAI API, Microsoft Azure and Amazon Bedrock. Standard API pricing $10/$50 per 1M tokens; Fast mode is up to 2x speed at 2x price; cache reads and writes have separate rates. Model docs list 1,050,000 context, 128,000 max output, knowledge cutoff April 30, 2026, reasoning efforts up to 'max'. Published launch numbers (Astra / GPT-5.6 Sol / Fable 5.1 / Opus 5): OSWorld 2.0 72.6 / 65.7 / — / 70.2; Terminal-Bench 4.0 57.9 / 37.3 / 55.8 / 52.3; Terminal-Bench Science 0.1 64.6 / 22.4 / 52.6 / 30.0; FrontierMath Tier 4 v2 97.6 / 83.0 / 87.8 / 73.2; GPQA Diamond 96.0 / 94.6 / 93.7 / 93.7; Humanity's Last Exam w/ tools 57.2 / — / 65.0 / 63.6; AutomationBench 41.4 / 18.1 / 31.4 / 26.9; DeepSWE v1.1 74.1 / 72.7 / 67.4 / 73.7; ARC-AGI-2 95.0 / 92.5 / 90.0 / 90.4; ARC-AGI-3 99.9 (OpenAI responses-API harness; ARC Prize's stateless runs score far lower) / 7.8 / — / 30.2; ExploitBench 100.0 / 78.5 / — / 70; SRE-Bench 88.0 / 55.9; Artificial Analysis Intelligence Index v4.1.1 61.2 / 60.9 / 65.7 / 63.1. Meets the Critical threshold for cybersecurity under OpenAI's Preparedness Framework; advanced cyber workflows gated behind OpenAI Daybreak. All figures from OpenAI's launch post and model docs, verified September 4, 2026.
Computer use leaderFrontierAgenticReasoningLong contextPremiumNew
Best for
Computer and browser use, long-horizon agentic coding, and frontier math and science work
OpenAI's latest agentic flagship for coding, research, computer-use workflows, and long multi-step knowledge work.
Verdict
Best OpenAI flagship for agentic coding, research, and computer-use work.
Quality score
94%
Pricing
$5.00/1M in
$30.00/1M out
Speed
Balanced
3/5 speed
Context
1M tokens
Ranked from public benchmark and pricing data verified April 26, 2026: SWE-Bench Pro 58.6%, Terminal-Bench 2.0 82.7%, $5/$30 per 1M tokens, 1M API context.
AgenticCodingComputer useLong contextPremium
Best for
Agentic coding, computer-use workflows, and complex research tasks
GPT-5.6 Luna costs $0.2 per million input tokens and $1.2 per million output tokens on the API, with cached input at $0.02 per million. A month of 10M input and 2M output tokens runs about $4.40 at list price, before any batch or caching discounts.
What is the context window of GPT-5.6 Luna?
GPT-5.6 Luna has a 1.1M tokens context window, with up to 128k tokens of output per response. That is the total of prompt plus response the model can hold in one request.
What is the knowledge cutoff of GPT-5.6 Luna?
GPT-5.6 Luna's training data runs through February 16, 2026, and the model was released on July 9, 2026. For anything after that date it needs web search or documents in the prompt.
What is GPT-5.6 Luna best for?
GPT-5.6 Luna is best for cheap high-throughput summarization, drafting, and routine agent steps. It is a strong fit when that workflow matters more than the tradeoffs around budget pricing and fast speed.
When should I avoid GPT-5.6 Luna?
Your workload actually uses the long context window — recall drops to 41% past 512K tokens.
What is a cheaper alternative to GPT-5.6 Luna?
Grok 4.5 (xAI) at $2.00/1M/1M input against GPT-5.6 Luna's $0.20/1M/1M. Best cost-per-solved-task coding agent — efficiency over ceiling. Compare it first if GPT-5.6 Luna's pricing is the thing stopping you.
What is a faster alternative to GPT-5.6 Luna?
GPT-6 Astra — deliberate against GPT-5.6 Luna's fast, with 1.1M tokens of context. Worth the swap when response time is what your users notice rather than the last few points of reasoning depth.
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