ZMIME
Comparison · 3 models · Updated Oct 4, 2026

GPT-5.6 Luna vs GPT-6 Luna vs DeepSeek V4.1 Flash

GPT-6 Luna comes out ahead, 78 to 72 and 69 on our weighted score, and it is the cheaper option too.

  1. OpenAI

    GPT-5.6 Luna

    Released Jul 9, 2026

    69/100
    • ECI156.5
    • Price$0.20 / $1.20
    • Context1.05M
    Full specs Remove GPT-5.6 Luna
  2. Our pick

    OpenAI

    GPT-6 Luna

    Released Sep 22, 2026

    78/100
    • ECI—
    • Price$0.10 / $0.50
    • Context1.05M
    Full specs Remove GPT-6 Luna

  3. DeepSeek

    DeepSeek V4.1 Flash

    Released Sep 10, 2026

    72/100
    • ECI155.0
    • Price$0.15 / $0.60
    • Context1M
    Full specs Remove DeepSeek V4.1 Flash
01 — Verdict

GPT-6 Luna is our pick

GPT-6 Luna is the better all-round choice, scoring 78/100 against DeepSeek V4.1 Flash (72) and GPT-5.6 Luna (69). It leads on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceGPT-6 LunaGPT-6 Luna $0.20 · DeepSeek V4.1 Flash $0.263 · GPT-5.6 Luna $0.45 per 1M tokens (3:1 blend)
  • Longest contextGPT-5.6 Luna and GPT-6 LunaGPT-5.6 Luna 1,050,000 · GPT-6 Luna 1,050,000 · DeepSeek V4.1 Flash 1,000,000 tokens
  • Widest inputsGPT-5.6 Luna and GPT-6 LunaGPT-5.6 Luna: Text, Images, PDFs · GPT-6 Luna: Text, Images, PDFs · DeepSeek V4.1 Flash: Text, Images
  • Self-hostingDeepSeek V4.1 FlashPublishes downloadable weights (MIT)
How the score is built
MeasureWeightGPT-5.6 LunaGPT-6 LunaDeepSeek V4.1 Flash
Price50%668377
Inputs & features30%808070
Context window20%616160
Overall100%69/10078/10072/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

GPT-5.6 Luna vs GPT-6 Luna vs DeepSeek V4.1 Flash specifications side by side
SpecificationGPT-5.6 LunaOpenAIGPT-6 LunaOpenAIDeepSeek V4.1 FlashDeepSeek
Capability
Capabilities Index (ECI)156.5 (best)—155.0
ECI rank#21 of 148 (best)—#29 of 148
GPQA DiamondGraduate-level science questions91.6% (best)90.5%—
FrontierMath Tiers 1–3Research-level mathematics82.1% (best)79.0%—
OTIS Mock AIME 2024–2025Competition mathematics98.3%98.9% (best)—
SimpleQA VerifiedShort factual questions41.0%41.4% (best)—
Price per million tokens
Input$0.20$0.10 (best)$0.15
Output$1.20$0.50 (best)$0.60
Cached input$0.02$0.01$0.003 (best)
Blended (3:1)$0.45$0.20 (best)$0.263
Long-context rateOver 272K: $0.40 / $1.80Over 272K: $0.20 / $0.75Same rate
Price sourceOfficial OpenAI APIOfficial OpenAI APIOfficial DeepSeek API
Limits
Context window1,050,000 tokens (best)1,050,000 tokens (best)1,000,000 tokens
Max output128,000 tokens128,000 tokens384,000 tokens (best)
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesYesNo
AudioNoNoNo
VideoNoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh · maxYeslow · high · max
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryOpenMIT
API model IDgpt-5.6-lunagpt-6-lunadeepseek-flash
API providers382450 (best)
ReleasedJul 9, 2026Sep 22, 2026Sep 10, 2026
Knowledge cutoffFeb 16, 2026May 18, 2026May 2025
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • GPT-5.6 Luna$4.40
  • GPT-6 Luna$2.00
  • DeepSeek V4.1 Flash$2.70
04 — Questions

Which should you choose?

Which is better: GPT-5.6 Luna, GPT-6 Luna or DeepSeek V4.1 Flash?

GPT-6 Luna is the better all-round choice, scoring 78/100 against DeepSeek V4.1 Flash (72) and GPT-5.6 Luna (69). It leads on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

Which is cheaper, GPT-5.6 Luna, GPT-6 Luna or DeepSeek V4.1 Flash?

GPT-6 Luna is cheaper at $0.10 input / $0.50 output per million tokens (official OpenAI API price). DeepSeek V4.1 Flash costs $0.15 input / $0.60 output per million tokens (official DeepSeek API price); GPT-5.6 Luna costs $0.20 input / $1.20 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $0.20 per million tokens for GPT-6 Luna versus $0.263 for DeepSeek V4.1 Flash (1.3× as much) and $0.45 for GPT-5.6 Luna (2.3× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers all three models yet. GPT-5.6 Luna has an ECI of 156.5, GPT-6 Luna has not been scored yet and DeepSeek V4.1 Flash has an ECI of 155.0.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.6 Luna, GPT-6 Luna and DeepSeek V4.1 Flash yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.6 Luna and GPT-6 Luna have the largest context windows (1,050,000 and 1,050,000 tokens), against 1,000,000 for DeepSeek V4.1 Flash. Maximum output per response: GPT-5.6 Luna up to 128,000, GPT-6 Luna up to 128,000, DeepSeek V4.1 Flash up to 384,000 tokens.

Which can read images, PDFs, audio or video?

GPT-5.6 Luna accepts text, images and PDFs; GPT-6 Luna accepts text, images and PDFs; DeepSeek V4.1 Flash accepts text and images. GPT-5.6 Luna handles the widest range of inputs.

Are any of these open source?

DeepSeek V4.1 Flash publishes its weights (MIT) and can be self-hosted; GPT-5.6 Luna and GPT-6 Luna is proprietary.

Which is newer?

GPT-6 Luna is the newest, released Sep 22, 2026. DeepSeek V4.1 Flash came out Sep 10, 2026; GPT-5.6 Luna came out Jul 9, 2026. Knowledge cutoff: GPT-5.6 Luna Feb 16, 2026, GPT-6 Luna May 18, 2026, DeepSeek V4.1 Flash May 2025.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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