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Comparison · 2 models · Updated Oct 4, 2026

GPT-5.6 Luna vs DeepSeek V4.1 Flash

Too close to call on our weighted score (DeepSeek V4.1 Flash 78, GPT-5.6 Luna 78). The right pick depends on what you value most.

  1. OpenAI

    GPT-5.6 Luna

    Released Jul 9, 2026

    78/100
    • ECI156.5
    • Price$0.20 / $1.20
    • Context1.05M
    Full specs Remove GPT-5.6 Luna

  2. DeepSeek

    DeepSeek V4.1 Flash

    Released Sep 10, 2026

    78/100
    • ECI155.0
    • Price$0.15 / $0.60
    • Context1M
    Full specs Remove DeepSeek V4.1 Flash

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (DeepSeek V4.1 Flash 78/100, GPT-5.6 Luna 78/100), so choose by what matters most for your work: GPT-5.6 Luna for raw capability and DeepSeek V4.1 Flash on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-5.6 LunaCapabilities Index (ECI): GPT-5.6 Luna 156.5 · DeepSeek V4.1 Flash 155.0
  • Lowest priceDeepSeek V4.1 FlashDeepSeek V4.1 Flash $0.263 · GPT-5.6 Luna $0.45 per 1M tokens (3:1 blend)
  • Longest contextGPT-5.6 LunaGPT-5.6 Luna 1,050,000 · DeepSeek V4.1 Flash 1,000,000 tokens
  • Widest inputsGPT-5.6 LunaGPT-5.6 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 LunaDeepSeek V4.1 Flash
CapabilityCapabilities Index (ECI)50%8684
Price25%6677
Inputs & features15%8070
Context window10%6160
Overall100%78/10078/100
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 DeepSeek V4.1 Flash specifications side by side
SpecificationGPT-5.6 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%—
FrontierMath Tiers 1–3Research-level mathematics82.1%—
OTIS Mock AIME 2024–2025Competition mathematics98.3%—
SimpleQA VerifiedShort factual questions41.0%—
Price per million tokens
Input$0.20$0.15 (best)
Output$1.20$0.60 (best)
Cached input$0.02$0.003 (best)
Blended (3:1)$0.45$0.263 (best)
Long-context rateOver 272K: $0.40 / $1.80Same rate
Price sourceOfficial OpenAI APIOfficial DeepSeek API
Limits
Context window1,050,000 tokens (best)1,000,000 tokens
Max output128,000 tokens384,000 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesNo
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · high · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpenMIT
API model IDgpt-5.6-lunadeepseek-flash
API providers3850 (best)
ReleasedJul 9, 2026Sep 10, 2026
Knowledge cutoffFeb 16, 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
  • DeepSeek V4.1 Flash$2.70
04 — Questions

Which should you choose?

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

It is close. Our weighted score puts them within a point (DeepSeek V4.1 Flash 78/100, GPT-5.6 Luna 78/100), so choose by what matters most for your work: GPT-5.6 Luna for raw capability and DeepSeek V4.1 Flash on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

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

DeepSeek V4.1 Flash is cheaper at $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 $0.263 per million tokens for DeepSeek V4.1 Flash versus $0.45 for GPT-5.6 Luna (1.7× as much).

Which scores higher on benchmarks?

GPT-5.6 Luna scores higher on the Capabilities Index (ECI): GPT-5.6 Luna 156.5 (#21 of 148) and DeepSeek V4.1 Flash 155.0 (#29 of 148). The confidence ranges of the top two overlap (154.1–158.6 vs 148.8–157.6), so treat the gap as small.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.6 Luna and DeepSeek V4.1 Flash yet, so there is no like-for-like coding score. On overall capability, GPT-5.6 Luna leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.6 Luna has the largest context window at 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, 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; 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 is proprietary.

Which is newer?

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