Head-to-head comparison
DeepSeek V4 Pro 0813 (DeepSeek) and GPT-5.6 Luna (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.
Snapshot as of 9 September 2026
As of 9 September 2026, DeepSeek V4 Pro 0813 holds the stronger ModelCap Index position (#25 vs #28); GPT-5.6 Luna is 1.4× cheaper per output token ($1.20/1M vs $1.74/1M); and DeepSeek V4 Pro 0813 ships open weights.
Evidence: 4 public benchmark observations across 4 boards · 6 public benchmark observations across 6 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.
Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.
Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.
DeepSeek V4 Pro 0813 ranks higher on the ModelCap Index as of 9 September 2026: #25 against #28. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.
GPT-5.6 Luna is cheaper on output tokens: $1.20/1M against $1.74/1M. Input tokens are $0.579/1M for DeepSeek V4 Pro 0813 and $0.20/1M for GPT-5.6 Luna. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $2.03 for DeepSeek V4 Pro 0813 versus $1.00 for GPT-5.6 Luna. GPT-5.6 Luna costs 50.7% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.
Both publish a 1M-token context window.
Arena coding: DeepSeek V4 Pro 0813 1505, GPT-5.6 Luna 1497 — DeepSeek V4 Pro 0813 leads. AA Terminal-Bench 2.1: DeepSeek V4 Pro 0813 78.7%, GPT-5.6 Luna 80.9% — GPT-5.6 Luna leads.
DeepSeek V4 Pro 0813: Open weights. GPT-5.6 Luna: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.
ModelCap currently lists 19 API providers for DeepSeek V4 Pro 0813 and 3 for GPT-5.6 Luna, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.
Every figure comes from the sealed ModelCap dataset published 9 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.