Head-to-head comparison
GPT-5.6 Luna (OpenAI) and Hy4 preview (Tencent) 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 3 September 2026
As of 3 September 2026, GPT-5.6 Luna holds the stronger ModelCap Index position (#18 vs #19); GPT-5.6 Luna is 2.1× cheaper per output token ($1.20/1M vs $2.50/1M); and Hy4 preview ships open weights.
Evidence: 6 public benchmark observations across 6 boards · placed against measured peers on publisher-reported benchmarks, discounted for self-report optimism; floored directly above its measured family predecessor. 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.
GPT-5.6 Luna ranks higher on the ModelCap Index as of 3 September 2026: #18 against #19. 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.
GPT-5.6 Luna is cheaper on output tokens: $1.20/1M against $2.50/1M. Input tokens are $0.20/1M for GPT-5.6 Luna and $0.834/1M for Hy4 preview. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.
Both publish a 1M-token context window.
The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.
GPT-5.6 Luna: API only. Hy4 preview: Open weights. 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 3 API providers for GPT-5.6 Luna and 1 for Hy4 preview, 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 3 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.