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Introducing Hy4 Preview

AnnouncementModelAug 29, 2026

Tencent released Hy4 Preview, an open-weight text-only LLM with 770B total parameters, 49B active parameters, and a 1M token context window, weighing 1.56TB on Hugging Face. The model is substantially larger than Tencent's Hy3 from July, which had 295B parameters, 21B active, and 256,000 context. Its chat template supports two reasoning effort levels, "high" (default) and "no_think". Testing via OpenRouter showed a reasoning trace using truncated English.

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Citation chain · 1 source

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Hugging FaceCompanyOpenRouterCompanyTencentCompanyHy3ModelHy4 PreviewModel
Canonical: https://simonwillison.net/2026/Aug/29/hy4/