Tencent Releases Hy4 Preview: 770B Params, 1M Context, Reasoning Mode

Simon Willison · rss · 2026-08-30

Tencent released Hy4 Preview, a new open-weight text LLM. It features 770B total parameters (49B active), a 1M token context window, and weighs 1.56TB on Hugging Face—a significant scale-up from the July Hy3 (295B/256k). The config reveals two reasoning effort levels: 'high' (default) and 'nothink'. Tests show the hidden reasoning trace optimizes for token efficiency, using truncated English when debating details like adding a helmet to a pelican.

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