Story · Simon Willison
Introducing Hy4 Preview (Simon Willison)
blog post · Story page
Tencent's open-weight, text-only Hy4 Preview: 770B total parameters, 49B active, a 1M-token context window, 1.56TB on Hugging Face, up from Hy3's 295B in July. Simon Willison reads the chat template instead of the benchmarks and finds what appear to be two reasoning modes, high and no_think, for a harness to drive.
In plain words
- Tencent released Hy4 Preview, a text-only artificial intelligence system whose internal numerical settings can be downloaded.
- It contains 770 billion internal values, with 49 billion active while it processes text.
- It can consider up to 1 million small text units from one request.
- Developers connecting Hy4 to other software only need to support two reasoning choices: highest or off.
Appeared in
- Maersk's 100,000 corrections, preference-trap evals, and Tencent's Hy4 Preview
Aug 31, 2026 · in the sections
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