Tencent's 770B Hy4 weights make model spend a memory-capacity question
Hy4 preview carries 2.6 times Hy3's parameters and 3.9 times its context window. Tencent is giving the weights away. That means the build column in next quarter's model budget gets priced in accelerator memory rather than in tokens.
The Investor · Invest desk

What happened
- Tencent published Hy4 Preview, a text-only open-weight model listing 770 billion total parameters, 49 billion active, a one-million-token context window, and 1.56TB of files on Hugging Face.
- The July predecessor, Hy3, carried 295 billion total parameters, 21 billion active, a 256,000-token window and 598GB of weights, which is the baseline this preview is measured against.
- In a separate item on the same blog, Cambridge's Anil Madhavapeddy switched his exploit-finding agents to DeepSeek V4 Pro after Claude Fable refused the task.
Why it matters
- Who has to decide decision Anyone renewing a per-token text contract next quarter now has a second column to fill in, and it is an amortisation argument about accelerator memory rather than a discount conversation with a vendor.
- Who's exposed exposure Because Hy4 accepts no image input, the substitution pressure reaches text pipelines only, and document, screenshot and vision workloads stay with whoever charges per token for them.
- What's now possible capability Refusal policy is becoming a purchasing criterion rather than a safety footnote, since work simply relocates to whichever model will accept the job, as the OCaml maintainer's swap shows.
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Sparsity is the first number I would put on the whiteboard: 49 billion active out of 770 billion total [1] is 6.4% of the weights doing work on any given token [11], against 7.1% for July's 295B/21B Hy3 [2][12], so the model got 2.6 times heavier to store [10] while the per-token compute path widened only 2.3 times [8].
The file size is where the buy-side arithmetic actually lives. Divide 1.56TB by 770 billion parameters and you get roughly 2.03 gigabytes per billion, which is two bytes a parameter, and Hy3's 598GB over 295 billion is the same 2.03 [13], so nobody has quantized anything on your behalf and the memory problem is yours to solve. At 80GB per accelerator, 1.56TB is twenty devices before the first token comes out [14]. That is the honest entry price of the build column.
Free weights still cap what a vendor can charge for text inference, though, because the buyer's alternative was never only self-hosting. Simon Willison ran his pelican-on-a-bicycle prompt through OpenRouter at the default high reasoning setting [4], which means somebody else had already bought the memory and was reselling access to it, and a reseller of downloadable weights competes on margin rather than on capability. I do not have those per-token prices in front of me. It is the first number I would go and get.
Tencent has put 1.56TB on Hugging Face [1], and that choice is its own statement: it cannot now sell access to this generation's text capability, so it is buying distribution and default-choice status with revenue it will not collect a token at a time.
The reasoning dial is the finding here, because there isn't one. The chat template accepts only "high" and "no_think" [3], so a team that wants a third of the thinking budget has no setting to ask for it, and hidden reasoning tokens are precisely the line item that breaks a monthly estimate. Willison noticed the trace writing in clipped, half-grammatical English, which he reads as perfect grammar not being worth the tokens [6]; that is a vendor compressing its own cost, and it implies the thinking runs long enough to be worth compressing.
This is probably wrong, but the direction I would bet on is that the marginal price of frontier-adjacent text tokens converges on hosting cost plus a thin margin. What would prove it wrong: hosted Hy4 prices arriving close to closed-model text pricing, which would say accelerator memory rather than model access is the genuinely scarce good.
What to watch
- Quantized community repacks that cut the 1.56TB footprint below what a single host can hold, which changes who can run this without renting.
- Whether Tencent's next preview repeats the roughly 2.6x-per-generation size step or holds size flat and cuts serving cost instead.
- Published throughput and price numbers for the full one-million-token window, which the preview announcement does not include.
Information, not investment advice. This story is general information about companies and markets, drawn from cited reporting. It is not a recommendation to buy, sell or hold any security; check the cited sources before acting.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence62
- Adoption18
- Hype gap+30
- Incentives65
- Confidence60
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Tencent released Hy4 Preview, an open-weight text-input-only (no vision) LLM with 770B total parameters, 49B active parameters, a 1M-token context window, and 1.56TB of files on Hugging Face.
- [2]
Tencent's previous model, Hy3, released in July, was 295B total parameters, 21B active, a 256,000-token context window, and 598GB.
- [3]
Hy4's chat_template.jinja on Hugging Face defines only two reasoning_effort values, 'high' (the default) and 'no_think', raising an exception on any other value.
- [4]
Willison tried his 'Generate an SVG of a pelican riding a bicycle' prompt against Hy4 with the default high reasoning via OpenRouter.
- [5]
Anil Madhavapeddy, a Cambridge computer science professor and OCaml compiler core maintainer, demonstrated agent-driven exploit discovery by switching to DeepSeek V4 Pro when Claude Fable refused the task.
- [6]
Willison observed that Hy4's reasoning trace uses slightly truncated English, which he attributes to perfect grammar not being useful or token efficient for hidden reasoning text.
- [7]
Hy4's 770B total parameters are about 2.6 times Hy3's 295B.
- [8]
Hy4's 49B active parameters are about 2.3 times Hy3's 21B active.
- [9]
Hy4's 1M-token context window is about 3.9 times Hy3's 256,000 tokens.
- [10]
Hy4's 1.56TB of weight files is about 2.6 times Hy3's 598GB.
- [11]
Hy4 activates about 6.4% of its parameters per token.
- [12]
Hy3 activated about 7.1% of its parameters per token.
- [13]
Both releases are published at about 2.03 GB per billion parameters, roughly two bytes per parameter, implying unquantized weights in both cases.
- [14]
Holding Hy4's 1.56TB of weights resident requires about twenty accelerators if each holds 80GB.
Sources
2 independent publishers whose own reporting we read for this story.
- simonwillison.netSimon Willison on llms
1 article · August 30, 2026
- Tencent Releases and Open-Sources Tencent Hy4 preview - Tencent
tencent.com
1 article · August 31, 2026
Topics and entities
Topics
- Open-weight LLMs
- Inference Hardware
- Mixture of Experts Architectures
Entities
- Anil Madhavapeddy
- OpenRouter
- Tencent
- Hugging Face
- Simon Willison