Xiaomi open-sources MiMo-⁠V2.6-⁠Pro, after a $2.6 million reinforcement-learning run

1 month ago

From the Hacker News front page: Xiaomi’s MiMo-V2.6; Alice GG: Attention is all you have; Bryan Cantrill on what Sun got wrong; Georgia Tech’s Transformer Explainer; and Kev, small open decision models. MiMo v2.6 https://mimo.xiaomi.com/mimo-v2-6 — “Scaling RL, Fully Open-Sourced”; RL training progress chart Discussion, about 1,100 points and about 480 comments: https://news.ycombinator.com/item?id=49792730 Attention is all you have https://alicegg.tech/2026/09/21/attention Discussion, about 1,100 points and about 330 comments: https://news.ycombinator.com/item?id=49787726 What Sun got wrong https://bcantrill.dtrace.org/2026/09/20/what-sun-got-wrong/ Discussion, about 690 points and about 420 comments: https://news.ycombinator.com/item?id=49787436 Transformers Explained Visually https://poloclub.github.io/transformer-explainer/ Discussion, about 660 points and 92 comments: https://news.ycombinator.com/item?id=49792342 Kev: Tiny Jev-like family of decision models built on top of Qwen3.5 https://github.com/jaredpalmer/kev/tree/main — development sets; the README says this is not a controlled comparison Discussion, about 460 points and about 200 comments: https://news.ycombinator.com/item?id=49783999 The front page that day: https://news.ycombinator.com/front?day=2026-09-21

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Chapters

  1. 0:00Front page
  2. 0:10Two open models, old prices
  3. 0:26What the reinforcement-learning run cost
  4. 0:46Before and after the run
  5. 0:58Transparency over scores
  6. 1:12Whatever you look at shapes you
  7. 1:26When the web was better
  8. 1:40Bored with the mechanics
  9. 1:56The buying experience
  10. 2:10A live model in a browser tab
  11. 2:28What it made click
  12. 2:41Small models for boring decisions
  13. 2:58A smaller alternative
Show transcript
  1. Near the top of the Hacker News front page, with about eleven hundred points: Xiaomi open sourced MiMo V two point six Pro, its most capable model to date.

    Slide text
    Monday, September 21, 2026

    Xiaomi open-sources MiMo-⁠V2.6-⁠Pro, after a $2.6 million reinforcement-learning run

    Also on the front page
    • Alice GG: Attention is all you have
    • Bryan Cantrill on what Sun got wrong
    • Georgia Tech’s Transformer Explainer
    • Kev, small open decision models
  2. Xiaomi released two open weight models, a larger Pro and a cheaper Flash, both handling text, images and audio natively. Pricing did not move. Their claim: Pro is the strongest open source model on the Artificial Analysis index.

    Slide text
    Hacker News

    MiMo-V2.6 from Xiaomi

    What shipped
    Two natively omnimodal models with open weights: a larger Pro and a cheaper Flash.
    What did not change
    API pricing stays where the MiMo-V2.5 series left it.
    Xiaomi’s claim
    Pro scores 46.32 on the Artificial Analysis Intelligence Index, the highest of any open-source model.
  3. Pro's reinforcement learning run cost about two point six million dollars of compute: thirty steps over roughly seven hundred fifty thousand trajectories, in under six days. Flash's cost about eight hundred fifty thousand dollars. Xiaomi streamed both runs live, and open sourced the code and the training environments.

    Slide text
    Hacker News

    The reinforcement-learning run took under six days
    • MiMo v2.6 — “Scaling RL, Fully Open-Sourced”

    $2.62M
    of compute for MiMo-V2.6-Pro
    30 reinforcement-learning steps over roughly 750,000 trajectories.
    $0.85M
    for MiMo-V2.6-Flash, the same 30 steps
    Streamed live as it ran. The report, RL code and training environments are open-sourced.
  4. On DeepSWE, a software engineering benchmark held out of training, Pro's score rose from about fifty eight points to seventy three. Flash's rose from about forty nine points to sixty six.

    Slide text
    Hacker News

    MiMo-V2.6 on a coding benchmark held out of training

    Before the run
    After 30 steps
    Pro
    58.4 points on DeepSWE v1.1
    72.6 points on DeepSWE v1.1
    Flash
    48.8 points on DeepSWE v1.1
    65.7 points on DeepSWE v1.1
  5. Commenter rao-v picks out the openness rather than the scores. The dashboard ran while the training did, and the report even includes the benchmarks where they did poorly. Alice G G's essay is called Attention is all you have.

    Slide text
    Hacker News

    In the thread

    “The realtime dashboard they shared during training … was an incredible learning and teaching tool for me.”

    rao-v, on the run being published as it happened
  6. An essay that opens with the Tetris effect: play it daily for a few weeks and the shapes start appearing in clouds and buildings. Whatever you focus on shapes how you think. And a recommendation engine picks that focus for you.

    Slide text
    Hacker News

    Attention is all you have

    The Tetris effect
    Play it daily for a few weeks and the shapes start turning up in clouds and buildings.
    The lesson drawn from it
    Whatever you focus on long enough ends up shaping your thoughts.
    The problem
    Less and less of that focus is chosen. A recommendation engine picks it.
  7. Commenter tripleee offers a blunter version, and this is their view rather than anything the essay argues. Peak internet, they reckon, was the short window when it was there but you were not permanently attached to it. So what did Sun get wrong?

    Slide text
    Hacker News

    In the thread

    “Peak internet was the brief period of time when it was available but we weren’t permanently connected.”

    tripleee — a view offered in the thread, not a claim in the article
  8. Bryan Cantrill distills it to one line: Sun had become bored with the mechanics of running a business. A startup on OpenSolaris wanted to buy Sun hardware and could not get Sun to answer the phone. Dell answered an overnight web form by morning.

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    Hacker News

    What Sun got wrong

    Fifteen years on, distilled to one line
    Sun had become bored with the mechanics of running a business.
    2005
    A startup growing fast on OpenSolaris wanted to buy a pile of Sun hardware, and could not get Sun to pick up the phone.
    The contrast
    A web form filled in at night, and by morning a Dell account executive who felt like he worked for them.
  9. Commenter coreyh14444 remembers it from the customer's side, which is the same complaint the post makes. Buying from the old workstation vendors meant live sales meetings and endless quote revisions.

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    Hacker News

    In the thread

    “I remember calculating the server rails and power cords for a new Alpha server were going to cost more than a shipped/delivered Dell server that I could get the next day.”

    coreyh14444, buying hardware in the late 1990s
  10. An explainer out of Georgia Tech runs a small GPT-2, about a hundred twenty million parameters, inside your browser tab. Type a prompt and watch the tokens, attention weights and next token probabilities move. An old model, chosen because it has the same parts as the current ones.

    Slide text
    Hacker News

    Transformers Explained Visually

    124 million
    parameters in GPT-2 (small), running inside the page
    Type your own prompt and watch tokens, attention weights and next-token probabilities move. An old model, built from the same parts as current ones.
  11. Commenter mhl47 says what it unstuck, and the page bears it out. Attention and the feed forward layer alternate through twelve stacked blocks, so other tokens mix back in at every one.

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    Hacker News

    In the thread

    “I always struggled to see how transformers get away with compressing all context in a flat vector (e.g. 768 numbers here) between attention and the MLP …”

    mhl47, on what the visualisation unstuck
  12. Kev is a family of small, openly licensed models for the dull decisions: which team owns this ticket, does it need a human, how annoyed is the customer. On questions it never trained on, the largest lands within one point of Jev, the hosted model it imitates.

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    Hacker News

    Kev: small decision models you can run yourself

    Jev, hosted by TypeSafe
    Kev-27B, open weights
    Questions Kev never trained on
    85.7 % accuracy
    84.8 % accuracy
  13. Commenter nico pushes a smaller option, from their own experience rather than anything the project measured. For plain classification, fifty to a hundred labelled examples and a classifier over embeddings trains on an ordinary processor in under five minutes.

    Slide text
    Hacker News

    In the thread

    “If you only need classification, and you can provide some training data, you can ask Codex/Claude to build an embeddings + logistic classifier model for you.”

    nico — their own results, not measured by the project

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