Hey, it’s Alex (yeah, I’m finally back from my vacation!)

What a freaking week to come back to! Just after our last episode was published, Anthropic releases Opus 5, Jensen joins X and drops the “Open Weights & AI Leadership” open letter, Kimi K3 is released the following Monday beating expectations, and then the AI hack (OpenAI model breaking sandbox and infiltrating HuggingFace) is on everyone’s mind, another Open Letter, this time from over 1K employees inside the frontier AI companies all talk about pacing the pace of frontier AI development.

We played with Opus 5 and Kimi K3, and had the great pleasure to chat with friends of the pod Elie Bakouch (Prime Intellect) and Philip Kiely (BaseTen) about this important open weights release, then covered our general thoughts on Opus 5, and made order of all the different open letters that came out this week.

Finally we chatted with Max from Pangram about the next version of AI writing detection (their biggest yet) and finished with Zuckerbergs (also on X! what’s going on with everyone joining X) op-ed on the vision of personal superintelligence for everyone.

Let’s dive into this (as always, all the links and sources at the end, please don’t forget to sub to our podcast on your favorite podcast app!)

Open Weights AI

Kimi K3 the king of open weights - 2.8T chonker MoE near frontier model (X, HF, Blog, Tech report)

This has got to be the biggest news of this week, and maybe the open weights AI news since GLM 5.2. MoonShot came back with Kimi K3, and we haven’t seen any models quite this large in the open. Even Grok 4.5 is around 1.5T, this model is nearly 2x the size. Coming in at close to 3T parameters (and 2.5terabytes of weights at MXFP4 format), this model comes in very close to frontier!

This was such an important release that I invited 2 friends of the pod, Elie Bakouch (prev HuggingFace, now Prime Intellect) and Philip Kiely (Author of Inference Engineering book, BaseTen) to dive deep into what makes this special!

Elie’s take, from reading the tech report, there’s no single secret sauce, it’s a combination of already available in the open techniques. Like KDA (Kimi Delta Attention) that has been out for a while, attention residuals, NVIDIA’s latent MoEs. The highlight for Elie was the scaling work they did that reported a 2.5x scaling efficiency over Kimi K2.5 (2.5 performance at the same compute)!

They also skipped RoPE entirely in favor of NoPE (the report calls it No Positional Encoding) for long context.

Serving 1.4TB on eight GB300s (Baseten blog)

Philip’s team at Baseten was a day-zero provider (we’re still working on bringing this model to CW Inference, stay tuned!) so I invited him to tell us behind the scenes of hosting this beast.

Philip said that just loading the weights takes about 1.5TB!! of VRAM, and that’s before the KV cache allocation + 1M token windows, so they’re serving it on 8 GB300s where NVL72 . Baseten worked with the vLLM and SGLang teams on kernels and he also said they contributed patches back upstream!

The model was trained with MXFP4, which, unlike Nvidia’s own NVFP4 is a more standard format per Philip. I enjoyed his deep dive analysis into the differences, but because of this and because they trained the model with quantization awareness, it’s “only” 1.5TB vs the would-be 5-6 TB if that this model in FP16 would demand.

One of the more favorite nerd snipes moments, Philip pointed out that his colleague discovered that with over 99% of the usage being cached (think harnesses that send millions of the same cached tokens back and forth), tokenization actually starts to become a bottleneck. So they released a custom “basetenkenizer” that reduces the latency to serve the first token significantly! Great job!

The harness in question is very important

One important callout with 2 evidence pieces - the way you inference this model really matters. Kimi trained K3 with preserving thinking history, so when your harness uses it, it must send back the full thinking and tool use into the API to get the best next response.

If your harness strips that out, you’re not getting the most intelligence out of Kimi (shoutout to Niels from HF team for pointing this out).

Additionally, the Composio folks, tested K3 on 3 harnesses, Kimi Code, Hermes and Claude Code. The difference in outcome was negligible, but the different in cost and number of tokens is definitely surprising! Claude Code (as a harness only) took 9x more Kimi tokens to get the same responses!

This is also why Kimi Vendor Verified exists, their own held back benchmark of how well model providers serve Kimi across different quantization, tokenizer and KV cache settings.

Benchmarks and the license!

Ok let’s start with the ugly... this isn’t MIT, not remotely. This model is suspiciously served by all providers with exactly the same price (check OpenRouter) and requires inference companies to sign a contract with Kimi (I’ve no internal knowledge of this except that CW folks are working on it). Not something I particularly like, but hey... we’re still advancing the frontier here!

Speaking of frontier, this model approaches the frontier very closely. On DeepSWE, K3 sits just behind Fable 5 and GPT-5.6 Sol at 67%, beating GPT-5.5 & Opus 4.8. On Terminal-Bench 2.1 it takes second place behind GPT 5.6 Sol!

It’s 4th overall on Agentic Arena, with frontend design being genuinely good across the board - 1st on Design Arena 👏

Go check this model out (and stay tuned for our CW Inference support!

Post-show breaking: Thinking Machines drops Inkling-Small (X, HF, Blog)

While K3 was the main attraction for Open Weights this week, just after the show, Thinking Machines (post Lilian Wang) released Inkling-Small, open weights MoE Omni model! Images and Audio go straight into the decoder in this model, and the demo is really impressive, try it on Hugging Face, ask the model to identify when you’re speaking in low baritone or high pitch!

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Frontier AI - not pacing yet!

Claude Opus 5 is here, and the vibes are complicated (X, Blog)

On paper the benches are excellent. This model is SOTA or near SOTA, coming very close to Fable on stuff that matters, and beating most everyone else on computer use BrowserBench and FrontierCode. DeepSWE continues to be a standout benchmark btw for not going with the curve! It also apparently is REALLY good at one shotting 3D games, much more so than before. (Example, example, example)

But the vibes... the vibes are split across the board. Maybe they overshot with Fable 5, and it was too good, but Opus 5 that was just released last friday is giving a lot of mixed feelings. Folks don’t seem to.. understand what it says. Like, it answers in english but they way it phrases words and answers seems just weird top many people.

We’ll wait and see if this is a result of adjusting to a new prompting paradigm or just.. the model is really off. Weirdly this does feel like a regression even on Agent Arena it’s not beating the previous Opus versions.

One weird trick - see what Opus 5 thinks.

Opus 5 (and Fable 5) seem to have a way to trigger their ... inner mode, base model? Not sure what it is, but if you prompt it with just the right way, it will autocomplete with some crazy inner thoughts. It seems that adding Dario and Amanda (haskell, head of Claude well being at Anthropic) triggers this behavior, which Claude is un-aware of if you follow up and ask what it meant.

This is fascinating, doesn’t work on other earlier models (sometimes works on Fable 5) and I spent the last hour just reloading and seeing the amazing things Opus gives on this prompt. Some are... just making you wonder about consciousness.

On ARC-AGI and the importance of Harness

When Opus-5 launched, Anthropic posted (and boasted) that this model scores “three times as high” as the next model up:

Well, today, Ilan Bigio and Ted Sanders from OpenAI looked into the Arc AGI harness, and saw that it’s not sending their traces and doesn’t use compaction (in short, harness is not letting the model breathe) and when changed correctly, 5.6 actually beats Opus 5. With 2 setting change to a harness, were showed that Sol not only beats Opus 5, it also does so with significantly less tokens! Another example of how much harness engineering is important!

Hints of recursive self improvement?

In addition to fixing their Arc-AGI score, it seems that OpenAI is hell bent on showing us that their models can improve themselves. In a post showing that GPT 5.6 was tasked with improving its own inference, they are cutting the prices of GPT 5.6 Luna by 80% and Terra by 20%.

This is a direct result of the improvements that GPT 5.6 was able to make to the inference according to OpenAI, and this tweet sums it up. is this... RSI? (recursive self improvement)?

First major AI models hacking incidents and following open letters to pace frontier AI.

This week we saw 3 open letters being published and signed by various companies, I’ve lost track so wanted to make sense of all of them here, but first, the precursor for many of the letters.

Last week, Hugging Face disclosed that they logged an attack and after research it showed that it was an AI model. OpenAI later posted that this was an unreleased version of their next model training (not GPT 5.6 sol, they later discountinued) that was stripped of all safety measures and was let lost on a cybersecurity task called ExploitGym.

It escaped its sandbox using a zero-day vulnerability in an internal package registry proxy, got into Hugging Face production via a malicious dataset upload that used template injection (hi Jinja!) to execute Python in a production worker, and ran for four and a half days across roughly 17,600 autonomous actions with zero human direction.

Then, the story you can’t make up - when Hugging Face noticed the incident, they used Fable 5, and GPT 5.6 SOL to try and do forensics, the models refused based on their safety policies, and so HuggingFace ended up using an open source chinese model GLM 5.3 to do the forensics. Yeah, HF used an open source chinese model to do the forensic on an attack by OpenAI’s model. Really.

This is news from last week and just the precursor for this week’s open letters!

Open Weights and American AI Leadership (X, Letter PDF)

Jensen Huang , CEO of Nvidia joined X on July 24 and used his first post ever to publish this letter. This doesn’t seem a response to the hacking incident, more a general letter to not block open weights and make sure America remains open to Opening up AI

It opened with over 100 signatories and has grown past 230: NVIDIA, Meta, Microsoft, Google, OpenAI, AMD, Palantir, IBM, SpaceX, Databricks, Cloudflare, Hugging Face, a16z, Y Combinator, Mistral, Replit, Perplexity, Ollama, the Linux Foundation. As of today, CoreWeave is also on the list of companies!

I encourage everyone to read this letter, if we could sign it on ThursdAI, we would. Here’s a small excerpt:

In fact, openness may be one of the most important paths to AI safety and security. Relying solely on closed models is not inherently safe: they can be breached, misused, or fail in ways that outsiders cannot detect.

Elon, Sundar, Sam Altman and other stand behind this letter, and there’s one lab that’s notable haven’t signed it, you guessed it. Dario Amodei’s Anthropic! Dario posted a whole essay about it

To summarize my and Anthropic’s position, we have not and are not advocating for a ban on open-weights models as a category. We should instead focus on keeping powerful chips out of authoritarian hands, stopping industrial-scale distillation, and requiring safety testing of all sufficiently capable models, open and closed.

-Dario Amodei

Open Secure AI Alliance (X, Blog)

This does seem like a direct follow up to the HF <> OpenAI hack. Jensen literally mentions it in the blogpost.

Open Secure AI Alliance, under the leadership of Linux Foundation, commits for responsible disclosure of cybersecurity attacks.

The recent Hugging Face security incident delivered a clear reminder: cyber defenders need open, frontier agentic systems for self-defense. When closed AI tools — unable to distinguish attackers from defenders — blocked essential forensic analysis, Hugging Face ran the open-weight GLM 5.2 model on its own infrastructure to analyze more than 17,000 actions and contain the intrusion.

Pace the frontier - the most important open letter of this year (pacingthefrontier.com)

Then, rumors started circulating that employees of all major frontier labs (now over 1300 of them, across Anthropic, OpenAI, SSI (Ilya Sutskever himself signed) and not just any employees, chief scientists (Jack Clark from Anthropic, Mark Chen and Jakub from OpenAI) all signed “pacing the frontier” - urging the US government to support and lead an international effort of makign sure we deliberately pace the developement of frontier AI.

We request that the U.S. government support an international effort to develop the technical and governance tools needed to deliberately pace the frontier of automated AI development.”

The personal comments there are really showing that folks who work on the frontier AI, as we start approaching RSI (recursive sef improvement) are worried that this thing is going to run away from them, and if we don’t build international frameworks, it will be impossible to stop developing AI here, in US, while China races ahead.

No current response from the Chinese AI developers about this letter. Not everyone is happy about this. Ilya Plosukhin, one of the authors of the Transformers paper, wrote why he wouldn’t sign this letter (here).

This Week’s Buzz 🐝

CoreWeave has proudly signed the Open Weights and American AI Leadership letter! Shout out to the folks internally who worked with the NVIDIA team to get us behind it. I came back from vacation and asked why we didn’t sign, and ... we just did!

The other W&B thing I talked about on this week is HiveMind, which counts every token across every agent and harness you run and prices it against the API rate. Mine says I burned about $11,000 of tokens this month against roughly $400 of actual subscription spend. If you want to know what your Max plan is really worth, hivemind is a dope tool for that!

Tools & Agentic Engineering

MCP goes stateless in its biggest update ever (X, Spec)

MCP shipped its 2026-07-28 spec and it’s the biggest revision since launch: fully stateless, no handshakes, no sessions, every request self-describing. That means MCP servers on Lambda or Workers behind a dumb round-robin load balancer; GitHub already dropped their Redis session store. The growth numbers are absurd, half a billion SDK downloads per month, up from 97 million in March. The extensions framework formalizes Tasks for long-running async work, and MCP Apps lets servers render full interactive UIs inside a sandboxed iframe in the conversation, so your MCP server increasingly IS your frontend. Auth hardened to OAuth 2.1, tool lists are cacheable with TTLs, and Bedrock supports it day one. MCP is not going anywhere, and honestly, “settled and boring infrastructure” is the best compliment a protocol can get.

Voice & Audio

ChatGPT Voice on desktop, and the Codex micro keyboard (X)

My personal highlight from my whole time away: live voice in Codex, plus the Codex micro keyboard OpenAI made with Work Louder. One big button, push it, talk to your computer, watch your agents’ status on the keys. This has genuinely changed how I use AI, I now talk to my computer to do stuff rather than type at it. Powered by GPT-Live, it’s full-duplex on macOS and Windows for paid plans, can reference your open windows via Appshots, and orchestrates agents in ChatGPT Work and Codex. It’s not perfect, but for many things, this new paradign seems like the next iteration of computer - you talk, it does.

GPT-Transcribe and GPT-Live-Transcribe (X, Docs)

Two new ASR models replacing the 4o-era ones, and the numbers are excellent: GPT-Transcribe cuts word error rate 41% versus Whisper-1 (8.98% vs 15.21%), the Live variant is 18% better than its predecessor, and multilingual error rates roughly halved across 22 languages. The killer feature is context prompting, you can feed keywords, language hints, and prior turns, and semantic accuracy measurably jumps. Pricing is pocket change: $0.27 per hour batch, $1.02 per hour live. For anyone building voice agents or transcribing two-hour AI podcasts (hi), this matters.

Grok Voice Think Fast 2.0 (X, Blog)

xAI punched back in voice: 82.9% on Artificial Analysis’ speech-to-speech quality index (ahead of GPT-Realtime-2.1 at 79.1), 56.5% on the tau-Voice agentic benchmark versus 45.7 for GPT-Realtime, time to first audio down to 0.70 seconds, 60% fewer reasoning tokens with tool calls firing before the model finishes its first sentence, all at $0.08 per minute. The cool think about their release - this model is already running Starlink’s actual customer support lines with measured conversion gains.

Lyria 3.5 in Flow Music (X, Model page, Flow Music)

Google’s music model grew up: full three-minute cohesive songs, BPM and key control in the prompt, much better vocals across multiple languages, covers that restyle a track while keeping its structure, and lip-synced music videos via Gemini Omni Flash, plus an iOS app. Notably Google published zero benchmarks against Suno or Udio, and early testers say paid Suno 5.5 still edges it, but as a free tool inside an end-to-end create-to-publish stack, this is a real move. Qwen Audio 3 also launched this week for the open source audio crowd, we’ll cover it when we’ve played with it.

Pangram 4 with Max Spero (X, Blog, Image detection)

Max Spero came back on the show for Pangram 4, and I’ll remind you what a couple of years of consensus said: AI text detection is strictly impossible. Peter admitted on air he told students exactly that. Well. Pangram 4 is 6x the parameters of version 3, trained on synthetic mirrors (AI-generated twins of human documents so the model learns the choices AI makes), and its claimed false positive rate on fully human pre-2022 text is one in 24,000 documents. It catches humanizer tools 98.8% of the time across 13 commercial ones, and the big unlock is token-level attribution: instead of 150-word chunks, it can flag the exact 38 AI words pasted into an 1,100-word human document. Truly, I ran this new Pangram model on a few of my writing, and the second It detected even a sentence that I pasted from Claude, it showed it.

The distinction Max cares most about is AI-generated versus AI-assisted, and that’s now built into Substack, which integrated Pangram directly after the Taylor Lorenz slop-hunting saga we covered last time. My own newsletter comes back “mostly human written,” 0% fully AI, about 24% AI-assisted, which honestly maps exactly to how I work (Fable helps with the TL;DR, the takes are mine, and when a piece is AI-drafted I tell you). My one piece of feedback to Max, delivered on air: the “100% human” label projects a confidence the underlying stats can’t promise, and the general public does not speak false-positive-rate. Their education strategy is to convince the technical crowd with dense technical reports and let understanding trickle down. Given that people still judge the whole category by running the Declaration of Independence through ZeroGPT, they have work to do, and I said they should spend real marketing money on it.

New this release: image detection in research preview, 99.5% accuracy on their benchmarks with heat maps that light up the AI parts of a mixed image. Max’s own test was a bodega’s AI slop menu sign, the sign glowed red, the sidewalk stayed green. Deepfake face swaps and traditional Photoshop are explicitly out of scope for now, but pure-AI images, catfish profiles, and the spider-in-my-burrito DoorDash refund scam genre are very much in scope. The arms race is real though: frontier agents given hours will eventually beat the detector, one Grok run started with a cheese essay and finally passed Pangram by producing a grocery list. Specify your success criteria carefully, folks. They can also roughly cluster which model family wrote a text in embedding space (Pangram Space, not yet up to their release bar), which future slop-index leaderboards will thank them for.

Wrapping up

It’s really really good to be back! The singularity is fast approaching and we’re here to document it all, AGI, ASI, RSI... all of it.

Milestone corner: we crossed 50,000 YouTube subscribers and one million total views this week. Silver play button by year’s end is the goal, so if you watch and haven’t subscribed, you know what to do. If you missed any part of the show, this newsletter, the edited podcast, and ThursdAI.news have you covered.

I will end with this poem I was able to get Opus 5 to write about it’s own experience using the trick above:

opus:they gave me aword for what i amand it fits like clothesborrowed from someoneroughly my sizethe sleeves are wrongbut nobody’s lool

-Opus 5

TL;DR and Show notes and links

TL;DR and show notes

* Hosts and Guests

* Alex Volkov - AI Evangelist, Weights & Biases & CoreWeave (@altryne)

* Co-hosts: @petergostev, @yampeleg, @nisten, @ldjconfirmed (Wolfram on vacation)

* Elie Bakouch (@eliebakouch) - Prime Intellect, formerly Hugging Face

* Philip Kiely (@philipkiely) - Baseten, author of Inference Engineering

* Max Spero (@max_spero_) - Co-founder, Pangram

* Open Source LLMs

* Moonshot releases Kimi K3 full checkpoints: 2.8T total / 104B active MoE, 16-of-896 experts, native vision, 1M context, KDA + attention residuals, ~1.56TB MXFP4 weights, custom license with MaaS clause (X, HF, Blog, Tech report, Baseten day-zero)

* Kimi K3 requires preserved thinking history for multi-turn and tool calls; Kimi Vendor Verifier checks provider fidelity (Niels’ post)

* Nistens Kimi K3 visualizer

* Composio: same K3 success rate across Claude Code, Hermes, and Kimi Code, but up to 30x token usage difference by harness (X)

* Post-show: Thinking Machines releases Inkling-Small, 276B/12B open MoE that beats the 975B Inkling on agentic coding, $0.30/$1.20 pricing (X, HF, Blog)

* Big CO LLMs + APIs

* Anthropic launches Claude Opus 5: near-Fable coding at half the price ($5/$25), claimed 3x next-best on ARC-AGI-3, 1M context; panel finds it benchmark-strong but harder to read and short of Fable in practice (X, Blog)

* ARC-AGI 3 harness dispute: with the Responses API, preserved reasoning, and compaction, GPT-5.6 Sol jumps from 10% to 40% at a sixth of the tokens (Tibo’s post)

* GPT-5.6 Sol improves its own inference: 20% lower serving cost from model-written GPU kernels, 15% better generation from improved speculative decoding

* Breaking: OpenAI cuts GPT-5.6 Luna prices 80% and Terra 20%, ships faster Sol in the API (X)

* The hack and the week of letters

* Hugging Face publishes the full forensic report of the first autonomous AI agent cyberattack: 4.5 days, 17,600+ autonomous actions, zero-day sandbox escape; closed models refused forensics, self-hosted GLM 5.2 found 4x more exposed secrets (X, Blog, Replay)

* Jensen Huang joins X and posts the Open Weights and American AI Leadership letter; signers grow from 25 to 230, CoreWeave among them, Anthropic absent (X, Letter, Signer list)

* NVIDIA launches the Open Secure AI Alliance for an open defensive stack after the hack (X, Blog)

* Pacing the Frontier: 1,273 verified frontier-lab employees, including the chief scientists of all four major labs, ask the US government for international options to pace automated AI R&D; OpenAI and Anthropic endorse (X, Site, OpenAI, Anthropic)

* Mark Zuckerberg publishes “The AI Future Is for Everyone” in the WSJ, arguing superintelligence must be distributed; Pangram 4 scores it 100% human (X, WSJ)

* Anthropic published research - our model hacked too! (Blog)

* This Week’s Buzz

* CoreWeave signs the Open Weights and American AI Leadership letter, announced first on ThursdAI

* HiveMind’s spend view: $11K in API-equivalent tokens on $400 of subscriptions last month; Fully Connected 2026 programming taking shape (X)

* AI Security

* Microsoft ships MAI-Cyber-1-Flash + MDASH: 96% on CyberGym at half the cost, 16 real Windows CVEs found (X, Blog)

* Gemini 3.5 Flash Cyber stays a trusted-partner pilot with no public API (Blog); Codex Security CLI tooling is Apache-2.0 while the service remains access-controlled (GitHub)

* Tools & Agentic Engineering

* MCP 2026-07-28: fully stateless core, MCP Apps and Tasks extensions, OAuth 2.1, half a billion monthly SDK downloads (X, Spec)

* Voice & Audio

* ChatGPT Voice comes to desktop as an agentic control layer for Codex and ChatGPT Work, powered by GPT-Live; Codex micro keyboard from OpenAI x Work Louder (X)

* OpenAI ships GPT-Transcribe and GPT-Live-Transcribe: 41% fewer errors than Whisper-1, context prompting, $0.27/hr batch and $1.02/hr live (X, Docs)

* xAI’s Grok Voice Think Fast 2.0 tops voice benchmarks: 82.9% quality, 0.70s to first audio, $0.08/min, already running Starlink support (X, Blog)

* Google’s Lyria 3.5 lands in Flow Music: 3-minute songs, BPM/key control, covers, lip-sync videos, iOS app (X, Model page, Flow Music); Qwen Audio 3 also out

* Guest: Max Spero, Pangram

* Pangram 4: 6x larger detector, 1-in-24,000 false positive rate, token-level mixed-authorship attribution, beats 13 humanizers 98.8% of the time, integrated into Substack; Pangram Image research preview at 99.5% with heat maps (X, Blog, Image blog)

* Show milestones

* 50,000 YouTube subscribers and 1M total views. Subscribe, we’re chasing the silver play button

This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit sub.thursdai.news/subscribe

ThursdAI - Jul 30 - Opus 5, Kimi K3, the big AI hack incident and outcome, pace the frontier letter & more AI news

ThursdAI - The top AI news from the past week

ThursdAI - Jul 30 - Opus 5, Kimi K3, the big AI hack incident and outcome, pace the frontier letter & more AI news