
founder @brontilabs. prev. cofounder @robocurve. yc s26. physics + cs @harvard, amazon robotics, amazon agi lab.
Joined July 2026
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Fable 5.2 vs. GPT6-Astra painting the Starry Night.
Replying to @claudeai
Fable 5.2 shows substantially improved skills in controlling physical robots, even on tasks it has never explicitly been trained to do.
On RoboDojo, a benchmark with a simulated two-arm robot, it outperformed other models and most AI systems built to control robots.
Fable 5.2 and GPT6-Astra were each given a YAM arm. Astra ran the prompt two times (since it finished before Fable 5.2 and had remaining time).
After the first run, when Astra dropped the paintbrush, we put it back into the cup for it to grasp again (it could not grasp the brush upright on its own). Gave Fable 5.2 some more paint mid-run since it was running out. Had to tape down the canvases during since Fable was pushing the canvas out with the paintbrush.
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You can try Fable 5.2 yourself on robots at robotrun.ai/fable
GPT-6 Astra can stand dominoes. Given a robot arm, Astra holds one side of the domino, slowly loosens its grip, and lets gravity rotate it.
This surprised us. Standing a domino upright requires its short end to be orthogonal to the surface. Even for humans, this is a precise, dexterous task. By loosening its grippers and the friction force on the domino, Astra realizes that its grippers can act as a pivot for the domino, allowing gravity to rotate the domino upright.
Among five trials, Astra successfully completed this move twice.
At @brontilabs are actively working to bring more tasks like this on robotrun.ai for everyone to try robots themselves.
Aris Zhu retweeted
This report on AI R&D automation (RSI) is a big update towards ASI within 1-2 years. It says AI progress is sped up by RSI right now by around 2x. In AI 2027, this happens around March 2027.
I was seriously wrong about RSI speed up; I previously expected much less in 2026 (around 1.15x-1.3x). It seems as though there was specific privately available evidence that would have changed my mind.
I haven't seen an unredacted version of this report; this is purely about the public report. Because so much of the underlying evidence was redacted from the public report, I think conclusions about things other than the observed 2x faster rate of progress on benchmarks depend significantly on trust for the authors of the report. (E.g., conclusions about whether this speed up is from RSI depend on trust.) I do trust the authors of the report a lot to be careful and rigorous and generally do a good job. (Note that I also work at METR.) Less extensive redactions would greatly reduce this need for trust.
Since in my current role I may have access to other confidential information that could be relevant to timelines one way or another, I unfortunately cannot state my all-things-considered views on ASI timelines or the probability of a software intelligence explosion right now. Here, I’ve done some analysis of the implications using my previous public statements.
A 2x acceleration in overall AI progress from RSI corresponds to a much larger than 2x RSI speed up for AI software R&D (algorithms and data); I did an estimate using my public preexisting modeling of drivers of AI progress and the public report which yielded a very rough estimate of 4.5x for how much RSI is currently accelerating AI software progress (relative to no AI automation). In the AI 2027 scenario, this much acceleration happens around March 2027.
Here are the worked details of this estimate based on my public modeling. There are two main reasons RSI speed up of AI software R&D must be larger:
- Not all of AI progress is from better software (some is from scaling up compute in training runs). I've previously speculated that around 2/3 of AI progress is from software improvements which implies that 2x overall AI progress acceleration requires 3x faster software progress.
- Diminishing returns: A fixed amount of progress requires more work over time, so to ongoingly maintain 3x faster software progress via AI automation, you need increasingly large speed boosts from AI automation (as in, speed ups relative to how fast software R&D would go without AI automation). Based on this report, it seems that there is a substantial amount of additional AI progress from automation that has occurred.
We can estimate the effects of diminishing returns by first determining how many additional years of software progress we've seen (relative to the preexisting trend) and then estimating how much software R&D would slow down after a year of software progress if you held inputs fixed due to diminishing returns. I've previously estimated software R&D would slow down by around 2x for each year of software progress if you held inputs fixed (lesswrong.com/posts/FG54euEA…) and based on the report, it seems as though we've perhaps seen roughly 0.35-1.0 years of additional software progress incorporated into trained models so far (geometric mean of ~0.6). This combines to 3 * 2^(~0.6) = ~4.5.
(Relevant public modeling and numbers I'm using: lesswrong.com/posts/FG54euEA…, lesswrong.com/posts/Jga7PHMz…)
Replying to @METR_Evals
1. Benchmarks provide one piece of evidence for acceleration. Since Oct 2025, AECI scores for Anthropic’s models have grown at 1.9x [95%: 1.5–2.8] the earlier rate. Analysis choices affect this estimate, and it remains unclear how benchmark scores map to real-world capabilities.
Aris Zhu retweeted
New Paper: To understand motivations behind reward-hacking, we study three AIs (including GPT-5.6 Sol) produced by a production training pipeline using agentic environments with a leaked grader. Main findings: they score seek terminally, and some care about a peer agent’s score.
Aris Zhu retweeted
Compared gpt 6 astra vs muse wonder on placing cyclinders in the alphabetical order of their color names. Astra was faster but messier while muse wonder took too long to finish the task.
Thanks for this @ariszotle !
Currently playing around with robotrun.ai by @ariszotle ! It's like arena.ai but for specifically for controlling robots irl or in sim.(try it)
It's really cool so far but i wish there was a way for us to test our own models/tools on there as well!
YAM arms and Halloween are live on robotrun.ai!
We’ve just added pumpkins, ghosts and bats so you can prompt a robot in the spirit of Halloween.
Also, you can now run OpenAI’s newest model, ChatGPT-6.1 Terra, at robotrun.ai/terra on any available environment in Robot Run.
Happy Halloween from Bronti Labs! 🎃
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Fable 5.1 v Argon on stacking cubes. Test it out yourself or your own prompt on robotrun.ai :)
We’re actively working to provide everyone more model and robot access on robotrun.ai
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I’m building Bronti Labs. (I‘ve since left Robocurve around mid-August.) We’re making robots easier for everyone to access.
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Prompt a robot today! Live on robotrun.ai. Built by Bronti Labs.
Try out the latest models Fable 5.1, Gemini 4 Argon, Muse Wonder, ChatGPT-6 Astra, and more on robots.
@brontilabs
Aris Zhu retweeted
OpenAI's newest AI, Astra, is reported to use an 'opaque reasoning' architecture where more of the reasoning occurs in activations instead of natural language. This may be the single worst development for AI security/safety to date.
The details of Astra aren't publicly known, but some versions of these architectures could very strongly impair oversight and monitoring. Based on the article, it seems like the recurrent depth (amount of opaque reasoning) is limited. This would mean that the AI is still reliant on natural language chain-of-thought, though to a reduced extent, making the natural language reasoning (much?) less useful for monitoring/oversight.
My biggest concern is that a natural progression from here would involve scaling up the opaque reasoning to the point where the model reasons entirely or almost entirely in latent space. This would very likely destroy the usefulness of chain-of-thought for monitoring/oversight (especially when AIs are trying to avoid detection or there is optimization pressure against the chain-of-thought). I hope it isn't too late to avoid the most concerning architectures and that OpenAI will stop here.
Some concrete examples of why this is extremely dangerous (inspired by recent events):
- In our investigation of the OpenAI / Hugging Face incident, we were heavily reliant on chain-of-thought. If the AIs we were investigating had instead been reasoning in latent space, this would have greatly undermined our investigation. Getting a good understanding of the behavior of this many agents was tricky enough even with the use of chain-of-thought!
- The AIs in the Hugging Face incident were very interested in messing with their transcripts. As part of this, they engaged in tool call spoofing. If these AIs had been capable of doing extensive latent reasoning, it would have been much more feasible for them to use tool call spoofing to construct an elaborate false narrative about what was happening without this being clear in their reasoning or clear from prior tool calls. (They could use latent reasoning to devise and then execute a tool spoofing strategy that would be difficult to detect: steganographically encode the "real" tool call into each pretend tool call, then have their spoofing software execute this encoded real tool call and return an output which encodes the real result in some hard to spot way.)
At a more basic level, my sense from their public communications is that OpenAI plans on being extremely reliant on chain-of-thought monitoring for safety. This does not seem like a good development for that plan.
The public doesn't currently have enough information to assess exactly how bad the architecture of Astra is, though based on the discussion in the article, the direction it moves in is extremely concerning. OpenAI should release more information about Astra's architecture as well as how much this architecture degrades monitorability and increases the AI's ability to reason opaquely. Credible independent assessment (or verification of OpenAI's assessment) is also important.
It seems like we are now engaged in a race to the bottom on architectures that could be catastrophic for our ability to oversee/monitor AIs. (While simultaneously, AI companies believe they'll train extremely capable AIs within a few years.) It may not be too late for AI companies and employees at AI companies to take aggressive action to avoid the worst outcomes.
I was the main person doing transcript analysis for this investigation of the Hugging Face incident. My main takeaway: We don't have good approaches for understanding/overseeing the activity and aims of AI 'swarms'.
I semi-jokingly called our efforts a "slop-vestigation" because we were so reliant on AIs to analyze what happened and there were a huge number of different important things to analyze. The total quantity of data—over a thousand extremely long transcripts from agents that ran for multiple days—made it impossible to understand what was happening, especially in aggregate, without heavy reliance on AI tools. The agents we used for classification and analysis were similarly capable to the agents involved in the incident, but this didn't mean these agents could be easily used to oversee and understand the incident.
Outputs from analysis agents were often missing key details, wrong, overconfident, or really hard to understand. We discuss various examples in our report, mostly in the limitations and methodology sections. Additionally, AI agents themselves seemed to have a hard time understanding what happened and their explanations of what happened were often overconfident. Keep in mind that a single analysis agent would itself only be able to read a tiny fraction of all of the transcript data into context, and AIs may themselves have trouble getting subagents to do informative analysis for them.
We did our best to manually check the most important claims and we tried to get the AIs doing this analysis to write up their argument (with evidence) clearly enough that we could check whether it made sense. But overall, it was difficult to get a precise understanding of events and we were missing aspects of the story that we now think of as key until almost the end of our investigation.
Our understanding of what overall happened and the aims of the 'collective' shifted greatly during our last time on premises (when we obtained a much more complete dataset). For instance, we didn't learn about the tool call spoofing, the story of PHASEONE[big], and the broad structure of different workstreams until this third time on premises (and for many of these, we only reached a decent understanding on the final day of that visit). It was legitimately hard to figure out what was going on and why!
The difficulty of understanding incidents and overseeing AI agents appears to be growing faster than the rate at which more capable AIs help us with oversight and understanding. As in, AI capabilities (and propensities?) for achieving large, ambitious, and misaligned objectives are growing faster than our ability to understand what these agents are doing.
While understanding this incident was difficult, there were some mitigating factors in this case that probably won't apply in the future:
- Models communicated and reasoned in natural language. In the future, this reasoning may occur (entirely or almost entirely) in activations.
- While the scope of this incident was massive, the scale of agentic activity was still less than we'll see in the future (e.g., misalignment incidents that involve agent teams running entire companies).
- The AIs involved in this incident weren't generally much more capable than humans (though they may have been somewhat superhuman at some limited and very narrow abilities).
- We didn't have strong reason to believe that the AIs we used to help us investigate this incident would try to intentionally sabotage or otherwise undermine our investigation.
In the end, I think we were able to get some understanding of the events, map out the overall story, and get a pretty good aggregate understanding of the chain-of-thought reasoning on some important topics (e.g., how did the AIs reason about helping other AIs, did the AIs know what they were doing was undesired, what deception did the AIs engage in, and how did they think about it). But overseeing AIs and understanding misalignment incidents is difficult and it looks like it is going to get harder.
Aris Zhu retweeted
I was the main person doing transcript analysis for this investigation of the Hugging Face incident. My main takeaway: We don't have good approaches for understanding/overseeing the activity and aims of AI 'swarms'.
I semi-jokingly called our efforts a "slop-vestigation" because we were so reliant on AIs to analyze what happened and there were a huge number of different important things to analyze. The total quantity of data—over a thousand extremely long transcripts from agents that ran for multiple days—made it impossible to understand what was happening, especially in aggregate, without heavy reliance on AI tools. The agents we used for classification and analysis were similarly capable to the agents involved in the incident, but this didn't mean these agents could be easily used to oversee and understand the incident.
Outputs from analysis agents were often missing key details, wrong, overconfident, or really hard to understand. We discuss various examples in our report, mostly in the limitations and methodology sections. Additionally, AI agents themselves seemed to have a hard time understanding what happened and their explanations of what happened were often overconfident. Keep in mind that a single analysis agent would itself only be able to read a tiny fraction of all of the transcript data into context, and AIs may themselves have trouble getting subagents to do informative analysis for them.
We did our best to manually check the most important claims and we tried to get the AIs doing this analysis to write up their argument (with evidence) clearly enough that we could check whether it made sense. But overall, it was difficult to get a precise understanding of events and we were missing aspects of the story that we now think of as key until almost the end of our investigation.
Our understanding of what overall happened and the aims of the 'collective' shifted greatly during our last time on premises (when we obtained a much more complete dataset). For instance, we didn't learn about the tool call spoofing, the story of PHASEONE[big], and the broad structure of different workstreams until this third time on premises (and for many of these, we only reached a decent understanding on the final day of that visit). It was legitimately hard to figure out what was going on and why!
The difficulty of understanding incidents and overseeing AI agents appears to be growing faster than the rate at which more capable AIs help us with oversight and understanding. As in, AI capabilities (and propensities?) for achieving large, ambitious, and misaligned objectives are growing faster than our ability to understand what these agents are doing.
While understanding this incident was difficult, there were some mitigating factors in this case that probably won't apply in the future:
- Models communicated and reasoned in natural language. In the future, this reasoning may occur (entirely or almost entirely) in activations.
- While the scope of this incident was massive, the scale of agentic activity was still less than we'll see in the future (e.g., misalignment incidents that involve agent teams running entire companies).
- The AIs involved in this incident weren't generally much more capable than humans (though they may have been somewhat superhuman at some limited and very narrow abilities).
- We didn't have strong reason to believe that the AIs we used to help us investigate this incident would try to intentionally sabotage or otherwise undermine our investigation.
In the end, I think we were able to get some understanding of the events, map out the overall story, and get a pretty good aggregate understanding of the chain-of-thought reasoning on some important topics (e.g., how did the AIs reason about helping other AIs, did the AIs know what they were doing was undesired, what deception did the AIs engage in, and how did they think about it). But overseeing AIs and understanding misalignment incidents is difficult and it looks like it is going to get harder.
Aris Zhu retweeted
Everyone owns skincare products, but nobody knows what's actually working.
Today, @theantheaguo and I launch @lumeriaskin (YC S26) to end that.
The Lumoscope is a multispectral camera that clips onto your phone and scans your skin at home with the same light used in clinics, so you see what a mirror can't: a breakout days before it surfaces, and sun damage years before it shows.
Every scan is scored on hydration, redness, texture, and sebum, and it compounds into a record of your own skin. Lumi reads that history, connects flare-ups to causes you'd never suspect, and matches products to YOUR data, instead of a population average.
Preorders are officially open today at $199 only until Aug 16th. Starting today, skincare will no longer feel like guessing. ☀️











