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Charles Foster

@cfoster.bsky.social
873 followers 156 following 58 posts

Twitter: @CFGeek Mastodon: @cfoster0@sigmoid.social When I choose to speak, I speak for myself. 🪄 Tensor-enjoyer 🧪

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Charles Foster @cfoster.bsky.social · 16/09/2026
I won’t speak on behalf of METR, but I’ll say personally: none of the work that we've done so far passes my bar for an "audit" of an AI company or its systems, was definitely not "regulation" in any meaningful sense (whether bank examiner-like or otherwise), and shouldn’t substitute for actual laws.
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METR @metr.org · 24/02/2026
Since early 2025, we've been studying how AI tools impact productivity among developers. Previously, we found a 20% slowdown. That finding is now outdated. Speedups now seem likely, but changes in developer behavior make our new results unreliable. We’re working to address this.
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METR @metr.org · 10/07/2025
We ran a randomized controlled trial to see how much AI coding tools speed up experienced open-source developers. The results surprised us: Developers thought they were 20% faster with AI tools, but they were actually 19% slower when they had access to AI than when they didn't.
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Charles Foster @cfoster.bsky.social · 07/03/2025
Update for those who’ve left the other app: I’m now on the policy team at Model Evaluation and Threat Research (METR). Excited to be “doing AI policy” full-time.
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Charles Foster @cfoster.bsky.social · 26/02/2025
Why aren’t our AI evaluations better? AFAICT a key reason is that the incentives around them are kinda bad. In a new post, I explain how the standardized testing industry works and write about lessons it may have for the AI evals ecosystem. open.substack.com/pub/contextw...
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Charles Foster @cfoster.bsky.social · 11/01/2025
When we optimize automation, we sometimes optimize *hard*. Like this automated loom working away at an inhuman 1200 RPM. Wild. youtu.be/WweMNDqDYhc?...
youtu.be
TOYOTA AIR JET LOOMS JAT 810 JA4S-190 CM RUNNING AT 1200 RPM
YouTube video by TEMAC INDIA
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Charles Foster @cfoster.bsky.social · 22/12/2024
Is there a website/database out there that tracks what major AI company executives say about the future of AI?
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Charles Foster @cfoster.bsky.social · 18/12/2024
Transformers and other parallel sequence models like Mamba are in TC⁰. That implies they can't internally map (state₁, action₁ ... actionₙ) → stateₙ₊₁ But they can map (state₁, action₁, state₂, action₂ ... stateₙ, actionₙ) → stateₙ₊₁ Just reformulate the task!
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Charles Foster @cfoster.bsky.social · 10/12/2024
Atticus Geiger gave a take on when sparse autoencoder (SAEs) are/aren’t what you should use. I basically agree with his recommendations. youtube.com/clip/UgkxKWI...
youtube.com
YouTube
Share your videos with friends, family, and the world
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Charles Foster @cfoster.bsky.social · 10/12/2024
These days, flow-based models are typically defined via (neural) differential equations, requiring numerical integration or simulation-free alternatives during training. This paper revisits autoregressive flows, using Transformer layers to define the sequence of flow transformations directly.
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Charles Foster @cfoster.bsky.social · 04/12/2024
Re: instruction-tuning and RLHF as “lobotomy” I’m interested in experiments that look into how much finetuning can “roll back” a post-trained model to its base model perplexity on the original distribution. Has anyone seen an experiment like this run?
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Charles Foster @cfoster.bsky.social · 01/12/2024
I’ve been wondering when it would make sense for “AI agent” services to offer money-back guarantees. Wrote a short post about this on a flight. open.substack.com/pub/contextw...
open.substack.com
“Provider pays” for failed automation services
If your AI works as well as you claim, why not make that a promise?
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Charles Foster @cfoster.bsky.social · 30/11/2024
Neat thing about real-money prediction markets is that you can get paid for doing this.
xkcd comic 386, with back and forth that goes:

“Are you going to bed?”
“I can’t. This is important.”
“What?”
“Someone is WRONG on the internet.”

https://xkcd.com/386/
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Charles Foster @cfoster.bsky.social · 28/11/2024
A bit of clever mechanism design: prediction markets + randomized auditing. If you have 100 verifiable claims you want information on but can only afford to check 10, fund markets on each. Later, use a randomized ordering of them to check the first 10. Resolve those to yes/no, refund the rest.
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Charles Foster @cfoster.bsky.social · 27/11/2024
Still gathering my thoughts on @TheCurveConf, but for now, a short reflection on why I like “the curve” as a way of thinking about the future of AI. (1/6)
Logo for The Curve Conference. Link to website: https://thecurve.is
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Charles Foster @cfoster.bsky.social · 26/11/2024
RT-ed and endorsed
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Charles Foster @cfoster.bsky.social · 25/11/2024
CLAIM: In areas where we can’t measure what (we claim) we want & where we won’t change our minds about that, we’ll struggle to make AI systems that give us better—rather than merely cheaper, faster, more consistent—outputs. But I think that’ll really pressure us to revise our wants.
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Charles Foster @cfoster.bsky.social · 21/11/2024
Timothy B. Lee here gives a good short list of what human attributes might still have value (at least temporarily) in a hypothetical world where AI systems are capable of acting as “remote worker substitutes”. open.substack.com/pub/understa...
open.substack.com
Seven big advantages human workers have over AI
Geoffrey Hinton says "there's nothing special about people." He's wrong.
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Charles Foster @cfoster.bsky.social · 21/11/2024
For those of us that rely on earned income, a key concern about the future is “Will automation soon put me out of work?” But at the moment, we can’t do much about it. Would you pay 1% of your earnings per year to protect a year’s worth of future earnings if most jobs are suddenly automated away?
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Charles Foster @cfoster.bsky.social · 20/11/2024
Whenever faced with a hard problem, some AI folks say “I know, I’ll use reinforcement learning.” Now, they have two hard problems.
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Charles Foster @cfoster.bsky.social · 17/11/2024
Using Bluesky to reboot your character arc for the LLMs
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Grace @gracekind.net · 15/11/2024
A human bioactuator inspects the entire factory and turns a single screw, fixing the problem. The next day, he bills the company $10,000. “$10,000? My AI could’ve figured out the problem in an instant!” The bioactuator relied: “It’s $1 for knowing which screw to turn, and $9,999 for turning it”
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Charles Foster @cfoster.bsky.social · 13/11/2024
“I had worked hard for nearly two years, for the sole purpose of infusing life into an inanimate body. For this I had deprived myself of rest and health […] but now that I had finished, the beauty of the dream vanished, and breathless horror and disgust filled my heart.” - M. Shelley in Frankenstein
Professor Geoffrey Hinton, photo from a NYT article. Link: https://www.nytimes.com/2023/05/01/technology/ai-google-chatbot-engineer-quits-hinton.html
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Charles Foster @cfoster.bsky.social · 12/11/2024
Let us not mistake how we want the world to be for how it is.
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Ted Underwood @tedunderwood.com · 01/11/2023
A letter about the critical role of open-source models in ensuring that AI doesn’t produce an unsafe concentration of power. Led by Mozilla and signed by leaders in academia, MistralAI, EleutherAI, &c.
open.mozilla.org
Joint Statement on AI Safety and Openness
We are at a critical juncture in AI governance. To mitigate current and future harms from AI systems, we need to embrace openness, transparency, and broad access.
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Charles Foster @cfoster.bsky.social · 04/07/2023
We'll soon forget the butterflies we first felt when software talked.
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