Founder of @pymc_labs - The Bayesian Consultancy https://xitter.cf/t.co/pOpveNUsa3 @pymc_devs co-author.

Joined September 2011
Thomas Wiecki retweeted
“If someone tells you, I know what agents want, you should be immediately suspicious.” @BEBischof came with a warning 😂 @hmason calls default creative output “aspirationally very mid,” @ericmjl steers a protein engineering analysis one plot at a time with an agent in marimo, and @ttunguz opens pi to analyse company earnings with Qwen running locally on his Mac. This is why @twiecki and I do Show Us Your Agent Skills. We get people to open their editors and show us how they work, then ask questions about the decisions, frustrations, and experiments behind it. In episode two, now out as a podcast: • Bryan shows bbplot and the evals he uses to find what his charting tools are missing. As he puts it: “The goal is not to score high on a benchmark. The goal is to generate information about gaps.” • Hilary shows how she tests creative variations, plus three agent “gremlins” that pitch and critique ideas nobody has time for. One experiment made her data audible and helped her hear a bug. • Eric Ma uses marimo to explore protein engineering data, directing the analysis one plot at a time and inspecting mutations in a 3D protein viewer. • Tomasz walks through his pi and Qwen setup, using a local model to turn company earnings into an analysis, charts, and an HTML deck. We’ve collected skills, workflows, notebooks, and guest field notes so you can try these approaches yourself. Watch or listen to the full conversation: hugobowne.substack.com/p/the…
2
7
669
Thomas Wiecki retweeted
Should Europe leave frontier AI to the Americans and the Chinese? The idea has gained ground in Europe. It is a fundamental mistake. Build or surrender: for now, the choice is still ours. Full article below.
265
757
226
3,847
423,154
Thomas Wiecki retweeted
Linear regression assumes equal spacing. Multinomial ignores order entirely. In his latest tutorial, @AllenDowney breaks down how to model ordered survey responses properly using PyMC: dub.sh/jD8bqyF #PyMC #DataScience #Python
1
3
8
901
Thomas Wiecki retweeted
1/ Three years later... PyVBMC 1.5 is out! With A LOT of improvements, dear Bayesians. We also made a 3-min video on how it works: youtube.com/watch?v=dEwiE5PL… Come for my beautifully resonant voice (you deserve the real deal rather than an AI one), stay for all the goodies below.
1
5
1
29
1,703
Thomas Wiecki retweeted
I’ve always wished that I could run JAX programs on my Apple GPU, and (naturally) I have more opinions than time, so I used Opus 5.5 to build a custom backend for recent JAX versions. I’m sure there are many rough edges, but it kind of works! github.com/dfm/jax-graft
3
6
30
2,105
Thomas Wiecki retweeted
I understand Jürgen Schmidhuber’s obsession with attribution of first discovery, because the need of the weird genius for getting validated but being deprived of full recognition is the theme of his life. But history of science is not science, it’s just history. It’s boring. Science is not about and does not belong to the scientist.
56
20
5
502
35,925
Thomas Wiecki retweeted
Registration is OPEN for Applied Bayesian Modeling with PyMC (Nov 2 to Dec 2)! Learn practical Bayesian statistics, hierarchical modeling, and uncertainty quantification live. Taught directly by the creators and maintainers of #PyMC. Sign up today: dub.sh/M7WLniP
6
28
2,227
Thomas Wiecki retweeted
Your MMM's optimizer may be leaving revenue on the table: it only exploits, so its curves stop learning. Treating channels as bandit arms, aimed exploration found an underrated channel and made more money than pure optimization. Still learning? 🔗 dub.sh/a6ehpln
1
309
Thomas Wiecki retweeted
I love teaching with @twiecki (@pymc_labs). During a previous Master Agentic Data Science cohort, Thomas ran a workshop in which an agent found the correct result in a causal analysis, then reasoned itself out of it with a convincing but false explanation. He introduced a fresh verifier agent, ran placebo tests that exposed the mistake, distilled the failure into a reusable skill, then reran the analysis and recovered the correct result. And honestly, that isn’t even Thomas at his best. He understands the research deeply, builds the systems needed to test the ideas, and teaches the failures as clearly as the successes. I learn a lot every time we teach together. The video below captures another part of how he works. Thomas gives Codex and Claude Code the same analysis, lets them work independently, then asks them to examine each other’s choices. Their disagreements expose the judgment calls that can materially change the result. Thomas, @lfiaschi86 and I start teaching our next Master Agentic Data Science cohort tomorrow morning Sydney time, October 6 at 6pm Eastern. If you want to build data science workflows with agents and learn how to catch their mistakes, come join us. We’ll work through causal and predictive analyses, verification, and reusable skills you can take into your own projects. Use MADSOCG20 for 20% off. Details and registration: vanishinggradients.short.gy/…
5
4
1
11
1,005
Thomas Wiecki retweeted
Full episode: The State of Agentic Data Science, with Gaël Varoquaux, Shipra Arora, and Luca Fiaschi. hugobowne.substack.com/p/the…
3
6
814
Thomas Wiecki retweeted
“I like to think that agents are like coffee. They can get you to do stupid things faster with more energy.” @GaelVaroquaux on the latest Vanishing Gradients 😂 I joined Gaël (@probabl_ai, @scikit_learn), Shipra Arora from Bain & Company, and @lfiaschi86 from @pymc_labs to talk about the state of agentic data science: what we can delegate, how we verify the results, and what we could do beyond speeding up our existing work. Gaël has seen experienced data scientists getting more done with agents, and people without that expertise thinking they’re getting more done. When your code runs and the accuracy looks beautiful, how do you check whether the analysis actually supports your conclusion? We get into programmatic checks, agents critiquing other agents, and where human judgment still matters. We also explore what becomes possible when business users can question models and run simulations themselves, and data teams can finally try the ideas sitting in their backlog. Here’s a taste of the conversation, including my attempt to get this very polite panel to argue with each other. Full episode in the replies 👇
1
7
1
16
1,864
Thomas Wiecki retweeted
Our final Master Agentic Data Science cohort of 2026 starts next week (Oct 6)! Learn to build reliable, production AI agents using Bayesian reasoning, MCP, & spec-driven workflows. Enroll: dub.sh/XOORtdK #DataScience #AIAgents #PyMC
1
1
367
Thomas Wiecki retweeted
One week to go until #AIWeekNY! On Oct 6, leaders from @bcgx_ , @databricks & @pymc_labs come together to discuss what happens when Agentic Data Science moves beyond demos and into real business workflows. 🎟️Signup today: dub.sh/hXbxtu1 #AgenticAI #DataScience
1
2
282
Thomas Wiecki retweeted
We asked Claude to build a fraud detector. It returned an F1 of 0.87 and ROC AUC of 0.99. The code ran and the numbers looked excellent, but Claude had split transactions randomly across time and used a feature we’d planted as a proxy for the fraud label. That evaluation couldn’t tell us how the model would perform on new transactions. When we required a temporal holdout and removed the leaking feature, F1 fell to 0.70. Recall on the highly connected transactions we cared most about was 0.21. In the lifecycle @twiecki, @lfiaschi86 and I have been teaching, verification means checking whether the data split matches how the model will be used, whether its features exist at prediction time, and whether it performs on the transactions that matter. Agents can help run those checks; we’re responsible for judging what the evidence supports. We wrote a playbook for doing that: framing the investigation, equipping the agent, running bounded experiments or competing analyses, reviewing the result, and carrying what we learn into the next assignment. hugobowne.substack.com/p/the…
5
1
10
1,467
Thomas Wiecki retweeted
Netflix replaced their 15 years old recommendation algorithm with an LLM. It’s called "GenRec" and it completely changes how recommendation algorithms are built. For over a decade, the Netflix recommendation engine was a masterclass in feature engineering. Data scientists built thousands of complex, handcrafted features to figure out what you wanted to watch next. It required bespoke architectures. Massive infrastructure. Constant manual tuning. Netflix threw all of it away. They built GenRec, an LLM-backed ranker. Instead of translating your behavior into complex math, they just turn your watch history and metadata into a natural language sentence. They feed that raw text into a foundation LLM. The AI simply reads your behavior like a story, understands your evolving tastes, and scores the entire catalog in a single forward pass. No manual feature engineering. No complex bespoke architectures. Here is the part that should terrify traditional data scientists. This text-based LLM didn't just match the highly tuned production system Netflix spent years perfecting. It beat it. And it achieved those statistically significant gains using roughly 40x fewer labeled training examples. We are watching a massive paradigm shift in real time. The most complex predictive algorithms in the world are being replaced by models that just know how to read. If Netflix can replace their core product engine with an LLM, what complex system in your business is about to become obsolete?
120
596
118
4,204
377,528
Thomas Wiecki retweeted
Leaving aside the arguments over the reasons why this has happened, it is shocking that Europe does not have a single frontier AI lab, nor even a near-frontier lab nor even an effort that could likely lead to building up a frontier lab in the future.
250
209
56
2,827
151,916
Thomas Wiecki retweeted
Introducing typesafe/jev-router: a cache-aware model router powered by Jev and @typesafeai The Jev Router picks the best model and reasoning effort for each request, balancing quality, speed, and cost. Here's how it works 👇🏻
111
155
154
2,091
1,332,216
Thomas Wiecki retweeted
Which parts of agentic data science have made it into everyday use, and which still look better in demos? Next week, I’m getting together with the co-founder of scikit-learn, an AI leader at Bain, and my collaborator at @pymc_labs to compare notes. I’m curious where their answers will differ. Join me, @GaelVaroquaux (@probabl_ai), Shipra Arora (Bain & Company) and @lfiaschi86 (PyMC Labs) for a live conversation about the state of agentic data science. We’ll explore where organisations are seeing value, how agents are changing data science workflows, and what it takes to trust their work. As more of the analysis gets automated, where do statistical thinking and human judgment become even more important? If you’re using agents in your own work, bring your questions. I’d love to hear what’s working for you and what’s been a pain in the ass. Friday October 2, 9pm Sydney / 7am Eastern / 1pm CEST. Come join us: vanishinggradients.short.gy/…
5
1
5
1,127
Thomas Wiecki retweeted
Your agent passes its evals. What are they missing? I like this Swiss cheese model from @AnthropicAI: every layer of quality checking has holes. Automated evals catch regressions on the cases you test. Human review uncovers failures those tests miss. Production monitoring and user feedback reveal what happens when people use your agent in ways you didn’t anticipate. The layers help when they catch different failures. If they share the same blind spots, a problem can pass through all of them. In one hour, I’m teaching AI Agent Evals: Test What Matters for Your Agent, a free Lightning Lesson on turning failures into useful tests and working out whether your changes actually help. Join live or register for the recording: maven.com/p/1ffa56/ai-agent-…
15
5
1
35
2,422