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It's time to build.
Joined August 2009
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Introducing Cosign.
cosign.co
Excited to introduce @Cosign: the curated professional network for the startup community: cosign.co
Our goal is to create the following:
- A comprehensive startup directory of investors, companies, and operators, including what they worked on and who they worked on it with.
- Cosign graph: Who shaped your career? Who were you actually in the trenches with? Who would work with you again? Who thinks you’re someone to watch?
- Durable reputation: Great endorsements happen every day on X and disappear into the feed. Cosign attaches those signals permanently to people and companies.
- Discovery: Who are the best fintech angels? Which AI companies should I watch? Who are the best designers?
- Intent network: Privately signal “I’d invest in them,” “I’d hire them,” “I’d work with them,” or eventually even “I’d acquire this company.” Match people when interest exists on both sides.
Imagine if Wikipedia, LinkedIn, and OG AngelList had a baby. Though Cosign is a community, not a business.
In order to join, you need to be cosigned. Or you can apply directly.
David Booth and I started this idea 7 years ago but didn’t have the firepower to make it work. Now we do.
No one has really touched LinkedIn in 20 years. Excited to take a swing.
cosign.co
The future of security in the AI age is "the constant pressure of models attacking you," says Kevin Mandia of @ArmadinSecurity. That means seeing your network the way a swarm of AI attackers would:
"We do a thing called a hyperattack. We throw a drone swarm of agents at you, and we map your network. Every service, every route, every system, all assets. We may end up with terabytes of metadata on your network."
"This is the attacker's view of your network. But with that metadata, we now just poll you almost like a heartbeat."
"What's changed?... Did a route change? Did a service get updated? Did a new machine get presented into the target area? We can poll cheaply for change and then attack the change."
"You can't [attack yourself] all the time because it's cost prohibitive, and it's unnecessary. You do it when either the threat changes, new models come out, new intelligence is available, or your network changes."
"Over the weekend, there was a zero-day in a popular product, and immediately we've already got the heartbeat. We just polled who's got the problem."
"Our goal at Armadin is to go from a known vulnerability to knowing whether it's actually exploitable before the bad guys can."
The window to patch software bugs is collapsing
Of the bugs hackers actually exploit, ~87% are now being attacked on or before the day the bug is public knowledge
That share was 23% in 2020
Charts of the Week: a16z.news/p/chart-of-the-wee…
In the '90s, general-purpose chips wiped out the specialists. The original Thinking Machines, Cray Computer, and a wave of others shut down, and their best ideas got absorbed into other chips.
Zain Asgar of @gimletlabs argues the conditions that made generalists win have changed. Dennard scaling (shrinking transistors made chips faster at the same power) ended around 2005, transistor costs stopped falling around 2012, and memory bandwidth never kept up with compute.
Meanwhile, token demand is projected to grow 24x by 2030 while available power grows about 2x. When power is the bottleneck, performance per watt wins, and that's where specialized chips shine.
Full piece from Zain on why "the time of specialization is upon us": a16z.news/p/why-hardware-spe…
Adit Abraham of @reductoai on why everything in AI is "state-of-the-art all the time," and how to find what actually works for you:
"One of the unfortunate things about the AI industry... is benchmarks have become marketing over time."
"There's a public benchmark out there that we tested where if you take the same documents and you add a little bit of noise, like you tilt it one degree, you add a little Gaussian blur, the provider that published the benchmark gets way, way worse than everyone else, but everyone else is kind of consistent."
"Our recommendation is actually LLM as a judge is quite strong today if you're thoughtful about how you think about a rubric and how to approach it."
"We want to see the industry move closer to people testing on their own data, with tools maybe to make that evaluation easier."
"Instead of trusting a generic benchmark, you really should be at a point where you know what works best for you."
@aditabrm
AI agents can reason over enormous amounts of information, but much of the world's actual work is still trapped in PDFs, spreadsheets, scans, and other formats that models struggle to reliably understand.
Reducto co-founder and CEO Adit Abraham argues that solving this document layer is essential if agents are going to take on consequential work in healthcare, legal, finance, and insurance.
Adit joins a16z General Partner Jennifer Li to explain why traditional OCR breaks down on messy real-world documents, how Reducto combines vision-language models with specialized infrastructure to reach high accuracy without sacrificing cost or latency, and why frontier models can silently drop information on long extraction tasks.
Reducto now processes billions of pages each month, and crossed its 7 billionth page the morning of this recording.
0:00 Why AI agents need to read PDFs
2:12 From 1990s OCR to vision models
5:00 Training R1 on the messiest docs
7:46 When agents beat humans at extraction
9:45 A penny a page for 7 billion pages
12:47 Why legal and finance lag coding AI
15:01 The stakes of AI errors in healthcare
16:25 Agents that can edit Word and Excel
17:58 Why the labs won't go deep on PDFs
20:14 Frontier models silently drop data
22:21 Benchmarks have become marketing
25:45 Why charts and Excel stump models
28:46 Infra for 10M documents at once
31:03 How "chet pain" gets claims denied
34:32 The paperwork AI should kill first
YouTube: youtu.be/xuczlbVVLsQ
@aditabrm @reductoai @JenniferHli
a16z retweeted
We formally announced Mirendil less than 4 months ago. Today, I'm excited to share an important milestone for:
Pretraining at scale without a pretraining team.
Mirendil's mission is to solve Recursive Self-Improvement (RSI) and use it to democratize frontier AI development, ultimately accelerating science and technology. At Mirendil, when we think about RSI, we think holistically about the company as an intelligent entity that self-improves toward its goal. From that perspective, the most powerful notion of acceleration is reducing the time and resources (number of human experts, compute, and other costs) needed to achieve ambitious goals.
Given that pretraining is perhaps the most important yet most challenging part of frontier AI development, we decided to run an ambitious controlled experiment: Starting fully from scratch, can we significantly reduce the time, number of human experts, and compute resources needed to go all the way to successfully pretraining a strong coding model at scale?
Mirendil-Base is the result of this experiment. Our first pretrained model was built by one researcher in 3.5 months, with less than $10M in compute. This includes all the research and small-scale experiments it took to get there, as well as the final training run.
The recipe holds up as the models get bigger. For reference, Mirendil-Base is in the 100B-500B parameter range, Mirendil-Base-Large in the 500B-2T range, and Mirendil-Base-XL in the 2T-10T range.
We're beginning to see a world where a single researcher, empowered by AI, can take on work that once required an entire research organization. As these systems improve, the bottleneck shifts from the size of a team to the ambition and judgment of the people directing them. This has profound implications for who gets to build AI and, ultimately, who gets to push the frontiers of science and technology forward.
We’ll share independent evaluations, post-training benchmarks and API-access sooner than you think so stay tuned!
Introducing the Cosign Awards.
cosign.co/awards
Excited to announce the Cosign Awards: celebrating exceptional people, companies, and products that had a massive impact in 2026.
cosign.co/awards
Anyone can nominate and vote. Award winners will be chosen by the public in conjunction with a panel of judges, including industry leaders like @lennysan, @packyM, @amasad, and many more. We’ll host an event in December honoring the winners (10 per category).
For people categories, we’re mostly focused on everyone except the CEO–everyone else building the company behind the scenes.
Companies with the most amount of people nominations will be listed on our “Top Companies to Work For” page.
True to form, at Product Hunt I helped launch the Golden Kitty awards a decade ago to recognize great products. Soon after I launched the Rise Awards, honoring executives and ICs building companies that make them. The Cosign Awards is the next iteration.
We have 41 categories across people, companies, and products.
People categories:
- Future Founders
- Rising Stars
- Engineering
- FDE
- Product
- Design
- AI Researchers
- Marketing
- Comms
- Growth
- Chief of Staff
- Operations
- Talent
- Finance
- Public Intellectuals
- Podcaster of the Year
- Newsletter Author of the Year
- Poster of the Year
Company categories:
- Rising Stars
- Best Place to Work
- Founder Mafia
- Talent Density
- Highest Aura
Product categories:
- Product of the Year
- Launch of the Year
- AI Assistant
- AI Language Model
- AI Coding
- Dev Tools
- Open Source
- Consumer
- Productivity
- Creative & Media Tools
- Product Design & UX
- Enterprise B2B
- Hardware
- Robotics
- Self-Driving
- Healthcare
- Vertical Fintech
- Legal
AI agents can reason over enormous amounts of information, but much of the world's actual work is still trapped in PDFs, spreadsheets, scans, and other formats that models struggle to reliably understand.
Reducto co-founder and CEO Adit Abraham argues that solving this document layer is essential if agents are going to take on consequential work in healthcare, legal, finance, and insurance.
Adit joins a16z General Partner Jennifer Li to explain why traditional OCR breaks down on messy real-world documents, how Reducto combines vision-language models with specialized infrastructure to reach high accuracy without sacrificing cost or latency, and why frontier models can silently drop information on long extraction tasks.
Reducto now processes billions of pages each month, and crossed its 7 billionth page the morning of this recording.
0:00 Why AI agents need to read PDFs
2:12 From 1990s OCR to vision models
5:00 Training R1 on the messiest docs
7:46 When agents beat humans at extraction
9:45 A penny a page for 7 billion pages
12:47 Why legal and finance lag coding AI
15:01 The stakes of AI errors in healthcare
16:25 Agents that can edit Word and Excel
17:58 Why the labs won't go deep on PDFs
20:14 Frontier models silently drop data
22:21 Benchmarks have become marketing
25:45 Why charts and Excel stump models
28:46 Infra for 10M documents at once
31:03 How "chet pain" gets claims denied
34:32 The paperwork AI should kill first
YouTube: youtu.be/xuczlbVVLsQ
@aditabrm @reductoai @JenniferHli
Eugenia Kuyda, founder of @wabi, on why chatbots are the MS-DOS era of AI, and why a new interface is necessary to make AI's full potential obvious to everyone:
"It always struck me as strange that people were using products like ChatGPT, Gemini, or Claude, but mostly for very simple use cases: for search, or to help them write something, help with homework."
"No one was really mentioning any of these exciting capabilities that we just kept seeing the models get, and so we felt like there must be an interface problem."
"There should be something simple for everyone, me included, to actually discover these amazing use cases that all these models already have."
"We got obsessed with this metaphor that the current chatbots are really the Microsoft DOS era for AI interfaces. And that there will be some sort of a Windows/MacOS moment."
"There is so much traction with chatbots... In order to unlock something else, you need a more exciting interface."
@ekuyda
Ekin Dogus Cubuk of @periodiclabs on why AI has to learn from the physical world, and building their own lab to close that loop:
"One of the more fundamental ways of making things around us is powder synthesis... You can actually, using that method, discover new superconductors, magnets, all kinds of materials that are very important for technologies around us."
"But at the core of it is just quantum mechanics. And we feel like teaching these LLMs quantum mechanics will be the next frontier for LLMs."
"Science is by its nature iterative, right? Like even the smartest humans tried many times before they discovered the things they discovered. LLMs can be very smart, but if they're not iterating on science, they won't discover science."
"The important thing to teach these LLMs is the method of scientific inquiry. So you do simulations, you do theoretical calculations, you do experiments, you get results, and the results are probably incorrect or not what you wanted at first, but you iterate on it."
"You have to do it with the real physics, not just the simulation."
@ekindogus @AnjneyMidha
a16z's Christian Keil makes the case for why building, testing, and iterating in the physical world is the bottleneck for AI in hardware: a16z.news/p/superhuman-hardw…
AI models are getting close to designing hardware better than humans, and that shifts where the hard problems are:
- Better simulation, so physical builds become confirmation instead of experiments
- Demand shifts toward parts, machining and raw materials
- AI labs need to capture the "process knowledge" that lives in machinists and fabs
The one step even superhuman AI will struggle to speed up:
"A superhuman hardware engineer could design one million new iterations of the Apple Watch and get them manufactured for cheap, but then how can it know what customers actually want?"
But once AI crosses over, "the impact should prove immense: humanity will be able to directly use digital AI tools to bring about real, physical, material abundance."
Full piece from a16z's Christian Keil on what hardware engineering looks like once AI masters design: a16z.news/p/superhuman-hardw…
"It took me three months to design it, but it's nine months until I can actually start to use it."
Former Intel CEO Pat Gelsinger on the manufacturing bottleneck between designing hardware with AI and actually getting it built:
"Let's say we're off to do a great new chip together, the one that's gonna leap ahead because we have understanding of the AI workloads... And let's say we turn our AI tools loose. Within three months we have an awesome design."
"[But] we still have like a couple of really major bottlenecks today. One is we still have nine months of silicon processing time... So I can design the thing in three months, but I can't actually get it into real silicon at scale for nine months."
"We have to really see that bottleneck improve if we're gonna have this innovation."
"If it takes me a year and a half until I actually get scale and software on it, my understanding of the AI workloads is no longer applicable to the chip that I designed."
"All of those aspects somewhat obviate the fact that AI has made the design piece easy. All of those manufacturing scale issues to me become a huge bottleneck."
@PGelsinger @appenz @RaghuRaghuram
a16z's Christian Keil makes the case for why manufacturing, testing and iteration are the next frontier for AI in hardware: a16z.news/p/superhuman-hardw…
a16z retweeted
More background on how this happened and why Silicon Valley is so magical:
-I had the privilege of working with Jean-Denis (@jgreze) at Plaid for many years
-After running in the SF Marathon in 2024, I "ran" into him at In-N-Out in Daly City and we talked about what he was doing next...
-SMB tax...!
-Meanwhile, my partner Justine Moore (@venturetwins) was off trying every single consumer and enterprise productivity agent...and Town had pivoted
-She concluded Town was the best, which caused @bhorowitz to start using Town
-I then re-heard of Town and was like...the SMB Tax tool? :)
-I reached back out to Jean-Denis and told him about his mega fan and suggested having dinner with Ben and me
This also shows why venture is a team sport. This investment would have never happened without Justine, and probably without Ben as well! And maybe without the SF Marathon! And likely not without Plaid / @zachperret!
Jean-Denis Greze was CTO of Plaid. His next startup, an AI tax product for small businesses, brought in nearly $1M in revenue its first year, and he projected $2.5 to $3M the next. He shut it down anyway.
The reason: in the age of AI, it was never going to be venture scale. Incumbents could use the same technology to automate tax prep for their existing customers faster than a startup could win market share. Tax is also sold once a year, so he had about a one-month window to pivot before the door closed.
The pivot became Town, an AI assistant that works from your email and calendar. It found product-market fit fast enough that Ben Horowitz messaged a16z's Alex Rampell to say it "changed my life."
In this conversation, Alex and Jean-Denis cover:
- How to know when to kill a business that's working on paper
- Why Town competes with OpenAI and Anthropic, the companies it buys its tokens from
- Why the "forward deployed engineer" model gets worse as AI gets better
- How a $1/month AI routine can save a restaurant thousands
- What agents mean for Amazon, advertising and the future of shopping
0:57 How Ben Horowitz discovered Town
2:20 Why Town started with AI tax prep
3:55 Why tax couldn't be venture scale
6:30 Shutting down a working business
10:24 The customer ask that became Town
13:35 Why Town built for users before IT
16:18 AI's iPhone moment at work
21:28 Jevons paradox for executive assistants
23:13 Town as a "token allocation machine"
28:00 How Town tailors itself to each job
34:03 Competing with your token suppliers
42:24 Staying off the AI labs' radar
44:42 Why AI isn't spreading evenly yet
52:32 How agents break the ad model
55:35 The friction humans actually enjoy
57:05 Why supply aggregators lose to agents
YouTube: youtu.be/o_5f4N6Nq80
@jgreze @TownAI @arampell
a16z retweeted
It's time for personal agents in healthcare.
Our system is fragmented and runs on clunky legacy software. That's exactly why agents that can navigate those systems on our behalf could make such an impact.
Karan, who leads health AI at OpenAI, calls it "absolutely ripe for agents and computer use" and thinks many of the barriers between patients, clinicians, and their data will dissolve. I agree.
Super inspiring convo with my friend @thekaransinghal on how AI can raise both the floor and the ceiling of human health.
More than 300 million people use ChatGPT for health and wellness questions each week. OpenAI’s Karan Singhal thinks that’s only the beginning.
Karan joins a16z's Jay Rughani to explain how OpenAI is building health intelligence, the advantages of using generalized models for health applications, how AI could lower the cost of healthcare, and more.
00:00 Intro
01:00 How OpenAI is building health intelligence
07:57 A doctor in your pocket
14:20 Creating trust with users
19:44 Medical consensus and its 5–17 year lag
28:03 AI for mental health
30:59 How AI enables the healthcare ecosystem
38:21 A "move 37" for health
43:39 Driving down the cost of care
50:27 Procedural care and what's next
YouTube: youtu.be/9n0MI4D7TCM
@thekaransinghal @JayRughani
For AI to become a superhuman hardware engineer, it has to learn from the physical world, and real-world data is hard to get:
- It's non-uniform and constantly changing
- It's sparse: you can't measure everything all the time
- It's expensive to collect
- Physical processes take time, and can only be sped up so far
- Some of it is qualitative: do users actually like the product?
"Data limitations like these are massive drivers in the spikiness of AI capability development today. The more quantifiable and machine-readable the results of a test, the faster the models can climb the hill."
Full piece from a16z's Christian Keil on why the physical world is so hard for AI to learn from: a16z.news/p/superhuman-hardw…
NEW: INVESTOR ADVICE FOR APPLYING TO SPEEDRUN (SR008 EDITION)
Every cohort we sit down with our investors to hear what’s top of mind. This time @ndrewlee got in the booth with @kenanhsaleh, @emilybenn12, @seeamshahidnoor, and @tkexpress11 to talk about:
00:00 - what’s changed in apps this cycle
04:15 - team vs. market vs. traction: how we weigh them
08:14 - hot markets vs. ones that feel inevitable
10:36 - spotting the gaps the frontier models leave
13:35 - where speedrun fits in your founder journey
22:26 - how to make your application stand out
30:05 - common mistakes (AI is not your “why now”)
38:46 - the 10-min interview + co-founder dynamics
45:41 - what you get working with speedrun
SR008 apps close Nov 1. Watch the full roundtable here 👇
Karan Singhal of @OpenAI on the collapsing cost of intelligence, as seen on their health benchmark:
"GPT-6 Luna is our current cheapest frontier model on the API... It performed better than 5.6 Sol, which was literally our best model a month ago. And it performs better despite being 34x cheaper."
Most tiers of model intelligence became more than 100x cheaper within roughly a year
One tier went from ~$32 to ~$0.02 per million tokens in two years
More than 300 million people use ChatGPT for health and wellness questions each week. OpenAI’s Karan Singhal thinks that’s only the beginning.
Karan joins a16z's Jay Rughani to explain how OpenAI is building health intelligence, the advantages of using generalized models for health applications, how AI could lower the cost of healthcare, and more.
00:00 Intro
01:00 How OpenAI is building health intelligence
07:57 A doctor in your pocket
14:20 Creating trust with users
19:44 Medical consensus and its 5–17 year lag
28:03 AI for mental health
30:59 How AI enables the healthcare ecosystem
38:21 A "move 37" for health
43:39 Driving down the cost of care
50:27 Procedural care and what's next
YouTube: youtu.be/9n0MI4D7TCM
@thekaransinghal @JayRughani
AI is on track to become a superhuman hardware designer, but design is only the beginning. The interface between bits and atoms is lossy, and turning designs into real hardware gets harder at every level:
1. Sourcing off-the-shelf parts that work together (a 2006 Falcon 1 engine test was delayed by one capacitor, in stock 6,000 miles away)
2. Custom parts, where a master machinist translates CAD into machine instructions
3. Assemblies, where every part can meet its drawing and still not fit
4. Outside vendors (even SpaceX has 591 employees with supply chain titles)
5. Doing all of it at a scale of 1,000,000
"Superhuman AI might be great at pure design, meaning at defining the platonically ideal part for a particular job, but struggle with 'design for manufacturing,' or finding a point design that meets the requirements while remaining easy to build/procure and inexpensive."
Full piece from a16z's Christian Keil on what it takes to turn AI-designed hardware into the real thing: a16z.news/p/superhuman-hardw…
Five bangers from OpenAI's Karan Singhal:
1. Raising the floor and the ceiling of human health:
"There's more than 300 million people weekly using ChatGPT for health and wellness types of questions, and we take that as an incredibly important responsibility to get that right."
"We're really invested in making sure basically two things. One is that we can raise the floor of human health and give people access to trustworthy, abundant, reliable health intelligence for free or nearly free, and really raise the ceiling as well and make things possible that weren't possible before."
2. Five physicians, eight answers:
"It turns out if you ask five physicians any question, you'll get, like, eight different answers. One of the first things that we did when we first started focusing on health at OpenAI was really build this kind of global physician network of hundreds of experts."
"[The goal was] to kind of aggregate the wisdom of experts so that we weren't relying, especially in areas where there could be disagreement, on one or two or three physicians to kind of adjudicate."
3. Why health runs on a general model rather than a specialized model:
"What we're talking about here is actually specialized training in a general model, which is, I think, actually the best of both worlds."
"If you forked and said, 'Hey, we're gonna train a smaller specialized model that is just for healthcare'... what you'd find is that model would fall behind the frontier relatively quickly, because the pace of the frontier and the general model improvements is so fast."
4. Compressing medicine's 5 to 17-year lag:
"How long does it take for clinical guidelines to penetrate the practice of everyday doctors across the world? People have found that this takes, depending on the study, 5 to 17 years... You don't wanna be practicing medicine 5 to 17 years behind."
"One of the things that we think about is how do you compress that kind of period of practicing down to weeks or days or even hours."
5. Healthcare's legacy software is ripe for agents:
"Healthcare is also one of those industries where you shouldn't expect everything to have an MCP connector tomorrow. It is a place where there's legacy software... This is absolutely ripe for agents and computer use."
"This is a place where a lot of the barriers that have traditionally existed between patients and getting the care they need and clinicians and delivering the care they need and healthcare data in general... I think a lot of those will dissolve."
@thekaransinghal
More than 300 million people use ChatGPT for health and wellness questions each week. OpenAI’s Karan Singhal thinks that’s only the beginning.
Karan joins a16z's Jay Rughani to explain how OpenAI is building health intelligence, the advantages of using generalized models for health applications, how AI could lower the cost of healthcare, and more.
00:00 Intro
01:00 How OpenAI is building health intelligence
07:57 A doctor in your pocket
14:20 Creating trust with users
19:44 Medical consensus and its 5–17 year lag
28:03 AI for mental health
30:59 How AI enables the healthcare ecosystem
38:21 A "move 37" for health
43:39 Driving down the cost of care
50:27 Procedural care and what's next
YouTube: youtu.be/9n0MI4D7TCM
@thekaransinghal @JayRughani
If you ask five physicians a question, you might get eight different answers. Karan Singhal of @OpenAI on how OpenAI decides what its models should say about health:
"One of the first things that we did when we first started focusing on health at OpenAI was really build this kind of global physician network of hundreds of experts that we work with."
"Across the globe, across dozens of specialties and languages and countries of practice, to think about the right ways to aggregate the wisdom of experts so that we weren't relying, especially in areas where there could be disagreement, on one or two or three physicians to kind of adjudicate."
"Let's say the aggregated wisdom of the physicians is pointing in one direction, and then maybe the user actually wants you to say something comforting even when the situation's not comforting. There it's basically a prioritization of safety."
"It's very important to us that we take our obligation very seriously when there's hundreds of millions of health conversations coming in."
"We have evaluations that track these kind of difficult situations... Over time, we've not only improved how we've done that evaluation working with physicians, but also seen pretty dramatic model improvements across the board."
@thekaransinghal @JayRughani
More than 300 million people use ChatGPT for health and wellness questions each week. OpenAI’s Karan Singhal thinks that’s only the beginning.
Karan joins a16z's Jay Rughani to explain how OpenAI is building health intelligence, the advantages of using generalized models for health applications, how AI could lower the cost of healthcare, and more.
00:00 Intro
01:00 How OpenAI is building health intelligence
07:57 A doctor in your pocket
14:20 Creating trust with users
19:44 Medical consensus and its 5–17 year lag
28:03 AI for mental health
30:59 How AI enables the healthcare ecosystem
38:21 A "move 37" for health
43:39 Driving down the cost of care
50:27 Procedural care and what's next
YouTube: youtu.be/9n0MI4D7TCM
@thekaransinghal @JayRughani
















