Simon Lu

It’s time to share what we’ve been quietly building for the past two years: @firstharmonic First Harmonic is a new kind of program for early-stage founders. Since 2023, we’ve worked closely with nearly 50 teams across 6 cohorts on one of the most critical challenges in the early days of company building: defining a precise go-to-market strategy. Our belief is simple: Great GTM begins with focus. Every major decision—roadmap priorities, customer acquisition strategy, sales model, pricing—flows from who your customer is. Most early-stage companies go too broad, too soon. This is a common mistake and leads to building your startup in hard mode. During our eight-week program, we apply an intensive 1:1 method to help teams go narrow and come out with both clarity about who their ideal customer is and what the right GTM motion is to execute downstream of that. The founder feedback has validated our core beliefs about early-stage GTM. Founders tell us the program has been transformative, and we’ve maintained an NPS of ~100 across every cohort. Our cohorts are small—about 10 companies each—and there’s no application. Instead, we work with a select group of founders nominated by people we trust, often alumni of the program. To keep the program free and founder-friendly, we raised an early-stage fund that covers the costs of running the program. But there are no investment expectations or strings attached to participating. We named our firm First Harmonic because the first harmonic represents a foundational principle in any system. As the base frequency from which all other harmonics derive, it symbolizes the starting point of a journey—something every early-stage founder can relate to. If you're an early-stage investor, let’s find ways to collaborate. If you're a founder, you can read more about our method (link in comments).

I could not be more excited to announce that @amirmova has joined the team @firstharmonic. Amir and I have known each other for 15 years. He was one of the best hires I made in my five years at Twitter. Amir made a huge impact, including helping to lead the company’s IPO efforts in 2014. A few years later, he became the CFO at Mixpanel and then the COO, leading the GTM organization and owning the sales number. I knew Amir to be an extraordinary operating executive, but did not expect him to become a CEO as quickly as he did. But that’s exactly what happened when Mixpanel's founder stepped down in 2017 and asked Amir to take over. Mixpanel was once the market leader in product analytics, but had lost its lead. As CEO, Amir led an amazing turnaround in the company’s performance. He remained CEO for eight years before recruiting his replacement and stepping down earlier this year, with Mixpanel growing, thriving, and profitable. Amir is a builder. He is a winner. He cares deeply about his work and the people he works with. His breadth of experience at both private and public companies is remarkable, and I believe he will become a tremendous resource to First Harmonic’s founders through all stages of their journey. Welcome to the team, Amir. I’m delighted to work with you again.

Introducing @PoeticHQ: a new AI system that executes complex multi-hour tasks with 99%+ accuracy and 10x fewer tokens than agents. We raised $50M at $500M from Kleiner Perkins, Founders Fund, First Harmonic, and Genius Ventures to build AI that does complex work inside Fortune 500 companies without hallucination. While code is too brittle, agents are too unpredictable. The work that runs the global economy - anti-money laundering, fraud investigations, underwriting - needs extreme accuracy. So we built a new kind of software that pairs the flexibility of AI with the predictability of code. When the world stays the same, Poetic runs fixed code: fast, cheap, identical every time. When the world changes, Poetic uses AI to regenerate its approach and find its way back to the objective. In one year, we went from zero to an eight-figure run rate as a team of four. Since then, we’ve scaled the team and executed the highest-stakes processes at AIG, SoFi, and Chime. At SoFi, a large US bank, Poetic reached 99%+ quality on fraud investigations in five weeks.

We hosted a Builders Table event with leaders from @AnthropicAI last week. It was amazing to hear about their experiences using Mythos internally, managing the unprecedented growth they are seeing, and learning about new products they are hoping to build. Thanks so much to the @AnthropicAI team (@bcherny, @mikeyk, @alistaiir, @OmidMogasemi, @jwbaskerv, and especially @RazRazcle), and to the great engineers who spent their evening with us.

📣 We just raised our $45M Series B from @TCVTech and @firstharmonic, with participation from @BainCapVC, @firstround, and @AlkeonCapital. Sales is the most expensive function in most companies — and one of the hardest. Hundreds of accounts, different context, different stakeholders, different dynamics, and a different path to close. No one can do that perfectly. Critical things get missed. So we gave every account its own AI agent — working 24/7, maintaining full context, progressing it through the funnel, and guiding reps and leaders on what to do next. The greatest privilege has been building alongside companies like @Samsara @tryramp @ironclad_inc and @attentiveHQ — enterprises with thousands of sellers who are already living in the future. There are only two unbounded upside problems out there: building and selling. Every company sells. and @useactively is building the system they'll all run on. We’re excited to pull every revenue team into the future we know is inevitable.

Last week, we brought together 30 of SF’s top engineers for our Builders Table event with @cursor_ai. The way we build software is evolving quickly, and Cursor is helping lead that shift. The group dove into questions like: - Does the future of coding live in the IDE, the CLI, or somewhere entirely new? - How will the role of an engineer change over time? There are plenty of spaces for founders to connect and learn from one another, but there are far fewer spaces for engineers. We loved creating one and are excited to do more. If you're an engineer interested in joining a future @firstharmonic event, please feel free to DM me.

We hosted 30 of SF’s best engineers at our Builders Table event with @cursor_ai last week. The way we code is changing fast, and Cursor is one of the companies at the forefront. The team shared their perspectives on questions like: - Will engineers even look at their code in a year? - Will the future of coding be in the IDE, the CLI, or in something else entirely? - What will the role of an engineer look like in the future? There are many forums for founders to learn from each other, but fewer for engineers. We loved creating one and hope to do more. If you’re an engineer and interested in attending a future @firstharmonic event, DM me!

Excited to announce that @simpleailab has raised a $14M seed round led by @firstharmonic. For the past year, we’ve been building AI voice agents to transform direct-to-consumer sales. We fundamentally believe that voice AI is the future of all B2C calls.

Excited to announce our $11M Series A, led by @ROWGHANI from @firstharmonic. Our AI agents automate and strengthen compliance workflows for financial institutions, including @Chime , @BiltRewards , & @CelticBank. Thanks to our customers, team, & investors :)

I love the description of Pixar as a miracle factory. How do you create the conditions to make special outcomes more likely? @ROWGHANI helped build Pixar, working closely with Steve Jobs and Ed Catmull in their golden era. He also worked closely with the Twitter founders and then Sam at YC. He’s advised some of the best founders through his work at YC Continuity and now his own fund First Harmonic. I love talking to Ali and always learn something new. Hope you enjoy.

Today we're announcing that Eventual has raised $30M in Seed and Series A funding from @CRV and @felicis as well as @ycombinator, @M12vc and @Citi and others. The AI era needs data infrastructure built for AI, not retrofitted. 🧵

👋 Sharing a great opportunity for anyone out there who loves to read, write, and learn. We're hiring a part-time writer at @firstharmonic to produce a series of research essays on topics that early-stage founders care about. Probably two pieces per month, each about 1,000–2,000 words, month-to-month contract. Maybe you're an engineer but want to stimulate your brain in a different way. Maybe you work in banking or consulting and are VC-curious. Maybe you're still in school. If you enjoy thinking about businesses and you appreciate good clear prose, it'll be a great time. Email me if you're interested or know someone who might be! (mia@)

Learn more about how we think here: thoughts.firstharmonic.com/choose-your-cu…

It’s time to share what we’ve been quietly building for the past two years: @firstharmonic First Harmonic is a new kind of program for early-stage founders. Since 2023, we’ve worked closely with nearly 50 teams across 6 cohorts on one of the most critical challenges in the early days of company building: defining a precise go-to-market strategy. Our belief is simple: Great GTM begins with focus. Every major decision—roadmap priorities, customer acquisition strategy, sales model, pricing—flows from who your customer is. Most early-stage companies go too broad, too soon. This is a common mistake and leads to building your startup in hard mode. During our eight-week program, we apply an intensive 1:1 method to help teams go narrow and come out with both clarity about who their ideal customer is and what the right GTM motion is to execute downstream of that. The founder feedback has validated our core beliefs about early-stage GTM. Founders tell us the program has been transformative, and we’ve maintained an NPS of ~100 across every cohort. Our cohorts are small—about 10 companies each—and there’s no application. Instead, we work with a select group of founders nominated by people we trust, often alumni of the program. To keep the program free and founder-friendly, we raised an early-stage fund that covers the costs of running the program. But there are no investment expectations or strings attached to participating. We named our firm First Harmonic because the first harmonic represents a foundational principle in any system. As the base frequency from which all other harmonics derive, it symbolizes the starting point of a journey—something every early-stage founder can relate to. If you're an early-stage investor, let’s find ways to collaborate. If you're a founder, you can read more about our method (link in comments).

Mito just launched on Product Hunt! We'd love to hear your feedback on our new AI suite! producthunt.com/posts/mito-ai

🚀 Introducing Daft: A High-Performance Distributed Dataframe Library for Multimodal Data 📊🔥 blog.getdaft.io/p/introducing-… 🧵 1/5

Congrats to the team at Redbird on the round! Redbird (YC W22) is building an analytics operating system for the enterprise - empowering anyone within an organization to easily automate and unify their analytics work in minutes, without writing code: techcrunch.com/2022/10/13/ana…

Congratulations @sytses, @dzaporozhets, and the entire @gitlab (YC W15) team on today’s IPO! Beyond building an enormously successful business, they have broken the mold of how startups themselves are built. Read about GitLab's story from YC to IPO 👇🏽 blog.ycombinator.com/gitlab-from-yc…

The biggest news in Fivetran's history: we're bringing together the two best companies in the data pipeline business. fivetran.com/blog/hvr-acqui…

👋We're hiring our first Research Associate at @YCombinator Continuity. This is an amazing role for somebody who loves data & startups to help us evaluate investment opportunities, lead market research & advise portfolio companies. Apply here & DMs open! jobs.ashbyhq.com/ycombinator/8a…

YC's legal and software teams, and YC Continuity are hiring -- come work with us! blog.ycombinator.com/come-work-at-y…