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Varun Mohan (co-founder and CEO)20 April 2025

Building a magical AI code editor used by over 1 million developers in four months: The untold story of Windsurf

6Frameworks
14Insights

Frameworks in this episode

Insights & moments

The myth-busts, hot takes, explainers, and tools worth keeping.

Hot Take· 6

Hot Take08:30

Why Value in AI Accrues at the Application Layer, Not Infrastructure

Varun explains that their original bet on heterogeneous model architectures collapsed once everything converged on the transformer by mid-2023, invalidating the infrastructure thesis. He argues the application layer is the deep place to differentiate because there is effectively no ceiling on how much better developer workflows and UX can get.

  • The first thing a founder believes they should work on is unlikely to be the right thing.
  • They initially assumed many model architectures (CNNs, RNNs, LSTMs) would need an abstraction layer.
  • By mid-2023 everything looked like a transformer, so the infrastructure-value hypothesis was wrong.
  • Value accrues at the application layer, where there is effectively no ceiling on improving developer workflows.

It's very unlikely the first thing that you believe you should go work on uh is going to be the right thing which is like…

Varun Mohan · 08:30
#ai-strategy#value-capture#startups
Hot Take21:30

Agency Is the Most Undervalued Skill in the AI Era

Beyond problem-solving and systems knowledge, Varun singles out agency as the skill society and schooling most undervalue. School gives people well-defined paths and tells them exactly what to do; startups instead need people who want to build something without being told, and Windsurf explicitly screens for high agency.

  • School conditions people to follow well-defined paths and do exactly what they're told.
  • Agency, the drive to build something without instruction, is undervalued in the last decade.
  • Windsurf explicitly hires for high agency because a startup dies if it doesn't innovate.
  • Most large-company software engineering interviews don't select for agency.

we look for people that are really high agency because we just recognize that by default if we don't innovate and do crazy things, we're…

Varun Mohan · 22:00
#hiring#skills#agency#career
Hot Take23:00

The 'Dehydrated Company': Only Hire When You're Underwater

Varun explains their hiring philosophy: only hire for a function when the team is genuinely underwater, because adding people you don't need creates politics as they manufacture low-value work to justify themselves. He wants the company to stay 'dehydrated,' with each hire a little water added only when people are raising their hands saying they're drowning.

  • The goal is to be the smallest company that can satisfy their ambitions, not lean for its own sake.
  • Only hire for a role when that function is actually underwater.
  • Unneeded hires manufacture unimportant work and lobby the org that it matters, creating politics.
  • Staying understaffed is a forcing function for ruthless prioritization.

I wanted the company to almost be like this dehydrated entity right and every hire is is like a little bit of water, right? And…

Varun Mohan · 25:30
#hiring#org-design#startups
Hot Take31:00

'I Work Smart' Is a Hiring Dog Whistle

Varun says when he asks candidates how hard they're willing to work and they answer that they 'work smart,' it's a red flag. In a company that already has many smart people who also work hard, someone who only works smart will pull the team down, since a company is a massive group project where the cost of a coasting teammate is felt by everyone around them.

  • Windsurf tells candidates up front it's a very competitive, hard-working environment, not a chill one.
  • Answering 'I work smart' when asked how hard you'll work is a dog whistle.
  • The real cost of a coasting person is the signal it sends to teammates about the internal bar.
  • If four of five teammates don't care, the fifth stops caring too.

one of the biggest dog whistles I sort of hear is when I ask people like how hard are you willing to work? Some people…

Varun Mohan · 31:30
#hiring#culture#work-ethic
Hot Take50:30

Verticalized Niche Software Will Get Competed Down

Varun predicts that highly verticalized niche products, like sales, legal, or finance software, will be competed down because domain specialists can now build the exact tools they want. Those vertical vendors historically survived by bundling a kitchen sink of features when each customer only needed 10%, and companies couldn't build or maintain their own; that constraint has now disappeared.

  • Very verticalized niche products (sales, legal, finance) are most at risk of being competed down.
  • Vertical vendors won because customers couldn't build or maintain custom software for their needed 10% of features.
  • Domain specialists can now build the tools they always wanted in minutes, often more customized.
  • Off-the-shelf software often frustrates buyers with missing integrations; custom builds fix that.

these very very verticalized niche products I think are going to get they're going to get competed down a ton.

Varun Mohan · 51:00

the domain specialists now have access to build the tools that they ultimately wanted

Varun Mohan · 52:00
#software-industry#ai-disruption#saas
Hot Take1:06:30

Cannibalize Your Own Product Every 6 to 12 Months

Varun's most counterintuitive lesson is the tension between visible short-term wins and the longer, riskier bets that actually determine survival. He tells the company they should cannibalize their own product every 6-12 months so it makes the existing version look silly, warning that being first with the agentic IDE will depreciate quickly unless they keep re-proving themselves in ways users aren't even asking for.

  • The company works on 3-9 month bets internally even as the public celebrates weekly incremental wins.
  • The goal: cannibalize the existing product every 6-12 months so it looks silly by comparison.
  • Being first with the agentic IDE depreciates fast without continuous reinvention.
  • Incremental feature requests feel safe but are table stakes, not why they'll win.
  • You still can't ignore users, since they're the reason you exist.

we should be cannibalizing the existing state of our product every 6 to 12 months. Every 6 to 12 months it should make our existing…

Varun Mohan · 1:07:00
#product-strategy#innovation#roadmap

Explainer· 2

Explainer17:30

How Engineering Changes When AI Writes 90% of the Code

Varun breaks an engineer's work into three buckets: what to solve, how to solve it, and solving it. He argues AI will handle nearly all of the 'solving it,' and increasingly the 'how' as codebase understanding improves, pushing engineers toward the highest-value work of choosing which business problems and capabilities actually matter.

  • Engineering work splits into: what to solve, how to solve it, and solving it.
  • AI will handle the vast majority, if not all, of 'solving it.'
  • Deep codebase and organizational understanding will let AI increasingly handle 'how to solve it' too.
  • Engineering shifts toward prioritizing the most important business problems and technical decisions.

what should I solve for how should I solve it and then solving it

Varun Mohan · 17:30
#future-of-work#engineering#ai
Explainer1:04:00

Why 90% AI-Written Code Means Hiring More Engineers, Not Fewer

Varun uses Amdahl's law to explain why AI writing 90% of code doesn't make engineers 10x productive: writing code is only one part of the job alongside reviewing, testing, debugging, and deploying, so even eliminating coding time yields maybe 30-40% gains. More importantly, when technology gets cheaper to build, its ROI rises, so high-ceiling companies like JP Morgan should invest more and hire more engineers.

  • AI writing 90% of code doesn't make engineers 10x productive; they also review, test, debug, design, and deploy.
  • Amdahl's law: parallelizing one task to near-zero only shifts the total by that task's share (e.g. 100 to 73 units).
  • They see roughly 30-40% productivity improvements, not 10x.
  • Cheaper technology raises the ROI of building it, so high-ceiling companies invest and hire more.
  • JP Morgan Chase has a ~$17B software budget and 50,000+ engineers, each now more productive.

if AI is writing over 90% of the code, that doesn't mean engineers are 10x as productive, right? Engineers spend more time than just writing…

Varun Mohan · 1:04:00

the ROI of building technology has actually gone up.

Varun Mohan · 1:05:30
#productivity#economics#engineering#ai

Story· 3

Story04:30

From GPU Infra to Kodium to Windsurf: The Two Pivots

Varun recounts starting the company nearly four years ago building GPU virtualization and compiler software, before ChatGPT existed. When generative models got good in mid-2022, the team realized their bespoke-model infrastructure was losing value, so they vertically integrated into an AI coding product (Kodium), then forked VS Code six months before the interview to build the Windsurf IDE.

  • Started ~4 years ago in GPU virtualization; Varun came from autonomous vehicles, co-founder from AR/VR at Meta.
  • By mid-2022 they had a couple million in revenue, ~10,000 GPUs managed, 8 people, free-cash-flow positive.
  • Realized that if everyone runs the same generative models, an infrastructure company can't differentiate.
  • Vertically integrated their inference infra into Kodium, an AI coding product offered free across all IDEs.
  • Forked VS Code ~6 months ago because existing IDEs capped the agentic capabilities they could ship.

And in a world in which everyone was going to run generative AI models, why would an infrastructure company be a differentiator?

Varun Mohan · 06:00
#startups#pivots#ai-coding#company-history
Story13:30

Forking VS Code Tripled Their Acceptance Rate With the Same Models

Varun describes why they built a custom IDE instead of staying inside VS Code: they believed AI would write over 90% of software, shifting the developer's job toward reviewing code. When they ported their autocomplete/refactor UI to Windsurf, acceptance rate tripled using the identical ML models, proving the surface matters as much as the technology.

  • They believed AI would write well over 90% of software, making code review the developer's main job.
  • VS Code's limited APIs forced hacks like dynamically generating images next to the cursor.
  • Porting the same models to Windsurf tripled the acceptance rate.
  • Lesson: great technology delivers little value if the surface and interface can't showcase it.

immediately by porting over to Windsorf our acceptance rate tripled same ML models it just tripled

Varun Mohan · 15:00
#product#ide#ux#ai-coding
Story49:30

Their Sales Team Built Their Own Software and Saved $500K in SaaS

When Windsurf launched, they tasked everyone in the company, including the go-to-market and sales teams, with building an app using it. The result: over half a million dollars of SaaS products they were going to buy were replaced by internally built tools, including a partner portal built by a head of partnerships who had never written software.

  • Everyone at the company, including sales, was tasked with building an app with Windsurf.
  • They saved over half a million dollars in SaaS products they would have bought.
  • The head of partnerships built his own partner portal instead of buying one, despite never coding before.
  • The company built ways to deploy these internal apps securely.

we've saved over half a million dollars of of SAS products we were going to buy because our go to market team has now built…

Varun Mohan · 50:00
#ai-coding#productivity#internal-tools

Takeaway· 3

Takeaway10:30

Never Fall in Love With Your Ideas

Reflecting on pivoting away from a profitable business after raising $28M, Varun argues founders should assume many of their hypotheses are wrong and build a truth-seeking organization where morale doesn't collapse after a wrong bet. He frames each year's growing engineering output as a fresh chance to test new hypotheses.

  • They pivoted overnight from a profitable infra business, having already raised $28M, because focus is everything.
  • Assume a lot of your hypotheses will be wrong, then do concentrated work to validate them.
  • A truth-seeking org keeps morale up even after a wrong decision, preserving optionality.
  • Each year the company's total engineering output exceeds all prior years combined, a new lease on life to test hypotheses.

it's awesome when you have a great idea, but you should never be too in love with your ideas

Varun Mohan · 11:30
#decision-making#startups#culture
Takeaway26:30

Get an A+ on the One Class That Matters, an F on the Rest

Varun contrasts school with company-building: school optimizes total GPA, but companies win by doing one thing exceptionally and failing at nine others. Keeping the team underwater forces this ruthless prioritization, since a team will never ask to work on something unimportant when they can only take on one thing.

  • You don't win by doing ten things well; you win by doing one thing really well.
  • School optimizes total GPA; a company just needs an A+ on the one class that matters.
  • An F in other classes means deprioritizing what doesn't matter, not doing anything illegal.
  • Fewer people is a forcing function for organizational prioritization.

In school, you optimize for your total GPA, but for companies, I just need to get an A+ on the one class that matters and…

Varun Mohan · 27:00
#prioritization#focus#startups
Takeaway35:30

Why They Bet on Enterprise Sales Early (When Most Technical Founders Won't)

Varun pushes back on the technical-founder instinct that sales is negative and everything should be product-led growth. As a GPU-infra company he couldn't scale a sales function because he couldn't sell it himself, but once large enterprises reached out to Kodium and they ran tens of concurrent pilots, they hired a VP of Sales by end of 2023 and scaled an 80+ person go-to-market team.

  • Technical founders often wrongly see enterprise sales as negative and insist on pure PLG.
  • As an infra company they never hired sales because the founder couldn't yet scale the motion himself.
  • Large enterprises reached out to Kodium, driving tens of concurrent enterprise pilots by mid-2023.
  • They hired a VP of Sales by end of 2023; go-to-market is now 80+ people.
  • You can't sell to the Fortune 500 purely by swiping a credit card.

I think this is like a interesting thing that technical founders sometimes don't really like. They think sales is like a very negative sort of…

Varun Mohan · 36:00

if you want to sell to the Fortune 500, it is very hard to do that purely by swiping a credit card.

Varun Mohan · 37:30
#sales#enterprise#go-to-market