YC provides a built-in go-to-market engine where startups treat their 200+ well-funded batchmates as their first customers. This 'win YC, win the market' strategy de-risks early customer acquisition and provides critical initial revenue and case studies to build momentum.

The old model of raising a large sum of money to build infrastructure is obsolete. Today, founders can and should validate their product and find customers with minimal capital *before* seeking significant investment, reversing the traditional order of operations.

Founders who've already built a product haven't missed the 'validation' window. The focus simply shifts from 'is there a problem?' to de-risking subsequent assumptions: Is the solution worthwhile? Will people pay enough? Can customers be acquired profitably? This process is ongoing, even at scale.

While a fusion reactor can't be built in three months, YC pushes hardware and deep tech founders to create a tangible Minimum Viable Proof. This forces them to de-risk the venture by hitting a critical milestone, such as building a small-scale desert prototype or securing key letters of intent, proving traction on a non-obvious timeline.

The flood of inbound leads from a YC launch accelerates customer discovery. However, founders recognize this attention is temporary and doesn't replace the need to build their own sustainable customer acquisition engines, creating a potential false sense of security.

Contrary to fears of a "circular economy," YC founder Paul Graham advises that selling to other startups is optimal. They are smarter, less bureaucratic, and more representative of future trends. A product that succeeds with this discerning group is well-positioned for broader market success.

Even startups with traction and pre-seed funding find Y Combinator transformative. YC partners provide unparalleled, stage-specific feedback that founders can't easily get elsewhere, making the 7% equity cost worthwhile for companies well beyond the idea stage.

AI agents require deep, nuanced understanding of specific workflows. YC's methodology, which forces founders to intensely engage with customers and iterate rapidly, provides the perfect training ground to acquire this necessary domain expertise, making it an ideal environment for this new class of startups.

After experiencing numerous lukewarm responses to failed ideas, the intense, urgent demand from a customer for a successful product becomes an undeniable signal. The contrast between a polite 'maybe later' and a frantic 'how do I get this now?' makes true product-market fit impossible to miss.