Here's a scenario that's playing out in boardrooms and founder conversations all over the world right now. A mid-sized company, let's say a regional food safety operator running forty sites, is using a piece of vertical software that costs them €30,000 a year. Their new head of technology comes in, opens up Claude, and says: "I reckon we could build something like this ourselves."

And they're not wrong. Not entirely. The prototype is genuinely impressive. It takes three weeks. The CEO gets excited. The CFO starts doing mental maths on €30k a year versus a one-time build cost. And then someone asks a question that changes the whole conversation: "What happens if it goes wrong?"

There's a version of this series that stays entirely at the product level. Switching costs, regulatory moats, data assets, go-to-market depth: all of it matters, and I'll have nine articles making the case for why. But there's a variable that cuts across all of it, that can neutralise every structural advantage a vertical SaaS business has, and it doesn't show up in any financial model. It's the person running the business, and whether they're genuinely willing to change.

If I had to pick one insight from the last two years of watching AI reshape the software industry, it would be this: people consistently overestimate how much easier AI has made it to displace an incumbent software business, while correctly observing that it's made it easier to replicate one.

These are not the same thing. And the gap between them is where a lot of the interesting investing happens right now.

I'm starting a series of posts. Nobody asked for it, but I've been doing some deep SaaS contemplation so thought I'd write it down.

There's a strange thing happening in software investing at the moment. On one side, you've got the AI maximalists telling you that SaaS is dead, that agents will replace every application, and that anything built before 2023 is basically a legacy system waiting to be disrupted…..

There's a question I've started asking in almost every management meeting I do with a vertical software business, and it goes something like this: how long has your longest-tenured salesperson been here?

It sounds like an HR question. It isn't. It's one of the most revealing things you can ask..

The AI-kills-SaaS narrative has become almost ritualistic at this point. Every few months someone publishes a hot take: agents will automate everything, vibe-coders will build it themselves over a weekend, the incumbents are toast….