A markdown file — not a product, not a platform — a markdown file catalyzed a ~$285 billion single-session collapse across software, financial services, and alternative asset managers.

On January 30th, Anthropic released a set of plugins for Claude Cowork, its desktop AI tool. One of them handled legal contract review. It could triage NDAs, flag non-standard clauses against a negotiation playbook, and generate compliance summaries — the kind of work that, until last week, required a paralegal, a Westlaw subscription, and billable hours.

The plugin was open-source. Anyone could read it. And when people did, they found roughly 200 lines of structured markdown prompts — first-year law school content dressed up with some clever workflow logic. It shipped with a disclaimer: “All outputs should be reviewed by licensed attorneys.”

By the close on Monday, Thomson Reuters had posted its biggest single-day stock decline on record — down nearly 18%. RELX, the parent company of LexisNexis, fell roughly 14%. Wolters Kluwer dropped about 13%. LegalZoom cratered nearly 20%. FactSet lost more than 10%. Morningstar fell 9%. The Goldman Sachs U.S. software basket posted its worst session since the April tariff selloff. The selling spread to alternative asset managers and private equity firms across the board.

The catalyst wasn’t just the plugin. Software companies were already posting disappointing earnings — missing revenue estimates at rates not seen since the post-COVID correction — and the broader “AI disruption” repricing had been building for months. But the Anthropic release crystallized the fear into a single, legible image: a text file doing work that billion-dollar companies charge per-seat fees to access. The logic was brutally simple: if AI compresses the cost of legal and financial analysis, then every firm charging premium fees for that analysis has a margin problem. Not next year. Now.

Jeffrey Favuzza on the Jefferies equity trading desk gave it a name. “We call it the SaaSpocalypse,” he told Bloomberg. “Trading is very much ‘get me out’ style selling.”

Here’s what almost nobody is saying clearly enough: the markdown file didn’t cause this. It revealed it. The per-seat SaaS licensing model — the financial bedrock that the entire enterprise software economy has been built on for twenty years — was already cracking. The market just hadn’t priced it in yet.

Here’s what’s inside:

  • The crash wasn’t about Claude. What actually broke, why the “Anthropic killed SaaS” narrative misses the structural story, and what the sell-off tells you about where enterprise software is headed.
  • The counterargument Jensen Huang is making — and the part he’s getting wrong. Why defending the product doesn’t save the pricing model, and what print media should have taught us.
  • The KPMG signal. A quieter story that matters more than any stock chart — how the Big Four are already using AI as fee negotiation leverage, and why the cascade is just starting.
  • What actually died (and what didn’t). The data edge and the accountability edge are real. The per-seat model sitting on top of them is not. What that means for incumbents, buyers, and builders.
  • The articulation problem. Why “build your own” isn’t as simple as the hype suggests, what the real bottleneck is, and how much time the incumbents actually have.
  • Why this is fractal. The same bolt-on vs. rebuild dynamic that’s threatening SaaS companies applies to every knowledge worker reading this — and the window is narrowing.

Let me show you what the SaaSpocalypse actually revealed — and what it means for how you work.

By NAte

https://natesnewsletter.substack.com/p/200-lines-of-markdown-just-triggered