Simon Willison reveals that both Anthropic and OpenAI have found true product-market fit, but not as consumer apps - rather as essential infrastructure that enterprises need. Meanwhile, Anthropic has launched an open-source framework for automated code vulnerability detection
Unexpected Product-Market Fit
Simon Willison, renowned developer and AI analyst, revealed in an interview that both Anthropic and OpenAI have discovered genuine product-market fit, but not in the form of consumer applications as many expected Key evidence Simon points to:
- Anthropic rumored to reach $40 billion valuation in a new fundraising round
- OpenAI's enterprise revenue continues to grow especially from API and enterprise solutions
- Both companies have real enterprise customers not just general users
Importantly, their product-market fit isn't in chatbots for the general public, but in AI infrastructure that businesses and organizations need to build their own products and services
Defending Code Harness: AI-Powered Vulnerability Detection
Anthropic open-sourced the Defending Code Harness framework on June 4, 2026, using LLMs - specifically Claude - to automatically find vulnerabilities in codebases Key features of Defending Code Harness: Not just traditional static analysis but uses AI intelligence to understand context and find complex vulnerabilities Uses Claude as the core engine for code analysis and security issue identification
Open-sourced with enterprise-friendly licensing
Can detect logic-level vulnerabilities that traditional tools miss This framework proves that AI can effectively help with security, especially in finding vulnerabilities hidden in program logic
Key Lessons from Anthropic's Growth
Anthropic and OpenAI's success as infrastructure providers offers several important lessons:
- AI doesn't need to be a consumer product to achieve business success
- Enterprise market is large enough for high-end AI technology
- Open-source still plays a crucial role even in the age of AI giants
- Security and reliability matter more to enterprises than new features
The open-source release of Defending Code Harness shows that Anthropic understands this concept well and is trying to build a strong ecosystem around its technology
References
Simon Willison: https://simonwillison.net/2026/May/27/product-market-fit/ Defending Code Harness: https://news.ycombinator.com/item?id=41298023