Startups building on OpenAI or Anthropic APIs face a major platform risk. Their usage data trains the underlying foundational models, enabling the platform owners to eventually absorb their features natively and make the startups obsolete.

For most startups, training a custom foundation model is a waste of capital. The winning strategy is to focus on workflow and proprietary data, building a "headless" product that uses a model router to switch between the cheapest, most effective LLMs for any given task.

The first step for an AI startup is to prove value using the best off-the-shelf models, even if they are expensive. Investing in custom models and post-training is a form of optimization that should only happen after product-market fit is established and there is a clear user signal to optimize for.

Creating frontier AI models is incredibly expensive, yet their value depreciates rapidly as they are quickly copied or replicated by lower-cost open-source alternatives. This forces model providers to evolve into more defensible application companies to survive.

Early-stage AI startups should resist spending heavily on fine-tuning foundational models. With base models improving so rapidly, the defensible value lies in building the application layer, workflow integrations, and enterprise-grade software that makes the AI useful, allowing the startup to ride the wave of general model improvement.

A vertical AI startup is extremely vulnerable if its core offering can be easily replicated by the foundational model it's built upon. True defensibility comes from integrating unique, proprietary data sources or solving non-obvious workflow problems that the base model cannot simply be prompted to do.

The traditional wisdom to "build what's core" to your business is becoming obsolete for AI. The immense cost and rapid advancement of foundational models by major labs mean most companies are better off buying or partnering for core AI capabilities rather than attempting to build them in-house.

To avoid being made obsolete by the next foundation model (e.g., GPT-5), entrepreneurs must build products that anticipate model evolution. This involves creating strategic "scaffolding" (unique workflows and integrations) or combining LLMs with proprietary data, like knowledge graphs, to create a defensible business.

Applied AI startups must solve immediate customer problems by building proprietary technology, even if they know it will be commoditized by foundation models in a few years. The strategy is to win customers now with superior tech, building a product and market position that will endure after the technology becomes table stakes.