Anthropic's AI models have become foundational components for many modern AI products. At the same time, technology companies are increasingly concerned that a key supplier could turn into a direct competitor: clients complain about high prices and rigid contract terms, and worry that Anthropic's moves into end-user markets could put them at risk.
Case study: Spellbook and Claude for Legal
In 2025, the legal AI startup Spellbook signed a long-term agreement with Anthropic to use its models for contract review. Scott Stevenson, Spellbook's CEO, said he did not expect Anthropic to become a direct competitor at the time; Anthropic employees reportedly reassured Spellbook that they did not plan to compete in the legal services market.
One year later, Anthropic announced Claude for Legal, a product aimed at law firms offering dozens of features—from contract review and citation checks to tracking regulatory changes. Many of these features overlap with Spellbook's offerings, a development Stevenson described as "somewhat awkward." As a result, Spellbook began sharing company data and product plans with Anthropic more cautiously.
Before the announcement, Spellbook was performing more than 500,000 contract reviews per month for clients using Claude; after the product launch, Spellbook shifted a significant portion of its spending to OpenAI.
Customer dissatisfaction: prices, terms, searching for alternatives
Spellbook is not the only company with a complicated relationship with Anthropic. Several customers have expressed dissatisfaction with Anthropic's steep pricing and inflexible negotiation stance. Some are already exploring alternative providers and models to reduce costs and lower supplier concentration risk.
Regulatory and industry tensions ahead of IPO
Anthropic has also had clashes with the U.S. government and parts of the industry while preparing for a public listing. Those disputes add another layer of uncertainty for companies deciding whether to build on Anthropic's technology.
What risk do partners take?
The situation highlights a dilemma for startups and tech firms that build on external AI platforms: a rapidly growing model provider can enter downstream markets and compete directly with its customers. Spellbook's experience shows how such moves can alter partner relationships and procurement choices.
Conclusions
Heavy reliance on Anthropic models can accelerate product development in the short term but creates strategic risk over time. For partners, the key question is how long it makes sense to base a business on a supplier that may also become a competitor. In response, several companies have started diversifying their model sourcing and adopting more cautious data-sharing practices.
