Anthropic acquisition of Stainless eyed at $300M in talks

Anthropic acquisition talks are underway for developer tools startup Stainless, with the deal expected to be at least $300 million and still subject to change.

What Stainless does and why it matters

Stainless builds software that converts complex APIs into SDKs, making AI models easier to use for developers, non-technical users and automated agents.

Its customers include Anthropic, OpenAI and Google, and its tooling has seen higher demand as AI agents like Claude Code and OpenClaw automate more tasks.

Deal terms, funding and company profile

The talks would value Stainless well above its last reported valuation of $150 million in December 2024, with the contemplated price starting at $300 million.

Founded roughly four years ago, Stainless employs about 80 people and has raised $35 million from investors such as Andreessen Horowitz, Sequoia Capital and Felicis.

Sources say Anthropic may use some stock as part of the consideration, though negotiations remain preliminary and terms could shift before a closing.

Competitive and technical context

Stainless streamlines access to APIs for model providers and infrastructure firms, supporting integrations with Cloudflare and Cerebras as well as major model hosts.

The company also built software compatible with Anthropic’s Model Context Protocol, an open standard the company released in November 2024 to help models and agents use external tools.

Other firms and open-source projects make similar SDK tooling, including Speakeasy, LibLab and the OpenAPI Generator, but Stainless has become a common choice among leading labs.

Anthropic itself has shifted toward more acquisitions recently. After signaling readiness to buy in the fall, the company completed its first deal in December with Bun and later acquired Vercept and Coefficient Bio.

If completed, the transaction would give Anthropic ownership of a widely used route developers use to connect to rival models from OpenAI and Google, potentially shifting competitive dynamics around developer experience.

Anthropic was reported to have a valuation of $350 billion in February, a figure cited by sources discussing purchase options and equity-based payment structures.

Regulators and customers will likely watch how ownership changes affect neutral access to SDK tooling and whether integration tightens around Anthropic’s ecosystem.

Next steps include formal agreement on price and structure, regulatory review if required, and potential integration plans for Stainless’ products into Anthropic’s tooling suite.

Observers should monitor filings, developer reactions and any statements from Stainless’ backers as the negotiations progress to a final deal or collapse.