Stagehand is an open-source SDK developed by Browserbase designed to facilitate the creation of autonomous browser agents across TypeScript, Python, and Go. The framework provides high-level abstractions—specifically observe(), act(), and extract()—to enable natural language interaction with web elements. The observe() method identifies real CSS selectors to allow for secure credential handling, while the act() method provides "self-healing" capabilities that adapt to website redesigns. For data retrieval, the extract() method utilizes schema validation via Zod (TypeScript) or Pydantic (Python) to return structured, typed data from complex web pages. Technically, Stagehand optimizes token efficiency through hybrid accessibility-tree trimming and reduces latency by running as a browser extension. It supports integration with various LLMs, such as openai/gpt-5.4-mini, and offers a Model Gateway and server-side caching to minimize costs and round-trip times. Additionally, the ecosystem includes specialized tools like Fetch for markdown conversion, a web search utility, and a hosted Model Context Protocol (MCP) server, allowing agents to interact with web content via MCP clients like Claude or Cursor without requiring a local browser environment.