Stagehand

StagehandSince 2026-02

Stagehand is an AI-native browser automation SDK for TypeScript and Node.js created by Browserbase. It provides simple, high-level primitives (act, extract, and observe) that turn fragile CSS/XPath selectors into resilient natural language actions powered by frontier LLMs. By integrating directly with Playwright, Stagehand allows developers to mix standard deterministic browser code with dynamic AI-driven actions, creating test suites and automation scripts that never break when CSS classes or DOM hierarchies change.

Stagehand uses hierarchical DOM filtering to send compact accessibility trees to LLMs, keeping latency low and execution deterministic. Its extract method parses unstructured page contents directly into Zod schemas, while act executes complex multi-step user actions like selecting dates in dynamic calendar pickers. Stagehand can run locally on standard Playwright instances or scale horizontally across Browserbase's managed browser cloud with anti-bot bypass and session recording.

Cosine GenieSince 2024-08

Cosine Genie is a next-generation autonomous software engineering agent built to tackle complex software bugs, refactors, and feature requests. Operating with deep semantic understanding of massive codebases, Genie analyzes repository architectures, creates comprehensive execution plans, and generates multi-file diffs that pass existing continuous integration test suites. Designed to bridge the gap between AI code completion and full software development lifecycle automation, Genie mimics human engineering workflows by navigating dependency graphs, testing assumptions in sandboxed environments, and autonomously self-correcting logic errors before opening pull requests.

Genie is powered by Cosine's proprietary fine-tuned reasoning models and multi-agent orchestration framework, benchmarked at top-tier performance on the industry-standard SWE-bench. The system integrates directly with GitHub and GitLab, indexing abstract syntax trees (ASTs), commit histories, and documentation to maintain contextual awareness. Its sandboxed runtime spins up localized build containers to execute unit tests, compile artifacts, and measure regression risks in real time. Engineering teams use Genie to triage backlogs, automate dependency upgrades, and accelerate code reviews with verified pull request generation.