Summary Cobalt offers a comprehensive, unofficial WhatsApp API for JVM languages, enabling Java and Kotlin applications to function as WhatsApp clients. It provides two integration methods: a reverse-engineered "Linked" client mimicking official apps and direct integration with Meta's official "Cloud" API, catering to developers needing WhatsApp connectivity.

How It Works Cobalt supports two primary integration paths. The "Linked" client is a clean-room reimplementation of WhatsApp Web/Desktop/Mobile, operating without browsers. The "Cloud" client interfaces directly with Meta's official hosted WhatsApp Cloud API via HTTPS, including an integrated webhook server. Both approaches share a unified message model, prioritizing performance and feature coverage.

Quick Start & Requirements Requires Java 25. Installation uses Maven/Gradle (com.github.auties00:cobalt-lib:0.1.0). Native libraries for calls/media are downloaded or vendored per platform (Windows, Linux, macOS, x86-64, ARM64). Quickstart examples cover QR code scanning (Linked client) and credential-based connection (Cloud API). Extensive Javadocs serve as primary documentation.

Highlighted Details

• Codegen Tools: Automate Protobuf, AB Props, GraphQL, and WAM schema generation by extracting data from live WhatsApp Web clients.
• Cobalt MCP: A Node.js/Playwright-based reverse-engineering and interaction tool.
• Agentic Validator: Experimental system for verifying feature parity between Cobalt modules and official WhatsApp clients.
• Virtual Threads: All operations leverage Java virtual threads, making blocking calls efficient and preventing connection stalls.

Maintenance & Community The project is maintained by the author in their free time, supported by GitHub Sponsors. Contributions are welcomed. No specific community channels (e.g., Discord, Slack) are listed.

Licensing & Compatibility The specific license type is not explicitly stated. A critical disclaimer notes Cobalt is unofficial and not affiliated with Meta. The reverse-engineered Linked client may breach WhatsApp's Terms of Service, risking account restrictions or breakage. Commercial messaging should use the official Cloud API.

Limitations & Caveats Cobalt is pre-1.0, with breaking changes expected until API stabilization. The unofficial Linked client carries inherent risks of account suspension and service interruption. The Agentic Validator is experimental and not fully operational.