Mutation Server Protocol Specification

The `mutation-server-protocol` package defines the Mutation Server Protocol (MSP), a standardized, language-agnostic specification based on JSON-RPC 2.0. Its purpose is to enable seamless communication between Integrated Development Environments (IDEs) or other tools and mutation testing frameworks. Inspired by the Language Server Protocol, MSP establishes a unified method for initiating mutation tests, reporting their progress, and exchanging structured data like mutation locations and results. The current stable version is 0.4.2, with recent minor updates in March 2026, indicating active maintenance within the Stryker Mutator monorepo. Key differentiators include its explicit focus on mutation testing, support for both Standard Input/Output (stdio) and TCP/IP Socket transport modes, and detailed message formats for operations such as mutant discovery and execution. It emphasizes 1-based indexing for positions and locations, aligning with common text editor conventions.