tl;dr: Pi reversed its stance against MCP and brought it into the core, driven by MCP's maturation and the realization that supporting it well required infrastructure (like deferred tool loading and metadata) that also benefits other features. The integration pairs MCP with "Codemode," a JavaScript/WASM sandbox running on the harness side that lets the agent compose tool calls programmatically—treating MCP more like OpenAPI with structured data and discoverable tools, rather than dumping everything into context.