Function render_window_json 

pub fn render_window_json(session: &Session, opts: &WindowOpts) -> Value

Render session as the versioned, agent-parseable JSON window (schema WINDOW_SCHEMA): orientation header, role-labelled turns with tool output folded, the recent tail kept within budget_chars. Pure and deterministic for a fixed (session, opts) - the MCP layer handles neutralization and the final size guard.