swipl-mcp-server

# Session State Machine This document illustrates the session state machine used by `PrologInterface` to coordinate query and engine sessions. ## Diagram (Mermaid) ```mermaid stateDiagram-v2 [*] --> idle idle --> query: startQuery query --> query: nextSolution (has solution) query --> query_completed: nextSolution (no more) query --> idle: error query_completed --> closing_query: closeQuery closing_query --> idle idle --> engine: startEngine engine --> engine: nextEngine (has solution) engine --> engine_completed: nextEngine (no more) engine --> idle: error engine_completed --> closing_engine: closeEngine closing_engine --> idle note right of query_completed: Keeps context until closed note right of engine_completed: Keeps context until closed ``` ## Notes - The engine mode follows the same pattern: `startEngine` → `engine` → `engine_completed` → `closing_engine` → `idle` - Exactly one session type can be active at a time (query or engine). - The `*_completed` states keep context so that subsequent `next` calls respond with "no more solutions" until explicitly closed. - Transient `closing_*` states serialize shutdown before new sessions begin. - Invalid transitions are logged when `SWI_MCP_TRACE=1`.