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ellymud

A headless-testable MUD, built as a testbed for agent play

A TypeScript MUD (Telnet and WebSocket, with a React admin panel) built as a research question: can an LLM build a MUD, and can other LLMs play it. First commit 2025-03-17; 440 commits over roughly 13.5 months; public, dual-licensed AGPL-3.0 with a separate commercial license.

The answer’s machinery is an MCP server (src/mcp/mcpServer.ts, 2,400+ lines) whose virtual_session_* tools ride the same VirtualConnection abstraction real Telnet and WebSocket clients use — not a mocked API standing in for the game — plus deterministic-testing tools (snapshot load/save, tick control, stat/NPC injection) so an agent can drive and inspect a session the same way a human plays it. Test suite: 3,573 test cases across 167 files (grep-counted directly against the repo), a sampled file checked for substantive assertions rather than tautological ones.