Filesystem-Mediated Multi-Agent Coordination: PID Registries, Cross-Repo Path Aliases, and Idempotent .env Injection

We present Filesystem-Mediated Multi-Agent Coordination (FM-MAC), the architectural pattern production-implemented in MaiiaM Alchemist v0.4.1, using five filesystem primitives as coordination substrate: PID registry (userData/service-pids/) for cross-session liveness detection via process.kill(pid, 0); root: path alias system for cross-repository CWD resolution; idempotent structured .env mutation for integrating third-party services without protocol negotiation; filesystem presence probing for zero-latency capability detection; and typed artifact files as durable cross-language asynchronous coordination contracts. For asynchronous, cross-language, resilience-critical coordination, filesystem primitives provide superior resilience, debuggability, and language-portability over message-passing alternatives.