Unit was hard-coding HOMELAB_MCP_SSH_USER=mcp-reader, overriding the new code's 'root' default. No mcp-reader user exists on hubris — the key is authorized for root, with a strict command= wrapper. Also pin HOMELAB_MCP_HUBRIS_HOST + KNOWN_HOSTS env so the service doesn't depend on the python defaults staying in sync with the unit. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>