Trail wraps any command (trail run -- <cmd>) or Docker container and captures its stdout/stderr into per-session JSONL files on local disk. The bundled MCP server exposes list_sessions and get_logs so Claude Code can filter by level, regex, time window, or line range — server-side, without burning context window. Includes a debug-with-trail skill that walks Claude through a 4-phase debug flow: read existing logs first, add marked instrumentation only when needed, and a mandatory cleanup step verified by grep. Local-first, no cloud, no daemon, single static binary.