| Agent | Codex, IDE assistant, or automation that uses X4 commands. |
| Code Assist | Mastra GitHub bot workflows for planning, implementation, testing, and follow-up. |
| Control node | Host that owns remote validation job state and worker leases. |
| Devbox | Developer machine or VM where X4 workspaces are edited. |
| Evidence | Logs, artifacts, preview URLs, check runs, and comments derived from execution. |
| Execution model | YAML model for control nodes, workers, and worker classes. |
| Registry | YAML configuration for repo sets, sandbox profiles, env bundles, and validation commands. |
| Sandbox | Runtime environment for validating or previewing a workspace. |
| Tailnet preview | Private Tailscale URL safe to post as tester-facing evidence. |
| Testbox | Worker host used for remote validation. |
| Workspace | X4-managed multi-repo working set with shared metadata under .x4/. |
| Worktree | Git worktree attached to a repo, often generated by X4 or Mastra for a feature/issue. |