diff --git a/src/hqt/cli.py b/src/hqt/cli.py
index 7069f7f..55cbebb 100644
--- a/src/hqt/cli.py
+++ b/src/hqt/cli.py
@@ -121,6 +121,47 @@ def doctor():
         click.echo("No harnesses found on PATH")
 
 
+def _build_session_service():
+    """Wire a SessionService the same way HqtApp.on_mount does (for CLI use)."""
+    from hqt.config import get_settings
+    from hqt.db.engine import ensure_db, get_engine, get_session_factory
+    from hqt.harnesses.registry import discover_harnesses
+    from hqt.sessions.service import SessionService
+    from hqt.tmux.manager import TmuxManager
+    from hqt.tmux.runner import TmuxRunner
+
+    settings = get_settings()
+    ensure_db(settings)
+    factory = get_session_factory(get_engine(settings))
+    runner = TmuxRunner(settings.tmux_path, settings.tui_session_name)
+    return SessionService(factory, TmuxManager(runner), discover_harnesses())
+
+
+@main.command(name="tool")
+@click.argument("tool")
+@click.argument("window")
+def tool_cmd(tool, window):
+    """Run TOOL for the session in tmux WINDOW.
+
+    TOOL is nvim/lazygit/shell (opens a styled tool window) or "clone" (a fresh
+    harness with the same project + model). WINDOW is the tmux window name (the
+    hqt-<id> key, e.g. from #{window_name}).
+    """
+    import asyncio
+
+    from hqt.errors import ServiceError
+
+    svc = _build_session_service()
+    try:
+        if tool == "clone":
+            asyncio.run(svc.clone_session_for_window(window))
+        else:
+            asyncio.run(svc.open_tool_window_for_window(window, tool))
+    except ServiceError as err:
+        click.echo(str(err), err=True)
+        raise SystemExit(1)
+
+
 @main.command(name="list")
 def list_cmd():
     """List projects and sessions."""
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..652116b
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,65 @@
+from click.testing import CliRunner
+
+from hqt import cli
+from hqt.config import Settings
+
+
+def test_tool_cmd_opens_tool_window(monkeypatch, tmp_path):
+    monkeypatch.setattr(
+        "hqt.config.get_settings", lambda: Settings(db_path=tmp_path / "t.db")
+    )
+    calls = {}
+
+    async def fake_for_window(self, window, tool):
+        calls["tool"] = (window, tool)
+        return "@9"
+
+    monkeypatch.setattr(
+        "hqt.sessions.service.SessionService.open_tool_window_for_window",
+        fake_for_window,
+    )
+
+    result = CliRunner().invoke(cli.main, ["tool", "lazygit", "hqt-5"])
+
+    assert result.exit_code == 0, result.output
+    assert calls["tool"] == ("hqt-5", "lazygit")
+
+
+def test_tool_cmd_clone_dispatches_to_clone(monkeypatch, tmp_path):
+    monkeypatch.setattr(
+        "hqt.config.get_settings", lambda: Settings(db_path=tmp_path / "t.db")
+    )
+    calls = {}
+
+    async def fake_clone(self, window):
+        calls["clone"] = window
+        return "RESULT"
+
+    monkeypatch.setattr(
+        "hqt.sessions.service.SessionService.clone_session_for_window", fake_clone
+    )
+
+    result = CliRunner().invoke(cli.main, ["tool", "clone", "hqt-5"])
+
+    assert result.exit_code == 0, result.output
+    assert calls["clone"] == "hqt-5"
+
+
+def test_tool_cmd_reports_service_error(monkeypatch, tmp_path):
+    from hqt.errors import ServiceError
+
+    monkeypatch.setattr(
+        "hqt.config.get_settings", lambda: Settings(db_path=tmp_path / "t.db")
+    )
+
+    async def boom(self, window, tool):
+        raise ServiceError("'hqt-5' is not an hqt session window")
+
+    monkeypatch.setattr(
+        "hqt.sessions.service.SessionService.open_tool_window_for_window", boom
+    )
+
+    result = CliRunner().invoke(cli.main, ["tool", "nvim", "hqt-5"])
+
+    assert result.exit_code == 1
+    assert "not an hqt session window" in result.output