diff --git a/nanobot/cli/entry.py b/nanobot/cli/entry.py
index 534c84f82..65ae4d28e 100644
--- a/nanobot/cli/entry.py
+++ b/nanobot/cli/entry.py
@@ -71,7 +71,11 @@ def _run_agent(args: list[str], *, prog_name: str) -> None:
 def main() -> None:
     """Dispatch native TUI startup without importing the complete CLI graph."""
     raw_args = sys.argv[1:]
-    agent_args = _agent_invocation_args(raw_args)
+    # Installed completion scripts call ``nanobot`` without positional arguments
+    # and pass the request through this environment variable. Keep those requests
+    # on the root command so subcommands remain discoverable.
+    shell_completion = bool(os.environ.get("_NANOBOT_COMPLETE"))
+    agent_args = None if shell_completion else _agent_invocation_args(raw_args)
     dispatch_args = ["agent", *agent_args] if agent_args is not None else raw_args
     set_cli_process_identity(dispatch_args)
     _configure_windows_console()
diff --git a/tests/cli/test_entry.py b/tests/cli/test_entry.py
index b3cb4c2cc..bee8a9ce2 100644
--- a/tests/cli/test_entry.py
+++ b/tests/cli/test_entry.py
@@ -1,3 +1,8 @@
+import os
+import subprocess
+import sys
+from pathlib import Path
+
 from nanobot.cli import entry
 from nanobot.cli.entry import _agent_invocation_args, _native_tui_candidate
 
@@ -23,6 +28,36 @@ def test_root_metadata_and_subcommands_keep_the_root_cli() -> None:
         assert _agent_invocation_args(args) is None
 
 
+def test_root_shell_completion_keeps_root_subcommands() -> None:
+    env = os.environ.copy()
+    env.update(
+        {
+            "_NANOBOT_COMPLETE": "complete_bash",
+            "COMP_WORDS": "nanobot ",
+            "COMP_CWORD": "1",
+        }
+    )
+    script = (
+        "import sys; "
+        "from nanobot.cli.entry import main; "
+        "sys.argv = ['nanobot']; "
+        "main()"
+    )
+
+    result = subprocess.run(
+        [sys.executable, "-c", script],
+        cwd=Path(__file__).parents[2],
+        env=env,
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+    assert result.returncode == 0, result.stderr
+    assert {"agent", "gateway", "webui"} <= set(result.stdout.splitlines())
+    assert "not supported" not in result.stderr
+
+
 def test_root_alias_dispatches_the_shared_agent_command(monkeypatch) -> None:
     calls: dict[str, object] = {}
     monkeypatch.setattr(entry.sys, "argv", ["nanobot", "-m", "hello"])