diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 9ad4d0142b42..49740bcaabe3 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -675,6 +675,9 @@ def _resolve_session_by_name_or_id(name_or_id: str) -> Optional[str]:
 
 def cmd_chat(args):
     """Run interactive chat CLI."""
+    if not getattr(args, "query", None):
+        _require_tty("chat")
+
     # Resolve --continue into --resume with the latest CLI session or by name
     continue_val = getattr(args, "continue_last", None)
     if continue_val and not getattr(args, "resume", None):
diff --git a/hermes_cli/setup.py b/hermes_cli/setup.py
index e12f7d1a7601..14c7e74aba63 100644
--- a/hermes_cli/setup.py
+++ b/hermes_cli/setup.py
@@ -2946,6 +2946,9 @@ def _resolve_hermes_chat_argv() -> Optional[list[str]]:
 
 def _offer_launch_chat():
     """Prompt the user to jump straight into chat after setup."""
+    if not is_interactive_stdin():
+        return
+
     print()
     if not prompt_yes_no("Launch hermes chat now?", True):
         return
diff --git a/tests/hermes_cli/test_setup_noninteractive.py b/tests/hermes_cli/test_setup_noninteractive.py
index e3e243b4cc3b..b0e5a8406320 100644
--- a/tests/hermes_cli/test_setup_noninteractive.py
+++ b/tests/hermes_cli/test_setup_noninteractive.py
@@ -127,7 +127,7 @@ def test_chat_first_run_headless_skips_setup_prompt(self, capsys):
         """Bare `hermes` should not prompt for input when no provider exists and stdin is headless."""
         from hermes_cli.main import cmd_chat
 
-        args = _make_chat_args()
+        args = _make_chat_args(query="hello")
 
         with (
             patch("hermes_cli.main._has_any_provider_configured", return_value=False),
@@ -144,6 +144,71 @@ def test_chat_first_run_headless_skips_setup_prompt(self, capsys):
         out = capsys.readouterr().out
         assert "hermes config set model.provider custom" in out
 
+    def test_chat_requires_tty_for_interactive_mode(self, capsys):
+        """Interactive chat should fail fast in headless mode before launching the TUI."""
+        from hermes_cli.main import cmd_chat
+
+        args = _make_chat_args()
+
+        with (
+            patch("sys.stdin") as mock_stdin,
+            patch("hermes_cli.main._has_any_provider_configured", side_effect=AssertionError("provider check should not run")),
+            patch("cli.main", side_effect=AssertionError("interactive CLI should not launch")),
+        ):
+            mock_stdin.isatty.return_value = False
+            with pytest.raises(SystemExit) as exc:
+                cmd_chat(args)
+
+        assert exc.value.code == 1
+        err = capsys.readouterr().err
+        assert "requires an interactive terminal" in err
+        assert "hermes chat" in err
+
+    def test_chat_allows_single_query_without_tty(self):
+        """Single-query mode should remain available in headless environments."""
+        from hermes_cli.main import cmd_chat
+
+        args = _make_chat_args(query="hello")
+
+        with (
+            patch("sys.stdin") as mock_stdin,
+            patch("hermes_cli.main._has_any_provider_configured", return_value=True),
+            patch("cli.main") as mock_cli_main,
+        ):
+            mock_stdin.isatty.return_value = False
+            cmd_chat(args)
+
+        mock_cli_main.assert_called_once()
+        assert mock_cli_main.call_args.kwargs["query"] == "hello"
+
+    def test_offer_launch_chat_skips_prompt_and_exec_without_tty(self):
+        """Post-setup chat handoff should be a no-op when stdin is headless."""
+        from hermes_cli.setup import _offer_launch_chat
+
+        with (
+            patch("sys.stdin") as mock_stdin,
+            patch("hermes_cli.setup.prompt_yes_no", side_effect=AssertionError("prompt should not be called")),
+            patch("os.execvp", side_effect=AssertionError("exec should not be called")),
+        ):
+            mock_stdin.isatty.return_value = False
+            _offer_launch_chat()
+
+    def test_offer_launch_chat_prompts_and_execs_with_tty(self):
+        """Post-setup chat handoff should still work in an interactive terminal."""
+        from hermes_cli.setup import _offer_launch_chat
+
+        with (
+            patch("sys.stdin") as mock_stdin,
+            patch("hermes_cli.setup.prompt_yes_no", return_value=True) as mock_prompt,
+            patch("hermes_cli.setup._resolve_hermes_chat_argv", return_value=["hermes", "chat"]),
+            patch("os.execvp") as mock_execvp,
+        ):
+            mock_stdin.isatty.return_value = True
+            _offer_launch_chat()
+
+        mock_prompt.assert_called_once_with("Launch hermes chat now?", True)
+        mock_execvp.assert_called_once_with("hermes", ["hermes", "chat"])
+
     def test_returning_user_terminal_menu_choice_dispatches_terminal_section(self, tmp_path):
         """Returning-user menu should map Terminal Backend to the terminal setup, not TTS."""
         from hermes_cli import setup as setup_mod