diff --git a/tests/tools/test_voice_mode.py b/tests/tools/test_voice_mode.py
index 1d35c486..001aae60 100644
--- a/tests/tools/test_voice_mode.py
+++ b/tests/tools/test_voice_mode.py
@@ -61,6 +61,16 @@ def mock_sd(monkeypatch):
 # ============================================================================
 
 class TestDetectAudioEnvironment:
+    @pytest.fixture(autouse=True)
+    def _isolate_container_detection(self, monkeypatch):
+        """Default `is_container` to False so tests don't inherit the host
+        runner's container state (e.g. CI itself runs inside Docker, where
+        the production `is_container()` returns True via /.dockerenv or
+        /proc/1/cgroup and silently appended a 'Running inside Docker'
+        warning to every scenario). Individual tests opt in via setattr.
+        """
+        monkeypatch.setattr("tools.voice_mode.is_container", lambda: False)
+
     def test_clean_environment_is_available(self, monkeypatch):
         """No SSH, Docker, or WSL — should be available."""
         monkeypatch.delenv("SSH_CLIENT", raising=False)
@@ -85,6 +95,20 @@ class TestDetectAudioEnvironment:
         assert result["available"] is False
         assert any("SSH" in w for w in result["warnings"])
 
+    def test_docker_container_blocks_voice(self, monkeypatch):
+        """Running inside a Docker/Podman container should block voice mode."""
+        monkeypatch.delenv("SSH_CLIENT", raising=False)
+        monkeypatch.delenv("SSH_TTY", raising=False)
+        monkeypatch.delenv("SSH_CONNECTION", raising=False)
+        monkeypatch.setattr("tools.voice_mode.is_container", lambda: True)
+        monkeypatch.setattr("tools.voice_mode._import_audio",
+                            lambda: (MagicMock(), MagicMock()))
+
+        from tools.voice_mode import detect_audio_environment
+        result = detect_audio_environment()
+        assert result["available"] is False
+        assert any("Docker container" in w for w in result["warnings"])
+
     def test_wsl_without_pulse_blocks_voice(self, monkeypatch, tmp_path):
         """WSL without PULSE_SERVER should block voice mode."""
         monkeypatch.delenv("SSH_CLIENT", raising=False)
diff --git a/tools/voice_mode.py b/tools/voice_mode.py
index 66ecb242..a940957c 100644
--- a/tools/voice_mode.py
+++ b/tools/voice_mode.py
@@ -49,7 +49,7 @@ def _audio_available() -> bool:
         return False
 
 
-from hermes_constants import is_termux as _is_termux_environment
+from hermes_constants import is_container, is_termux as _is_termux_environment
 
 
 def _voice_capture_install_hint() -> str:
@@ -103,7 +103,6 @@ def detect_audio_environment() -> dict:
         warnings.append("Running over SSH -- no audio devices available")
 
     # Docker/Podman container detection
-    from hermes_constants import is_container
     if is_container():
         warnings.append("Running inside Docker container -- no audio devices")