diff --git a/tests/tools/test_tool_backend_helpers.py b/tests/tools/test_tool_backend_helpers.py
new file mode 100644
index 0000000000..faaed9c5e0
--- /dev/null
+++ b/tests/tools/test_tool_backend_helpers.py
@@ -0,0 +1,287 @@
+"""Unit tests for tools/tool_backend_helpers.py.
+
+Tests cover:
+- managed_nous_tools_enabled() feature flag
+- normalize_browser_cloud_provider() coercion
+- coerce_modal_mode() / normalize_modal_mode() validation
+- has_direct_modal_credentials() detection
+- resolve_modal_backend_state() backend selection matrix
+- resolve_openai_audio_api_key() priority chain
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from tools.tool_backend_helpers import (
+    coerce_modal_mode,
+    has_direct_modal_credentials,
+    managed_nous_tools_enabled,
+    normalize_browser_cloud_provider,
+    normalize_modal_mode,
+    resolve_modal_backend_state,
+    resolve_openai_audio_api_key,
+)
+
+
+# ---------------------------------------------------------------------------
+# managed_nous_tools_enabled
+# ---------------------------------------------------------------------------
+class TestManagedNousToolsEnabled:
+    """Feature flag driven by HERMES_ENABLE_NOUS_MANAGED_TOOLS."""
+
+    def test_disabled_by_default(self, monkeypatch):
+        monkeypatch.delenv("HERMES_ENABLE_NOUS_MANAGED_TOOLS", raising=False)
+        assert managed_nous_tools_enabled() is False
+
+    @pytest.mark.parametrize("val", ["1", "true", "True", "yes"])
+    def test_enabled_when_truthy(self, monkeypatch, val):
+        monkeypatch.setenv("HERMES_ENABLE_NOUS_MANAGED_TOOLS", val)
+        assert managed_nous_tools_enabled() is True
+
+    @pytest.mark.parametrize("val", ["0", "false", "no", ""])
+    def test_disabled_when_falsy(self, monkeypatch, val):
+        monkeypatch.setenv("HERMES_ENABLE_NOUS_MANAGED_TOOLS", val)
+        assert managed_nous_tools_enabled() is False
+
+
+# ---------------------------------------------------------------------------
+# normalize_browser_cloud_provider
+# ---------------------------------------------------------------------------
+class TestNormalizeBrowserCloudProvider:
+    """Coerce arbitrary input to a lowercase browser provider key."""
+
+    def test_none_returns_default(self):
+        assert normalize_browser_cloud_provider(None) == "local"
+
+    def test_empty_string_returns_default(self):
+        assert normalize_browser_cloud_provider("") == "local"
+
+    def test_whitespace_only_returns_default(self):
+        assert normalize_browser_cloud_provider("   ") == "local"
+
+    def test_known_provider_normalized(self):
+        assert normalize_browser_cloud_provider("BrowserBase") == "browserbase"
+
+    def test_strips_whitespace(self):
+        assert normalize_browser_cloud_provider("  Local  ") == "local"
+
+    def test_integer_coerced(self):
+        result = normalize_browser_cloud_provider(42)
+        assert isinstance(result, str)
+        assert result == "42"
+
+
+# ---------------------------------------------------------------------------
+# coerce_modal_mode / normalize_modal_mode
+# ---------------------------------------------------------------------------
+class TestCoerceModalMode:
+    """Validate and coerce the requested modal execution mode."""
+
+    @pytest.mark.parametrize("value", ["auto", "direct", "managed"])
+    def test_valid_modes_passthrough(self, value):
+        assert coerce_modal_mode(value) == value
+
+    def test_none_returns_auto(self):
+        assert coerce_modal_mode(None) == "auto"
+
+    def test_empty_string_returns_auto(self):
+        assert coerce_modal_mode("") == "auto"
+
+    def test_whitespace_only_returns_auto(self):
+        assert coerce_modal_mode("   ") == "auto"
+
+    def test_uppercase_normalized(self):
+        assert coerce_modal_mode("DIRECT") == "direct"
+
+    def test_mixed_case_normalized(self):
+        assert coerce_modal_mode("Managed") == "managed"
+
+    def test_invalid_mode_falls_back_to_auto(self):
+        assert coerce_modal_mode("invalid") == "auto"
+        assert coerce_modal_mode("cloud") == "auto"
+
+    def test_strips_whitespace(self):
+        assert coerce_modal_mode("  managed  ") == "managed"
+
+
+class TestNormalizeModalMode:
+    """normalize_modal_mode is an alias for coerce_modal_mode."""
+
+    def test_delegates_to_coerce(self):
+        assert normalize_modal_mode("direct") == coerce_modal_mode("direct")
+        assert normalize_modal_mode(None) == coerce_modal_mode(None)
+        assert normalize_modal_mode("bogus") == coerce_modal_mode("bogus")
+
+
+# ---------------------------------------------------------------------------
+# has_direct_modal_credentials
+# ---------------------------------------------------------------------------
+class TestHasDirectModalCredentials:
+    """Detect Modal credentials via env vars or config file."""
+
+    def test_no_env_no_file(self, monkeypatch, tmp_path):
+        monkeypatch.delenv("MODAL_TOKEN_ID", raising=False)
+        monkeypatch.delenv("MODAL_TOKEN_SECRET", raising=False)
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is False
+
+    def test_both_env_vars_set(self, monkeypatch, tmp_path):
+        monkeypatch.setenv("MODAL_TOKEN_ID", "id-123")
+        monkeypatch.setenv("MODAL_TOKEN_SECRET", "sec-456")
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is True
+
+    def test_only_token_id_not_enough(self, monkeypatch, tmp_path):
+        monkeypatch.setenv("MODAL_TOKEN_ID", "id-123")
+        monkeypatch.delenv("MODAL_TOKEN_SECRET", raising=False)
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is False
+
+    def test_only_token_secret_not_enough(self, monkeypatch, tmp_path):
+        monkeypatch.delenv("MODAL_TOKEN_ID", raising=False)
+        monkeypatch.setenv("MODAL_TOKEN_SECRET", "sec-456")
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is False
+
+    def test_config_file_present(self, monkeypatch, tmp_path):
+        monkeypatch.delenv("MODAL_TOKEN_ID", raising=False)
+        monkeypatch.delenv("MODAL_TOKEN_SECRET", raising=False)
+        (tmp_path / ".modal.toml").touch()
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is True
+
+    def test_env_vars_take_priority_over_file(self, monkeypatch, tmp_path):
+        monkeypatch.setenv("MODAL_TOKEN_ID", "id-123")
+        monkeypatch.setenv("MODAL_TOKEN_SECRET", "sec-456")
+        (tmp_path / ".modal.toml").touch()
+        with patch.object(Path, "home", return_value=tmp_path):
+            assert has_direct_modal_credentials() is True
+
+
+# ---------------------------------------------------------------------------
+# resolve_modal_backend_state
+# ---------------------------------------------------------------------------
+class TestResolveModalBackendState:
+    """Full matrix of direct vs managed Modal backend selection."""
+
+    @staticmethod
+    def _resolve(monkeypatch, mode, *, has_direct, managed_ready, nous_enabled=False):
+        """Helper to call resolve_modal_backend_state with feature flag control."""
+        if nous_enabled:
+            monkeypatch.setenv("HERMES_ENABLE_NOUS_MANAGED_TOOLS", "1")
+        else:
+            monkeypatch.setenv("HERMES_ENABLE_NOUS_MANAGED_TOOLS", "")
+        return resolve_modal_backend_state(
+            mode, has_direct=has_direct, managed_ready=managed_ready
+        )
+
+    # --- auto mode ---
+
+    def test_auto_prefers_managed_when_available(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=True, managed_ready=True, nous_enabled=True)
+        assert result["selected_backend"] == "managed"
+
+    def test_auto_falls_back_to_direct(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=True, managed_ready=False, nous_enabled=True)
+        assert result["selected_backend"] == "direct"
+
+    def test_auto_no_backends_available(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=False, managed_ready=False)
+        assert result["selected_backend"] is None
+
+    def test_auto_managed_ready_but_nous_disabled(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=True, managed_ready=True, nous_enabled=False)
+        assert result["selected_backend"] == "direct"
+
+    def test_auto_nothing_when_only_managed_and_nous_disabled(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=False, managed_ready=True, nous_enabled=False)
+        assert result["selected_backend"] is None
+
+    # --- direct mode ---
+
+    def test_direct_selects_direct_when_available(self, monkeypatch):
+        result = self._resolve(monkeypatch, "direct", has_direct=True, managed_ready=True, nous_enabled=True)
+        assert result["selected_backend"] == "direct"
+
+    def test_direct_none_when_no_credentials(self, monkeypatch):
+        result = self._resolve(monkeypatch, "direct", has_direct=False, managed_ready=True, nous_enabled=True)
+        assert result["selected_backend"] is None
+
+    # --- managed mode ---
+
+    def test_managed_selects_managed_when_ready_and_enabled(self, monkeypatch):
+        result = self._resolve(monkeypatch, "managed", has_direct=True, managed_ready=True, nous_enabled=True)
+        assert result["selected_backend"] == "managed"
+
+    def test_managed_none_when_not_ready(self, monkeypatch):
+        result = self._resolve(monkeypatch, "managed", has_direct=True, managed_ready=False, nous_enabled=True)
+        assert result["selected_backend"] is None
+
+    def test_managed_blocked_when_nous_disabled(self, monkeypatch):
+        result = self._resolve(monkeypatch, "managed", has_direct=True, managed_ready=True, nous_enabled=False)
+        assert result["selected_backend"] is None
+        assert result["managed_mode_blocked"] is True
+
+    # --- return structure ---
+
+    def test_return_dict_keys(self, monkeypatch):
+        result = self._resolve(monkeypatch, "auto", has_direct=True, managed_ready=False)
+        expected_keys = {
+            "requested_mode",
+            "mode",
+            "has_direct",
+            "managed_ready",
+            "managed_mode_blocked",
+            "selected_backend",
+        }
+        assert set(result.keys()) == expected_keys
+
+    def test_passthrough_flags(self, monkeypatch):
+        result = self._resolve(monkeypatch, "direct", has_direct=True, managed_ready=False)
+        assert result["requested_mode"] == "direct"
+        assert result["mode"] == "direct"
+        assert result["has_direct"] is True
+        assert result["managed_ready"] is False
+
+    # --- invalid mode falls back to auto ---
+
+    def test_invalid_mode_treated_as_auto(self, monkeypatch):
+        result = self._resolve(monkeypatch, "bogus", has_direct=True, managed_ready=False)
+        assert result["requested_mode"] == "auto"
+        assert result["mode"] == "auto"
+
+
+# ---------------------------------------------------------------------------
+# resolve_openai_audio_api_key
+# ---------------------------------------------------------------------------
+class TestResolveOpenaiAudioApiKey:
+    """Priority: VOICE_TOOLS_OPENAI_KEY > OPENAI_API_KEY."""
+
+    def test_voice_key_preferred(self, monkeypatch):
+        monkeypatch.setenv("VOICE_TOOLS_OPENAI_KEY", "voice-key")
+        monkeypatch.setenv("OPENAI_API_KEY", "general-key")
+        assert resolve_openai_audio_api_key() == "voice-key"
+
+    def test_falls_back_to_openai_key(self, monkeypatch):
+        monkeypatch.delenv("VOICE_TOOLS_OPENAI_KEY", raising=False)
+        monkeypatch.setenv("OPENAI_API_KEY", "general-key")
+        assert resolve_openai_audio_api_key() == "general-key"
+
+    def test_empty_voice_key_falls_back(self, monkeypatch):
+        monkeypatch.setenv("VOICE_TOOLS_OPENAI_KEY", "")
+        monkeypatch.setenv("OPENAI_API_KEY", "general-key")
+        assert resolve_openai_audio_api_key() == "general-key"
+
+    def test_no_keys_returns_empty(self, monkeypatch):
+        monkeypatch.delenv("VOICE_TOOLS_OPENAI_KEY", raising=False)
+        monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+        assert resolve_openai_audio_api_key() == ""
+
+    def test_strips_whitespace(self, monkeypatch):
+        monkeypatch.setenv("VOICE_TOOLS_OPENAI_KEY", "  voice-key  ")
+        monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+        assert resolve_openai_audio_api_key() == "voice-key"