diff --git a/src/openjarvis/system.py b/src/openjarvis/system.py
index eda3ef5a..a9ade2f8 100644
--- a/src/openjarvis/system.py
+++ b/src/openjarvis/system.py
@@ -43,6 +43,7 @@ class JarvisSystem:
     session_store: Optional[Any] = None  # SessionStore
     capability_policy: Optional[Any] = None  # CapabilityPolicy
     audit_logger: Optional[Any] = None  # AuditLogger
+    boundary_guard: Optional[Any] = None  # BoundaryGuard
     operator_manager: Optional[Any] = None  # OperatorManager
     agent_manager: Optional[Any] = None  # AgentManager
     agent_scheduler: Optional[Any] = None  # AgentScheduler
diff --git a/src/openjarvis/tools/_stubs.py b/src/openjarvis/tools/_stubs.py
index b8a3d4fe..127b4f3b 100644
--- a/src/openjarvis/tools/_stubs.py
+++ b/src/openjarvis/tools/_stubs.py
@@ -101,6 +101,7 @@ class ToolExecutor:
         default_timeout: float = 30.0,
         capability_policy: Optional[Any] = None,
         agent_id: str = "",
+        boundary_guard: Optional[Any] = None,
     ) -> None:
         self._tools: Dict[str, BaseTool] = {t.spec.name: t for t in tools}
         self._bus = bus
@@ -109,6 +110,7 @@ class ToolExecutor:
         self._default_timeout = default_timeout
         self._capability_policy = capability_policy
         self._agent_id = agent_id
+        self._boundary_guard = boundary_guard
 
     def execute(self, tool_call: ToolCall) -> ToolResult:
         """Parse arguments, dispatch to tool, measure latency, emit events."""
@@ -130,6 +132,22 @@ class ToolExecutor:
                 success=False,
             )
 
+        # Boundary guard: scan external tool arguments
+        if (
+            self._boundary_guard is not None
+            and not getattr(tool, "is_local", True)
+        ):
+            try:
+                tool_call = self._boundary_guard.check_outbound(tool_call)
+                # Re-parse arguments after potential redaction
+                params = json.loads(tool_call.arguments) if tool_call.arguments else {}
+            except Exception as exc:
+                return ToolResult(
+                    tool_name=tool_call.name,
+                    content=f"Security block: {exc}",
+                    success=False,
+                )
+
         # RBAC capability check
         if self._capability_policy and tool.spec.required_capabilities:
             for cap in tool.spec.required_capabilities:
diff --git a/tests/security/test_boundary_guard.py b/tests/security/test_boundary_guard.py
index 8bfd6dcf..bdcb31ce 100644
--- a/tests/security/test_boundary_guard.py
+++ b/tests/security/test_boundary_guard.py
@@ -160,3 +160,68 @@ class TestToolTagging:
         from openjarvis.tools.calculator import CalculatorTool
 
         assert CalculatorTool.is_local is True
+
+
+class TestToolExecutorBoundaryIntegration:
+    """ToolExecutor should use BoundaryGuard for external tool calls."""
+
+    def _make_executor(self, boundary_guard=None):
+        from openjarvis.tools._stubs import BaseTool, ToolExecutor, ToolSpec
+
+        class FakeExternalTool(BaseTool):
+            tool_id = "fake_external"
+            is_local = False
+
+            @property
+            def spec(self):
+                return ToolSpec(
+                    name="fake_external",
+                    description="test",
+                    parameters={
+                        "type": "object",
+                        "properties": {"q": {"type": "string"}},
+                    },
+                )
+
+            def execute(self, **params):
+                from openjarvis.core.types import ToolResult
+
+                return ToolResult(
+                    tool_name="fake_external",
+                    content=f"result for {params.get('q', '')}",
+                    success=True,
+                )
+
+        return ToolExecutor(
+            tools=[FakeExternalTool()],
+            boundary_guard=boundary_guard,
+        )
+
+    def test_external_tool_args_scanned(self) -> None:
+        from openjarvis.core.types import ToolCall
+        from openjarvis.security.boundary import BoundaryGuard
+
+        guard = BoundaryGuard(mode="redact")
+        executor = self._make_executor(boundary_guard=guard)
+
+        tc = ToolCall(
+            id="t1",
+            name="fake_external",
+            arguments=(
+                '{"q": "my key is sk-proj-abc123def456ghi789jkl012mno345pqr678stu"}'
+            ),
+        )
+        result = executor.execute(tc)
+        assert "sk-proj-" not in result.content
+
+    def test_no_guard_passes_through(self) -> None:
+        from openjarvis.core.types import ToolCall
+
+        executor = self._make_executor(boundary_guard=None)
+        tc = ToolCall(
+            id="t2",
+            name="fake_external",
+            arguments='{"q": "sk-proj-abc123def456ghi789jkl012mno345pqr678stu"}',
+        )
+        result = executor.execute(tc)
+        assert "sk-proj-" in result.content