diff --git a/agent/agent_runtime_helpers.py b/agent/agent_runtime_helpers.py
index 73f3cba435df..de5fe909153b 100644
--- a/agent/agent_runtime_helpers.py
+++ b/agent/agent_runtime_helpers.py
@@ -1619,6 +1619,7 @@ def invoke_tool(agent, function_name: str, function_args: dict, effective_task_i
             from hermes_cli.plugins import get_pre_tool_call_block_message
             block_message = get_pre_tool_call_block_message(
                 function_name, function_args, task_id=effective_task_id or "",
+                session_id=agent.session_id or "",
             )
         except Exception:
             pass
diff --git a/agent/tool_executor.py b/agent/tool_executor.py
index 358c1a0a8f70..d26d943d9916 100644
--- a/agent/tool_executor.py
+++ b/agent/tool_executor.py
@@ -212,6 +212,7 @@ def execute_tool_calls_concurrent(agent, assistant_message, messages: list, effe
                 from hermes_cli.plugins import get_pre_tool_call_block_message
                 block_message = get_pre_tool_call_block_message(
                     function_name, function_args, task_id=effective_task_id or "",
+                    session_id=agent.session_id or "",
                 )
             except Exception:
                 block_message = None
@@ -589,6 +590,7 @@ def execute_tool_calls_sequential(agent, assistant_message, messages: list, effe
                 from hermes_cli.plugins import get_pre_tool_call_block_message
                 _block_msg = get_pre_tool_call_block_message(
                     function_name, function_args, task_id=effective_task_id or "",
+                    session_id=agent.session_id or "",
                 )
             except Exception:
                 pass
diff --git a/tests/hermes_cli/test_plugins.py b/tests/hermes_cli/test_plugins.py
index b78e8b2921d0..248267fac424 100644
--- a/tests/hermes_cli/test_plugins.py
+++ b/tests/hermes_cli/test_plugins.py
@@ -532,6 +532,38 @@ def test_first_valid_block_wins(self, monkeypatch):
         )
         assert get_pre_tool_call_block_message("terminal", {}) == "first blocker"
 
+    def test_session_id_forwarded_to_hook(self, monkeypatch):
+        """Verify session_id kwarg reaches the plugin hook (regression test)."""
+        captured_kwargs = {}
+
+        def _capture_hook(hook_name, **kwargs):
+            captured_kwargs.update(kwargs)
+            return []
+
+        monkeypatch.setattr(
+            "hermes_cli.plugins.invoke_hook",
+            _capture_hook,
+        )
+        get_pre_tool_call_block_message(
+            "terminal", {}, task_id="t1", session_id="sess-42",
+        )
+        assert captured_kwargs.get("session_id") == "sess-42"
+
+    def test_session_id_defaults_to_empty_string(self, monkeypatch):
+        """When session_id is omitted, hook receives empty string default."""
+        captured_kwargs = {}
+
+        def _capture_hook(hook_name, **kwargs):
+            captured_kwargs.update(kwargs)
+            return []
+
+        monkeypatch.setattr(
+            "hermes_cli.plugins.invoke_hook",
+            _capture_hook,
+        )
+        get_pre_tool_call_block_message("todo", {}, task_id="t1")
+        assert captured_kwargs.get("session_id") == ""
+
 
 class TestThreadToolWhitelist:
     """Tests for the thread-local tool whitelist used by background review forks."""