diff --git a/gateway/run.py b/gateway/run.py
index 8b40bf62..2e8f393b 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -9404,11 +9404,17 @@ class GatewayRunner:
 
     @classmethod
     def _extract_cache_busting_config(cls, user_config: dict | None) -> dict:
-        """Pull the subset of config values that must bust the agent cache.
+        """Pull values that must bust the cached agent.
 
-        Returns a flat dict keyed by 'section.key'.  Missing keys and
-        non-dict sections yield None values, which still contribute to
-        the signature (so 'absent' vs 'present-and-null' differ).
+        Returns a flat dict keyed by 'section.key'.  Missing config keys and
+        non-dict sections yield None values, which still contribute to the
+        signature (so 'absent' vs 'present-and-null' differ).
+
+        The live tool registry generation is included too.  MCP reloads and
+        dynamic MCP tool-list changes mutate the registry without necessarily
+        changing config.yaml.  Cached AIAgent instances freeze their tool
+        schemas at construction time, so a registry generation change must
+        rebuild the agent before the next turn.
         """
         out: Dict[str, Any] = {}
         cfg = user_config if isinstance(user_config, dict) else {}
@@ -9418,6 +9424,12 @@ class GatewayRunner:
                 out[f"{section}.{key}"] = section_val.get(key)
             else:
                 out[f"{section}.{key}"] = None
+        try:
+            from tools.registry import registry
+
+            out["tools.registry_generation"] = getattr(registry, "_generation", None)
+        except Exception:
+            out["tools.registry_generation"] = None
         return out
 
     @staticmethod
diff --git a/tests/gateway/test_agent_cache.py b/tests/gateway/test_agent_cache.py
index f3e63b07..abf0ce34 100644
--- a/tests/gateway/test_agent_cache.py
+++ b/tests/gateway/test_agent_cache.py
@@ -170,6 +170,22 @@ class TestAgentConfigSignature:
         )
         assert sig_a == sig_b
 
+    def test_tool_registry_generation_change_busts_cache(self):
+        """MCP reloads mutate the tool registry, so cached agents must rebuild."""
+        from gateway.run import GatewayRunner
+
+        runtime = {"api_key": "k", "base_url": "u", "provider": "p"}
+        sig_before = GatewayRunner._agent_config_signature(
+            "m", runtime, ["telegram"], "",
+            cache_keys={"tools.registry_generation": 10},
+        )
+        sig_after = GatewayRunner._agent_config_signature(
+            "m", runtime, ["telegram"], "",
+            cache_keys={"tools.registry_generation": 11},
+        )
+
+        assert sig_before != sig_after
+
 
 class TestExtractCacheBustingConfig:
     """Verify _extract_cache_busting_config pulls the documented subset of
@@ -229,6 +245,17 @@ class TestExtractCacheBustingConfig:
         out = GatewayRunner._extract_cache_busting_config(None)
         for section, key in GatewayRunner._CACHE_BUSTING_CONFIG_KEYS:
             assert out[f"{section}.{key}"] is None
+        assert "tools.registry_generation" in out
+
+    def test_extract_includes_live_tool_registry_generation(self, monkeypatch):
+        from gateway.run import GatewayRunner
+        from tools.registry import registry
+
+        monkeypatch.setattr(registry, "_generation", 12345)
+
+        out = GatewayRunner._extract_cache_busting_config({})
+
+        assert out["tools.registry_generation"] == 12345
 
     def test_full_round_trip_busts_cache_on_real_edit(self):
         """End-to-end: simulate a config edit on main and verify the