fix(mcp): accept integer progressToken in host progress capture

litellm/proxy/_experimental/mcp_server/server.py

@@ -716,7 +716,7 @@ def _capture_host_progress_callback(host_server) -> Optional[Callable]:
         if not (host_ctx and hasattr(host_ctx, "meta") and host_ctx.meta):
             return None
         host_token = getattr(host_ctx.meta, "progressToken", None)
-        if not (host_token and hasattr(host_ctx, "session") and host_ctx.session):
+        if host_token is None or not (hasattr(host_ctx, "session") and host_ctx.session):
             return None
         host_session = host_ctx.session
 
@@ -732,7 +732,7 @@ async def forward_progress(progress: float, total: Optional[float]):
             except Exception as e:
                 verbose_logger.error(f"Failed to forward progress to Host: {e}")
 
-        verbose_logger.debug(f"Host progressToken captured: {host_token[:8]}...")
+        verbose_logger.debug(f"Host progressToken captured: {str(host_token)[:8]}...")
         return forward_progress
 
     async def _build_virtual_call_logging_obj(

tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_tool_search.py

@@ -789,6 +789,47 @@ def test_returns_callable_when_token_present(self) -> None:
         host.request_context.session = MagicMock()
         assert callable(_capture_host_progress_callback(host))
 
+    def test_returns_callable_when_token_is_integer(self) -> None:
+        from litellm.proxy._experimental.mcp_server.server import (
+            _capture_host_progress_callback,
+        )
+
+        host = MagicMock()
+        host.request_context.meta.progressToken = 12345
+        host.request_context.session = MagicMock()
+        assert callable(_capture_host_progress_callback(host))
+
+    def test_returns_callable_when_token_is_zero(self) -> None:
+        from litellm.proxy._experimental.mcp_server.server import (
+            _capture_host_progress_callback,
+        )
+
+        host = MagicMock()
+        host.request_context.meta.progressToken = 0
+        host.request_context.session = MagicMock()
+        assert callable(_capture_host_progress_callback(host))
+
+    @pytest.mark.asyncio
+    async def test_forwarded_progress_token_preserves_integer_value(self) -> None:
+        from litellm.proxy._experimental.mcp_server.server import (
+            _capture_host_progress_callback,
+        )
+
+        host = MagicMock()
+        host.request_context.meta.progressToken = 12345
+        session = AsyncMock()
+        host.request_context.session = session
+
+        callback = _capture_host_progress_callback(host)
+        assert callback is not None
+        await callback(0.5, 1.0)
+
+        session.send_progress_notification.assert_awaited_once_with(
+            progress_token=12345,
+            progress=0.5,
+            total=1.0,
+        )
+
 
 class TestHandleListToolsVirtual:
     """Covers the protocol list_tools early-return when the flag is enabled."""