diff --git a/solara/server/esm.py b/solara/server/esm.py
index e5f29cb23..bbae33036 100644
--- a/solara/server/esm.py
+++ b/solara/server/esm.py
@@ -2,15 +2,22 @@
 # in the future, we may want to move the esm features of ipyreact
 # into a separate package, and then we can import it unconditionally
 import logging
+import threading
+from collections import defaultdict
 from pathlib import Path
 from typing import Dict, List, Tuple, Union
 
 import ipyreact.importmap
 import ipyreact.module
 
+from solara.server import kernel_context
+
 logger = logging.getLogger("solara.server.esm")
+lock = threading.Lock()
 
 _modules: Dict[str, Tuple[Union[str, Path], List[str]]] = {}
+_modules_added_per_kernel: Dict[str, Dict[str, ipyreact.module.Module]] = defaultdict(dict)
+_import_map_per_kernel: Dict[str, ipyreact.importmap.ImportMap] = {}
 
 
 # in solara server, we'll monkey patch ipyreact.module with this
@@ -29,10 +36,20 @@ def get_module_names():
 
 
 def create_modules():
+    kernel_id = kernel_context.get_current_context().id
+    _modules_added = _modules_added_per_kernel[kernel_id]
     logger.info("define modules %s", _modules)
     widgets = {}
-    for name, (module, dependencies) in _modules.items():
-        widgets[name] = create_module(name, module, dependencies=dependencies)
+    with lock:
+        for name, (module, dependencies) in _modules.items():
+            if name not in _modules_added:
+                _modules_added[name] = create_module(name, module, dependencies=dependencies)
+                logger.info("create module %s %s %s", name, module, dependencies)
+            else:
+                _modules_added[name].code = module if not isinstance(module, Path) else module.read_text(encoding="utf8")
+                _modules_added[name].dependencies = dependencies
+                logger.info("update module %s %s %s", name, module, dependencies)
+            widgets[name] = _modules_added[name]
     return widgets
 
 
@@ -41,5 +58,12 @@ def create_module(name, module: Union[str, Path], dependencies: List[str]):
 
 
 def create_import_map():
-    logger.info("create import map %s", ipyreact.importmap._effective_import_map)
-    return ipyreact.importmap.ImportMap(import_map=ipyreact.importmap._effective_import_map)
+    kernel_id = kernel_context.get_current_context().id
+    with lock:
+        if kernel_id not in _import_map_per_kernel:
+            _import_map_per_kernel[kernel_id] = ipyreact.importmap.ImportMap(import_map=ipyreact.importmap._effective_import_map)
+            logger.info("create import map %s", ipyreact.importmap._effective_import_map)
+        else:
+            _import_map_per_kernel[kernel_id].import_map = ipyreact.importmap._effective_import_map
+            logger.info("update import map %s", ipyreact.importmap._effective_import_map)
+    return