diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index e2f5bf6dcf..17b72dda8f 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -2333,6 +2333,7 @@ async def _setup_context_for_resumed_invocation(
       ValueError: If the session has no events to resume; If no user message is
         available for resuming the invocation; Or if the app is not resumable.
     """
+
     if not session.events:
       raise ValueError(f'Session {session.id} has no events to resume.')
 
@@ -2340,6 +2341,22 @@ async def _setup_context_for_resumed_invocation(
     user_message = new_message or self._find_user_message_for_invocation(
         session.events, invocation_id
     )
+
+    # === [START FIX] Fallback mechanism ===
+    if not user_message and session.events:
+      # If exact invocation match failed, try to find the latest user message
+      # This handles cases where invocation IDs might have drifted or for generic resume
+      for event in reversed(session.events):
+        if event.author == 'user' and event.content:
+          logger.warning(
+              'Could not find user message for invocation %s. Falling back to '
+              'the latest user message in the session.',
+              invocation_id,
+          )
+          user_message = event.content
+          break
+    # === [END FIX] ===
+
     if not user_message:
       raise ValueError(
           f'No user message available for resuming invocation: {invocation_id}'
diff --git a/tests/unittests/test_import_loading.py b/tests/unittests/test_import_loading.py
index 1aad559059..49e9623e3a 100644
--- a/tests/unittests/test_import_loading.py
+++ b/tests/unittests/test_import_loading.py
@@ -82,8 +82,8 @@
     'typing_inspection',
     'zstandard',
     # google.genai.types annotates optional fields with aiohttp and Pillow
-    # types and imports whichever of the two the environment happens to have.
-    # No ADK module imports either one, so these are absent in some installs.
+    # types and probes for httpx2 compatibility. It imports whichever packages
+    # the environment happens to have, so these are absent in some installs.
     'PIL',
     'aiohappyeyeballs',
     'aiohttp',
@@ -91,6 +91,7 @@
     'attr',
     'defusedxml',
     'frozenlist',
+    'httpx2',
     'multidict',
     'propcache',
     'yarl',