fix: keep SQLite session state numbers exact across updates

Merge #7426

PiperOrigin-RevId: 996043876

Author: donggyun112

src/google/adk/sessions/sqlite_session_service.py

@@ -52,12 +52,22 @@
 # Merges {delta} into {state} with dict.update() semantics: keys in the delta
 # always win with their delta value (including SQL NULL / JSON null), unlike
 # json_patch() which deep-merges dict values and treats null as "delete key".
+#
+# json_group_object writes a REAL with 15 significant digits, which rounds
+# floats such as 0.1 + 0.2 for every key in the row. A REAL is written with 17
+# digits when 15 do not read back as the same value, so floats round-trip.
 _MERGE_STATE_SQL = """
         SELECT json_group_object(
                  key,
                  CASE
                    WHEN type IN ('object','array') THEN json(value)
                    WHEN type IN ('true','false') THEN json(type)
+                   WHEN type = 'real' THEN json(
+                     CASE
+                       WHEN CAST(printf('%!.15g', value) AS REAL) = value
+                         THEN printf('%!.15g', value)
+                       ELSE printf('%!.17g', value)
+                     END)
                    ELSE value
                  END)
         FROM (

tests/unittests/sessions/test_session_service.py

@@ -1271,6 +1271,63 @@ async def test_user_state_none_valued_delta_is_stored_not_dropped(
   assert session1.state.get('user:pref') is None
 
 
+# Floats that need more than 15 significant digits to read back unchanged.
+_EXACT_NUMBERS = {
+    'ratio': 0.1 + 0.2,
+    'epoch_seconds': 1727500000.1234567,
+}
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('prefix', ['', 'user:', 'app:'])
+async def test_numbers_survive_unrelated_state_delta(session_service, prefix):
+  """Stored numbers read back unchanged after an unrelated state_delta."""
+  numbers = {prefix + key: value for key, value in _EXACT_NUMBERS.items()}
+  session = await session_service.create_session(
+      app_name='my_app', user_id='u1', session_id='s1', state=numbers
+  )
+  event = Event(
+      invocation_id='inv1',
+      author='user',
+      actions=EventActions(state_delta={prefix + 'other': 1}),
+  )
+  await session_service.append_event(session=session, event=event)
+
+  reloaded = await session_service.get_session(
+      app_name='my_app', user_id='u1', session_id='s1'
+  )
+
+  assert {key: reloaded.state[key] for key in numbers} == numbers
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('prefix', ['', 'user:', 'app:'])
+async def test_number_valued_state_delta_is_stored_exactly(
+    session_service, prefix
+):
+  """Numbers written by a state_delta read back unchanged."""
+  numbers = {prefix + key: value for key, value in _EXACT_NUMBERS.items()}
+  # Seed the scope so the delta is merged into existing state.
+  session = await session_service.create_session(
+      app_name='my_app',
+      user_id='u1',
+      session_id='s1',
+      state={prefix + 'seed': 1},
+  )
+  event = Event(
+      invocation_id='inv1',
+      author='user',
+      actions=EventActions(state_delta=numbers),
+  )
+  await session_service.append_event(session=session, event=event)
+
+  reloaded = await session_service.get_session(
+      app_name='my_app', user_id='u1', session_id='s1'
+  )
+
+  assert {key: reloaded.state[key] for key in numbers} == numbers
+
+
 @pytest.mark.asyncio
 async def test_temp_state_is_not_persisted_in_state_or_events(session_service):
   app_name = 'my_app'