diff --git a/tests/common.py b/tests/common.py
index 8bd45e4d7f8..3ec3f6d844c 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -1815,3 +1815,20 @@ async def snapshot_platform(
         state = hass.states.get(entity_entry.entity_id)
         assert state, f"State not found for {entity_entry.entity_id}"
         assert state == snapshot(name=f"{entity_entry.entity_id}-state")
+
+
+def reset_translation_cache(hass: HomeAssistant, components: list[str]) -> None:
+    """Reset translation cache for specified components.
+
+    Use this if you are mocking a core component (for example via
+    mock_integration), to ensure that the mocked translations are not
+    persisted in the shared session cache.
+    """
+    translations_cache = translation._async_get_translations_cache(hass)
+    for loaded_components in translations_cache.cache_data.loaded.values():
+        for component_to_unload in components:
+            loaded_components.discard(component_to_unload)
+    for loaded_categories in translations_cache.cache_data.cache.values():
+        for loaded_components in loaded_categories.values():
+            for component_to_unload in components:
+                loaded_components.pop(component_to_unload, None)
diff --git a/tests/components/conftest.py b/tests/components/conftest.py
index 4294c0c2912..5628a2b1aaf 100644
--- a/tests/components/conftest.py
+++ b/tests/components/conftest.py
@@ -827,9 +827,6 @@ async def check_translations(
             f"Unused ignore translations: {', '.join(unused_ignore)}. "
             "Please remove them from the ignore_translations fixture."
         )
-    for key, description in translation_errors.items():
-        if key.startswith("component.cloud.issues."):
-            # cloud tests are flaky
-            continue
+    for description in translation_errors.values():
         if description not in {"used", "unused"}:
             pytest.fail(description)
diff --git a/tests/components/tts/test_init.py b/tests/components/tts/test_init.py
index 80dff87eb9b..9d8dbf3ef94 100644
--- a/tests/components/tts/test_init.py
+++ b/tests/components/tts/test_init.py
@@ -45,6 +45,7 @@ from tests.common import (
     mock_integration,
     mock_platform,
     mock_restore_cache,
+    reset_translation_cache,
 )
 from tests.typing import ClientSessionGenerator, WebSocketGenerator
 
@@ -1988,3 +1989,6 @@ async def test_default_engine_prefer_cloud_entity(
     provider_engine = tts.async_resolve_engine(hass, "test")
     assert provider_engine == "test"
     assert tts.async_default_engine(hass) == "tts.cloud_tts_entity"
+
+    # Reset the `cloud` translations cache
+    reset_translation_cache(hass, ["cloud"])
diff --git a/tests/conftest.py b/tests/conftest.py
index b858073a5e4..c46ed0407e5 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1192,7 +1192,12 @@ def mock_get_source_ip() -> Generator[_patch]:
 
 @pytest.fixture(autouse=True, scope="session")
 def translations_once() -> Generator[_patch]:
-    """Only load translations once per session."""
+    """Only load translations once per session.
+
+    Warning: having this as a session fixture can cause issues with tests that
+    create mock integrations, overriding the real integration translations
+    with empty ones. Translations should be reset after such tests (see #131628)
+    """
     cache = _TranslationsCacheData({}, {})
     patcher = patch(
         "homeassistant.helpers.translation._TranslationsCacheData",