diff --git a/homeassistant/components/google_generative_ai_conversation/config_flow.py b/homeassistant/components/google_generative_ai_conversation/config_flow.py
index 9048304a006..0572c63085a 100644
--- a/homeassistant/components/google_generative_ai_conversation/config_flow.py
+++ b/homeassistant/components/google_generative_ai_conversation/config_flow.py
@@ -305,10 +305,11 @@ async def google_generative_ai_config_option_schema(
         )
         for api in llm.async_get_apis(hass)
     ]
-    if (suggested_llm_apis := options.get(CONF_LLM_HASS_API)) and isinstance(
-        suggested_llm_apis, str
-    ):
-        suggested_llm_apis = [suggested_llm_apis]
+    if suggested_llm_apis := options.get(CONF_LLM_HASS_API):
+        if isinstance(suggested_llm_apis, str):
+            suggested_llm_apis = [suggested_llm_apis]
+        known_apis = {api.id for api in llm.async_get_apis(hass)}
+        suggested_llm_apis = [api for api in suggested_llm_apis if api in known_apis]
 
     if is_new:
         if CONF_NAME in options:
diff --git a/tests/components/google_generative_ai_conversation/test_config_flow.py b/tests/components/google_generative_ai_conversation/test_config_flow.py
index 52def1d06bb..7f5e5685ecb 100644
--- a/tests/components/google_generative_ai_conversation/test_config_flow.py
+++ b/tests/components/google_generative_ai_conversation/test_config_flow.py
@@ -707,3 +707,53 @@ async def test_reauth_flow(hass: HomeAssistant) -> None:
     assert hass.config_entries.async_entries(DOMAIN)[0].data == {"api_key": "1234"}
     assert len(mock_unload_entry.mock_calls) == 1
     assert len(mock_setup_entry.mock_calls) == 1
+
+
+@pytest.mark.parametrize(
+    ("current_llm_apis", "suggested_llm_apis", "expected_options"),
+    [
+        ("assist", ["assist"], ["assist"]),
+        (["assist"], ["assist"], ["assist"]),
+        ("non-existent", [], ["assist"]),
+        (["non-existent"], [], ["assist"]),
+        (["assist", "non-existent"], ["assist"], ["assist"]),
+    ],
+)
+async def test_reconfigure_conversation_subentry_llm_api_schema(
+    hass: HomeAssistant,
+    mock_config_entry: MockConfigEntry,
+    mock_init_component,
+    current_llm_apis: str | list[str],
+    suggested_llm_apis: list[str],
+    expected_options: list[str],
+) -> None:
+    """Test llm_hass_api field values when reconfiguring a conversation subentry."""
+    subentry = next(iter(mock_config_entry.subentries.values()))
+    hass.config_entries.async_update_subentry(
+        mock_config_entry,
+        subentry,
+        data={CONF_LLM_HASS_API: current_llm_apis},
+    )
+    await hass.async_block_till_done()
+
+    with patch(
+        "google.genai.models.AsyncModels.list",
+        return_value=get_models_pager(),
+    ):
+        subentry_flow = await mock_config_entry.start_subentry_reconfigure_flow(
+            hass, subentry.subentry_id
+        )
+
+    assert subentry_flow["type"] is FlowResultType.FORM
+    assert subentry_flow["step_id"] == "set_options"
+
+    # Only valid LLM APIs should be suggested and shown as options
+    schema = subentry_flow["data_schema"].schema
+    key = next(k for k in schema if k == CONF_LLM_HASS_API)
+    assert key.description
+    assert key.description.get("suggested_value") == suggested_llm_apis
+    field_schema = schema[key]
+    assert field_schema.config
+    assert [
+        opt["value"] for opt in field_schema.config.get("options")
+    ] == expected_options