fix: restore model_id for terminal batch retrieval

Co-authored-by: Ishaan Jaff <ishaan-jaff@users.noreply.github.com>

litellm/proxy/batches_endpoints/endpoints.py

@@ -406,6 +406,21 @@ async def retrieve_batch(  # noqa: PLR0915
             verbose_proxy_logger=verbose_proxy_logger,
         )
 
+        # DB-restored terminal batches can miss hidden_params.model_id.
+        # Restore it from the unified batch ID so post hooks can re-unify
+        # output/error file IDs before responding.
+        if response is not None and unified_batch_id:
+            current_hidden_params = getattr(response, "_hidden_params", {}) or {}
+            if not isinstance(current_hidden_params, dict):
+                current_hidden_params = {}
+            if not current_hidden_params.get("model_id"):
+                model_id_from_batch = get_model_id_from_unified_batch_id(unified_batch_id)
+                if model_id_from_batch:
+                    response._hidden_params = {
+                        **current_hidden_params,
+                        "model_id": model_id_from_batch,
+                    }
+
         # If batch is in a terminal state, return immediately.
         # Include "complete" (DB-normalized form of "completed").
         if response is not None and response.status in [

tests/test_litellm/enterprise/proxy/test_batch_retrieve_input_file_id.py

@@ -10,6 +10,7 @@ import base64
 import json
 
 import pytest
+from fastapi import Response
 from unittest.mock import AsyncMock, MagicMock, patch
 
 from litellm.proxy.openai_files_endpoints.common_utils import (
@@ -73,3 +74,84 @@ async def test_should_resolve_raw_input_file_id_to_unified():
         f"input_file_id should be unified '{B64_UNIFIED_INPUT_FILE_ID}', "
         f"got raw '{response.input_file_id}'"
     )
+
+
+@pytest.mark.asyncio
+async def test_should_restore_model_id_for_terminal_db_batch_before_post_hook():
+    """
+    When retrieve_batch returns a terminal batch directly from DB, it should
+    restore hidden_params.model_id from the unified batch ID before running
+    post_call_success_hook.
+    """
+    from litellm.proxy.batches_endpoints.endpoints import retrieve_batch
+    from litellm.types.utils import LiteLLMBatch
+
+    terminal_batch = LiteLLMBatch(
+        id=B64_UNIFIED_BATCH_ID,
+        completion_window="24h",
+        created_at=1700000000,
+        endpoint="/v1/chat/completions",
+        input_file_id=B64_UNIFIED_INPUT_FILE_ID,
+        object="batch",
+        status="completed",
+        output_file_id="file-raw-provider-output-123",
+    )
+    terminal_batch._hidden_params = {}
+
+    async def _post_call_success_hook(data, user_api_key_dict, response):
+        assert response._hidden_params.get("model_id") == "model-xyz"
+        response.output_file_id = "b64-unified-output-file-id"
+        return response
+
+    mock_proxy_logging_obj = MagicMock(
+        post_call_success_hook=AsyncMock(side_effect=_post_call_success_hook),
+        update_request_status=AsyncMock(),
+    )
+    mock_user_api_key_dict = MagicMock()
+    mock_user_api_key_dict.parent_otel_span = None
+    mock_user_api_key_dict.allowed_model_region = ""
+
+    mock_request = MagicMock()
+    mock_request.headers = {}
+    mock_request.query_params = {}
+    mock_request.url = MagicMock()
+    mock_request.url.port = 4000
+    mock_request.method = "GET"
+    mock_request.url.path = f"/v1/batches/{B64_UNIFIED_BATCH_ID}"
+
+    with (
+        patch(
+            "litellm.proxy.batches_endpoints.endpoints.ProxyBaseLLMRequestProcessing.common_processing_pre_call_logic",
+            new=AsyncMock(return_value=({"batch_id": B64_UNIFIED_BATCH_ID}, MagicMock())),
+        ),
+        patch(
+            "litellm.proxy.batches_endpoints.endpoints.ProxyBaseLLMRequestProcessing.get_custom_headers",
+            return_value={},
+        ),
+        patch(
+            "litellm.proxy.batches_endpoints.endpoints.get_batch_from_database",
+            new=AsyncMock(return_value=(MagicMock(), terminal_batch)),
+        ),
+        patch(
+            "litellm.proxy.batches_endpoints.endpoints.resolve_input_file_id_to_unified",
+            new=AsyncMock(),
+        ),
+        patch(
+            "litellm.proxy.batches_endpoints.endpoints.resolve_output_file_ids_to_unified",
+            new=AsyncMock(),
+        ),
+        patch("litellm.proxy.proxy_server.general_settings", {}),
+        patch("litellm.proxy.proxy_server.llm_router", MagicMock()),
+        patch("litellm.proxy.proxy_server.proxy_config", MagicMock()),
+        patch("litellm.proxy.proxy_server.version", "1.0.0"),
+        patch("litellm.proxy.proxy_server.proxy_logging_obj", mock_proxy_logging_obj),
+    ):
+        response = await retrieve_batch(
+            request=mock_request,
+            fastapi_response=Response(),
+            user_api_key_dict=mock_user_api_key_dict,
+            provider=None,
+            batch_id=B64_UNIFIED_BATCH_ID,
+        )
+
+    assert response.output_file_id == "b64-unified-output-file-id"