fix: Indefinitely loading KB page for errors (#12295)

* fix indefinitely loading KB page

* [autofix.ci] apply automated fixes

* retry for 5XX error

* [autofix.ci] apply automated fixes

* improved testcase name

---------

Co-authored-by: Olayinka Adelakun <olayinkaadelakun@mac.war.can.ibm.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Carlos Coelho <80289056+carlosrcoelho@users.noreply.github.com>
Co-authored-by: Olayinka Adelakun <olayinkaadelakun@Olayinkas-MacBook-Pro.local>

src/backend/base/langflow/api/v1/knowledge_bases.py

@@ -552,6 +552,7 @@ async def get_knowledge_base_chunks(
     search: Annotated[str, Query(description="Filter chunks whose text contains this substring")] = "",
 ) -> PaginatedChunkResponse:
     """Get chunks from a specific knowledge base with pagination."""
+    kb_path: Path | None = None
     try:
         kb_path = _resolve_kb_path(kb_name, current_user)
 
@@ -631,7 +632,8 @@ async def get_knowledge_base_chunks(
     finally:
         client = None
         chroma = None
-        KBStorageHelper.release_chroma_resources(kb_path)
+        if kb_path is not None:
+            KBStorageHelper.release_chroma_resources(kb_path)
 
 
 @router.delete("/{kb_name}", status_code=HTTPStatus.OK)

src/backend/tests/unit/test_knowledge_bases_api.py

@@ -694,6 +694,20 @@ class TestKnowledgeBaseAPI:
         assert data["page"] == 2
         mock_collection.get.assert_called_with(include=["documents", "metadatas"], limit=10, offset=10)
 
+    @patch("langflow.api.v1.knowledge_bases.KBStorageHelper.get_root_path")
+    async def test_get_chunks_non_existent_kb_returns_404(
+        self,
+        mock_root,
+        client: AsyncClient,
+        logged_in_headers,
+        tmp_path,
+    ):
+        mock_root.return_value = tmp_path
+
+        response = await client.get("api/v1/knowledge_bases/MissingKB/chunks", headers=logged_in_headers)
+
+        assert response.status_code == 404
+
 
 class TestPerformIngestionTask:
     """Tests for the internal KBIngestionHelper.perform_ingestion background task."""

src/frontend/src/controllers/API/queries/knowledge-bases/use-get-knowledge-base-chunks.ts

@@ -63,6 +63,13 @@ export const useGetKnowledgeBaseChunks: useQueryFunctionType<
     getChunksFn,
     {
       enabled: !!params?.kb_name,
+      retry: (failureCount, error: any) => {
+        const status = error?.response?.status;
+        if (typeof status === "number") {
+          return status >= 500 && failureCount < 3;
+        }
+        return failureCount < 3;
+      },
       refetchOnWindowFocus: false,
       ...options,
     },

src/frontend/src/pages/MainPage/pages/knowledgePage/sourceChunksPage/__tests__/SourceChunksPage.test.tsx

@@ -93,6 +93,19 @@ describe("SourceChunksPage", () => {
       render(<SourceChunksPage />);
       expect(screen.getByText("Failed to load chunks")).toBeInTheDocument();
     });
+
+    it("shows error message on 4xx errors", () => {
+      mockGetChunks.mockReturnValue({
+        isLoading: false,
+        isError: true,
+        data: undefined,
+        error: { response: { status: 404 } },
+      });
+
+      render(<SourceChunksPage />);
+
+      expect(screen.getByText("Failed to load chunks")).toBeInTheDocument();
+    });
   });
 
   describe("Empty state", () => {