fix: yield to event loop after each SSE write to flush socket

The for-await loop over OpenAI stream chunks runs synchronously when
data is buffered, causing res.write() calls to queue without flushing.
Add setImmediate yield after each progress event so the event loop
reaches its I/O phase and pushes data to the network immediately.

backend/src/routes/import.ts

@@ -60,6 +60,7 @@ router.post(
       res.setHeader('Cache-Control', 'no-cache');
       res.setHeader('Connection', 'keep-alive');
       res.setHeader('X-Accel-Buffering', 'no');
+      res.socket?.setNoDelay(true);
       res.flushHeaders();
 
       try {
@@ -79,12 +80,6 @@ router.post(
           return;
         }
 
-        sseWrite(res, {
-          stage: 'import',
-          progress: 88,
-          message: 'Импорт в базу данных...',
-        });
-
         const result = await importStatement(converted);
         if (isValidationError(result)) {
           sseWrite(res, {

backend/src/services/pdfToStatement.ts

@@ -137,7 +137,7 @@ export async function convertPdfToStatement(
     return {
       status: 502,
       error: 'BAD_GATEWAY',
-      message: 'Временная ошибка конвертации',
+      message: extractLlmErrorMessage(err),
     };
   }
 }
@@ -145,7 +145,14 @@ export async function convertPdfToStatement(
 export type ProgressStage = 'pdf' | 'llm' | 'import';
 export type OnProgress = (stage: ProgressStage, progress: number, message: string) => void;
 
-const EXPECTED_CHARS = 15_000;
+const LLM_PROGRESS_MIN = 10;
+const LLM_PROGRESS_MAX = 98;
+const LLM_PROGRESS_RANGE = LLM_PROGRESS_MAX - LLM_PROGRESS_MIN;
+const THROTTLE_MS = 300;
+
+function yieldToEventLoop(): Promise<void> {
+  return new Promise(resolve => setImmediate(resolve));
+}
 
 export async function convertPdfToStatementStreaming(
   buffer: Buffer,
@@ -160,6 +167,7 @@ export async function convertPdfToStatementStreaming(
   }
 
   onProgress('pdf', 2, 'Извлечение текста из PDF...');
+  await yieldToEventLoop();
 
   let text: string;
   try {
@@ -183,6 +191,7 @@ export async function convertPdfToStatementStreaming(
   }
 
   onProgress('pdf', 8, 'Текст извлечён, отправка в LLM...');
+  await yieldToEventLoop();
 
   const openai = new OpenAI({
     apiKey: config.llmApiKey,
@@ -202,22 +211,36 @@ export async function convertPdfToStatementStreaming(
       stream: true,
     });
 
+    const expectedChars = Math.max(2_000, Math.min(text.length * 2, 30_000));
+
     let accumulated = '';
     let charsReceived = 0;
+    let lastEmitTime = 0;
 
     for await (const chunk of stream) {
       const delta = chunk.choices[0]?.delta?.content;
       if (delta) {
         accumulated += delta;
         charsReceived += delta.length;
-        const llmProgress = Math.min(
-          85,
-          Math.round((charsReceived / EXPECTED_CHARS) * 75 + 10),
-        );
-        onProgress('llm', llmProgress, 'Конвертация через LLM...');
+
+        const now = Date.now();
+        if (now - lastEmitTime >= THROTTLE_MS) {
+          const ratio = Math.min(1, charsReceived / expectedChars);
+          const llmProgress = Math.min(
+            LLM_PROGRESS_MAX,
+            Math.round(ratio * LLM_PROGRESS_RANGE + LLM_PROGRESS_MIN),
+          );
+          onProgress('llm', llmProgress, 'Конвертация через LLM...');
+          lastEmitTime = now;
+          // Let the event loop flush socket writes to the network
+          await yieldToEventLoop();
+        }
       }
     }
 
+    onProgress('llm', LLM_PROGRESS_MAX, 'LLM завершил, обработка результата...');
+    await yieldToEventLoop();
+
     const content = accumulated.trim();
     if (!content) {
       return {
@@ -233,11 +256,25 @@ export async function convertPdfToStatementStreaming(
     return {
       status: 502,
       error: 'BAD_GATEWAY',
-      message: 'Временная ошибка конвертации',
+      message: extractLlmErrorMessage(err),
     };
   }
 }
 
+function extractLlmErrorMessage(err: unknown): string {
+  const raw = String(
+    (err as Record<string, unknown>)?.message ??
+    (err as Record<string, Record<string, unknown>>)?.error?.message ?? '',
+  );
+  if (/context.length|n_ctx|too.many.tokens|maximum.context/i.test(raw)) {
+    return 'PDF-файл слишком большой для обработки. Попробуйте файл с меньшим количеством операций или используйте модель с большим контекстным окном.';
+  }
+  if (/timeout|timed?\s*out|ETIMEDOUT|ECONNREFUSED/i.test(raw)) {
+    return 'LLM-сервер не отвечает. Проверьте, что сервер запущен и доступен.';
+  }
+  return 'Временная ошибка конвертации';
+}
+
 function parseConversionResult(content: string): StatementFile | PdfConversionError {
   const jsonMatch = content.match(/\{[\s\S]*\}/);
   const jsonStr = jsonMatch ? jsonMatch[0] : content;

frontend/nginx.conf

@@ -15,7 +15,7 @@ server {
         proxy_connect_timeout 5s;
         proxy_read_timeout 600s;
         proxy_buffering off;
-        chunked_transfer_encoding off;
+        gzip off;
         client_max_body_size 15m;
     }
 

frontend/src/components/ImportModal.tsx

@@ -66,13 +66,11 @@ export function ImportModal({ onClose, onDone }: Props) {
         onClose();
       }
     } else {
-      if (result || importState.error) clearImport();
       onClose();
     }
   };
 
   const handleDone = () => {
-    clearImport();
     onDone();
   };
 

frontend/src/components/Layout.tsx

@@ -4,7 +4,7 @@ import { useAuth } from '../context/AuthContext';
 import { useImport } from '../context/ImportContext';
 
 function ImportProgressBar() {
-  const { importState, clearImport } = useImport();
+  const { importState, clearImport, openModal } = useImport();
   const [visible, setVisible] = useState(false);
   const hideTimerRef = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
 
@@ -31,9 +31,9 @@ function ImportProgressBar() {
 
   const handleClick = useCallback(() => {
     if (hideTimerRef.current) clearTimeout(hideTimerRef.current);
+    openModal();
     setVisible(false);
-    clearImport();
-  }, [clearImport]);
+  }, [openModal]);
 
   if (!visible) return null;
 

frontend/src/context/ImportContext.tsx

@@ -20,6 +20,9 @@ export interface ImportProgress {
 
 interface ImportContextValue {
   importState: ImportProgress;
+  showModal: boolean;
+  openModal: () => void;
+  closeModal: () => void;
   startImport: (file: File) => void;
   clearImport: () => void;
 }
@@ -35,8 +38,12 @@ const ImportContext = createContext<ImportContextValue | null>(null);
 
 export function ImportProvider({ children }: { children: ReactNode }) {
   const [importState, setImportState] = useState<ImportProgress>(INITIAL);
+  const [showModal, setShowModal] = useState(false);
   const runningRef = useRef(false);
 
+  const openModal = useCallback(() => setShowModal(true), []);
+  const closeModal = useCallback(() => setShowModal(false), []);
+
   const startImport = useCallback((file: File) => {
     if (runningRef.current) return;
     runningRef.current = true;
@@ -92,7 +99,9 @@ export function ImportProvider({ children }: { children: ReactNode }) {
   }, []);
 
   return (
-    <ImportContext.Provider value={{ importState, startImport, clearImport }}>
+    <ImportContext.Provider value={{
+      importState, showModal, openModal, closeModal, startImport, clearImport,
+    }}>
       {children}
     </ImportContext.Provider>
   );

frontend/src/pages/HistoryPage.tsx

@@ -18,6 +18,7 @@ import { TransactionTable } from '../components/TransactionTable';
 import { Pagination } from '../components/Pagination';
 import { EditTransactionModal } from '../components/EditTransactionModal';
 import { ImportModal } from '../components/ImportModal';
+import { useImport } from '../context/ImportContext';
 import { toISODate } from '../utils/format';
 
 const PARAM_KEYS = [
@@ -125,7 +126,7 @@ export function HistoryPage() {
   const [accounts, setAccounts] = useState<Account[]>([]);
   const [categories, setCategories] = useState<Category[]>([]);
   const [editingTx, setEditingTx] = useState<Transaction | null>(null);
-  const [showImport, setShowImport] = useState(false);
+  const { showModal: showImport, openModal: openImport, closeModal: closeImport, clearImport } = useImport();
 
   useEffect(() => {
     getAccounts().then(setAccounts).catch(() => {});
@@ -197,7 +198,8 @@ export function HistoryPage() {
   };
 
   const handleImportDone = () => {
-    setShowImport(false);
+    closeImport();
+    clearImport();
     fetchData();
     getAccounts().then(setAccounts).catch(() => {});
   };
@@ -208,7 +210,7 @@ export function HistoryPage() {
         <h1>История операций</h1>
         <button
           className="btn btn-primary"
-          onClick={() => setShowImport(true)}
+          onClick={openImport}
         >
           Импорт выписки
         </button>
@@ -262,7 +264,7 @@ export function HistoryPage() {
 
       {showImport && (
         <ImportModal
-          onClose={() => setShowImport(false)}
+          onClose={closeImport}
           onDone={handleImportDone}
         />
       )}