diff --git a/frontend/components/ClipboardApp/FileListDisplay.tsx b/frontend/components/ClipboardApp/FileListDisplay.tsx
index 435dc79..7d2943d 100644
--- a/frontend/components/ClipboardApp/FileListDisplay.tsx
+++ b/frontend/components/ClipboardApp/FileListDisplay.tsx
@@ -13,7 +13,7 @@ import type { Messages } from "@/types/messages";
 import { useFileTransferStore } from "@/stores/fileTransferStore";
 import { supportsAutoDownload } from "@/lib/browserUtils";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 
 function formatFolderDis(template: string, num: number, size: string) {
   return template.replace("{num}", num.toString()).replace("{size}", size);
@@ -261,7 +261,7 @@ const FileListDisplay: React.FC<FileListDisplayProps> = ({
 
           if (isAutoDownloadSupported) {
             // Browsers that support automatic downloads like Chrome: Download directly
-            if (developmentEnv === "true") {
+            if (developmentEnv === "development") {
               postLogToBackend(
                 `[Download Debug] Auto-downloading file: ${item.name}`
               );
@@ -269,7 +269,7 @@ const FileListDisplay: React.FC<FileListDisplayProps> = ({
             onDownload(item);
           } else {
             // Non-Chrome browsers: Set to save status, wait for user manual click
-            if (developmentEnv === "true") {
+            if (developmentEnv === "development") {
               postLogToBackend(
                 `[Download Debug] Setting pendingSave for non-Chrome browser: ${item.name}`
               );
@@ -280,7 +280,7 @@ const FileListDisplay: React.FC<FileListDisplayProps> = ({
             }));
           }
         } else {
-          if (developmentEnv === "true") {
+          if (developmentEnv === "development") {
             postLogToBackend(
               `Skipping download logic - isSaveToDisk: ${isSaveToDisk}, onDownload: ${!!onDownload}`
             );
diff --git a/frontend/lib/fileReceiver.ts b/frontend/lib/fileReceiver.ts
index 951a766..51992ce 100644
--- a/frontend/lib/fileReceiver.ts
+++ b/frontend/lib/fileReceiver.ts
@@ -22,7 +22,7 @@ import {
   EmbeddedChunkMeta,
 } from "@/types/webrtc";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 Strict Sequential Buffering Writer - Optimizes large file disk I/O performance
  */
@@ -40,6 +40,18 @@ class SequencedDiskWriter {
 
   /**\n   * Write a chunk, automatically managing order and buffering\n   */
   async writeChunk(chunkIndex: number, chunk: ArrayBuffer): Promise<void> {
+    // 🔍 调试writeChunk调用
+    if (
+      developmentEnv === "development" &&
+      (chunkIndex <= 5 || chunkIndex === this.nextWriteIndex)
+    ) {
+      postLogToBackend(
+        `[DEBUG-RESUME] 🎯 WriteChunk called - received:${chunkIndex}, expected:${
+          this.nextWriteIndex
+        }, match:${chunkIndex === this.nextWriteIndex}`
+      );
+    }
+
     // 1. If it is the expected next chunk, write immediately
     if (chunkIndex === this.nextWriteIndex) {
       await this.flushSequentialChunks(chunk);
@@ -50,26 +62,26 @@ class SequencedDiskWriter {
     if (chunkIndex > this.nextWriteIndex) {
       if (this.writeQueue.size < this.maxBufferSize) {
         this.writeQueue.set(chunkIndex, chunk);
-        if (developmentEnv === "true") {
-          postLogToBackend(
-            `[DEBUG] 📦 BUFFERED chunk #${chunkIndex} (waiting for #${this.nextWriteIndex}), queue: ${this.writeQueue.size}/${this.maxBufferSize}`
-          );
-        }
+        // if (developmentEnv === "development") {
+        //   postLogToBackend(
+        //     `[DEBUG] 📦 BUFFERED chunk #${chunkIndex} (waiting for #${this.nextWriteIndex}), queue: ${this.writeQueue.size}/${this.maxBufferSize}`
+        //   );
+        // }
       } else {
         // Buffer full, forcing processing of the earliest chunk to free up space
         await this.forceFlushOldest();
         this.writeQueue.set(chunkIndex, chunk);
-        if (developmentEnv === "true") {
-          postLogToBackend(
-            `[DEBUG] ⚠️ BUFFER_FULL, forced flush and buffered chunk #${chunkIndex}`
-          );
-        }
+        // if (developmentEnv === "development") {
+        //   postLogToBackend(
+        //     `[DEBUG] ⚠️ BUFFER_FULL, forced flush and buffered chunk #${chunkIndex}`
+        //   );
+        // }
       }
       return;
     }
 
     // 3. If the chunk is expired, log a warning but ignore (already written)
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] ⚠️ DUPLICATE chunk #${chunkIndex} ignored (already written #${this.nextWriteIndex})`
       );
@@ -87,7 +99,7 @@ class SequencedDiskWriter {
       await this.stream.write(firstChunk);
       this.totalWritten += firstChunk.byteLength;
 
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ✓ DISK_WRITE chunk #${this.nextWriteIndex} - ${firstChunk.byteLength} bytes, total: ${this.totalWritten}`
         );
@@ -123,7 +135,7 @@ class SequencedDiskWriter {
     }
 
     if (flushCount > 0) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] 🔥 SEQUENTIAL_FLUSH ${flushCount} chunks, now at #${this.nextWriteIndex}, queue: ${this.writeQueue.size}`
         );
@@ -131,6 +143,13 @@ class SequencedDiskWriter {
     }
   }
 
+  /**
+   * Get the next expected write index
+   */
+  get expectedIndex(): number {
+    return this.nextWriteIndex;
+  }
+
   /**
    * Force refresh the earliest chunk to release buffer space
    */
@@ -142,11 +161,11 @@ class SequencedDiskWriter {
       const chunk = this.writeQueue.get(oldestIndex)!;
 
       // Warning: Unordered write
-      if (developmentEnv === "true") {
-        postLogToBackend(
-          `[DEBUG] ⚠️ FORCE_FLUSH out-of-order chunk #${oldestIndex} (expected #${this.nextWriteIndex})`
-        );
-      }
+      // if (developmentEnv === "development") {
+      //   postLogToBackend(
+      //     `[DEBUG] ⚠️ FORCE_FLUSH out-of-order chunk #${oldestIndex} (expected #${this.nextWriteIndex})`
+      //   );
+      // }
 
       // Use seek to write at the correct position (fallback handling)
       const fileOffset = oldestIndex * 65536; // Assume each chunk is 64KB
@@ -204,7 +223,7 @@ class SequencedDiskWriter {
         const fileOffset = chunkIndex * 65536;
         await this.stream.seek(fileOffset);
         await this.stream.write(chunk);
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
             `[DEBUG] 💾 FINAL_FLUSH chunk #${chunkIndex} at cleanup`
           );
@@ -410,6 +429,38 @@ class FileReceiver {
     const receptionPromise = new Promise<void>((resolve, reject) => {
       const expectedChunksCount = Math.ceil((fileInfo.size - offset) / 65536); // Calculate expected chunk count
 
+      // 🔍 调试expectedChunksCount计算
+      if (developmentEnv === "development") {
+        const totalChunks = Math.ceil(fileInfo.size / 65536);
+        const startChunkIndex = Math.floor(offset / 65536);
+        const calculatedExpected = totalChunks - startChunkIndex;
+
+        postLogToBackend(`[DEBUG-CHUNKS] File: ${fileInfo.name}`);
+        postLogToBackend(
+          `[DEBUG-CHUNKS] File size: ${fileInfo.size}, offset: ${offset}`
+        );
+        postLogToBackend(
+          `[DEBUG-CHUNKS] Total chunks in file: ${totalChunks} (0-${
+            totalChunks - 1
+          })`
+        );
+        postLogToBackend(
+          `[DEBUG-CHUNKS] Start chunk index: ${startChunkIndex}`
+        );
+        postLogToBackend(
+          `[DEBUG-CHUNKS] Expected chunks calculation: (${fileInfo.size} - ${offset}) / 65536 = ${expectedChunksCount}`
+        );
+        postLogToBackend(
+          `[DEBUG-CHUNKS] Alternative calculation: ${totalChunks} - ${startChunkIndex} = ${calculatedExpected}`
+        );
+
+        if (expectedChunksCount !== calculatedExpected) {
+          postLogToBackend(
+            `[DEBUG-CHUNKS] ⚠️ MISMATCH: ${expectedChunksCount} vs ${calculatedExpected}`
+          );
+        }
+      }
+
       this.activeFileReception = {
         meta: fileInfo,
         chunks: new Array(expectedChunksCount).fill(null), // 🚀 Initialize as an empty array arranged by index
@@ -435,7 +486,7 @@ class FileReceiver {
       this.webrtcConnection.sendData(JSON.stringify(request), this.peerId);
       this.log("log", "Sent fileRequest", { request });
     } else {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ERROR: Cannot send fileRequest - no peerId available!`
         );
@@ -507,7 +558,7 @@ class FileReceiver {
       return true;
     });
 
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] 📁 All files in folder completed - ${folderName}, files: ${completedFileIds.length}/${folderProgress.fileIds.length}`
       );
@@ -533,7 +584,7 @@ class FileReceiver {
       try {
         const arrayBuffer = await data.arrayBuffer();
         if (data.size !== arrayBuffer.byteLength) {
-          if (developmentEnv === "true") {
+          if (developmentEnv === "development") {
             postLogToBackend(
               `[DEBUG] ⚠️ Blob size mismatch: ${data.size}→${arrayBuffer.byteLength}`
             );
@@ -541,7 +592,7 @@ class FileReceiver {
         }
         return arrayBuffer;
       } catch (error) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(`[DEBUG] ❌ Blob conversion failed: ${error}`);
         }
         return null;
@@ -556,13 +607,13 @@ class FileReceiver {
         new Uint8Array(newArrayBuffer).set(uint8Array);
         return newArrayBuffer;
       } catch (error) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(`[DEBUG] ❌ TypedArray conversion failed: ${error}`);
         }
         return null;
       }
     } else {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ❌ Unknown data type: ${Object.prototype.toString.call(
             data
@@ -584,7 +635,7 @@ class FileReceiver {
     try {
       // 1. Check minimum packet length
       if (arrayBuffer.byteLength < 4) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
             `[DEBUG] ❌ Invalid embedded packet - too small: ${arrayBuffer.byteLength}`
           );
@@ -599,7 +650,7 @@ class FileReceiver {
       // 3. Verify packet integrity
       const expectedTotalLength = 4 + metaLength;
       if (arrayBuffer.byteLength < expectedTotalLength) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
             `[DEBUG] ❌ Incomplete embedded packet - expected: ${expectedTotalLength}, got: ${arrayBuffer.byteLength}`
           );
@@ -618,7 +669,7 @@ class FileReceiver {
 
       // 6. Verify chunk data size
       if (chunkData.byteLength !== chunkMeta.chunkSize) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
             `[DEBUG] ⚠️ Chunk size mismatch - meta: ${chunkMeta.chunkSize}, actual: ${chunkData.byteLength}`
           );
@@ -627,7 +678,7 @@ class FileReceiver {
 
       return { chunkMeta, chunkData };
     } catch (error) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ❌ Failed to parse embedded packet: ${error}`
         );
@@ -664,7 +715,7 @@ class FileReceiver {
 
       if (arrayBuffer) {
         if (!this.activeFileReception) {
-          if (developmentEnv === "true") {
+          if (developmentEnv === "development") {
             postLogToBackend(
               `[DEBUG] ERROR: Received file chunk but no active file reception!`
             );
@@ -679,7 +730,7 @@ class FileReceiver {
         // 🚀 Unified processing: All data is processed as embedded packets
         await this.handleEmbeddedChunkPacket(arrayBuffer);
       } else {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
             `[DEBUG] ERROR: Failed to convert binary data to ArrayBuffer`
           );
@@ -773,7 +824,7 @@ class FileReceiver {
 
     // Verify fileId match
     if (chunkMeta.fileId !== reception.meta.fileId) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ⚠️ FileId mismatch - expected: ${reception.meta.fileId}, got: ${chunkMeta.fileId}`
         );
@@ -781,44 +832,74 @@ class FileReceiver {
       return;
     }
 
-    // Update expected chunks count (may differ from initial estimate)
+    // 🔧 修复：续传时不要调整expectedChunksCount
+    // chunkMeta.totalChunks是文件总chunk数，但续传时我们只接收部分chunks
     if (chunkMeta.totalChunks !== reception.expectedChunksCount) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
+        const startChunkIndex = Math.floor(reception.initialOffset / 65536);
+        const calculatedExpected = chunkMeta.totalChunks - startChunkIndex;
         postLogToBackend(
-          `[DEBUG] ⚠️ Chunk count adjustment - expected: ${reception.expectedChunksCount}, actual: ${chunkMeta.totalChunks}`
+          `[DEBUG-CHUNKS] Chunk count info - fileTotal: ${chunkMeta.totalChunks}, currentExpected: ${reception.expectedChunksCount}, calculatedExpected: ${calculatedExpected}, startChunk: ${startChunkIndex}`
         );
-      }
-      reception.expectedChunksCount = chunkMeta.totalChunks;
-      // Adjust chunks array size
-      if (reception.chunks.length < chunkMeta.totalChunks) {
-        const newChunks = new Array(chunkMeta.totalChunks).fill(null);
-        reception.chunks.forEach((chunk, index) => {
-          if (index < newChunks.length) newChunks[index] = chunk;
-        });
-        reception.chunks = newChunks;
+
+        // 🚫 不再调整expectedChunksCount，保持续传时的正确数量
+        // reception.expectedChunksCount = chunkMeta.totalChunks; // 这行导致了问题！
+
+        if (reception.expectedChunksCount !== calculatedExpected) {
+          postLogToBackend(
+            `[DEBUG-CHUNKS] ⚠️ Expected chunks mismatch, should be ${calculatedExpected}`
+          );
+        }
       }
     }
 
-    // Store chunk by index
-    const chunkIndex = chunkMeta.chunkIndex;
-    if (chunkIndex >= 0 && chunkIndex < reception.chunks.length) {
-      reception.chunks[chunkIndex] = chunkData;
-      reception.chunkSequenceMap.set(chunkIndex, true);
+    // Store chunk by index - 🔧 修复：将绝对索引映射到相对索引
+    const absoluteChunkIndex = chunkMeta.chunkIndex; // 发送端的绝对索引（如967-3650）
+    const startChunkIndex = Math.floor(reception.initialOffset / 65536); // 续传起始索引（如967）
+    const relativeChunkIndex = absoluteChunkIndex - startChunkIndex; // 在chunks数组中的相对索引（如0-2683）
+
+    if (developmentEnv === "development" && absoluteChunkIndex <= 970) {
+      postLogToBackend(
+        `[DEBUG-CHUNKS] Index mapping - absolute:${absoluteChunkIndex}, start:${startChunkIndex}, relative:${relativeChunkIndex}, arraySize:${reception.chunks.length}`
+      );
+    }
+
+    if (
+      relativeChunkIndex >= 0 &&
+      relativeChunkIndex < reception.chunks.length
+    ) {
+      reception.chunks[relativeChunkIndex] = chunkData;
+      reception.chunkSequenceMap.set(absoluteChunkIndex, true); // 序列映射仍使用绝对索引
       reception.receivedChunksCount++;
 
       // Update progress
       this.updateProgress(chunkData.byteLength);
 
       if (reception.sequencedWriter) {
-        // 🚀 Use strict sequential write management
-        await reception.sequencedWriter.writeChunk(chunkIndex, chunkData);
+        // 🔍 调试chunk接收匹配 (前5个和后5个chunks)
+        const lastFewChunks =
+          relativeChunkIndex >= reception.expectedChunksCount - 5;
+        if (
+          developmentEnv === "development" &&
+          (absoluteChunkIndex <= 970 || lastFewChunks)
+        ) {
+          postLogToBackend(
+            `[DEBUG-CHUNKS] 📦 Chunk #${absoluteChunkIndex} received - relative:${relativeChunkIndex}, size:${chunkData.byteLength}, writerExpects:${reception.sequencedWriter.expectedIndex}, isLastFew:${lastFewChunks}`
+          );
+        }
+
+        // 🚀 Use strict sequential write management - 使用绝对索引
+        await reception.sequencedWriter.writeChunk(
+          absoluteChunkIndex,
+          chunkData
+        );
       }
     } else {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
-          `[DEBUG] ❌ Invalid chunk index - ${chunkIndex}, expected 0-${
-            reception.chunks.length - 1
-          }`
+          `[DEBUG-CHUNKS] ❌ Invalid relative chunk index - absolute:${absoluteChunkIndex}, relative:${relativeChunkIndex}, arraySize:${
+            reception.chunks.length
+          }, expected:0-${reception.chunks.length - 1}`
         );
       }
     }
@@ -840,7 +921,8 @@ class FileReceiver {
     const currentTotalSize = reception.chunks.reduce((sum, chunk) => {
       return sum + (chunk instanceof ArrayBuffer ? chunk.byteLength : 0);
     }, 0);
-    const expectedSize = reception.meta.size;
+    // 🔧 修复：续传时应该比较的是剩余文件大小，不是整个文件大小
+    const expectedSize = reception.meta.size - reception.initialOffset;
 
     // 🚀 Unified integrity check: sequential reception mode
     let sequencedCount = 0;
@@ -850,10 +932,55 @@ class FileReceiver {
       }
     }
     const isSequencedComplete = sequencedCount === expectedChunks;
-
     const sizeComplete = currentTotalSize >= expectedSize;
     const isDataComplete = isSequencedComplete && sizeComplete;
 
+    // 🔍 详细调试完成检查 (减少频率，只在关键时刻输出)
+    if (
+      developmentEnv === "development" &&
+      (isDataComplete ||
+        sequencedCount % 500 === 0 ||
+        sequencedCount > expectedChunks - 10)
+    ) {
+      // 检查最后几个chunks的状态 (显示相对索引)
+      const lastChunkIndex = expectedChunks - 1;
+      const lastFewChunks = [];
+      const startChunkIndex = Math.floor(reception.initialOffset / 65536);
+
+      for (let i = Math.max(0, lastChunkIndex - 3); i <= lastChunkIndex; i++) {
+        const chunk = reception.chunks[i];
+        const exists = chunk instanceof ArrayBuffer;
+        const size = exists ? (chunk as ArrayBuffer).byteLength : 0;
+        const absoluteIndex = startChunkIndex + i; // 对应的绝对索引
+        lastFewChunks.push(`rel#${i}(abs#${absoluteIndex}):${exists}(${size})`);
+      }
+
+      postLogToBackend(
+        `[DEBUG-COMPLETE] Check completion - file:${reception.meta.name}`
+      );
+      postLogToBackend(
+        `[DEBUG-COMPLETE] Chunks: received:${sequencedCount}/${expectedChunks}, isSequenceComplete:${isSequencedComplete}`
+      );
+      postLogToBackend(
+        `[DEBUG-COMPLETE] Size: current:${currentTotalSize}, expected:${expectedSize}, sizeComplete:${sizeComplete}, diff:${
+          expectedSize - currentTotalSize
+        }`
+      );
+      postLogToBackend(
+        `[DEBUG-COMPLETE] LastChunks: ${lastFewChunks.join(", ")}`
+      );
+      postLogToBackend(
+        `[DEBUG-COMPLETE] IsDataComplete: ${isDataComplete}, isFinalized: ${reception.isFinalized}`
+      );
+
+      if (reception.sequencedWriter) {
+        const writerStatus = reception.sequencedWriter.getBufferStatus();
+        postLogToBackend(
+          `[DEBUG-COMPLETE] SequencedWriter: nextIndex:${writerStatus.nextIndex}, totalWritten:${writerStatus.totalWritten}, queueSize:${writerStatus.queueSize}`
+        );
+      }
+    }
+
     // Prevent duplicate finalize
     if (reception.isFinalized) {
       return;
@@ -862,6 +989,12 @@ class FileReceiver {
     if (isDataComplete) {
       reception.isFinalized = true;
 
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-COMPLETE] ✅ Starting finalization - isDataComplete:${isDataComplete}`
+        );
+      }
+
       try {
         await this.finalizeFileReceive();
 
@@ -870,7 +1003,7 @@ class FileReceiver {
         }
         this.activeFileReception = null;
       } catch (error) {
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(`[DEBUG] ❌ Auto-finalize ERROR: ${error}`);
         }
         if (reception.completionNotifier) {
@@ -958,10 +1091,14 @@ class FileReceiver {
         startChunkIndex
       );
 
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] 📢 SEQUENCED_WRITER created - startIndex: ${startChunkIndex}, offset: ${offset}`
         );
+        // 🔍 调试续传接收期望
+        postLogToBackend(
+          `[DEBUG-RESUME] 🎯 SequencedWriter expects - startIndex:${startChunkIndex}, offset:${offset}, calculatedFrom:${offset}/65536`
+        );
       }
     } catch (err) {
       this.fireError("Failed to create file on disk", {
@@ -994,28 +1131,59 @@ class FileReceiver {
 
   private async finalizeLargeFileReceive(): Promise<void> {
     const reception = this.activeFileReception;
-    if (!reception?.writeStream || !reception.fileHandle) return;
+    if (!reception?.writeStream || !reception.fileHandle) {
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-FINALIZE] ❌ Cannot finalize - missing writeStream:${!!reception?.writeStream} or fileHandle:${!!reception?.fileHandle}`
+        );
+      }
+      return;
+    }
 
     try {
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-FINALIZE] 🚀 Starting finalization for ${reception.meta.name}`
+        );
+      }
+
       // 🚀 First close the strict sequential writing manager (flush all buffers)
       if (reception.sequencedWriter) {
+        if (developmentEnv === "development") {
+          postLogToBackend(`[DEBUG-FINALIZE] Closing SequencedWriter...`);
+        }
         await reception.sequencedWriter.close();
         const status = reception.sequencedWriter.getBufferStatus();
-        if (developmentEnv === "true") {
+        if (developmentEnv === "development") {
           postLogToBackend(
-            `[DEBUG] 💾 SEQUENCED_WRITER closed - totalWritten: ${status.totalWritten}, finalQueue: ${status.queueSize}`
+            `[DEBUG-FINALIZE] 💾 SEQUENCED_WRITER closed - totalWritten: ${status.totalWritten}, finalQueue: ${status.queueSize}`
           );
         }
         reception.sequencedWriter = null;
       }
 
       // Then close the file stream
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-FINALIZE] About to close writeStream for ${reception.meta.name}`
+        );
+      }
       await reception.writeStream.close();
+      if (developmentEnv === "development") {
+        postLogToBackend(`[DEBUG-FINALIZE] ✅ WriteStream closed successfully`);
+      }
 
-      if (developmentEnv === "true") {
-        postLogToBackend(`[DEBUG] ✅ LARGE_FILE finalized successfully`);
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-FINALIZE] ✅ LARGE_FILE finalized successfully - ${reception.meta.name}`
+        );
       }
     } catch (error) {
+      if (developmentEnv === "development") {
+        postLogToBackend(
+          `[DEBUG-FINALIZE] ❌ Error during finalization: ${error}`
+        );
+      }
       this.fireError("Error finalizing large file", { error });
     }
   }
@@ -1040,7 +1208,7 @@ class FileReceiver {
     // Final verification
     const sizeDifference = reception.meta.size - totalChunkSize;
     if (sizeDifference !== 0) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ❌ SIZE_MISMATCH - missing: ${sizeDifference} bytes`
         );
@@ -1131,7 +1299,7 @@ class FileReceiver {
       this.peerId
     );
 
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] 📤 Sent folderReceiveComplete - folderName: ${folderName}, completedFiles: ${completedFileIds.length}, allStoreUpdated: ${allStoreUpdated}, success: ${success}`
       );
diff --git a/frontend/lib/tracking.ts b/frontend/lib/tracking.ts
index 4cc95b8..b87d5a8 100644
--- a/frontend/lib/tracking.ts
+++ b/frontend/lib/tracking.ts
@@ -4,7 +4,7 @@ export const trackReferrer = async () => {
   // Get URL parameters
   const urlParams = new URLSearchParams(window.location.search);
   let ref = urlParams.get("ref");
-  if (process.env.NEXT_PUBLIC_development === "false") {
+  if (process.env.NODE_ENV === "production") {
     ref = urlParams.get("ref") || "noRef"; // Production environment, count daily active users, record as noRef if there is no ref
   }
 
diff --git a/frontend/lib/transfer/FileTransferOrchestrator.ts b/frontend/lib/transfer/FileTransferOrchestrator.ts
index 5d58dc2..842e4e5 100644
--- a/frontend/lib/transfer/FileTransferOrchestrator.ts
+++ b/frontend/lib/transfer/FileTransferOrchestrator.ts
@@ -14,7 +14,7 @@ import { StreamingFileReader } from "./StreamingFileReader";
 import { TransferConfig } from "./TransferConfig";
 import WebRTC_Initiator from "../webrtc_Initiator";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 File transfer orchestrator
  * Integrates all components to provide unified file transfer services
@@ -211,7 +211,7 @@ export class FileTransferOrchestrator implements MessageHandlerDelegate {
       peerState.readOffset || 0
     );
 
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] 🚀 Starting transfer - file: ${file.name}, size: ${(
           file.size /
@@ -301,20 +301,32 @@ export class FileTransferOrchestrator implements MessageHandlerDelegate {
         }
       }
 
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         const totalTime = performance.now() - transferStartTime;
         const avgSpeedMBps = totalBytesSent / 1024 / 1024 / (totalTime / 1000);
+        const expectedTotalChunks = Math.ceil(file.size / 65536);
+        const startOffset = peerState.readOffset || 0;
+        const startChunkIndex = Math.floor(startOffset / 65536);
+        const expectedChunksSent = expectedTotalChunks - startChunkIndex;
+
         postLogToBackend(
-          `[DEBUG] ✅ Transfer complete - file: ${file.name}, time: ${(
+          `[DEBUG-CHUNKS] ✅ Transfer complete - file: ${file.name}, time: ${(
             totalTime / 1000
-          ).toFixed(1)}s, speed: ${avgSpeedMBps.toFixed(
-            1
-          )}MB/s, chunks: ${networkChunkIndex}`
+          ).toFixed(1)}s, speed: ${avgSpeedMBps.toFixed(1)}MB/s`
         );
+        postLogToBackend(
+          `[DEBUG-CHUNKS] Chunks sent: ${networkChunkIndex}, expected: ${expectedChunksSent}, startChunk: ${startChunkIndex}, totalFileChunks: ${expectedTotalChunks}`
+        );
+
+        if (networkChunkIndex !== expectedChunksSent) {
+          postLogToBackend(
+            `[DEBUG-CHUNKS] ⚠️ CHUNK MISMATCH: sent ${networkChunkIndex} but expected ${expectedChunksSent}`
+          );
+        }
       }
     } catch (error: any) {
       const errorMessage = `Streaming send error: ${error.message}`;
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(`[DEBUG] ❌ Transfer error: ${errorMessage}`);
       }
       this.fireError(errorMessage, {
@@ -428,7 +440,7 @@ export class FileTransferOrchestrator implements MessageHandlerDelegate {
   public handlePeerReconnection(peerId: string): void {
     // Clear all transfer states for this peer
     this.stateManager.clearPeerState(peerId);
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       this.log(
         "log",
         `Successfully reset transfer state for reconnected peer ${peerId}`
@@ -443,7 +455,7 @@ export class FileTransferOrchestrator implements MessageHandlerDelegate {
     this.networkTransmitter.cleanup();
     this.progressTracker.cleanup();
     this.messageHandler.cleanup();
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       this.log("log", "FileTransferOrchestrator cleaned up");
   }
 }
diff --git a/frontend/lib/transfer/MessageHandler.ts b/frontend/lib/transfer/MessageHandler.ts
index 61e8d57..4481c7a 100644
--- a/frontend/lib/transfer/MessageHandler.ts
+++ b/frontend/lib/transfer/MessageHandler.ts
@@ -6,7 +6,7 @@ import {
 } from "@/types/webrtc";
 import { StateManager } from "./StateManager";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 Message handling interface - Communicate with main orchestrator
  */
@@ -120,7 +120,7 @@ export class MessageHandler {
     message: FolderReceiveComplete,
     peerId: string
   ): void {
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] 📥 Folder complete - folderName: ${message.folderName}, files: ${message.completedFileIds.length}`
       );
@@ -172,7 +172,7 @@ export class MessageHandler {
    * 🧹 Clean up resources
    */
   public cleanup(): void {
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       postLogToBackend("[DEBUG] 🧹 MessageHandler cleaned up");
   }
 }
diff --git a/frontend/lib/transfer/NetworkTransmitter.ts b/frontend/lib/transfer/NetworkTransmitter.ts
index 7b0da2c..fa897f2 100644
--- a/frontend/lib/transfer/NetworkTransmitter.ts
+++ b/frontend/lib/transfer/NetworkTransmitter.ts
@@ -2,7 +2,7 @@ import { EmbeddedChunkMeta } from "@/types/webrtc";
 import { StateManager } from "./StateManager";
 import WebRTC_Initiator from "../webrtc_Initiator";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 Network transmitter - Simplified version
  * Uses WebRTC native bufferedAmountLowThreshold for backpressure control
@@ -34,7 +34,7 @@ export class NetworkTransmitter {
       // Key node logs (development environment only)
 
       if (
-        developmentEnv === "true" &&
+        developmentEnv === "development" &&
         (metadata.chunkIndex % 100 === 0 || metadata.isLastChunk)
       ) {
         postLogToBackend(
@@ -48,7 +48,7 @@ export class NetworkTransmitter {
 
       return true;
     } catch (error) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `[DEBUG] ❌ CHUNK #${metadata.chunkIndex} send failed: ${error}`
         );
@@ -106,7 +106,7 @@ export class NetworkTransmitter {
     if (!sendResult) {
       const errorMessage = `sendData failed`;
 
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(`[DEBUG] ❌ ${errorMessage}`);
       }
       throw new Error(errorMessage);
@@ -148,7 +148,7 @@ export class NetworkTransmitter {
       });
 
       // Only output backpressure logs in development environment
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         const waitTime = performance.now() - startTime;
         postLogToBackend(
           `[DEBUG] 🚀 BACKPRESSURE - wait: ${waitTime.toFixed(
@@ -182,7 +182,7 @@ export class NetworkTransmitter {
       }
     } catch (error) {
       const errorMessage = `sendWithBackpressure failed: ${error}`;
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(`[DEBUG] ❌ ${errorMessage}`);
       }
       throw new Error(errorMessage);
@@ -239,7 +239,7 @@ export class NetworkTransmitter {
    * 🧹 Clean up resources
    */
   public cleanup(): void {
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend("[DEBUG] 🧹 NetworkTransmitter cleaned up");
     }
   }
diff --git a/frontend/lib/transfer/ProgressTracker.ts b/frontend/lib/transfer/ProgressTracker.ts
index 18d0d06..f28b6c2 100644
--- a/frontend/lib/transfer/ProgressTracker.ts
+++ b/frontend/lib/transfer/ProgressTracker.ts
@@ -1,7 +1,7 @@
 import { SpeedCalculator } from "@/lib/speedCalculator";
 import { StateManager } from "./StateManager";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 Progress callback type definition
  */
@@ -225,7 +225,7 @@ export class ProgressTracker {
    */
   cleanup(): void {
     // SpeedCalculator internally automatically cleans up expired data
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       postLogToBackend("[DEBUG] 🧹 ProgressTracker cleaned up");
   }
 }
diff --git a/frontend/lib/transfer/StreamingFileReader.ts b/frontend/lib/transfer/StreamingFileReader.ts
index 087c536..3a22e71 100644
--- a/frontend/lib/transfer/StreamingFileReader.ts
+++ b/frontend/lib/transfer/StreamingFileReader.ts
@@ -1,7 +1,7 @@
 import { CustomFile } from "@/types/webrtc";
 import { TransferConfig } from "./TransferConfig";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!;
+const developmentEnv = process.env.NODE_ENV;
 /**
  * 🚀 Network chunk interface
  */
@@ -46,9 +46,11 @@ export class StreamingFileReader {
     this.file = file;
     this.totalFileSize = file.size;
     this.totalFileOffset = startOffset;
+    // 🔧 修复：续传时currentBatchStartOffset应该从startOffset开始
+    this.currentBatchStartOffset = startOffset;
     this.fileReader = new FileReader();
 
-    if (developmentEnv === "true") {
+    if (developmentEnv === "development") {
       postLogToBackend(
         `[DEBUG] 📖 StreamingFileReader created - file: ${file.name}, size: ${(
           this.totalFileSize /
@@ -56,6 +58,13 @@ export class StreamingFileReader {
           1024
         ).toFixed(1)}MB`
       );
+      // 🔍 调试续传初始化
+      const expectedGlobalChunk = Math.floor(
+        startOffset / this.NETWORK_CHUNK_SIZE
+      );
+      postLogToBackend(
+        `[DEBUG-RESUME] 🏗️ StreamingFileReader created - totalFileOffset:${this.totalFileOffset}, currentBatchStartOffset:${this.currentBatchStartOffset}, expectedGlobalChunk:${expectedGlobalChunk}`
+      );
     }
   }
 
@@ -89,6 +98,15 @@ export class StreamingFileReader {
 
     // Delete frequent chunk progress logs
 
+    // 🔍 调试chunk发送 (前5个和最后5个chunks)
+    const totalChunks = this.calculateTotalNetworkChunks();
+    const isLastFew = globalChunkIndex >= (totalChunks - 5);
+    if (developmentEnv === "development" && (globalChunkIndex <= 5 || isLastFew || isLast)) {
+      postLogToBackend(
+        `[DEBUG-CHUNKS] 📤 Send chunk #${globalChunkIndex}/${totalChunks} - size:${networkChunk.byteLength}, isLast:${isLast}, fileOffset:${this.totalFileOffset - networkChunk.byteLength}`
+      );
+    }
+
     return {
       chunk: networkChunk,
       chunkIndex: globalChunkIndex,
@@ -160,11 +178,24 @@ export class StreamingFileReader {
       this.currentBatch = await this.readFileSlice(fileSlice);
       const readTime = performance.now() - readStartTime;
 
-      this.currentBatchStartOffset = this.totalFileOffset;
-      this.currentChunkIndexInBatch = 0;
+      const batchStartOffset = this.totalFileOffset;
+      this.currentBatchStartOffset = batchStartOffset;
+
+      // 🔧 修复：如果不是从batch边界开始，说明是续传情况，需要计算正确的batch内索引
+      if (batchStartOffset % this.BATCH_SIZE !== 0) {
+        // 续传情况：不是从batch边界开始
+        const globalChunkIndex = Math.floor(
+          batchStartOffset / this.NETWORK_CHUNK_SIZE
+        );
+        this.currentChunkIndexInBatch =
+          globalChunkIndex % this.CHUNKS_PER_BATCH;
+      } else {
+        // 正常情况：从batch边界开始
+        this.currentChunkIndexInBatch = 0;
+      }
 
       // Only output batch reading logs in development environment
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         const totalTime = performance.now() - startTime;
         const speedMBps = batchSize / 1024 / 1024 / (totalTime / 1000);
         postLogToBackend(
@@ -174,9 +205,15 @@ export class StreamingFileReader {
             1
           )}MB/s`
         );
+        // 🔍 调试batch内索引设置
+        postLogToBackend(
+          `[DEBUG-RESUME] 📖 BATCH loaded - batchStartOffset:${batchStartOffset}, currentChunkIndexInBatch:${
+            this.currentChunkIndexInBatch
+          }, isResume:${batchStartOffset % this.BATCH_SIZE !== 0}`
+        );
       }
     } catch (error) {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(`[DEBUG] ❌ BATCH_READ failed: ${error}`);
       }
       throw new Error(`Failed to load file batch: ${error}`);
@@ -247,7 +284,19 @@ export class StreamingFileReader {
       this.currentBatchStartOffset / this.BATCH_SIZE
     );
     const chunksInPreviousBatches = batchesBefore * this.CHUNKS_PER_BATCH;
-    return chunksInPreviousBatches + this.currentChunkIndexInBatch;
+    const result = chunksInPreviousBatches + this.currentChunkIndexInBatch;
+
+    // 🔍 调试chunk索引计算
+    if (
+      developmentEnv === "development" &&
+      this.currentChunkIndexInBatch <= 5
+    ) {
+      postLogToBackend(
+        `[DEBUG-RESUME] 🧮 calculateGlobalChunkIndex - batchStartOffset:${this.currentBatchStartOffset}, batchesBefore:${batchesBefore}, chunksInPrev:${chunksInPreviousBatches}, chunkInBatch:${this.currentChunkIndexInBatch}, result:${result}`
+      );
+    }
+
+    return result;
   }
 
   /**
@@ -324,10 +373,14 @@ export class StreamingFileReader {
     this.isFinished = false;
     this.isReading = false;
     this.currentBatch = null;
-    this.currentBatchStartOffset = 0;
-    this.currentChunkIndexInBatch = 0;
-    if (developmentEnv === "true") {
-      postLogToBackend(`[DEBUG] 🔄 StreamingFileReader reset`);
+    // 🔧 修复：reset时也要正确设置currentBatchStartOffset
+    this.currentBatchStartOffset = startOffset;
+    this.currentChunkIndexInBatch = 0; // 重置为0，loadNextBatch会重新计算
+
+    if (developmentEnv === "development") {
+      postLogToBackend(
+        `[DEBUG] 🔄 StreamingFileReader reset - startOffset:${startOffset}`
+      );
     }
   }
 
diff --git a/frontend/lib/webrtc_Initiator.ts b/frontend/lib/webrtc_Initiator.ts
index 05ab205..9cdd619 100644
--- a/frontend/lib/webrtc_Initiator.ts
+++ b/frontend/lib/webrtc_Initiator.ts
@@ -1,7 +1,7 @@
 // Initiator flow: Join room; receive 'ready' event (this event is triggered by the socket server after a new recipient enters) -> createPeerConnection + createDataChannel -> createAndSendOffer
 import BaseWebRTC, { WebRTCConfig } from "./webrtc_base";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!; // Development environment
+const developmentEnv = process.env.NODE_ENV; // Development environment
 
 export default class WebRTC_Initiator extends BaseWebRTC {
   constructor(config: WebRTCConfig) {
@@ -16,7 +16,7 @@ export default class WebRTC_Initiator extends BaseWebRTC {
     });
     // Add listener for recipient's response
     this.socket.on("recipient-ready", ({ peerId }) => {
-      if (developmentEnv === "true")
+      if (developmentEnv === "development")
         postLogToBackend(
           `[Initiator] Received recipient-ready from: ${peerId}`
         );
@@ -32,7 +32,7 @@ export default class WebRTC_Initiator extends BaseWebRTC {
   private async handleReady({ peerId }: { peerId: string }): Promise<void> {
     // Recipient peerId
     // this.log('log',`Received ready signal from peer ${peerId}`);
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       postLogToBackend(`Received ready signal from peer ${peerId}`);
     await this.createPeerConnection(peerId);
     await this.createDataChannel(peerId);
@@ -48,7 +48,7 @@ export default class WebRTC_Initiator extends BaseWebRTC {
     from: string;
   }): Promise<void> {
     // this.log('log',`Handling answer from peer ${from}`);
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       postLogToBackend(`Handling answer from peer ${from}`);
     const peerConnection = this.peerConnections.get(from);
     if (!peerConnection) {
@@ -96,7 +96,7 @@ export default class WebRTC_Initiator extends BaseWebRTC {
   // If it is the initiator, create and send an offer to the signaling server to negotiate a connection with the recipient.
   private async createAndSendOffer(peerId: string): Promise<void> {
     // this.log('log', `Creating and sending offer to ${peerId}`);
-    if (developmentEnv === "true")
+    if (developmentEnv === "development")
       postLogToBackend(`createAndSendOffer for peerId: ${peerId}`);
     const peerConnection = this.peerConnections.get(peerId);
     if (!peerConnection) {
diff --git a/frontend/lib/webrtc_base.ts b/frontend/lib/webrtc_base.ts
index 967b218..64be02e 100644
--- a/frontend/lib/webrtc_base.ts
+++ b/frontend/lib/webrtc_base.ts
@@ -2,7 +2,7 @@
 import io, { Socket, ManagerOptions, SocketOptions } from "socket.io-client";
 import { WakeLockManager } from "./wakeLockManager";
 import { postLogToBackend } from "@/app/config/api";
-const developmentEnv = process.env.NEXT_PUBLIC_development!; // Development environment
+const developmentEnv = process.env.NODE_ENV; // Development environment
 
 export class WebRTCError extends Error {
   constructor(message: string, public context?: Record<string, any>) {
@@ -131,7 +131,7 @@ export default class BaseWebRTC {
     this.socket.on("disconnect", () => {
       this.isInRoom = false;
       this.isSocketDisconnected = true;
-      if (developmentEnv === "true")
+      if (developmentEnv === "development")
         postLogToBackend(
           `${this.peerId} disconnect on socket,isInitiator:${this.isInitiator},isInRoom:${this.isInRoom}`
         );
@@ -153,7 +153,7 @@ export default class BaseWebRTC {
     if (this.isSocketDisconnected && this.isPeerDisconnected && this.roomId) {
       // Start reconnection only after both socket and P2P connections are disconnected
       this.reconnectionInProgress = true;
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(
           `Starting reconnection, socket and peer both disconnected. isInitiator:${this.isInitiator}`
         );
@@ -314,7 +314,7 @@ export default class BaseWebRTC {
       disconnected: async () => {
         await this.cleanupExistingConnection(peerId);
         this.isPeerDisconnected = true;
-        if (developmentEnv === "true")
+        if (developmentEnv === "development")
           postLogToBackend(`p2p disconnected, isInitiator:${this.isInitiator}`);
         // Attempt to reconnect
         this.attemptReconnection();
@@ -402,7 +402,7 @@ export default class BaseWebRTC {
     };
 
     dataChannel.onclose = () => {
-      if (developmentEnv === "true") {
+      if (developmentEnv === "development") {
         postLogToBackend(`DataChannel closed for peer: ${peerId}`);
       }
       this.log("log", `Data channel with ${peerId} closed.`);
@@ -440,7 +440,7 @@ export default class BaseWebRTC {
               roomId: this.roomId,
             });
           }
-          if (developmentEnv === "true")
+          if (developmentEnv === "development")
             postLogToBackend(
               `peerId:${this.socket.id} Successfully joined room: ${response.roomId},isInitiator:${this.isInitiator},isInRoom:${this.isInRoom}`
             );
@@ -448,7 +448,7 @@ export default class BaseWebRTC {
         } else {
           this.isInRoom = false;
           this.roomId = null;
-          if (developmentEnv === "true")
+          if (developmentEnv === "development")
             postLogToBackend(`Failed to join room,message:${response.message}`);
           this.fireError("Failed to join room", { message: response.message });
           reject(new Error(response.message));
@@ -499,10 +499,10 @@ export default class BaseWebRTC {
             ? data.byteLength
             : 0;
 
-        if (developmentEnv === "true")
-          postLogToBackend(
-            `sendToPeer - type: ${dataType}, size: ${dataSize}, bufferedAmount: ${dataChannel.bufferedAmount}`
-          );
+        // if (developmentEnv === "development")
+        //   postLogToBackend(
+        //     `sendToPeer - type: ${dataType}, size: ${dataSize}, bufferedAmount: ${dataChannel.bufferedAmount}`
+        //   );
 
         dataChannel.send(data);
         return true;