diff --git a/src/main/ipc.ts b/src/main/ipc.ts
index a42c95c..da5e1cf 100644
--- a/src/main/ipc.ts
+++ b/src/main/ipc.ts
@@ -53,6 +53,15 @@ export function setupIPC(): void {
     }
   });
 
+  ipcMain.handle('fs:readFileBase64', async (_, filePath: string) => {
+    try {
+      const buf = await fs.promises.readFile(filePath);
+      return { success: true, content: buf.toString('base64'), size: buf.length, name: path.basename(filePath) };
+    } catch (err) {
+      return { success: false, error: (err as Error).message };
+    }
+  });
+
   ipcMain.handle('fs:writeFile', async (_, filePath: string, content: string, encoding?: string) => {
     try {
       await fs.promises.writeFile(filePath, content, (encoding as BufferEncoding) || 'utf-8');
diff --git a/src/main/preload.ts b/src/main/preload.ts
index 0ba6b14..62e77b5 100644
--- a/src/main/preload.ts
+++ b/src/main/preload.ts
@@ -13,6 +13,7 @@ contextBridge.exposeInMainWorld('metonaDesktop', {
   },
   fs: {
     readFile: (filePath: string) => ipcRenderer.invoke('fs:readFile', filePath),
+    readFileBase64: (filePath: string) => ipcRenderer.invoke('fs:readFileBase64', filePath),
     writeFile: (filePath: string, content: string, encoding?: string) => ipcRenderer.invoke('fs:writeFile', filePath, content, encoding)
   },
   tool: {
diff --git a/src/renderer/components/input-area.ts b/src/renderer/components/input-area.ts
index 7dc7662..3c696eb 100644
--- a/src/renderer/components/input-area.ts
+++ b/src/renderer/components/input-area.ts
@@ -136,20 +136,19 @@ async function handleImagePaths(paths: string[]): Promise<void> {
   for (const filePath of paths) {
     const name = filePath.split(/[/\\]/).pop() || filePath;
     try {
-      const result = await bridge.fs.readFile(filePath);
+      const result = await bridge.fs.readFileBase64(filePath);
       if (!result.success) {
         appendSystemMessage(`❌ 读取 ${name} 失败: ${result.error}`);
         continue;
       }
-      // IPC 返回的 content 是 UTF-8 字符串，转为 base64
-      const binary = Uint8Array.from(atob(result.content as string), c => c.charCodeAt(0));
-      const base64 = btoa(String.fromCharCode(...binary));
-      if (binary.length > maxSize) {
+      const size = result.size ?? 0;
+      if (size > maxSize) {
         appendSystemMessage(`⚠️ 图片 ${name} 超过 20MB 限制`);
         continue;
       }
+      const base64 = result.content!;
       pendingImages.push({ name, base64 });
-      logInfo(`图片已添加: ${name}`, formatSize(binary.length));
+      logInfo(`图片已添加: ${name}`, formatSize(size));
     } catch (err) {
       logError('图片读取失败', (err as Error).message);
       appendSystemMessage(`❌ 读取 ${name} 失败`);
diff --git a/src/renderer/components/settings-modal.ts b/src/renderer/components/settings-modal.ts
index f2c2a22..d3a03cd 100644
--- a/src/renderer/components/settings-modal.ts
+++ b/src/renderer/components/settings-modal.ts
@@ -298,12 +298,12 @@ async function importSessions(filePath: string): Promise<void> {
 
   try {
     const bridge = (window as any).metonaDesktop;
-    const result = await bridge.fs.readFile(filePath);
+    const result = await bridge.fs.readFileBase64(filePath);
     if (!result.success) {
       showToast(`读取文件失败: ${result.error}`, 'error');
       return;
     }
-    // IPC 返回 base64 编码的二进制，转 ArrayBuffer
+    // 主进程返回 base64，直接解码为二进制
     const binary = atob(result.content as string);
     const bytes = new Uint8Array(binary.length);
     for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i);
diff --git a/src/renderer/types.d.ts b/src/renderer/types.d.ts
index ce063b8..dc2aab8 100644
--- a/src/renderer/types.d.ts
+++ b/src/renderer/types.d.ts
@@ -211,6 +211,7 @@ export interface MetonaDesktopAPI {
   };
   fs: {
     readFile: (filePath: string) => Promise<{ success: boolean; content?: string; name?: string; error?: string }>;
+    readFileBase64: (filePath: string) => Promise<{ success: boolean; content?: string; size?: number; name?: string; error?: string }>;
     writeFile: (filePath: string, content: string, encoding?: string) => Promise<{ success: boolean; error?: string }>;
   };
   tool: {