diff --git a/frontend-web/src/pages/IframeChatPage.tsx b/frontend-web/src/pages/IframeChatPage.tsx
index 79f37082..821b0ef5 100644
--- a/frontend-web/src/pages/IframeChatPage.tsx
+++ b/frontend-web/src/pages/IframeChatPage.tsx
@@ -30,21 +30,10 @@ import { useThreadStream } from "@/core/threads/hooks";
 import { textOfMessage } from "@/core/threads/utils";
 import { env } from "@/env";
 import { cn } from "@/lib/utils";
-
-type BrainyChatSubmitMessage = {
-  source?: string;
-  type?: string;
-  payload?: {
-    text?: string;
-    prompt?: string;
-    pageContext?: {
-      title?: string;
-      content?: string;
-      url?: string;
-    };
-  };
-  requestId?: string;
-};
+import {
+  type BrainyChatSubmitMessage,
+  parseBrainyChatSubmitMessage,
+} from "./iframe-chat-submit";
 
 type BrainyChatStatus = "started" | "finished";
 
@@ -62,47 +51,6 @@ function postBrainyChatStatus(status: BrainyChatStatus, requestId: string) {
   );
 }
 
-function buildIframeMessageText({
-  text,
-  prompt,
-  pageContext,
-}: {
-  text: string;
-  prompt: string;
-  pageContext?:
-    | {
-        title?: string;
-        content?: string;
-        url?: string;
-      }
-    | undefined;
-}) {
-  const primaryText = text || prompt;
-  const sections = [primaryText];
-
-  if (prompt && prompt !== primaryText) {
-    sections.push(`<extension_prompt>\n${prompt}\n</extension_prompt>`);
-  }
-
-  if (pageContext) {
-    const pageContextParts = [
-      pageContext.title ? `<title>\n${pageContext.title}\n</title>` : null,
-      pageContext.url ? `<url>\n${pageContext.url}\n</url>` : null,
-      pageContext.content
-        ? `<content>\n${pageContext.content}\n</content>`
-        : null,
-    ].filter(Boolean);
-
-    if (pageContextParts.length > 0) {
-      sections.push(
-        `<page_context>\n${pageContextParts.join("\n\n")}\n</page_context>`,
-      );
-    }
-  }
-
-  return sections.join("\n\n");
-}
-
 export default function IframeChatPage() {
   const routeBase = useRouteBase();
   const router = useRouter();
@@ -265,44 +213,23 @@ export default function IframeChatPage() {
       if (data?.source !== "brainy-extension") return;
       if (data?.type !== "brainy:chat-submit") return;
 
-      const text = data.payload?.text?.trim() ?? "";
-      const prompt = data.payload?.prompt?.trim() ?? "";
-      const rawPageContext = data.payload?.pageContext;
-      const pageContext = rawPageContext
-        ? {
-            ...(rawPageContext.title?.trim()
-              ? { title: rawPageContext.title.trim() }
-              : {}),
-            ...(rawPageContext.content?.trim()
-              ? { content: rawPageContext.content.trim() }
-              : {}),
-            ...(rawPageContext.url?.trim()
-              ? { url: rawPageContext.url.trim() }
-              : {}),
-          }
-        : undefined;
-      const submitText = buildIframeMessageText({ text, prompt, pageContext });
+      const { submitText, files, iframeContext } =
+        parseBrainyChatSubmitMessage(data);
 
       console.log("收到插件消息", {
-        text,
-        prompt,
-        pageContext,
+        text: data.payload?.text,
+        prompt: data.payload?.prompt,
+        pageContext: data.payload?.pageContext,
+        screenshot: data.payload?.screenshot,
         requestId: data.requestId,
+        filesCount: files.length,
       });
 
-      if (!submitText) return;
+      if (!submitText && files.length === 0) return;
 
       pendingRequestIdRef.current = data.requestId ?? null;
 
-      const iframeContext: Record<string, unknown> = {};
-      if (data.requestId) {
-        iframeContext.brainy_request_id = data.requestId;
-      }
-
-      handleSubmit(
-        { text: submitText, files: [] },
-        Object.keys(iframeContext).length > 0 ? iframeContext : undefined,
-      );
+      handleSubmit({ text: submitText, files }, iframeContext);
     };
 
     window.addEventListener("message", handleMessage);
diff --git a/frontend-web/src/pages/iframe-chat-submit.test.ts b/frontend-web/src/pages/iframe-chat-submit.test.ts
new file mode 100644
index 00000000..690570fd
--- /dev/null
+++ b/frontend-web/src/pages/iframe-chat-submit.test.ts
@@ -0,0 +1,71 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { parseBrainyChatSubmitMessage } from "./iframe-chat-submit";
+
+test("parses iframe text, page context, and screenshot into a prompt message", () => {
+  const result = parseBrainyChatSubmitMessage({
+    source: "brainy-extension",
+    type: "brainy:chat-submit",
+    requestId: "iframe-123",
+    payload: {
+      text: "提取并翻译",
+      prompt: "提取图片中的文字并翻译成简体中文",
+      pageContext: {
+        title: "UN News",
+        content: "Banning children from social media is not the answer.",
+        url: "https://news.un.org/example",
+      },
+      screenshot: {
+        dataUrl: "data:image/png;base64,aGVsbG8=",
+        fileName: "capture.png",
+        images: [
+          {
+            filename: "capture.png",
+            url: "C:\\Users\\Rocky\\AppData\\Local\\Temp\\capture.png",
+            size: 0,
+          },
+        ],
+      },
+    },
+  });
+
+  assert.equal(result.submitText, [
+    "提取并翻译",
+    "<extension_prompt>\n提取图片中的文字并翻译成简体中文\n</extension_prompt>",
+    "<page_context>\n<title>\nUN News\n</title>\n\n<url>\nhttps://news.un.org/example\n</url>\n\n<content>\nBanning children from social media is not the answer.\n</content>\n</page_context>",
+  ].join("\n\n"));
+  assert.deepEqual(result.iframeContext, { brainy_request_id: "iframe-123" });
+  assert.equal(result.files.length, 1);
+  assert.equal(result.files[0]?.type, "file");
+  assert.equal(result.files[0]?.filename, "capture.png");
+  assert.equal(result.files[0]?.mediaType, "image/png");
+  assert.ok(result.files[0]?.file instanceof File);
+  assert.equal(result.files[0]?.file?.name, "capture.png");
+  assert.equal(result.files[0]?.file?.type, "image/png");
+  assert.equal(result.files[0]?.url, "data:image/png;base64,aGVsbG8=");
+});
+
+test("keeps screenshot-only iframe submissions in the conversation flow", () => {
+  const result = parseBrainyChatSubmitMessage({
+    source: "brainy-extension",
+    type: "brainy:chat-submit",
+    payload: {
+      screenshot: {
+        dataUrl: "data:image/jpeg;base64,aGVsbG8=",
+        images: [
+          {
+            filename: "shot.jpg",
+            url: "C:\\Users\\Rocky\\AppData\\Local\\Temp\\shot.jpg",
+            size: 0,
+          },
+        ],
+      },
+    },
+  });
+
+  assert.equal(result.submitText, "");
+  assert.equal(result.files.length, 1);
+  assert.equal(result.files[0]?.filename, "shot.jpg");
+  assert.equal(result.files[0]?.mediaType, "image/jpeg");
+});
diff --git a/frontend-web/src/pages/iframe-chat-submit.ts b/frontend-web/src/pages/iframe-chat-submit.ts
new file mode 100644
index 00000000..c7583900
--- /dev/null
+++ b/frontend-web/src/pages/iframe-chat-submit.ts
@@ -0,0 +1,247 @@
+type BrainyPageContext = {
+  title?: string;
+  content?: string;
+  url?: string;
+};
+
+type BrainyScreenshotPath = {
+  image_url?: string;
+};
+
+type BrainyScreenshotImage = {
+  filename?: string;
+  url?: string;
+  size?: number;
+};
+
+type BrainyScreenshot = {
+  dataUrl?: string;
+  fileName?: string;
+  filePath?: BrainyScreenshotPath[];
+  images?: BrainyScreenshotImage[];
+};
+
+export type BrainyChatSubmitMessage = {
+  source?: string;
+  type?: string;
+  payload?: {
+    text?: string;
+    prompt?: string;
+    pageContext?: BrainyPageContext;
+    screenshot?: BrainyScreenshot;
+  };
+  requestId?: string;
+};
+
+export type IframePromptInputFilePart = {
+  type: "file";
+  url: string;
+  mediaType: string;
+  filename: string;
+  file?: File;
+};
+
+export type ParsedBrainyChatSubmitMessage = {
+  submitText: string;
+  files: IframePromptInputFilePart[];
+  iframeContext?: Record<string, unknown>;
+};
+
+function trimToUndefined(value: string | undefined): string | undefined {
+  const trimmed = value?.trim();
+  return trimmed ? trimmed : undefined;
+}
+
+function fileNameFromPath(path: string | undefined): string | undefined {
+  if (!path) return undefined;
+  const parts = path.split(/[\\/]/).filter(Boolean);
+  return parts.at(-1);
+}
+
+function isLikelyLocalPath(path: string): boolean {
+  return /^[a-zA-Z]:[\\/]/.test(path) || path.startsWith("\\\\");
+}
+
+function mimeTypeFromFilename(filename: string | undefined): string | undefined {
+  const lower = filename?.toLowerCase() ?? "";
+  if (lower.endsWith(".png")) return "image/png";
+  if (lower.endsWith(".jpg") || lower.endsWith(".jpeg")) return "image/jpeg";
+  if (lower.endsWith(".webp")) return "image/webp";
+  if (lower.endsWith(".gif")) return "image/gif";
+  return undefined;
+}
+
+function parseDataUrlMeta(dataUrl: string): { mimeType: string; payload: string } | null {
+  const match = /^data:([^;,]+)?(?:;base64)?,(.*)$/i.exec(dataUrl);
+  if (!match) return null;
+  return {
+    mimeType: match[1] || "application/octet-stream",
+    payload: match[2] || "",
+  };
+}
+
+function decodeBase64(base64: string): Uint8Array {
+  if (typeof Buffer !== "undefined") {
+    return Uint8Array.from(Buffer.from(base64, "base64"));
+  }
+
+  const binary = atob(base64);
+  const bytes = new Uint8Array(binary.length);
+  for (let i = 0; i < binary.length; i += 1) {
+    bytes[i] = binary.charCodeAt(i);
+  }
+  return bytes;
+}
+
+function fileFromDataUrl(
+  dataUrl: string,
+  filename: string,
+  mediaType: string,
+): File | undefined {
+  const meta = parseDataUrlMeta(dataUrl);
+  if (!meta) return undefined;
+
+  const bytes = decodeBase64(meta.payload);
+  const arrayBuffer = bytes.buffer.slice(
+    bytes.byteOffset,
+    bytes.byteOffset + bytes.byteLength,
+  );
+
+  return new File([arrayBuffer], filename, {
+    type: mediaType || meta.mimeType,
+  });
+}
+
+function normalizePageContext(
+  pageContext: BrainyPageContext | undefined,
+): BrainyPageContext | undefined {
+  if (!pageContext) return undefined;
+
+  const normalized = {
+    title: trimToUndefined(pageContext.title),
+    content: trimToUndefined(pageContext.content),
+    url: trimToUndefined(pageContext.url),
+  };
+
+  return normalized.title || normalized.content || normalized.url
+    ? normalized
+    : undefined;
+}
+
+export function buildIframeMessageText({
+  text,
+  prompt,
+  pageContext,
+}: {
+  text?: string;
+  prompt?: string;
+  pageContext?: BrainyPageContext;
+}) {
+  const primaryText = trimToUndefined(text) || trimToUndefined(prompt) || "";
+  const sections: string[] = [];
+
+  if (primaryText) {
+    sections.push(primaryText);
+  }
+
+  const normalizedPrompt = trimToUndefined(prompt);
+  if (normalizedPrompt && normalizedPrompt !== primaryText) {
+    sections.push(
+      `<extension_prompt>\n${normalizedPrompt}\n</extension_prompt>`,
+    );
+  }
+
+  const normalizedPageContext = normalizePageContext(pageContext);
+  if (normalizedPageContext) {
+    const pageContextParts = [
+      normalizedPageContext.title
+        ? `<title>\n${normalizedPageContext.title}\n</title>`
+        : null,
+      normalizedPageContext.url
+        ? `<url>\n${normalizedPageContext.url}\n</url>`
+        : null,
+      normalizedPageContext.content
+        ? `<content>\n${normalizedPageContext.content}\n</content>`
+        : null,
+    ].filter(Boolean);
+
+    if (pageContextParts.length > 0) {
+      sections.push(
+        `<page_context>\n${pageContextParts.join("\n\n")}\n</page_context>`,
+      );
+    }
+  }
+
+  return sections.join("\n\n");
+}
+
+function buildScreenshotFileParts(
+  screenshot: BrainyScreenshot | undefined,
+): IframePromptInputFilePart[] {
+  if (!screenshot) return [];
+
+  const fallbackPath =
+    screenshot.filePath?.map((item) => item.image_url).find(Boolean) ??
+    screenshot.images?.map((item) => item.url).find(Boolean);
+  const fallbackFilename =
+    trimToUndefined(screenshot.fileName) ??
+    screenshot.images?.map((item) => trimToUndefined(item.filename)).find(Boolean) ??
+    fileNameFromPath(fallbackPath) ??
+    "screenshot.png";
+
+  const dataUrl = trimToUndefined(screenshot.dataUrl);
+  if (dataUrl) {
+    const parsed = parseDataUrlMeta(dataUrl);
+    const mediaType =
+      parsed?.mimeType || mimeTypeFromFilename(fallbackFilename) || "image/png";
+    const file = fileFromDataUrl(dataUrl, fallbackFilename, mediaType);
+
+    return [
+      {
+        type: "file",
+        url: dataUrl,
+        mediaType,
+        filename: fallbackFilename,
+        ...(file ? { file } : {}),
+      },
+    ];
+  }
+
+  const remoteImage = screenshot.images?.find((item) => {
+    const url = trimToUndefined(item.url);
+    return !!url && !isLikelyLocalPath(url);
+  });
+
+  if (remoteImage?.url && remoteImage.filename) {
+    return [
+      {
+        type: "file",
+        url: remoteImage.url,
+        mediaType:
+          mimeTypeFromFilename(remoteImage.filename) || "application/octet-stream",
+        filename: remoteImage.filename,
+      },
+    ];
+  }
+
+  return [];
+}
+
+export function parseBrainyChatSubmitMessage(
+  data: BrainyChatSubmitMessage,
+): ParsedBrainyChatSubmitMessage {
+  const text = trimToUndefined(data.payload?.text);
+  const prompt = trimToUndefined(data.payload?.prompt);
+  const pageContext = normalizePageContext(data.payload?.pageContext);
+  const submitText = buildIframeMessageText({ text, prompt, pageContext });
+  const files = buildScreenshotFileParts(data.payload?.screenshot);
+  const requestId = trimToUndefined(data.requestId);
+
+  return {
+    submitText,
+    files,
+    ...(requestId
+      ? { iframeContext: { brainy_request_id: requestId } }
+      : {}),
+  };
+}