diff --git a/src/backends/contracts.ts b/src/backends/contracts.ts
new file mode 100644
index 0000000..9e78172
--- /dev/null
+++ b/src/backends/contracts.ts
@@ -0,0 +1,50 @@
+export type BackendId = 'qianwen' | 'yuanbao' | (string & {});
+
+export type BackendLoginStatus = 'logged-in' | 'logged-out' | 'unknown';
+
+/** 主进程可安全使用的后端静态信息。 */
+export interface BackendDefinition {
+  readonly id: BackendId;
+  readonly label: string;
+  readonly url: string;
+  readonly origins: readonly string[];
+  readonly partition: string;
+  readonly editorSelector: string;
+}
+
+export interface BackendPageStatus {
+  readonly loginStatus: BackendLoginStatus;
+  /** 页面已经具备开始语音识别所需的编辑器和麦克风入口。 */
+  readonly ready: boolean;
+  readonly message?: string;
+}
+
+/** 仅在后端网页 preload 的渲染进程中调用。 */
+export interface BackendWebAdapter {
+  readonly definition: BackendDefinition;
+  readonly stopDelayMs: number;
+  findEditor(document: Document): HTMLElement | null;
+  findMicrophone(document: Document): HTMLElement | null;
+  serialize(editor: HTMLElement): string;
+  detectPageStatus(document: Document): BackendPageStatus;
+}
+
+export interface BackendControlCommand {
+  readonly backend: BackendId;
+  readonly action: 'start' | 'stop' | 'cancel' | 'refresh-status';
+}
+
+export interface BackendTranscriptPayload {
+  readonly backend: BackendId;
+  readonly text: string;
+  readonly revision: number;
+}
+
+export function backendOwnsUrl(definition: BackendDefinition, candidate: string): boolean {
+  try {
+    const origin = new URL(candidate).origin;
+    return definition.origins.includes(origin);
+  } catch {
+    return false;
+  }
+}
diff --git a/src/backends/definitions.ts b/src/backends/definitions.ts
new file mode 100644
index 0000000..64c5201
--- /dev/null
+++ b/src/backends/definitions.ts
@@ -0,0 +1,24 @@
+import type { BackendDefinition } from './contracts';
+
+export const qianwenDefinition: BackendDefinition = Object.freeze({
+  id: 'qianwen',
+  label: '千问',
+  url: 'https://www.qianwen.com/',
+  origins: Object.freeze(['https://www.qianwen.com']),
+  partition: 'persist:meloasr-qianwen',
+  editorSelector: '[data-slate-editor="true"][contenteditable="true"], [role="textbox"][contenteditable="true"]'
+});
+
+export const yuanbaoDefinition: BackendDefinition = Object.freeze({
+  id: 'yuanbao',
+  label: '元宝',
+  url: 'https://yuanbao.tencent.com/',
+  origins: Object.freeze(['https://yuanbao.tencent.com']),
+  partition: 'persist:meloasr-yuanbao',
+  editorSelector: '.ql-editor[contenteditable="true"], [contenteditable="true"][role="textbox"]'
+});
+
+export const backendDefinitions = Object.freeze([
+  qianwenDefinition,
+  yuanbaoDefinition
+] as const);
diff --git a/src/backends/dom.ts b/src/backends/dom.ts
new file mode 100644
index 0000000..18cd268
--- /dev/null
+++ b/src/backends/dom.ts
@@ -0,0 +1,58 @@
+import type { BackendLoginStatus, BackendPageStatus } from './contracts';
+
+export function isVisible(element: Element | null): element is HTMLElement {
+  if (!(element instanceof HTMLElement)) return false;
+  const style = getComputedStyle(element);
+  const rect = element.getBoundingClientRect();
+  return style.display !== 'none' && style.visibility !== 'hidden' && rect.width > 0 && rect.height > 0;
+}
+
+export function isUsableControl(element: Element | null): element is HTMLElement {
+  return isVisible(element) && !element.matches('[disabled], [aria-disabled="true"]');
+}
+
+export function firstVisible(document: Document, selector: string): HTMLElement | null {
+  const elements = Array.from(document.querySelectorAll(selector));
+  return elements.find(isVisible) ?? (elements[0] instanceof HTMLElement ? elements[0] : null);
+}
+
+export function controlDescription(element: Element): string {
+  return [
+    element.getAttribute('aria-label'),
+    element.getAttribute('title'),
+    element.getAttribute('data-tooltip'),
+    element.textContent,
+    element.getAttribute('class'),
+    element.querySelector('svg')?.getAttribute('class')
+  ].filter(Boolean).join(' ');
+}
+
+export function findSemanticControl(document: Document, pattern: RegExp): HTMLElement | null {
+  const control = Array.from(document.querySelectorAll('button, a, [role="button"]'))
+    .find((element) => pattern.test(controlDescription(element)) && isUsableControl(element));
+  return control instanceof HTMLElement ? control : null;
+}
+
+export function operationalStatus(
+  document: Document,
+  editor: HTMLElement | null,
+  microphone: HTMLElement | null,
+  loginPattern: RegExp
+): BackendPageStatus {
+  if (editor && microphone) return { loginStatus: 'logged-in', ready: true };
+  if (editor) {
+    return {
+      loginStatus: 'logged-in',
+      ready: false,
+      message: '语音入口尚未就绪'
+    };
+  }
+
+  const loginControl = findSemanticControl(document, loginPattern);
+  const loginStatus: BackendLoginStatus = loginControl ? 'logged-out' : 'unknown';
+  return {
+    loginStatus,
+    ready: false,
+    message: loginControl ? '尚未登录' : '页面尚未进入可语音输入状态'
+  };
+}
diff --git a/src/backends/index.ts b/src/backends/index.ts
new file mode 100644
index 0000000..d9281c1
--- /dev/null
+++ b/src/backends/index.ts
@@ -0,0 +1,15 @@
+export {
+  getBackend,
+  listBackends,
+  requireBackend
+} from './registry';
+export type {
+  BackendControlCommand,
+  BackendDefinition,
+  BackendId,
+  BackendLoginStatus,
+  BackendPageStatus,
+  BackendTranscriptPayload,
+  BackendWebAdapter
+} from './contracts';
+export { backendOwnsUrl } from './contracts';
diff --git a/src/backends/qianwen.ts b/src/backends/qianwen.ts
new file mode 100644
index 0000000..4f85749
--- /dev/null
+++ b/src/backends/qianwen.ts
@@ -0,0 +1,40 @@
+import type { BackendWebAdapter } from './contracts';
+import { qianwenDefinition } from './definitions';
+import { firstVisible, isUsableControl, operationalStatus } from './dom';
+
+export const qianwenAdapter: BackendWebAdapter = {
+  definition: qianwenDefinition,
+  stopDelayMs: 1_600,
+
+  findEditor(document) {
+    return firstVisible(document, qianwenDefinition.editorSelector);
+  },
+
+  findMicrophone(document) {
+    const anchor = document.querySelector('[data-global-speaking-guide-anchor]');
+    if (isUsableControl(anchor)) return anchor;
+    const icon = document.querySelector('[data-icon-type="qwpcicon-mic"]');
+    const control = icon?.closest('button, [role="button"], [data-global-speaking-guide-anchor]') ?? icon?.parentElement;
+    return control instanceof HTMLElement && isUsableControl(control) ? control : null;
+  },
+
+  serialize(editor) {
+    return Array.from(editor.children)
+      .filter((node) => node.nodeType === Node.ELEMENT_NODE)
+      .map((block) => {
+        const clone = block.cloneNode(true) as HTMLElement;
+        clone.querySelectorAll('[data-slate-placeholder], [data-slate-zero-width]').forEach((node) => node.remove());
+        return clone.textContent ?? '';
+      })
+      .join('\n');
+  },
+
+  detectPageStatus(document) {
+    return operationalStatus(
+      document,
+      this.findEditor(document),
+      this.findMicrophone(document),
+      /登录|注册|log\s*in|sign\s*in/i
+    );
+  }
+};
diff --git a/src/backends/registry.ts b/src/backends/registry.ts
new file mode 100644
index 0000000..e4205b7
--- /dev/null
+++ b/src/backends/registry.ts
@@ -0,0 +1,22 @@
+import type { BackendDefinition, BackendId } from './contracts';
+import { backendDefinitions } from './definitions';
+
+export type { BackendDefinition, BackendId, BackendWebAdapter } from './contracts';
+
+const definitionById = new Map<BackendId, BackendDefinition>(
+  backendDefinitions.map((definition) => [definition.id, definition] as const)
+);
+
+export function listBackends(): readonly BackendDefinition[] {
+  return backendDefinitions;
+}
+
+export function getBackend(id: string): BackendDefinition | undefined {
+  return definitionById.get(id);
+}
+
+export function requireBackend(id: string): BackendDefinition {
+  const definition = getBackend(id);
+  if (!definition) throw new Error(`未知后端：${id}`);
+  return definition;
+}
diff --git a/src/backends/web-registry.ts b/src/backends/web-registry.ts
new file mode 100644
index 0000000..84f0951
--- /dev/null
+++ b/src/backends/web-registry.ts
@@ -0,0 +1,13 @@
+import type { BackendId, BackendWebAdapter } from './contracts';
+import { qianwenAdapter } from './qianwen';
+import { yuanbaoAdapter } from './yuanbao';
+
+const adapterById = new Map<BackendId, BackendWebAdapter>(
+  [qianwenAdapter, yuanbaoAdapter]
+    .map((adapter) => [adapter.definition.id, adapter] as const)
+);
+
+/** 仅供后端网页 preload 使用。 */
+export function getBackendWebAdapter(id: string): BackendWebAdapter | undefined {
+  return adapterById.get(id);
+}
diff --git a/src/backends/yuanbao.ts b/src/backends/yuanbao.ts
new file mode 100644
index 0000000..f025b42
--- /dev/null
+++ b/src/backends/yuanbao.ts
@@ -0,0 +1,49 @@
+import type { BackendWebAdapter } from './contracts';
+import { yuanbaoDefinition } from './definitions';
+import { controlDescription, firstVisible, isUsableControl, operationalStatus } from './dom';
+
+export const yuanbaoAdapter: BackendWebAdapter = {
+  definition: yuanbaoDefinition,
+  stopDelayMs: 3_500,
+
+  findEditor(document) {
+    return firstVisible(document, yuanbaoDefinition.editorSelector);
+  },
+
+  findMicrophone(document) {
+    const directSelectors = [
+      '[data-testid*="voice-input" i]',
+      '[data-testid*="voice" i]',
+      '[class*="voice-input" i] button',
+      '[class*="voiceInput"] button',
+      'button[class*="voice" i]',
+      '[role="button"][class*="voice" i]'
+    ];
+    for (const selector of directSelectors) {
+      const element = document.querySelector(selector);
+      if (isUsableControl(element)) return element;
+    }
+
+    const control = Array.from(document.querySelectorAll('button, [role="button"]'))
+      .find((element) =>
+        /语音输入|开始语音|停止语音|voice.?input|microphone|mic\b/i.test(controlDescription(element)) &&
+        isUsableControl(element)
+      );
+    return control instanceof HTMLElement ? control : null;
+  },
+
+  serialize(editor) {
+    const clone = editor.cloneNode(true) as HTMLElement;
+    const text = clone.innerText ?? clone.textContent ?? '';
+    return text.replace(/\n$/, '');
+  },
+
+  detectPageStatus(document) {
+    return operationalStatus(
+      document,
+      this.findEditor(document),
+      this.findMicrophone(document),
+      /登录|微信登录|QQ登录|手机号登录|log\s*in|sign\s*in/i
+    );
+  }
+};
diff --git a/src/preload/backend.ts b/src/preload/backend.ts
new file mode 100644
index 0000000..2cd7dad
--- /dev/null
+++ b/src/preload/backend.ts
@@ -0,0 +1,175 @@
+import { ipcRenderer } from 'electron';
+import type { BackendControlCommand, BackendPageStatus, BackendTranscriptPayload } from '../backends/contracts';
+import { getBackendWebAdapter } from '../backends/web-registry';
+
+const backendId = process.argv
+  .find((argument) => argument.startsWith('--meloasr-backend='))
+  ?.slice('--meloasr-backend='.length) ?? '';
+const adapter = getBackendWebAdapter(backendId);
+
+let editorObserver: MutationObserver | undefined;
+let pageObserver: MutationObserver | undefined;
+let active = false;
+let stopping = false;
+let lastSpeechText = '';
+let emitScheduled = false;
+let stopTimer: ReturnType<typeof setTimeout> | undefined;
+let statusTimer: ReturnType<typeof setTimeout> | undefined;
+let transcriptRevision = 0;
+let lastStatusKey = '';
+
+function emit(channel: string, value: Record<string, unknown> = {}): void {
+  ipcRenderer.send(channel, { backend: backendId, ...value });
+}
+
+function statusKey(status: BackendPageStatus): string {
+  return JSON.stringify([status.loginStatus, status.ready, status.message ?? '']);
+}
+
+function emitPageStatus(force = false): void {
+  if (!adapter) return;
+  const status = adapter.detectPageStatus(document);
+  const key = statusKey(status);
+  if (!force && key === lastStatusKey) return;
+  lastStatusKey = key;
+  emit('backend-status', {
+    ready: status.ready,
+    loggedIn: status.loginStatus === 'unknown' ? null : status.loginStatus === 'logged-in',
+    detail: status.message ?? ''
+  });
+}
+
+function schedulePageStatus(): void {
+  clearTimeout(statusTimer);
+  statusTimer = setTimeout(() => emitPageStatus(), 200);
+}
+
+function emitCurrentEditorText(): void {
+  emitScheduled = false;
+  if (!active || !adapter) return;
+  const editor = adapter.findEditor(document);
+  if (!editor) {
+    fail(`${adapter.definition.label}输入框在录音期间消失，本轮已停止`);
+    return;
+  }
+  const text = adapter.serialize(editor);
+  if (text === lastSpeechText) return;
+  lastSpeechText = text;
+  transcriptRevision += 1;
+  const payload: Omit<BackendTranscriptPayload, 'backend'> = { text, revision: transcriptRevision };
+  emit('backend-transcript', payload);
+}
+
+function scheduleTranscript(): void {
+  if (emitScheduled || !active) return;
+  emitScheduled = true;
+  requestAnimationFrame(emitCurrentEditorText);
+}
+
+function observeEditor(editor: HTMLElement): void {
+  editorObserver?.disconnect();
+  editorObserver = new MutationObserver(scheduleTranscript);
+  editorObserver.observe(editor, {
+    subtree: true,
+    childList: true,
+    characterData: true,
+    attributes: true,
+    attributeFilter: ['class']
+  });
+}
+
+function placeCaretAtEnd(editor: HTMLElement): void {
+  editor.focus({ preventScroll: true });
+  const selection = window.getSelection();
+  if (!selection) return;
+  const range = document.createRange();
+  range.selectNodeContents(editor);
+  range.collapse(false);
+  selection.removeAllRanges();
+  selection.addRange(range);
+}
+
+function resetSession(): void {
+  clearTimeout(stopTimer);
+  active = false;
+  stopping = false;
+  editorObserver?.disconnect();
+}
+
+function fail(message: string): void {
+  resetSession();
+  emit('backend-start-error', { message });
+  emitPageStatus(true);
+}
+
+function startSpeech(): void {
+  if (!adapter) return;
+  const status = adapter.detectPageStatus(document);
+  if (!status.ready) {
+    fail(status.loginStatus === 'logged-out'
+      ? `${adapter.definition.label}尚未登录，请先打开登录页面`
+      : `${adapter.definition.label}页面尚未就绪，请打开后端页面并进入对话页`);
+    return;
+  }
+
+  const editor = adapter.findEditor(document);
+  const microphone = adapter.findMicrophone(document);
+  if (!editor || !microphone) {
+    fail(`没有找到${adapter.definition.label}输入框或麦克风按钮`);
+    return;
+  }
+
+  clearTimeout(stopTimer);
+  placeCaretAtEnd(editor);
+  lastSpeechText = adapter.serialize(editor);
+  transcriptRevision = 0;
+  active = true;
+  stopping = false;
+  observeEditor(editor);
+  microphone.click();
+}
+
+function stopSpeech(): void {
+  if (!active || stopping || !adapter) return;
+  stopping = true;
+  adapter.findMicrophone(document)?.click();
+  clearTimeout(stopTimer);
+  stopTimer = setTimeout(() => {
+    emitCurrentEditorText();
+    resetSession();
+    emit('backend-session-ended', { text: lastSpeechText, revision: transcriptRevision });
+    emitPageStatus(true);
+  }, adapter.stopDelayMs);
+}
+
+function cancelSpeech(): void {
+  if (!active || !adapter) return;
+  adapter.findMicrophone(document)?.click();
+  resetSession();
+  lastSpeechText = '';
+}
+
+ipcRenderer.on('backend-control', (_event, command: BackendControlCommand) => {
+  if (!adapter || command.backend !== backendId) return;
+  if (command.action === 'start') startSpeech();
+  if (command.action === 'stop') stopSpeech();
+  if (command.action === 'cancel') cancelSpeech();
+  if (command.action === 'refresh-status') emitPageStatus(true);
+});
+
+if (adapter) {
+  const startStatusObserver = (): void => {
+    emitPageStatus(true);
+    pageObserver?.disconnect();
+    pageObserver = new MutationObserver(schedulePageStatus);
+    pageObserver.observe(document.documentElement, { subtree: true, childList: true });
+    window.setInterval(() => emitPageStatus(), 5_000);
+  };
+  if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', startStatusObserver, { once: true });
+  } else {
+    startStatusObserver();
+  }
+} else {
+  emit('backend-start-error', { message: `未知后端：${backendId || '未指定'}` });
+}
diff --git a/test/backends.test.ts b/test/backends.test.ts
new file mode 100644
index 0000000..57b068a
--- /dev/null
+++ b/test/backends.test.ts
@@ -0,0 +1,20 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { backendOwnsUrl } from '../src/backends/contracts';
+import { getBackend, listBackends, requireBackend } from '../src/backends/registry';
+
+test('后端注册表包含千问和元宝且 ID 唯一', () => {
+  const backends = listBackends();
+  assert.deepEqual(backends.map(({ id }) => id), ['qianwen', 'yuanbao']);
+  assert.equal(new Set(backends.map(({ id }) => id)).size, backends.length);
+  assert.equal(getBackend('qianwen')?.label, '千问');
+  assert.equal(getBackend('missing'), undefined);
+  assert.throws(() => requireBackend('missing'), /未知后端/);
+});
+
+test('后端 URL 校验使用精确 origin', () => {
+  const qianwen = requireBackend('qianwen');
+  assert.equal(backendOwnsUrl(qianwen, 'https://www.qianwen.com/chat/1'), true);
+  assert.equal(backendOwnsUrl(qianwen, 'https://www.qianwen.com.evil.example/'), false);
+  assert.equal(backendOwnsUrl(qianwen, 'not a url'), false);
+});