diff --git a/apps/sidecar/src/index.ts b/apps/sidecar/src/index.ts
index 21f3d93d..c23d72cc 100644
--- a/apps/sidecar/src/index.ts
+++ b/apps/sidecar/src/index.ts
@@ -25,7 +25,7 @@ import {
 } from "./services/infra/logger";
 import { assertSidecarNativeRuntime } from "./services/infra/native-runtime";
 import { createProcessRpcTransport, MAX_RPC_MESSAGE_BYTES } from "./rpc/process-transport";
-import { classifyBrowserRpcResponse } from "./rpc/browser-rpc-sequence";
+import { browserRpcErrorFromPayload, classifyBrowserRpcResponse } from "./rpc/browser-rpc-sequence";
 import { createReverseRpcRenderClient } from "./services/agent-runtime/tools/web/reverse-rpc-render-client";
 import { setSidecarRenderClient } from "./services/agent-runtime/tools/web/render-client-holder";
 import { setPersistedSettingsMutationWriter } from "./services/system/settings-store";
@@ -204,7 +204,7 @@ async function handleRpcLine(line: string): Promise<void> {
       return;
     }
     const response = responsePayload;
-    if (response.error) pending.reject(new Error("browser request failed"));
+    if (response.error) pending.reject(browserRpcErrorFromPayload(response.error));
     else pending.resolve(response.result);
     return;
   }
diff --git a/apps/sidecar/src/rpc/browser-rpc-sequence.test.ts b/apps/sidecar/src/rpc/browser-rpc-sequence.test.ts
index 8f64426b..17a1cc9f 100644
--- a/apps/sidecar/src/rpc/browser-rpc-sequence.test.ts
+++ b/apps/sidecar/src/rpc/browser-rpc-sequence.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { classifyBrowserRpcResponse } from "./browser-rpc-sequence";
+import { browserRpcErrorFromPayload, classifyBrowserRpcResponse } from "./browser-rpc-sequence";
 
 describe("classifyBrowserRpcResponse（#156 序列号单调判定）", () => {
   test("正常路径：MAC 有效且序号 = 当前 +1 → advance", () => {
@@ -21,3 +21,19 @@ describe("classifyBrowserRpcResponse（#156 序列号单调判定）", () => {
     expect(classifyBrowserRpcResponse(9, false, 0)).toBe("reject-pending");
   });
 });
+
+describe("browserRpcErrorFromPayload（#252 错误码传播）", () => {
+  test("保留 Desktop 返回的稳定错误码", () => {
+    const error = browserRpcErrorFromPayload({ code: "actionability_failed" });
+
+    expect(error.code).toBe("actionability_failed");
+    expect(error.message).toBe("actionability_failed");
+  });
+
+  test("无效错误载荷安全退化为 browser_internal_error", () => {
+    const error = browserRpcErrorFromPayload(undefined);
+
+    expect(error.code).toBe("browser_internal_error");
+    expect(error.message).toBe("browser_internal_error");
+  });
+});
diff --git a/apps/sidecar/src/rpc/browser-rpc-sequence.ts b/apps/sidecar/src/rpc/browser-rpc-sequence.ts
index dca5d113..ee77c2d9 100644
--- a/apps/sidecar/src/rpc/browser-rpc-sequence.ts
+++ b/apps/sidecar/src/rpc/browser-rpc-sequence.ts
@@ -15,3 +15,19 @@ export function classifyBrowserRpcResponse(
   if (!macOk || sequence <= inboundSequence) return "reject-pending";
   return "advance";
 }
+
+export class BrowserRpcError extends Error {
+  readonly code: string;
+
+  constructor(code: string, message = code) {
+    super(message);
+    this.name = "BrowserRpcError";
+    this.code = code;
+  }
+}
+
+export function browserRpcErrorFromPayload(error: { code?: unknown; message?: unknown } | undefined): BrowserRpcError {
+  const code = typeof error?.code === "string" && error.code ? error.code : "browser_internal_error";
+  const message = typeof error?.message === "string" && error.message ? error.message : code;
+  return new BrowserRpcError(code, message);
+}
diff --git a/apps/sidecar/src/services/browser/browser-broker.test.ts b/apps/sidecar/src/services/browser/browser-broker.test.ts
index c4b86b13..7128e007 100644
--- a/apps/sidecar/src/services/browser/browser-broker.test.ts
+++ b/apps/sidecar/src/services/browser/browser-broker.test.ts
@@ -1,6 +1,7 @@
 import { strict as assert } from "node:assert";
 import { test } from "node:test";
 import { BrowserBroker } from "./browser-broker";
+import { BrowserRpcError } from "../../rpc/browser-rpc-sequence";
 
 test("extension backend is absent until browser/chrome plugins, setting, and live host agree", async () => {
   const calls: unknown[] = [];
@@ -18,6 +19,18 @@ test("extension backend is absent until browser/chrome plugins, setting, and liv
   assert.equal(calls.length, 0);
 });
 
+test("broker preserves a structured Desktop browser error code", async () => {
+  const broker = new BrowserBroker({
+    request: async () => { throw new BrowserRpcError("actionability_failed", "browser request failed"); },
+  });
+  broker.setPluginState({ browserEnabled: true });
+
+  await assert.rejects(
+    () => broker.dispatch({ method: "playwright_locator_fill", params: { tabId: "tab-1", locator: { version: 1, steps: [{ kind: "css", selector: "#kw" }] }, value: "agent loop" }, browserSessionId: "s", browserTurnId: "t" }),
+    /actionability_failed/,
+  );
+});
+
 test("connected Chrome cookie export is capability-gated, user-only, and paged", async () => {
   const calls: any[] = []
   const broker = new BrowserBroker(
diff --git a/apps/sidecar/src/services/browser/browser-broker.ts b/apps/sidecar/src/services/browser/browser-broker.ts
index 723192dd..4cb32053 100644
--- a/apps/sidecar/src/services/browser/browser-broker.ts
+++ b/apps/sidecar/src/services/browser/browser-broker.ts
@@ -425,7 +425,10 @@ function stableJson(value: unknown): string {
   return JSON.stringify(value) ?? "null"
 }
 function stableBrowserErrorCode(error: unknown): string {
-  const value = error instanceof Error ? error.message : ""
+  const structuredCode = error && typeof error === "object" && typeof (error as { code?: unknown }).code === "string"
+    ? (error as { code: string }).code
+    : ""
+  const value = structuredCode || (error instanceof Error ? error.message : "")
   return new Set(["browser_unavailable", "invalid_browser_request", "invalid_url", "private_origin_confirmation_required", "stale_target", "tab_not_found", "tab_generation_changed", "confirmation_unavailable", "reference_grant_expired", "action_denied", "strict_locator_violation", "actionability_failed", "dialog_blocking", "unsupported", "executed_unknown"]).has(value) ? value : "browser_internal_error"
 }