diff --git a/extensions/whatsapp/src/setup-finalize.ts b/extensions/whatsapp/src/setup-finalize.ts
index 05314877e9b..f0e3a1b94e1 100644
--- a/extensions/whatsapp/src/setup-finalize.ts
+++ b/extensions/whatsapp/src/setup-finalize.ts
@@ -10,7 +10,11 @@ import {
 } from "openclaw/plugin-sdk/setup";
 import type { ChannelSetupWizard } from "openclaw/plugin-sdk/setup";
 import { formatCliCommand, formatDocsLink } from "openclaw/plugin-sdk/setup-tools";
-import { resolveWhatsAppAccount, resolveWhatsAppAuthDir } from "./accounts.js";
+import {
+  resolveDefaultWhatsAppAccountId,
+  resolveWhatsAppAccount,
+  resolveWhatsAppAuthDir,
+} from "./accounts.js";
 import { loginWeb } from "./login.js";
 import { whatsappSetupAdapter } from "./setup-core.js";
 
@@ -333,19 +337,20 @@ export async function finalizeWhatsAppSetup(params: {
   prompter: SetupPrompter;
   runtime: SetupRuntime;
 }) {
+  const accountId = params.accountId.trim() || resolveDefaultWhatsAppAccountId(params.cfg);
   let next =
-    params.accountId === DEFAULT_ACCOUNT_ID
+    accountId === DEFAULT_ACCOUNT_ID
       ? params.cfg
       : whatsappSetupAdapter.applyAccountConfig({
           cfg: params.cfg,
-          accountId: params.accountId,
+          accountId,
           input: {},
         });
 
-  const linked = await detectWhatsAppLinked(next, params.accountId);
+  const linked = await detectWhatsAppLinked(next, accountId);
   const { authDir } = resolveWhatsAppAuthDir({
     cfg: next,
-    accountId: params.accountId,
+    accountId,
   });
 
   if (!linked) {
@@ -365,7 +370,7 @@ export async function finalizeWhatsAppSetup(params: {
   });
   if (wantsLink) {
     try {
-      await loginWeb(false, undefined, params.runtime, params.accountId);
+      await loginWeb(false, undefined, params.runtime, accountId);
     } catch (error) {
       params.runtime.error(`WhatsApp login failed: ${String(error)}`);
       await params.prompter.note(
@@ -382,7 +387,7 @@ export async function finalizeWhatsAppSetup(params: {
 
   next = await promptWhatsAppDmAccess({
     cfg: next,
-    accountId: params.accountId,
+    accountId,
     forceAllowFrom: params.forceAllowFrom,
     prompter: params.prompter,
   });
diff --git a/extensions/whatsapp/src/setup-surface.test.ts b/extensions/whatsapp/src/setup-surface.test.ts
index 0ea3e6cc9d1..6d23e2142a3 100644
--- a/extensions/whatsapp/src/setup-surface.test.ts
+++ b/extensions/whatsapp/src/setup-surface.test.ts
@@ -248,6 +248,45 @@ describe("whatsapp setup wizard", () => {
     );
   });
 
+  it("uses configured defaultAccount for omitted-account finalize writes", async () => {
+    hoisted.pathExists.mockResolvedValue(true);
+    const harness = createSeparatePhoneHarness({
+      selectValues: ["separate", "open"],
+    });
+
+    const result = expectFinalizeResult(
+      await runFinalizeWithHarness({
+        harness,
+        accountId: "",
+        cfg: {
+          channels: {
+            whatsapp: {
+              defaultAccount: "work",
+              dmPolicy: "disabled",
+              allowFrom: ["+15555550123"],
+              accounts: {
+                work: {
+                  authDir: "/tmp/work",
+                },
+              },
+            },
+          },
+        },
+      }),
+    );
+
+    expect(result.cfg.channels?.whatsapp?.dmPolicy).toBe("disabled");
+    expect(result.cfg.channels?.whatsapp?.allowFrom).toEqual(["+15555550123"]);
+    expect(result.cfg.channels?.whatsapp?.accounts?.work?.dmPolicy).toBe("open");
+    expect(result.cfg.channels?.whatsapp?.accounts?.work?.allowFrom).toEqual(["*", "+15555550123"]);
+    expect(harness.note).toHaveBeenCalledWith(
+      expect.stringContaining(
+        "`channels.whatsapp.accounts.work.dmPolicy` + `channels.whatsapp.accounts.work.allowFrom`",
+      ),
+      "WhatsApp DM access",
+    );
+  });
+
   it("normalizes allowFrom entries when list mode is selected", async () => {
     const { result } = await runSeparatePhoneFlow({
       selectValues: ["separate", "allowlist", "list"],