diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58a96348517f..0d8981242672 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,7 @@ Docs: https://docs.openclaw.ai
 
 ### Changes
 
-- **Standalone browser relay:** ship a gateway-free extension relay daemon (`dist/extensions/browser/relay-daemon-entry.js`) and teach the native messaging host a rate-limited `ensure_relay` op, so the Chrome extension can wake the relay on demand and CDP clients (mcporter, Playwright) drive the paired browser without a running Gateway. The standalone daemon is v2-only by default (it never re-enables legacy one-directional auth unless `browser.extensionRelay.allowLegacyAuth=true` is set explicitly), so a process that squats the relay port cannot harvest the secret from a legacy client.
+- **Standalone browser relay:** ship a gateway-free extension relay daemon (`dist/extensions/browser/relay-daemon-entry.js`) and teach the native messaging host a rate-limited `ensure_relay` op, so the Chrome extension can wake the relay on demand and CDP clients (mcporter, Playwright) drive the paired browser without a running Gateway. The standalone daemon is v2-only by default (it never re-enables legacy one-directional auth unless `browser.extensionRelay.allowLegacyAuth=true` is set explicitly), so a process that squats the relay port cannot harvest the secret from a legacy client. The relay secret is also re-checked for owner and `0600` mode on every read (self-healing a drifted mode, refusing a foreign-owned or non-regular file), so a permission drift on a shared host can no longer expose it.
 - **Secret egress host binding:** bind each shared-store secret to exact HTTPS destination hosts across CLI, Gateway RPC, and Control UI so unbound sentinel substitution fails closed before plaintext egress.
 - **Release validation:** defer beta candidate Parallels smoke to postpublish `release:beta-smoke` by default, keep stable/full prepublish coverage, and bound nested release workflow monitors with explicit job timeouts.
 - **macOS app profiles:** isolate named app instances across state, preferences, Keychain, Gateway services, and duplicate-instance ownership while keeping host-global login and node services untouched.
diff --git a/extensions/browser/src/browser/extension-relay/relay-auth.test.ts b/extensions/browser/src/browser/extension-relay/relay-auth.test.ts
index 44c95cd80b00..ba51297482c6 100644
--- a/extensions/browser/src/browser/extension-relay/relay-auth.test.ts
+++ b/extensions/browser/src/browser/extension-relay/relay-auth.test.ts
@@ -4,6 +4,7 @@ import os from "node:os";
 import path from "node:path";
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
 import {
+  classifyRelaySecretPrivacy,
   ensureExtensionRelayToken,
   readExtensionRelayToken,
   resolveExtensionRelayToken,
@@ -68,4 +69,49 @@ describe("extension relay host-local secret", () => {
       fs.rmSync(otherDir, { recursive: true, force: true });
     }
   });
+
+  const secretFilePath = (): string =>
+    path.join(stateDir, "credentials", "browser-extension-relay.secret");
+
+  it.runIf(process.platform !== "win32")(
+    "self-heals a group/other-readable secret to 0600 and still reads it",
+    async () => {
+      const token = await ensureExtensionRelayToken();
+      const secretPath = secretFilePath();
+      fs.chmodSync(secretPath, 0o644);
+      // Reading tightens the mode back to private and still returns the token.
+      expect(readExtensionRelayToken()).toBe(token);
+      expect(fs.statSync(secretPath).mode & 0o777).toBe(0o600);
+    },
+  );
+
+  it("refuses a symlinked secret", async () => {
+    const token = await ensureExtensionRelayToken();
+    const secretPath = secretFilePath();
+    const realTarget = path.join(stateDir, "elsewhere.secret");
+    fs.renameSync(secretPath, realTarget);
+    fs.symlinkSync(realTarget, secretPath);
+    expect(token).toMatch(/^[0-9a-f]{64}$/);
+    expect(readExtensionRelayToken()).toBeNull();
+  });
+});
+
+describe("classifyRelaySecretPrivacy", () => {
+  it("accepts a private, self-owned file", () => {
+    expect(classifyRelaySecretPrivacy({ uid: 501, mode: 0o600 }, 501, "linux")).toBe("ok");
+  });
+
+  it("flags a self-owned file with broad mode for healing", () => {
+    expect(classifyRelaySecretPrivacy({ uid: 501, mode: 0o644 }, 501, "linux")).toBe("heal");
+    expect(classifyRelaySecretPrivacy({ uid: 501, mode: 0o660 }, 501, "linux")).toBe("heal");
+  });
+
+  it("refuses a foreign-owned file regardless of mode", () => {
+    expect(classifyRelaySecretPrivacy({ uid: 0, mode: 0o600 }, 501, "linux")).toBe("refuse");
+  });
+
+  it("trusts Windows ACLs and an unknown uid instead of POSIX bits", () => {
+    expect(classifyRelaySecretPrivacy({ uid: 0, mode: 0o777 }, 501, "win32")).toBe("ok");
+    expect(classifyRelaySecretPrivacy({ uid: 0, mode: 0o777 }, undefined, "linux")).toBe("ok");
+  });
 });
diff --git a/extensions/browser/src/browser/extension-relay/relay-auth.ts b/extensions/browser/src/browser/extension-relay/relay-auth.ts
index e44713b17cc0..dfc7a7d7fc46 100644
--- a/extensions/browser/src/browser/extension-relay/relay-auth.ts
+++ b/extensions/browser/src/browser/extension-relay/relay-auth.ts
@@ -8,17 +8,18 @@
  * Chrome, and no gateway credential ever has to travel to a node.
  */
 import crypto from "node:crypto";
+import fs from "node:fs";
 import path from "node:path";
-import {
-  createSecretFileAtomic,
-  readSecretFile,
-  tryReadSecretFileSync,
-} from "openclaw/plugin-sdk/secret-file";
+import { createSecretFileAtomic, tryReadSecretFileSync } from "openclaw/plugin-sdk/secret-file";
 import { resolveOAuthDir } from "openclaw/plugin-sdk/state-paths";
+import { createSubsystemLogger } from "../../logging/subsystem.js";
+
+const log = createSubsystemLogger("browser").child("extension-relay");
 
 const RELAY_SECRET_FILE = "browser-extension-relay.secret";
 const RELAY_SECRET_REREAD_ATTEMPTS = 50;
 const RELAY_SECRET_REREAD_DELAY_MS = 10;
+const PRIVATE_SECRET_FILE_MODE = 0o600;
 
 // resolveOAuthDir returns `${stateDir}/credentials`, the shared credentials dir.
 function resolveExtensionRelaySecretPath(env: NodeJS.ProcessEnv = process.env): string {
@@ -30,12 +31,79 @@ function normalizeToken(raw: string): string | null {
   return /^[0-9a-f]{64}$/.test(value) ? value : null;
 }
 
+/**
+ * The relay secret is the whole auth model: anyone who can read it drives the
+ * user's real browser, and loopback is not a trust boundary on a multi-user
+ * host. The fs-safe reader rejects symlinks/hardlinks but does not re-check the
+ * file mode or owner on read, so a secret whose permissions drifted
+ * group/other-readable (loosened umask, restore, shared home) would still be
+ * trusted. Classify the file's privacy before use.
+ */
+export type RelaySecretPrivacy = "ok" | "heal" | "refuse";
+
+/**
+ * Pure privacy decision for a secret file's stat. `heal`: we own it but the
+ * mode is too broad — tighten to 0600 and continue. `refuse`: owned by another
+ * user (never trust a foreign-owned credential). Windows uses ACLs, not POSIX
+ * mode bits, and the create path establishes them, so it is always `ok` here.
+ */
+export function classifyRelaySecretPrivacy(
+  stat: { uid: number; mode: number },
+  selfUid: number | undefined,
+  platform: NodeJS.Platform = process.platform,
+): RelaySecretPrivacy {
+  if (platform === "win32" || selfUid === undefined) {
+    return "ok";
+  }
+  if (stat.uid !== selfUid) {
+    return "refuse";
+  }
+  return (stat.mode & 0o077) === 0 ? "ok" : "heal";
+}
+
+/**
+ * Return the secret path only when it is safe to read: absent (caller handles
+ * null), already private, or self-healable by tightening our own file's mode.
+ * Refuses a foreign-owned or unhealable file so a world-readable credential is
+ * never trusted.
+ */
+function resolveUsableRelaySecretPath(env: NodeJS.ProcessEnv): string | null {
+  const secretPath = resolveExtensionRelaySecretPath(env);
+  let stat: fs.Stats;
+  try {
+    stat = fs.lstatSync(secretPath);
+  } catch (err) {
+    // Absent is the normal "not paired yet" case; let the reader return null.
+    return (err as NodeJS.ErrnoException).code === "ENOENT" ? secretPath : null;
+  }
+  if (stat.isSymbolicLink() || !stat.isFile()) {
+    log.warn("ignoring extension relay secret: not a regular file");
+    return null;
+  }
+  const decision = classifyRelaySecretPrivacy(stat, process.getuid?.());
+  if (decision === "refuse") {
+    log.warn("ignoring extension relay secret: owned by another user");
+    return null;
+  }
+  if (decision === "heal") {
+    try {
+      fs.chmodSync(secretPath, PRIVATE_SECRET_FILE_MODE);
+      log.warn("tightened extension relay secret permissions to 0600");
+    } catch {
+      log.warn("ignoring extension relay secret: permissions are too broad and could not be fixed");
+      return null;
+    }
+  }
+  return secretPath;
+}
+
 /** Read the host-local relay token, or null when it has not been created yet. */
 export function readExtensionRelayToken(env: NodeJS.ProcessEnv = process.env): string | null {
-  return normalizeToken(
-    tryReadSecretFileSync(resolveExtensionRelaySecretPath(env), "browser extension relay secret") ??
-      "",
-  );
+  const secretPath = resolveUsableRelaySecretPath(env);
+  if (!secretPath) {
+    return null;
+  }
+  return normalizeToken(tryReadSecretFileSync(secretPath, "browser extension relay secret") ?? "");
 }
 
 /**
@@ -71,16 +139,11 @@ export async function ensureExtensionRelayToken(
     }
     // Another process created it first; its exclusive async write may still be
     // finishing after the final name appears, so adopt it with a bounded reread.
+    // Reuse the hardened sync read so a foreign-owned file is never adopted here.
     for (let attempt = 0; attempt < RELAY_SECRET_REREAD_ATTEMPTS; attempt += 1) {
-      try {
-        const winner = normalizeToken(
-          await readSecretFile(secretPath, "browser extension relay secret"),
-        );
-        if (winner) {
-          return winner;
-        }
-      } catch {
-        // Retry only inside the bounded first-writer handoff window.
+      const winner = readExtensionRelayToken(env);
+      if (winner) {
+        return winner;
       }
       await new Promise<void>((resolve) => {
         setTimeout(resolve, RELAY_SECRET_REREAD_DELAY_MS);