diff --git a/src/service/launchd.ts b/src/service/launchd.ts
index 0fdf5e3..f477e7b 100644
--- a/src/service/launchd.ts
+++ b/src/service/launchd.ts
@@ -66,7 +66,9 @@ export function buildPlist(): string {
   <dict>
     <key>PATH</key>
     <string>${escapeXml(pathEnv)}</string>
-  </dict>
+${process.env.CODEX_BIN ? `    <key>CODEX_BIN</key>
+    <string>${escapeXml(process.env.CODEX_BIN)}</string>
+` : ''}  </dict>
 </dict>
 </plist>
 `;
diff --git a/src/service/systemd.ts b/src/service/systemd.ts
index 10d8b46..3b26039 100644
--- a/src/service/systemd.ts
+++ b/src/service/systemd.ts
@@ -42,6 +42,7 @@ export function buildUnit(): string {
   const nodePath = process.execPath;
   const cliBinPath = resolveCliBinPath();
   const pathEnv = process.env.PATH ?? '';
+  const codexBinEnv = process.env.CODEX_BIN ? `Environment="CODEX_BIN=${esc(process.env.CODEX_BIN)}"\n` : '';
   return `[Unit]
 Description=feishu-codex-bridge bot
 After=network-online.target
@@ -55,6 +56,7 @@ RestartSec=5
 StandardOutput=append:${serviceStdoutPath()}
 StandardError=append:${serviceStderrPath()}
 Environment="PATH=${esc(pathEnv)}"
+${codexBinEnv}
 
 [Install]
 WantedBy=default.target
diff --git a/src/service/win-startup.ts b/src/service/win-startup.ts
index 23adf5f..721f3e5 100644
--- a/src/service/win-startup.ts
+++ b/src/service/win-startup.ts
@@ -62,6 +62,7 @@ export function buildLauncherCmd(): string {
   return [
     '@echo off',
     `set "PATH=${process.env.PATH ?? ''}"`,
+    ...(process.env.CODEX_BIN ? [`set "CODEX_BIN=${process.env.CODEX_BIN}"`] : []),
     `set "${SERVICE_ENV_FLAG}=1"`,
     `"${process.execPath}" "${resolveCliBinPath()}" run >> "${serviceStdoutPath()}" 2>> "${serviceStderrPath()}"`,
     '',
diff --git a/test/service-definitions.test.ts b/test/service-definitions.test.ts
index cf51f0b..48e1c5c 100644
--- a/test/service-definitions.test.ts
+++ b/test/service-definitions.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect, it } from 'vitest';
+import { buildPlist } from '../src/service/launchd';
 import { buildUnit, SYSTEMD_UNIT_NAME } from '../src/service/systemd';
 import { buildLauncherCmd, buildLauncherVbs } from '../src/service/win-startup';
 
@@ -28,6 +29,22 @@ describe('systemd unit (buildUnit)', () => {
   it('unit name is a .service', () => {
     expect(SYSTEMD_UNIT_NAME).toMatch(/\.service$/);
   });
+
+  it('preserves an explicit CODEX_BIN override for the background service', () => {
+    withCodexBin('/opt/codex/bin/codex', () => {
+      expect(buildUnit()).toContain('Environment="CODEX_BIN=/opt/codex/bin/codex"');
+    });
+  });
+});
+
+describe('launchd plist (buildPlist)', () => {
+  it('preserves an explicit CODEX_BIN override for the background service', () => {
+    withCodexBin('/Applications/Codex & Friends.app/Contents/Resources/codex', () => {
+      const plist = buildPlist();
+      expect(plist).toContain('<key>CODEX_BIN</key>');
+      expect(plist).toContain('/Applications/Codex &amp; Friends.app/Contents/Resources/codex');
+    });
+  });
 });
 
 describe('Windows hidden launcher (.cmd)', () => {
@@ -45,6 +62,12 @@ describe('Windows hidden launcher (.cmd)', () => {
     expect(cmd).toContain('>> "');
     expect(cmd).toContain('2>> "');
   });
+
+  it('preserves an explicit CODEX_BIN override for the background service', () => {
+    withCodexBin('C:\\Tools\\codex.exe', () => {
+      expect(buildLauncherCmd()).toContain('set "CODEX_BIN=C:\\Tools\\codex.exe"');
+    });
+  });
 });
 
 describe('Windows hidden launcher (.vbs)', () => {
@@ -55,3 +78,14 @@ describe('Windows hidden launcher (.vbs)', () => {
     expect(vbs).toMatch(/sh\.Run "cmd \/c "".+\.cmd""", 0, False/);
   });
 });
+
+function withCodexBin(value: string, fn: () => void): void {
+  const prev = process.env.CODEX_BIN;
+  process.env.CODEX_BIN = value;
+  try {
+    fn();
+  } finally {
+    if (prev === undefined) delete process.env.CODEX_BIN;
+    else process.env.CODEX_BIN = prev;
+  }
+}