diff --git a/agent/src/service/install.ts b/agent/src/service/install.ts
index adae58e..8563098 100644
--- a/agent/src/service/install.ts
+++ b/agent/src/service/install.ts
@@ -11,7 +11,7 @@
  *   - FIX M-host-2service: base-app env (BIND_HOST/ALLOWED_ORIGINS/PORT/…) is routed to the
  *     base-app unit ONLY; the agent unit (which supervises frpc) never carries it.
  */
-import { dirname } from 'node:path'
+import { dirname, join } from 'node:path'
 import type { AgentConfig } from '../config/agentConfig.js'
 import {
   agentLabel,
@@ -225,9 +225,15 @@ export async function installService(
 
   if (platform === 'launchd') {
     const baseAppPath = launchdPlistPath(deps.homedir(), baseAppLabel())
-    deps.writeFile(baseAppPath, buildLaunchdPlist(baseAppExec, baseAppEnvWithPath, baseAppLabel()))
+    deps.writeFile(
+      baseAppPath,
+      buildLaunchdPlist(baseAppExec, baseAppEnvWithPath, baseAppLabel(), join(cfg.stateDir, 'base-app.log')),
+    )
     const agentPath = launchdPlistPath(deps.homedir(), agentLabel())
-    deps.writeFile(agentPath, buildLaunchdPlist([nodePath, bin, 'run'], agentEnv, agentLabel()))
+    deps.writeFile(
+      agentPath,
+      buildLaunchdPlist([nodePath, bin, 'run'], agentEnv, agentLabel(), join(cfg.stateDir, 'agent.log')),
+    )
     for (const path of [baseAppPath, agentPath]) {
       const { cmd, args } = launchdLoadCommand(path)
       await deps.runCommand(cmd, args)
diff --git a/agent/src/service/launchd.ts b/agent/src/service/launchd.ts
index b4d1e76..772ca4b 100644
--- a/agent/src/service/launchd.ts
+++ b/agent/src/service/launchd.ts
@@ -78,6 +78,7 @@ export function buildLaunchdPlist(
   programArguments: readonly string[],
   env: ServiceEnv = {},
   label: string = AGENT_LABEL,
+  logPath?: string,
 ): string {
   return [
     '<?xml version="1.0" encoding="UTF-8"?>',
@@ -91,6 +92,16 @@ export function buildLaunchdPlist(
     '  <true/>',
     '  <key>KeepAlive</key>',
     '  <true/>',
+    // launchd's default has no log sink (unlike systemd's journald), so a crashing unit is silent.
+    // Route stdout+stderr to a file so `pair --install` failures are diagnosable out of the box.
+    ...(logPath !== undefined
+      ? [
+          '  <key>StandardOutPath</key>',
+          `  <string>${escapeXml(logPath)}</string>`,
+          '  <key>StandardErrorPath</key>',
+          `  <string>${escapeXml(logPath)}</string>`,
+        ]
+      : []),
     ...environmentVariablesBlock(env),
     '</dict>',
     '</plist>',