/agent command takes extremely long to switch back to the main agent

Start by reproducing the regression with /agent and session resume in Codex CLI 0.145.0 using the uploaded thread 019f6908-95ff-73d2-92c5-ba698e0e9bec, then compare behavior with 0.144.6. Focus on the long-session path and the difference between switching to a subagent and switching back to the main agent. Done means agent switching completes within 2 seconds and session resume within 15 seconds, or provides progress for longer operations.

What version of Codex CLI is running?

codex-cli 0.145.0

What subscription do you have?

Pro 20x

Which model were you using?

gpt-5.6-luna

What platform is your computer?

Linux 6.18.33.2-microsoft-standard-WSL2 x86_64 x86_64

What terminal emulator and version are you using (if applicable)?

Windows Terminal

Codex doctor report

{
  "schemaVersion": 1,
  "generatedAt": "1784733292s since unix epoch",
  "overallStatus": "warning",
  "codexVersion": "0.145.0",
  "checks": {
    "app_server.status": {
      "id": "app_server.status",
      "category": "app-server",
      "status": "ok",
      "summary": "background server is not running",
      "details": {
        "control socket": "/home/gili/cat/.codex/app-server-control/app-server-control.sock",
        "daemon state dir": "/home/gili/cat/.codex/app-server-daemon",
        "mode": "ephemeral",
        "pid file": "/home/gili/cat/.codex/app-server-daemon/app-server.pid (missing)",
        "settings": "/home/gili/cat/.codex/app-server-daemon/settings.json (missing)",
        "status": "not running",
        "update-loop pid file": "/home/gili/cat/.codex/app-server-daemon/app-server-updater.pid (missing)"
      },
      "remediation": null,
      "durationMs": 0
    },
    "auth.credentials": {
… +301 lines (ctrl + t to view transcript)
        "terminal title project value": "2.1-add-divide-and-co...",
        "terminal title source": "default"
      },
      "remediation": null,
      "durationMs": 0
    },
    "updates.status": {
      "id": "updates.status",
      "category": "updates",
      "status": "ok",
      "summary": "update configuration is locally consistent",
      "details": {
        "cached latest version": "0.145.0",
        "check for update on startup": "true",
        "last checked at": "2026-07-22T14:22:04.036380264Z",
        "latest version": "0.145.0",
        "latest version status": "current version is not older",
        "update action": "manual or unknown",
        "version cache": "/home/gili/cat/.codex/version.json"
      },
      "remediation": null,
      "durationMs": 262
    }
  }
}

What issue are you seeing?

I am seeing a major performance regression when switching agents or resuming sessions in version 0.145.0 compared to 0.144.6.

In version 0.144.6, switching agents using /agent was almost instantaneous. Resuming the session took ~15-30 seconds, not 8 minutes.
In version 0.145.0 resuming the session or using /agent to switch from a subagent back to the main agent takes 8 minutes to complete with little to no visible CPU, disk or network usage.

Switching from the main agent to a subagent remains fast.

What steps can reproduce the bug?

Uploaded thread: 019f6908-95ff-73d2-92c5-ba698e0e9bec

What is the expected behavior?

• Switching between agents using /agent should take no longer than 2 seconds
• Resuming sessions should take no longer than 15 seconds. Consider showing a progress indicator for long operations.

Additional information

This is a long session, spanning continuous work over ~2-3 days of work.