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codex - 💡(How to fix) Fix codex takes ~5 seconds before entering the TUI [1 comments, 2 participants]

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openai/codex#19802•Fetched 2026-04-28 06:36:52
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Root Cause

The codex found the cause by itself:

  • The delay happens before the first Codex log line is written to ~/.codex/log/codex-tui.log.
  • codex --disable plugins -c check_for_update_on_startup=false does not help
  • CODEX_TUI_DISABLE_KEYBOARD_ENHANCEMENT=1 codex does not help
  • sample cmd shows the main thread spending most samples in macOS hostname resolution
    • DNS capture shows repeated mDNS queries for the local hostname
      • A/AAAA <local-hostname>.local. via 224.0.0.251:5353 / ff02::fb:5353

Fix Action

Workaround

Adding the local hostname to /etc/hosts fixes the startup delay:

127.0.0.1 <local-hostname>.local
::1       <local-hostname>.local

After flushing DNS cache and restarting mDNSResponder, codex starts normally again:

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

Code Example

127.0.0.1 <local-hostname>.local
::1       <local-hostname>.local

---

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder
RAW_BUFFERClick to expand / collapse

What version of Codex CLI is running?

codex-cli 0.125.0

What subscription do you have?

not related

Which model were you using?

not related

What platform is your computer?

Darwin 25.3.0 arm64 arm

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

Alacritty

What issue are you seeing?

After upgrading codex, launching codex takes ~5 seconds before entering the TUI. Before the upgrade there's no delay.

What steps can reproduce the bug?

Upgrading codex and launching it.

What is the expected behavior?

No delay on launching codex.

Additional information

Cause

The codex found the cause by itself:

  • The delay happens before the first Codex log line is written to ~/.codex/log/codex-tui.log.
  • codex --disable plugins -c check_for_update_on_startup=false does not help
  • CODEX_TUI_DISABLE_KEYBOARD_ENHANCEMENT=1 codex does not help
  • sample cmd shows the main thread spending most samples in macOS hostname resolution
    • DNS capture shows repeated mDNS queries for the local hostname
      • A/AAAA <local-hostname>.local. via 224.0.0.251:5353 / ff02::fb:5353

Workaround

Adding the local hostname to /etc/hosts fixes the startup delay:

127.0.0.1 <local-hostname>.local
::1       <local-hostname>.local

After flushing DNS cache and restarting mDNSResponder, codex starts normally again:

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

extent analysis

TL;DR

Adding the local hostname to /etc/hosts and flushing the DNS cache may resolve the startup delay issue with Codex CLI.

Guidance

  • The delay is likely caused by repeated mDNS queries for the local hostname, which can be verified by checking the DNS capture and codex-tui.log for related errors.
  • To mitigate the issue, add the local hostname to /etc/hosts with the following entries: 127.0.0.1 <local-hostname>.local and ::1 <local-hostname>.local.
  • After making the changes, flush the DNS cache using sudo dscacheutil -flushcache and restart mDNSResponder with sudo killall -HUP mDNSResponder.
  • Verify that the fix worked by launching Codex CLI and checking for the startup delay.

Example

# Add local hostname to /etc/hosts
echo "127.0.0.1 $(hostname).local" | sudo tee -a /etc/hosts
echo "::1 $(hostname).local" | sudo tee -a /etc/hosts

# Flush DNS cache and restart mDNSResponder
sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

Notes

This workaround may not be applicable if the issue is caused by a different factor, and further investigation may be necessary to determine the root cause.

Recommendation

Apply the workaround by adding the local hostname to /etc/hosts and flushing the DNS cache, as it has been reported to resolve the startup delay issue.

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codex - 💡(How to fix) Fix codex takes ~5 seconds before entering the TUI [1 comments, 2 participants]