Codex in-app Browser blocks http://127.0.0.1:3000 despite local server reachable

Resolved 💬 2 comments Opened May 22, 2026 by micronex-13652 Closed May 25, 2026

What version of the Codex App are you using (From “About Codex” dialog)?

26.519.3891.0

What subscription do you have?

ChatGPT Plus

What platform is your computer?

Windows 11 Pro, x64, build 26200

What issue are you seeing?

Feedback ID:
019e4fa5-c24d-7c43-ae5b-e6f9bf1aec88

Problem:
Codex in-app Browser / @Browser rejects http://127.0.0.1:3000 with:

"Browser Use cannot access http://127.0.0.1:3000 because enterprise network policy blocks it."

Local diagnostics:

PowerShell can reach http://127.0.0.1:3000/
HTTP returns 200
Test-NetConnection to 127.0.0.1:3000 succeeds
The local server is running correctly

Affected machine:

Windows 11 Pro x64, build 26200
Codex package: OpenAI.Codex_26.519.3891.0_x64__2p2nqsd0c76g0
Edge WebView2 runtime detected

Firewall / sandbox findings:
Initially these Windows Firewall rules were present and enabled:

codex_sandbox_offline_block_loopback_tcp
codex_sandbox_offline_block_loopback_udp
codex_sandbox_offline_block_outbound

I disabled:

codex_sandbox_offline_block_loopback_tcp
codex_sandbox_offline_block_loopback_udp

After a full Codex restart, both remain Enabled: False, but @Browser still rejects http://127.0.0.1:3000 with the same enterprise network policy block.

Comparison machine:

Same local test URL http://127.0.0.1:3000 returns HTTP 200
codex_sandbox_offline_block_loopback_* rules are not present

Expected:
@Browser should be able to open local development URLs like http://127.0.0.1:3000, or Codex should provide a setting/allowlist to permit localhost access.

Actual:
@Browser rejects the URL before navigation due to enterprise/network policy.

What steps can reproduce the bug?