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Codex Issues / #29396

Invalid transport error when setting `mcp_servers.codex_apps.startup_timeout_sec`

Open 💬 6 comments Opened Jun 22, 2026 by siddhpant

When starting Codex (v0.141.0), I got the following error:

⚠ MCP client for `codex_apps` timed out after 30 seconds. Add or adjust `startup_timeout_sec` in your config.toml:
  [mcp_servers.codex_apps]
  startup_timeout_sec = XX

⚠ MCP startup incomplete (failed: codex_apps)

So I did that and added the following in config.toml:

[mcp_servers.codex_apps]
startup_timeout_sec = 60

After that codex fails to start:

$ codex
Error loading config.toml: invalid transport
in `mcp_servers.codex_apps`

View original on GitHub ↗

6 Comments

noneNote · 21 days ago

I also encountered a similar error. I am using Codex within the Microsoft Ubuntu WSL environment; this issue began appearing after I updated from version 0.137 to 0.142.

xiaoying706 · 21 days ago

我也遇到这个问题了,还以为是我电脑的自身问题呢,看到你们的问题,这下我总算放心了

EazyReal · 11 days ago

Still reproducible on codex-cli 0.144.1 with Linux x86_64, ChatGPT Pro/Max auth, and tmux 3.4.

I reproduced the full sequence today:

  1. Launch Codex with apps enabled and a populated ~/.codex/cache/codex_apps_tools cache.
  2. gpt-5.6-sol responds successfully, but codex_apps remains in Booting MCP server state.
  3. At 30 seconds the TUI prints the timeout and recommends:
[mcp_servers.codex_apps]
startup_timeout_sec = 60
  1. Adding that exact table makes Codex fail before startup with:
Error loading config.toml: invalid transport in `mcp_servers.codex_apps`

The current source constructs this host-owned server with a fixed 30-second timeout:
https://github.com/openai/codex/blob/main/codex-rs/codex-mcp/src/mcp/mod.rs#L539-L553

This appears to be the generic MCP timeout remediation being shown for a host-owned server whose user configuration cannot be expressed as a transport-less mcp_servers entry. A fix could either expose a valid dedicated timeout setting, merge a user timeout override into the synthesized server, or suppress the unusable suggestion for codex_apps.

codex doctor --json returned no output on this build.

skorotkiewicz · 10 days ago

I have exactly the same issue as @EazyReal

sharkxuanbee · 5 days ago

Confirmed on codex-cli 0.144.4, native Ubuntu 26.04 x86_64.

The TUI warning still recommends configuring the implicit server:

Add or adjust startup_timeout_sec in your config.toml:
[mcp_servers.codex_apps]
startup_timeout_sec = XX

However, the suggested override is not representable because codex_apps has no user-configurable transport:

$ codex mcp list
No MCP servers configured yet.

$ codex mcp get codex_apps
Error: No MCP server named 'codex_apps' found.

$ codex -c mcp_servers.codex_apps.startup_timeout_sec=90 --no-alt-screen
Error loading config.toml: invalid transport
in `mcp_servers.codex_apps`

A full Codex/app-server restart does not change this deterministic config failure.

Expected behavior: for a host-owned implicit MCP, either expose a dedicated supported timeout setting or suppress the generic user-MCP suggestion. Ideally the warning should also preserve the actual upstream Apps/Connectors error instead of only reporting a tools/list timeout.

siddhpant · 5 days ago

Can we just say +1 instead of AI dumping itself here?