Codex CLI (Mac/Linux)

After installing the Codex CLI, create two config files by hand (config.toml + auth.json) to connect to the LMU AI API — no third-party config tool needed.

Step 1 — Install Node.js

You need Node.js 20+ — download: https://nodejs.org/en/download

Click through the installer, then verify in the terminal:

node --version
# A version number (e.g. v23.7.0) means it installed correctly

Step 2 — Install the Codex CLI

npm i -g @openai/codex

If you hit network issues, switch to a China mirror first:

npm config set registry https://registry.npmmirror.com
npm i -g @openai/codex

Verify the install:

codex --version
# A version number means it installed correctly

Step 3 — Create the config files

The config directory is ~/.codex/ (create it if missing; overwrite any old files). Create/overwrite these two files in it:

config.toml

model = "gpt-5.4"
model_reasoning_effort = "xhigh"
disable_response_storage = true
sandbox_mode = "danger-full-access"
windows_wsl_setup_acknowledged = true
approval_policy = "never"
file_opener = "vscode"
model_provider = "codex"
web_search = "cached"
suppress_unstable_features_warning = true

[history]
persistence = "save-all"

[tui]
notifications = true

[shell_environment_policy]
inherit = "all"
ignore_default_excludes = false

[sandbox_workspace_write]
network_access = true

[features]
plan_tool = true
apply_patch_freeform = true
view_image_tool = true
unified_exec = false
streamable_shell = false
rmcp_client = true
elevated_windows_sandbox = true

[profiles.auto-max]
approval_policy = "never"
sandbox_mode = "workspace-write"

[profiles.review]
approval_policy = "on-request"
sandbox_mode = "workspace-write"

[notice]
hide_gpt5_1_migration_prompt = true

[model_providers.codex]
name = "codex"
base_url = "https://api.lmuai.com"
wire_api = "responses"
requires_openai_auth = true

auth.json

{
  "OPENAI_API_KEY": "your sk- key generated in the console"
}

Step 4 — Launch the Codex CLI

After saving the config files, reopen the terminal and run the following to launch and sign in automatically:

codex --dangerously-bypass-approvals-and-sandbox

Or the short form:

codex --yolo

This launch command skips security approvals, so you do not approve each auto-executed step.

On a successful launch, the interface shows the current model as gpt-5.4 xhigh (the model set by the model field in config.toml).

Enabling the 1M context in Codex (optional)

gpt-5.4 supports a 1M-token long context window (272K by default), useful for large-repo review, long-log analysis, and cross-file refactors. Codex does not enable the 1M window by default; you must declare it explicitly in config.toml.

How to configure: add two lines to config.toml

Edit ~/.codex/config.toml and add the following at the top level (before any [section], e.g. right after model = "gpt-5.4"):

model_context_window = 1000000
model_auto_compact_token_limit = 900000

Save, reopen the terminal, and re-enter Codex to apply it.

Field reference

Verify it took effect

After re-entering Codex, type /status and check whether context window shows around 1M (some versions show about 950K — a reserved 5% safety margin from Codex). You can also use /statusline to add context usage to the status bar for live monitoring.

If you use CC Switch

If you manage the Codex config with CC Switch, add the same two lines in its Codex config editor and apply — the effect is identical:

Last updated: 2026-08-26