Configure Codex CLI Model Provider

Codex CLI stores the model and provider in config.toml and the API key separately in auth.json. Both files live in the current system user's .codex directory.

Step 1: Choose a model

Open LAYSO AI models and pricing ↗, compare price, context length, and capabilities, then copy the exact model ID shown on the page.

The example below uses gpt-5.5. To switch models later, change only model.

Step 2: Add the model provider

Locate the current user's configuration file for your operating system:

System	config.toml path
macOS	/Users/<username>/.codex/config.toml
Windows	C:\Users\<username>\.codex\config.toml
Linux / WSL	/home/<username>/.codex/config.toml

Open the file and add:

model_provider = "layso_ai"
model = "gpt-5.5"
model_reasoning_effort = "high"
disable_response_storage = true
cli_auth_credentials_store = "file"

[model_providers.layso_ai]
name = "LAYSO AI"
base_url = "https://api.layso.ai/v1"
wire_api = "responses"
requires_openai_auth = true

Field	Purpose
model_provider	Uses the LAYSO AI provider ID: layso_ai
name	Provider name displayed in Codex: LAYSO AI
model	Exact model ID copied from the pricing page
model_reasoning_effort	Reasoning effort; this example uses high
disable_response_storage	Disables Responses API response storage
cli_auth_credentials_store	Forces credentials to use .codex/auth.json for the current user
base_url	LAYSO AI OpenAI-compatible Base URL
wire_api	Responses request format used by a Codex custom provider
requires_openai_auth	Uses OPENAI_API_KEY from the Codex authentication file

Step 3: Write the API key to the authentication file

Create and copy a key from the LAYSO AI API Keys page ↗. Do not place the key in config.toml; create auth.json for your device.

The authentication file uses the same content on all three systems:

{
  "OPENAI_API_KEY": "sk-..."
}

Replace sk-... with the full LAYSO AI API key.

macOS

Authentication file: /Users/<username>/.codex/auth.json (the same as ~/.codex/auth.json).

mkdir -p ~/.codex
nano ~/.codex/auth.json
chmod 600 ~/.codex/auth.json

Paste the JSON above into the editor, save, and exit.

Windows

Authentication file: C:\Users\<username>\.codex\auth.json ($HOME\.codex\auth.json in PowerShell).

New-Item -ItemType Directory -Force "$HOME\.codex"
notepad "$HOME\.codex\auth.json"

Paste the JSON above into Notepad. When saving, make sure the file is named auth.json, not auth.json.txt.

Linux / WSL

Authentication file: /home/<username>/.codex/auth.json (the same as ~/.codex/auth.json).

mkdir -p ~/.codex
nano ~/.codex/auth.json
chmod 600 ~/.codex/auth.json

Paste the JSON above into the editor, save, and exit. WSL uses the Linux home directory, not the Windows user directory.

auth.json stores only the API key; config.toml stores the model and provider. Never share, screenshot, or commit authentication data from these files.

Step 4: Start and verify

codex

Run /status inside Codex and confirm that the provider is LAYSO AI and the model ID matches your pricing-page selection.

Switch models

Return to LAYSO AI models and pricing ↗, copy another exact model ID, and update:

model = "<MODEL_ID>"

Restart Codex after saving. One LAYSO AI API key can access platform models. Successful requests have itemized charges; failed tasks are not charged.

Authentication troubleshooting

Symptom	Resolution
401 / 403	Confirm that .codex/auth.json exists for the current user, contains valid JSON, and has a valid OPENAI_API_KEY
404	Keep base_url = "https://api.layso.ai/v1"; do not append /v1 twice
Invalid request shape	Confirm wire_api = "responses"
Unknown model	Copy the exact ID from the pricing page
Provider not applied	Confirm model_provider = "layso_ai" and [model_providers.layso_ai], then restart Codex
Old key is still used	Confirm cli_auth_credentials_store = "file", fully quit Codex, and restart it

Next step

Read Codex Desktop or return to the Codex CLI overview.