Codex CLI

Guide to configuring the OpenAI Codex CLI to call the Minimax model via GreenNode MaaS — using the Responses API through a custom maas provider defined in codex.toml.

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Prerequisites

• Prepare your API key, Base URL, and model following Getting Started with AI Coding

• Node.js ≥ 22 installed

The Minimax M2.5 model via Codex uses the OpenAI standard — the Base URL includes /v1: https://maas-llm-aiplatform-hcm.api.vngcloud.vn/v1.

Using a Token Plan (subscription package) key instead of a pay-as-you-go API key? Use https://tokenplan.api.greennode.ai/v1 as the Base URL instead. See Token Plan for details.

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Step 1 — Install Codex CLI

npm install -g @openai/codex

Confirm the install succeeded:

codex --version

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Step 2 — Get an API key from AI Platform

1. Log in to the AI Platform Console

2. Go to API Keys → Create API Key

3. Name the key (5–50 characters, lowercase letters + numbers + hyphens)

4. Copy the API key (vn-...) you just created

A newly created API key starts in pending status. Wait until status = ACTIVE before using it.

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Step 3 — Configure codex.toml

Create or edit ~/.codex/config.toml (system-wide config) or codex.toml at your project root (applies to that project only):

# API key — export before running Codex
# export MAAS_API_KEY="vn-...your-gateway-token..."

model_provider = "maas"
model = "minimax/minimax-m2.5"

# Needed because MAAS doesn't return model metadata — avoids incorrect context truncation
model_context_window = 204800
model_max_output_tokens = 16400

# The MAAS backend is stateless — Codex must resend the full conversation every turn
disable_response_storage = true

[model_providers.maas]
name = "MAAS AI Gateway"

# base_url has NO trailing /responses — Codex appends it automatically (→ .../v1/responses)
base_url = "https://maas-llm-aiplatform-hcm.api.vngcloud.vn/v1"
env_key = "MAAS_API_KEY"
wire_api = "responses"
request_max_retries = 3

Key field explanations:

Field	Purpose
model_provider	The provider key under [model_providers.*]
model	Model ID sent to MaaS
model_context_window	Set manually since MaaS doesn't expose model metadata
disable_response_storage	Required for the stateless backend — resend the full conversation every turn
base_url	MaaS endpoint with /v1 — Codex appends /responses after it
env_key	Name of the environment variable holding the API key
wire_api	Protocol used — responses corresponds to the OpenAI Responses API

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Step 4 — Set the API key and run Codex

Export the API key in your shell:

export MAAS_API_KEY="vn-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

To do this automatically every time you open a terminal, add it to ~/.zshrc or ~/.bashrc:

echo 'export MAAS_API_KEY="vn-xxxx..."' >> ~/.zshrc
source ~/.zshrc

Run Codex inside your project directory:

codex

Codex will show the provider and model in use in the session header:

model:     minimax/minimax-m2.5   /model to change
directory: ~/your-project

Codex running with the minimax/minimax-m2.5 model via GreenNode MaaS

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Troubleshooting

Symptom	Cause	Fix
401 Unauthorized	Wrong, missing, or not-yet-ACTIVE API key	Re-export MAAS_API_KEY; check the key's status in the AI Platform Console
404 when sending a request	base_url wrong or missing /v1	Make sure base_url ends with /v1 (no /responses)
Context truncated incorrectly	Model metadata not declared	Check model_context_window and model_max_output_tokens in the config
Loses context every turn	disable_response_storage not set	Add disable_response_storage = true to the config
Connection timeout	Endpoint unreachable	Check VPN / connection to *.api.vngcloud.vn

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Result

Once done, the Codex CLI routes all requests through GreenNode MaaS using the Minimax model. Usage is logged on the AI Platform Console → Usage.

I want to next...	Go to
Use the GUI version	Codex Desktop
Use OpenCode with MaaS	Use OpenCode with GreenNode MaaS
Connect Claude Code to MaaS	Connect Claude Code to GreenNode MaaS
View usage and billing	AI Platform Console

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Need help?

If you've followed the steps and it's still not working, feel free to contact GreenNode Customer Support:

• Email: [e-mail]

• Hotline: [phone]

• Help center: helpdesk.greennode.ai

Thank you for using GreenNode's services.