Codex

1. Overview

Codex is OpenAI’s official terminal-based coding agent, designed for code generation, code review and complex engineering tasks. With GravitexAI (OpenAI-compatible) you can:

Unified access

Use one API key to reach GPT-5.5 / 5.4 / 5.4-Pro and the whole GPT family

Responses API

Built-in wire_api = "responses" for the latest GPT models

High availability

Distributed infra with automatic failover and stable global routing

Pay-as-you-go

No subscriptions, token-based billing — better value than the official endpoint

2. Prerequisites

Codex CLI installed (follow Codex’s official install instructions)
An API key created in the GravitexAI console (format sk-xxxxxxxxxx)

Base URL: https://api.gravitex.ai/v1 — must end with /v1.

3. Quick Setup

Codex uses a TOML config to declare providers. Env vars can be unreliable for custom providers, so we recommend writing the config directly into TOML.

Edit `~/.codex/config.toml`

Open the config

# macOS / Linux
nano ~/.codex/config.toml

# Windows
notepad %USERPROFILE%\.codex\config.toml

Paste the following

model = "gpt-5.5"
model_provider = "openai-custom"
personality = "pragmatic"
model_reasoning_effort = "high"

[model_providers.openai-custom]
name = "GravitexAI"
base_url = "https://api.gravitex.ai/v1"
wire_api = "responses"

# Custom providers usually need the key injected explicitly:
[model_providers.openai-custom.http_headers]
Authorization = "Bearer YOUR_API_KEY"
Content-Type = "application/json"

Launch Codex

cd your-project-folder
codex

Codex will use the GPT model served by GravitexAI based on this config.

4. Recommended Models (via GravitexAI)

Codex currently supports GPT-family model IDs. The most commonly used combinations on GravitexAI:

Model ID	Best for	Notes
gpt-5.5 ⭐	Complex reasoning, production code	OpenAI’s latest flagship
gpt-5.4	General chat, codegen	Next-gen main model for pro tasks
gpt-5.4-pro	Heavy refactoring / reasoning	High-performance variant
gpt-5.4-mini	Balanced cost & speed	General daily dev
gpt-5.4-nano	High concurrency / low cost	Lightweight workloads
gpt-5.1-codex	Code-focused completion	Requires `wire_api = "responses"`

Codex supports GPT-family IDs only (e.g. gpt-5.5, gpt-5.4, gpt-5.1-codex). See the full list in the GravitexAI model catalog.

5. Personality & Reasoning

Codex exposes two optional settings to customize behavior: personality and model_reasoning_effort.

5.1 Personality

Controls the tone and style of replies.

personality = "pragmatic"

Option	Description
`pragmatic`	Direct and practical, minimal explanation
`concise`	Short and to the point
`detailed`	More context and explanation
`analytical`	Structured, logic-focused
`creative`	Expressive and flexible

Personality is a soft preference, not strictly enforced. For precise control, use a system prompt.

5.2 Reasoning effort

Controls how much “thinking” the model spends — maps to the reasoning.effort field of OpenAI’s Responses API.

model_reasoning_effort = "high"

Option	Description	Best for
`low`	Fastest responses	Quick Q&A, copy generation
`medium`	Balanced speed/quality	Day-to-day coding
`high`	Deep reasoning	Complex debugging, design, algorithms

Higher reasoning effort costs more time and tokens but markedly improves quality for hard coding and debugging tasks.

5.3 Full example

model = "gpt-5.5"
model_provider = "openai-custom"
personality = "pragmatic"
model_reasoning_effort = "high"

[model_providers.openai-custom]
name = "GravitexAI"
base_url = "https://api.gravitex.ai/v1"
wire_api = "responses"

[model_providers.openai-custom.http_headers]
Authorization = "Bearer sk-your-gravitex-key"
Content-Type = "application/json"

This config gives you:

Clear, practical answers
Deep reasoning for complex tasks
Full GPT-5.5 capability via the Responses API

6. FAQ

401 / invalid API key

Re-check your key in the GravitexAI console — beware of stray spaces or newlines.
Confirm the Authorization header is Bearer sk-xxxxxxxxxx.
Make sure your balance is positive.

404 / wrong endpoint

Make sure the Base URL ends with /v1:

base_url = "https://api.gravitex.ai/v1"

Common mistakes: missing /v1, appending /responses, using http:// instead of https://.

Model not found

Verify the model ID exists in the GravitexAI model list.
Codex supports GPT-family IDs only (no Claude / Gemini).
Model names are case-sensitive.

chatCompletion error with gpt-5.1-codex

gpt-5.1-codex / gpt-5.2-codex and similar Codex models only support the Responses API. Make sure your provider config has:

[model_providers.openai-custom]
wire_api = "responses"

Env vars don't seem to work?

For custom providers, Codex may not auto-inject OPENAI_API_KEY. Recommended: set Authorization explicitly via http_headers:

[model_providers.openai-custom.http_headers]
Authorization = "Bearer sk-your-key"

7. References

GravitexAI console: https://maas.gravitex.ai
Model catalog: https://maas.gravitex.ai/#/models
API keys: https://maas.gravitex.ai/#/keys
OpenAI Responses API: https://platform.openai.com/docs/api-reference/responses

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1. Overview

Unified access

Responses API

High availability

Pay-as-you-go

2. Prerequisites

3. Quick Setup

Edit `~/.codex/config.toml`

4. Recommended Models (via GravitexAI)

5. Personality & Reasoning

5.1 Personality

5.2 Reasoning effort

5.3 Full example

6. FAQ

7. References

​1. Overview

Unified access

Responses API

High availability

Pay-as-you-go

​2. Prerequisites

​3. Quick Setup

​Edit ~/.codex/config.toml

​4. Recommended Models (via GravitexAI)

​5. Personality & Reasoning

​5.1 Personality

​5.2 Reasoning effort

​5.3 Full example

​6. FAQ

​7. References

1. Overview

2. Prerequisites

3. Quick Setup

Edit `~/.codex/config.toml`

4. Recommended Models (via GravitexAI)

5. Personality & Reasoning

5.1 Personality

5.2 Reasoning effort

5.3 Full example

6. FAQ

7. References