What to know first
Start with Codex if you want the OpenAI and ChatGPT ecosystem. Consider Claude Code if your work is centered on terminal, IDE, desktop, and web surfaces in the Claude ecosystem. Consider Antigravity if you want an agent-first workspace that can switch among Google and partner models. Model availability and limits change, so verify the official pages before buying.
Choose the workflow before the brand
Codex is OpenAI's coding agent for coding, tests, fixes, and delivery across ChatGPT plans, the CLI, desktop, and developer tools. Claude Code is an agentic coding tool that understands a codebase, edits files, runs commands, and works in the terminal, IDE, desktop, and web. Antigravity places App, CLI, and IDE surfaces in an agent-first workspace and lets users switch among Google DeepMind and partner models.
All three can write code, but the outcome also depends on repository permissions, terminal sandboxing, network policy, context handling, approvals, and team policy. Do not choose a long-term tool from one first-turn code sample.
| Tool | Main surfaces | Work to validate first |
|---|---|---|
| Codex | ChatGPT, CLI, desktop, developer tools | Fixes, refactors, tests, and cross-file delivery |
| Claude Code | Terminal, IDE, desktop, web | Long tasks, codebase understanding, commands, and PR work |
| Gemini Antigravity | App, CLI, IDE | Multi-model agent workflows, task groups, and reviewable artifacts |
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Claude Code overviewGoogle Antigravity: Choose a model
Billing determines the long-term cost
Codex can use allowances from a ChatGPT plan. When signed in with a ChatGPT account, usage depends on the plan, model, task complexity, context, and tools. In supported situations, an API key can use the API pricing model instead.
Claude Code metering depends on how you sign in: a subscription or organization seat uses its included limits, while a Console, Bedrock, Vertex, or other API key bills the corresponding account by tokens. Antigravity offers an individual free tier, Google AI Pro, Google AI Ultra, and organization options with different limits or AI credit pools.
| Question | Codex | Claude Code | Antigravity |
|---|---|---|---|
| Can a fixed plan get started? | Start with a ChatGPT plan | Start with a Claude plan or organization seat | Start with the individual free tier |
| API billing path | API rates when using an API key | Token billing through Console or a cloud provider | Consumption billing for organization/API paths |
| What happens at the limit? | Reset, credits, or upgrade options depend on the account | Limit, credits, or usage billing depends on sign-in | Limits and AI credits depend on the plan |
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Models, usage, and limits in Claude CodeGoogle Antigravity: Pricing
Combine model choice with context and controls
Codex is often strongest when you want OpenAI coding models, code review, and ChatGPT workflow integration. Claude Code fits sustained codebase understanding, terminal operations, and multi-file edits. Antigravity's differentiator is switching among Google and partner reasoning models and selecting a thinking level.
Do not treat a model list as a permanent promise. Antigravity documents plan availability and removal dates, and Codex and Claude Code also change model and allowance rules. Measure task success, human rework, context length, and cost per completed task.
- Short edits and completion: compare latency, IDE integration, and daily limits.
- Large refactors: compare context, planning, test execution, and failure recovery.
- Team workflows: compare permissions, auditability, data policy, pull requests, and caps.
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Claude Code overviewGoogle Antigravity: Choose a model
Three practical starting points
If you already use ChatGPT and want to see Codex usage in the same account, test Codex first. If your daily work is centered on a terminal and IDE and you want to continue similar coding tasks across surfaces, test Claude Code.
If your team wants multiple model providers, agent task groups, and reviewable artifacts, include Antigravity in a controlled pilot. For all three, fix a set of real repository tasks instead of comparing only demo prompts.
| Priority | Test first | Measure |
|---|---|---|
| Already have ChatGPT and want a quick start | Codex | Completion, allowance use, PR rework |
| Terminal and IDE are the main surfaces | Claude Code | Codebase understanding, command safety, session limits |
| Want Google and partner models | Gemini Antigravity | Model availability, limits, artifact review |
| Need centralized governance | Pilot all three | Data policy, permissions, logs, unit task cost |
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Claude Code overviewGoogle Antigravity: Pricing
Run the same tasks for seven days
- Prepare a small fix, a cross-file refactor, a test-completion task, and a pull-request review.
- Keep the repository, instructions, test commands, and acceptance criteria the same.
- Record completion time, human edits, retries, tokens or credits, and final bill.
- Evaluate dangerous commands, network access, secret protection, and approval UX separately.
- Choose the long-term plan from unit task cost and acceptable risk.
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Models, usage, and limits in Claude CodeGoogle Antigravity: Choose a model
Frequently asked questions
Which tool writes code best?
There is no task-independent winner. Codex fits the OpenAI/ChatGPT workflow, Claude Code fits terminal and codebase-agent work, and Antigravity fits a multi-model agent workspace. Use the same real tasks to compare.
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Claude Code overviewGoogle Antigravity: Choose a model
Which one is cheapest?
Do not compare monthly prices alone. Compare included usage, overage credits, API rates, completion rate, and human rework; plans and limits change.
Sources: OpenAI: Using Codex with your ChatGPT planAnthropic: Models, usage, and limits in Claude CodeGoogle Antigravity: Pricing
Is Claude Code an API or subscription product?
It can be used both ways. A subscription or organization seat uses its included allowance, while an API key, Console, or cloud credential bills the relevant account by tokens.
Sources: Anthropic: Models, usage, and limits in Claude CodeAnthropic: Claude Code overview
Does Antigravity only use Gemini?
Its official documentation describes access to Google DeepMind and partner models. Exact availability depends on the plan, surface, and account.
Sources: Google Antigravity: Choose a model
Do I need to buy a separate API for Codex?
With a ChatGPT account, Codex usage follows the plan and account rules. Calls made with an API key or inside your own application use the separate API billing model.
Sources: OpenAI: Using Codex with your ChatGPT planOpenAI: Managing billing for ChatGPT and the API platform
Official sources and review notes
Sources checked on October 17, 2026. Rates and eligibility rules can change; confirm the latest official guidance and your own agreement.
- OpenAI: Using Codex with your ChatGPT plan
- Anthropic: Claude Code overview
- Anthropic: Models, usage, and limits in Claude Code
- Google Antigravity: Pricing
- Google Antigravity: Choose a model
- OpenAI: Managing billing for ChatGPT and the API platform
AISub prepared this guide from public OpenAI documentation, with an independent worked example and purchasing advice. AISub is an independent price index and is not affiliated with OpenAI.