OpenAI Codex vs Claude Code: Which CLI Coding Agent Should You Use?

Codex CLI and Claude Code are both terminal-based agentic coding tools, but they target different workflows. Codex CLI is a lightweight, open-source agent with full OpenAI-compatible API flexibility and a clean sandbox model. Claude Code is a more feature-complete platform with multi-surface support, richer session management, and tighter integration across CLI, IDE, desktop, and browser. The right choice comes down to whether you need maximum model flexibility or a unified coding environment built around one provider’s API.

What is Codex CLI?

Codex CLI is OpenAI’s open-source terminal coding agent. It runs locally, sends requests to an OpenAI-compatible API backend, and can read files, edit code, and execute commands inside a sandboxed directory on your machine.

The key design choice in Codex CLI is provider flexibility. The tool speaks the OpenAI Chat Completions wire format, which means any provider that exposes an OpenAI-compatible endpoint can be dropped in through a TOML config file. That includes OpenAI’s own models (GPT-4o, o3, o4-mini), but also third-party providers like Novita AI.

Codex CLI’s security model is explicit by design. Network access is disabled by default for executed code, and file writes are scoped to the configured directory. Three approval modes control how much autonomy the agent has:

• Suggest mode (default): prompts for approval at every step
• Auto edit mode: edits files automatically but asks before running commands
• Full auto mode: executes without prompting

The project is MIT-licensed and actively maintained at openai/codex on GitHub.

What is Claude Code?

Claude Code is Anthropic’s agentic coding tool. It is available as a CLI, a VS Code extension, a JetBrains plugin, a desktop app, and a browser interface at claude.ai/code. Every surface runs the same underlying agent engine, which reads your project, edits files, runs commands, and handles multi-step tasks like writing tests, refactoring across files, and managing git.

Under the hood, Claude Code sends requests to an Anthropic-compatible API endpoint. The default is Anthropic’s own api.anthropic.com, but a single environment variable (ANTHROPIC_BASE_URL) redirects it to any compatible provider.

Claude Code adds session continuity features that Codex CLI does not have: named sessions, branch-style conversation forks, rewind checkpoints, and a /compact command that summarizes context to extend the usable window on long tasks. Project-level instructions go into a CLAUDE.md file that the agent reads at the start of every session.

Codex CLI vs Claude Code: Side-by-Side Comparison

Feature	Codex CLI	Claude Code
Provider	OpenAI	Anthropic
License	Open-source (MIT)	Proprietary (API access)
Wire API	OpenAI Chat Completions	Anthropic Messages API
Third-party providers	Any OpenAI-compatible	Any Anthropic-compatible
Surfaces	Terminal only	CLI, VS Code, JetBrains, desktop, browser
Project config	TOML config file	CLAUDE.md + settings.json
Session continuity	Per-session	Named sessions, resume, branch, rewind
Approval modes	Suggest / Auto Edit / Full Auto	default, plan, auto, acceptEdits, bypassPermissions
MCP support	No	Yes
Context management	Per-session context	/compact, /context, /branch
Sandbox security	Network-disabled, directory-scoped	Permission-mode scoping

Model Support and API Flexibility

This is where the two tools differ most sharply in practice.

Codex CLI accepts any model that speaks the OpenAI Chat Completions format. Out of the box it works with OpenAI’s model lineup — GPT-4o, o3, o4-mini — but because the provider is configurable via model_providers in the TOML config, you can point it at Novita AI, Azure OpenAI, or any other compatible endpoint without patching the tool itself.

Claude Code uses the Anthropic Messages API format. By default it routes to Anthropic and uses Claude models (Sonnet, Opus, Haiku). The ANTHROPIC_BASE_URL environment variable allows provider substitution, so any Anthropic-compatible endpoint — including Novita AI — works as a drop-in.

In practice, this means:

• If your preferred models speak the OpenAI format (DeepSeek, Qwen Coder, Kimi K2 via OpenAI-compatible endpoints), Codex CLI is the more natural fit.
• If your preferred models speak the Anthropic format, or you want to use the same configuration across CLI and IDE surfaces, Claude Code gives you more consistent behavior.

Both tools support models from Novita AI. The configuration method differs (TOML for Codex, env var for Claude Code), but the Novita AI model library — including DeepSeek V3, Qwen3-Coder, and Kimi K2 — is accessible through both.

Open-Source vs Proprietary Architecture

Codex CLI’s open-source nature matters in specific contexts: you can audit the agent loop, fork it for internal tooling, or vendor it into a CI pipeline without a separate licensing conversation. The community can (and does) contribute provider integrations, bug fixes, and feature extensions.

Claude Code’s core is proprietary. Anthropic provides the CLI as a distributed binary with API access, not a source release. The upside is a more consistent, well-maintained release cadence with direct Anthropic support. The downside is that customization is limited to what the tool exposes through config files, environment variables, and the extension APIs.

For most developers, the open-source distinction is only relevant if you need to modify the agent’s behavior at a code level. For workflow integration — CI pipelines, automated tasks, scripted code generation — both tools expose enough CLI flags and scripting modes to cover the common cases.

Installation and Setup

Codex CLI installs via npm:

npm install -g @openai/codex

Provider configuration lives in ~/.codex/config.toml:

model = "deepseek/deepseek-v3.1"
model_provider = "novitaai"

[model_providers.novitaai]
name = "Novita AI"
base_url = "https://api.novita.ai/openai"
http_headers = {"Authorization" = "Bearer YOUR_NOVITA_API_KEY"}
wire_api = "chat"

Claude Code installs via the native installer (macOS/Linux/WSL):

curl -fsSL https://claude.ai/install.sh | bash

Or via npm (Node.js 18+):

npm install -g @anthropic-ai/claude-code

Redirecting to a custom provider:

export ANTHROPIC_BASE_URL=https://api.novita.ai/anthropic
export ANTHROPIC_API_KEY=YOUR_NOVITA_API_KEY
claude --model deepseek/deepseek-v3.1

Claude Code also runs /init in a project to generate a starter CLAUDE.md, which persists project-specific instructions across sessions.

Platform and Surface Coverage

This is the most visible difference in day-to-day use.

Codex CLI runs in a terminal. That is its only surface. If your workflow is entirely terminal-based — SSH sessions, headless CI, developer containers — this is fine. If you want inline suggestions inside VS Code or a desktop GUI, Codex CLI does not provide those.

Claude Code runs across five surfaces: the CLI, VS Code extension, JetBrains plugin, desktop app, and claude.ai/code in the browser. All surfaces share the same agent engine and, in most cases, the same session state. A task started in the terminal can be picked up in VS Code.

If IDE integration matters to your team, Claude Code has a clear lead. If you are building a pipeline where the agent runs headless as part of a larger automation system, both tools work equally well — and Codex CLI’s simpler footprint may be easier to manage.

Configuration and Project Context

Codex CLI configuration is split into provider/model config (TOML) and per-project instructions (a AGENTS.md or similar file that the agent reads when present). This is intentionally minimal.

Claude Code has layered configuration:

• CLAUDE.md files (project-level, directory-level, user-level) for persistent instructions
• .claude/settings.json for permission rules, hook definitions, and tool settings
• Slash commands like /memory to edit instructions during a session
• Environment variables for API routing and authentication

The CLAUDE.md approach is useful for teams that want every agent session to start with a shared understanding of the codebase conventions, review checklists, or allowed libraries. Codex CLI does not have an equivalent built-in mechanism, though you can replicate it by prepending instructions in each prompt.

Approval Modes and Security Controls

Both tools give you control over how much the agent can do without asking.

Codex CLI’s three modes are simple and explicit:

• Suggest: shows proposed changes and asks before applying anything
• Auto edit: writes files without asking, but requires approval before running shell commands
• Full auto: runs without asking; useful for trusted pipelines

Claude Code’s permission modes map to similar concepts with more granularity:

• default: asks for approval on file edits and shell commands
• acceptEdits: auto-approves file edits, asks for shell commands
• auto: runs without asking (equivalent to Codex full auto)
• plan: shows a plan before executing; useful for reviewing multi-step tasks before running
• bypassPermissions: skips all checks (for trusted automated contexts)

Claude Code also supports a fine-grained allow/deny/ask rule system in settings.json, letting you approve specific commands permanently without changing the overall permission mode.

For teams with strict change-control requirements, Claude Code’s layered permission system provides more control. For individual developers who just want clear on/off behavior, Codex CLI’s three-mode system is easier to reason about.

Session and Context Management

Long coding sessions run into context limits. Both tools handle this, but differently.

Codex CLI manages context per-session. When a session ends, the context is gone. You start fresh on the next invocation.

Claude Code adds persistent session management:

• Named sessions that can be resumed with claude -r "session-name"
• /compact to summarize the current conversation and reduce token usage while continuing
• /branch to fork a conversation and try a different approach without losing the original
• /rewind to roll back to a checkpoint if a change went wrong
• /context to visualize how much of the window is used and where

For short, focused tasks — fix this bug, write this function, add these tests — the difference does not matter. For long refactoring sessions or tasks that evolve over multiple exchanges, Claude Code’s session continuity reduces the friction of context loss.

When to Use Codex CLI

Use Codex CLI when:

• You need to connect to OpenAI-compatible models directly (GPT-4o, o3, o4-mini, or third-party providers with OpenAI-format endpoints)
• You want to audit or modify the agent’s behavior at the source level
• Your workflow is purely terminal-based with no IDE integration needed
• You are embedding a coding agent into a CI pipeline or internal tool and want a minimal, auditable dependency
• Your security requirements demand explicit network-disabled sandboxing by default

When to Use Claude Code

Use Claude Code when:

• You want consistent behavior across terminal, VS Code, JetBrains, and desktop
• Your team benefits from shared CLAUDE.md project context across sessions
• You need session continuity — resuming named sessions, branching conversations, rewinding changes
• MCP server integration is part of your workflow
• You prefer the Anthropic-format API and want to route to Anthropic-compatible providers (including Novita AI)

Using Novita AI with Either Tool

Both tools accept Novita AI as a drop-in LLM backend. This matters when you want access to models that are not available through the tool’s default provider, or when cost is a constraint: models like DeepSeek V3, Qwen3-Coder, and Kimi K2 on Novita AI run at significantly lower per-token rates than Anthropic’s or OpenAI’s own flagship models.

Codex CLI with Novita AI: Configure model_provider in ~/.codex/config.toml to point at https://api.novita.ai/openai. See the full model list and setup steps in How to Use Codex with Novita AI Models.

Claude Code with Novita AI: Set ANTHROPIC_BASE_URL=https://api.novita.ai/anthropic and pass a Novita API key. The --model flag or ANTHROPIC_MODEL env var selects the specific model. Full CLI reference at Claude Code CLI Documentation.

Novita AI’s role here is as an inference backend, not an IDE layer. Once the environment variable is set, Codex CLI and Claude Code behave exactly as they would with their default providers — the model changes, the tool interface does not. This makes it straightforward to test different models (DeepSeek for reasoning-heavy tasks, Qwen3-Coder for code generation, GLM-4.7 for tool-heavy agentic work) without switching tools or workflows.

For teams building their own agentic pipelines or coding platforms, Novita AI also offers isolated sandbox environments for running agents — separate from the local machine, with scoped file access and controlled execution.

FAQ

Is Codex the same as the original OpenAI Codex model?

No. The original Codex was a code-generation model released by OpenAI in 2021 and later deprecated. Codex CLI is a separate product — an open-source terminal agent released in 2025 that uses current OpenAI models (GPT-4o, o3, etc.) through the Chat Completions API. The names are similar but the products are unrelated.

Can I use GPT-4o or newer OpenAI models with Codex CLI?

Yes. Codex CLI’s model field in the TOML config accepts any model ID that the configured provider supports. If you point it at OpenAI’s endpoint, gpt-4o, o3, o4-mini, and other current models all work.

Does Claude Code support OpenAI-compatible endpoints?

Not directly. Claude Code uses the Anthropic Messages API format, so it requires a provider that exposes an Anthropic-compatible endpoint. Novita AI supports this. OpenAI’s endpoint uses a different format and is not compatible.

Which tool is cheaper to run?

Both tools send API requests, so cost depends on the model and provider you connect to — not the tool itself. For either tool, switching to a lower-cost model through Novita AI — such as DeepSeek V3 or Qwen3-Coder — is the main cost lever. Check current pricing on the Novita AI model library.

Can I use both tools together?

Some teams do. Codex CLI is lightweight enough to drop into CI or scripted contexts, while Claude Code handles the interactive development session in VS Code. The tools do not share sessions, so combining them means maintaining separate configurations — manageable but worth being intentional about.

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Recommended Reading

1. How to Use Codex with Novita AI Models: Complete Setup Guide
2. Claude Code CLI Documentation: Setup, Slash Commands, and LLM API Integration
3. CLI vs IDE Coding Agent: What’s the Smarter Choice for Your Next Project