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Comparisons4 min read

Claude Code vs Codex: how they differ, and using both

Claude Code is Anthropic's coding agent; Codex is OpenAI's. How sign-in, apps and instruction files differ, and how to run both side by side.

A new Mirasim session set to Codex, ready for its first promptA new Mirasim session set to Codex, ready for its first prompt

The short answer

Both are coding agents that read your code, edit files and run commands. The practical difference is whose account you sign in with: Claude Code runs on Anthropic's models with a Claude subscription or an Anthropic Console account; Codex runs on OpenAI's models with a ChatGPT plan or an API key.

Claude Code
You already pay for a Claude plan
Codex
You already pay for ChatGPT Plus, Pro or a work plan
Codex CLI (Apache-2.0)
You want a CLI whose source you can read and change
Both, side by side in Mirasim
You'd rather not choose, or want to compare them on your own code

Which one writes better code depends on the task and changes with every model release, so the most reliable test is your own repository.

At a glance

Claude CodeCodex
Made byAnthropicOpenAI
ModelsAnthropic's Claude modelsOpenAI's GPT models
Sign inClaude subscription or Anthropic Console accountChatGPT Plus, Pro, Business, Edu or Enterprise, or an API key
Where it runsTerminal, VS Code, JetBrains, desktop app, browserTerminal, IDE extension (VS Code, Cursor, Windsurf), desktop app, browser
Instructions fileCLAUDE.md, or an AGENTS.md in its placeAGENTS.md
Extending itMCP, skills, hooks, subagentsMCP, skills, hooks, subagents

From each product's own documentation on November 8, 2026. Both change often; see the sources at the end.

Installing them

Claude Code
curl -fsSL https://claude.ai/install.sh | bash on macOS, Linux and WSL; irm https://claude.ai/install.ps1 | iex in Windows PowerShell. Homebrew and WinGet work too. Run claude in a project and sign in.
Codex
curl -fsSL https://chatgpt.com/codex/install.sh | sh on macOS and Linux, the PowerShell script on Windows, or npm install -g @openai/codex. Run codex and choose Sign in with ChatGPT.

In Mirasim you don't need either command: Agent Config installs both, and each keeps its own sign-in.

Using both in Mirasim

One Mirasim windowClaude Code and Codex sessions in panes
  • Side by sideGive both the same task and compare their changes
  • Hand over mid-taskSwitch a session from Claude Code to Codex and keep the conversation
  • Their own sign-insYour Claude and ChatGPT accounts, or Mirasim credit for either
  • One sidebar⌘K searches both agents' transcripts
  • Back to the terminalCopy resume command picks the session up in the agent's own CLI
Mirasim runs the Claude Code and Codex installed on your computer, unmodified, so new releases reach you as soon as you update them.

Article · Running coding agents unmodified by changing one URL → How Mirasim runs the original Claude Code and Codex without modifying them.

Article · Cursor vs Claude Code: an editor with an agent, or an agent for any editor → Choosing between Cursor and Claude Code.

Questions

Which one is better at coding?
There's no answer that holds for long: it depends on the task and on whichever models were released last. Give both the same task in two panes and compare the diffs.
Can one subscription cover both?
Not from Anthropic or OpenAI: Claude Code needs a Claude or Console account, Codex a ChatGPT plan or OpenAI API key. In Mirasim, Mirasim credit runs either one.
Can my team share my Claude or ChatGPT subscription?
No. Personal subscriptions are for their owner only. A session your team shares in Mirasim runs on a key shared with members or on space credit.
Do both work on Windows?
Yes. Both ship a PowerShell installer, and Mirasim runs on Windows, macOS and Linux.
How much do they cost?
See claude.com/pricing and developers.openai.com/codex/pricing. For Mirasim, see mirasim.ai/pricing.

Sources

Checked against each product's documentation on November 8, 2026: code.claude.com/docs/en/overview for Claude Code; github.com/openai/codex (README) and learn.chatgpt.com/docs for Codex. Both change quickly, so check those pages for the latest.

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