Can I use Claude Code, Codex and Grok in the same app?

Yes. Brainwrite starts the agent command-line tools you have installed and signed in to, and lets you pick an engine and model for each bot and each thread. A coding bot can run on Codex while a writing bot runs on Claude and a research bot runs on Grok, all in one workspace.

Who pays for AI usage when Brainwrite runs Claude Code or Codex?

Your provider does. Each engine uses your own login or API key, and that provider bills usage under its own terms and limits. Brainwrite plans do not include AI usage, and Brainwrite does not turn one provider's subscription into access to another. Per-thread token and cost figures help you track spending.

Which is better for AI agents: Claude Code, Codex or Grok?

There is no single answer, and we do not publish benchmark rankings. Choose based on the subscription you already pay for, the features your bot needs, and how each engine performs on your own tasks. In Brainwrite you can run the same prompt in two threads on different engines and compare the results directly.

Comparisons

Claude Code vs Codex vs Grok: Picking an Engine per Bot

Claude Code, Codex and Grok Build compared as AI agent engines: what each is, how you sign in, who bills you, and how to pick one per bot in Brainwrite.

Bhavik Fuletra·September 28, 2026·5 min read

Claude Code, Codex and Grok Build are agentic command-line tools from Anthropic, OpenAI and xAI. Each reads files, runs commands and edits code on your machine. In Brainwrite you do not pick one for everything. You pick an engine per bot, and per thread, using the logins you already have. Your provider bills the usage.

What are Claude Code, Codex and Grok Build?

All three are coding agents that run in your terminal. Here is how each provider describes its tool, with links to the official pages.

Claude Code is Anthropic's tool. Its overview page calls it "an agentic coding tool that reads your codebase, edits files, runs commands, and integrates with your development tools." Most ways of using it require a Claude subscription or an Anthropic Console account.
Codex CLI is OpenAI's tool. Its CLI page says it lets you "inspect code, make changes, run commands, and automate repeatable work without leaving your terminal." You can sign in with ChatGPT, and OpenAI's pricing page says API-key use is billed at API pricing.
Grok Build is xAI's tool. Its documentation describes "a powerful and extensible coding agent" that can run interactively, headlessly in scripts, or through the Agent Client Protocol (ACP) in other apps. It signs in through your browser on first launch, or with an xAI API key.

Plans, limits and model names change often. Check each provider's page for what your account includes today.

How does Brainwrite use these engines?

Brainwrite does not send your messages through a Brainwrite model account. It starts the agent CLIs installed on your computer and turns their output into one consistent chat app. That means:

You install and sign in to each CLI yourself.
Brainwrite detects installed engines during setup and in Settings → Engines. Restart the app after installing or signing in to a CLI.
If detection fails, you can set an explicit path to the executable.
An engine that is unavailable stays visible with a reason, instead of breaking the others.

The agent engines docs summarise how each one connects:

Engine	How you sign in	What Brainwrite notes
Claude	Claude CLI login	Strong support for tools, approvals, sessions and local computer use
Codex	Codex CLI login	Model discovery, approvals, steering and computer tools
Grok	Grok CLI login	Model catalog and sessions over ACP

Claude, Codex and Grok are not the only options. Brainwrite also supports Cursor, Kimi, Factory Droid, Antigravity (Google), OpenCode, Qwen, Hermes and Pi, plus the Mistral API without a CLI. Local models run through OpenCode. See bring your own model.

Who pays for usage when you bring your own engine?

Your provider. This is the most important point and the easiest to miss.

Your CLI login or API key decides what you can access and who bills you.
Brainwrite plans do not include AI usage. See pricing.
Brainwrite does not turn one subscription into access to another provider. A Claude plan does not give a bot access to Codex.
Each provider's terms and limits apply, including rate limits on subscription plans.

To see what a bot costs, each thread shows uncached input, cached input and output tokens, plus cost when the provider reports it. A missing cache figure is shown as unknown, not zero. See usage and cost.

How do you pick an engine for each bot?

We do not publish benchmark rankings, and we would be wary of anyone who claims one engine wins at everything. Results depend on the task, the prompt, the model version and your account. Use practical criteria instead.

Start with the subscription you already pay for

If you already pay for Claude, start your bots on Claude. If your team runs on ChatGPT, start with Codex. Adding a second paid provider only makes sense once you have a task where the first one falls short.

Match the engine to what the bot needs

Look at the features your bot uses, not just its writing quality:

Approvals. If the bot will touch email, files or the shell, choose an engine that supports approval cards. Claude and Codex both do.
Computer use. Brainwrite's docs list local computer use as a strength of the Claude engine. Codex bots use the browser and computer you select in Brainwrite.
Steering. Codex supports steering a run while it works.
Several accounts. If you need separate Work and Personal logins, that is Claude only today. See multiple Claude accounts.

Test on your own task

The fairest comparison is your own work. Brainwrite makes this cheap:

Open two threads on the same bot.
Set one thread to Claude and the other to Codex in the chat header.
Send the same prompt to both.
Compare the output, the time taken and the cost shown on each thread.

Each thread remembers its own model, so the test does not change the bot's other conversations. Changing a model affects future turns. It does not rewrite earlier history.

What does a mixed-engine team look like?

Because the engine is set per bot, one team can use several. A sketch:

Bot	Role	Engine idea
Chief of Staff	Receives requests, delegates, summarises	Whichever you trust most for judgment
Code bot	Works in one repository	Claude or Codex
Research bot	Reads pages in the built-in browser	Any engine with the tools you need
Private bot	Handles sensitive notes	A local model through OpenCode

When a Chief of Staff creates a new specialist, you can ask for a specific engine, model and reasoning effort. If you do not, the new bot uses your workspace default, not the Chief's model.

Brainwrite vs using a CLI on its own

You can use Claude Code or Codex directly in a terminal, and for single coding sessions that may be all you need. Brainwrite adds a team layer on top: bots with memory, threads, groups, routines, approval cards, connected apps and a cost view across engines. Our Claude Code comparison and Codex comparison go into the differences.

Try it

Brainwrite runs on macOS today. Install at least one agent CLI and sign in, then download Brainwrite and choose a plan on the pricing page. Make one bot per engine you already pay for and give them the same small task before deciding which bot gets which job.