Muse Code vs Codex CLI
Both read AGENTS.md, both sandbox by default, both fan out to parallel agents. One of them is open source and one of them is $5 a month.
Updated September 4, 2026 · Independent comparison — Muse Code, Codex CLI are separate products.
Muse Code
Meta's local-first terminal coding agent
Muse Code is Meta's terminal coding agent, in beta from 2026-08-05 and generally available on 2026-09-01. It ships as a single static binary with no language runtime to install, and everything except model inference runs on your machine — the agent, its subagents and the session logs. Long jobs fan out to child agents in isolated git worktrees, with concurrency scaled to your core count. It reads AGENTS.md, the same file Codex uses, and will import a Codex skills folder directly. Plans start at $5/month; the Meta Model API offers pay-as-you-go, and a Contributor tier roughly 12x cheaper if you let Meta train on your code.
Codex CLI
OpenAI's open-source terminal coding agent
Codex CLI is OpenAI's terminal coding agent and, unlike almost everything else in this category, the harness itself is open source — the cloud product wrapped around it is not. It runs GPT-5.6 and GPT-5.3-Codex, driven either by a ChatGPT plan or an OpenAI API key, and spans CLI, IDE extension, web, iOS and Codex Cloud. Its distinguishing feature is that a consumer ChatGPT subscription includes background and cloud compute rather than only local runs, so delegated tasks draw on the same quota instead of being a separate SKU. Approval modes, OS sandboxing, MCP and AGENTS.md are all first-class.
Bottom line
These two are closer than any other pair in the category: both read AGENTS.md, both sandbox at the OS level by default, both fan work out to parallel agents. The differences are openness and delivery. Codex CLI's harness is open source and its consumer subscription uniquely includes cloud and background compute, so delegated tasks cost no extra SKU. Muse Code is proprietary and local-only, but it is cheaper at every tier — $5 against $8 at entry, $50 against $200 at the top — and it will import a Codex skills folder directly, which makes trying it nearly free in effort. Codex CLI is the safer institutional choice; Muse Code is the cheaper one, provided you stay off the Contributor tier that pays for its discount with your code.
Pricing
| Feature | Muse Code | Codex CLI |
|---|---|---|
| Free tier | ✗ | Limited Codex access on ChatGPT Free |
| Entry paid plan | $5/month (Everyday Usage) | $8/month (ChatGPT Go); $20/month Plus |
| Higher-usage plans | $15/month (3x), $50/month (10x) | ChatGPT Pro from $100/month; $200/month tier |
| Subscription bundles anything else | No — the plan is the agent | Yes — the whole ChatGPT product |
| Pay-as-you-go option | Meta Model API: $1.25 in / $4.25 out / $0.15 cached per 1M | OpenAI API token pricing |
| Discount for training rights | Contributor tier: ~$0.10 in / ~$0.20 out per 1M | ✗ |
Openness
| Feature | Muse Code | Codex CLI |
|---|---|---|
| Harness licence | Proprietary | Open source |
| Model weights | Closed | Closed |
| Fork and self-host the agent | ✗ | Yes — the cloud product stays proprietary |
| Bring your own key | Meta Model API key | OpenAI API key |
Models
| Feature | Muse Code | Codex CLI |
|---|---|---|
| Model family | Muse Spark 1.2 and 1.3 | GPT-5.6 and GPT-5.3-Codex |
| Context window | 1M tokens | ~1.05M tokens on GPT-5.6 |
| Reasoning effort control | none through ultra, default high | reasoning.effort none through max |
| Multimodal input | Image and video, plus voice mode and web search | Image input |
| Vendor-published coding standing | Meta's table: Muse Spark 1.3 at 88.8 on Terminal-Bench 2.1, 75.4 on DeepSWE v1.1 | Meta's same table: GPT-5.6 Sol ties at 88.8 on Terminal-Bench 2.1, 73.0 on DeepSWE v1.1 |
Agent architecture
| Feature | Muse Code | Codex CLI |
|---|---|---|
| Parallel work | Child agents in isolated git worktrees, concurrency roughly core count minus two | Subagents plus Codex Cloud tasks on the same subscription quota |
| Cloud or background execution | ✗ | Codex Cloud, included with the plan |
| Where the agent runs | Fully local; only the model is hosted | Local, or delegated to Codex Cloud |
| Project instructions | AGENTS.md, falling back to CLAUDE.md | AGENTS.md |
| Imports skills from other agents | Reads .codex/skills and .claude/skills | ✗ |
| Session recovery | Append-only event log, replay-exact and restart-safe | Session resume |
Surfaces & safety
| Feature | Muse Code | Codex CLI |
|---|---|---|
| MCP support | Enabled by default — stdio and streamable_http | ✓ |
| IDE extension | ✗ | ✓ |
| Web or mobile | Web access via dev.meta.ai | Web and iOS |
| SDK | TypeScript SDK in developer preview | Codex SDK |
| Platforms | macOS and Linux; Windows needs WSL2 | macOS, Linux and Windows |
| Approval controls | on-request default; rm -rf and sudo always prompt | Configurable approval modes |
| OS-level sandbox | Seatbelt on macOS, bubblewrap on Linux; fails closed | Sandboxed by default |
The Verdict
Choose Muse Code if...
- ✓You want the cheapest capable terminal agent, at $5/month
- ✓You want everything except inference to stay on your machine
- ✓You work in large repositories where worktree isolation prevents collisions
- ✓You want image and video input, voice mode and web search in the agent
- ✓You will trade training rights for roughly 12x cheaper tokens
Choose Codex CLI if...
- ✓You want an open-source harness you can read, fork and audit
- ✓You want cloud and background tasks included in a consumer subscription
- ✓You want CLI, IDE, web and iOS coverage from one product
- ✓You need native Windows support without WSL2
- ✓Your ChatGPT subscription already covers the cost
Frequently Asked Questions
Can Muse Code use my existing AGENTS.md and Codex skills?
Yes. Muse Code reads the same AGENTS.md file Codex CLI uses, scans .codex/skills automatically, and ships muse skills import --from codex for an explicit migration. Meta built the compatibility in on purpose, so switching an existing Codex project across requires no rewriting.
Is Codex CLI actually open source?
The CLI harness is. The cloud product built around it — Codex Cloud, the web and iOS surfaces — is proprietary. So you can read and fork the agent that runs on your machine, but not the service that runs delegated tasks. Muse Code is proprietary end to end, and Muse Spark's weights are closed.
Which one is cheaper?
Muse Code, at every tier. Entry is $5/month against ChatGPT Go's $8, and Muse Code's top tier is $50/month against ChatGPT Pro's $100 and $200 tiers. On tokens, Muse Spark is $1.25 in / $4.25 out per million. The caveat is that a ChatGPT subscription buys the whole ChatGPT product plus Codex Cloud compute, while a Muse Code plan buys the agent and nothing else.
Does Muse Code have a cloud mode like Codex Cloud?
No. Muse Code is local-first by design — the agent, its subagents and the session logs all run on your machine, and only model inference is hosted. If you want to fire off a task and close the laptop, Codex Cloud does that on a consumer plan and Muse Code has no equivalent.
How does Muse Code run tasks in parallel?
It creates one git worktree per child agent, checked out from the lead agent's commit, so parallel agents never write over each other's files. Concurrency is roughly your core count minus two, clamped between 2 and 16, and children run one level deep — they cannot spawn their own children.
1DevToolRun both, and let one cover the other's rate limits
Muse Code and Codex CLI share a config format and a sandboxing philosophy, which makes them unusually easy to run side by side — cheap bulk work on one, cloud delegation on the other. 1DevTool runs 14 CLI agents including Codex, Claude Code, Gemini, Cursor and Cline in persistent terminals in one window, each on its own key or subscription, with automatic fallbacks when one is rate-limited. It adds a 23-engine database client, an HTTP client, browser profiles, Docker and Git worktrees around them. From $29 one-time, no subscription.