Codex CLI vs IDE Extension vs Codex Cloud: Choosing a Codex Surface

Codex is OpenAI's coding agent family, available in three surfaces: Codex CLI (local terminal), an IDE extension (in-editor), and Codex Cloud (hosted environments). All three share the same models and engineering capabilities; what differs is execution location and collaboration mode -- the official docs group modes into Local environments and Cloud environments, with the two local surfaces in the former and Cloud in the latter. This guide compares them across execution environment, security boundaries, automation, and scenarios, closing with the migration view for Cursor users.

1. One Table to Tell the Surfaces Apart

One line: the CLI is the full-capability surface, the IDE extension is the low-friction surface, Cloud is the background surface.

2. Codex CLI: Sandbox and Approvals Are the Core Design

The CLI runs in your terminal with the agent facing your filesystem directly -- so security is a first-class capability in the official docs:

• Sandbox: bounds file writes and system access, giving agent operations an explicit perimeter.
• Approvals: high-risk actions (networking, writes outside the workspace) require human confirmation.
• Network controls: internet access is managed separately, not granted by default.

This design turns "letting an agent modify code on my machine" from a trust question into a configuration question -- once the team standardizes sandbox and approval policies, agent operations are auditable. Combined with the git-worktree isolation pattern (agent in a separate worktree, review the diff, merge), the CLI's engineering discipline supports primary development work.

3. IDE Extension: The Low-Friction Entry for Editor Natives

The IDE extension embeds Codex in the editor: an integrated terminal runs the agent in-editor, and code review happens in the diff view. Its value is not capability difference -- capabilities are the same lineage as the CLI -- but friction difference: no window switching, changes and review in the same line of sight.

For users migrating from other AI editors (this week's Cursor users are the textbook case), the IDE extension is the smallest experience gap: install and go, with the learning cost concentrated in one new concept -- the sandbox-and-approvals model.

4. Codex Cloud: The Background Surface

Cloud moves execution off the local machine:

• Long-running work: test matrices and large refactors that would hog local machines -- or that you simply do not want to wait on -- run in hosted environments.
• Scheduled tasks: periodic checks and maintenance run automatically, with nobody needing to remember to start them.
• Environment isolation: cloud environments keep dependencies and configuration separate from local machines; a broken run does not touch your dev box.

Cloud's role is not to replace local surfaces but to take over the tasks that do not fit interactive execution -- the local surfaces handle human-in-the-loop development, Cloud handles execution without a human in the loop.

5. Scenario-Based Selection

Mixing is the norm: the IDE extension for daily changes, the CLI for refactors, Cloud for batches -- all three share the same account and capabilities, switched by task nature rather than pick-one.

Frequently Asked Questions

1. Do the three surfaces differ in models or capabilities?

Not fundamentally -- all three share the same Codex models and engineering capabilities. What differs is execution location and interaction: the CLI runs in your terminal with changes landing in your workspace; the IDE extension lives in the editor; Cloud runs in hosted environments and returns results. Choosing a surface is choosing where code and context live.

2. How do the CLI sandbox and approvals work?

The official docs treat security as a first-class CLI capability: the sandbox bounds file writes and network access, and the approval mechanism gates risky actions (networking, writes outside the workspace) behind your confirmation. This turns "letting an agent run on my machine" from a trust problem into a configuration problem -- with auditable operations, team adoption is much easier.

3. Which tasks belong in Codex Cloud?

Two kinds: long-running work -- test matrices and large refactors that would hog or overwhelm local machines -- and scheduled tasks for periodic checks and maintenance. Jobs execute in hosted environments and hand results back, leaving local resources alone.

4. Migrating from Cursor -- which surface first?

OpenAI announced model supply to Cursor ends 2026-11-12. Recommendation: editor-heavy users install the IDE extension first (smallest experience gap), terminal power users go straight to the CLI (fullest capability); the two coexist. Migration is a workflow change, not just a tool swap -- budget regression time and run low-risk tasks through the sandbox and approval setup first.

5. Is Code review a separate product or a surface?

It is a cross-surface capability: the official docs list Code review among Codex's core workflows, and both local changes and cloud tasks can feed it. Teams use it as a pre-PR self-check layer; combined with the sandbox it can run at scale without touching the main branch.

6. Can the surfaces be mixed?

Yes, and they should be. A common setup: daily small changes in the IDE extension, complex refactors in the CLI (stepwise inside the sandbox), batch and periodic work in Cloud. All three share the same account and capabilities -- switch by task nature rather than picking just one.

Next Steps

• The four-tool cross-comparison? Read Codex CLI vs Cursor vs Aider vs Claude Code: Four AI Coding Tools Compared (2026).
• New to Codex CLI? Read Getting started with OpenAI Codex CLI: from install to daily use.
• This week's Cursor cutoff in full? Read OpenAI Ecosystem Week 41 Flash (2026-08-28/29).