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Original: Simon Willison · 02/02/2026

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Summary

Since the launch of GPT‑5.2-Codex in mid-December, overall Codex usage has doubled. Introducing the Codex app OpenAI just released a new macOS app for their Codex coding agent. I’ve had a few days of preview access - it’s a solid app that provides a nice UI over the capabilities of the Codex CLI agent and adds some interesting new features, most notably first-class support for Skil

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Key Insights

“Since the launch of GPT‑5.2-Codex in mid-December, overall Codex usage has doubled.” — Highlighting the rapid adoption and usage growth of Codex.
“Codex is built on a simple premise: everything is controlled by code.” — Explaining the foundational philosophy behind Codex.
“it’s taking us some time to get really solid sandboxing working on Windows.” — Discussing the technical challenges of bringing Codex to Windows.

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Topics

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Full Article

# Introducing the Codex app
Author: Simon Willison
Published: 2026-02-02
Source: https://simonwillison.net/2026/Feb/2/introducing-the-codex-app/#atom-everything
<p><strong><a href=“https://openai.com/index/introducing-the-codex-app/“>Introducing the Codex app</a></strong></p> OpenAI just released a new macOS app for their Codex coding agent. I’ve had a few days of preview access - it’s a solid app that provides a nice UI over the capabilities of the Codex CLI agent and adds some interesting new features, most notably first-class support for <a href=“https://developers.openai.com/codex/skills”>Skills&lt;/a>, and <a href=“https://developers.openai.com/codex/app/automations”>Automations&lt;/a> for running scheduled tasks.</p> <p><img alt=“Screenshot of a macOS desktop application with a dark sidebar and light main content area. Left sidebar shows navigation items “New thread”, “Automations”, “Skills”, and a “Threads” section containing two project folders: “local-codex-scratch” with tasks “Reply to greeting task 2h” and “List Codex.app contents 3h”, and “shot-scraper” with tasks “Validate tests on dependency… 3h”, “Document shot-scraper CLI usage 18h” (highlighted), and “Run this: uv run pytest -x 1d”. Bottom left shows “Personal”. Top bar displays “Document shot-scraper CLI usage shot-scraper” with “Open” and “Commit” dropdown buttons. Main content shows a conversation: user message “Build a skill describing how to use the shot-scraper CLI tool” followed by assistant responses: “I’ll use the skill-creator skill, scan the repo for existing shot-scraper docs/commands, then draft a concise skill in this workspace and sanity-check it.” then “I’ve confirmed the skill-creator scripts exist. Next I’ll inspect the CLI entrypoint and docs, then scaffold a skill under skills/ in this repo.” then “I’ve scaffolded skills/shot-scraper-cli/. I’ll now replace the template SKILL.md with a task-focused skill and add a compact CLI reference under references/.” then “I’ll run the skill packager/validator next to ensure the new skill structure is valid.” then “Done — I created and packaged the skill. Key outputs: • Skill definition: SKILL.md • Compact reference: cli-reference.md • Packaged skill: shot-scraper-cli.skill”. Bottom shows input field with placeholder “Ask for follow-up changes”, ”+ Custom Medium” dropdown, and “Local” and “main” branch indicators.” src=“https://static.simonwillison.net/static/2026/codex-app.jpg” /></p> <p>The app is built with Electron and Node.js. Automations track their state in a SQLite database - here’s what that looks like if you explore it with <code>uvx datasette ~/.codex/sqlite/codex-dev.db</code>:</p> <p><img alt=“Database schema documentation on light gray background showing three tables: “automation_runs” (teal underlined link) with italic columns “thread_id, automation_id, status, read_at, thread_title, source_cwd, inbox_title, inbox_summary, created_at, updated_at, archived_user_message, archived_assistant_message, archived_reason” and “1 row”; “automations” (teal underlined link) with italic columns “id, name, prompt, status, next_run_at, last_run_at, cwds, rrule, created_at, updated_at” and “1 row”; “inbox_items” (teal underlined link) with italic columns “id, title, description, thread_id, read_at, created_at” and “0 rows”.” src=“https://static.simonwillison.net/static/2026/codex-dev-sqlite.jpg” /></p> <p>Here’s an interactive copy of that database <a href=“https://lite.datasette.io/?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsimonw%2F274c4ecfaf959890011810e6881864fe%2Fraw%2F51fdf25c9426b76e9693ccc0d9254f64ceeef819%2Fcodex-dev.db#/codex-dev”>in Datasette Lite</a>.</p> <p>The announcement gives us a hint at some usage numbers for Codex overall - the holiday spike is notable:</p> <blockquote> <p>Since the launch of GPT‑5.2-Codex in mid-December, overall Codex usage has doubled, and in the past month, more than a million developers have used Codex.</p> </blockquote> <p>Automations are currently restricted in that they can only run when your laptop is powered on. OpenAI promise that cloud-based automations are coming soon, which will resolve this limitation.</p> <p>They chose Electron so they could target other operating systems in the future, with Windows “<a href=“https://news.ycombinator.com/item?id=46859054#46859673”>coming very soon</a>”. OpenAI’s Alexander Embiricos noted <a href=“https://news.ycombinator.com/item?id=46859054#46859693”>on the Hacker News thread</a> that:</p> <blockquote> <p>it’s taking us some time to get really solid sandboxing working on Windows, where there are fewer OS-level primitives for it.</p> </blockquote> <p>Like Claude Code, Codex is really a general agent harness disguised as a tool for programmers. OpenAI acknowledge that here:</p> <blockquote> <p>Codex is built on a simple premise: everything is controlled by code. The better an agent is at reasoning about and producing code, the more capable it becomes across all forms of technical and knowledge work. […] We’ve focused on making Codex the best coding agent, which has also laid the foundation for it to become a strong agent for a broad range of knowledge work tasks that extend beyond writing code.</p> </blockquote> <p>Claude Code had to <a href=“https://simonwillison.net/2026/Jan/12/claude-cowork/“>rebrand to Cowork</a> to better cover the general knowledge work case. OpenAI can probably get away with keeping the Codex name for both.</p> <p>OpenAI have made Codex available to free and <a href=“https://simonwillison.net/2026/Jan/16/chatgpt-ads/“>Go&lt;/a> plans for “a limited time” (update: Sam Altman <a href=“https://x.com/sama/status/2018437537103269909”>says two months</a>) during which they are also doubling the rate limits for paying users. <p>Tags: <a href=“https://simonwillison.net/tags/sandboxing”>sandboxing&lt;/a>, <a href=“https://simonwillison.net/tags/sqlite”>sqlite&lt;/a>, <a href=“https://simonwillison.net/tags/ai”>ai&lt;/a>, <a href=“https://simonwillison.net/tags/datasette”>datasette&lt;/a>, <a href=“https://simonwillison.net/tags/electron”>electron&lt;/a>, <a href=“https://simonwillison.net/tags/openai”>openai&lt;/a>, <a href=“https://simonwillison.net/tags/generative-ai”>generative-ai&lt;/a>, <a href=“https://simonwillison.net/tags/llms”>llms&lt;/a>, <a href=“https://simonwillison.net/tags/ai-agents”>ai-agents&lt;/a>, <a href=“https://simonwillison.net/tags/coding-agents”>coding-agents&lt;/a>, <a href=“https://simonwillison.net/tags/codex-cli”>codex-cli&lt;/a>&lt;/p>

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Key Takeaways

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Notable Quotes

Since the launch of GPT‑5.2-Codex in mid-December, overall Codex usage has doubled.
Context: Highlighting the rapid adoption and usage growth of Codex.
Codex is built on a simple premise: everything is controlled by code.
Context: Explaining the foundational philosophy behind Codex.
it’s taking us some time to get really solid sandboxing working on Windows.
Context: Discussing the technical challenges of bringing Codex to Windows.
  • [[topics/ai-agents]]
  • [[topics/agent-native-architecture]]
  • [[topics/openai-api]]

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Originally published at https://simonwillison.net/2026/Feb/2/introducing-the-codex-app/#atom-everything.