OpenAI Codex: pricing, what it does and real use cases

Jobs it fits

• Port or rewrite code against a test suite
• Delegate coding tasks to run in the cloud

Pricing

Or use your own API key and pay API prices.

Source: https://developers.openai.com/codex/pricing, checked October 21, 2026. Prices change; confirm on the vendor's page.

What people are doing with it

• Use caseCoding

  A developer ran Google's open Gemma 4 model locally inside Codex CLI and wrote up how a coding agent performs without a cloud model.

  Apr 2026Daniel Vaughan (blog), via Hacker News ↗

• Use caseCoding

  Simon Willison used Codex CLI to port the JustHTML HTML5 parser from Python to JavaScript in about 4.5 hours, using the existing html5lib test suite to check the agent's work.

  Dec 2025Simon Willison's Weblog ↗

• Use caseCoding

  Semgrep's security researchers had Claude Code and OpenAI Codex hunt for vulnerabilities in real Python web apps: both found real bugs (about 20 high-severity), but more than 80% of what they flagged were false positives.

  Sep 2025Semgrep blog ↗

Each one is summarised in our own words from the linked public post. Vendor case studies are labelled; they report the vendor's and customer's numbers, not ours. All use cases.

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