OpenAI Codex (included in ChatGPT Free, desktop app for light coding tasks)
OpenAI
ChatGPT Free ($0 per month) already includes Codex, usable in the desktop app with GPT-6 Luna for light coding tasks; the official page does not publish exact limits for the free plan
Official Codex pricing page verbatim: "ChatGPT Work and Codex are included in your ChatGPT Free, Go, Plus, Pro, Business, Edu, or Enterprise plan". Free card: "Free. Explore Codex capabilities on quick coding tasks. $0 /month. GPT-6 Luna at Standard speed in the desktop app, subject to rollout". By comparison the Go plan at $8 per month is also limited to GPT-6 Luna in the desktop app; only the Plus plan at $20 per month adds Codex on the web, in the CLI, in the IDE extension and on iOS, and includes GPT-6.1 Sol. The page also notes that ChatGPT Work and Codex share usage.
The official page only says "quick coding tasks" and gives no task count or time window for the free plan; usage is shared with other ChatGPT features, and "subject to rollout" means availability opens to accounts in batches, so check in the app before relying on it. The Free plan covers the desktop app only, not the CLI, IDE extension or web version. ChatGPT is not offered in mainland China, so you need a compliant overseas network and account.