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OpenAI's coding agent. It works in ChatGPT, in the cloud, in your code editor and in the terminal.
Codex is OpenAI's AI agent for building and changing software. You describe what you want, and it writes the code, runs it and fixes problems. In the examples here, people also point it at a folder of documents to research and compare.
Used in the entries here to build a clinic's AI scribe, to turn a folder of client notes into a priced hotel shortlist, and to make designs and listing copy for a print-on-demand shop.
ProductStrong evidence (evidence grade B)
Solo-owned SaaS (Preceden, a timeline maker)
In about a month, scheduled Claude Code routines shipped 1,531 PRs to Preceden, a 17-year-old SaaS, across 20 batched deploys with none reverted. The owner says MRR impact isn't visible yet.
SalesStrong evidence (evidence grade B)
Solo founder of quoting software for industrial insulation contractors
A solo founder selling quoting software to industrial insulation contractors runs about 16 agents on evenings and weekends; 214 agent-written cold emails at a 3.3% reply rate produced his first pilot customer without him touching the funnel until the demo.
SalesVendor or secondhand (evidence grade C)
Travel advisor (Worldvia Travel Network)
From a folder of old client notes and one short prompt, Codex Desktop worked out what the clients liked, checked live hotel booking calendars and returned three options with availability, nightly rates and a budget warning.
OperationsLight evidence (evidence grade D)
Outpatient physical therapy clinic (neurorehab)
An outpatient PT clinic owner used OpenAI Codex to build a Python AI scribe in about 5 hours that transcribes a session and writes a SOAP note in the clinic's own style, at about $0.11 per one-hour session.
Strong evidence (evidence grade B)
Seasonal print-on-demand Etsy shop (The Cozy Bow Company, a side project)
A builder drafts designs with AI, says yes or no, and code lists them on Etsy.
No income sharedNo sales figures yet: 85 live listings by the end of week one, which hadn't brought in visitors.
Know before you start
Included in ChatGPT plans. chatgpt.com/pricing lists limited Codex use on Free and Go. OpenAI's Codex page lists Plus at $20 a month, Pro at $100 a month for higher limits, and Business at $20 per user a month (billed yearly, two or more seats).
Price checked Oct 15, 2026 on openai.com. Prices and plans change; check the official site before you buy.