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Until now, we were accustomed to the fact that working with advanced code generation models required being present at a computer, an IDE (integrated development environment), and a stable connection to a monitor. OpenAI changes this paradigm with this step. The integration of Codex into the ChatGPT mobile app allows users to stay in touch with their projects even in situations when they are not at their desk – during the commute to work, while waiting for coffee, or during a short break.
A new era: From chatting to controlling agents
The key shift is not just that you can "write code" on your phone. The main added value lies in the ability for asynchronous collaboration with AI agents. According to the official announcement by OpenAI, more than 4 million people already use Codex every week. The new feature allows Codex to perform long-running tasks on your laptop, Mac mini, or in a controlled remote environment, while you only monitor and control it via phone.
This creates a new work rhythm. Instead of having to wait for the AI to complete refactoring of the entire module, you can start the process, leave, and subsequently check the diffs (comparison of changes), terminal outputs, or test results on your mobile phone. If Codex encounters a problem or requires a decision, it will send you a notification that you can immediately approve or change the direction of the assignment.
How does it work technically? A secure bridge between mobile and machine
To be able to perform these operations securely, OpenAI implemented a so-called secure relay layer. This mechanism ensures that your machines on which Codex runs are not directly exposed to the public internet, which is critical from a cybersecurity perspective.
The application on the mobile phone loads the live state from your development environment. This means that you see exactly what the developer sees on the desktop:
- Screenshots from the browser or simulator.
- Terminal output in real time.
- Test results and potential errors.
- Code diffs, that is precise examples of what the AI changed in the code.
Comparison: OpenAI Codex vs. competition
This novelty places OpenAI in direct competition with other players striving for a similar degree of autonomy. If we compare the current situation, it looks as follows:
| Feature | OpenAI Codex (Mobile) | Anthropic Claude (Computer Use) | GitHub Copilot |
|---|---|---|---|
| Mobile agent management | Yes (high integration) | Partially (via API/web) | Limited (via IDE) |
| State synchronization | Real-time (Relay layer) | Low | Low |
| Autonomy | High (Agentic workflow) | High (Direct UI control) | Medium (Autocomplete/Chat) |
While Claude focuses on the model's ability to directly control the computer's user interface (so-called "Computer Use"), OpenAI in the mobile app concentrates on controlling an agent that runs on your own hardware. This is a fundamental difference for companies that cannot afford to send sensitive code to Anthropic's cloud but want to harness the power of AI on their own servers.
Impact on the Czech and European market
For Czech developers and technology companies, this update brings two main aspects. The first is efficiency. In an environment where there are more and more freelancers and digital nomads, Codex allows working on complex projects even outside the office.
The second, and perhaps more important aspect, is regulation and security. In the context of the EU AI Act and strict GDPR rules, the ability to have AI agents running in a controlled, local environment (instead of a purely cloud model) is a huge advantage. Companies in the Czech Republic can use Codex to automate routine coding tasks without having to risk exfiltration of source codes outside their secure infrastructure, because the mobile application only "translates" instructions and results via a secure relay channel.
Availability and language: The ChatGPT app is fully available in the Czech Republic. Although the code itself is primarily in English, the application interface and communication with the model support the Czech language, which facilitates giving instructions even for less advanced developers or technical managers.
Price and how to start
The Codex feature in the mobile app is not part of the free version. For full use of agentic functions and connection to development environments, a subscription to ChatGPT Plus (approx. 20 USD / month, converted around 470 CZK) or the business version ChatGPT Team/Enterprise is usually required.
To get started, you need to have your development environment set up (e.g., VS Code or a remote server) where Codex is ready to work, and subsequently log in to the same account in the ChatGPT mobile app on iOS or Android.
Is my code safe in the mobile app and not stored in OpenAI's cloud?
Thanks to the secure relay layer technology, your files and sensitive data remain on your original machine. The mobile app only displays outputs (diffs, terminal) and sends commands. However, OpenAI always recommends following your company's internal security policies regarding the use of AI tools.
Can I start a completely new project from scratch using my mobile phone?
Yes, you can give an instruction to create a new project. Codex will start working on your connected machine, create the necessary files and structure, and you can monitor the process in real time directly on your phone's display.
Does it require special setup in the terminal?
For full functionality, it is necessary to have an installed and configured environment that allows Codex to control (e.g., via API or specific plugins/interfaces that OpenAI provides for Codex). The standard installation of ChatGPT on mobile is not enough; you must have an active "workstation" to which the app connects.
