A Hands-On AI Coding Agent Project: My Retirement Countdown

🔍 Read the full analysis: A Hands-On AI Coding Agent Project: My Retirement Countdown on ThorstenMeyerAI.com

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Thorsten Meyer says he built and published Altersteilzeit, a free web app for people counting down to partial retirement in Germany, with help from the Claude Opus 5.5 coding agent over five days. The project grew from a request for a one-minute animated film into a browser-based service with a working-day countdown, a narrator and 19 3D games, according to Meyer’s October 13 account.

Meyer says he began on Monday, September 28, 2026, asking the agent for a short film about the two phases of Altersteilzeit in the block model: a period of regular work followed by an equally long period away from work. By Friday, October 2, he had approved the public release. The app lets users enter the start date of either phase and choose a model ranging from 1:1 to 5:5.

The app calculates the other phase date and estimates remaining working days, counting weekdays while subtracting public holidays in the user’s German federal state and any leave entered. Its features include a daily countdown and milestones, a calendar export, a printable calendar and a finder for bridge days. A short film depicts the work and leisure phases, while games use years, months and weeks as the basis for levels and play. Meyer’s account describes 19 game options, though an earlier development note in the same account refers to 15 modes.

Meyer says the app has no accounts, cookies or tracking, and performs its calculations in the browser. Dates in a shared link are stored after the “#” in the address, which, he says, means they are not sent to a server in a standard web request. He reports that all 24 project commits were co-authored by the coding agent, while he supplied directions, made decisions and approved releases.

The Human Work Behind the App

The account offers a practical example of how an AI coding agent can contribute to a software project that reaches a public release. Meyer attributes work to the agent across engineering, translation, audio production and deployment, but also describes a continuing role for himself in defining what to build and judging whether the result was ready.

That distinction matters for readers trying to understand what “built by AI” means in practice. Meyer says the agent produced code and tests, split large tasks among sub-agents, and generated text and voice assets. He says he set the product’s tone, chose the sea as the image of retirement freedom, selected voices and dialects, and made release decisions. The project is therefore evidence of a reported human-agent workflow, not a controlled measure of how quickly or reliably AI agents can build software in general.

The app’s focus also gives the project a specific use: turning a long retirement timeline into a daily count, with local holidays and leave included in the calculation. Its usefulness will depend on the accuracy of its dates and holiday data for each user, as well as whether its features work as described. Meyer’s account does not provide independent testing or user numbers.

From Film Request to Public App

Altersteilzeit is a German arrangement for reducing work before retirement. In the block model described by Meyer, a person works as usual during an active phase and is then released from work during a passive phase. In a 4:4 arrangement, for example, each phase lasts four years. The app is intended to help people follow the working days remaining in the active phase.

Meyer’s timeline describes a rapid expansion across five working days. The initial film request was followed by date calculations and game prototypes. He says the daily view, language support, additional games, badges, bridge-day tools, narration and sound were added over subsequent days. He reports that the final project included seven languages and five German dialects, and that versions of the narrator were produced in multiple languages.

The source account says the project involved about 18,000 lines of JavaScript and Python, 15 test scripts, more than 1,800 text strings per language in 12 languages, and 1,224 voice clips. It also describes 17 sound effects and screenshots for every language. These figures are Meyer’s own account; the article provides no independent audit of the code, assets or development time.

“The interesting part is not how much an AI agent can build, but what was still left for me to do.”

— Thorsten Meyer, describing the project

What the Account Does Not Establish

The development timeline, workload figures and feature descriptions come from Meyer’s account. There is no independent verification in the source material of the reported code volume, testing, production process or the agent’s exact share of the work. The account also does not provide download figures, user feedback, operating costs or a comparison with a project completed without an AI agent.

Some scope details are not fully reconciled: Meyer describes a 3D game with 19 ways to play, but his day-by-day account refers to 15 game modes. He also reports seven languages and five dialects, while stating that text and voice work covered 12 languages. The material does not explain how those counts relate to one another. It does not specify the holiday-data source, how often that data is updated, or whether the working-day calculations have been independently checked.

The App’s Use and Verification

Meyer’s account says the app was publicly available by October 2, 2026, and describes the October 13 article as a report on how it was built. It does not announce a later release date or a specific upcoming feature. The immediate next step for readers interested in the project is to check the published app’s current features and privacy information directly.

Further reporting could establish how people use the service, whether its holiday and leave calculations are accurate across German states, and how the app is maintained. Meyer has not supplied independent test results or usage data in the source material, so its reliability and reach remain open questions.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German form of partial retirement. In the block model described by Meyer, a person works during an active phase and then spends a matching period away from work.

What does the app calculate?

Users enter the start date of one phase and choose a model. The app calculates the other date and counts working days, subtracting public holidays for the selected German federal state and any leave entered, according to Meyer.

What did the AI coding agent do?

Meyer says the Claude Opus 5.5 coding agent helped write and test software, produce translations and voice clips, and support deployment. He says he directed the work, made product and creative decisions, and approved releases.

Is the app independently verified?

The source account does not include independent testing or an audit of the app’s calculations, privacy claims, code or reported development figures. Those details should be treated as Meyer’s descriptions of his project.

Source: ThorstenMeyerAI.com