Sixteen Takes On A Retirement Countdown With An AI Coding Agent

🔍 Read the full analysis: Sixteen Takes On A Retirement Countdown With An AI Coding Agent on ThorstenMeyerAI.com

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Developer Thorsten Meyer says he used the AI coding agent Claude Opus 5.5 to build Altersteilzeit, a free web app for people counting down working days in Germany’s partial-retirement “block model,” amid wider discussion of coding-agent security. The project grew from a one-minute film request on September 28, 2026, into a public website released five days later, combining a daily countdown, a narrated film and 19 3D games.

Meyer described the work in an account published October 13 on ThorstenMeyerAI.com, offering a case study of an AI coding agent used in a real project. He says all 24 commits were co-authored by Claude Opus 5.5, while he supplied direction, made product and editorial decisions, reviewed the results and approved releases. The account presents the project as a report on one human-and-agent collaboration, not an independent evaluation of the coding agent’s capabilities.

Users enter a date marking the start of either the active or passive phase and select a model ranging from 1:1 to 5:5. The app calculates the corresponding date and working days, counting Monday through Friday and subtracting public holidays for the selected German federal state and any leave entered by the user. It then presents a daily total, milestones and a saying of the day. Other features include calendar exports, a printable countdown, bridge-day suggestions and a team countdown.

The site also includes a short narrated film and games that map time to play: for example, months and weeks form a maze, while working days become emails in a game called Mail Flood. Meyer says the project included seven languages and five German dialects, with narration and sound effects. He reports that the agent handled coding, tests, translations, audio production and deployment tasks; Meyer retained decisions about tone, voices, dialects, legal-page contact details and whether the film should have narration.

A Practical Test of AI-Assisted Building

The project offers a concrete example of how a coding agent can contribute across a small product’s development, rather than only generate an isolated code sample. Meyer’s account describes work spanning browser-based 3D, localization, testing and deployment, as well as the creation of voice clips and sound effects. Those details help show the breadth of tasks he says were delegated in this particular project.

It also illustrates the limits of the account. The five-day schedule and reported output come from the developer who made the app; they do not establish how the agent would perform on other projects, how much time the work would take without an agent, or whether the software has been independently audited. Meyer’s description points to a continuing human role in product choices, review and release approval, even with substantial agent involvement.

For users, the project’s stated privacy design is relevant because the app processes dates that can reveal personal plans. Meyer says there are no accounts, cookies or tracking, and that calculations happen in the browser. The date-sharing links put the information after the “#” in the address, which browsers do not send to the server as part of an ordinary request. The source account does not provide an external security or privacy review.

From Countdown Film to Web App

Altersteilzeit is a German partial-retirement arrangement. In the block model, an employee works an active phase and then has a passive phase of equal length; a 4:4 model, for example, pairs four years of work with four years away from work. Meyer’s app is designed to count working days across that schedule, accounting for the user’s state holidays and entered leave rather than simply counting calendar days.

Meyer says the original request, made on Monday, September 28, was for a short animated film about the two phases. On the first day, the work expanded to include date calculations and two game prototypes, which were combined into a single game. The account says a public version was online that evening with legal pages. Over the following days, Meyer added languages, the daily view, more games, badges, the bridge-day finder, narration and sound effects. He reports approving the release on Friday, October 2, followed by the addition of five German dialects.

The article describes the final game collection as having 19 games, while its day-by-day account says that the game was expanded through successive additions. The games use calendar time as their underlying structure: a year of the active phase can become a level, and leave can affect gameplay. Meyer also says names were chosen to avoid using other companies’ trademarks.

“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’s human role

Independent Checks and User Numbers

The details available come from Meyer’s own account. No independent assessment is provided of the code, the reported development time, the agent’s contribution or the app’s security and privacy practices. The article also does not state how many people have used the website, whether it has been tested against every relevant holiday calendar or how the working-day calculations handle every user’s employment arrangement.

The source describes the app as free and says its calculations run in the browser, but does not specify whether those arrangements or features may change. It gives no usage figures, user feedback, maintenance plan or comparison with a version built without an AI agent. The 24 co-authored commits and reported production totals are figures supplied by Meyer, rather than independently verified measurements.

Use, Feedback and Ongoing Review

Meyer’s account describes the website as public after his approval on October 2, but does not announce a further release date or a planned update. The immediate next step for readers interested in the service is to check the live app’s current features and terms directly, since the published account does not establish how the site will be maintained.

For the project’s broader claims, further information would include independent testing of the date calculations and privacy design, along with user numbers and details of ongoing support. Meyer’s account makes clear that he reviewed and approved the release; it does not say whether later changes will follow the same workflow or how responsibilities will be divided if the app is updated.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a person works an active phase and then has a passive phase, such as four years in each phase.

What does the app calculate?

Users enter the start date of an active or passive phase and choose a model from 1:1 to 5:5. According to Meyer, the app calculates the paired date and remaining working days, subtracting state public holidays and leave entered by the user.

What did the AI coding agent contribute?

Meyer says Claude Opus 5.5 co-authored all 24 commits and helped with engineering, testing, translations, audio assets and deployment. Meyer says he set direction, made product decisions, reviewed work and approved releases.

Does the source independently verify the app’s privacy?

No. Meyer says the app has no accounts, cookies or tracking and performs calculations in the browser, but the account does not include an independent privacy or security audit.

How long did development take?

Meyer says work began on September 28, 2026, and the public release was approved on October 2. That five-day timeline is his account of this project, not an independently tested estimate for similar software.

Source: ThorstenMeyerAI.com