Sixteen Versions In Five Days: My AI Coding Agent Build

🔍 Read the full analysis: Sixteen Versions In Five Days: My AI Coding Agent Build on ThorstenMeyerAI.com

Buying for a business?Offer from Amazon

Get business pricing on monitors, keyboards and dev gear

• Business-only prices and quantity discounts
• Tax-exempt purchasing
• Multiple users, one account, clear invoices

Create a free Business account →Free to register

As an affiliate, we earn on qualifying purchases.Hide

Developer Thorsten Meyer says he built Altersteilzeit, a free web app that counts down working days during German partial retirement, in five days with Claude Opus 5.5 acting as a coding agent. What began on September 28, 2026, as a request for a short animated film had become a public website by October 2, with a daily countdown, a film, 19 3D games and narration in multiple languages, according to Meyer’s account published October 13.

Meyer describes the app as a tool for people using the block model of Altersteilzeit, a German partial-retirement arrangement in which a period of regular work is followed by an equally long release from work. Users enter the start date of either phase and choose a model, from 1:1 to 5:5. The app calculates the corresponding dates and remaining working days, accounting for weekdays, public holidays in the user’s German federal state and entered leave.

The finished site combines that calculation with a daily dashboard showing a countdown, progress ring, daily saying and upcoming milestones. Meyer says it also offers calendar exports, a printable calendar, a bridge-day finder, badges and a team countdown. The film presents the user’s working and passive phases as two visual acts, while the games turn years and calendar periods into playable levels. The article refers to 19 games overall, although its day-by-day account says the game expanded through successive additions.

Meyer reports that the project went through 16 versions and 24 commits, each co-authored by Claude Opus 5.5. He says the agent wrote code, tests and documentation, helped produce translations and audio, and deployed the site. Meyer says he set the concept and tone, made choices about voices and content, reviewed the work and approved releases. The account describes a collaboration, not an independently audited measure of what the agent completed without human input.

Where the Agent’s Work Ended

The account offers a concrete example of how an AI coding agent can contribute to a small, public-facing software project across engineering, content and production. Meyer’s reported output goes beyond a code prototype: the app includes date calculations, interactive browser games, multiple languages, recorded narration and legal pages. That breadth helps explain why the project may interest developers considering agent-assisted workflows.

It also draws a distinction often blurred in claims about automated software development: the agent did substantial implementation work, while the developer retained direction and approval. Meyer says he decided what the experience should feel like, chose voices and dialects, set the contact details and signed off on releases. The project therefore illustrates a workflow in which an agent handles many production tasks but a person remains responsible for product choices and publication.

For users, the app’s stated privacy design is relevant because it handles personal dates. Meyer says calculations happen in the browser, with no accounts, cookies or tracking, and that dates in shared links are placed after the address’s “#” fragment. Those are the developer’s descriptions; the article does not provide an independent privacy or security review.

From Film to Countdown App

The project began with a narrow request: on Monday, September 28, Meyer asked for a short animated film about the work and release phases of an Altersteilzeit arrangement. The block model is especially suited to a countdown because the active phase, when a person continues working, is followed by a passive phase away from work. Meyer says he wanted to make that wait more engaging than a plain date calculation.

His chronology describes a rapid expansion over five days. On the first day, the work moved from the film to date entry, working-day calculations and game prototypes, and the site went online. The second day added seven languages, the dashboard and more games. The third brought further games and features, along with a fix after a mobile scrolling problem on iPhone. A narrator and sound effects followed on day four; Meyer says he approved the result on day five, when five German dialects were also added.

The games use calendar time as their organizing idea: for example, Meyer says maze columns represent months and cells represent weeks, while another game treats emails as working days. He also says the project uses single-file HTML that can run offline and was supported by 15 test scripts. Those technical details and totals come from the project author’s account.

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

— Thorsten Meyer, project author

What the Account Does Not Verify

The source is Meyer’s first-person account, rather than an independent technical review. It does not include a third-party audit of the code, test coverage, privacy claims, accessibility or the app’s date calculations. It also gives no user numbers, usage data or external evaluation of whether the site works as described across devices and regions.

Some production figures need to be read as reported totals, not independently checked results. Meyer lists 12 languages for the narrator and production work, while describing the launch features as seven languages plus five German dialects. Those descriptions may refer to different language and dialect groupings, but the article does not fully explain how they are counted. The chronology also says that the game grew through additions while giving both an overall total of 19 and a day-three addition of 12 more; the exact counting of prototypes, modes and games is not clarified.

The account does not state how much time Meyer spent directing, reviewing or correcting the agent, or provide a comparison with a human-only build. It also does not identify a formal release date beyond saying the site was online by October 2. The reported speed and scope should therefore be understood as the author’s description of this project, not a general benchmark for AI coding agents.

The App After Its Five-Day Build

Meyer’s account ends with his approval of the sound effects and the addition of German dialects on the fifth day. It does not announce a future feature, a new release schedule or a planned evaluation. The immediate next step for readers interested in the project is to inspect the public app and its own published details, rather than treating the build narrative as independent verification.

Further information that would help assess the project includes a technical description of the date and holiday calculations, an independent review of the privacy design, and a clearer breakdown of how the language, dialect, game and mode totals are counted. Until those details are available, the confirmed development is the publication of Meyer’s account and his report that the app was built and put online during the five-day period.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a person works during an active phase and is later released from work for a matching period.

What does the app calculate?

Users enter the start date of one phase and select a model. The app is described as calculating the other date and the remaining working days, subtracting public holidays for the selected German federal state and any leave entered.

What did the AI coding agent do?

Meyer says Claude Opus 5.5 helped implement features, write and run tests, produce translations and audio, and handle deployment. He says he set the direction, made product decisions, reviewed results and approved releases.

How long did the build take?

Meyer says work began on September 28, 2026, and the site was online by October 2. He reports 16 versions and 24 commits during that period.

Have the app’s privacy and performance claims been independently checked?

The supplied account does not include an independent audit. Claims about browser-only calculations, no tracking and the reported technical output are attributed to Meyer.

Source: ThorstenMeyerAI.com