Three apps on one handlebar: how Fahrklar came to be

Fahrklar exists because on a three-week motorcycle tour, three separate apps — one navigation app, two weather apps — never talked to each other. Fahrklar closes exactly that gap: route planning that checks the weather for every stretch of road at the time you'll actually arrive there, instead of just showing one forecast for the destination.

Before the first line of code, there was a tour: three weeks on a motorcycle, with preparation starting weeks earlier at a desk.

I planned it in Google Maps, because that's the fastest way to drop waypoints — except no motorcycle navigation app reads that format. So every leg had to be exported, converted into a format the navigation app understood, imported there, and checked to see whether the waypoints still matched or had shifted along the way. For three weeks of legs, that added up to a lot of evenings.

On the road, three apps ran side by side on the handlebar: one navigation app for the winding roads, plus two weather apps — because the two kept contradicting each other and neither felt trustworthy alone. Every morning, the same back-and-forth: open the weather app, guess whether the rain front at 2pm would sit over the pass or the valley, switch back to navigation, check the route, check the weather again. And at the next break, start over.

The annoying part wasn't that any single app was bad — each did its job well. The annoying part was the gap between them: none knew what the others knew. The weather apps didn't know the route. The navigation app didn't know the weather. And the route itself had to travel through several file formats before it was even rideable.

Somewhere on that tour, I started writing it down. That became Fahrklar.

What Fahrklar does differently, technically

The core idea is simple: a weather forecast for the destination says nothing about kilometer 84. Over a 300-kilometer route, the start, middle, and end can each sit in a different weather system — and you reach them at three different times.

That's why Fahrklar splits the route into segments and fetches the forecast for each segment at the time you're expected to arrive there. Not the weather now, but the weather then and there. Start-time optimization builds on this: it runs every possible start time in a window of three hours before and after your preferred time and suggests the driest one. How much risk is acceptable is up to you, from "completely dry" to "light rain is fine".

Break planning relies on the same calculation: if a rain phase sits on the route regardless, Fahrklar suggests the break exactly there — with a café or gas station nearby, and a check on whether it's actually open by the time you'd arrive.

And the file-format problem from those planning evenings: Fahrklar reads GPX, KML, and KMZ directly, no conversion needed, and exports as a GPX track or as a guided route-planner tour or calendar entry in ICS format. The desk evenings are gone.

What's been added since

It started with the motorcycle. Today Fahrklar covers four vehicle types: motorcycle, convertible, bicycle, and e-bike, each with its own speed and route calculation. Convertible uses the motorcycle profile, since both travel similarly on winding country roads. Bicycle and e-bike calculate differently, because two hours of rain on a bike is a different thing than two hours under a hardtop.

The most recent addition is EV charging stations: drivers going electric now see the nearest charging stations at the start, destination, and every planned break. One click adopts the station as a waypoint, and the route recalculates. That wasn't on the original list, but it follows the same logic as everything else: anyone planning a break wants to know what's at the break. For EV drivers, that's the charging station — the feature is available from the Plus plan.

On top of that: live rain radar on the planning map, GPS tracking during the ride with an alert if you drift off route, elevation profile, route planning across all of Europe, and four languages. Technically, Fahrklar is a Progressive Web App: it runs in the browser, can be added to your home screen like an app, and also works offline.

How I built this as a solo developer

I built Fahrklar alone, using an AI model as a tool. That's no secret today; a large share of the code being written now comes out of a language model. The problem isn't that the code gets written — the problem is that it gets written faster than a human can review it.

For that, I use Code Guardian by Provimedia. In short, it sits between the model and the software. Before any change happens, it goes through a plan mode: first read-only exploration, then every open decision asked as a separate question, then a plan, then approval — only then write access. After the change, an audit runs over the entire diff, and every finding needs evidence from an executed check. "I read the code, it looks right" doesn't count.

On top of that, there are gates that stop critical steps instead of flagging them afterward: before a deployment, before a database migration, before a new dependency, before any statement about data. And cold reviewers: subagents that read a finished plan or diff without the conversation context and try to poke holes in it.

What that buys you shows up exactly where it's annoying: a push to the production branch without a green pipeline doesn't go through. A migration with no rollback path gets stopped. A number in a report needs the command that produced it. For a product with user accounts, payments, and location data, that's the whole point: speed comes from the model, reliability comes from the process.

Where Fahrklar stands today

Fahrklar runs at fahrklar.net, hosted in Germany, with no tracking and no ads. The Basic plan is free forever.

The paid plans are one-time payments for 30 days, with no auto-renewal — a deliberate choice: no product that quietly keeps renewing until someone cancels.

If you ride a motorcycle, drive a convertible, or ride a bike, give it a try. And if you're a developer working with AI and want to know exactly how that review process works, just send a message.