Before your app goes online, fline builds it: it gets the add-ons your app uses, runs your app's own build step and packs the result. This page explains what fline does by itself when that build fails, what you see while it happens, and what to do if the second try fails too.

What fline does by itself

fline writes the instructions for building your app itself, so you never have to. Sometimes its first version isn't right: it misses a step your app needs, or a download doesn't work. When the build stops for a reason like that, fline:

reads the lines where the build said what went wrong,
changes its own build instructions to fix that, and
builds your app again.

You don't have to ask, and Claude Code doesn't have to send your project again. fline does this once for each version of your app. Whether the second try works depends on what went wrong, so we can't promise it will.

Which failures it tries again

fline tries again when:

its own build instructions had a mistake,
your app's build step stopped with an error,
the finished app came out too big, or
something your app needs couldn't be downloaded.

Other failures stop the launch the first time, for example a build that runs longer than 15 minutes.

fline changes only its own build instructions, never your app's code. If the build stopped because of a mistake in your app's own code, the second try usually fails the same way, and Claude Code is the one to fix it.

What you see

Your fline dashboard shows "preparing build" again, then "building".
You may get a second email that says "Building" and your project's name.
Claude Code sees the same thing, and fline tells it to keep waiting.

If the second try fails too

The launch stops, and your dashboard and an email say what went wrong, as with any failed build. The message is the one from the second build. If fline couldn't write new build instructions at all, the message is the first build's.

Then follow The build failed: copy the problem for Claude Code from your dashboard, paste it in, and add:

Paste this into Claude Code

fline tried to build my app twice and it failed. Look at what went wrong on fline and try a fix.

What fline sends and keeps

To change its build instructions, fline sends the error lines from the failed build, and the build instructions it wrote, to the same AI model that reads parts of your code, made by OpenAI. The passwords and keys you save on fline never go into the build, so they aren't in those lines. Error lines can quote parts of your own files, the way an error message does.

fline also keeps a short record of each failed build: its error lines and the kinds of tools your project uses, like Next.js or Python. It's there so that failures which happen again and again across apps can be found and fixed for everyone. Nothing deletes these records yet. The privacy page has the details.

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