Detection

af init reads what is already in the repository and writes a manifest from it. Every value it writes came from a file: a package manifest, a Dockerfile, a compose file, a dependency list.

af init

It does not ask you to describe your application. Your application already describes itself, in the files you use to run it.

What it reads

Source	What it yields
package.json, go.mod, requirements.txt, Gemfile	Language, version, start command, scripts
Dockerfile, docker-compose.yml, Procfile	Services, ports, commands, dependencies
Dependency lists	Third party APIs, which become egress rules
Migration directories	The migrate command
Cron and schedule files	Scheduled services

The dependency list is the one that surprises people. A stripe dependency produces an egress rule for api.stripe.com in sandbox mode, a resend dependency produces one for api.resend.com in capture mode, and a sentry dependency produces a block with a sentence saying why.

What it says it is unsure about

Assumed
  database.present                         yes
  service.web.port                         3000

  These were not detected with confidence. Check them before you commit.

A guess presented as a fact is worse than a question. Anything inferred rather than read is listed under Assumed, so the things worth a second look are the short list rather than the whole file.

When it cannot decide

AF-DET-001 More than one service could be the web service: web, api, frontend.

Rather than picking one, it says which candidates it found. Editing the manifest once is faster than discovering next week that previews have been building the wrong thing.

Re-running it

af init writes the manifest once and does not regenerate it. Nothing rewrites it behind your back, so an edit you make survives, and a later af init on a repository that already has one tells you it is there rather than replacing it.

If the repository has changed enough to want a fresh look, delete the manifest and run it again, or read the new one against the old with git diff.

Related: the manifest reference, building.