# FAST Component Discovery
FAST reads each package's `customElements` manifest as its component inventory
and loads converted `*.template-webui.html` files for those declarations.
It explicitly opts into package metadata loading. Other discovery plugins do
not incur this metadata work unless they independently opt in. Package-level
script ownership analysis is performed only for FAST manifest declarations.
## Package assets
A single-component package can export `./template-webui.html` and optionally
`./styles.css`. Paths are relative to the package root, including symlinked
packages. Direct strings and conditional objects preserve declaration order
with `browser`, `import`, and `default` as active conditions. An active `null`
blocks the export. Export arrays are not supported. The selected template path
must end in `.template-webui.html`. Raw `.template.html` files and their export
are never selected.
The manifest supplies the inventory and names; these exports are only optional
asset-location hints.
Without a package-level template export, FAST uses CEM module-relative
template/style lookup and virtual-module fallbacks, then checks parent
directories within the package when needed. This supports multi-component
packages with templates beside their JavaScript modules.
CEM module paths may also be bare npm specifiers. Scoped package subpaths and
unscoped packages declared through `dependencies`, `peerDependencies`, or
`optionalDependencies` resolve from `node_modules`, including package export
maps. The current package name is also recognized for self-references. Prefix
an ambiguous package-relative path with `./`; existing paths backed by local
modules or templates remain package-relative. Asset lookup stays within the
resolved package and honors its explicit converted template and style exports.
An explicit missing or invalid asset is an error, not a reason to select a
different template. Packages shipping only `.template.html` must also provide
the converted `.template-webui.html` variant for this discovery plugin.
## Default fallback
FAST also includes ordinary `<component-name>.html` files not declared in the
manifest, using default filename, CSS, and script-ownership rules. This fallback
also works when the manifest is absent or contains no component declarations.
Manifest declarations win name conflicts. Generated `.template.html` and
`.template-webui.html` assets are not accidentally registered as default names.
Malformed declared metadata still reports an error.
Ordinary `<component-name>.html` files in the application folder remain supported
under both FAST parser versions, including sibling CSS and authored scripts.
See the [discovery crate README](../../../README.md) for shared package lookup
and scope behavior.