Barrel rules

Which barrel setting applies to each plugin, when a plugin gets no barrel, and what each index.ts re-exports.

Which barrel setting applies

The Barrel plugin runs after every other plugin, so each barrel sees the final set of files. For each plugin, Kubb reads its output.barrel first, then the root output.barrel, then false.

The root output.barrel accepts only type and is always flat. It has no nested or namespace field.
Passing your own output to a plugin replaces its default barrel: { type: 'named' }, so the plugin falls back to the root setting.

Root `output.barrel`	Plugin `output.barrel`	Plugin barrels	Root barrel
`false` (default)	Plugin default `{ type: 'named' }`	Yes	No
`false` (default)	Unset, because your own `output` replaced the default, as in `pluginTs({ output: { path: 'types' } })`	No	No
`{ type }`	Unset	Yes, with the root `type`	Yes
`{ type }`	`{ type, … }`	Yes, with the plugin setting	Yes
`{ type }`	`false`	No	Yes, without this plugin's files

When a plugin gets no barrel

Case	Result
`output.mode: 'file'`	The root barrel re-exports the single file directly.
The plugin writes to the output root, with no own `output.path`	The root barrel picks up its files.
`output.path` resolves outside the root `output.path`	With a directory barrel, the build fails with `KUBB_PATH_TRAVERSAL`. With `barrel: false` or `mode: 'file'`, Kubb does not check it.

What goes into a barrel

Every .ts, .tsx, .js, and .jsx file below the folder, sorted by name. Other index.ts files are not re-exported as leaves.
The barrel file is always index.ts.
With type: 'named', a file without sources is re-exported whole.
With type: 'all', a file whose sources are all marked as not indexable is left out.
With nested, a subfolder barrel is always chained with export *, also for type: 'named', because the child barrel already lists the names.

A plugin's barrels get its output.banner and output.footer only when the plugin sets them. They never get the default "Generated by Kubb" notice, and the root barrel gets neither.

Namespaces for tag groups

namespace exposes each immediate subfolder as a named namespace, next to its standalone exports. Combine it with tag groups to export each group as a named service.

A namespace takes the PascalCase folder name. A name that does not start with a letter gets an _ prefix, and a name with no letters or digits becomes _.
An enabled root barrel forwards the namespaces too.
Editors can offer auto-imports for these namespaces when the generated files belong to the TypeScript project.

For tag-grouped fetch clients, name the service folders with group.name. Leave the fetch sdk option unset so React Query can import the standalone operation functions. For a pet tag, the operations land in src/gen/client/petService/. Both calling styles, PetService.getPetById() and getPetById(), work next to the generated hooks and query options.

All Barrel guides