This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

You can read more about this in the [Advanced User Guide](../advanced/index.md).

## Details { #details }

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

{* ../../docs_src/sub_applications/tutorial001_py310.py hl[11, 14:16] *}

### Mount the sub-application { #mount-the-sub-application }

In your top-level application, `app`, mount the sub-application, `subapi`.

In this case, it will be mounted at the path `/subapi`:

{* ../../docs_src/sub_applications/tutorial001_py310.py hl[11, 19] *}

import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * An unbounded {@linkplain BlockingQueue blocking queue} that uses the same ordering rules as class
 * {@link PriorityQueue} and supplies blocking retrieval operations. While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion (causing {@code

```html
<a href="/items/42">
```

## Templates and static files { #templates-and-static-files }

You can also use `url_for()` inside of the template, and use it, for example, with the `StaticFiles` you mounted with the `name="static"`.

```jinja hl_lines="4"
{!../../docs_src/templates/templates/item.html!}
```

In this example, it would link to a CSS file at `static/styles.css` with:

```CSS hl_lines="4"

RUN Add-Content -Path C:\tools\msys64\.bashrc -Value 'alias bq=bq.cmd'

# Symlink a directory, to have it pretend be the T:\ drive.
# This drive letter is used by internal CI,
# and part of it is mounted to the container during the container's creation.
#
# While the mount argument (`-v host_path:container_path`) still requires
# `container_path` to be a legitimate C:\ path, in this case, 'C:\drive_t',

/// info | Very Technical Details

**Note**: this is a very technical detail that you probably can **just skip**.

---

The `APIRouter`s are not "mounted", they are not isolated from the rest of the application.

This is because we want to include their *path operations* in the OpenAPI schema and the user interfaces.

 * its greatest element, as determined by the queue's specified comparator. If no comparator is
 * given at creation time, the natural order of elements is used. If no maximum size is given at
 * creation time, the queue is unbounded.
 *
 * <p>Usage example:
 *
 * {@snippet :
 * MinMaxPriorityQueue<User> users = MinMaxPriorityQueue.orderedBy(userComparator)
 *     .maximumSize(1000)
 *     .create();
 * }
 *

 * its greatest element, as determined by the queue's specified comparator. If no comparator is
 * given at creation time, the natural order of elements is used. If no maximum size is given at
 * creation time, the queue is unbounded.
 *
 * <p>Usage example:
 *
 * {@snippet :
 * MinMaxPriorityQueue<User> users = MinMaxPriorityQueue.orderedBy(userComparator)
 *     .maximumSize(1000)
 *     .create();
 * }
 *

    // lowest respectively). If centerFloor is in allRequired, we will definitely find it. If not,
    // but centerFloor + 1 is, we'll definitely find that. The closest value to the true (unrounded)
    // center will be at either low or high.
    int low = requiredFrom;
    int high = requiredTo;
    while (high > low + 1) {
      int mid = (low + high) >>> 1;
      if (allRequired[mid] > centerFloor) {

        endpoint_ctx = (
            _extract_endpoint_context(dependant.call)
            if dependant.call
            else EndpointContext()
        )

        if dependant.path:
            # For mounted sub-apps, include the mount path prefix
            mount_path = request.scope.get("root_path", "").rstrip("/")
            endpoint_ctx["path"] = f"{request.method} {mount_path}{dependant.path}"