`OobHost`¶

Stable out-of-band swap root with a reserved id.


Import	`from hedron import OobHost`
Distribution	`hedron`
Backend activity	No
Normal render mode	`RenderMode.FRAGMENT`

Live demo¶

DemoCode

Docs simulation — not a running Hedron server. Interactive demos show a “Simulated HTMX” trace when applicable.

Draft profilePrimary region waiting for save.

OOB host#statusStable swap root

Minimal runnable app.py that reproduces this demo (real Hedron, not the docs simulator):

app.py

import os

from hedron import (
    Hedron,
    InteractionResult,
    OobHost,
    OobUpdate,
    Page,
    Stack,
    html,
)
from hedron_core.interaction import InteractionPolicy

app = Hedron(
    title="OobHost demo",
    security="standard",
    explorer="off",
    session_secret=os.environ.get("HEDRON_SESSION_SECRET", "dev-only"),
)

main = app.region("oob-primary")
host = app.region("demo-oob-host")


def primary(*, draft: bool = True):
    return html.div(
        html.strong("Draft profile" if draft else "Profile saved"),
        html.span("Primary region waiting for save." if draft else "Primary region updated."),
        id=main.id,
    )


@app.page("/")
def home() -> Page:
    return Page(
        Stack(
            primary(draft=True),
            OobHost(
                html.span("OOB host"),
                html.span(
                    html.strong("#status"),
                    html.small("Stable swap root"),
                    class_="hedron-sim-oob-label",
                ),
                id=host.id,
            ),
            html.button(
                "Save",
                type="button",
                **{
                    "hx-post": "/profile",
                    "hx-target": main.selector,
                    "hx-swap": "outerHTML",
                },
            ),
        ),
        title="OobHost",
    )


@app.action("/profile", method="POST", fragment_regions=(main, host))
def save() -> InteractionResult:
    return InteractionResult(
        content=primary(draft=False),
        region_id=main.id,
        oob=(
            OobUpdate(
                content=OobHost(
                    html.span("Saved"),
                    html.span(
                        html.strong("#status"),
                        html.small("Out-of-band update"),
                        class_="hedron-sim-oob-label",
                    ),
                    id=host.id,
                ),
                element_id=host.id,
            ),
        ),
        policy=InteractionPolicy(declared_regions=(main, host)),
    )

Basic use¶

from hedron import OobHost, Toast
component = OobHost(Toast('Saved'), id='toast-host')

Compose under Page for full documents, or return from a fragment route for HTMX swaps.

How it works¶

OobHost reserves a predictable DOM root for oob_swap updates. Pair with authorize_oob_update and reserved-id rules so fragments cannot target arbitrary selectors.

This component can initiate or represent a backend interaction. The live documentation intercepts that interaction with JavaScript and shows the same pending, success, or replacement states without making a real request. In an application, keep the URL, authorization, validation, and returned fragment on the server; JavaScript is only progressive enhancement.

Constructor and parameters¶

OobHost(*nodes, *, id, tag='div', class_=None)

Parameter	Type	Meaning
`id`	`str`	Required stable element id for OOB targeting.
`tag`	`str`	Host element tag (default div).
`class_`	`str \| None`	Optional CSS classes.

Composition and backend behavior¶

Keep OobHost at the smallest semantic boundary. Fragment routes should return only the replaced region and preserve stable target IDs across success, validation, empty, loading, and error responses.

Mutating flows must use POST, validate CSRF, authorize on the server, re-validate typed input, and return a bounded fragment. GET remains safe and repeatable; native submit should still work without HTMX.

Accessibility¶

Give each OOB host a unique page-local id and keep toast/status regions outside MainPanel when they must survive panel swaps.

Security¶

Escaping and SafeUrl / TrustedHtml are framework concerns; authorization and data exposure remain application code. Redact secrets before rendering.

Common mistakes¶

Do not reuse an OobHost id for ordinary fragment regions.
Do not copy docs-preview JavaScript into an application server.

Testing¶

from hedron import RenderMode, render

result = render(component, mode=RenderMode.FRAGMENT)
assert result.html
assert not result.diagnostics

All component demos · Built-in API · Testing

OobHost¶