Once Props

Cache props client-side after the first resolution.

See also

Official Inertia.js docs: Once Props

What Are Once Props?

Once props are included in the initial page response, but the Inertia client caches their value after the first resolution. Subsequent visits reuse the cached value unless the prop is explicitly requested again.

Why Use Once Props?

Use once props for data that is expensive to compute and rarely changes, like feature flags, account settings, or reference data.

Backend Usage

from typing import Any

from litestar import get
from litestar_vite.inertia import once

@get("/dashboard", component="Dashboard")
async def dashboard() -> dict[str, Any]:
    return {
        "user": get_current_user(),
        "feature_flags": once("feature_flags", get_feature_flags),
        "settings": once("settings", lambda: Settings.for_user("alice")),
    }

Refreshing Once Props

The client will reuse cached values. To force a refresh, request the prop in a partial reload:

import { router } from "@inertiajs/react";

router.reload({ only: ["settings"] });

import { router } from "@inertiajs/vue3";

router.reload({ only: ["settings"] });

Deferred + Once

Combine deferred props with caching for “load later, remember forever”:

from typing import Any

from litestar import get
from litestar_vite.inertia import defer

@get("/reports", component="Reports")
async def reports() -> dict[str, Any]:
    return {
        "summary": defer("summary", build_summary).once(),
    }

Comparison of Prop Types

Type

Initial Load

Partial Reloads

Typical Use

once()

Included, cached

Reused unless requested

Rarely changing data

lazy()

Excluded

Included when requested

On-demand data

optional()

Excluded

Only when explicitly requested

WhenVisible / viewport loading

always()

Included

Included even when filtered

Critical auth/context

See Also