Squide Framework

Squide is a React modular application shell. Use only documented APIs.

Core Concepts

• Runtime: The FireflyRuntime instance is the backbone of a Squide application. Never instantiate directly — use initializeFirefly(), which wires up plugins, logging, and the module lifecycle.
• Modular Registration: Modules register routes, navigation items, and MSW handlers via a registration function, assembled by the host at bootstrapping.
• Public vs Protected Routes: Routes default to protected (rendered under ProtectedRoutes). Use registerPublicRoute() for public routes. Protected routes fetch both public and protected global data.
• Deferred Registrations: Navigation items dependent on remote data or feature flags use two-phase registration — return a function from the registration to defer items to a second phase.

Key Patterns

Host Application Setup

// host/src/index.tsx
import { createRoot } from "react-dom/client";
import { FireflyProvider, initializeFirefly } from "@squide/firefly";
import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
import { App } from "./App.tsx";
import { registerHost } from "./register.tsx";

const runtime = initializeFirefly({
    localModules: [registerHost]
});

const queryClient = new QueryClient();
const root = createRoot(document.getElementById("root")!);

root.render(
    <FireflyProvider runtime={runtime}>
        <QueryClientProvider client={queryClient}>
            <App />
        </QueryClientProvider>
    </FireflyProvider>
);

// host/src/App.tsx
import { AppRouter, useIsBootstrapping } from "@squide/firefly";
import { createBrowserRouter, Outlet } from "react-router";
import { RouterProvider } from "react-router/dom";

function BootstrappingRoute() {
    if (useIsBootstrapping()) {
        return <div>Loading...</div>;
    }
    return <Outlet />;
}

export function App() {
    return (
        <AppRouter>
            {({ rootRoute, registeredRoutes, routerProps, routerProviderProps }) => (
                <RouterProvider
                    router={createBrowserRouter([{
                        element: rootRoute,
                        children: [{
                            element: <BootstrappingRoute />,
                            children: registeredRoutes
                        }]
                    }], routerProps)}
                    {...routerProviderProps}
                />
            )}
        </AppRouter>
    );
}

// host/src/register.tsx
import { PublicRoutes, ProtectedRoutes, type ModuleRegisterFunction, type FireflyRuntime } from "@squide/firefly";
import { RootLayout } from "./RootLayout.tsx";

export const registerHost: ModuleRegisterFunction<FireflyRuntime> = runtime => {
    runtime.registerRoute({
        element: <RootLayout />,
        children: [PublicRoutes, ProtectedRoutes]
    }, { hoist: true });

    // HomePage and NotFoundPage are local page components
    runtime.registerRoute({ index: true, element: <HomePage /> });
    runtime.registerPublicRoute({ path: "*", element: <NotFoundPage /> });
};

Navigation Rendering

Important: RenderItemFunction signature is (item, key, index, level) => ReactNode and RenderSectionFunction is (elements, key, index, level) => ReactNode. These signatures are fixed and do not accept custom context parameters, but there could be fewer arguments. Use closures to access external values.

Important: spread additionalProps whole, never key by key. A value the renderer must read instead of forward belongs in $context, surfaced as context. Never destructure a key out of additionalProps to keep it off the element — that is what $context is for. This $context is per-item data for the layout: it is not the module registration context and not React context. It was named $meta in @squide/firefly 18.2.0-19.0.0 (@squide/react-router 9.1.0-10.0.0).

import { Link, Outlet } from "react-router";
import {
    useNavigationItems, useRenderedNavigationItems, isNavigationLink,
    type RenderItemFunction, type RenderSectionFunction
} from "@squide/firefly";

// Signature: (item, key, index, level) => ReactNode
const renderItem: RenderItemFunction = (item, key, index, level) => {
    if (!isNavigationLink(item)) return null;
    const { label, linkProps, additionalProps } = item;
    return (
        <li key={key}>
            <Link {...linkProps} {...additionalProps}>{label}</Link>
        </li>
    );
};

// Signature: (elements, key, index, level) => ReactNode
const renderSection: RenderSectionFunction = (elements, key, index, level) => (
    <ul key={key}>{elements}</ul>
);

export function RootLayout() {
    const navigationItems = useNavigationItems();
    const navigationElements = useRenderedNavigationItems(navigationItems, renderItem, renderSection);
    return (
        <>
            <nav>{navigationElements}</nav>
            <Outlet />
        </>
    );
}

Global Data Fetching

// Protected data
import { useProtectedDataQueries, useIsBootstrapping, AppRouter } from "@squide/firefly";

// ApiError and isApiError are app-specific; define them to match your API's error shape
function BootstrappingRoute() {
    const [session] = useProtectedDataQueries([{
        queryKey: ["/api/session"],
        queryFn: async () => {
            const response = await fetch("/api/session");
            if (!response.ok) throw new ApiError(response.status);
            return response.json();
        }
    }], error => isApiError(error) && error.status === 401);

    if (useIsBootstrapping()) return <div>Loading...</div>;

    return (
        <SessionContext.Provider value={session}>
            <Outlet />
        </SessionContext.Provider>
    );
}

// In App component, set waitForProtectedData
<AppRouter waitForProtectedData>...</AppRouter>

// Public data
const [data] = usePublicDataQueries([{ queryKey: [...], queryFn: ... }]);
<AppRouter waitForPublicData>...</AppRouter>

Deferred Navigation Items

export const register: ModuleRegisterFunction<FireflyRuntime, unknown, DeferredRegistrationData> = runtime => {
    // Always register routes
    runtime.registerRoute({ path: "/feature", element: <FeaturePage /> });

    // Return function for deferred navigation items
    return (deferredRuntime, { userData }) => {
        if (userData.isAdmin && deferredRuntime.getFeatureFlag("enable-feature")) {
            deferredRuntime.registerNavigationItem({
                $id: "feature",
                $label: "Feature",
                to: "/feature"
            });
        }
    };
};

// Execute deferred registrations in BootstrappingRoute.
// Wrap in useMemo — without it, a new object reference each render re-triggers all deferred registrations.
const data = useMemo(() => ({ userData }), [userData]);
useDeferredRegistrations(data);

Important: a deferred registration function runs again on every update (feature flag change or new data). Squide discards everything the previous run registered before replaying, so each run must register the full set of items it wants rendered — never the difference since the last run. Squide only discards what it owns: a plugin exposing its own registry to modules must clear it via the optional Plugin.onDeferredRegistrationScopeStarted hook, and a registry that isn't owned by a plugin via runtime.registerDeferredRegistrationScopeStartedListener — the same hook, same options, same guarantees (see references/runtime-api.md).

See also: For error boundaries, authentication, testing patterns, and advanced navigation (multi-level, modular tabs, dynamic segments, active state), see references/patterns.md. For MSW setup, LaunchDarkly, Honeycomb, i18next, and Storybook integrations, see references/integrations.md. For plugin authoring and the full runtime API, see references/runtime-api.md.

Reference Guide

For detailed API documentation beyond the patterns above, consult the reference files:

• references/getting-started.md — What Squide is and the problems it solves, modular design principles, scaffolding a host application and a local module from scratch (packages, files, Rsbuild config, template)
• references/runtime-api.md — initializeFirefly options, route registration options (hoist, parentPath, parentId), route properties, navigation item properties, navigation registration options (menuId, sectionId), deferred registration scope started listeners, and request handler registration
• references/hooks-api.md — All Squide hooks: data fetching (usePublicDataQueries, useProtectedDataQueries), navigation (including the render props types and canRender()), event bus, environment variables, feature flags, logging, routing, and i18next hooks
• references/components.md — AppRouter props (including strictMode and registration validation), FireflyProvider, helper functions (isNavigationLink, resolveRouteSegments, mergeDeferredRegistrations)
• references/patterns.md — Local module setup, deferred registration update runs and pending sections, error boundaries, authentication, modular tabs, MSW request handlers, testing (including createDeferredRegistrationsRunner), and other common patterns
• references/integrations.md — LaunchDarkly (plugin, utilities, testing clients), Honeycomb, i18next, and Storybook integration details

Common Pitfalls

Skill maintainers: Before updating this skill, read [ODR-0008](../../agent-docs/odr/0008-skill-body-reference-split.md). The body must stay under ~250 lines; new API content goes in the appropriate references/ file.

When working with Squide APIs, watch for these common mistakes:

1. useRenderedNavigationItems function signatures: Must always be (item, key, index, level) and (elements, key, index, level). These do NOT accept custom context parameters. If external values are needed (route params, location, etc.), use closures or React hooks - never suggest adding parameters to these functions.

1. Active state styling: Use React Router's NavLink and its isActive argument provided to the className/style render functions (for example, className={({ isActive }) => ... }). Do not suggest passing location/pathname as a context parameter.

1. Dynamic route segments: Use the resolveRouteSegments helper with closures to capture values like userId. Example pattern: create a higher-order function that returns a RenderItemFunction.

1. Deferred registration runtime parameter: The deferred registration callback receives deferredRuntime as its first argument — this is NOT the same runtime from the outer registration function. Always use deferredRuntime inside the deferred callback for registerNavigationItem, getFeatureFlag, etc.