# Loading, cache, and diagnostic reference Dynamic loading, priorities, overrides, cache, styles, and runtime observation. ## Choosing the loading level Use `wu.mount` for the complete lifecycle. `wu.prefetch` anticipates resources of registered applications, and `wu.use` loads components published through exports. `WuLoader` is an independent loader: it does not replace the core catalog, sandbox, or grants. Overrides and inspection tools belong to the host. A metric measures an observed interval; it does not guarantee the browser has finished painting. See [application loading](/docs/framework/loading/) and [diagnostics](/docs/framework/troubleshooting/) for the complete flow. ## wu.use Loads a component export declared by another application. `wu.use("app.component"): Promise` - **Parameters:** Exact app.component name; the provider manifest must declare wu.exports. - **Returns:** default export when present, otherwise the module namespace. - **Errors:** Missing app/export, traversal, invalid URL, or failed import reject. - **Permissions:** Host; a loaded component runs code in the consumer realm. - **Cleanup:** The renderer instance using the component manages its cleanup. ```js const ProductCard = await wu.use('catalog.ProductCard'); ``` Present at runtime but absent from the WuCore declaration. Does not convert components between frameworks. Reference: `src/core/wu-core.js`. ## wu.prefetchAll Requests preloading for all registered applications. `wu.prefetchAll(options?): Promise | (() => void)` - **Parameters:** Same trigger options as prefetch. - **Returns:** Immediate promise or cleanup for deferred triggers. - **Errors:** Preloading is a browser request; it does not confirm a renderer can mount. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Retain cleanup when choosing a deferred trigger. ```js await wu.prefetchAll({ on: 'immediate' }); ``` Reference: `src/core/wu-prefetch.js`. ## new WuLoader Creates a code and component loader with caching and in-flight deduplication. `new WuLoader({ maxCacheSize?, cacheTTL? }?): WuLoader` - **Parameters:** maxCacheSize limits entries (50 by default); cacheTTL is in milliseconds (1800000 by default). - **Returns:** Instance with loadApp, loadComponent, preload, isAvailable, and clearCache. - **Errors:** Constructing it neither registers apps nor executes lifecycle. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** loader.clearCache() releases cached entries. ```js import { WuLoader } from 'wu-framework'; const loader = new WuLoader({ maxCacheSize: 20, cacheTTL: 60000 }); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.loadApp Downloads entrypoint code text for the loading pipeline. `loader.loadApp(appUrl, manifest?): Promise` - **Parameters:** Base URL and manifest with optional entry. - **Returns:** Code string; does not execute mount or register the app. - **Errors:** Failed fetch, invalid response, or failed entry resolution reject. - **Permissions:** Host; subject to environment network access. - **Cleanup:** clearCache(base) discards cached reads for future requests. ```js const code = await loader.loadApp('/apps/catalog', { entry: 'entry.js' }); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.loadComponent Imports a component confined to an app base. `loader.loadComponent(appUrl, componentPath): Promise` - **Parameters:** Base and relative component path; no absolute URLs or traversal. - **Returns:** default export or imported namespace. - **Errors:** Path outside the base or failed import rejects. - **Permissions:** The module executes code in the same context; not scoped RPC. - **Cleanup:** Native import retains its module cache. ```js const card = await loader.loadComponent('/apps/catalog', 'components/card.js'); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.preload Anticipates code downloads for a list of applications. `loader.preload(appConfigs: WuAppConfig[]): Promise` - **Parameters:** Configuration array with name and url. - **Returns:** Promise completing preload traversal. - **Errors:** Preloading catches per-app failures; inspect availability before mounting. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Mounts no renderers; clearCache releases cached text. ```js await loader.preload([{ name: 'catalog', url: '/apps/catalog' }]); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.isAvailable Checks whether a URL responds successfully to HEAD. `loader.isAvailable(url): Promise` - **Parameters:** URL to check. - **Returns:** Boolean; network errors become false. - **Errors:** A server rejecting HEAD may return false even when GET works. - **Permissions:** Host network access. - **Cleanup:** Creates no subscriptions or persistent processes. ```js const available = await loader.isAvailable('/apps/catalog/entry.js'); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.clearCache Discards cached loader text and records. `loader.clearCache(pattern?): void` - **Parameters:** Optional pattern; without one, empties the loader cache. - **Returns:** void. - **Errors:** Does not invalidate the browser ESM cache. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js loader.clearCache('catalog'); ``` Reference: `src/core/wu-loader.js`. ## WuLoader.getStats Queries loader cache and in-flight imports. `loader.getStats(): object` - **Parameters:** No arguments. - **Returns:** Metrics object. - **Errors:** Does not represent apps' mounted state. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(loader.getStats()); ``` Reference: `src/core/wu-loader.js`. ## wu.override Configures a development URL override. `wu.override(name, url, options?): void` - **Parameters:** name and authorized URL; options.maxAge/path configure override persistence. - **Returns:** void - **Errors:** The system validates domains and configuration; an override is not automatic remounting. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Remove development overrides before sharing a session. ```js wu.override('catalog', 'http://localhost:4101'); ``` Reference: `src/core/wu-overrides.js`. ## wu.removeOverride Removes a URL override. `wu.removeOverride(name): void` - **Parameters:** Exact app name. - **Returns:** void - **Errors:** The system validates domains and configuration; an override is not automatic remounting. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Remove development overrides before sharing a session. ```js wu.removeOverride('catalog'); ``` Reference: `src/core/wu-overrides.js`. ## wu.getOverrides Queries active URL overrides. `wu.getOverrides(): Record` - **Parameters:** No arguments. - **Returns:** Record - **Errors:** The system validates domains and configuration; an override is not automatic remounting. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Remove development overrides before sharing a session. ```js console.log(wu.getOverrides()); ``` Reference: `src/core/wu-overrides.js`. ## wu.clearOverrides Removes all active overrides. `wu.clearOverrides(): void` - **Parameters:** No arguments. - **Returns:** void - **Errors:** The system validates domains and configuration; an override is not automatic remounting. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Remove development overrides before sharing a session. ```js wu.clearOverrides(); ``` Reference: `src/core/wu-overrides.js`. ## normalizeStyleMode Normalizes style configuration aliases. `normalizeStyleMode(mode): string | undefined` - **Parameters:** Mode string or undefined. - **Returns:** none→isolated; own-only→fully-isolated; other values pass through without validation. - **Errors:** Does not itself validate whether the manifest supports the mode. - **Permissions:** Pure function; grants no permissions. - **Cleanup:** Creates no subscriptions or persistent processes. ```js import { normalizeStyleMode } from 'wu-framework'; console.log(normalizeStyleMode('own-only')); ``` Reference: `src/core/wu-sandbox.js`. ## resolveDomOwnership Resolves explicit ownership and nativeShadow/framework aliases. `resolveDomOwnership(options?): "wu" | "app" | "light"` - **Parameters:** domOwnership takes precedence, then nativeShadow; Lit selects app by default. - **Returns:** Effective ownership. - **Errors:** Creates no Shadow DOM and does not validate whether a renderer implements its boundary. - **Permissions:** Configuration function; not a security control. - **Cleanup:** Creates no subscriptions or persistent processes. ```js import { resolveDomOwnership } from 'wu-framework'; console.log(resolveDomOwnership({ framework: 'lit' })); ``` Reference: `src/core/wu-sandbox.js`. ## wu.tagStyleAsApp Attributes a style/link sheet to an application for the CSS bridge. `wu.tagStyleAsApp(element, appName): void` - **Parameters:** style/link element and app name. - **Returns:** void. - **Errors:** Attribution does not replace manifest styleMode. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Remove the sheet when its owner ends. ```js const style = document.createElement('style'); style.textContent = ':host { color: var(--accent); }'; wu.tagStyleAsApp(style, 'catalog'); document.head.append(style); ``` Reference: `src/core/wu-core.js`. ## new WuCache Creates an LRU cache with TTL and optional storage. `new WuCache(options?): WuCache` - **Parameters:** maxSize in MB; maxItems; TTL in ms; persistent and storage memory/localStorage/sessionStorage. - **Returns:** Cache instance. - **Errors:** An oversized entry or operation limit may prevent storage. - **Permissions:** Host; do not use persistent storage as authorization. - **Cleanup:** cache.clear() releases entries and its persistent namespace. ```js import { WuCache } from 'wu-framework'; const cache = new WuCache({ maxSize: 2, maxItems: 20, defaultTTL: 60000, storage: 'memory' }); ``` Reference: `src/core/wu-cache.js`. ## WuCache.get Reads an unexpired entry and updates its LRU order. `cache.get(key): unknown | null` - **Parameters:** Entry key. - **Returns:** Saved value, or null for absence, expiration, or rate limit. - **Errors:** null does not distinguish a miss, expiration, and cooldown; check metrics. - **Permissions:** Access to the owned cache; store grants do not apply. - **Cleanup:** Creates no subscriptions or persistent processes. ```js const result = cache.get('catalog-result'); ``` An in-memory read returns the saved reference; it is not a separate snapshot like WuStore. Reference: `src/core/wu-cache.js`. ## WuCache.set Stores a value and applies space and expiration limits. `cache.set(key, value, ttl?): boolean` - **Parameters:** Key, value, and TTL in ms; ttl=0 uses defaultTTL because of || selection. - **Returns:** true if stored; false for size, error, or rate limit. - **Errors:** Catches failures and returns false; storage quota may limit persistence. - **Permissions:** Host; validate which data you persist. - **Cleanup:** delete(key) removes one entry; clear() removes all. ```js const cached = cache.set('catalog-result', { count: 12 }, 30000); ``` Reference: `src/core/wu-cache.js`. ## WuCache.delete Deletes an entry from memory and configured backing storage. `cache.delete(key): void` - **Parameters:** Exact key. - **Returns:** void - **Errors:** Persistence depends on storage availability and quota. - **Permissions:** Cache owner's authority. - **Cleanup:** Creates no subscriptions or persistent processes. ```js cache.delete('catalog-result'); ``` Reference: `src/core/wu-cache.js`. ## WuCache.clear Empties this instance's cache and configured storage. `cache.clear(): void` - **Parameters:** No arguments. - **Returns:** void - **Errors:** Persistence depends on storage availability and quota. - **Permissions:** Cache owner's authority. - **Cleanup:** Creates no subscriptions or persistent processes. ```js cache.clear(); ``` Reference: `src/core/wu-cache.js`. ## WuCache.getStats Queries hits, misses, evictions, sizes, and rate limiting. `cache.getStats(): object` - **Parameters:** No arguments. - **Returns:** object - **Errors:** Persistence depends on storage availability and quota. - **Permissions:** Cache owner's authority. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(cache.getStats()); ``` Reference: `src/core/wu-cache.js`. ## WuCache.getRateLimitStatus Queries whether operations are in cooldown and their quota. `cache.getRateLimitStatus(): object` - **Parameters:** No arguments. - **Returns:** object - **Errors:** Persistence depends on storage availability and quota. - **Permissions:** Cache owner's authority. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(cache.getRateLimitStatus()); ``` Reference: `src/core/wu-cache.js`. ## wu.getStats Summarizes core subsystem state and metrics. `wu.getStats(): object` - **Parameters:** No arguments. - **Returns:** Diagnostic object. - **Errors:** Does not replace a mount test or HTTP check. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(wu.getStats()); ``` Reference: `src/core/wu-core.js`. ## wu.getManifestDiagnostics Reads declarative dependency errors between apps. `wu.getManifestDiagnostics(): WuManifestImportDiagnostic[]` - **Parameters:** No arguments; depends on import preflight. - **Returns:** Diagnostic list by consumer/import/provider. - **Errors:** Does not automatically check every transitive bundle import. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.table(wu.getManifestDiagnostics()); ``` Reference: `src/core/wu-core.js`. ## wu.showInspector Opens the visual inspector loaded on demand. `wu.showInspector(): Promise<{ close(): void } | null>` - **Parameters:** No arguments. - **Returns:** close handle, or null if not opened. - **Errors:** Chunk loading or the DOM environment may prevent opening. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** close() or wu.hideInspector() removes the overlay. ```js const inspector = await wu.showInspector(); // Al cerrar tu herramienta: inspector?.close(); ``` Reference: `src/core/wu-core.js`. ## wu.hideInspector Closes the inspection overlay if present. `wu.hideInspector(): Promise` - **Parameters:** No arguments. - **Returns:** Closure promise. - **Errors:** Does not delete apps or store data. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Removes the diagnostic interface. ```js await wu.hideInspector(); ``` Reference: `src/core/wu-core.js`. ## wu.performance.startMeasure Marks the start of an app-specific or global duration. `wu.performance.startMeasure(name, appName?): void` - **Parameters:** Measurement name; appName defaults to global. - **Returns:** void. - **Errors:** Disabled configuration skips recording. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Finish with endMeasure using the same name/app pair. ```js wu.performance.startMeasure('load-catalog', 'catalog'); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.endMeasure Ends a duration and publishes it to metrics/User Timing when enabled. `wu.performance.endMeasure(name, appName?): number` - **Parameters:** Same name/app as startMeasure. - **Returns:** Milliseconds; 0 without a start mark. - **Errors:** Missing mark returns 0 rather than inventing a duration. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Removes this measurement's start mark. ```js const ms = wu.performance.endMeasure('load-catalog', 'catalog'); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.generateReport Aggregates instance performance statistics. `wu.performance.generateReport(): object` - **Parameters:** No arguments. - **Returns:** object - **Errors:** User Timing availability depends on the environment. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(wu.performance.generateReport()); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.getMetrics Reads metrics for a specific app. `wu.performance.getMetrics(appName): object | null` - **Parameters:** Exact name; null if no measurements exist. - **Returns:** object | null - **Errors:** User Timing availability depends on the environment. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(wu.performance.getMetrics('catalog')); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.getAllMetrics Reads metrics for every app registered with the measurer. `wu.performance.getAllMetrics(): object` - **Parameters:** No arguments. - **Returns:** object - **Errors:** User Timing availability depends on the environment. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(wu.performance.getAllMetrics()); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.clearMetrics Clears measurements for one or all apps. `wu.performance.clearMetrics(appName?): void` - **Parameters:** Optional name. - **Returns:** void - **Errors:** User Timing availability depends on the environment. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js wu.performance.clearMetrics('catalog'); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.getDevToolsEntries Reads User Timing entries emitted by WU. `wu.performance.getDevToolsEntries(options?): PerformanceEntry[]` - **Parameters:** type: mark, measure, or all; optional appName. - **Returns:** PerformanceEntry[] - **Errors:** User Timing availability depends on the environment. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.table(wu.performance.getDevToolsEntries({ type: 'measure', appName: 'catalog' })); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.observe Listens for new WU User Timing entries using PerformanceObserver. `wu.performance.observe(callback, { type? }?): () => void` - **Parameters:** PerformanceEntry callback; type defaults to measure. - **Returns:** Cleanup; an empty function if the observer is unavailable. - **Errors:** Missing PerformanceObserver does not throw; callback failures are logged. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** stop() disconnects the observer. ```js const stop = wu.performance.observe(entry => console.log(entry.duration), { type: 'measure' }); ``` Reference: `src/core/wu-performance.js`. ## wu.performance.configure Configures measurement, history limits, User Timing, and thresholds. `wu.performance.configure(options): void` - **Parameters:** enabled, maxMeasurements, devtoolsTimeline, and thresholds by name. - **Returns:** void. - **Errors:** Exceeding a threshold generates a warning; it does not cancel an operation. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js wu.performance.configure({ enabled: true, maxMeasurements: 100, devtoolsTimeline: true }); ``` Reference: `src/core/wu-performance.js`. ## wu.errorBoundary.register Adds a failure classification and recovery handler. `wu.errorBoundary.register(handler): void` - **Parameters:** name, canHandle(error), and handle(error,context). - **Returns:** void. - **Errors:** Throws if any member is missing; handlers are traversed in order. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Returns no unsubscribe; manage these extensions during the host lifecycle. ```js wu.errorBoundary.register({ name: 'catalog-error', canHandle: error => error.name === 'CatalogError', async handle(error) { return { recovered: false, action: 'none', message: error.message }; } }); ``` The default generic fallback may precede handlers added later. Check ordering before relying on this registration. Reference: `src/core/wu-error-boundary.js`. ## wu.errorBoundary.handle Classifies a failure and obtains a recovery decision. `wu.errorBoundary.handle(error, context?): Promise` - **Parameters:** Error and context; the core interprets some actions during mount. - **Returns:** Result with recovered and action, plus handler information. - **Errors:** An action name does not itself change URL, timeout, or permissions. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Recovery must release the failed attempt before retrying. ```js const recovery = await wu.errorBoundary.handle(new Error('Entry no disponible'), { appName: 'catalog', phase: 'mount' }); ``` Reference: `src/core/wu-error-boundary.js`. ## wu.errorBoundary.getErrorLog Reads recent errors retained by the boundary. `wu.errorBoundary.getErrorLog(limit?: number): object[]` - **Parameters:** limit defaults to 10. - **Returns:** Array of the latest entries. - **Errors:** Diagnostic memory, not a durable record. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.table(wu.errorBoundary.getErrorLog(5)); ``` Reference: `src/core/wu-error-boundary.js`. ## wu.errorBoundary.getStats Summarizes error count, handlers, and types. `wu.errorBoundary.getStats(): object` - **Parameters:** No arguments. - **Returns:** Object with totalErrors, handlers, errorsByType, and recentErrors. - **Errors:** Excludes failures that never passed through this boundary. - **Permissions:** Host API; not exposed by the scoped facade. - **Cleanup:** Creates no subscriptions or persistent processes. ```js console.log(wu.errorBoundary.getStats()); ``` Reference: `src/core/wu-error-boundary.js`. ## WuLoadingStrategy Creates loading strategies and starts idle processing. `new WuLoadingStrategy(core)` - **Parameters:** Core instance. - **Returns:** Coordinator with default strategies. - **Errors:** Propagates invalid-configuration errors; inspect asynchronous operation results. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** cleanup cancels idle callbacks and resolves the pending queue with null. ```js import { WuLoadingStrategy } from 'wu-framework'; const strategies = new WuLoadingStrategy(wu); strategies.cleanup(); ``` Reference: `src/core/wu-strategies.js`. ## strategies.register Registers or replaces a loading strategy. `strategies.register(name, strategy): void` - **Parameters:** Required strategy.load(appName,config); optional shouldPreload and priority. - **Returns:** void. - **Errors:** Throws if strategy.load is not a function. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js strategies.register('custom', { shouldPreload: false, priority: 'low', load: async (name, config) => { console.log(name, config); return null; }, }); ``` Reference: `src/core/wu-strategies.js`. ## strategies.load Executes the strategy selected by config.strategy. `strategies.load(appName, config): Promise` - **Parameters:** Name and config; lazy by default. - **Returns:** Result of the registered load function. - **Errors:** Unknown strategy logs a warning and falls back to lazy; load errors propagate. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js await strategies.load('card', { strategy: 'custom' }); ``` Reference: `src/core/wu-strategies.js`. ## strategies.preload Sequentially preloads applications whose strategies request it. `strategies.preload(apps): Promise` - **Parameters:** Configuration list with name and strategy. - **Returns:** Traversal promise; catches individual failures. - **Errors:** An individual failure is logged and allows continuation to the next app. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js await strategies.preload([{ name: 'card', strategy: 'custom' }]); ``` Reference: `src/core/wu-strategies.js`. ## strategies.getStats Queries registered strategies and idle queue size. `strategies.getStats(): object` - **Parameters:** No arguments. - **Returns:** {totalStrategies,strategies,idleQueueSize,isIdle}. - **Errors:** Local read without side effects. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js console.log(strategies.getStats()); ``` Reference: `src/core/wu-strategies.js`. ## strategies.cleanup Stops the idle queue and releases pending waits. `strategies.cleanup(): void` - **Parameters:** No arguments. - **Returns:** void. - **Errors:** Cleanup attempts to complete each wait even if one resolution fails. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** Cancels idle/timer and empties the queue; pending entries resolve null. ```js strategies.cleanup(); ``` Reference: `src/core/wu-strategies.js`. ## wu.sandbox.addStyles Inserts CSS into an existing sandbox. `wu.sandbox.addStyles(appName, css): void` - **Parameters:** Name and CSS string. - **Returns:** void. - **Errors:** Logs a warning and returns if the sandbox is missing. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js wu.sandbox.addStyles('card', ':host{display:block}'); ``` The sandbox property is core-managed. Do not call cleanupAll while applications are mounted: use wu.unmount to coordinate lifecycle. Reference: `src/core/wu-sandbox.js`. ## wu.sandbox.loadExternalStyles Inserts a stylesheet link into the sandbox. `wu.sandbox.loadExternalStyles(appName, href): void` - **Parameters:** Name and CSS URL. - **Returns:** void; does not await stylesheet load. - **Errors:** Missing sandbox produces a warning. Stylesheet network errors are not returned as a promise. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js wu.sandbox.loadExternalStyles('card', '/styles/card.css'); ``` The sandbox property is core-managed. Do not call cleanupAll while applications are mounted: use wu.unmount to coordinate lifecycle. Reference: `src/core/wu-sandbox.js`. ## wu.sandbox.getStyleStats Queries style-bridge statistics. `wu.sandbox.getStyleStats(): object | null` - **Parameters:** No arguments. - **Returns:** Statistics object or null. - **Errors:** Read without network operations. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js console.log(wu.sandbox.getStyleStats()); ``` The sandbox property is core-managed. Do not call cleanupAll while applications are mounted: use wu.unmount to coordinate lifecycle. Reference: `src/core/wu-sandbox.js`. ## wu.sandbox.reinjectStyles Reinjects styles according to the application's isolation mode. `wu.sandbox.reinjectStyles(appName): Promise` - **Parameters:** Registered sandbox name. - **Returns:** Promise. - **Errors:** Does nothing for a missing sandbox or isolated mode; other modes apply their style selection. - **Permissions:** Host administration API; not included in a microapp's scoped facade. - **Cleanup:** The runtime owner manages resources and their cleanup functions. ```js await wu.sandbox.reinjectStyles('card'); ``` The sandbox property is core-managed. Do not call cleanupAll while applications are mounted: use wu.unmount to coordinate lifecycle. Reference: `src/core/wu-sandbox.js`. In 4.0, an override without `allowedDomains` accepts only loopback hosts or the page’s hostname. Configure an explicit allowlist for another host. This restriction applies to programmatic overrides and those restored from cookies.