Aurelia 2 Beta 27: 13 Features and a Glimpse of What's Next

Beta 27 is a landmark release. With 13 new features, 16 bug fixes, and foundational refactoring for SSR and AOT compilation, this update touches nearly every corner of Aurelia 2. Whether you’re managing complex state, building virtualized lists, or waiting for server-side rendering support, there’s something substantial here for you.

SSR and AOT on the Horizon

Fred ( @fkleuver ) has been laying the groundwork for server-side rendering and ahead-of-time compilation. Beta 27 includes several internal refactors that pave the way for these features: AST nodes converted to interfaces for easier serialization ( #2309 ), numeric instruction discriminants for smaller payloads ( #2329 ), and a simplified template compiler ( #2310 ).

SSR, SSG, and AOT compilation are actively being wired up and will be ready for testing shortly. Initial versions will be based on Vite. Alongside this, a new VS Code extension is coming with typechecking, syntax highlighting, refactorings, and more.

State Management

Multiple Named and Keyed Stores

You can now register and manage multiple independent stores identified by names or DI keys ( #2262 ).

Previously, applications were limited to a single default store, which meant contending with large monolithic state objects as applications grew. Multiple stores let you partition state into logical domains (user state, UI state, feature-specific data), each managed independently.

The @fromState decorator accepts optional store locators, and template syntax allows fine-grained store selection. The default store continues to work unchanged for backward compatibility.

Dialog

Child Dialog Services with Default Settings

Large applications often need preconfigured dialog services for different contexts: confirmation dialogs, form dialogs, notification dialogs. The new child dialog service API ( #2300 ) lets you create scoped dialog services with default settings that inherit from the parent:

const confirmService = dialogService.createChild({
  lock: true,
  overlayDismiss: false
});

// All dialogs opened via confirmService inherit these defaults
confirmService.open({ component: ConfirmDialog });

This eliminates repetitive configuration and provides cleaner separation of dialog concerns.

Router Enhancements

Beta 27 brings five router improvements that address common pain points.

Aggregated Route Parameters

The new getRouteParameters() helper ( #2264 ) gives nested components clean access to ancestor parameters without walking parent chains. For a route like company/:companyId/project/:projectId/task/:taskId, deeply nested components can now:

import { getRouteParameters } from '@aurelia/router';

// Get all parameters from the route hierarchy
const params = getRouteParameters(this);
console.log(params.companyId, params.projectId, params.taskId);

The helper supports configurable merge strategies when parameter names collide across route levels.

The loaded Lifecycle Hook

The new loaded hook ( #2267 ) fires after the component swap completes, once per navigation. This complements loading (which fires before swap) and provides a dedicated point for initialization that requires the component to be fully attached:

export class MyComponent {
  loading(params) {
    // Before swap - fetch data
  }

  loaded(params) {
    // After swap - initialize third-party libraries that need DOM
  }
}

Navigation Direction Detection

Know whether the user navigated forward or backward with the new isBack property ( #2243 ):

loading(params, instruction) {
  if (instruction.navigation.isBack) {
    // Restore scroll position, skip animations, etc.
  }
}

External Link Detection

The router now auto-detects absolute URLs, protocol links, and protocol-relative hrefs as external ( #2270 ). No more external attributes on every outbound link. You can configure an allow-list for domains that should still use router navigation.

Repeat Improvements

The $previous Variable

The new contextual property enables the $previous variable in repeaters ( #2261 ). This unlocks patterns that previously required external state:

<!-- Section headers when category changes -->
<div repeat.for="item of items">
  <h2 if.bind="item.category !== $previous?.category">
    ${item.category}
  </h2>
  <div>${item.name}</div>
</div>

<!-- Highlight changes in a changelog -->
<div repeat.for="entry of changelog">
  <span class="${entry.value !== $previous?.value ? 'changed' : ''}">
    ${entry.value}
  </span>
</div>

Contextual properties are enabled by default. Apps that want less work in the repeater can disable them:

<div repeat.for="item of items; contextual: false">

Observation

Manual Getter Dependencies

The @computed decorator now accepts explicit dependencies ( #2260 ), giving you precise control over when getters re-evaluate:

@computed('items.length', 'taxRate')
get total() {
  return this.items.reduce((sum, i) => sum + i.price, 0) * (1 + this.taxRate);
}

Options include flush timing (sync vs async) and deep observation:

@computed({ deps: ['cart'], deep: true })
get cartTotal() {
  // Re-evaluates when any cart item property changes
}

Note: deep observation doesn’t observe newly added properties. Replace the entire object to trigger updates.

UI Virtualization

The virtualization plugin received a comprehensive overhaul ( #2178 ):

• Variable item heights: render items of different sizes (use cautiously, layout calculations are expensive)
• Horizontal scrolling: virtualize horizontal lists alongside vertical ones
• Infinite scrolling: event-driven loading as users approach content boundaries
• Better configurability: bindable properties for sizing and behavior
• Improved error handling: centralized error codes with descriptive messages

Validation

Cross-Field Validation with ensureGroup

The new ensureGroup method ( #2217 ) handles validation scenarios where fields depend on each other:

ValidationRules
  .ensureGroup()
  .satisfies((model) => model.endDate > model.startDate)
  .withMessage('End date must be after start date')
  .on(MyModel);

Plugin Conventions

HTML Transformation

The new transformHtml option ( #2320 ) lets you modify HTML during the build process. This is useful for preprocessing, optimization, or custom syntax.

Template Type-Checker Improvements

The template type-checker now supports <let> declarations ( #2223 ) and with bindings ( #2224 ) with proper scope visibility, catching more errors at build time.

Bug Fixes

This release includes 16 bug fixes across the framework:

• HMR: Fixed doubly rendered elements and broken state on hot reload ( #2206 , #2316 , #2326 )
• Router: Fixed error recovery, URL generation, nav: false exceptions, and hash fragment paths ( #2263 , #2254 , #2251 , #2218 )
• Binding: Property bindings now stop reacting during controller deactivation ( #2293 )
• Computed observers: Callback timing now matches normal observer behavior ( #2249 )
• Bindables: Underscores in attribute names are preserved (_my_prop stays _my_prop) ( #2241 )
• au-compose: Surrogate attributes now apply correctly to host elements ( #2272 )
• Web components: Observed attribute naming conventions are now enforced ( #2298 )
• CSS Modules: Fixed processing for static class attributes in nested templates ( #2226 )
• Build: Fixed package.json exports for the development condition and added Node 22 compatibility ( #2321 , #2327 )

Breaking Changes

DOM Queue Removed

The old platform.domQueue and platform.taskQueue APIs have been removed ( #2305 ) in favor of the queue implementation introduced in Beta 25. If you’re using these directly, migrate to the new queue API:

import { queueTask, tasksSettled } from 'aurelia';

queueTask(() => {
  // Your queued work
});

await tasksSettled();

Contributors

Thanks to everyone who contributed to this release:

• @bigopon
• @fkleuver
• @Sayan751
• @Vheissu
• @RubenMaguregui

Full Changelog

• https://github.com/aurelia/aurelia/compare/v2.0.0-beta.26…v2.0.0-beta.27
• https://github.com/aurelia/aurelia/releases/tag/v2.0.0-beta.27

Upgrade Guide

1. Update your @aurelia/* dependencies to 2.0.0-beta.27
2. Replace any platform.domQueue or platform.taskQueue usage with the new queue API
3. Test your app thoroughly, this is a large release

Beta 27 represents months of work across state management, routing, rendering, and SSR foundations. The groundwork being laid now will enable server-side rendering and ahead-of-time compilation in upcoming releases. As always, join us on Discord if you have questions or encounter issues.