Which @angular/* package(s) are relevant/related to the feature request?

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Description

Feature Request: Multi-Version Angular Microfrontend Support

We are requesting enhanced support for microfrontend architecture that allows multiple Angular versions (v14, v16, v19, v20) to coexist within a single application ecosystem. This feature would enable organisations to maintain, upgrade, and scale large Angular applications more effectively while reducing technical debt and deployment risks.
Problem Statement
Current Challenges
Version Lock-in: Large enterprise applications are often locked into specific Angular versions due to the complexity and risk associated with major version upgrades. This creates technical debt and prevents teams from leveraging newer Angular features and performance improvements.
Monolithic Upgrade Constraints: Traditional Angular applications require complete application upgrades, which can take months or years for large code bases, during which teams cannot adopt new features or security patches from newer Angular versions.
Team Independence: In large organisations, different teams may work on different parts of the application but are forced to coordinate Angular version upgrades, slowing down development velocity and creating cross-team dependencies.
Legacy Code Maintenance: Organisations struggle to maintain older Angular code while simultaneously developing new features with modern Angular capabilities.

Proposed solution

Proposed Solution

Multi-Version Microfrontend Architecture
Implement a comprehensive microfrontend solution that supports:

Angular v14 Support: Maintain existing applications built on Angular 14 with full feature compatibility
Angular v16 Support: Enable teams to leverage standalone components, required inputs, and improved developer experience
Angular v19 Support: Access to latest features including improved hydration, new lifecycle hooks, and performance optimizations
Angular v20 Support: Future-proof architecture for upcoming Angular releases and features

Alternatives considered

Alternatives Considered

1. Complete Application Rewrite

Approach: Rebuild entire application using latest Angular version
Rejected: 6-24 month timeline, high risk, expensive, potential loss of domain knowledge

2. Monolithic Upgrade

Approach: Upgrade entire application version by version in coordinated manner
Rejected: Blocks development, requires cross-team coordination, prevents incremental feature adoption

3. IFrame Integration

Approach: Deploy different Angular versions as separate applications connected via iframes
Rejected: Poor user experience, complex state sharing, SEO issues, browser security restrictions

4. Hybrid Framework Approach

Approach: Migrate parts to React/Vue while maintaining Angular core
Rejected: Multiple framework expertise required, inconsistent UX, increased complexity and bundle size

5. Web Components (Angular Elements)

Approach: Convert Angular components to Web Components for cross-version compatibility
Rejected: Limited Angular features, performance overhead, complex state management

6. Server-Side Composition

Approach: Use server-side includes to compose different Angular applications
Rejected: Infrastructure complexity, poor client-side state management, increased latency

7. Docker Microservices

Approach: Deploy each Angular version as separate containerized services
Rejected: Not suitable for frontend integration, network latency, complex local development

8. Angular Universal Version Switching

Approach: Server-side rendering with different Angular versions based on routes
Rejected: Complex infrastructure, hydration challenges, limited client-side state sharing

Why Multi-Version Microfrontend is Optimal

✅ Maintains Angular ecosystem benefits
✅ Enables incremental version adoption
✅ Seamless user experience
✅ Minimizes migration risk and cost
✅ Preserves existing Angular expertise
✅ Allows parallel team development