Which Cross-Platform Framework Should Agencies Choose in 2026?

I wouldn’t say this came down to a single framework like React Native or Flutter. Not every framework is a good fit for every app, and a lot depends on the specifics of the project and the industry it operates in.

What made the difference on those projects wasn’t chasing a “best” framework, but choosing one that matched the actual constraints of the work: how complex the business logic was, how long the app was expected to live, how often it would change, and how many teams would touch the code over time. In agency environments, those factors matter more than raw development speed or popularity, because every shortcut taken early tends to show up later as delivery risk.

In this guide, I’ll break down each framework from my perspective as a senior mobile developer, showing what works, what challenges to expect, and which framework often provides the best balance between speed and reliability.

How I Evaluate Cross-Platform Frameworks for Agency Projects

When you’re delivering multiple client apps at once, the framework you pick isn’t just a technical decision, but it directly affects timelines, quality, and team sanity. I don’t look for the “hottest” framework or the one with the largest community.

Here are the things I look at when comparing frameworks like Flutter, React Native, Kotlin Multiplatform (KMP), and Compose Multiplatform (CMP):

Onboarding speed: How fast can a new developer start contributing? Some frameworks, like Flutter, are easy to pick up for UI work, but maintaining complex apps can take longer. KMP and CMP can take a bit more time to learn, but once the team understands the setup, scaling multiple apps becomes easier.

Shared logic vs platform code: Can the same code run on both iOS and Android? KMP is strong here, letting you share business logic while keeping full native control of the UI. Flutter and React Native often try to share UI too, which can be tricky when apps get complex. CMP is good for certain widgets or small modules, but not every project.

Predictability of changes: Will a small change break other parts of the app? Flutter vs CMP, or KMP vs React Native, all have different ways of handling shared code. Picking the right framework reduces surprises when multiple client apps are running in parallel.

Long-term maintenance: How easy is it to maintain the app as it grows? A framework might be fast to start, like Flutter or React Native, but hard to maintain across several apps. KMP usually keeps shared logic clean, making long-term maintenance more predictable.

Delivery risk: Every project has deadlines, and the wrong framework adds hidden risks. The right one helps you deliver multiple apps without burning out the team.

By looking at cross-platform frameworks this way, it’s easier to see the differences between them, Flutter vs React Native vs KMP vs CMP, and choose the one that works best for agency projects. Later, I’ll go through each framework in detail and explain what works, what to watch out for, and why KMP often balances speed and reliability the best.

Flutter in Agency Projects

Flutter is great for quickly building apps with polished UIs. It’s easy to prototype, and you can get screens up fast, which makes it appealing for agency projects with tight deadlines. Developers can pick it up quickly, especially if they’re familiar with Dart or front-end frameworks.

That said, when you’re managing multiple client apps in parallel, Flutter can start showing its limits. Sharing business logic across apps isn’t as straightforward, and complex projects sometimes require lots of workarounds. Compared to Kotlin Multiplatform, where shared logic stays predictable across iOS and Android, Flutter can be trickier to maintain as projects scale.

Flutter also tries to share UI across platforms. That’s fine for simple apps, but when client apps have slightly different designs or platform-specific requirements, it can slow development. In contrast, Compose Multiplatform lets you isolate small reusable UI components, but it’s still niche and not as battle-tested for full client apps.

Finally, Flutter’s ecosystem is large, but dependency updates or breaking changes can occasionally cause headaches when multiple apps rely on the same libraries. React Native has similar challenges, but KMP’s approach of separating shared logic from native UI often makes scaling multiple projects easier.

In short: Flutter is excellent for fast UI-heavy apps and prototypes, but for agencies running several apps in parallel, frameworks like KMP or CMP can offer more predictable long-term maintainability and team scalability.

Here you can read more on Flutter vs CMP.

React Native Across Multiple Client Apps

React Native has been around for a while, and it’s a solid choice if your team is familiar with JavaScript or already has web developers who can contribute. For agencies delivering several client apps, this can be a real advantage because onboarding is usually faster than starting from scratch with a new language.

That said, React Native comes with trade-offs. While it allows sharing a lot of code between iOS and Android, complex business logic and platform-specific features often require custom bridges. These can become tricky to maintain when multiple apps rely on the same shared modules. Compared to KMP, where shared logic is cleanly separated from native UI, React Native projects can be harder to scale without introducing unexpected bugs.

React Native is often compared to Flutter because both aim to speed up development. Flutter gives more control over UI with a single codebase, while React Native relies on native components, which sometimes leads to inconsistencies across platforms. CMP, on the other hand, focuses on small, reusable UI modules but isn’t yet widely used for full client apps, which is something to consider if you want predictable long-term maintenance.

In practice, React Native works well for agencies with simpler apps or teams heavily invested in JavaScript. But when managing multiple client projects with complex logic and long-term evolution, KMP usually provides more stability, easier onboarding, and predictable delivery timelines.

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Kotlin Multiplatform: Not the Fastest, But the Most Predictable

When managing multiple client apps at the same time, speed isn’t always the most important factor, predictability and maintainability matter more. Unlike Flutter or React Native, Kotlin Multiplatform focuses on sharing business logic across iOS and Android while keeping full native control of the UI. This separation reduces unexpected bugs, makes onboarding new developers faster, and keeps delivery timelines under control.

At Aetherius, we recently added KMP to an existing native app that had separate iOS and Android codebases. Instead of rewriting the app, we migrated the core business logic step by step, including networking, data models, and validation. This approach allowed the app to continue running smoothly while sharing critical logic across platforms, improving maintainability and making future updates much faster.

Migrating to KMP doesn’t have to be all or nothing. A step-by-step approach works best:

1. Start with shared business logic: move networking, data models, and validation into KMP modules.
2. Keep native UIs intact: don’t force UI sharing at first; this avoids breaking the existing app.
3. Gradually expand shared modules: add caching, analytics, or payment logic as confidence grows.
4. Integrate CI/CD for shared code: ensure changes in KMP modules are tested across all apps.
5. Train new developers on the shared layer first: they can contribute safely without touching platform-specific code immediately.

Compared to Flutter vs KMP, Flutter might let you spin up a UI quickly, but KMP scales far better across multiple client apps. React Native vs KMP shows a similar pattern: React Native is familiar and fast for simple apps, but complexity multiplies when multiple apps and teams work in parallel. CMP vs KMP demonstrates that while CMP is powerful for small reusable modules or widgets, KMP is stronger for full client apps where shared logic consistency is critical.

Using KMP in this way, adding it to an existing native app gradually and focusing on predictability, allows agencies to deliver multiple apps without burning out teams or introducing hidden delivery risks. It’s not the fastest to start, but for cross-platform mobile app development in 2026, it often saves the most time in the long run.

Compose Multiplatform: Powerful, But Project-Specific

CMP is an interesting option for agencies, but it’s not a one-size-fits-all solution. CMP allows you to share UI components across platforms, which can save time on specific features. For example, reusable widgets like custom charts, data cards, or small polling modules can be written once and used across mobile, desktop, or web apps.

The recent CMP 1.10.0 release makes it even more practical for agency work. You can now use a single @Preview for all platforms, see hot reload updates instantly, and rely on consistent navigation across mobile and desktop apps. Dependency management is also cleaner, making it easier to add libraries without confusion. These updates reduce some of the friction that previously made CMP harder to adopt in real projects.

That said, CMP still works best for isolated UI modules or small features, not entire client apps. While Kotlin Multiplatform focuses on sharing business logic across iOS and Android, CMP is mainly about UI. Compared to Flutter vs CMP, Flutter is better for building full apps from scratch with consistent UI, and React Native vs CMP usually offers more ecosystem support and developer availability. CMP can complement KMP, but it’s not yet the backbone for large, complex projects with multiple client apps.

In short: CMP is powerful, especially with the 1.10.0 improvements, but for agencies that need predictable, maintainable cross-platform mobile apps, KMP remains the main choice for shared logic, while CMP can handle specific UI improvements efficiently.

You can read more on KMP vs CMP to have better insights when making a decision.

Choosing the Right Framework Based on Project Constraints

As I already mentioned, there’s no universal “best” cross-platform framework, it all depends on the project.

Here’s how I think about it:

1. Short-lived or UI-heavy apps

• Flutter is often the fastest to start and delivers polished UI quickly.
• Good for prototypes or client apps with simple logic and consistent design.
• CMP can help share certain UI modules, but KMP isn’t always necessary here.

2. Long-term, logic-heavy apps

• KMP shines here. Shared business logic reduces duplication, keeps changes predictable, and scales across multiple apps.
• Migrating existing native apps to KMP step by step makes onboarding and feature delivery smoother.
• Flutter or React Native can work, but maintenance risk grows with complexity.

3. Apps that evolve over time

• Apps that will change often, or have multiple teams contributing, benefit from KMP’s separation of shared logic and native UI.
• CMP can complement KMP for shared UI components, especially after the 1.10.0 updates with better previews, navigation, and hot reload.

4. Limited scope or small reusable modules

• CMP is ideal for isolated features: widgets, charts, forms, or small cross-platform tools.
• Flutter or React Native may be overkill for these, and KMP can be too heavy if only UI needs sharing.

The main takeaway: agencies delivering multiple client apps should pick frameworks based on project size, team setup, and how predictable they need delivery to be. In most scenarios, KMP forms the backbone for shared logic, while CMP or Flutter can complement it for UI-specific needs. React Native remains a valid choice if the team is experienced with JavaScript and the apps aren’t too complex.

At Aetherius, we worked on a fitness app for a client that already had separate iOS and Android apps. They needed to add several new features across both platforms:

• Workout tracking logic: calculating calories burned, tracking exercise completion, and storing session history.
• Social sharing: letting users post achievements to their feed.
• In-app reminders: notifications for scheduled workouts.

We had to choose a framework carefully:

• Flutter could have delivered the UI quickly, but sharing the workout tracking logic across apps would have required duplicating code or adding complex workarounds.
• React Native would have faced similar issues, with additional bridges for platform-specific functionality.
• CMP was useful for small UI components like achievement badges and stats cards, but it didn’t solve the core logic sharing problem.

We decided to add KMP step by step:

1. Moved workout tracking and session history logic into KMP modules.
2. Kept native UI for iOS and Android intact to avoid rewriting screens.
3. Gradually added shared modules for in-app reminders and social features, ensuring all platforms stayed consistent.

This approach allowed the team to deliver new features predictably, share business logic across both apps, and maintain existing native UI without disruptions. CMP complemented KMP for UI widgets, but KMP became the backbone for the shared logic, which was critical for this multi-app, feature-heavy project.

Final Thoughts: Navigating Mobile Trends in 2026

Mobile trends in 2026 show that agencies need flexible cross-platform solutions more than ever. Delivering multiple client apps simultaneously is only going to get more complex, and the framework you choose can either make your life easier or create long-term headaches.

Flutter remains strong for fast, UI-heavy projects.

React Native is a solid choice if your team is experienced with JavaScript and the app isn’t too complex.

Compose Multiplatform shines for shared UI modules, especially with the 1.10.0 updates that improved previews, navigation, and hot reload.

Kotlin Multiplatform is the framework that consistently delivers on shared business logic, predictability, and scalability, the backbone that agencies need when multiple apps, teams, and deadlines are involved.

At Aetherius, adding KMP to an existing native fitness app step by step allowed us to share complex workout logic, in-app reminders, and social features across iOS and Android without breaking existing screens. CMP complemented it for UI widgets, but KMP kept delivery predictable and maintainable.

The takeaway for agencies: in line with mobile trends 2026, it’s not about the fastest framework or the most popular one. It’s about picking the technology that matches your project’s complexity, team structure, and delivery goals. For most multi-app scenarios, KMP provides the balance between speed and maintainability, while CMP, Flutter, and React Native can complement it where needed.

If your agency wants to stay ahead in 2026, focus on frameworks that let you deliver multiple client apps efficiently, reduce surprises, and scale your team without compromise.

If your agency is juggling multiple client apps or complex projects and needs extra hands or guidance, come back to us!

We can help you choose the right framework, integrate KMP or CMP, and scale your delivery without surprises.