Android Studio may fail to render a Compose Preview with KotlinReflectionNotSupportedError even though the same UI runs correctly on a device or emulator. This article covers the known Preview regression identified in Android Studio Quail 2 (2026.1.2) and Rabbit 1 Canary 4, explains how to distinguish it from a real missing dependency, and provides a safe resolution path.
Representative error
kotlin.jvm.KotlinReflectionNotSupportedError:
Kotlin reflection implementation is not found at runtime.
Make sure you have kotlin-reflect.jar in the classpathThe exception occurs while Android Studio is rendering a Compose Preview. The Preview pane may remain blank or show a render problem and stack trace, while deploying the same composable to a device or emulator still works.
Cause
Google lists this problem as Issue #559426543: Compose Preview fails to use kotlin-reflect and throws KotlinReflectionNotSupportedError. The official fixed-issues page specifically identifies Android Studio 2026.1.2 and 2026.2.1 Canary 4 as affected versions.
In this scenario, the problem is in the classpath Android Studio builds for its standalone Preview renderer, not necessarily in the application’s runtime classpath. Adding a dependency solely because the exception mentions kotlin-reflect.jar may therefore have no effect when the IDE regression is the real cause.
Important: If the same exception also occurs on a physical device or emulator, investigate the application’s runtime dependencies. The known Android Studio issue is most strongly indicated when only Compose Preview fails.
Affected and fixed versions
- Android Studio Quail 2 (2026.1.2)
- Android Studio Rabbit 1 Canary 4 (2026.2.1 Canary 4)
- Previews that evaluate application or library code using Kotlin Reflection
- Projects where runtime deployment works but Design or Split Preview fails
Google lists the issue under Android Studio Rabbit 2 Canary 2 (2026.2.2 Canary 2) fixed issues. Rabbit 2 Canary 2 is therefore the first version for which an official fix is confirmed.
Recommended resolution
- Identify where the failure occurs: Run the affected composable on a device or emulator. If the application works and only Preview fails, the symptoms match the IDE issue.
- Check the Android Studio version: Open Help > About Android Studio, or Android Studio > About Android Studio on macOS. Confirm whether you are using 2026.1.2 or 2026.2.1 Canary 4.
- Upgrade to a fixed build: If preview builds are acceptable in your environment, install Rabbit 2 Canary 2 or later. If your organization requires stable releases, keep using a known-good Android Studio installation until a stable release containing the fix is available.
- Restart and sync: After upgrading, restart the IDE, run Gradle Sync, and reopen the file in Design or Split mode.
- Render the same preview again: Verify that the exception is gone and the composable renders.
When to check the application dependency
If the exception also appears when the app runs on a device or emulator, inspect the affected module’s dependencies. Code that directly uses Kotlin Reflection requires a compatible kotlin-reflect artifact.
dependencies {
implementation(kotlin("reflect"))
}Projects using a version catalog or the Kotlin BOM should follow their existing version-alignment policy. Do not add this dependency automatically when runtime execution is already successful and only Preview is broken. It can increase the dependency footprint without correcting the Android Studio renderer regression.
Alternative approaches
- Validate the UI on a device or emulator until a fixed Android Studio build is available.
- Keep a known-good Android Studio version installed separately and use it for Preview work on the affected project.
- If the design permits it, pass simple Preview-only sample data that does not execute reflection-dependent initialization. This is a project-specific workaround, not Google’s underlying fix.
How to verify the fix
- Open the composable file that previously failed.
- Switch to Split or Design view and rebuild the Preview.
- Confirm that
KotlinReflectionNotSupportedErrorno longer appears. - Launch the same screen on a device or emulator to verify that no dependency change introduced a runtime problem.
- For team projects, record the Android Studio build number and Kotlin and Compose versions used for the successful test.
Cautions
Invalidate Caches and deleting Gradle caches can help rule out stale state, but neither operation is the documented fix for Issue #559426543. Do not treat a temporary improvement after cache removal as proof that the version-specific regression has been resolved.
Canary builds are intended for testing. In production environments, install the preview build alongside the current stable IDE rather than overwriting it, and keep the project under version control.
Summary
When KotlinReflectionNotSupportedError affects Compose Preview only, the failure may be the known Android Studio 2026.1.2 / 2026.2.1 Canary 4 regression. Confirm that the app itself still runs, then move to Rabbit 2 Canary 2 or later, where Google lists the issue as fixed. Investigate or add the application’s kotlin-reflect dependency only when the runtime build also fails.
Official references
