Compose 1.13 Beta: PolygonShape Rewrite, Required Slider onValueChange and a Faster Modifier.border

Compose 1.13 has been in alpha since August. Beta01 landed on October 7, 2026 and beta02 followed on October 21, and the beta01 API notes are where the real work is: several source-breaking renames, a Slider parameter that is now mandatory, a PolygonShape API that was restructured, and a Kotlin 2.2 floor. Beta02 is bug-fix only, but it quietly swaps in a new Modifier.border implementation you should test.

1. Toolchain: Kotlin 2.2 Is the Floor

Beta01 libraries target Kotlin 2.2 and require kotlinc 2.2. If your project is still on an older compiler, the Compose upgrade is also a Kotlin upgrade. Do that first, in its own commit, so a compiler regression isn't confused with a Compose one.

2. Slider: onValueChange Is Now Required

onValueChange is now a required parameter on Slider, VerticalSlider and RangeSlider. The previously hidden deprecated APIs were also removed, including the DraggableState implementation on SliderState, the legacy Saver overloads and isVertical on SliderState. The SliderDefaults.Thumb overload taking SliderState is deprecated; use the overload with isVertical.

var volume by remember { mutableFloatStateOf(0.5f) }

Slider(
    value = volume,
    onValueChange = { volume = it },
    valueRange = 0f..1f
)

Any code that built a slider from a SliderState without supplying a change callback, or that treated SliderState as a DraggableState, will stop compiling. Grep for both before you bump.

3. PolygonShape Was Restructured

Two API changes in Foundation and UI hit anyone using PolygonShape:

• CornerRounding moved to the top level, with dp() and fraction() factories.
• The transformed() and scaledToFit() extensions were replaced by an in-place PolygonShape.transform(PolygonShapeTransformScope.() -> Unit) and PolygonShape.copy().
• Factory parameters now carry @FloatRange / @IntRange, and innerRadiusRatio on PolygonShape.star and PolygonShape.pillStar is restricted to (0f, 1f).

Because transform is in place, call copy() first when the original shape is shared. The notes describe it as an in-place mutable transform, so don't assume the old return-a-new-shape behavior.

4. Modifier.blur, MediaQuery and Interaction Barrier

• Modifier.blur: the radius parameter is now blurRadiusSpec, as is BlurScope.radius. BlurStop.fraction gains @FloatRange, and the default fallOffRadius in BlurRadiusSpec.radialGradient changed to Dp.Unspecified.
• Posture in MediaQuery: replaced by WindowPosture, which exposes physical WindowFolds (FoldState and FoldOrientation). It adds isTabletop and isFlat, and the explicit Book posture is gone.
• Modifier.interactionBarrier(): removed from the public API surface for 1.13.

5. Beta02: A New Modifier.border

Beta02 is documented as bug fixes only, but the first entry is significant: Modifier.border uses a new, more performant implementation, and it can now render generic and polygon shapes using a runtime shader. A separate fix addresses an edge case when rendering certain rounded rectangle outlines.

Both have escape hatches in case of visual diffs:

// Foundation flags from the 1.13.0-beta02 notes
ComposeFoundationFlags.isNewBorderImplementationEnabled = false
ComposeFoundationFlags.isRoundedRectangleBorderRenderingFixEnabled = false

If you need either flag, the release notes ask you to file a bug. Run your screenshot tests over bordered cards, chips and text fields before shipping this.

6. Smaller Fixes Worth Knowing

• BasicTextField focus: it now waits for the window to gain focus before starting the text input session. This fixes the keyboard not appearing when focus was requested before the window was focused, for example in onCreate. Revert with ComposeFoundationFlags.isTextFieldWaitWindowFocusForInputSessionEnabled = false.
• FlexBox: alignContent(FlexAlignContent.Stretch) no longer forces children to stretch with their line, and a single wrapped line is no longer expanded to the minimum cross-axis constraint.
• Lazy layouts: the cache window no longer re-prefetches items when a previously prefetched item becomes visible.
• Insets: an IllegalStateException when updating consumeWindowInsets, windowInsetsPadding or onConsumedWindowInsetsChanged on detached modifier nodes (such as during movableContent movement) is fixed.
• VectorPainter: now shares internal ImageBitmap resources when the same ImageVector is drawn in multiple composables; disable with ComposeUiFlags.isVectorDrawCacheSharingEnabled.
• Accessibility and crashes: TalkBack touch exploration no longer jumps to an AndroidView (such as a WebView) covered by Compose content, and a crash from Color.toColorLong() on colors composited over Color.Unspecified is fixed.
• Styles API: CommonStyle.styleLayer() was added; properties in a layer override lower layers, and state() helpers such as pressed() now create a layer implicitly.

Should You Move Now?

Beta means the API surface is meant to be settled, so this is the right time to compile against it and see what breaks, not to ship it. My order: Kotlin 2.2 first, then the Compose bump on a branch, fix slider and shape call sites, then run screenshot tests specifically for borders and text field focus. If a flag is needed, file the bug before stable ships while it can still be fixed.

Sources: the Compose Foundation and Compose UI release notes on developer.android.com (1.13.0-beta01 and 1.13.0-beta02).