diff --git a/.changeset/reactive-prop-derivations.md b/.changeset/reactive-prop-derivations.md
new file mode 100644
index 0000000000..7fc917150b
--- /dev/null
+++ b/.changeset/reactive-prop-derivations.md
@@ -0,0 +1,5 @@
+---
+'@evidence-dev/core-components': patch
+---
+
+Make prop-derived chart values reactive: Area's and Line's default label positions now follow `swapXY`, and Sparkline's series type follows `type`, instead of freezing at their mount-time values.
diff --git a/packages/ui/core-components/src/lib/unsorted/viz/area/Area.svelte b/packages/ui/core-components/src/lib/unsorted/viz/area/Area.svelte
index a70379fbc7..9cb11494e8 100644
--- a/packages/ui/core-components/src/lib/unsorted/viz/area/Area.svelte
+++ b/packages/ui/core-components/src/lib/unsorted/viz/area/Area.svelte
@@ -117,7 +117,7 @@
 		middle: 'inside'
 	};
 
-	let defaultLabelPosition = swapXY ? 'right' : 'top';
+	$: defaultLabelPosition = swapXY ? 'right' : 'top';
 	$: labelPosition =
 		(swapXY ? swapXYLabelPositions[labelPosition] : labelPositions[labelPosition]) ??
 		defaultLabelPosition;
diff --git a/packages/ui/core-components/src/lib/unsorted/viz/core/_Sparkline.svelte b/packages/ui/core-components/src/lib/unsorted/viz/core/_Sparkline.svelte
index 10db89655b..34b2f0ed09 100644
--- a/packages/ui/core-components/src/lib/unsorted/viz/core/_Sparkline.svelte
+++ b/packages/ui/core-components/src/lib/unsorted/viz/core/_Sparkline.svelte
@@ -37,7 +37,7 @@
 	export let yScale = false; // scale the y axis to the data
 	$: yScale = yScale === 'true' || yScale === true;
 
-	let seriesType = type === 'area' ? 'line' : type;
+	$: seriesType = type === 'area' ? 'line' : type;
 
 	export let connectGroup = undefined; // connects to all other connected sparklines with the same group name (shared tooltip behaviour)
 
diff --git a/packages/ui/core-components/src/lib/unsorted/viz/line/Line.svelte b/packages/ui/core-components/src/lib/unsorted/viz/line/Line.svelte
index 3541f27388..d0ff12e0a3 100644
--- a/packages/ui/core-components/src/lib/unsorted/viz/line/Line.svelte
+++ b/packages/ui/core-components/src/lib/unsorted/viz/line/Line.svelte
@@ -139,7 +139,7 @@
 		middle: 'inside'
 	};
 
-	let defaultLabelPosition = swapXY ? 'right' : 'top';
+	$: defaultLabelPosition = swapXY ? 'right' : 'top';
 	$: labelPosition =
 		(swapXY ? swapXYLabelPositions[labelPosition] : labelPositions[labelPosition]) ??
 		defaultLabelPosition;