diff --git a/CLAUDE.md b/CLAUDE.md
index 7a49895..4dca9c6 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -51,4 +51,4 @@ For components that accept children (layers, popups, tooltips), use the `registe
 
 ### Output
 
-`tsc` compiles `src/` → `dist/` as individual ESM modules (`.js` + `.d.ts` + `.d.ts.map`), then `rollup -c` bundles `dist/index.js` (ESM), `dist/index.cjs` (CJS), and `dist/index.umd.js` (UMD) — each with minified variants. Leaflet is always external (never bundled). Imports within source use `.js` extensions (required for ESM `"moduleResolution": "bundler"`).
+`tsc` compiles `src/` → `dist/` as individual ESM modules (`.js` + `.d.ts` + `.d.ts.map`), then `rollup -c` bundles `dist/index.js` (ESM), `dist/index.cjs` (CJS), and `dist/index.umd.js` (UMD) — each with minified variants. Leaflet is always external (never bundled). Imports within source use `.ts` extensions; `rewriteRelativeImportExtensions` in tsconfig strips them to `.js` in the tsc output (`tsconfig.json:16`).
diff --git a/src/components/leaflet-circle-marker.ts b/src/components/leaflet-circle-marker.ts
index c1fb349..e6b331c 100644
--- a/src/components/leaflet-circle-marker.ts
+++ b/src/components/leaflet-circle-marker.ts
@@ -1,10 +1,10 @@
 import { CircleMarker } from 'leaflet';
-import { buildOptions, numAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, numAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import { isPathStyleAttr, updatePathStyle } from '../core/path-style.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
diff --git a/src/components/leaflet-circle.ts b/src/components/leaflet-circle.ts
index 7ccdc29..b891d35 100644
--- a/src/components/leaflet-circle.ts
+++ b/src/components/leaflet-circle.ts
@@ -1,10 +1,10 @@
 import { Circle } from 'leaflet';
-import { buildOptions, numAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, numAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import { isPathStyleAttr, updatePathStyle } from '../core/path-style.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
diff --git a/src/components/leaflet-control-attribution.ts b/src/components/leaflet-control-attribution.ts
index deb849d..b21b36e 100644
--- a/src/components/leaflet-control-attribution.ts
+++ b/src/components/leaflet-control-attribution.ts
@@ -1,8 +1,8 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { registerWithParent } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import type { PropDef } from '../core/props.js';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'bottomright' },
diff --git a/src/components/leaflet-control-scale.ts b/src/components/leaflet-control-scale.ts
index 9ae2ceb..0fecc3c 100644
--- a/src/components/leaflet-control-scale.ts
+++ b/src/components/leaflet-control-scale.ts
@@ -1,8 +1,8 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { registerWithParent } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import type { PropDef } from '../core/props.js';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'bottomleft' },
diff --git a/src/components/leaflet-control-zoom.ts b/src/components/leaflet-control-zoom.ts
index 2792d04..247de6c 100644
--- a/src/components/leaflet-control-zoom.ts
+++ b/src/components/leaflet-control-zoom.ts
@@ -1,8 +1,8 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { registerWithParent } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import type { PropDef } from '../core/props.js';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'topleft' },
diff --git a/src/components/leaflet-feature-group.ts b/src/components/leaflet-feature-group.ts
index b6a8a32..d85df28 100644
--- a/src/components/leaflet-feature-group.ts
+++ b/src/components/leaflet-feature-group.ts
@@ -1,6 +1,6 @@
 import { FeatureGroup, Layer } from 'leaflet';
-import { buildOptions } from '../core/utils.js';
-import { registerChildren, unregisterChildren, getChildren } from '../core/register.js';
+import { buildOptions } from '../core/utils.ts';
+import { registerChildren, unregisterChildren, getChildren } from '../core/register.ts';
 
 export class LeafletFeatureGroup extends HTMLElement {
   #obj?: FeatureGroup;
diff --git a/src/components/leaflet-geojson.ts b/src/components/leaflet-geojson.ts
index ef344e8..1402cd6 100644
--- a/src/components/leaflet-geojson.ts
+++ b/src/components/leaflet-geojson.ts
@@ -1,9 +1,9 @@
 import { GeoJSON, PathOptions, Layer } from 'leaflet';
-import { buildOptions } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren, getChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren, getChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   data: { kind: 'str', attr: 'data', default: '' },
diff --git a/src/components/leaflet-image-overlay.ts b/src/components/leaflet-image-overlay.ts
index ea17fde..b2cc9b0 100644
--- a/src/components/leaflet-image-overlay.ts
+++ b/src/components/leaflet-image-overlay.ts
@@ -1,10 +1,10 @@
 import { ImageOverlay, LatLngBounds, LatLngExpression } from 'leaflet';
 import type { ImageOverlayOptions } from 'leaflet';
-import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
diff --git a/src/components/leaflet-layer-group.ts b/src/components/leaflet-layer-group.ts
index 8d47c22..51ff034 100644
--- a/src/components/leaflet-layer-group.ts
+++ b/src/components/leaflet-layer-group.ts
@@ -1,6 +1,6 @@
 import { LayerGroup, Layer } from 'leaflet';
-import { buildOptions } from '../core/utils.js';
-import { registerChildren, unregisterChildren, getChildren } from '../core/register.js';
+import { buildOptions } from '../core/utils.ts';
+import { registerChildren, unregisterChildren, getChildren } from '../core/register.ts';
 
 export class LeafletLayerGroup extends HTMLElement {
   #obj?: LayerGroup;
diff --git a/src/components/leaflet-map.ts b/src/components/leaflet-map.ts
index 241d84b..ae1aada 100644
--- a/src/components/leaflet-map.ts
+++ b/src/components/leaflet-map.ts
@@ -1,5 +1,5 @@
 import { Icon, Map as LMap, MapOptions } from 'leaflet';
-import { LeafletRegisterEvent } from '../core/register.js';
+import { LeafletRegisterEvent } from '../core/register.ts';
 
 const DEFAULT_CSS_URL = 'https://unpkg.com/leaflet@1.9.4/dist/leaflet.css';
 const DEFAULT_CSS_INTEGRITY = 'sha256-p4NxAoJBhIIN+hmNHrzRCf9tD/miZyoHS5obTRR9BMY=';
diff --git a/src/components/leaflet-marker.ts b/src/components/leaflet-marker.ts
index fa3ee68..7ec8cf7 100644
--- a/src/components/leaflet-marker.ts
+++ b/src/components/leaflet-marker.ts
@@ -1,9 +1,9 @@
 import { Marker } from 'leaflet';
-import { buildOptions, numAttr, buildAttrMap, setLayerAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, numAttr, buildAttrMap, setLayerAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
diff --git a/src/components/leaflet-polygon.ts b/src/components/leaflet-polygon.ts
index 516d31f..e3e07f6 100644
--- a/src/components/leaflet-polygon.ts
+++ b/src/components/leaflet-polygon.ts
@@ -1,11 +1,11 @@
 import { Polygon } from 'leaflet';
-import { buildOptions } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef } from '../core/props.js';
-import type { LeafletLine } from './leaflet-line.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import { isPathStyleAttr, updatePathStyle } from '../core/path-style.ts';
+import type { PropDef } from '../core/props.ts';
+import type { LeafletLine } from './leaflet-line.ts';
 
 const PROPS = {
   color: { kind: 'str', attr: 'color', default: '#3388ff' },
diff --git a/src/components/leaflet-polyline.ts b/src/components/leaflet-polyline.ts
index bc2a532..45fb4f2 100644
--- a/src/components/leaflet-polyline.ts
+++ b/src/components/leaflet-polyline.ts
@@ -1,11 +1,11 @@
 import { Polyline } from 'leaflet';
-import { buildOptions } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef } from '../core/props.js';
-import type { LeafletLine } from './leaflet-line.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import { isPathStyleAttr, updatePathStyle } from '../core/path-style.ts';
+import type { PropDef } from '../core/props.ts';
+import type { LeafletLine } from './leaflet-line.ts';
 
 const PROPS = {
   color: { kind: 'str', attr: 'color', default: '#3388ff' },
diff --git a/src/components/leaflet-popup.ts b/src/components/leaflet-popup.ts
index 1cb55dd..dba3026 100644
--- a/src/components/leaflet-popup.ts
+++ b/src/components/leaflet-popup.ts
@@ -1,8 +1,8 @@
 import { Popup } from 'leaflet';
-import { registerWithParent, buildOptions, numAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { registerWithParent, buildOptions, numAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import type { PropDef } from '../core/props.js';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
diff --git a/src/components/leaflet-rectangle.ts b/src/components/leaflet-rectangle.ts
index 526e2a4..05d350c 100644
--- a/src/components/leaflet-rectangle.ts
+++ b/src/components/leaflet-rectangle.ts
@@ -1,10 +1,10 @@
 import { Rectangle } from 'leaflet';
-import { buildOptions, parseBoundsAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, parseBoundsAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import { isPathStyleAttr, updatePathStyle } from '../core/path-style.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   bounds: { kind: 'str', attr: 'bounds', default: '' },
diff --git a/src/components/leaflet-svg-overlay.ts b/src/components/leaflet-svg-overlay.ts
index 138f968..a2a472c 100644
--- a/src/components/leaflet-svg-overlay.ts
+++ b/src/components/leaflet-svg-overlay.ts
@@ -1,10 +1,10 @@
 import { SVGOverlay, LatLngBounds, LatLngExpression } from 'leaflet';
 import type { ImageOverlayOptions } from 'leaflet';
-import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   bounds: { kind: 'str', attr: 'bounds', default: '' },
diff --git a/src/components/leaflet-tile-layer-wms.ts b/src/components/leaflet-tile-layer-wms.ts
index 2299cdd..dc624f9 100644
--- a/src/components/leaflet-tile-layer-wms.ts
+++ b/src/components/leaflet-tile-layer-wms.ts
@@ -1,9 +1,9 @@
 import { TileLayer } from 'leaflet';
-import { buildOptions, buildAttrMap, setLayerAttr, parseAttributeValue } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, buildAttrMap, setLayerAttr, parseAttributeValue } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
diff --git a/src/components/leaflet-tile-layer.ts b/src/components/leaflet-tile-layer.ts
index 2264000..bc363a5 100644
--- a/src/components/leaflet-tile-layer.ts
+++ b/src/components/leaflet-tile-layer.ts
@@ -1,9 +1,9 @@
 import { TileLayer } from 'leaflet';
-import { buildOptions, buildAttrMap, setLayerAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, buildAttrMap, setLayerAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
diff --git a/src/components/leaflet-tooltip.ts b/src/components/leaflet-tooltip.ts
index 4d1fb94..ce8fcd5 100644
--- a/src/components/leaflet-tooltip.ts
+++ b/src/components/leaflet-tooltip.ts
@@ -1,9 +1,9 @@
 import { Tooltip } from 'leaflet';
 import type { TooltipOptions } from 'leaflet';
-import { registerWithParent, buildOptions, numAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { registerWithParent, buildOptions, numAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import type { PropDef } from '../core/props.js';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
diff --git a/src/components/leaflet-video-overlay.ts b/src/components/leaflet-video-overlay.ts
index 03425d6..88fe63a 100644
--- a/src/components/leaflet-video-overlay.ts
+++ b/src/components/leaflet-video-overlay.ts
@@ -1,10 +1,10 @@
 import { VideoOverlay, LatLngBounds, LatLngExpression } from 'leaflet';
 import type { VideoOverlayOptions } from 'leaflet';
-import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.js';
-import { withProps } from '../core/with-props.js';
+import { buildOptions, buildAttrMap, setLayerAttr, parseBoundsAttr } from '../core/utils.ts';
+import { withProps } from '../core/with-props.ts';
 
-import { registerChildren, unregisterChildren } from '../core/register.js';
-import type { PropDef } from '../core/props.js';
+import { registerChildren, unregisterChildren } from '../core/register.ts';
+import type { PropDef } from '../core/props.ts';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
diff --git a/src/core/path-style.ts b/src/core/path-style.ts
index fe1f8cb..2e3fac9 100644
--- a/src/core/path-style.ts
+++ b/src/core/path-style.ts
@@ -1,5 +1,5 @@
 import { Path } from 'leaflet';
-import { parseAttributeValue } from './utils.js';
+import { parseAttributeValue } from './utils.ts';
 
 // The set of HTML attribute names that map to Leaflet Path style options.
 // These are handled specially because Leaflet exposes them through
diff --git a/src/core/register.ts b/src/core/register.ts
index b032eba..39989ed 100644
--- a/src/core/register.ts
+++ b/src/core/register.ts
@@ -1,5 +1,5 @@
 import { Layer, LayerGroup, Popup, Tooltip } from 'leaflet';
-import { registerWithParent } from './utils.js';
+import { registerWithParent } from './utils.ts';
 
 // Custom event type for the bubbling registration protocol. Carries the
 // Leaflet object and the originating element so the nearest parent can
diff --git a/src/core/utils.ts b/src/core/utils.ts
index 0ee7f41..a2cd70c 100644
--- a/src/core/utils.ts
+++ b/src/core/utils.ts
@@ -1,4 +1,4 @@
-import type { PropDef, PropTypesFromTable } from './props.js';
+import type { PropDef, PropTypesFromTable } from './props.ts';
 import type { LatLngBoundsExpression } from 'leaflet';
 
 // Parses an HTML attribute string into a typed JS value:
diff --git a/src/core/with-props.ts b/src/core/with-props.ts
index 23720e2..0ab482d 100644
--- a/src/core/with-props.ts
+++ b/src/core/with-props.ts
@@ -1,5 +1,5 @@
-import type { PropDef, PropTypesFromTable } from './props.js';
-import { definePropAccessors } from './utils.js';
+import type { PropDef, PropTypesFromTable } from './props.ts';
+import { definePropAccessors } from './utils.ts';
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 type Ctor<T = object> = new (...args: any[]) => T;
diff --git a/src/index.ts b/src/index.ts
index 67ce946..669fd29 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,26 +1,26 @@
-export * from './core/utils.js';
-export * from './core/with-props.js';
-export * from './core/path-style.js';
-export * from './core/register.js';
-export * from './core/props.js';
-export * from './components/leaflet-map.js';
-export * from './components/leaflet-marker.js';
-export * from './components/leaflet-circle.js';
-export * from './components/leaflet-circle-marker.js';
-export * from './components/leaflet-line.js';
-export * from './components/leaflet-polygon.js';
-export * from './components/leaflet-polyline.js';
-export * from './components/leaflet-rectangle.js';
-export * from './components/leaflet-tile-layer.js';
-export * from './components/leaflet-tile-layer-wms.js';
-export * from './components/leaflet-image-overlay.js';
-export * from './components/leaflet-video-overlay.js';
-export * from './components/leaflet-svg-overlay.js';
-export * from './components/leaflet-layer-group.js';
-export * from './components/leaflet-feature-group.js';
-export * from './components/leaflet-geojson.js';
-export * from './components/leaflet-control-zoom.js';
-export * from './components/leaflet-control-attribution.js';
-export * from './components/leaflet-control-scale.js';
-export * from './components/leaflet-popup.js';
-export * from './components/leaflet-tooltip.js';
+export * from './core/utils.ts';
+export * from './core/with-props.ts';
+export * from './core/path-style.ts';
+export * from './core/register.ts';
+export * from './core/props.ts';
+export * from './components/leaflet-map.ts';
+export * from './components/leaflet-marker.ts';
+export * from './components/leaflet-circle.ts';
+export * from './components/leaflet-circle-marker.ts';
+export * from './components/leaflet-line.ts';
+export * from './components/leaflet-polygon.ts';
+export * from './components/leaflet-polyline.ts';
+export * from './components/leaflet-rectangle.ts';
+export * from './components/leaflet-tile-layer.ts';
+export * from './components/leaflet-tile-layer-wms.ts';
+export * from './components/leaflet-image-overlay.ts';
+export * from './components/leaflet-video-overlay.ts';
+export * from './components/leaflet-svg-overlay.ts';
+export * from './components/leaflet-layer-group.ts';
+export * from './components/leaflet-feature-group.ts';
+export * from './components/leaflet-geojson.ts';
+export * from './components/leaflet-control-zoom.ts';
+export * from './components/leaflet-control-attribution.ts';
+export * from './components/leaflet-control-scale.ts';
+export * from './components/leaflet-popup.ts';
+export * from './components/leaflet-tooltip.ts';
diff --git a/tsconfig.json b/tsconfig.json
index 3433f3c..cd345d0 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -13,6 +13,8 @@
     "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true,
     "isolatedModules": true,
+    "allowImportingTsExtensions": true,
+    "rewriteRelativeImportExtensions": true,
   },
   "include": ["src/**/*"]
 }