diff --git a/modules/carto/src/api/parse-map.ts b/modules/carto/src/api/parse-map.ts
index b1fadddae86..5a9ee028e9e 100644
--- a/modules/carto/src/api/parse-map.ts
+++ b/modules/carto/src/api/parse-map.ts
@@ -19,7 +19,7 @@ import {
   negateAccessor,
   getMaxMarkerSize
 } from './layer-map';
-import {assert} from '../utils';
+import {assert, getAuthFetchOptions} from '../utils';
 import {KeplerMapConfig, MapDataset, MapLayerConfig, VisualChannels} from './types';
 
 export type ParseMapResult = {
@@ -365,8 +365,8 @@ function createChannelProps(
   return result;
 }
 
-function createLoadOptions(accessToken: string) {
+function createLoadOptions(accessToken: string | undefined) {
   return {
-    loadOptions: {core: {fetch: {headers: {Authorization: `Bearer ${accessToken}`}}}}
+    loadOptions: {core: {fetch: getAuthFetchOptions(accessToken)}}
   };
 }
diff --git a/modules/carto/src/layers/cluster-tile-layer.ts b/modules/carto/src/layers/cluster-tile-layer.ts
index 9ff15d16e2a..7f087a49870 100644
--- a/modules/carto/src/layers/cluster-tile-layer.ts
+++ b/modules/carto/src/layers/cluster-tile-layer.ts
@@ -5,6 +5,7 @@
 /* eslint-disable no-shadow */
 
 import {GeoJsonLayer, GeoJsonLayerProps} from '@deck.gl/layers';
+import {getAuthFetchOptions} from '../utils';
 import {
   TileLayer,
   _Tile2DHeader as Tile2DHeader,
@@ -292,7 +293,7 @@ export default class ClusterTileLayer<
     const tileJSON = this.props.data as TilejsonResult;
     const scheme = tileJSON && 'scheme' in tileJSON ? tileJSON.scheme : 'quadbin';
     return mergeLoadOptions(super.getLoadOptions(), {
-      fetch: {headers: {Authorization: `Bearer ${tileJSON.accessToken}`}},
+      fetch: getAuthFetchOptions(tileJSON.accessToken),
       cartoSpatialTile: {scheme}
     });
   }
diff --git a/modules/carto/src/layers/h3-tile-layer.ts b/modules/carto/src/layers/h3-tile-layer.ts
index 049acf67ee2..7a2577c0aa9 100644
--- a/modules/carto/src/layers/h3-tile-layer.ts
+++ b/modules/carto/src/layers/h3-tile-layer.ts
@@ -3,6 +3,7 @@
 // Copyright (c) vis.gl contributors
 
 import {CompositeLayer, CompositeLayerProps, DefaultProps} from '@deck.gl/core';
+import {getAuthFetchOptions} from '../utils';
 import {H3HexagonLayer, H3HexagonLayerProps} from '@deck.gl/geo-layers';
 import H3Tileset2D, {getHexagonResolution} from './h3-tileset-2d';
 import SpatialIndexTileLayer, {SpatialIndexTileLayerProps} from './spatial-index-tile-layer';
@@ -49,7 +50,7 @@ export default class H3TileLayer<DataT = any, ExtraPropsT extends {} = {}> exten
   getLoadOptions(): any {
     const tileJSON = this.props.data as TilejsonResult;
     return mergeLoadOptions(super.getLoadOptions(), {
-      fetch: {headers: {Authorization: `Bearer ${tileJSON.accessToken}`}},
+      fetch: getAuthFetchOptions(tileJSON.accessToken),
       cartoSpatialTile: {scheme: 'h3'}
     });
   }
diff --git a/modules/carto/src/layers/quadbin-tile-layer.ts b/modules/carto/src/layers/quadbin-tile-layer.ts
index 3b3bce45bee..db2c306b5a5 100644
--- a/modules/carto/src/layers/quadbin-tile-layer.ts
+++ b/modules/carto/src/layers/quadbin-tile-layer.ts
@@ -3,6 +3,7 @@
 // Copyright (c) vis.gl contributors
 
 import {CompositeLayer, CompositeLayerProps, DefaultProps} from '@deck.gl/core';
+import {getAuthFetchOptions} from '../utils';
 import QuadbinLayer, {QuadbinLayerProps} from './quadbin-layer';
 import QuadbinTileset2D from './quadbin-tileset-2d';
 import SpatialIndexTileLayer, {SpatialIndexTileLayerProps} from './spatial-index-tile-layer';
@@ -45,7 +46,7 @@ export default class QuadbinTileLayer<
   getLoadOptions(): any {
     const tileJSON = this.props.data as TilejsonResult;
     return mergeLoadOptions(super.getLoadOptions(), {
-      fetch: {headers: {Authorization: `Bearer ${tileJSON.accessToken}`}},
+      fetch: getAuthFetchOptions(tileJSON.accessToken),
       cartoSpatialTile: {scheme: 'quadbin'}
     });
   }
diff --git a/modules/carto/src/layers/raster-tile-layer.ts b/modules/carto/src/layers/raster-tile-layer.ts
index a33a1c23430..b5a614d2bf8 100644
--- a/modules/carto/src/layers/raster-tile-layer.ts
+++ b/modules/carto/src/layers/raster-tile-layer.ts
@@ -11,6 +11,7 @@ import {
   LayersList
 } from '@deck.gl/core';
 import RasterLayer, {RasterLayerProps} from './raster-layer';
+import {getAuthFetchOptions} from '../utils';
 import QuadbinTileset2D from './quadbin-tileset-2d';
 import type {TilejsonResult} from '@carto/api-client';
 import {TilejsonPropType, mergeLoadOptions} from './utils';
@@ -66,7 +67,7 @@ export default class RasterTileLayer<
   getLoadOptions(): any {
     const tileJSON = this.props.data as TilejsonResult;
     return mergeLoadOptions(super.getLoadOptions(), {
-      fetch: {headers: {Authorization: `Bearer ${tileJSON.accessToken}`}}
+      fetch: getAuthFetchOptions(tileJSON.accessToken)
     });
   }
 
diff --git a/modules/carto/src/layers/vector-tile-layer.ts b/modules/carto/src/layers/vector-tile-layer.ts
index b10a6c8a36c..cc6b36ce7cd 100644
--- a/modules/carto/src/layers/vector-tile-layer.ts
+++ b/modules/carto/src/layers/vector-tile-layer.ts
@@ -24,7 +24,7 @@ import type {TilejsonResult} from '@carto/api-client';
 import {TilejsonPropType, mergeLoadOptions, mergeBoundaryData} from './utils';
 import {DEFAULT_TILE_SIZE} from '../constants';
 import {createPointsFromLines, createPointsFromPolygons} from './label-utils';
-import {createEmptyBinary} from '../utils';
+import {createEmptyBinary, getAuthFetchOptions} from '../utils';
 import PointLabelLayer from './point-label-layer';
 
 const MVT_BBOX: GeoBoundingBox = {west: 0, east: 1, south: 0, north: 1};
@@ -89,7 +89,7 @@ export default class VectorTileLayer<
   getLoadOptions(): any {
     const tileJSON = this.props.data as TilejsonResult;
     return mergeLoadOptions(super.getLoadOptions(), {
-      fetch: {headers: {Authorization: `Bearer ${tileJSON.accessToken}`}},
+      fetch: getAuthFetchOptions(tileJSON.accessToken),
       gis: {format: 'binary'} // Use binary for MVT loading
     });
   }
diff --git a/modules/carto/src/utils.ts b/modules/carto/src/utils.ts
index cf34dc88376..de1469c2fed 100644
--- a/modules/carto/src/utils.ts
+++ b/modules/carto/src/utils.ts
@@ -150,3 +150,20 @@ export function copyNumericProps(
     targetProps[prop].value[targetIndex] = sourceProps[prop].value[sourceIndex];
   });
 }
+
+/**
+ * Fetch options carrying the CARTO Authorization header, or none when no
+ * access token is present — e.g. a source created with the api-client's
+ * session auth mode, where tile URLs are same-origin and authenticated by a
+ * cookie. Emitting `Bearer undefined` would defeat such server-side session
+ * handling, which engages only when the Authorization header is absent.
+ */
+export function getAuthFetchOptions(accessToken: string | undefined): {
+  headers?: Record<string, string>;
+  credentials?: RequestCredentials;
+} {
+  if (!accessToken) {
+    return {credentials: 'same-origin'};
+  }
+  return {headers: {Authorization: `Bearer ${accessToken}`}};
+}