diff --git a/eslint.config.base.js b/eslint.config.base.js
index ea98b80e8..bc8b40101 100644
--- a/eslint.config.base.js
+++ b/eslint.config.base.js
@@ -822,6 +822,7 @@ export function createConfig(opts = {}) {
           '@typescript-eslint/no-unnecessary-parameter-property-assignment':
             'warn',
           '@typescript-eslint/no-unnecessary-qualifier': 'warn',
+          '@typescript-eslint/no-unnecessary-type-arguments': 'warn', // downgrade
           '@typescript-eslint/no-unsafe-argument': 'warn',
           '@typescript-eslint/no-unsafe-assignment': 'off', // too tricky to fix when `any` is declared externally (JSON.parse, Array.isArray, etc.)
           '@typescript-eslint/no-unused-vars': [
diff --git a/packages/app/src/vis-packs/core/hooks.ts b/packages/app/src/vis-packs/core/hooks.ts
index 1cd2a34f7..1f6b36b2c 100644
--- a/packages/app/src/vis-packs/core/hooks.ts
+++ b/packages/app/src/vis-packs/core/hooks.ts
@@ -2,13 +2,14 @@ import { createMemo } from '@h5web/shared/createMemo';
 import { assertDatasetValue, isDefined } from '@h5web/shared/guards';
 import {
   type ArrayShape,
+  type ArrayValue,
   type Dataset,
   type ScalarShape,
   type Value,
 } from '@h5web/shared/hdf5-models';
 import { type NumArray } from '@h5web/shared/vis-models';
 import { castArray } from '@h5web/shared/vis-utils';
-import { type NdArray, type TypedArray } from 'ndarray';
+import { type NdArray } from 'ndarray';
 import { useMemo } from 'react';
 
 import { type DimensionMapping } from '../../dimension-mapper/models';
@@ -100,29 +101,29 @@ export function useDatasetValues<D extends Dataset<ArrayShape | ScalarShape>>(
   });
 }
 
-export function useBaseArray<T extends unknown[] | TypedArray | undefined>(
+export function useBaseArray<T extends ArrayValue | undefined>(
   value: T,
   rawDims: number[],
-): T extends unknown[] | TypedArray ? NdArray<T> : undefined;
+): T extends ArrayValue ? NdArray<T> : undefined;
 
 export function useBaseArray(
-  value: unknown[] | TypedArray | undefined,
+  value: ArrayValue | undefined,
   rawDims: number[],
-): NdArray<unknown[] | TypedArray> | undefined {
+): NdArray<ArrayValue> | undefined {
   return useMemo(() => getBaseArray(value, rawDims), [value, rawDims]);
 }
 
-export function useMappedArray<T extends unknown[] | TypedArray | undefined>(
+export function useMappedArray<T extends ArrayValue | undefined>(
   value: T,
   dims: number[],
   mapping: DimensionMapping,
-): T extends unknown[] | TypedArray ? NdArray<T> : undefined;
+): T extends ArrayValue ? NdArray<T> : undefined;
 
 export function useMappedArray(
-  value: unknown[] | TypedArray | undefined,
+  value: ArrayValue | undefined,
   dims: number[],
   mapping: DimensionMapping,
-): NdArray<unknown[] | TypedArray> | undefined {
+): NdArray<ArrayValue> | undefined {
   const baseArray = useBaseArray(value, dims);
 
   return useMemo(() => applyMapping(baseArray, mapping), [baseArray, mapping]);
diff --git a/packages/app/src/vis-packs/core/utils.ts b/packages/app/src/vis-packs/core/utils.ts
index 1e6ef9545..c270d1541 100644
--- a/packages/app/src/vis-packs/core/utils.ts
+++ b/packages/app/src/vis-packs/core/utils.ts
@@ -11,7 +11,7 @@ import {
   type NumArray,
 } from '@h5web/shared/vis-models';
 import { createArrayFromView } from '@h5web/shared/vis-utils';
-import ndarray, { type NdArray, type TypedArray } from 'ndarray';
+import ndarray, { type NdArray } from 'ndarray';
 
 import { type DimensionMapping } from '../../dimension-mapper/models';
 import { isAxis } from '../../dimension-mapper/utils';
@@ -32,29 +32,27 @@ export const INTERACTIONS_WITH_AXIAL_ZOOM = [
   { shortcut: 'Ctrl+Shift+Drag', description: 'Select to zoom in Y' },
 ];
 
-export function getBaseArray<T extends unknown[] | TypedArray | undefined>(
+export function getBaseArray<T extends ArrayValue | undefined>(
   value: T,
   rawDims: number[],
-): T extends unknown[] | TypedArray ? NdArray<T> : undefined;
+): T extends ArrayValue ? NdArray<T> : undefined;
 
 export function getBaseArray(
-  value: unknown[] | TypedArray | undefined,
+  value: ArrayValue | undefined,
   rawDims: number[],
-): NdArray<unknown[] | TypedArray> | undefined {
+): NdArray<ArrayValue> | undefined {
   return value && ndarray(value, rawDims);
 }
 
-export function applyMapping<
-  T extends NdArray<unknown[] | TypedArray> | undefined,
->(
+export function applyMapping<T extends NdArray<ArrayValue> | undefined>(
   baseArray: T,
   mapping: (number | Axis | ':')[],
-): T extends NdArray<unknown[] | TypedArray> ? T : undefined;
+): T extends NdArray<ArrayValue> ? T : undefined;
 
 export function applyMapping(
-  baseArray: NdArray<unknown[] | TypedArray> | undefined,
+  baseArray: NdArray<ArrayValue> | undefined,
   mapping: (number | Axis | ':')[],
-): NdArray<unknown[] | TypedArray> | undefined {
+): NdArray<ArrayValue> | undefined {
   if (!baseArray) {
     return undefined;
   }
@@ -95,12 +93,16 @@ export function getImageInteractions(keepRatio: boolean): InteractionInfo[] {
   return keepRatio ? BASE_INTERACTIONS : INTERACTIONS_WITH_AXIAL_ZOOM;
 }
 
+function isBoolArray(val: ArrayValue<NumericLikeType>): val is boolean[] {
+  return Array.isArray(val) && typeof val[0] === 'boolean';
+}
+
 export function toNumArray(arr: ArrayValue<NumericLikeType>): NumArray {
-  if (typeof arr[0] === 'boolean') {
+  if (isBoolArray(arr)) {
     return arr.map((val) => (val ? 1 : 0));
   }
 
-  return arr as NumArray;
+  return arr;
 }
 
 const TYPE_STRINGS: Record<NumericLikeType['class'], string> = {
diff --git a/packages/shared/src/guards.ts b/packages/shared/src/guards.ts
index 132e79518..38be36593 100644
--- a/packages/shared/src/guards.ts
+++ b/packages/shared/src/guards.ts
@@ -142,14 +142,6 @@ export function isTypedArray(val: unknown): val is TypedArray {
   );
 }
 
-export function assertArrayOrTypedArray(
-  val: unknown,
-): asserts val is unknown[] | TypedArray {
-  if (!Array.isArray(val) && !isTypedArray(val)) {
-    throw new TypeError('Expected array or typed array');
-  }
-}
-
 export function isGroup(entity: Entity): entity is Group {
   return entity.kind === EntityKind.Group;
 }
@@ -431,7 +423,7 @@ export function isComplexValue(
 function assertPrimitiveValue(
   type: DType,
   value: unknown,
-): asserts value is Primitive<DType> {
+): asserts value is Primitive {
   if (isNumericType(type)) {
     assertNum(value);
   } else if (isStringType(type)) {
@@ -457,7 +449,9 @@ export function assertDatasetValue<D extends Dataset<ScalarShape | ArrayShape>>(
   if (hasScalarShape(dataset)) {
     assertPrimitiveValue(type, value);
   } else {
-    assertArrayOrTypedArray(value);
+    if (!Array.isArray(value) && !isTypedArray(value)) {
+      throw new TypeError('Expected array or typed array');
+    }
 
     if (value.length > 0) {
       assertPrimitiveValue(type, value[0]);
diff --git a/packages/shared/src/hdf5-models.ts b/packages/shared/src/hdf5-models.ts
index c695f6366..955a35066 100644
--- a/packages/shared/src/hdf5-models.ts
+++ b/packages/shared/src/hdf5-models.ts
@@ -207,21 +207,19 @@ export interface UnknownType {
 /* ----------------- */
 /* ----- VALUE ----- */
 
-export type Primitive<T extends DType> = T extends NumericType | EnumType
-  ? number
+export type Primitive<T extends DType = DType> = T extends NumericLikeType
+  ? number | (T extends BooleanType ? boolean : never) // let providers choose how to return booleans
   : T extends StringType
     ? string
-    : T extends BooleanType
-      ? number | boolean // let providers choose
-      : T extends ComplexType
-        ? H5WebComplex
-        : T extends CompoundType<infer TFields>
-          ? Primitive<TFields>[]
-          : unknown;
-
-export type ArrayValue<T extends DType> =
-  | Primitive<T>[]
-  | (T extends NumericLikeType ? TypedArray : never);
+    : T extends ComplexType
+      ? H5WebComplex
+      : T extends CompoundType<infer TFields>
+        ? Primitive<TFields>[]
+        : unknown;
+
+export type ArrayValue<T extends DType = DType> = T extends NumericLikeType
+  ? TypedArray | number[] | (T extends BooleanType ? boolean[] : never) // don't use `Primitive` to avoid `(number | boolean)[]`
+  : Primitive<T>[];
 
 export type Value<D extends Dataset> =
   D extends Dataset<infer S, infer T>
diff --git a/packages/shared/src/mock-values.ts b/packages/shared/src/mock-values.ts
index 49985fc71..ce1da3f7d 100644
--- a/packages/shared/src/mock-values.ts
+++ b/packages/shared/src/mock-values.ts
@@ -2,7 +2,7 @@
 import { range } from 'd3-array';
 import ndarray, { type NdArray } from 'ndarray';
 
-import { type ArrayValue, type DType, type H5WebComplex } from './hdf5-models';
+import { type ArrayValue, type H5WebComplex } from './hdf5-models';
 import { cplx } from './hdf5-utils';
 
 const range1 = () => range(-20, 21);
@@ -276,4 +276,4 @@ export const mockValues = {
     ndarray(range1().map((val) => Math.cos((val * 3.14) / 40))),
   Y_scatter: () =>
     ndarray(range1().map((_, i) => ((i % 10) + (i % 5)) / 123_456)),
-} satisfies Record<string, () => NdArray<ArrayValue<DType>>>;
+} satisfies Record<string, () => NdArray<ArrayValue>>;
diff --git a/packages/shared/src/vis-utils.ts b/packages/shared/src/vis-utils.ts
index f1ae4999e..8dde43342 100644
--- a/packages/shared/src/vis-utils.ts
+++ b/packages/shared/src/vis-utils.ts
@@ -1,9 +1,10 @@
 import { format } from 'd3-format';
-import ndarray, { type NdArray, type TypedArray } from 'ndarray';
+import ndarray, { type NdArray } from 'ndarray';
 import { assign } from 'ndarray-ops';
 
 import { assertLength, isNdArray } from './guards';
 import {
+  type ArrayValue,
   type BooleanType,
   type ComplexType,
   type EnumType,
@@ -101,7 +102,7 @@ export function toTypedNdArray<T extends TypedArrayConstructor>(
   return ndarray(Constructor.from(arr.data) as InstanceType<T>, arr.shape);
 }
 
-export function createArrayFromView<T extends TypedArray | unknown[]>(
+export function createArrayFromView<T extends ArrayValue>(
   view: NdArray<T>,
 ): NdArray<T> {
   const { data, size, shape } = view;