diff --git a/biome.jsonc b/biome.jsonc
index e6e6e1b6080..bc4194f5489 100644
--- a/biome.jsonc
+++ b/biome.jsonc
@@ -50,8 +50,7 @@
 				"noNonNullAssertion": "off"
 			},
 			"performance": {
-				"noDelete": "off",
-				"noAccumulatingSpread": "off"
+				"noDelete": "off"
 			},
 			"security": {
 				"noGlobalEval": "off"
diff --git a/packages/rspack-test-tools/src/processor/multi.ts b/packages/rspack-test-tools/src/processor/multi.ts
index 187b113c000..e8fe16f4de8 100644
--- a/packages/rspack-test-tools/src/processor/multi.ts
+++ b/packages/rspack-test-tools/src/processor/multi.ts
@@ -43,40 +43,44 @@ export class MultiTaskProcessor<T extends ECompilerType>
 				if (typeof _multiOptions.findBundle !== "function") {
 					return [];
 				}
-				return this.multiCompilerOptions.reduce<string[]>(
-					(res, compilerOptions, index) => {
-						const curBundles = _multiOptions.findBundle!(
-							index,
-							context,
-							compilerOptions
-						);
 
-						const bundles = Array.isArray(curBundles)
-							? curBundles
-							: curBundles
-								? [curBundles]
-								: [];
+				const result: string[] = [];
+				const multiFileIndexMap: Record<string, number[]> =
+					context.getValue(_multiOptions.name, "multiFileIndexMap") || {};
+				for (const [
+					index,
+					compilerOptions
+				] of this.multiCompilerOptions.entries()) {
+					const curBundles = _multiOptions.findBundle!(
+						index,
+						context,
+						compilerOptions
+					);
 
-						const multiFileIndexMap: Record<string, number[]> =
-							context.getValue(_multiOptions.name, "multiFileIndexMap") || {};
-						for (const bundle of bundles) {
-							multiFileIndexMap[bundle] = [
-								...(multiFileIndexMap[bundle] || []),
-								index
-							];
+					const bundles = Array.isArray(curBundles)
+						? curBundles
+						: curBundles
+							? [curBundles]
+							: [];
+
+					for (const bundle of bundles) {
+						if (multiFileIndexMap[bundle]) {
+							multiFileIndexMap[bundle].push(index);
+						} else {
+							multiFileIndexMap[bundle] = [index];
 						}
-						context.setValue(
-							_multiOptions.name,
-							"multiFileIndexMap",
-							multiFileIndexMap
-						);
-						return [
-							...res,
-							...(Array.isArray(bundles) ? bundles : bundles ? [bundles] : [])
-						];
-					},
-					[]
+					}
+
+					result.push(...bundles);
+				}
+
+				context.setValue(
+					_multiOptions.name,
+					"multiFileIndexMap",
+					multiFileIndexMap
 				);
+
+				return result;
 			},
 			name: _multiOptions.name
 		});
diff --git a/packages/rspack-test-tools/src/test/context.ts b/packages/rspack-test-tools/src/test/context.ts
index fecf3afc9f1..0f4b9996d73 100644
--- a/packages/rspack-test-tools/src/test/context.ts
+++ b/packages/rspack-test-tools/src/test/context.ts
@@ -121,10 +121,7 @@ export class TestContext implements ITestContext {
 		if (name) {
 			return this.errors.get(name) || [];
 		}
-		return Array.from(this.errors.values()).reduce(
-			(res, arr) => [...res, ...arr],
-			[]
-		);
+		return Array.prototype.concat(...this.errors.values());
 	}
 	clearError(name?: string) {
 		if (name) {
diff --git a/packages/rspack/src/stats/StatsFactory.ts b/packages/rspack/src/stats/StatsFactory.ts
index 27c35a5fd3a..d2afed54461 100644
--- a/packages/rspack/src/stats/StatsFactory.ts
+++ b/packages/rspack/src/stats/StatsFactory.ts
@@ -171,12 +171,13 @@ export class StatsFactory {
 		});
 
 		const hooks = this.hooks;
-		this._caches = Object.keys(hooks).reduce((prev, curr) => {
-			return {
-				...prev,
-				[curr]: new Map()
-			};
-		}, {} as Cache);
+		const caches = {} as Cache;
+
+		for (const key of Object.keys(hooks)) {
+			caches[key as keyof Cache] = new Map();
+		}
+
+		this._caches = caches;
 		this._inCreate = false;
 	}