diff --git a/packages/openapi-zod-ts/src/__tests__/client.test.ts b/packages/openapi-zod-ts/src/__tests__/client.test.ts
index 2ac609f..c4e0164 100644
--- a/packages/openapi-zod-ts/src/__tests__/client.test.ts
+++ b/packages/openapi-zod-ts/src/__tests__/client.test.ts
@@ -989,6 +989,67 @@ describe('coverage: queryParamType edge cases (lines 70, 81)', () => {
     const out = generateClient(spec as OpenAPIV3_1.Document).content
     expect(out).toContain('filter?: unknown')
   })
+
+  it('nullable array query param (type: ["array","null"]) with integer items → number[] type (#303)', () => {
+    // Regression: type: ['array', 'null'] previously fell through to primitiveToTs('array')
+    // which returned 'unknown'. The fix treats it identically to type: 'array'.
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/reports': {
+          get: {
+            operationId: 'listReports',
+            parameters: [
+              {
+                name: 'ids[]',
+                in: 'query',
+                schema: { type: ['array', 'null'], items: { type: 'integer' } } as any,
+              },
+            ],
+            responses: {
+              '200': { content: { 'application/json': { schema: { type: 'string' } } } },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    // Type must be number[], not unknown (toPropertyKey wraps the bracket name in single quotes)
+    expect(out).toContain("'ids[]'?: number[]")
+    // Serialization must use append loop, not set
+    expect(out).toContain("searchParams.append('ids[]'")
+    expect(out).not.toContain("searchParams.set('ids[]'")
+  })
+
+  it('nullable array query param (type: ["array","null"]) with string items → string[] type (#303)', () => {
+    // Non-integer items: nullable array query param should be string[], not unknown.
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/search': {
+          get: {
+            operationId: 'searchItems',
+            parameters: [
+              {
+                name: 'tags',
+                in: 'query',
+                schema: { type: ['array', 'null'], items: { type: 'string' } } as any,
+              },
+            ],
+            responses: {
+              '200': { content: { 'application/json': { schema: { type: 'string' } } } },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    expect(out).toContain('tags?: string[]')
+    expect(out).toContain("searchParams.append('tags'")
+    expect(out).not.toContain("searchParams.set('tags'")
+  })
 })
 
 describe('coverage: deriveOperationName via no-operationId spec (lines 101-123, 540)', () => {
diff --git a/packages/openapi-zod-ts/src/plugins/client.ts b/packages/openapi-zod-ts/src/plugins/client.ts
index 055e602..85e388a 100644
--- a/packages/openapi-zod-ts/src/plugins/client.ts
+++ b/packages/openapi-zod-ts/src/plugins/client.ts
@@ -247,7 +247,17 @@ function queryParamType(schema: SchemaObject | ReferenceObject | undefined): str
   // non-null primitive and drop the null member.
   if (Array.isArray(s.type)) {
     const nonNull = (s.type as string[]).filter((t) => t !== 'null')
-    if (nonNull.length === 1) return primitiveToTs(nonNull[0])
+    if (nonNull.length === 1) {
+      // type: ['array', 'null'] — nullable array: treat identically to type: 'array'
+      if (nonNull[0] === 'array') {
+        const items = (s as OpenAPIV3_1.ArraySchemaObject).items as SchemaObject | undefined
+        if (items !== undefined && (items.type === 'integer' || items.type === 'number')) {
+          return 'number[]'
+        }
+        return 'string[]'
+      }
+      return primitiveToTs(nonNull[0])
+    }
     return 'string'
   }
   if (s.type === 'array') {