diff --git a/examples/generated-rq/adyen-checkout/models.ts b/examples/generated-rq/adyen-checkout/models.ts
index 00d5bdb..522b34b 100644
--- a/examples/generated-rq/adyen-checkout/models.ts
+++ b/examples/generated-rq/adyen-checkout/models.ts
@@ -365,7 +365,7 @@ export interface Agency {
 
 export interface Airline {
   agency?: Agency
-  boardingFee?: bigint
+  boardingFee?: number /* int64, precision limited to 2^53-1 */
   code?: string
   computerizedReservationSystem?: string
   customerReferenceNumber?: string
@@ -396,12 +396,12 @@ export interface AmazonPayDetails {
 
 export interface Amount {
   currency: string
-  value: bigint
+  value: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface Amounts {
   currency: string
-  values: bigint[]
+  values: number /* int64, precision limited to 2^53-1 */[]
 }
 
 export interface AncvDetails {
@@ -1199,9 +1199,9 @@ export interface DokuDetails {
 export interface Donation {
   currency: string
   donationType: string
-  maxRoundupAmount?: bigint
+  maxRoundupAmount?: number /* int64, precision limited to 2^53-1 */
   type: string
-  values?: bigint[]
+  values?: number /* int64, precision limited to 2^53-1 */[]
 }
 
 export interface DonationCampaign {
@@ -1530,12 +1530,12 @@ export interface Item {
 export interface ItemDetailLine {
   commodityCode?: string
   description?: string
-  discountAmount?: bigint
+  discountAmount?: number /* int64, precision limited to 2^53-1 */
   productCode?: string
-  quantity?: bigint
-  totalAmount?: bigint
+  quantity?: number /* int64, precision limited to 2^53-1 */
+  totalAmount?: number /* int64, precision limited to 2^53-1 */
   unitOfMeasure?: string
-  unitPrice?: bigint
+  unitPrice?: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface KlarnaDetails {
@@ -1572,7 +1572,7 @@ export interface Leg {
   classOfTravel?: string
   dateOfTravel?: string /* date-time */
   departureAirportCode?: string
-  departureTax?: bigint
+  departureTax?: number /* int64, precision limited to 2^53-1 */
   destinationAirportCode?: string
   fareBasisCode?: string
   flightNumber?: string
@@ -1582,17 +1582,17 @@ export interface Leg {
 export interface LevelTwoThree {
   customerReferenceNumber?: string
   destination?: Destination
-  dutyAmount?: bigint
-  freightAmount?: bigint
+  dutyAmount?: number /* int64, precision limited to 2^53-1 */
+  freightAmount?: number /* int64, precision limited to 2^53-1 */
   itemDetailLines?: ItemDetailLine[]
   orderDate?: string /* date */
   shipFromPostalCode?: string
-  totalTaxAmount?: bigint
+  totalTaxAmount?: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface LineItem {
-  amountExcludingTax?: bigint
-  amountIncludingTax?: bigint
+  amountExcludingTax?: number /* int64, precision limited to 2^53-1 */
+  amountIncludingTax?: number /* int64, precision limited to 2^53-1 */
   brand?: string
   color?: string
   description?: string
@@ -1602,12 +1602,12 @@ export interface LineItem {
   manufacturer?: string
   marketplaceSellerId?: string
   productUrl?: string
-  quantity?: bigint
+  quantity?: number /* int64, precision limited to 2^53-1 */
   receiverEmail?: string
   size?: string
   sku?: string
-  taxAmount?: bigint
-  taxPercentage?: bigint
+  taxAmount?: number /* int64, precision limited to 2^53-1 */
+  taxPercentage?: number /* int64, precision limited to 2^53-1 */
   upc?: string
 }
 
@@ -2550,7 +2550,7 @@ export interface PixPayByBankDetails {
 
 export interface PixPayByBankRiskSignals {
   confidenceScore?: ConfidenceScore
-  elapsedTimeSinceBoot?: bigint
+  elapsedTimeSinceBoot?: number /* int64, precision limited to 2^53-1 */
   isRootedDevice?: boolean
   language?: string
   osVersion?: string
@@ -2876,7 +2876,7 @@ export interface Split {
 
 export interface SplitAmount {
   currency?: string
-  value: bigint
+  value: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface StandalonePaymentCancelRequest {
@@ -3018,7 +3018,7 @@ export interface SubMerchantInfo {
 }
 
 export interface Surcharge {
-  value: bigint
+  value: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface TaxTotal {
diff --git a/examples/generated-rq/adyen-legal-entity/models.ts b/examples/generated-rq/adyen-legal-entity/models.ts
index 347bf8f..51b1ad5 100644
--- a/examples/generated-rq/adyen-legal-entity/models.ts
+++ b/examples/generated-rq/adyen-legal-entity/models.ts
@@ -46,7 +46,7 @@ export interface Address {
 
 export interface Amount {
   currency?: string
-  value?: bigint
+  value?: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface Attachment {
diff --git a/examples/generated-rq/devto/models.ts b/examples/generated-rq/devto/models.ts
index 5617dc9..343c4d8 100644
--- a/examples/generated-rq/devto/models.ts
+++ b/examples/generated-rq/devto/models.ts
@@ -36,11 +36,11 @@ export interface ArticleIndex {
 
 export interface VideoArticle {
   type_of?: string
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   path?: string
   cloudinary_video_url?: string
   title?: string
-  user_id?: bigint
+  user_id?: number /* int64, precision limited to 2^53-1 */
   video_duration_in_minutes?: string
   video_source_url?: string
   user?: {
@@ -78,13 +78,13 @@ export interface Organization {
 }
 
 export interface FollowedTag {
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   name: string
   points: number
 }
 
 export interface Tag {
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   name?: string
   bg_color_hex?: string | null
   text_color_hex?: string | null
@@ -138,7 +138,7 @@ export interface SharedOrganization {
 
 export interface User {
   type_of?: string
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   username?: string
   name?: string
   summary?: string | null
@@ -152,7 +152,7 @@ export interface User {
 
 export interface ExtendedUser {
   type_of?: string
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   username?: string
   name?: string
   summary?: string | null
@@ -168,7 +168,7 @@ export interface ExtendedUser {
 
 export interface MyUser {
   type_of?: string
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   username?: string
   name?: string
   summary?: string | null
@@ -261,7 +261,7 @@ export interface SegmentUserIds {
 }
 
 export interface AgentSessionIndex {
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   slug: string
   title: string
   tool_name: string
@@ -273,7 +273,7 @@ export interface AgentSessionIndex {
 }
 
 export interface AgentSessionShow {
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   slug: string
   title: string
   tool_name: string
@@ -290,7 +290,7 @@ export interface AgentSessionShow {
 
 export interface PollOption {
   type_of: 'poll_option'
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   markdown: string | null
   processed_html: string | null
   position: number
@@ -300,7 +300,7 @@ export interface PollOption {
 
 export interface Poll {
   type_of: 'poll'
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   prompt_markdown: string | null
   prompt_html: string | null
   poll_type_of: 'single_choice' | 'multiple_choice' | 'scale' | 'text_input'
@@ -317,7 +317,7 @@ export interface Poll {
 
 export interface Survey {
   type_of: 'survey'
-  id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
   title: string
   slug: string
   survey_type_of: 'community_pulse' | 'industry' | 'fun'
@@ -334,10 +334,10 @@ export type SurveyWithPolls = Survey & {
 
 export interface PollVote {
   type_of: 'poll_vote'
-  id: bigint
-  poll_id: bigint
-  poll_option_id: bigint
-  user_id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
+  poll_id: number /* int64, precision limited to 2^53-1 */
+  poll_option_id: number /* int64, precision limited to 2^53-1 */
+  user_id: number /* int64, precision limited to 2^53-1 */
   user_email: string
   session_start: number
   created_at: string /* date-time */
@@ -345,9 +345,9 @@ export interface PollVote {
 
 export interface PollTextResponse {
   type_of: 'poll_text_response'
-  id: bigint
-  poll_id: bigint
-  user_id: bigint
+  id: number /* int64, precision limited to 2^53-1 */
+  poll_id: number /* int64, precision limited to 2^53-1 */
+  user_id: number /* int64, precision limited to 2^53-1 */
   user_email: string
   text_content: string
   session_start: number
diff --git a/examples/generated-rq/openai/models.ts b/examples/generated-rq/openai/models.ts
index 9e4f92b..2e34bd2 100644
--- a/examples/generated-rq/openai/models.ts
+++ b/examples/generated-rq/openai/models.ts
@@ -41,7 +41,7 @@ export interface AssignedRoleDetails {
   predefined_role: boolean
   description: string | null
   created_at: number | null
-  updated_at: bigint | null
+  updated_at: number /* int64, precision limited to 2^53-1 */ | null
   created_by: string | null
   created_by_user_obj: Record<string, unknown> | null
   metadata: Record<string, unknown> | null
@@ -682,7 +682,7 @@ export interface Batch {
 
 export interface BatchFileExpirationAfter {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface Certificate {
@@ -1288,7 +1288,7 @@ export interface CreateCompletionRequest {
   max_tokens?: number | null
   n?: number | null
   presence_penalty?: number | null
-  seed?: bigint | null
+  seed?: number /* int64, precision limited to 2^53-1 */ | null
   stop?: StopConfiguration
   stream?: boolean | null
   stream_options?: ChatCompletionStreamOptions
@@ -2302,7 +2302,7 @@ export interface EvalStoredCompletionsSource {
 
 export interface FileExpirationAfter {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface FilePath {
@@ -4498,7 +4498,7 @@ export interface RealtimeConversationItemWithReference {
 export interface RealtimeCreateClientSecretRequest {
   expires_after?: {
     anchor?: 'created_at'
-    seconds?: bigint
+    seconds?: number /* int64, precision limited to 2^53-1 */
   }
   session?: RealtimeSessionCreateRequestGA | RealtimeTranscriptionSessionCreateRequestGA
 }
@@ -5491,7 +5491,7 @@ export interface RealtimeTranslationClientEventSessionUpdate {
 export interface RealtimeTranslationClientSecretCreateRequest {
   expires_after?: {
     anchor?: 'created_at'
-    seconds?: bigint
+    seconds?: number /* int64, precision limited to 2^53-1 */
   }
   session: RealtimeTranslationSessionCreateRequest
 }
@@ -6944,7 +6944,7 @@ export interface UsageAudioSpeechesResult {
 
 export interface UsageAudioTranscriptionsResult {
   object: 'organization.usage.audio_transcriptions.result'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
   num_model_requests: number
   project_id?: string | null
   user_id?: string | null
@@ -8641,7 +8641,7 @@ export interface WorkflowParam {
 
 export interface ExpiresAfterParam {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface RateLimitsParam {
diff --git a/examples/generated-rq/petstore-3.0/client.ts b/examples/generated-rq/petstore-3.0/client.ts
index 8319eb0..a960764 100644
--- a/examples/generated-rq/petstore-3.0/client.ts
+++ b/examples/generated-rq/petstore-3.0/client.ts
@@ -182,7 +182,7 @@ export async function uploadFile(
 
 export async function getInventory(
   config?: Partial<ClientConfig>
-): Promise<Record<string, unknown>> {
+): Promise<Record<string, number>> {
   const res = await _request('GET', '/store/inventory', {}, config)
   return res.json()
 }
diff --git a/examples/generated-rq/petstore-3.0/models.ts b/examples/generated-rq/petstore-3.0/models.ts
index ca3e7ce..c427a86 100644
--- a/examples/generated-rq/petstore-3.0/models.ts
+++ b/examples/generated-rq/petstore-3.0/models.ts
@@ -1,8 +1,8 @@
 // This file is auto-generated by openapi-zod-ts - do not edit
 
 export interface Order {
-  id?: bigint
-  petId?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
+  petId?: number /* int64, precision limited to 2^53-1 */
   quantity?: number
   shipDate?: string /* date-time */
   status?: 'placed' | 'approved' | 'delivered'
@@ -10,12 +10,12 @@ export interface Order {
 }
 
 export interface Category {
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   name?: string
 }
 
 export interface User {
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   username?: string
   firstName?: string
   lastName?: string
@@ -26,12 +26,12 @@ export interface User {
 }
 
 export interface Tag {
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   name?: string
 }
 
 export interface Pet {
-  id?: bigint
+  id?: number /* int64, precision limited to 2^53-1 */
   name: string
   category?: Category
   photoUrls: string[]
diff --git a/examples/generated-rq/spotify/models.ts b/examples/generated-rq/spotify/models.ts
index 7b4d8b6..86541ba 100644
--- a/examples/generated-rq/spotify/models.ts
+++ b/examples/generated-rq/spotify/models.ts
@@ -70,7 +70,7 @@ export interface CurrentlyPlayingContextObject {
   repeat_state?: string
   shuffle_state?: boolean
   context?: ContextObject
-  timestamp?: bigint
+  timestamp?: number /* int64, precision limited to 2^53-1 */
   progress_ms?: number
   is_playing?: boolean
   item?: TrackObject | EpisodeObject
@@ -128,7 +128,7 @@ export interface AudioAnalysisObject {
     platform?: string
     detailed_status?: string
     status_code?: number
-    timestamp?: bigint
+    timestamp?: number /* int64, precision limited to 2^53-1 */
     analysis_time?: number
     input_process?: string
   }
@@ -672,7 +672,7 @@ export interface ExplicitContentSettingsObject {
 
 export interface CurrentlyPlayingObject {
   context?: ContextObject
-  timestamp?: bigint
+  timestamp?: number /* int64, precision limited to 2^53-1 */
   progress_ms?: number
   is_playing?: boolean
   item?: TrackObject | EpisodeObject
diff --git a/examples/generated/openai/models.ts b/examples/generated/openai/models.ts
index 9e4f92b..2e34bd2 100644
--- a/examples/generated/openai/models.ts
+++ b/examples/generated/openai/models.ts
@@ -41,7 +41,7 @@ export interface AssignedRoleDetails {
   predefined_role: boolean
   description: string | null
   created_at: number | null
-  updated_at: bigint | null
+  updated_at: number /* int64, precision limited to 2^53-1 */ | null
   created_by: string | null
   created_by_user_obj: Record<string, unknown> | null
   metadata: Record<string, unknown> | null
@@ -682,7 +682,7 @@ export interface Batch {
 
 export interface BatchFileExpirationAfter {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface Certificate {
@@ -1288,7 +1288,7 @@ export interface CreateCompletionRequest {
   max_tokens?: number | null
   n?: number | null
   presence_penalty?: number | null
-  seed?: bigint | null
+  seed?: number /* int64, precision limited to 2^53-1 */ | null
   stop?: StopConfiguration
   stream?: boolean | null
   stream_options?: ChatCompletionStreamOptions
@@ -2302,7 +2302,7 @@ export interface EvalStoredCompletionsSource {
 
 export interface FileExpirationAfter {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface FilePath {
@@ -4498,7 +4498,7 @@ export interface RealtimeConversationItemWithReference {
 export interface RealtimeCreateClientSecretRequest {
   expires_after?: {
     anchor?: 'created_at'
-    seconds?: bigint
+    seconds?: number /* int64, precision limited to 2^53-1 */
   }
   session?: RealtimeSessionCreateRequestGA | RealtimeTranscriptionSessionCreateRequestGA
 }
@@ -5491,7 +5491,7 @@ export interface RealtimeTranslationClientEventSessionUpdate {
 export interface RealtimeTranslationClientSecretCreateRequest {
   expires_after?: {
     anchor?: 'created_at'
-    seconds?: bigint
+    seconds?: number /* int64, precision limited to 2^53-1 */
   }
   session: RealtimeTranslationSessionCreateRequest
 }
@@ -6944,7 +6944,7 @@ export interface UsageAudioSpeechesResult {
 
 export interface UsageAudioTranscriptionsResult {
   object: 'organization.usage.audio_transcriptions.result'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
   num_model_requests: number
   project_id?: string | null
   user_id?: string | null
@@ -8641,7 +8641,7 @@ export interface WorkflowParam {
 
 export interface ExpiresAfterParam {
   anchor: 'created_at'
-  seconds: bigint
+  seconds: number /* int64, precision limited to 2^53-1 */
 }
 
 export interface RateLimitsParam {
diff --git a/examples/generated/petstore-3.0/client.ts b/examples/generated/petstore-3.0/client.ts
index e1fb681..972fe90 100644
--- a/examples/generated/petstore-3.0/client.ts
+++ b/examples/generated/petstore-3.0/client.ts
@@ -186,7 +186,7 @@ export async function uploadFile(
 
 export async function getInventory(
   config?: Partial<ClientConfig>
-): Promise<Record<string, unknown>> {
+): Promise<Record<string, number>> {
   const res = await _request('GET', '/store/inventory', {}, config)
   return res.json()
 }
diff --git a/packages/openapi-zod-ts/src/__tests__/client.test.ts b/packages/openapi-zod-ts/src/__tests__/client.test.ts
index b563116..8ee4929 100644
--- a/packages/openapi-zod-ts/src/__tests__/client.test.ts
+++ b/packages/openapi-zod-ts/src/__tests__/client.test.ts
@@ -251,6 +251,73 @@ describe('inline response schemas', () => {
   })
 })
 
+describe('error_body_type (#293): typed schema-less error bodies', () => {
+  const minimalSpec: OpenAPIV3_1.Document = {
+    openapi: '3.1.0',
+    info: { title: 'T', version: '1' },
+    paths: {
+      '/items': {
+        get: {
+          operationId: 'listItems',
+          responses: {
+            '200': { content: { 'application/json': { schema: { type: 'string' } } } },
+          },
+        },
+      },
+    },
+  }
+
+  it('without errorBodyType: error body cast uses no type annotation', () => {
+    const out = generateClient(minimalSpec).content
+    expect(out).toContain('await res.json().catch(() => null)')
+    expect(out).not.toContain(' as ')
+  })
+
+  it('errorBodyType laravel: LaravelValidationError type is emitted after ApiError', () => {
+    const out = generateClient(minimalSpec, { errorBodyType: 'laravel' }).content
+    expect(out).toContain('export type LaravelValidationError = {')
+    expect(out).toContain('message: string')
+    expect(out).toContain('errors: Record<string, string[]>')
+  })
+
+  it('errorBodyType laravel: error body is cast to LaravelValidationError', () => {
+    const out = generateClient(minimalSpec, { errorBodyType: 'laravel' }).content
+    expect(out).toContain('await res.json().catch(() => null) as LaravelValidationError')
+  })
+
+  it('errorBodyType laravel: no import is emitted for LaravelValidationError', () => {
+    const out = generateClient(minimalSpec, { errorBodyType: 'laravel' }).content
+    expect(out).not.toMatch(/import type \{.*LaravelValidationError/)
+  })
+
+  it('errorBodyType custom + importPath: import type is emitted at top', () => {
+    const out = generateClient(minimalSpec, {
+      errorBodyType: 'ApiErrorBody',
+      errorBodyTypeImport: './types/errors',
+    }).content
+    expect(out).toContain("import type { ApiErrorBody } from './types/errors'")
+  })
+
+  it('errorBodyType custom + importPath: error body is cast to custom type', () => {
+    const out = generateClient(minimalSpec, {
+      errorBodyType: 'ApiErrorBody',
+      errorBodyTypeImport: './types/errors',
+    }).content
+    expect(out).toContain('await res.json().catch(() => null) as ApiErrorBody')
+  })
+
+  it('errorBodyType custom without importPath: cast emitted, no import', () => {
+    const out = generateClient(minimalSpec, { errorBodyType: 'GlobalErrorType' }).content
+    expect(out).toContain('await res.json().catch(() => null) as GlobalErrorType')
+    expect(out).not.toMatch(/import type \{.*GlobalErrorType/)
+  })
+
+  it('errorBodyType custom: LaravelValidationError type NOT emitted', () => {
+    const out = generateClient(minimalSpec, { errorBodyType: 'ApiErrorBody' }).content
+    expect(out).not.toContain('LaravelValidationError')
+  })
+})
+
 describe('generateClient with empty paths', () => {
   it('handles spec with no paths gracefully', async () => {
     const spec = await parseSpec(join(__dirname, '../__fixtures__/specs/task-manager.json'))
@@ -643,6 +710,120 @@ describe('coverage: deprecated + throws together (lines 321-329, 387-394)', () =
   })
 })
 
+describe('inline additionalProperties response typing (#294)', () => {
+  it('operation response with additionalProperties schema object -> Record<string, T>', () => {
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/metrics': {
+          get: {
+            operationId: 'getMetrics',
+            responses: {
+              '200': {
+                content: {
+                  'application/json': {
+                    schema: {
+                      type: 'object',
+                      additionalProperties: { type: 'integer', format: 'int32' },
+                    },
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    expect(out).toContain('Promise<Record<string, number>>')
+    expect(out).not.toContain('Record<string, unknown>')
+  })
+
+  it('operation response with additionalProperties: true -> Record<string, unknown>', () => {
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/data': {
+          get: {
+            operationId: 'getData',
+            responses: {
+              '200': {
+                content: {
+                  'application/json': {
+                    schema: {
+                      type: 'object',
+                      additionalProperties: true,
+                    },
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    expect(out).toContain('Promise<Record<string, unknown>>')
+  })
+
+  it('operation response with object and no additionalProperties -> Record<string, unknown>', () => {
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/plain': {
+          get: {
+            operationId: 'getPlain',
+            responses: {
+              '200': {
+                content: {
+                  'application/json': {
+                    schema: {
+                      type: 'object',
+                    },
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    expect(out).toContain('Promise<Record<string, unknown>>')
+  })
+
+  it('operation response with additionalProperties string schema -> Record<string, string>', () => {
+    const spec: OpenAPIV3_1.Document = {
+      openapi: '3.1.0',
+      info: { title: 'T', version: '1' },
+      paths: {
+        '/labels': {
+          get: {
+            operationId: 'getLabels',
+            responses: {
+              '200': {
+                content: {
+                  'application/json': {
+                    schema: {
+                      type: 'object',
+                      additionalProperties: { type: 'string' },
+                    },
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    }
+    const out = generateClient(spec as OpenAPIV3_1.Document).content
+    expect(out).toContain('Promise<Record<string, string>>')
+  })
+})
+
 describe('coverage: inlineSchemaToTs edge cases (lines 28, 31-33, 37)', () => {
   it('response with nullable array type → string | null (line 28: Array.isArray(s.type) branch)', () => {
     // inlineSchemaToTs handles type: ['string', 'null'] → 'string | null'
diff --git a/packages/openapi-zod-ts/src/__tests__/config.test.ts b/packages/openapi-zod-ts/src/__tests__/config.test.ts
index bbde62d..fe015ab 100644
--- a/packages/openapi-zod-ts/src/__tests__/config.test.ts
+++ b/packages/openapi-zod-ts/src/__tests__/config.test.ts
@@ -91,6 +91,48 @@ describe('loadConfig', () => {
     await expect(loadConfig(tmpDir)).rejects.toThrow('"server_client" must be a boolean')
   })
 
+  it('loads error_body_type field', async () => {
+    writeConfig({ input_openapi: 'openapi.json', output: 'src/api', error_body_type: 'laravel' })
+    const config = await loadConfig(tmpDir)
+    expect(config.error_body_type).toBe('laravel')
+  })
+
+  it('loads error_body_type with error_body_type_import', async () => {
+    writeConfig({
+      input_openapi: 'openapi.json',
+      output: 'src/api',
+      error_body_type: 'ApiErrorBody',
+      error_body_type_import: './types/errors',
+    })
+    const config = await loadConfig(tmpDir)
+    expect(config.error_body_type).toBe('ApiErrorBody')
+    expect(config.error_body_type_import).toBe('./types/errors')
+  })
+
+  it('error_body_type and error_body_type_import are undefined when absent', async () => {
+    writeConfig({ input_openapi: 'openapi.json', output: 'src/api' })
+    const config = await loadConfig(tmpDir)
+    expect(config.error_body_type).toBeUndefined()
+    expect(config.error_body_type_import).toBeUndefined()
+  })
+
+  it('throws when error_body_type is an empty string', async () => {
+    writeConfig({ input_openapi: 'openapi.json', output: 'src/api', error_body_type: '' })
+    await expect(loadConfig(tmpDir)).rejects.toThrow('"error_body_type" must be a non-empty string')
+  })
+
+  it('throws when error_body_type_import is an empty string', async () => {
+    writeConfig({
+      input_openapi: 'openapi.json',
+      output: 'src/api',
+      error_body_type: 'MyError',
+      error_body_type_import: '',
+    })
+    await expect(loadConfig(tmpDir)).rejects.toThrow(
+      '"error_body_type_import" must be a non-empty string'
+    )
+  })
+
   it('ignores unknown config fields', async () => {
     writeConfig({ input_openapi: 'openapi.json', output: 'src/api', unknown_field: 'ignored' })
     const config = await loadConfig(tmpDir)
diff --git a/packages/openapi-zod-ts/src/__tests__/types-unit.test.ts b/packages/openapi-zod-ts/src/__tests__/types-unit.test.ts
index e7c13cb..44cf810 100644
--- a/packages/openapi-zod-ts/src/__tests__/types-unit.test.ts
+++ b/packages/openapi-zod-ts/src/__tests__/types-unit.test.ts
@@ -522,11 +522,11 @@ describe('coverage: generateTypes schema-enhanced mode with no schemas (types.ts
   })
 })
 
-describe('int64 format -> bigint in types', () => {
-  it('integer with format int64 -> bigint TS type', () => {
+describe('int64 format -> number in types', () => {
+  it('integer with format int64 -> number TS type with precision comment', () => {
     const out = genSingle('Id', { type: 'integer', format: 'int64' })
-    expect(out).toContain('bigint')
-    expect(out).not.toContain('number')
+    expect(out).toContain('number /* int64, precision limited to 2^53-1 */')
+    expect(out).not.toContain('bigint')
   })
 
   it('integer with no format -> number', () => {
@@ -535,19 +535,21 @@ describe('int64 format -> bigint in types', () => {
     expect(out).not.toContain('bigint')
   })
 
-  it('int64 as object property', () => {
+  it('int64 as object property -> number with precision comment', () => {
     const out = genSingle('Obj', {
       type: 'object',
       required: ['id'],
       properties: { id: { type: 'integer', format: 'int64' } },
     })
-    expect(out).toContain('id: bigint')
+    expect(out).toContain('id: number /* int64, precision limited to 2^53-1 */')
+    expect(out).not.toContain('bigint')
   })
 
-  it('nullable int64 array type: [integer, null] with int64 format', () => {
+  it('nullable int64 array type: [integer, null] with int64 format -> number with precision comment | null', () => {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     const out = genSingle('Id', { type: ['integer', 'null'], format: 'int64' } as any)
-    expect(out).toContain('bigint | null')
+    expect(out).toContain('number /* int64, precision limited to 2^53-1 */ | null')
+    expect(out).not.toContain('bigint')
   })
 })
 
diff --git a/packages/openapi-zod-ts/src/__tests__/zod-unit.test.ts b/packages/openapi-zod-ts/src/__tests__/zod-unit.test.ts
index 4596d04..517a226 100644
--- a/packages/openapi-zod-ts/src/__tests__/zod-unit.test.ts
+++ b/packages/openapi-zod-ts/src/__tests__/zod-unit.test.ts
@@ -606,14 +606,15 @@ describe('coverage: multi-type array with null member (zod.ts line 118 TRUE bran
   })
 })
 
-describe('int64 format -> bigint', () => {
-  it('integer with format int64 -> z.bigint()', () => {
+describe('int64 format -> z.number()', () => {
+  it('integer with format int64 -> z.number()', () => {
     const out = genSingle('Id', { type: 'integer', format: 'int64' })
     // Check the schema declaration line specifically to avoid matching header comments
-    expect(out).toContain('IdSchema = z.bigint()')
+    expect(out).toContain('IdSchema = z.number()')
+    expect(out).not.toContain('z.bigint()')
   })
 
-  it('integer with format int32 -> z.number() (only int64 gets bigint)', () => {
+  it('integer with format int32 -> z.number()', () => {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     const out = genSingle('Id', { type: 'integer', format: 'int32' } as any)
     expect(out).toContain('IdSchema = z.number()')
@@ -626,19 +627,21 @@ describe('int64 format -> bigint', () => {
     expect(out).not.toContain('z.bigint()')
   })
 
-  it('int64 as object property', () => {
+  it('int64 as object property -> z.number()', () => {
     const out = genSingle('Obj', {
       type: 'object',
       required: ['id'],
       properties: { id: { type: 'integer', format: 'int64' } },
     })
-    expect(out).toContain('id: z.bigint()')
+    expect(out).toContain('id: z.number()')
+    expect(out).not.toContain('z.bigint()')
   })
 
-  it('nullable int64 array type: [integer, null] with int64 format', () => {
+  it('nullable int64 array type: [integer, null] with int64 format -> z.number().nullable()', () => {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     const out = genSingle('Id', { type: ['integer', 'null'], format: 'int64' } as any)
-    expect(out).toContain('z.bigint().nullable()')
+    expect(out).toContain('z.number().nullable()')
+    expect(out).not.toContain('z.bigint()')
   })
 })
 
diff --git a/packages/openapi-zod-ts/src/config.ts b/packages/openapi-zod-ts/src/config.ts
index d76bed5..24e7d03 100644
--- a/packages/openapi-zod-ts/src/config.ts
+++ b/packages/openapi-zod-ts/src/config.ts
@@ -19,6 +19,20 @@ export interface Config {
   baseUrl?: string
   /** When true, generates server.ts with a createServerClient() factory for Next.js RSC (default: false) */
   server_client?: boolean
+  /**
+   * When set, schema-less error bodies in the generated client are cast to this type.
+   * Use 'laravel' to emit the built-in LaravelValidationError type alongside ApiError.
+   * Any other non-empty string is used as a type name; pair with error_body_type_import
+   * to emit an import, or omit it to treat the type as ambient/global.
+   */
+  error_body_type?: string
+  /**
+   * Module path for the custom error body type. Only used when error_body_type is set to a
+   * value other than 'laravel'. When provided, the generator emits
+   * `import type { TypeName } from 'importPath'` at the top of the generated client.
+   * Ignored when error_body_type is absent or 'laravel'.
+   */
+  error_body_type_import?: string
 }
 
 /**
@@ -47,6 +61,22 @@ export function defineProjects(configs: Config[]): { projects: Config[] } {
   return { projects: configs }
 }
 
+/** Validate the error_body_type / error_body_type_import optional fields. */
+function validateErrorBodyConfig(raw: Record<string, unknown>): void {
+  if (
+    raw['error_body_type'] !== undefined &&
+    (typeof raw['error_body_type'] !== 'string' || !raw['error_body_type'])
+  ) {
+    throw new Error('"error_body_type" must be a non-empty string when present')
+  }
+  if (
+    raw['error_body_type_import'] !== undefined &&
+    (typeof raw['error_body_type_import'] !== 'string' || !raw['error_body_type_import'])
+  ) {
+    throw new Error('"error_body_type_import" must be a non-empty string when present')
+  }
+}
+
 function parseConfig(raw: Record<string, unknown>, base: import('./config-core.js').BaseConfig): Config {
   if (
     raw['input_schema'] !== undefined &&
@@ -57,11 +87,14 @@ function parseConfig(raw: Record<string, unknown>, base: import('./config-core.j
   if (raw['server_client'] !== undefined && typeof raw['server_client'] !== 'boolean') {
     throw new Error('"server_client" must be a boolean')
   }
+  validateErrorBodyConfig(raw)
   return {
     ...base,
     input_schema: raw['input_schema'] as string | undefined,
     baseUrl: typeof raw['baseUrl'] === 'string' ? raw['baseUrl'] : undefined,
     server_client: raw['server_client'] as boolean | undefined,
+    error_body_type: raw['error_body_type'] as string | undefined,
+    error_body_type_import: raw['error_body_type_import'] as string | undefined,
   }
 }
 
diff --git a/packages/openapi-zod-ts/src/generator.ts b/packages/openapi-zod-ts/src/generator.ts
index ecda10b..f104b66 100644
--- a/packages/openapi-zod-ts/src/generator.ts
+++ b/packages/openapi-zod-ts/src/generator.ts
@@ -80,7 +80,16 @@ async function generateOne(
       cookieAuth ? { defaultCredentials: 'include', authSchemes } : { authSchemes }
     )
   )
-  generatedFiles.push(generateClient(spec, undefined, writableVariantMap))
+  generatedFiles.push(
+    generateClient(
+      spec,
+      {
+        errorBodyType: config.error_body_type,
+        errorBodyTypeImport: config.error_body_type_import,
+      },
+      writableVariantMap
+    )
+  )
   generatedFiles.push(generateIndexBarrel())
 
   console.log(`${prefix}Writing output to: ${outputDir}`)
@@ -162,7 +171,12 @@ async function generateZodIntegration(
     )
     const enhancedClient = generateClient(
       spec,
-      { schemaNames: exportedSchemas, schemaImportPath },
+      {
+        schemaNames: exportedSchemas,
+        schemaImportPath,
+        errorBodyType: config.error_body_type,
+        errorBodyTypeImport: config.error_body_type_import,
+      },
       writableVariantMap
     )
     const enhancedTypesPath = join(outputDir, enhancedTypes.filename)
diff --git a/packages/openapi-zod-ts/src/plugins/client.ts b/packages/openapi-zod-ts/src/plugins/client.ts
index 3c2ac79..ae676d7 100644
--- a/packages/openapi-zod-ts/src/plugins/client.ts
+++ b/packages/openapi-zod-ts/src/plugins/client.ts
@@ -51,6 +51,31 @@ function resolveDeepRefToTs(
   return result
 }
 
+/**
+ * Resolve the TypeScript Record type for an inline object schema.
+ * When additionalProperties is a schema object, recurse to produce Record<string, T>.
+ * Otherwise fall back to Record<string, unknown>.
+ */
+function inlineObjectSchemaToTs(
+  s: SchemaObject,
+  spec?: OpenAPIV3_1.Document,
+  visited?: Set<string>
+): string {
+  if (
+    s.additionalProperties !== undefined &&
+    s.additionalProperties !== true &&
+    s.additionalProperties !== false
+  ) {
+    const valueType = inlineSchemaToTs(
+      s.additionalProperties as SchemaObject | ReferenceObject,
+      spec,
+      visited
+    )
+    return `Record<string, ${valueType}>`
+  }
+  return 'Record<string, unknown>'
+}
+
 function inlineSchemaToTs(
   schema: SchemaObject | ReferenceObject,
   spec?: OpenAPIV3_1.Document,
@@ -73,7 +98,7 @@ function inlineSchemaToTs(
     if (items !== undefined) return `${inlineSchemaToTs(items, spec, visited)}[]`
     return 'unknown[]'
   }
-  if (s.type === 'object') return 'Record<string, unknown>'
+  if (s.type === 'object') return inlineObjectSchemaToTs(s, spec, visited)
   if (s.type !== undefined) return primitiveToTs(s.type as string)
   return 'unknown'
 }
@@ -823,6 +848,12 @@ interface HelperFeatures {
   hasMultipart: boolean
   /** Any endpoint uses application/x-www-form-urlencoded. Emits bodyEncoding branch in `_request`. */
   hasFormUrlencoded: boolean
+  /**
+   * When set, schema-less error bodies are cast to this type name in the generated error handler.
+   * Use 'laravel' for the built-in LaravelValidationError type or any other string for an
+   * ambient/imported type (see ClientOptions.errorBodyTypeImport for the import path).
+   */
+  errorBodyType?: string
 }
 
 /**
@@ -990,10 +1021,22 @@ function emitAuthHeaderSpreads(
   }
 }
 
-/** Emits the shared error-check + return block at the end of a helper function. */
-function emitErrorCheckAndReturn(lines: string[]): void {
+/**
+ * Emits the shared error-check + return block at the end of a helper function.
+ * When errorBodyType is provided, the error body is cast to that type so callers
+ * get a typed body instead of unknown. The special value 'laravel' uses the built-in
+ * LaravelValidationError type emitted alongside ApiError; any other value is used as-is
+ * (caller is responsible for ensuring the type is in scope).
+ */
+function emitErrorCheckAndReturn(lines: string[], errorBodyType?: string): void {
   lines.push(`  if (!res.ok) {`)
-  lines.push(`    const err = new ApiError(res.status, await res.json().catch(() => null))`)
+  if (errorBodyType !== undefined) {
+    lines.push(
+      `    const err = new ApiError(res.status, await res.json().catch(() => null) as ${errorBodyType})`
+    )
+  } else {
+    lines.push(`    const err = new ApiError(res.status, await res.json().catch(() => null))`)
+  }
   lines.push(`    onError?.(err)`)
   lines.push(`    throw err`)
   lines.push(`  }`)
@@ -1116,7 +1159,7 @@ function emitRequestFunction(
   lines.push(`  }`)
   emitOnRequestBlock(lines)
   emitSignalAndFetch(lines)
-  emitErrorCheckAndReturn(lines)
+  emitErrorCheckAndReturn(lines, features.errorBodyType)
 }
 
 /** Emits the _requestForm function into lines (up to and including the closing brace). */
@@ -1157,7 +1200,7 @@ function emitRequestFormFunction(
   lines.push(`  }`)
   emitOnRequestBlock(lines)
   emitSignalAndFetch(lines)
-  emitErrorCheckAndReturn(lines)
+  emitErrorCheckAndReturn(lines, features.errorBodyType)
 }
 
 /**
@@ -1437,6 +1480,20 @@ function generateFunctionCode(
 export interface ClientOptions {
   schemaNames?: Set<string>
   schemaImportPath?: string
+  /**
+   * When set, schema-less error bodies are cast to this type in the generated client.
+   * Use 'laravel' to emit the built-in LaravelValidationError type
+   * ({ message: string; errors: Record<string, string[]> }) alongside ApiError.
+   * Any other string is used as-is; pair it with errorBodyTypeImport to emit an import,
+   * or leave errorBodyTypeImport unset to treat it as an ambient/global type.
+   */
+  errorBodyType?: string
+  /**
+   * When errorBodyType is set to a custom type name (not 'laravel'), provide the module
+   * path here and the generator will emit `import type { TypeName } from 'importPath'`
+   * at the top of the generated client. Ignored when errorBodyType is 'laravel' or absent.
+   */
+  errorBodyTypeImport?: string
 }
 
 /** Built-in TypeScript types that must NOT be imported from ./models */
@@ -1637,6 +1694,18 @@ export function generateClient(
     lines.push(`import { ${sortedSchemas.join(', ')} } from '${options.schemaImportPath}'`)
   }
 
+  // When a custom error body type with an import path is configured, emit the import.
+  // The 'laravel' value uses a built-in type emitted inline and needs no import.
+  if (
+    options?.errorBodyType !== undefined &&
+    options.errorBodyType !== 'laravel' &&
+    options.errorBodyTypeImport !== undefined
+  ) {
+    lines.push(
+      `import type { ${options.errorBodyType} } from '${options.errorBodyTypeImport}'`
+    )
+  }
+
   lines.push('')
 
   // ApiError class — generic so callers can type-narrow caught errors.
@@ -1653,16 +1722,31 @@ export function generateClient(
   lines.push(`  }`)
   lines.push(`}`)
 
+  // When error_body_type is 'laravel', emit the built-in LaravelValidationError type
+  // immediately after ApiError so it is available for the typed error body cast.
+  if (options?.errorBodyType === 'laravel') {
+    lines.push(``)
+    lines.push(`export type LaravelValidationError = {`)
+    lines.push(`  message: string`)
+    lines.push(`  errors: Record<string, string[]>`)
+    lines.push(`}`)
+  }
+
   // Shared private request helpers — emitted once, called by every endpoint function.
   // Code inside the helpers is feature-conditional: only emit auth/credentials/extraHeaders
   // when the spec actually declares those features.
   if (hasAnyEndpoints) {
+    // Resolve the actual TS type name for the error body cast.
+    // 'laravel' is a config shorthand for the built-in LaravelValidationError type.
+    const resolvedErrorBodyType =
+      options?.errorBodyType === 'laravel' ? 'LaravelValidationError' : options?.errorBodyType
     const helperFeatures: HelperFeatures = {
       authSchemes: detectAuthSchemes(spec),
       hasCookieAuth: hasCookieAuth(spec),
       hasHeaderParams: hasHeaderParamEndpoints,
       hasMultipart: hasMultipartEndpoints,
       hasFormUrlencoded: hasFormUrlencodedEndpoints,
+      errorBodyType: resolvedErrorBodyType,
     }
     lines.push('')
     lines.push(generateRequestHelpers(helperFeatures))
diff --git a/packages/openapi-zod-ts/src/plugins/types.ts b/packages/openapi-zod-ts/src/plugins/types.ts
index 99e7ce8..a4fdbdf 100644
--- a/packages/openapi-zod-ts/src/plugins/types.ts
+++ b/packages/openapi-zod-ts/src/plugins/types.ts
@@ -201,8 +201,10 @@ function schemaToTypeString(
 
 /**
  * Map an OpenAPI primitive type to a TypeScript type.
- * For integer with format int64, returns bigint instead of number
- * to preserve precision for 64-bit IDs.
+ * For integer with format int64, returns number with an inline comment noting precision
+ * is limited to 2^53-1 (JS Number.MAX_SAFE_INTEGER). BigInt is avoided because
+ * JSON.stringify throws on bigint values and JSON.parse never produces bigint, making
+ * bigint unworkable for standard API client serialization.
  */
 function primitiveToTs(type: string, format?: string): string {
   switch (type) {
@@ -211,8 +213,7 @@ function primitiveToTs(type: string, format?: string): string {
     case 'number':
       return 'number'
     case 'integer':
-      // int64 requires bigint for precision-safe 64-bit IDs (JS number cannot represent >2^53)
-      return format === 'int64' ? 'bigint' : 'number'
+      return format === 'int64' ? 'number /* int64, precision limited to 2^53-1 */' : 'number'
     case 'boolean':
       return 'boolean'
     case 'null':
diff --git a/packages/openapi-zod-ts/src/plugins/zod.ts b/packages/openapi-zod-ts/src/plugins/zod.ts
index a454969..2fcc13f 100644
--- a/packages/openapi-zod-ts/src/plugins/zod.ts
+++ b/packages/openapi-zod-ts/src/plugins/zod.ts
@@ -81,8 +81,9 @@ function serializeLiteral(value: unknown): string {
 
 /**
  * Return the Zod v4 base expression for a primitive type.
- * For integer with format int64, returns z.bigint() instead of z.number()
- * to preserve precision for 64-bit IDs.
+ * For integer with format int64, returns z.number() instead of z.bigint() because
+ * JSON.stringify throws on bigint values and JSON.parse never produces bigint. Precision
+ * is limited to 2^53-1 (JS Number.MAX_SAFE_INTEGER) for int64 fields.
  */
 function primitiveToZod(type: string, format?: string): string {
   switch (type) {
@@ -91,8 +92,7 @@ function primitiveToZod(type: string, format?: string): string {
     case 'number':
       return 'z.number()'
     case 'integer':
-      // int64 requires bigint for precision-safe 64-bit IDs (JS number cannot represent >2^53)
-      return format === 'int64' ? 'z.bigint()' : 'z.number()'
+      return format === 'int64' ? 'z.number()' : 'z.number()'
     case 'boolean':
       return 'z.boolean()'
     case 'null':
@@ -325,8 +325,8 @@ function objectSchemaToZod(schema: SchemaObject): string {
 
 /**
  * Handle scalar primitive types: string, integer, number, boolean, null.
- * Applies format-based specialisation (stringSchemaExpr, int64 bigint) and
- * numeric/string constraints before returning the Zod expression.
+ * Applies format-based specialisation (stringSchemaExpr, numeric constraints) and
+ * string/numeric constraints before returning the Zod expression.
  */
 function primitiveTypeToZod(schema: SchemaObject): string {
   const type = schema.type as string
@@ -335,9 +335,7 @@ function primitiveTypeToZod(schema: SchemaObject): string {
     base = stringSchemaExpr(schema)
   } else if (type === 'integer') {
     base = primitiveToZod('integer', schema.format as string | undefined)
-    if (base !== 'z.bigint()') {
-      base = applyNumberConstraints(base, schema)
-    }
+    base = applyNumberConstraints(base, schema)
   } else if (type === 'number') {
     base = primitiveToZod('number')
     base = applyNumberConstraints(base, schema)