diff --git a/app/api/bookkeeping/account-balances/route.ts b/app/api/bookkeeping/account-balances/route.ts
index ae06165e..c7281574 100644
--- a/app/api/bookkeeping/account-balances/route.ts
+++ b/app/api/bookkeeping/account-balances/route.ts
@@ -120,7 +120,8 @@ export async function GET(request: Request) {
         query = query.neq('journal_entry_id', obEntryId)
       }
 
-      return query.range(from, to)
+      // Stable total order for correct paging (see fetch-all.ts).
+      return query.order('id', { ascending: true }).range(from, to)
     })
   } catch (err) {
     log.error('period activity lookup failed', {
diff --git a/app/api/v1/companies/[companyId]/compliance/check/route.ts b/app/api/v1/companies/[companyId]/compliance/check/route.ts
index 4cb26eaa..41c1dfd1 100644
--- a/app/api/v1/companies/[companyId]/compliance/check/route.ts
+++ b/app/api/v1/companies/[companyId]/compliance/check/route.ts
@@ -20,7 +20,7 @@
 import { z } from 'zod'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ownsFiscalPeriod } from '@/lib/api/v1/owns-fiscal-period'
@@ -234,7 +234,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: ComplianceCheckResponse },
+  response: { success: dataEnvelope(ComplianceCheckResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/customers/[id]/route.ts b/app/api/v1/companies/[companyId]/customers/[id]/route.ts
index 6baf8a0c..2699ac20 100644
--- a/app/api/v1/companies/[companyId]/customers/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/customers/[id]/route.ts
@@ -16,7 +16,7 @@ import { z } from 'zod'
 import { noContent, ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
 import { parseExpand } from '@/lib/api/v1/expand'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope, NoBodyResponse } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { UpdateCustomerSchema } from '@/lib/api/schemas'
@@ -100,7 +100,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: CustomerDetail },
+  response: { success: dataEnvelope(CustomerDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -244,7 +244,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: UpdateCustomerSchema },
-  response: { success: CustomerDetail },
+  response: { success: dataEnvelope(CustomerDetail) },
 })
 
 const CUSTOMER_UPDATE_RESPONSE_COLUMNS = CUSTOMER_DETAIL_COLUMNS
@@ -438,7 +438,7 @@ registerEndpoint({
   idempotent: true,
   reversible: true,
   dryRunSupported: true,
-  response: { success: z.object({}) },
+  response: { success: NoBodyResponse },
 })
 
 export const DELETE = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/customers/bulk-create/route.ts b/app/api/v1/companies/[companyId]/customers/bulk-create/route.ts
index ce8231e2..832704cf 100644
--- a/app/api/v1/companies/[companyId]/customers/bulk-create/route.ts
+++ b/app/api/v1/companies/[companyId]/customers/bulk-create/route.ts
@@ -17,7 +17,7 @@ import { z } from 'zod'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateCustomerSchema } from '@/lib/api/schemas'
@@ -99,7 +99,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: BulkCreateRequest },
-  response: { success: BulkCreateResponse },
+  response: { success: dataEnvelope(BulkCreateResponse) },
 })
 
 interface ResultItem {
diff --git a/app/api/v1/companies/[companyId]/customers/route.ts b/app/api/v1/companies/[companyId]/customers/route.ts
index 4cf47a4c..ab6bdcb0 100644
--- a/app/api/v1/companies/[companyId]/customers/route.ts
+++ b/app/api/v1/companies/[companyId]/customers/route.ts
@@ -16,7 +16,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateCustomerSchema } from '@/lib/api/schemas'
@@ -301,7 +301,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateCustomerSchema },
-  response: { success: CustomerCreated },
+  response: { success: dataEnvelope(CustomerCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/documents/[id]/download/route.ts b/app/api/v1/companies/[companyId]/documents/[id]/download/route.ts
index a6e62017..8202ecf5 100644
--- a/app/api/v1/companies/[companyId]/documents/[id]/download/route.ts
+++ b/app/api/v1/companies/[companyId]/documents/[id]/download/route.ts
@@ -13,7 +13,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { eventBus } from '@/lib/events'
@@ -77,7 +77,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: DocumentDownloadResponse },
+  response: { success: dataEnvelope(DocumentDownloadResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/documents/[id]/link/route.ts b/app/api/v1/companies/[companyId]/documents/[id]/link/route.ts
index e386d738..5ca71406 100644
--- a/app/api/v1/companies/[companyId]/documents/[id]/link/route.ts
+++ b/app/api/v1/companies/[companyId]/documents/[id]/link/route.ts
@@ -18,7 +18,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { linkToJournalEntry } from '@/lib/core/documents/document-service'
@@ -71,7 +71,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: Body },
-  response: { success: DocumentLinkedResponse },
+  response: { success: dataEnvelope(DocumentLinkedResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/documents/route.ts b/app/api/v1/companies/[companyId]/documents/route.ts
index 564a164a..4b3f2236 100644
--- a/app/api/v1/companies/[companyId]/documents/route.ts
+++ b/app/api/v1/companies/[companyId]/documents/route.ts
@@ -31,7 +31,7 @@
 
 import { z } from 'zod'
 import { created } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import {
@@ -110,7 +110,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   request: { body: MultipartBodySchema, contentType: 'multipart/form-data' },
-  response: { success: DocumentUploaded },
+  response: { success: dataEnvelope(DocumentUploaded) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/employees/[id]/route.ts b/app/api/v1/companies/[companyId]/employees/[id]/route.ts
index 9d76eab3..a3b91581 100644
--- a/app/api/v1/companies/[companyId]/employees/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/employees/[id]/route.ts
@@ -20,7 +20,7 @@
 import { z } from 'zod'
 import { ok, noContent } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope, NoBodyResponse } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { UpdateEmployeeSchema } from '@/lib/api/schemas'
@@ -136,7 +136,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: EmployeeDetail },
+  response: { success: dataEnvelope(EmployeeDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -201,7 +201,7 @@ registerEndpoint({
   request: { body: UpdateEmployeeSchema },
   // Write responses mask personnummer (GDPR Art.5(1)(c)) — only the GET
   // drill-in returns the full value. Symmetric with the POST response.
-  response: { success: EmployeeWriteResponse },
+  response: { success: dataEnvelope(EmployeeWriteResponse) },
 })
 
 export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -402,7 +402,7 @@ registerEndpoint({
   idempotent: true,
   reversible: true,
   dryRunSupported: true,
-  response: { success: z.object({}) },
+  response: { success: NoBodyResponse },
 })
 
 export const DELETE = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/employees/route.ts b/app/api/v1/companies/[companyId]/employees/route.ts
index 5c132cdb..a1629d5d 100644
--- a/app/api/v1/companies/[companyId]/employees/route.ts
+++ b/app/api/v1/companies/[companyId]/employees/route.ts
@@ -24,7 +24,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateEmployeeSchema } from '@/lib/api/schemas'
@@ -318,7 +318,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateEmployeeSchema },
-  response: { success: EmployeeCreated },
+  response: { success: dataEnvelope(EmployeeCreated) },
 })
 
 const EMPLOYEE_RESPONSE_COLUMNS =
diff --git a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/close/route.ts b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/close/route.ts
index 131c66ba..bf26f668 100644
--- a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/close/route.ts
+++ b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/close/route.ts
@@ -11,7 +11,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { closePeriod } from '@/lib/core/bookkeeping/period-service'
@@ -49,7 +49,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: PeriodClosedResponse },
+  response: { success: dataEnvelope(PeriodClosedResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/currency-revaluation/route.ts b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/currency-revaluation/route.ts
index 72fd642b..d80e0b0b 100644
--- a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/currency-revaluation/route.ts
+++ b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/currency-revaluation/route.ts
@@ -12,7 +12,7 @@
 
 import { z } from 'zod'
 import { accepted } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ownsFiscalPeriod } from '@/lib/api/v1/owns-fiscal-period'
@@ -59,7 +59,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: false,
   request: { body: Body },
-  response: { success: RevaluationAccepted },
+  response: { success: dataEnvelope(RevaluationAccepted) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/lock/route.ts b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/lock/route.ts
index 9086a203..619589e6 100644
--- a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/lock/route.ts
+++ b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/lock/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { lockPeriod } from '@/lib/core/bookkeeping/period-service'
@@ -46,7 +46,7 @@ registerEndpoint({
   idempotent: true,
   reversible: true,
   dryRunSupported: false,
-  response: { success: PeriodLockedResponse },
+  response: { success: dataEnvelope(PeriodLockedResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/opening-balances/route.ts b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/opening-balances/route.ts
index 74711f9b..b5563ac5 100644
--- a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/opening-balances/route.ts
+++ b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/opening-balances/route.ts
@@ -12,7 +12,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ownsFiscalPeriod } from '@/lib/api/v1/owns-fiscal-period'
@@ -56,7 +56,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: false,
   request: { body: Body },
-  response: { success: OpeningBalancesResponse },
+  response: { success: dataEnvelope(OpeningBalancesResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/year-end/route.ts b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/year-end/route.ts
index 5cecf192..4f181641 100644
--- a/app/api/v1/companies/[companyId]/fiscal-periods/[id]/year-end/route.ts
+++ b/app/api/v1/companies/[companyId]/fiscal-periods/[id]/year-end/route.ts
@@ -15,7 +15,7 @@
 
 import { z } from 'zod'
 import { accepted } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ownsFiscalPeriod } from '@/lib/api/v1/owns-fiscal-period'
@@ -62,7 +62,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: YearEndAcceptedResponse },
+  response: { success: dataEnvelope(YearEndAcceptedResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/imports/bank/route.ts b/app/api/v1/companies/[companyId]/imports/bank/route.ts
index 55a88576..a8d03d40 100644
--- a/app/api/v1/companies/[companyId]/imports/bank/route.ts
+++ b/app/api/v1/companies/[companyId]/imports/bank/route.ts
@@ -21,7 +21,7 @@
 
 import { z } from 'zod'
 import { accepted } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import {
@@ -83,7 +83,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   request: { contentType: 'multipart/form-data' },
-  response: { success: BankImportAccepted },
+  response: { success: dataEnvelope(BankImportAccepted) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/imports/sie/route.ts b/app/api/v1/companies/[companyId]/imports/sie/route.ts
index 36f471f1..6ad6e63a 100644
--- a/app/api/v1/companies/[companyId]/imports/sie/route.ts
+++ b/app/api/v1/companies/[companyId]/imports/sie/route.ts
@@ -24,7 +24,7 @@
 
 import { z } from 'zod'
 import { accepted } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import {
@@ -94,7 +94,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   request: { contentType: 'multipart/form-data' },
-  response: { success: SieImportAccepted },
+  response: { success: dataEnvelope(SieImportAccepted) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/invoices/[id]/credit/route.ts b/app/api/v1/companies/[companyId]/invoices/[id]/credit/route.ts
index 24507be7..4ab30094 100644
--- a/app/api/v1/companies/[companyId]/invoices/[id]/credit/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/[id]/credit/route.ts
@@ -27,7 +27,7 @@
 import { z } from 'zod'
 import { created } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { createCreditNoteJournalEntry } from '@/lib/bookkeeping/invoice-entries'
@@ -96,7 +96,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: CreditNoteRequest },
-  response: { success: CreditNoteCreated },
+  response: { success: dataEnvelope(CreditNoteCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/invoices/[id]/mark-paid/route.ts b/app/api/v1/companies/[companyId]/invoices/[id]/mark-paid/route.ts
index 1adad292..b9019c32 100644
--- a/app/api/v1/companies/[companyId]/invoices/[id]/mark-paid/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/[id]/mark-paid/route.ts
@@ -29,7 +29,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { MarkInvoicePaidSchema } from '@/lib/api/schemas'
@@ -99,7 +99,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: MarkInvoicePaidSchema },
-  response: { success: InvoiceMarkPaidResponse },
+  response: { success: dataEnvelope(InvoiceMarkPaidResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/invoices/[id]/mark-sent/route.ts b/app/api/v1/companies/[companyId]/invoices/[id]/mark-sent/route.ts
index e14da941..5194c3b4 100644
--- a/app/api/v1/companies/[companyId]/invoices/[id]/mark-sent/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/[id]/mark-sent/route.ts
@@ -36,7 +36,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { createInvoiceJournalEntry } from '@/lib/bookkeeping/invoice-entries'
@@ -97,7 +97,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: InvoiceMarkSentResponse },
+  response: { success: dataEnvelope(InvoiceMarkSentResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/invoices/[id]/route.ts b/app/api/v1/companies/[companyId]/invoices/[id]/route.ts
index b2ea882b..4a9d47b0 100644
--- a/app/api/v1/companies/[companyId]/invoices/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/[id]/route.ts
@@ -16,7 +16,7 @@ import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
 import { parseExpand } from '@/lib/api/v1/expand'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -108,7 +108,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: InvoiceDetail },
+  response: { success: dataEnvelope(InvoiceDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -210,7 +210,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: V1PatchDraftInvoiceSchema },
-  response: { success: InvoiceDetail },
+  response: { success: dataEnvelope(InvoiceDetail) },
 })
 
 const INVOICE_PATCH_RESPONSE_COLUMNS =
diff --git a/app/api/v1/companies/[companyId]/invoices/[id]/send/route.ts b/app/api/v1/companies/[companyId]/invoices/[id]/send/route.ts
index fb7ba17a..316fb074 100644
--- a/app/api/v1/companies/[companyId]/invoices/[id]/send/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/[id]/send/route.ts
@@ -39,7 +39,7 @@ import { z } from 'zod'
 import { renderToBuffer } from '@react-pdf/renderer'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { InvoicePDF } from '@/lib/invoices/pdf-template'
@@ -113,7 +113,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: InvoiceSendResponse },
+  response: { success: dataEnvelope(InvoiceSendResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/invoices/bulk-create/route.ts b/app/api/v1/companies/[companyId]/invoices/bulk-create/route.ts
index 4a9d22c5..7877fa96 100644
--- a/app/api/v1/companies/[companyId]/invoices/bulk-create/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/bulk-create/route.ts
@@ -36,7 +36,7 @@ import { z } from 'zod'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateInvoiceSchema } from '@/lib/api/schemas'
@@ -128,7 +128,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: BulkCreateRequest },
-  response: { success: BulkCreateResponse },
+  response: { success: dataEnvelope(BulkCreateResponse) },
 })
 
 interface ResultItem {
diff --git a/app/api/v1/companies/[companyId]/invoices/route.ts b/app/api/v1/companies/[companyId]/invoices/route.ts
index 9735192b..02bad7cf 100644
--- a/app/api/v1/companies/[companyId]/invoices/route.ts
+++ b/app/api/v1/companies/[companyId]/invoices/route.ts
@@ -23,7 +23,7 @@ import {
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
 import { parseExpand } from '@/lib/api/v1/expand'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateInvoiceSchema } from '@/lib/api/schemas'
@@ -372,7 +372,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateInvoiceSchema },
-  response: { success: InvoiceCreated },
+  response: { success: dataEnvelope(InvoiceCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/journal-entries/[id]/commit/route.ts b/app/api/v1/companies/[companyId]/journal-entries/[id]/commit/route.ts
index bfbe46f0..06b0bfb9 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/[id]/commit/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/[id]/commit/route.ts
@@ -15,7 +15,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { commitEntry, getNextVoucherNumber } from '@/lib/bookkeeping/engine'
@@ -59,7 +59,7 @@ registerEndpoint({
   idempotent: true,
   reversible: true,
   dryRunSupported: true,
-  response: { success: JournalEntryCommitted },
+  response: { success: dataEnvelope(JournalEntryCommitted) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/journal-entries/[id]/correct/route.ts b/app/api/v1/companies/[companyId]/journal-entries/[id]/correct/route.ts
index 85837014..0ef61553 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/[id]/correct/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/[id]/correct/route.ts
@@ -16,7 +16,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -76,7 +76,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: CorrectJournalEntrySchema },
-  response: { success: JournalEntryCorrected },
+  response: { success: dataEnvelope(JournalEntryCorrected) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/journal-entries/[id]/reverse/route.ts b/app/api/v1/companies/[companyId]/journal-entries/[id]/reverse/route.ts
index 9c24e2d2..47ca1772 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/[id]/reverse/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/[id]/reverse/route.ts
@@ -14,7 +14,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -68,7 +68,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: ReverseRequest },
-  response: { success: JournalEntryReversed },
+  response: { success: dataEnvelope(JournalEntryReversed) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/journal-entries/[id]/route.ts b/app/api/v1/companies/[companyId]/journal-entries/[id]/route.ts
index 46e7d9fd..afc3ca18 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/[id]/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -86,7 +86,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: JournalEntryDetail },
+  response: { success: dataEnvelope(JournalEntryDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/journal-entries/batch-create/route.ts b/app/api/v1/companies/[companyId]/journal-entries/batch-create/route.ts
index 89460edd..28e70802 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/batch-create/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/batch-create/route.ts
@@ -17,7 +17,7 @@ import { z } from 'zod'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ownsFiscalPeriod } from '@/lib/api/v1/owns-fiscal-period'
@@ -89,7 +89,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: BulkRequest },
-  response: { success: BulkResponse },
+  response: { success: dataEnvelope(BulkResponse) },
 })
 
 interface ResultItem {
diff --git a/app/api/v1/companies/[companyId]/journal-entries/route.ts b/app/api/v1/companies/[companyId]/journal-entries/route.ts
index 8c6c0987..f04e67f3 100644
--- a/app/api/v1/companies/[companyId]/journal-entries/route.ts
+++ b/app/api/v1/companies/[companyId]/journal-entries/route.ts
@@ -21,7 +21,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -246,7 +246,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateJournalEntrySchema },
-  response: { success: JournalEntryDetail },
+  response: { success: dataEnvelope(JournalEntryDetail) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reconciliation/bank/run/route.ts b/app/api/v1/companies/[companyId]/reconciliation/bank/run/route.ts
index ee41b3e1..43aa5d86 100644
--- a/app/api/v1/companies/[companyId]/reconciliation/bank/run/route.ts
+++ b/app/api/v1/companies/[companyId]/reconciliation/bank/run/route.ts
@@ -12,7 +12,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { runReconciliation } from '@/lib/reconciliation/bank-reconciliation'
@@ -88,7 +88,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: RunRequest },
-  response: { success: RunResponse },
+  response: { success: dataEnvelope(RunResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reconciliation/bank/status/route.ts b/app/api/v1/companies/[companyId]/reconciliation/bank/status/route.ts
index 0a1a9aaf..dcee40e4 100644
--- a/app/api/v1/companies/[companyId]/reconciliation/bank/status/route.ts
+++ b/app/api/v1/companies/[companyId]/reconciliation/bank/status/route.ts
@@ -7,7 +7,7 @@
  */
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { getReconciliationStatus } from '@/lib/reconciliation/bank-reconciliation'
@@ -56,7 +56,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: StatusResponse },
+  response: { success: dataEnvelope(StatusResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/ar-ledger/route.ts b/app/api/v1/companies/[companyId]/reports/ar-ledger/route.ts
index c8983698..54cdf08c 100644
--- a/app/api/v1/companies/[companyId]/reports/ar-ledger/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/ar-ledger/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -39,7 +39,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/avgifter-basis/route.ts b/app/api/v1/companies/[companyId]/reports/avgifter-basis/route.ts
index ba8fcf49..1812e6f7 100644
--- a/app/api/v1/companies/[companyId]/reports/avgifter-basis/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/avgifter-basis/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -39,7 +39,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/balance-sheet/route.ts b/app/api/v1/companies/[companyId]/reports/balance-sheet/route.ts
index aaa4e833..14cc1aa7 100644
--- a/app/api/v1/companies/[companyId]/reports/balance-sheet/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/balance-sheet/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { generateBalanceSheet } from '@/lib/reports/balance-sheet'
@@ -49,7 +49,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: BalanceSheetResponse },
+  response: { success: dataEnvelope(BalanceSheetResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/continuity-check/route.ts b/app/api/v1/companies/[companyId]/reports/continuity-check/route.ts
index ee2c21e1..650b97cc 100644
--- a/app/api/v1/companies/[companyId]/reports/continuity-check/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/continuity-check/route.ts
@@ -11,7 +11,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { validateBalanceContinuity } from '@/lib/reports/continuity-check'
@@ -42,7 +42,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/general-ledger/route.ts b/app/api/v1/companies/[companyId]/reports/general-ledger/route.ts
index 6bf4e271..13d38e49 100644
--- a/app/api/v1/companies/[companyId]/reports/general-ledger/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/general-ledger/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
@@ -43,7 +43,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: GeneralLedgerResponse },
+  response: { success: dataEnvelope(GeneralLedgerResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/income-statement/route.ts b/app/api/v1/companies/[companyId]/reports/income-statement/route.ts
index 412c7312..0c577136 100644
--- a/app/api/v1/companies/[companyId]/reports/income-statement/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/income-statement/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { generateIncomeStatement } from '@/lib/reports/income-statement'
@@ -41,7 +41,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: IncomeStatementResponse },
+  response: { success: dataEnvelope(IncomeStatementResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/journal-register/route.ts b/app/api/v1/companies/[companyId]/reports/journal-register/route.ts
index 73e2dc37..c1433e52 100644
--- a/app/api/v1/companies/[companyId]/reports/journal-register/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/journal-register/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { generateJournalRegister } from '@/lib/reports/journal-register'
@@ -39,7 +39,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/monthly-breakdown/route.ts b/app/api/v1/companies/[companyId]/reports/monthly-breakdown/route.ts
index 7041669b..12455c85 100644
--- a/app/api/v1/companies/[companyId]/reports/monthly-breakdown/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/monthly-breakdown/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { generateMonthlyBreakdown } from '@/lib/reports/monthly-breakdown'
@@ -36,7 +36,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/salary-journal/route.ts b/app/api/v1/companies/[companyId]/reports/salary-journal/route.ts
index d7145857..ed6c1c82 100644
--- a/app/api/v1/companies/[companyId]/reports/salary-journal/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/salary-journal/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -41,7 +41,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/supplier-ledger/route.ts b/app/api/v1/companies/[companyId]/reports/supplier-ledger/route.ts
index 308a1045..2755a8c9 100644
--- a/app/api/v1/companies/[companyId]/reports/supplier-ledger/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/supplier-ledger/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -39,7 +39,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/trial-balance/route.ts b/app/api/v1/companies/[companyId]/reports/trial-balance/route.ts
index 80cdb281..7530c73c 100644
--- a/app/api/v1/companies/[companyId]/reports/trial-balance/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/trial-balance/route.ts
@@ -9,7 +9,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { loadPeriodFromQuery, safeGenerate } from '@/lib/api/v1/report-period'
 import { generateTrialBalance } from '@/lib/reports/trial-balance'
@@ -64,7 +64,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: TrialBalanceResponse },
+  response: { success: dataEnvelope(TrialBalanceResponse) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/vacation-liability/route.ts b/app/api/v1/companies/[companyId]/reports/vacation-liability/route.ts
index 0ef05329..414eeaab 100644
--- a/app/api/v1/companies/[companyId]/reports/vacation-liability/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/vacation-liability/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -39,7 +39,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/reports/vat-declaration/route.ts b/app/api/v1/companies/[companyId]/reports/vat-declaration/route.ts
index 4abbff23..89588a02 100644
--- a/app/api/v1/companies/[companyId]/reports/vat-declaration/route.ts
+++ b/app/api/v1/companies/[companyId]/reports/vat-declaration/route.ts
@@ -8,7 +8,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { safeGenerate } from '@/lib/api/v1/report-period'
@@ -72,7 +72,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.unknown() },
+  response: { success: dataEnvelope(z.unknown()) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/approve/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/approve/route.ts
index 11c7ed0c..ea7c3173 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/approve/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/approve/route.ts
@@ -18,7 +18,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { eventBus } from '@/lib/events'
@@ -68,7 +68,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SalaryRunApproved },
+  response: { success: dataEnvelope(SalaryRunApproved) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/book/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/book/route.ts
index e3530870..fc17e2d7 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/book/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/book/route.ts
@@ -29,7 +29,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -99,7 +99,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SalaryRunBooked },
+  response: { success: dataEnvelope(SalaryRunBooked) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/calculate/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/calculate/route.ts
index ad1deac1..fce1107a 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/calculate/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/calculate/route.ts
@@ -25,7 +25,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { runSalaryCalculation } from '@/lib/salary/run-calculation'
@@ -85,7 +85,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SalaryRunCalculated },
+  response: { success: dataEnvelope(SalaryRunCalculated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/generate-agi/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/generate-agi/route.ts
index 3cc27ddb..26dc815b 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/generate-agi/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/generate-agi/route.ts
@@ -29,7 +29,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { generateAgiDeclaration } from '@/lib/salary/agi/generate-declaration'
@@ -99,7 +99,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: AgiGenerated },
+  response: { success: dataEnvelope(AgiGenerated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/mark-paid/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/mark-paid/route.ts
index 04a31b7d..b4ffc90c 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/mark-paid/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/mark-paid/route.ts
@@ -13,7 +13,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -51,7 +51,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SalaryRunPaid },
+  response: { success: dataEnvelope(SalaryRunPaid) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/[id]/route.ts b/app/api/v1/companies/[companyId]/salary-runs/[id]/route.ts
index 00c3de97..ed3afbdd 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/[id]/route.ts
@@ -14,7 +14,7 @@
 import { z } from 'zod'
 import { ok, noContent } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope, NoBodyResponse } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -92,7 +92,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: SalaryRunDetail },
+  response: { success: dataEnvelope(SalaryRunDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -160,7 +160,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: UpdateSalaryRunSchema },
-  response: { success: SalaryRunDetail },
+  response: { success: dataEnvelope(SalaryRunDetail) },
 })
 
 export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -306,7 +306,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: z.object({}) },
+  response: { success: NoBodyResponse },
 })
 
 export const DELETE = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/salary-runs/route.ts b/app/api/v1/companies/[companyId]/salary-runs/route.ts
index 25427b04..5b337a49 100644
--- a/app/api/v1/companies/[companyId]/salary-runs/route.ts
+++ b/app/api/v1/companies/[companyId]/salary-runs/route.ts
@@ -20,7 +20,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateSalaryRunSchema } from '@/lib/api/schemas'
@@ -229,7 +229,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateSalaryRunSchema },
-  response: { success: SalaryRunCreated },
+  response: { success: dataEnvelope(SalaryRunCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/approve/route.ts b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/approve/route.ts
index 6aa07902..34808ab6 100644
--- a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/approve/route.ts
+++ b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/approve/route.ts
@@ -14,7 +14,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { eventBus } from '@/lib/events'
@@ -56,7 +56,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SupplierInvoiceApproved },
+  response: { success: dataEnvelope(SupplierInvoiceApproved) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/credit/route.ts b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/credit/route.ts
index fbc3d328..99444a4a 100644
--- a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/credit/route.ts
+++ b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/credit/route.ts
@@ -20,7 +20,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -102,7 +102,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: true,
-  response: { success: SupplierInvoiceCredited },
+  response: { success: dataEnvelope(SupplierInvoiceCredited) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/mark-paid/route.ts b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/mark-paid/route.ts
index 6deee803..2ab4865f 100644
--- a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/mark-paid/route.ts
+++ b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/mark-paid/route.ts
@@ -17,7 +17,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -85,7 +85,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: MarkSupplierInvoicePaidSchema },
-  response: { success: SupplierInvoicePaidResponse },
+  response: { success: dataEnvelope(SupplierInvoicePaidResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/route.ts b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/route.ts
index 04be8e51..a92cbb4e 100644
--- a/app/api/v1/companies/[companyId]/supplier-invoices/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/supplier-invoices/[id]/route.ts
@@ -16,7 +16,7 @@ import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
 import { parseExpand } from '@/lib/api/v1/expand'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { UpdateSupplierInvoiceSchema } from '@/lib/api/schemas'
@@ -110,7 +110,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: SupplierInvoiceDetail },
+  response: { success: dataEnvelope(SupplierInvoiceDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -197,7 +197,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: V1PatchSupplierInvoiceSchema },
-  response: { success: SupplierInvoiceDetail },
+  response: { success: dataEnvelope(SupplierInvoiceDetail) },
 })
 
 export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/supplier-invoices/route.ts b/app/api/v1/companies/[companyId]/supplier-invoices/route.ts
index cbf6a0ac..a9f12884 100644
--- a/app/api/v1/companies/[companyId]/supplier-invoices/route.ts
+++ b/app/api/v1/companies/[companyId]/supplier-invoices/route.ts
@@ -29,7 +29,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -329,7 +329,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateSupplierInvoiceSchema },
-  response: { success: SupplierInvoiceCreated },
+  response: { success: dataEnvelope(SupplierInvoiceCreated) },
 })
 
 interface ComputedItem {
diff --git a/app/api/v1/companies/[companyId]/suppliers/[id]/route.ts b/app/api/v1/companies/[companyId]/suppliers/[id]/route.ts
index 83abfb68..3206db7b 100644
--- a/app/api/v1/companies/[companyId]/suppliers/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/suppliers/[id]/route.ts
@@ -16,7 +16,7 @@ import { z } from 'zod'
 import { noContent, ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
 import { parseExpand } from '@/lib/api/v1/expand'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope, NoBodyResponse } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { UpdateSupplierSchema } from '@/lib/api/schemas'
@@ -112,7 +112,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: SupplierDetail },
+  response: { success: dataEnvelope(SupplierDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -242,7 +242,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: UpdateSupplierSchema },
-  response: { success: SupplierDetail },
+  response: { success: dataEnvelope(SupplierDetail) },
 })
 
 export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -452,7 +452,7 @@ registerEndpoint({
   idempotent: true,
   reversible: true,
   dryRunSupported: true,
-  response: { success: z.object({}) },
+  response: { success: NoBodyResponse },
 })
 
 export const DELETE = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/suppliers/bulk-create/route.ts b/app/api/v1/companies/[companyId]/suppliers/bulk-create/route.ts
index 7dde060a..79781871 100644
--- a/app/api/v1/companies/[companyId]/suppliers/bulk-create/route.ts
+++ b/app/api/v1/companies/[companyId]/suppliers/bulk-create/route.ts
@@ -17,7 +17,7 @@ import { z } from 'zod'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateSupplierSchema } from '@/lib/api/schemas'
@@ -96,7 +96,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: BulkCreateRequest },
-  response: { success: BulkCreateResponse },
+  response: { success: dataEnvelope(BulkCreateResponse) },
 })
 
 interface ResultItem {
diff --git a/app/api/v1/companies/[companyId]/suppliers/route.ts b/app/api/v1/companies/[companyId]/suppliers/route.ts
index 94dea686..f51df953 100644
--- a/app/api/v1/companies/[companyId]/suppliers/route.ts
+++ b/app/api/v1/companies/[companyId]/suppliers/route.ts
@@ -21,7 +21,7 @@ import {
   encodeDefaultCursor,
   parsePaginationParams,
 } from '@/lib/api/v1/pagination'
-import { registerEndpoint, listEnvelope } from '@/lib/api/v1/registry'
+import { registerEndpoint, listEnvelope, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { CreateSupplierSchema } from '@/lib/api/schemas'
@@ -307,7 +307,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateSupplierSchema },
-  response: { success: SupplierCreated },
+  response: { success: dataEnvelope(SupplierCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/[id]/categorize/route.ts b/app/api/v1/companies/[companyId]/transactions/[id]/categorize/route.ts
index b29f6e0c..72851aac 100644
--- a/app/api/v1/companies/[companyId]/transactions/[id]/categorize/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/[id]/categorize/route.ts
@@ -16,7 +16,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -89,7 +89,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CategorizeTransactionSchema },
-  response: { success: CategorizeResponse },
+  response: { success: dataEnvelope(CategorizeResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/[id]/match-invoice/route.ts b/app/api/v1/companies/[companyId]/transactions/[id]/match-invoice/route.ts
index f3706226..e3e4a490 100644
--- a/app/api/v1/companies/[companyId]/transactions/[id]/match-invoice/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/[id]/match-invoice/route.ts
@@ -18,7 +18,7 @@
  */
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { MatchInvoiceSchema } from '@/lib/api/schemas'
@@ -87,7 +87,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   request: { body: MatchInvoiceSchema },
-  response: { success: MatchInvoiceResponse },
+  response: { success: dataEnvelope(MatchInvoiceResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/[id]/match-supplier-invoice/route.ts b/app/api/v1/companies/[companyId]/transactions/[id]/match-supplier-invoice/route.ts
index 339fd3ba..01247c47 100644
--- a/app/api/v1/companies/[companyId]/transactions/[id]/match-supplier-invoice/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/[id]/match-supplier-invoice/route.ts
@@ -7,7 +7,7 @@
  */
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { MatchSupplierInvoiceSchema } from '@/lib/api/schemas'
@@ -67,7 +67,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   request: { body: MatchSupplierInvoiceSchema },
-  response: { success: MatchSIResponse },
+  response: { success: dataEnvelope(MatchSIResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/[id]/route.ts b/app/api/v1/companies/[companyId]/transactions/[id]/route.ts
index dece2cd9..6e7c8514 100644
--- a/app/api/v1/companies/[companyId]/transactions/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/[id]/route.ts
@@ -6,7 +6,7 @@
  */
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -75,7 +75,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: TransactionDetail },
+  response: { success: dataEnvelope(TransactionDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/[id]/uncategorize/route.ts b/app/api/v1/companies/[companyId]/transactions/[id]/uncategorize/route.ts
index 2908e2cd..d9787b96 100644
--- a/app/api/v1/companies/[companyId]/transactions/[id]/uncategorize/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/[id]/uncategorize/route.ts
@@ -12,7 +12,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { reverseEntry } from '@/lib/bookkeeping/engine'
@@ -51,7 +51,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false, // The reversal itself cannot be reversed via this endpoint.
   dryRunSupported: true,
-  response: { success: UncategorizeResponse },
+  response: { success: dataEnvelope(UncategorizeResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/transactions/batch-categorize/route.ts b/app/api/v1/companies/[companyId]/transactions/batch-categorize/route.ts
index e199d18f..dd36d46c 100644
--- a/app/api/v1/companies/[companyId]/transactions/batch-categorize/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/batch-categorize/route.ts
@@ -12,7 +12,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { checkPeriodLock } from '@/lib/api/v1/check-period-lock'
@@ -102,7 +102,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: BatchRequest },
-  response: { success: BatchResponse },
+  response: { success: dataEnvelope(BatchResponse) },
 })
 
 interface Item {
diff --git a/app/api/v1/companies/[companyId]/transactions/ingest/route.ts b/app/api/v1/companies/[companyId]/transactions/ingest/route.ts
index 2ac383ca..0007997d 100644
--- a/app/api/v1/companies/[companyId]/transactions/ingest/route.ts
+++ b/app/api/v1/companies/[companyId]/transactions/ingest/route.ts
@@ -18,7 +18,7 @@
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { ingestTransactions } from '@/lib/transactions/ingest'
@@ -99,7 +99,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: IngestRequest },
-  response: { success: IngestResponse },
+  response: { success: dataEnvelope(IngestResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/voucher-gap-explanations/route.ts b/app/api/v1/companies/[companyId]/voucher-gap-explanations/route.ts
index 03e67c99..0666d80c 100644
--- a/app/api/v1/companies/[companyId]/voucher-gap-explanations/route.ts
+++ b/app/api/v1/companies/[companyId]/voucher-gap-explanations/route.ts
@@ -19,7 +19,7 @@
 import { z } from 'zod'
 import { created } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -83,7 +83,7 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: true,
   request: { body: CreateVoucherGapExplanation },
-  response: { success: VoucherGapExplanationCreated },
+  response: { success: dataEnvelope(VoucherGapExplanationCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/webhooks/[id]/rotate-secret/route.ts b/app/api/v1/companies/[companyId]/webhooks/[id]/rotate-secret/route.ts
index 93af6f30..70e73f33 100644
--- a/app/api/v1/companies/[companyId]/webhooks/[id]/rotate-secret/route.ts
+++ b/app/api/v1/companies/[companyId]/webhooks/[id]/rotate-secret/route.ts
@@ -25,7 +25,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { generateWebhookSecret } from '@/lib/webhooks/signing'
@@ -66,7 +66,7 @@ registerEndpoint({
   idempotent: false,
   reversible: false,
   dryRunSupported: false,
-  response: { success: RotateSecretResponse },
+  response: { success: dataEnvelope(RotateSecretResponse) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/webhooks/[id]/route.ts b/app/api/v1/companies/[companyId]/webhooks/[id]/route.ts
index d25d61c1..91e3a62c 100644
--- a/app/api/v1/companies/[companyId]/webhooks/[id]/route.ts
+++ b/app/api/v1/companies/[companyId]/webhooks/[id]/route.ts
@@ -19,7 +19,7 @@
 import { z } from 'zod'
 import { ok, noContent } from '@/lib/api/v1/response'
 import { dryRunPreview } from '@/lib/api/v1/dry-run'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope, NoBodyResponse } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { validateWebhookUrl } from '@/lib/webhooks/url-guard'
@@ -91,7 +91,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: WebhookDetail },
+  response: { success: dataEnvelope(WebhookDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -153,7 +153,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: PatchWebhookSchema },
-  response: { success: WebhookDetail },
+  response: { success: dataEnvelope(WebhookDetail) },
 })
 
 export const PATCH = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
@@ -299,7 +299,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: z.object({ deleted: z.boolean() }) },
+  response: { success: NoBodyResponse },
 })
 
 export const DELETE = withApiV1<{ params: Promise<{ companyId: string; id: string }> }>(
diff --git a/app/api/v1/companies/[companyId]/webhooks/[id]/test/route.ts b/app/api/v1/companies/[companyId]/webhooks/[id]/test/route.ts
index e71f2e9e..29e2fe3a 100644
--- a/app/api/v1/companies/[companyId]/webhooks/[id]/test/route.ts
+++ b/app/api/v1/companies/[companyId]/webhooks/[id]/test/route.ts
@@ -10,7 +10,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 
@@ -49,10 +49,10 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   response: {
-    success: z.object({
+    success: dataEnvelope(z.object({
       webhook_delivery_id: z.string().uuid(),
       status: z.literal('pending'),
-    }),
+    })),
   },
 })
 
diff --git a/app/api/v1/companies/[companyId]/webhooks/route.ts b/app/api/v1/companies/[companyId]/webhooks/route.ts
index 4a3c2129..87acdbfb 100644
--- a/app/api/v1/companies/[companyId]/webhooks/route.ts
+++ b/app/api/v1/companies/[companyId]/webhooks/route.ts
@@ -209,7 +209,7 @@ registerEndpoint({
   reversible: true,
   dryRunSupported: true,
   request: { body: CreateWebhookSchema },
-  response: { success: WebhookCreated },
+  response: { success: dataEnvelope(WebhookCreated) },
 })
 
 export const POST = withApiV1<{ params: Promise<{ companyId: string }> }>(
diff --git a/app/api/v1/health/route.ts b/app/api/v1/health/route.ts
index 034687f5..b3bb3e50 100644
--- a/app/api/v1/health/route.ts
+++ b/app/api/v1/health/route.ts
@@ -7,7 +7,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { API_V1_VERSION } from '@/lib/api/v1/version'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 
@@ -45,7 +45,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: HealthResponse },
+  response: { success: dataEnvelope(HealthResponse) },
 })
 
 export const GET = withApiV1('health.check', async (_request, ctx) => {
diff --git a/app/api/v1/operations/[id]/route.ts b/app/api/v1/operations/[id]/route.ts
index 5bbadc4c..9d5ad717 100644
--- a/app/api/v1/operations/[id]/route.ts
+++ b/app/api/v1/operations/[id]/route.ts
@@ -16,7 +16,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { getOperation } from '@/lib/api/v1/operations'
@@ -76,7 +76,7 @@ registerEndpoint({
   idempotent: true,
   reversible: false,
   dryRunSupported: false,
-  response: { success: OperationDetail },
+  response: { success: dataEnvelope(OperationDetail) },
 })
 
 export const GET = withApiV1<{ params: Promise<{ id: string }> }>(
diff --git a/app/api/v1/webhook-deliveries/[id]/retry/route.ts b/app/api/v1/webhook-deliveries/[id]/retry/route.ts
index b3b07e42..61f554b1 100644
--- a/app/api/v1/webhook-deliveries/[id]/retry/route.ts
+++ b/app/api/v1/webhook-deliveries/[id]/retry/route.ts
@@ -20,7 +20,7 @@
 
 import { z } from 'zod'
 import { ok } from '@/lib/api/v1/response'
-import { registerEndpoint } from '@/lib/api/v1/registry'
+import { registerEndpoint, dataEnvelope } from '@/lib/api/v1/registry'
 import { withApiV1 } from '@/lib/api/v1/with-api-v1'
 import { v1ErrorResponse, v1ErrorResponseFromCode } from '@/lib/api/v1/errors'
 import { minimisePayload } from '@/lib/webhooks/handler'
@@ -59,10 +59,10 @@ registerEndpoint({
   reversible: false,
   dryRunSupported: false,
   response: {
-    success: z.object({
+    success: dataEnvelope(z.object({
       webhook_delivery_id: z.string().uuid(),
       status: z.literal('pending'),
-    }),
+    })),
   },
 })
 
diff --git a/lib/api/v1/__tests__/response-envelope-contract.test.ts b/lib/api/v1/__tests__/response-envelope-contract.test.ts
new file mode 100644
index 00000000..2eec4ae0
--- /dev/null
+++ b/lib/api/v1/__tests__/response-envelope-contract.test.ts
@@ -0,0 +1,131 @@
+/**
+ * Response-envelope contract test.
+ *
+ * Every v1 handler returns the canonical `{ data, meta }` envelope — `ok()` and
+ * `created()` wrap a single object, `paginated()` wraps an array, both stamping
+ * the shared `meta` block (see `lib/api/v1/response.ts`). The OpenAPI generator,
+ * however, derives each endpoint's documented body purely from its registered
+ * `response.success` Zod schema, and that schema is NOT validated at runtime —
+ * so nothing stops a route from declaring a shape the handler never sends.
+ *
+ * That is exactly what issue #794 found: every list endpoint declared a bare
+ * `{ <name>: [...] }` object that no handler emits. #802 fixed the list
+ * endpoints (via `listEnvelope`/`dataEnvelope`); the same drift was latent on
+ * the single-resource and write endpoints, which declared the bare resource
+ * schema instead of `{ data, meta }`.
+ *
+ * This test is the regression guard the issue asked for. It asserts EVERY
+ * JSON-returning endpoint declares the `{ data, meta }` envelope with the shared
+ * `ResponseMetaSchema` — so a new endpoint that forgets to wrap its schema
+ * (list OR single) fails CI here instead of shipping a lying spec. Binary
+ * downloads (`response.contentType`) and 204 No Content endpoints
+ * (`NoBodyResponse`) carry no JSON body and are the only exemptions.
+ */
+
+import { describe, expect, it } from 'vitest'
+import { z } from 'zod'
+import { listEndpoints, ResponseMetaSchema, NoBodyResponse, listEnvelope, dataEnvelope } from '../registry'
+// Side-effect import — every route file's registerEndpoint() runs at module
+// load time and populates the shared ENDPOINTS map.
+import '../load-routes'
+
+/** Binary downloads (PDF, SIE text) declare a non-JSON contentType. */
+function isBinary(success: { contentType?: string }): boolean {
+  return !!success.contentType && success.contentType !== 'application/json'
+}
+
+describe('v1 response envelope contract', () => {
+  const endpoints = listEndpoints()
+
+  it('every JSON endpoint declares the { data, meta } envelope with the shared meta schema', () => {
+    // Accumulate every violation so a failing run names ALL offending endpoints
+    // at once (a fresh route that forgets to wrap, plus any that drift later),
+    // instead of failing one-at-a-time across many edit cycles.
+    const violations: string[] = []
+
+    for (const ep of endpoints) {
+      const ctx = `${ep.method} ${ep.path} (${ep.operation})`
+
+      // Exemptions: binary bodies and 204-no-content have no JSON envelope.
+      if (isBinary(ep.response)) continue
+      if (ep.response.success === NoBodyResponse) continue
+
+      const success = ep.response.success
+      if (!(success instanceof z.ZodObject)) {
+        violations.push(`${ctx}: response.success is not a { data, meta } object — wrap it with listEnvelope()/dataEnvelope() (or use NoBodyResponse for 204 / response.contentType for binary).`)
+        continue
+      }
+
+      const shape = (success as z.ZodObject<z.ZodRawShape>).shape
+      const keys = Object.keys(shape).sort()
+      if (keys.length !== 2 || keys[0] !== 'data' || keys[1] !== 'meta') {
+        violations.push(`${ctx}: top-level keys must be [data, meta] — found [${keys.join(', ')}]. The handler returns { data, meta }; declare it with listEnvelope()/dataEnvelope().`)
+        continue
+      }
+
+      // Reference equality: both envelope helpers wire in this exact schema, so
+      // a hand-rolled `{ data, meta: z.object({...}) }` that drifts from the
+      // real meta block is rejected too.
+      if (shape.meta !== ResponseMetaSchema) {
+        violations.push(`${ctx}: meta is not the shared ResponseMetaSchema (use listEnvelope()/dataEnvelope(), don't hand-roll the envelope).`)
+      }
+    }
+
+    expect(
+      violations,
+      `\n${violations.length} v1 endpoint(s) declare a response.success that doesn't match the { data, meta } envelope the handler actually returns:\n\n${violations.map((v) => `  • ${v}`).join('\n')}\n`,
+    ).toEqual([])
+  })
+
+  it('list endpoints expose data as an array (the paginated() envelope)', () => {
+    // Detect list endpoints structurally: their `data` is a Zod array. This is
+    // the half of the contract that maps onto paginated() specifically — guards
+    // against a list endpoint drifting from `{ data: [...] }` back to a bare
+    // `{ <name>: [...] }` (which would drop the array out of `data` entirely).
+    const arrayDataEndpoints = endpoints.filter((ep) => {
+      const s = ep.response.success
+      return s instanceof z.ZodObject && (s as z.ZodObject<z.ZodRawShape>).shape.data instanceof z.ZodArray
+    })
+
+    // The 10 cursor-paginated list endpoints (companies, customers, suppliers,
+    // invoices, supplier-invoices, journal-entries, transactions, employees,
+    // salary-runs, webhook deliveries). accounts/fiscal-periods/webhooks nest
+    // their array under a named key inside `data`, so they use dataEnvelope and
+    // are intentionally NOT counted here. A drop below this floor means a
+    // paginated endpoint silently lost its `data: [...]` shape.
+    expect(
+      arrayDataEndpoints.length,
+      `expected the known paginated list endpoints to keep data: z.array(...); found only ${arrayDataEndpoints.length}`,
+    ).toBeGreaterThanOrEqual(10)
+
+    for (const ep of arrayDataEndpoints) {
+      const shape = (ep.response.success as z.ZodObject<z.ZodRawShape>).shape
+      expect(
+        shape.meta === ResponseMetaSchema,
+        `${ep.method} ${ep.path}: list envelope meta must be the shared ResponseMetaSchema`,
+      ).toBe(true)
+    }
+  })
+
+  it('listEnvelope() and dataEnvelope() produce the canonical { data, meta } shape', () => {
+    const list = listEnvelope(z.object({ id: z.string() }))
+    expect(list instanceof z.ZodObject).toBe(true)
+    expect(Object.keys(list.shape).sort()).toEqual(['data', 'meta'])
+    expect(list.shape.data instanceof z.ZodArray).toBe(true)
+    expect(list.shape.meta === ResponseMetaSchema).toBe(true)
+
+    const data = dataEnvelope(z.object({ id: z.string() }))
+    expect(data instanceof z.ZodObject).toBe(true)
+    expect(Object.keys(data.shape).sort()).toEqual(['data', 'meta'])
+    expect(data.shape.data instanceof z.ZodObject).toBe(true)
+    expect(data.shape.meta === ResponseMetaSchema).toBe(true)
+  })
+
+  it('the shared meta schema carries request_id + api_version', () => {
+    // The envelope helpers are only correct if meta itself is well-formed.
+    expect(ResponseMetaSchema instanceof z.ZodObject).toBe(true)
+    const metaKeys = Object.keys(ResponseMetaSchema.shape)
+    expect(metaKeys).toContain('request_id')
+    expect(metaKeys).toContain('api_version')
+  })
+})
diff --git a/lib/api/v1/registry.ts b/lib/api/v1/registry.ts
index 374002e4..ad6e2872 100644
--- a/lib/api/v1/registry.ts
+++ b/lib/api/v1/registry.ts
@@ -21,15 +21,31 @@ import type { ZodTypeAny } from 'zod'
 import type { ApiKeyScope } from '@/lib/auth/api-keys'
 import { API_V1_VERSION } from './version'
 
+/**
+ * The audit block surfaced inline on write responses (see `AuditBlock` in
+ * `lib/api/v1/response.ts`) so an agent gets the voucher number / audit-trail
+ * URL without a second round-trip. Every field is optional.
+ */
+const ResponseAuditSchema = z.object({
+  voucher_number: z.string().optional(),
+  voucher_url: z.string().optional(),
+  audit_trail_url: z.string().optional(),
+  immutable_at: z.string().optional(),
+})
+
 /**
  * The `meta` block echoed in every v1 response envelope (see
  * `lib/api/v1/response.ts`). List endpoints additionally populate
- * `next_cursor`; it is absent on the final page.
+ * `next_cursor`; it is absent on the final page. Writes may surface an
+ * `audit` block, and soft-degraded `?expand=` responses a `partial_expansions`
+ * list — both optional, so reads and lists omit them.
  */
 export const ResponseMetaSchema = z.object({
   request_id: z.string(),
   api_version: z.string(),
   next_cursor: z.string().nullable().optional(),
+  audit: ResponseAuditSchema.optional(),
+  partial_expansions: z.array(z.string()).optional(),
 })
 
 /**
@@ -66,6 +82,18 @@ export function dataEnvelope<T extends ZodTypeAny>(data: T) {
   })
 }
 
+/**
+ * Sentinel `response.success` for endpoints that return 204 No Content with an
+ * empty body — e.g. DELETE handlers calling `noContent()`. The OpenAPI
+ * generator emits a bare `204` response (no schema) for these instead of a
+ * `200 { data, meta }`, and the envelope contract test exempts them.
+ *
+ * Identified by REFERENCE equality, so every 204 route MUST import this exact
+ * constant rather than declaring its own `z.object({})` — that is what lets the
+ * generator and the contract test recognise the "no body" intent.
+ */
+export const NoBodyResponse = z.object({})
+
 export type HttpMethod = 'GET' | 'POST' | 'PATCH' | 'PUT' | 'DELETE'
 
 export type ActionRisk = 'low' | 'medium' | 'high'
@@ -327,6 +355,13 @@ export function generateOpenApiSpec(serverUrl: string): OpenApiSpec {
       ? { [def.response.contentType]: { schema: { type: 'string', format: 'binary' } } }
       : { 'application/json': { schema: zodToJsonSchema(def.response.success) } }
 
+    // 204 No Content endpoints (DELETEs returning noContent()) carry no body —
+    // emit a bare 204 instead of a 200 { data, meta } so the spec stops
+    // advertising a response shape these handlers never send.
+    const successResponse = def.response.success === NoBodyResponse
+      ? { '204': { description: 'No Content' } }
+      : { '200': { description: 'Success', content: successContent } }
+
     const operationDef: Record<string, unknown> = {
       operationId: def.operation,
       summary: def.summary,
@@ -343,10 +378,7 @@ export function generateOpenApiSpec(serverUrl: string): OpenApiSpec {
       'x-dry-run-supported': def.dryRunSupported,
       ...(def.scope ? { 'x-required-scope': def.scope } : {}),
       responses: {
-        '200': {
-          description: 'Success',
-          content: successContent,
-        },
+        ...successResponse,
         '400': { description: 'Validation error', $ref: '#/components/responses/Error' },
         '401': { description: 'Unauthorized', $ref: '#/components/responses/Error' },
         '403': { description: 'Insufficient scope', $ref: '#/components/responses/Error' },
diff --git a/lib/reports/__tests__/ar-ledger.test.ts b/lib/reports/__tests__/ar-ledger.test.ts
index 2426e34f..654b94f9 100644
--- a/lib/reports/__tests__/ar-ledger.test.ts
+++ b/lib/reports/__tests__/ar-ledger.test.ts
@@ -9,7 +9,7 @@ let results: Array<{ data?: unknown; error?: unknown }>
 
 function makeBuilder() {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'range']) {
+  for (const m of ['select', 'eq', 'in', 'order', 'range']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   b.single = vi.fn().mockImplementation(async () => results[resultIdx++] ?? { data: null, error: null })
diff --git a/lib/reports/__tests__/continuity-check.test.ts b/lib/reports/__tests__/continuity-check.test.ts
index 6a9a1661..dbcd4d88 100644
--- a/lib/reports/__tests__/continuity-check.test.ts
+++ b/lib/reports/__tests__/continuity-check.test.ts
@@ -9,7 +9,7 @@ let mockResults: Record<string, MockResult[]>
 
 function makeBuilder(tableName: string) {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'lt', 'neq', 'range', 'update']) {
+  for (const m of ['select', 'eq', 'in', 'lt', 'neq', 'order', 'range', 'update']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   const consume = (): MockResult => {
diff --git a/lib/reports/__tests__/general-ledger.test.ts b/lib/reports/__tests__/general-ledger.test.ts
index f789391c..48f3dcb8 100644
--- a/lib/reports/__tests__/general-ledger.test.ts
+++ b/lib/reports/__tests__/general-ledger.test.ts
@@ -124,6 +124,54 @@ describe('generateGeneralLedger', () => {
     expect(acc1930.closing_balance).toBe(1250)
   })
 
+  it('does not double a balance when an unstable page boundary re-serves a line (#790/#791)', async () => {
+    // Reproduces the doubling bug's mechanism: a paginated query whose order
+    // was not stable can return the same journal_entry_line on two pages.
+    // Page 1 must be a FULL page (PAGE_SIZE rows) so fetchAllRows fetches a
+    // second page; page 2 re-serves the 5010 line. dedupeBy(line id) must
+    // collapse it so the single 4000 posting totals 4000, not 8000.
+    const PAGE_SIZE = 1000
+    const filler = Array.from({ length: PAGE_SIZE - 1 }, (_, i) => ({
+      id: `f${i}`,
+      account_number: '1930',
+      debit_amount: 0,
+      credit_amount: 0,
+      journal_entries: { entry_date: '2024-01-02', voucher_number: 1, voucher_series: 'A', description: 'filler', source_type: 'manual' },
+    }))
+    const rentLine = {
+      id: 'rent-line-1',
+      account_number: '5010',
+      debit_amount: 4000,
+      credit_amount: 0,
+      journal_entries: { entry_date: '2024-01-15', voucher_number: 2, voucher_series: 'A', description: 'Lokalhyra', source_type: 'manual' },
+    }
+
+    mockResults = {
+      fiscal_periods: [
+        { data: { period_start: '2024-01-01', period_end: '2024-12-31', opening_balance_entry_id: null }, error: null },
+      ],
+      journal_entry_lines: [
+        { data: [...filler, rentLine], error: null }, // page 1 — full → triggers page 2
+        { data: [rentLine], error: null },            // page 2 — duplicate of the 5010 line
+      ],
+      chart_of_accounts: [
+        {
+          data: [
+            { account_number: '1930', account_name: 'Företagskonto' },
+            { account_number: '5010', account_name: 'Lokalhyra' },
+          ],
+          error: null,
+        },
+      ],
+    }
+
+    const report = await generateGeneralLedger(supabase, 'company-1', 'period-1')
+
+    const acc5010 = report.accounts.find((a) => a.account_number === '5010')!
+    expect(acc5010.total_debit).toBe(4000) // not 8000
+    expect(acc5010.lines).toHaveLength(1) // verifikat listed once, not twice
+  })
+
   it('computes opening balance from prior period entries', async () => {
     mockResults = {
       fiscal_periods: [
diff --git a/lib/reports/__tests__/journal-register.test.ts b/lib/reports/__tests__/journal-register.test.ts
index 6ee2e480..91ce0403 100644
--- a/lib/reports/__tests__/journal-register.test.ts
+++ b/lib/reports/__tests__/journal-register.test.ts
@@ -67,6 +67,54 @@ describe('generateJournalRegister', () => {
     expect(report.period).toEqual({ start: '2024-01-01', end: '2024-12-31' })
   })
 
+  it('does not double an entry when an unstable page boundary re-serves a line (#790/#793)', async () => {
+    // Page 1 is a FULL page so fetchAllRows fetches page 2, which re-serves
+    // the 5010 line of voucher 2. dedupeBy(line id) must collapse it so the
+    // grundbok lists the voucher once with a 4000 (not 8000) total.
+    const PAGE_SIZE = 1000
+    const filler = Array.from({ length: PAGE_SIZE - 1 }, (_, i) => ({
+      id: `f${i}`,
+      account_number: '1930',
+      debit_amount: 0,
+      credit_amount: 0,
+      journal_entry_id: 'e0',
+      journal_entries: { id: 'e0', entry_date: '2024-01-02', voucher_number: 1, voucher_series: 'A', description: 'filler', source_type: 'manual', status: 'posted' },
+    }))
+    const rentLine = {
+      id: 'rent-line-1',
+      account_number: '5010',
+      debit_amount: 4000,
+      credit_amount: 0,
+      journal_entry_id: 'e1',
+      journal_entries: { id: 'e1', entry_date: '2024-01-15', voucher_number: 2, voucher_series: 'A', description: 'Lokalhyra', source_type: 'manual', status: 'posted' },
+    }
+
+    mockResults = {
+      fiscal_periods: [
+        { data: { period_start: '2024-01-01', period_end: '2024-12-31' }, error: null },
+      ],
+      journal_entry_lines: [
+        { data: [...filler, rentLine], error: null }, // page 1 — full → triggers page 2
+        { data: [rentLine], error: null },            // page 2 — duplicate of the 5010 line
+      ],
+      chart_of_accounts: [
+        {
+          data: [
+            { account_number: '1930', account_name: 'Företagskonto' },
+            { account_number: '5010', account_name: 'Lokalhyra' },
+          ],
+          error: null,
+        },
+      ],
+    }
+
+    const report = await generateJournalRegister(supabase, 'company-1', 'period-1')
+
+    const voucher2 = report.entries.find((e) => e.voucher_number === 2)!
+    expect(voucher2.total_debit).toBe(4000) // not 8000
+    expect(voucher2.lines).toHaveLength(1) // listed once, not twice
+  })
+
   it('produces entries in registration order with correct totals', async () => {
     mockResults = {
       fiscal_periods: [
diff --git a/lib/reports/__tests__/monthly-breakdown.test.ts b/lib/reports/__tests__/monthly-breakdown.test.ts
index 83e54c91..3f25246b 100644
--- a/lib/reports/__tests__/monthly-breakdown.test.ts
+++ b/lib/reports/__tests__/monthly-breakdown.test.ts
@@ -5,6 +5,20 @@ const { supabase, mockResult } = createMockSupabase()
 
 import { generateMonthlyBreakdown } from '../monthly-breakdown'
 
+// Minimal chainable query mock: every filter/order method returns the same
+// object; .single()/.range() resolve to the queued result. Tolerant of
+// query-shape changes such as an added .order() (see fetch-all.ts ordering
+// invariant) so the tests don't hardcode the exact method chain.
+function chain(result: unknown) {
+  const c: Record<string, unknown> = {}
+  for (const m of ['select', 'eq', 'in', 'gte', 'lte', 'lt', 'neq', 'order']) {
+    c[m] = () => c
+  }
+  c.single = () => Promise.resolve(result)
+  c.range = () => Promise.resolve(result)
+  return c
+}
+
 beforeEach(() => {
   vi.clearAllMocks()
 })
@@ -33,38 +47,9 @@ describe('generateMonthlyBreakdown', () => {
     let callCount = 0
     supabase.from.mockImplementation(() => {
       callCount++
-      if (callCount === 1) {
-        // fiscal_periods query
-        return {
-          select: () => ({
-            eq: () => ({
-              eq: () => ({
-                single: () =>
-                  Promise.resolve({
-                    data: { period_start: '2024-01-01', period_end: '2024-12-31' },
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }
-      }
-      // journal_entry_lines query
-      return {
-        select: () => ({
-          eq: () => ({
-            eq: () => ({
-              eq: () => ({
-                range: () =>
-                  Promise.resolve({
-                    data: [],
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }),
-      }
+      return callCount === 1
+        ? chain({ data: { period_start: '2024-01-01', period_end: '2024-12-31' }, error: null })
+        : chain({ data: [], error: null })
     })
 
     const result = await generateMonthlyBreakdown(supabase as never, 'company-1', 'period-1')
@@ -79,61 +64,37 @@ describe('generateMonthlyBreakdown', () => {
     let callCount = 0
     supabase.from.mockImplementation(() => {
       callCount++
-      if (callCount === 1) {
-        return {
-          select: () => ({
-            eq: () => ({
-              eq: () => ({
-                single: () =>
-                  Promise.resolve({
-                    data: { period_start: '2024-01-01', period_end: '2024-03-31' },
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }
-      }
-      return {
-        select: () => ({
-          eq: () => ({
-            eq: () => ({
-              eq: () => ({
-                range: () =>
-                  Promise.resolve({
-                    data: [
-                      {
-                        account_number: '3001',
-                        debit_amount: 0,
-                        credit_amount: 10000,
-                        journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '5010',
-                        debit_amount: 3000,
-                        credit_amount: 0,
-                        journal_entry: { entry_date: '2024-01-20', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '3001',
-                        debit_amount: 0,
-                        credit_amount: 5000,
-                        journal_entry: { entry_date: '2024-02-10', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '6200',
-                        debit_amount: 1500,
-                        credit_amount: 0,
-                        journal_entry: { entry_date: '2024-02-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                    ],
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }),
-      }
+      return callCount === 1
+        ? chain({ data: { period_start: '2024-01-01', period_end: '2024-03-31' }, error: null })
+        : chain({
+            data: [
+              {
+                account_number: '3001',
+                debit_amount: 0,
+                credit_amount: 10000,
+                journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '5010',
+                debit_amount: 3000,
+                credit_amount: 0,
+                journal_entry: { entry_date: '2024-01-20', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '3001',
+                debit_amount: 0,
+                credit_amount: 5000,
+                journal_entry: { entry_date: '2024-02-10', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '6200',
+                debit_amount: 1500,
+                credit_amount: 0,
+                journal_entry: { entry_date: '2024-02-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+            ],
+            error: null,
+          })
     })
 
     const result = await generateMonthlyBreakdown(supabase as never, 'company-1', 'period-1')
@@ -160,61 +121,37 @@ describe('generateMonthlyBreakdown', () => {
     let callCount = 0
     supabase.from.mockImplementation(() => {
       callCount++
-      if (callCount === 1) {
-        return {
-          select: () => ({
-            eq: () => ({
-              eq: () => ({
-                single: () =>
-                  Promise.resolve({
-                    data: { period_start: '2024-01-01', period_end: '2024-01-31' },
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }
-      }
-      return {
-        select: () => ({
-          eq: () => ({
-            eq: () => ({
-              eq: () => ({
-                range: () =>
-                  Promise.resolve({
-                    data: [
-                      {
-                        account_number: '1930',
-                        debit_amount: 10000,
-                        credit_amount: 0,
-                        journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '2611',
-                        debit_amount: 0,
-                        credit_amount: 2500,
-                        journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '8400',
-                        debit_amount: 500,
-                        credit_amount: 0,
-                        journal_entry: { entry_date: '2024-01-20', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                      {
-                        account_number: '8300',
-                        debit_amount: 0,
-                        credit_amount: 200,
-                        journal_entry: { entry_date: '2024-01-25', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
-                      },
-                    ],
-                    error: null,
-                  }),
-              }),
-            }),
-          }),
-        }),
-      }
+      return callCount === 1
+        ? chain({ data: { period_start: '2024-01-01', period_end: '2024-01-31' }, error: null })
+        : chain({
+            data: [
+              {
+                account_number: '1930',
+                debit_amount: 10000,
+                credit_amount: 0,
+                journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '2611',
+                debit_amount: 0,
+                credit_amount: 2500,
+                journal_entry: { entry_date: '2024-01-15', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '8400',
+                debit_amount: 500,
+                credit_amount: 0,
+                journal_entry: { entry_date: '2024-01-20', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+              {
+                account_number: '8300',
+                debit_amount: 0,
+                credit_amount: 200,
+                journal_entry: { entry_date: '2024-01-25', status: 'posted', user_id: 'user-1', fiscal_period_id: 'period-1' },
+              },
+            ],
+            error: null,
+          })
     })
 
     const result = await generateMonthlyBreakdown(supabase as never, 'company-1', 'period-1')
diff --git a/lib/reports/__tests__/periodisk-sammanstallning.test.ts b/lib/reports/__tests__/periodisk-sammanstallning.test.ts
index 9f0afd6a..714e90b9 100644
--- a/lib/reports/__tests__/periodisk-sammanstallning.test.ts
+++ b/lib/reports/__tests__/periodisk-sammanstallning.test.ts
@@ -9,7 +9,7 @@ let results: Array<{ data?: unknown; error?: unknown }>
 
 function makeBuilder() {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'gte', 'lte', 'lt', 'or', 'not', 'range']) {
+  for (const m of ['select', 'eq', 'in', 'gte', 'lte', 'lt', 'or', 'not', 'order', 'range']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   b.single = vi.fn().mockImplementation(async () => results[resultIdx++] ?? { data: null, error: null })
diff --git a/lib/reports/__tests__/supplier-ledger.test.ts b/lib/reports/__tests__/supplier-ledger.test.ts
index a969610c..f314e259 100644
--- a/lib/reports/__tests__/supplier-ledger.test.ts
+++ b/lib/reports/__tests__/supplier-ledger.test.ts
@@ -9,7 +9,7 @@ let results: Array<{ data?: unknown; error?: unknown }>
 
 function makeBuilder() {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'range']) {
+  for (const m of ['select', 'eq', 'in', 'order', 'range']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   b.single = vi.fn().mockImplementation(async () => results[resultIdx++] ?? { data: null, error: null })
diff --git a/lib/reports/__tests__/trial-balance.test.ts b/lib/reports/__tests__/trial-balance.test.ts
index 81d7aa77..206629b6 100644
--- a/lib/reports/__tests__/trial-balance.test.ts
+++ b/lib/reports/__tests__/trial-balance.test.ts
@@ -11,7 +11,7 @@ let mockResults: Record<string, MockResult[]>
 
 function makeBuilder(tableName: string) {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'lt', 'lte', 'gte', 'neq', 'range']) {
+  for (const m of ['select', 'eq', 'in', 'lt', 'lte', 'gte', 'neq', 'order', 'range']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   const consume = (): MockResult => {
diff --git a/lib/reports/__tests__/vat-declaration.test.ts b/lib/reports/__tests__/vat-declaration.test.ts
index cf614b36..a337896d 100644
--- a/lib/reports/__tests__/vat-declaration.test.ts
+++ b/lib/reports/__tests__/vat-declaration.test.ts
@@ -9,7 +9,7 @@ let results: Array<{ data?: unknown; error?: unknown }>
 
 function makeBuilder() {
   const b: Record<string, unknown> = {}
-  for (const m of ['select', 'eq', 'in', 'gte', 'lte', 'lt', 'or', 'not', 'range']) {
+  for (const m of ['select', 'eq', 'in', 'gte', 'lte', 'lt', 'or', 'not', 'order', 'range']) {
     b[m] = vi.fn().mockReturnValue(b)
   }
   b.single = vi.fn().mockImplementation(async () => results[resultIdx++] ?? { data: null, error: null })
diff --git a/lib/reports/ar-ledger.ts b/lib/reports/ar-ledger.ts
index 45c2d882..85052a88 100644
--- a/lib/reports/ar-ledger.ts
+++ b/lib/reports/ar-ledger.ts
@@ -69,6 +69,8 @@ export async function generateARLedger(
         .select('*, customer:customers(id, name)')
         .eq('company_id', companyId)
         .in('status', ['sent', 'overdue', 'credited'])
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to)
     )
   } catch {
diff --git a/lib/reports/full-archive-export.ts b/lib/reports/full-archive-export.ts
index eba58f31..d4dc0ac8 100644
--- a/lib/reports/full-archive-export.ts
+++ b/lib/reports/full-archive-export.ts
@@ -209,6 +209,8 @@ export async function estimateArchiveSize(
         .eq('company_id', companyId)
         .eq('fiscal_period_id', periodId)
         .in('status', ['posted', 'reversed'])
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to)
     )
     const ids = periodEntryIds.map((e) => e.id)
@@ -345,6 +347,8 @@ async function writeDocuments(
         )
         .eq('company_id', companyId)
         .not('journal_entry_id', 'is', null)
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to)
     )
 
@@ -730,6 +734,9 @@ async function buildEntryToPeriodMap(
     query = query.in('fiscal_period_id', periodIds)
   }
 
+  // Stable total order for correct paging (see fetch-all.ts).
+  query = query.order('id', { ascending: true })
+
   const entries = await fetchAllRows<{ id: string; fiscal_period_id: string }>(({ from, to }) =>
     query.range(from, to)
   )
diff --git a/lib/reports/general-ledger.ts b/lib/reports/general-ledger.ts
index 90a8efa2..1d724d42 100644
--- a/lib/reports/general-ledger.ts
+++ b/lib/reports/general-ledger.ts
@@ -83,6 +83,7 @@ export async function generateGeneralLedger(
   // Supabase types !inner joins as arrays; for many-to-one (line → entry)
   // it returns a single object at runtime. Cast via `as any` on the query.
   const rawLines = await fetchAllRows<{
+    id: string
     account_number: string
     debit_amount: number
     credit_amount: number
@@ -97,7 +98,7 @@ export async function generateGeneralLedger(
   }>(({ from, to }) => {
     let query = supabase
       .from('journal_entry_lines')
-      .select('account_number, debit_amount, credit_amount, journal_entry_id, journal_entries!inner(entry_date, voucher_number, voucher_series, description, source_type, company_id, fiscal_period_id, status)')
+      .select('id, account_number, debit_amount, credit_amount, journal_entry_id, journal_entries!inner(entry_date, voucher_number, voucher_series, description, source_type, company_id, fiscal_period_id, status)')
       .eq('journal_entries.company_id', companyId)
       .eq('journal_entries.fiscal_period_id', periodId)
       .in('journal_entries.status', ['posted', 'reversed'])
@@ -106,9 +107,13 @@ export async function generateGeneralLedger(
       query = query.neq('journal_entry_id', obEntryId)
     }
 
+    // Stable total order on the line PK — paging is only correct with a
+    // deterministic order, else rows duplicate/skip across pages and balances
+    // double or accounts vanish (see fetch-all.ts ordering invariant). The
+    // report re-sorts lines per account below, so this order is invisible.
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    return query.range(from, to) as any
-  })
+    return query.order('id', { ascending: true }).range(from, to) as any
+  }, { dedupeBy: (r) => r.id })
 
   if (rawLines.length === 0 && openingBalances.size === 0) {
     return { accounts: [], period: { start: period.period_start, end: period.period_end } }
@@ -120,6 +125,7 @@ export async function generateGeneralLedger(
       .from('chart_of_accounts')
       .select('account_number, account_name')
       .eq('company_id', companyId)
+      .order('account_number', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/ink2/ink2-engine.ts b/lib/reports/ink2/ink2-engine.ts
index a09fd6ba..47dd90aa 100644
--- a/lib/reports/ink2/ink2-engine.ts
+++ b/lib/reports/ink2/ink2-engine.ts
@@ -745,6 +745,7 @@ export async function generateINK2Declaration(
       .from('chart_of_accounts')
       .select('account_number, account_name')
       .eq('company_id', companyId)
+      .order('account_number', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/journal-register.ts b/lib/reports/journal-register.ts
index a7b1ff5c..378e33b1 100644
--- a/lib/reports/journal-register.ts
+++ b/lib/reports/journal-register.ts
@@ -62,6 +62,7 @@ export async function generateJournalRegister(
   // Supabase types !inner joins as arrays; for many-to-one (line → entry)
   // it returns a single object at runtime. Cast via `as any` on the query.
   const rawLines = await fetchAllRows<{
+    id: string
     account_number: string
     debit_amount: number
     credit_amount: number
@@ -75,16 +76,18 @@ export async function generateJournalRegister(
       source_type: string
       status: string
     }
-  }>(({ from, to }) =>
-    supabase
+  }>(({ from, to }) => {
+    return supabase
       .from('journal_entry_lines')
-      .select('account_number, debit_amount, credit_amount, journal_entry_id, journal_entries!inner(id, entry_date, voucher_number, voucher_series, description, source_type, status, company_id, fiscal_period_id)')
+      .select('id, account_number, debit_amount, credit_amount, journal_entry_id, journal_entries!inner(id, entry_date, voucher_number, voucher_series, description, source_type, status, company_id, fiscal_period_id)')
       .eq('journal_entries.company_id', companyId)
       .eq('journal_entries.fiscal_period_id', periodId)
       .in('journal_entries.status', ['posted', 'reversed'])
+      // Stable total order on the line PK — without it, rows duplicate/skip
+      // across pages and entries appear twice or go missing (see fetch-all.ts).
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      .range(from, to) as any
-  )
+      .order('id', { ascending: true }).range(from, to) as any
+  }, { dedupeBy: (r) => r.id })
 
   if (rawLines.length === 0) {
     return { entries: [], total_entries: 0, total_debit: 0, total_credit: 0, period: { start: period.period_start, end: period.period_end } }
@@ -96,6 +99,7 @@ export async function generateJournalRegister(
       .from('chart_of_accounts')
       .select('account_number, account_name')
       .eq('company_id', companyId)
+      .order('account_number', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/monthly-breakdown.ts b/lib/reports/monthly-breakdown.ts
index c61a2259..89a0b292 100644
--- a/lib/reports/monthly-breakdown.ts
+++ b/lib/reports/monthly-breakdown.ts
@@ -63,6 +63,8 @@ export async function generateMonthlyBreakdown(
         .eq('journal_entries.fiscal_period_id', fiscalPeriodId)
         .eq('journal_entries.company_id', companyId)
         .eq('journal_entries.status', 'posted')
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to)
     )
   } catch {
diff --git a/lib/reports/ne-bilaga/ne-engine.ts b/lib/reports/ne-bilaga/ne-engine.ts
index 404f09fe..eb3ef39a 100644
--- a/lib/reports/ne-bilaga/ne-engine.ts
+++ b/lib/reports/ne-bilaga/ne-engine.ts
@@ -213,6 +213,7 @@ export async function generateNEDeclaration(
       .from('chart_of_accounts')
       .select('account_number, account_name')
       .eq('company_id', companyId)
+      .order('account_number', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/opening-balances.ts b/lib/reports/opening-balances.ts
index 7e552ba4..c65f7125 100644
--- a/lib/reports/opening-balances.ts
+++ b/lib/reports/opening-balances.ts
@@ -41,16 +41,20 @@ export async function getOpeningBalances(
     // for consistency (avoids silent truncation) and joins journal_entries
     // to enforce company_id ownership (defense in depth alongside RLS).
     const obLines = await fetchAllRows<{
+      id: string
       account_number: string
       debit_amount: number
       credit_amount: number
     }>(({ from, to }) =>
       supabase
         .from('journal_entry_lines')
-        .select('account_number, debit_amount, credit_amount, journal_entries!inner(company_id)')
+        .select('id, account_number, debit_amount, credit_amount, journal_entries!inner(company_id)')
         .eq('journal_entry_id', obEntryId)
         .eq('journal_entries.company_id', companyId)
-        .range(from, to)
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
+        .range(from, to),
+      { dedupeBy: (r) => r.id }
     )
 
     for (const line of obLines) {
diff --git a/lib/reports/periodisk-sammanstallning.ts b/lib/reports/periodisk-sammanstallning.ts
index 6b1a3d8d..860738f9 100644
--- a/lib/reports/periodisk-sammanstallning.ts
+++ b/lib/reports/periodisk-sammanstallning.ts
@@ -200,6 +200,8 @@ export async function generatePeriodiskSammanstallning(
       .in('journal_entries.source_type', ['invoice_created', 'credit_note'])
       .gte('journal_entries.entry_date', start)
       .lte('journal_entries.entry_date', end)
+      // Stable total order for correct paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to) as unknown as PromiseLike<{ data: RawLine[] | null; error: { message: string } | null }>,
   )
 
@@ -229,6 +231,8 @@ export async function generatePeriodiskSammanstallning(
           )
         `)
         .in('id', invoiceIds)
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to) as unknown as PromiseLike<{ data: RawInvoice[] | null; error: { message: string } | null }>,
     )
     for (const inv of invoices) invoiceMap.set(inv.id, inv)
diff --git a/lib/reports/rc-basis-gaps.ts b/lib/reports/rc-basis-gaps.ts
index 7af6514e..1a0cc712 100644
--- a/lib/reports/rc-basis-gaps.ts
+++ b/lib/reports/rc-basis-gaps.ts
@@ -90,6 +90,7 @@ function pickEntry(row: RcLineRow): EntryFields | null {
 }
 
 interface SiblingLineRow {
+  id: string
   journal_entry_id: string
   account_number: string
   debit_amount: number
@@ -122,6 +123,8 @@ export async function findRcBasisGaps(
       .eq('journal_entries.status', 'posted')
       .gte('journal_entries.entry_date', start)
       .lte('journal_entries.entry_date', end)
+      // Stable total order for correct paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to),
   )) as RcLineRow[]
 
@@ -132,9 +135,12 @@ export async function findRcBasisGaps(
   const siblingLines = await fetchAllRows<SiblingLineRow>(({ from, to }) =>
     supabase
       .from('journal_entry_lines')
-      .select('journal_entry_id, account_number, debit_amount, credit_amount')
+      .select('id, journal_entry_id, account_number, debit_amount, credit_amount')
       .in('journal_entry_id', entryIds)
+      // Stable total order for correct paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to),
+    { dedupeBy: (r) => r.id },
   )
 
   const basisByEntry = new Map<string, number>()
diff --git a/lib/reports/salary-journal.ts b/lib/reports/salary-journal.ts
index 9660a8a7..dfa005cc 100644
--- a/lib/reports/salary-journal.ts
+++ b/lib/reports/salary-journal.ts
@@ -73,6 +73,9 @@ export async function generateSalaryJournal(
       .eq('salary_runs.period_year', year)
       .eq('salary_runs.status', 'booked')
       .order('created_at')
+      // id tiebreaker — created_at is not unique, so it alone is not a stable
+      // total order for paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/supplier-ledger.ts b/lib/reports/supplier-ledger.ts
index 72c6b21f..4a67d943 100644
--- a/lib/reports/supplier-ledger.ts
+++ b/lib/reports/supplier-ledger.ts
@@ -47,6 +47,8 @@ export async function generateSupplierLedger(
         .select('*, supplier:suppliers(id, name)')
         .eq('company_id', companyId)
         .in('status', ['registered', 'approved', 'partially_paid', 'overdue'])
+        // Stable total order for correct paging (see fetch-all.ts).
+        .order('id', { ascending: true })
         .range(from, to)
     )
   } catch {
diff --git a/lib/reports/trial-balance.ts b/lib/reports/trial-balance.ts
index a56ddbfb..f4e45a35 100644
--- a/lib/reports/trial-balance.ts
+++ b/lib/reports/trial-balance.ts
@@ -60,13 +60,14 @@ export async function generateTrialBalance(
     options.fromDate > period.period_start
   ) {
     const priorLines = await fetchAllRows<{
+      id: string
       account_number: string
       debit_amount: number
       credit_amount: number
     }>(({ from, to }) => {
       let query = supabase
         .from('journal_entry_lines')
-        .select('account_number, debit_amount, credit_amount, journal_entries!inner(company_id, fiscal_period_id, status, source_type, entry_date)')
+        .select('id, account_number, debit_amount, credit_amount, journal_entries!inner(company_id, fiscal_period_id, status, source_type, entry_date)')
         .eq('journal_entries.company_id', companyId)
         .eq('journal_entries.fiscal_period_id', fiscalPeriodId)
         .in('journal_entries.status', ['posted', 'reversed'])
@@ -81,8 +82,9 @@ export async function generateTrialBalance(
         query = query.neq('journal_entries.source_type', 'year_end')
       }
 
-      return query.range(from, to)
-    })
+      // Stable total order on the line PK for correct paging (see fetch-all.ts).
+      return query.order('id', { ascending: true }).range(from, to)
+    }, { dedupeBy: (r) => r.id })
 
     for (const line of priorLines) {
       const existing = openingBalances.get(line.account_number) || { debit: 0, credit: 0 }
@@ -100,13 +102,14 @@ export async function generateTrialBalance(
   // be missed from both IB and period. The window is sub-second and the
   // consequence is a single stale report — acceptable.
   const lines = await fetchAllRows<{
+    id: string
     account_number: string
     debit_amount: number
     credit_amount: number
   }>(({ from, to }) => {
     let query = supabase
       .from('journal_entry_lines')
-      .select('account_number, debit_amount, credit_amount, journal_entries!inner(company_id, fiscal_period_id, status, source_type, entry_date)')
+      .select('id, account_number, debit_amount, credit_amount, journal_entries!inner(company_id, fiscal_period_id, status, source_type, entry_date)')
       .eq('journal_entries.company_id', companyId)
       .eq('journal_entries.fiscal_period_id', fiscalPeriodId)
       .in('journal_entries.status', ['posted', 'reversed'])
@@ -132,8 +135,9 @@ export async function generateTrialBalance(
       query = query.neq('journal_entries.source_type', 'year_end')
     }
 
-    return query.range(from, to)
-  })
+    // Stable total order on the line PK for correct paging (see fetch-all.ts).
+    return query.order('id', { ascending: true }).range(from, to)
+  }, { dedupeBy: (r) => r.id })
 
   if (lines.length === 0 && openingBalances.size === 0) {
     return { rows: [], totalDebit: 0, totalCredit: 0, isBalanced: true }
@@ -149,6 +153,7 @@ export async function generateTrialBalance(
       .from('chart_of_accounts')
       .select('account_number, account_name, account_class')
       .eq('company_id', companyId)
+      .order('account_number', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/vacation-liability.ts b/lib/reports/vacation-liability.ts
index 56a7a2fb..080d6feb 100644
--- a/lib/reports/vacation-liability.ts
+++ b/lib/reports/vacation-liability.ts
@@ -61,6 +61,9 @@ export async function generateVacationLiability(
       .eq('is_active', true)
       .not('vacation_rule', 'in', '(none,semesterersattning)')
       .order('last_name')
+      // id tiebreaker — last_name is not unique, so it alone is not a stable
+      // total order for paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to)
   )
 
@@ -80,6 +83,8 @@ export async function generateVacationLiability(
       .eq('company_id', companyId)
       .eq('salary_runs.period_year', year)
       .eq('salary_runs.status', 'booked')
+      // Stable total order for correct paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/reports/vat-declaration.ts b/lib/reports/vat-declaration.ts
index 2c10f67d..70ea4bca 100644
--- a/lib/reports/vat-declaration.ts
+++ b/lib/reports/vat-declaration.ts
@@ -283,6 +283,8 @@ export async function calculateVatDeclaration(
       .in('journal_entries.status', ['posted', 'reversed'])
       .gte('journal_entries.entry_date', start)
       .lte('journal_entries.entry_date', end)
+      // Stable total order for correct paging (see fetch-all.ts).
+      .order('id', { ascending: true })
       .range(from, to)
   )
 
diff --git a/lib/supabase/__tests__/fetch-all.test.ts b/lib/supabase/__tests__/fetch-all.test.ts
new file mode 100644
index 00000000..e5d49dac
--- /dev/null
+++ b/lib/supabase/__tests__/fetch-all.test.ts
@@ -0,0 +1,88 @@
+import { describe, it, expect } from 'vitest'
+import { fetchAllRows } from '../fetch-all'
+
+const PAGE_SIZE = 1000
+
+type Row = { id: string; value?: number }
+
+/**
+ * Build a queryFn that serves predefined pages keyed by the `from` offset.
+ * Mirrors how `fetchAllRows` drives PostgREST `.range(from, to)`.
+ */
+function pagedQuery(pages: Record<number, Row[]>) {
+  return ({ from }: { from: number; to: number }) =>
+    Promise.resolve({ data: pages[from] ?? [], error: null })
+}
+
+function makeRows(start: number, count: number): Row[] {
+  return Array.from({ length: count }, (_, i) => ({ id: String(start + i), value: 1 }))
+}
+
+describe('fetchAllRows', () => {
+  it('returns a single page as-is and stops (page < PAGE_SIZE)', async () => {
+    const rows = makeRows(0, 3)
+    const out = await fetchAllRows<Row>(pagedQuery({ 0: rows }))
+    expect(out).toHaveLength(3)
+    expect(out.map((r) => r.id)).toEqual(['0', '1', '2'])
+  })
+
+  it('paginates across multiple pages and concatenates in order', async () => {
+    const page1 = makeRows(0, PAGE_SIZE) // full page → fetch continues
+    const page2 = makeRows(PAGE_SIZE, 5) // partial page → stop
+    const out = await fetchAllRows<Row>(pagedQuery({ 0: page1, [PAGE_SIZE]: page2 }))
+    expect(out).toHaveLength(PAGE_SIZE + 5)
+    expect(out[0].id).toBe('0')
+    expect(out[out.length - 1].id).toBe(String(PAGE_SIZE + 4))
+  })
+
+  it('throws when the query returns an error', async () => {
+    await expect(
+      fetchAllRows<Row>(() => Promise.resolve({ data: null, error: { message: 'boom' } })),
+    ).rejects.toThrow('boom')
+  })
+
+  it('returns [] when the first page is empty', async () => {
+    const out = await fetchAllRows<Row>(pagedQuery({ 0: [] }))
+    expect(out).toEqual([])
+  })
+
+  // ── The regression-critical behaviour: an unstable cross-page order ──
+  // (a query missing a stable .order()) can return the same row on two
+  // pages. This is the mechanism behind the doubled-balance bugs (#790/#791).
+
+  it('dedupeBy drops a row duplicated across page boundaries (keeps first)', async () => {
+    const page1 = makeRows(0, PAGE_SIZE) // ids 0..999
+    // Unstable order: page 2 re-serves id "999" (already on page 1) plus a new id.
+    const page2: Row[] = [
+      { id: '999', value: 1 },
+      { id: '1000', value: 1 },
+    ]
+    const out = await fetchAllRows<Row>(
+      pagedQuery({ 0: page1, [PAGE_SIZE]: page2 }),
+      { dedupeBy: (r) => r.id },
+    )
+    // 1001 unique ids (0..1000), the duplicate "999" removed → no doubling.
+    expect(out).toHaveLength(PAGE_SIZE + 1)
+    const ids = out.map((r) => r.id)
+    expect(ids.filter((id) => id === '999')).toHaveLength(1)
+    expect(new Set(ids).size).toBe(out.length)
+  })
+
+  it('without dedupeBy, cross-page duplicates pass through (unsafe default)', async () => {
+    const page1 = makeRows(0, PAGE_SIZE)
+    const page2: Row[] = [{ id: '999', value: 1 }]
+    const out = await fetchAllRows<Row>(pagedQuery({ 0: page1, [PAGE_SIZE]: page2 }))
+    expect(out).toHaveLength(PAGE_SIZE + 1)
+    expect(out.map((r) => r.id).filter((id) => id === '999')).toHaveLength(2)
+  })
+
+  it('dedupeBy is a no-op for a single page (no cross-page duplicates possible)', async () => {
+    const rows: Row[] = [
+      { id: 'a' },
+      { id: 'b' },
+      { id: 'a' }, // an intra-page repeat is left untouched — single page is trusted
+    ]
+    const out = await fetchAllRows<Row>(pagedQuery({ 0: rows }), { dedupeBy: (r) => r.id })
+    expect(out).toHaveLength(3)
+  })
+})
diff --git a/lib/supabase/fetch-all.ts b/lib/supabase/fetch-all.ts
index f1cb7c96..4352b74f 100644
--- a/lib/supabase/fetch-all.ts
+++ b/lib/supabase/fetch-all.ts
@@ -1,11 +1,41 @@
+import { createLogger } from '@/lib/logger'
+
+const log = createLogger('fetch-all')
+
 const PAGE_SIZE = 1000
 
+export interface FetchAllRowsOptions<T> {
+  /**
+   * Stable de-duplication key. When supplied AND more than one page was
+   * fetched, rows are de-duplicated by this key after all pages are collected,
+   * and a warn is logged if any duplicates were dropped.
+   *
+   * This is a safety net, NOT the fix: PostgREST `.range()` paging is only
+   * correct when the underlying query has a stable TOTAL order (see the
+   * ordering invariant below). If a duplicate is ever observed here it means a
+   * caller's query is missing that `.order()` — the warn surfaces the
+   * regression in logs instead of letting it silently double financial totals.
+   * Note this only catches *duplicates*; *skipped* rows can only be prevented
+   * by ordering on a unique column at the call site.
+   */
+  dedupeBy?: (row: T) => string | number
+}
+
 /**
  * Fetches all rows from a Supabase query by paginating through results.
  * Overcomes PostgREST's default 1000-row limit.
  *
+ * **Ordering invariant:** any query that can return more than `PAGE_SIZE` rows
+ * MUST `.order()` on a unique column (e.g. the table's `id` PK). Postgres
+ * returns rows in an undefined order that can differ between the two `.range()`
+ * requests, so without a stable total order, rows on a page boundary are
+ * silently DUPLICATED and/or SKIPPED across pages. For aggregating reports
+ * (general ledger, trial balance, grundbok) that means doubled or missing
+ * balances. Order is purely for paging stability — callers that need a
+ * different display order should re-sort after fetching.
+ *
  * The callback receives `{ from, to }` range values — append `.range(from, to)`
- * to your query builder:
+ * to your query builder, AFTER a stable `.order()`:
  *
  * ```ts
  * const accounts = await fetchAllRows(({ from, to }) =>
@@ -13,27 +43,62 @@ const PAGE_SIZE = 1000
  *     .from('chart_of_accounts')
  *     .select('account_number, account_name')
  *     .eq('company_id', companyId)
+ *     .order('account_number', { ascending: true }) // stable total order
  *     .range(from, to)
  * )
  * ```
+ *
+ * Pass `{ dedupeBy }` as defense-in-depth for queries where a missing/regressed
+ * order would corrupt money:
+ *
+ * ```ts
+ * const lines = await fetchAllRows(
+ *   ({ from, to }) => q.order('id').range(from, to),
+ *   { dedupeBy: (r) => r.id },
+ * )
+ * ```
  */
 export async function fetchAllRows<T>(
   queryFn: (range: { from: number; to: number }) => PromiseLike<{
     data: T[] | null
     error: { message: string } | null
-  }>
+  }>,
+  options?: FetchAllRowsOptions<T>
 ): Promise<T[]> {
   const allRows: T[] = []
   let from = 0
+  let pages = 0
 
   while (true) {
     const { data, error } = await queryFn({ from, to: from + PAGE_SIZE - 1 })
     if (error) throw new Error(error.message)
     if (!data || data.length === 0) break
     allRows.push(...data)
+    pages += 1
     if (data.length < PAGE_SIZE) break
     from += PAGE_SIZE
   }
 
+  // Duplicates are only possible across page boundaries, so single-page results
+  // never need the dedup pass.
+  if (options?.dedupeBy && pages > 1) {
+    const seen = new Set<string | number>()
+    const deduped: T[] = []
+    for (const row of allRows) {
+      const key = options.dedupeBy(row)
+      if (seen.has(key)) continue
+      seen.add(key)
+      deduped.push(row)
+    }
+    const dropped = allRows.length - deduped.length
+    if (dropped > 0) {
+      log.warn(
+        'fetchAllRows dropped duplicate rows across pages — a paginated query is missing a stable .order() on a unique column',
+        { dropped, total: allRows.length, pages }
+      )
+      return deduped
+    }
+  }
+
   return allRows
 }