diff --git a/packages/core/src/ksef/ksef.adapter.ts b/packages/core/src/ksef/ksef.adapter.ts
index fbd5271..3f37638 100644
--- a/packages/core/src/ksef/ksef.adapter.ts
+++ b/packages/core/src/ksef/ksef.adapter.ts
@@ -52,6 +52,7 @@ export class KsefAdapterImpl implements KsefAdapter {
       subjectType,
       pageSize: opts.pageSize,
       pageOffset: opts.pageOffset,
+      includeXml: opts.includeXml,
     })
 
     return result.invoices.map((raw) => ({
diff --git a/packages/core/src/ksef/types.ts b/packages/core/src/ksef/types.ts
index 1e046f4..0130d67 100644
--- a/packages/core/src/ksef/types.ts
+++ b/packages/core/src/ksef/types.ts
@@ -38,6 +38,7 @@ export interface KsefClient {
     subjectType?: KsefSubjectType
     pageSize?: number
     pageOffset?: number
+    includeXml?: boolean
   }): Promise<{ invoices: KsefRawInvoice[]; total: number }>
   sendInvoice(params: {
     token: string
diff --git a/packages/http/src/client.ts b/packages/http/src/client.ts
index 757114f..ccc2e10 100644
--- a/packages/http/src/client.ts
+++ b/packages/http/src/client.ts
@@ -15,7 +15,7 @@ import {
   shouldRefresh,
   type ActiveSession,
 } from './session.js'
-import { fetchInvoices as fetchInvoicesHttp } from './invoices.js'
+import { fetchInvoices as fetchInvoicesHttp, fetchInvoiceXml as fetchInvoiceXmlHttp } from './invoices.js'
 import { fetchUpoXml } from './upo.js'
 import { KsefApiError } from './errors.js'
 import { fetchKsefTokenEncryptionKey } from './public-key.js'
@@ -129,6 +129,7 @@ export class KsefHttpClient implements KsefClient {
     subjectType?: 'Subject1' | 'Subject2' | 'Subject3'
     pageSize?: number
     pageOffset?: number
+    includeXml?: boolean
   }): Promise<{ invoices: KsefRawInvoice[]; total: number }> {
     let session = decodeSessionToken(params.token)
     if (!session) {
@@ -151,12 +152,31 @@ export class KsefHttpClient implements KsefClient {
           pageSize: params.pageSize,
           pageOffset: params.pageOffset,
           subjectType: params.subjectType ?? 'Subject2',
+          includeXml: params.includeXml,
         }),
       this.retryOpts,
     )
     return result
   }
 
+  async fetchInvoiceXml(params: { token: string; ksefNumber: string }): Promise<string> {
+    let session = decodeSessionToken(params.token)
+    if (!session) {
+      throw new Error('KsefHttpClient.fetchInvoiceXml: invalid session token')
+    }
+    if (shouldRefresh(session)) {
+      session = await withHttpRetry(
+        () => refreshAccessToken(this.http, session as ActiveSession),
+        this.retryOpts,
+      )
+    }
+    return withHttpRetry(
+      () =>
+        fetchInvoiceXmlHttp(this.http, (session as ActiveSession).accessToken, params.ksefNumber),
+      this.retryOpts,
+    )
+  }
+
   async sendInvoice(): Promise<{ ksefReferenceNumber: string; timestamp: string }> {
     throw new Error(
       'KsefHttpClient.sendInvoice: not implemented in HTTP client MVP — see http_plan.md §H05.5',
diff --git a/packages/mcp/src/tools/sync-invoices.ts b/packages/mcp/src/tools/sync-invoices.ts
index 8f393c0..f529e6a 100644
--- a/packages/mcp/src/tools/sync-invoices.ts
+++ b/packages/mcp/src/tools/sync-invoices.ts
@@ -1,4 +1,6 @@
 import type { Ksefnik } from '@ksefnik/core'
+import { writeFile, mkdir } from 'node:fs/promises'
+import { resolve, isAbsolute, join } from 'node:path'
 import { z } from 'zod'
 
 export const syncInvoicesSchema = z.object({
@@ -11,17 +13,48 @@ export const syncInvoicesSchema = z.object({
    * Defaults to `cost` for backwards compatibility with the MVP.
    */
   subject: z.enum(['sales', 'cost']).optional(),
+  /**
+   * When provided, downloads the full FA(2)/FA(3) XML for each invoice and
+   * saves it to `${saveDir}/${ksefReference}.xml`. Path must be absolute.
+   * Creates the directory if it doesn't exist.
+   */
+  saveDir: z.string().optional(),
 })
 
 export type SyncInvoicesInput = z.infer<typeof syncInvoicesSchema>
 
 export async function syncInvoices(ksef: Ksefnik, input: SyncInvoicesInput) {
   const subjectType = input.subject === 'sales' ? 'Subject1' : 'Subject2'
+  const includeXml = Boolean(input.saveDir)
+
   const invoices = await ksef.invoices.fetch({
     from: input.dateFrom,
     to: input.dateTo,
     nip: input.nip,
     subjectType,
+    includeXml,
   })
-  return { invoices, count: invoices.length, subject: input.subject ?? 'cost' }
+
+  let savedFiles: string[] = []
+  if (input.saveDir) {
+    const dir = isAbsolute(input.saveDir) ? input.saveDir : resolve(input.saveDir)
+    await mkdir(dir, { recursive: true })
+    savedFiles = await Promise.all(
+      invoices
+        .filter((inv) => inv.ksefReference && inv.rawXml)
+        .map(async (inv) => {
+          const path = join(dir, `${inv.ksefReference}.xml`)
+          await writeFile(path, inv.rawXml ?? '', 'utf8')
+          return path
+        }),
+    )
+  }
+
+  return {
+    invoices,
+    count: invoices.length,
+    subject: input.subject ?? 'cost',
+    savedFiles: input.saveDir ? savedFiles : undefined,
+    savedCount: input.saveDir ? savedFiles.length : undefined,
+  }
 }
diff --git a/packages/shared/src/types/ksef-adapter.ts b/packages/shared/src/types/ksef-adapter.ts
index 4054d52..8b62868 100644
--- a/packages/shared/src/types/ksef-adapter.ts
+++ b/packages/shared/src/types/ksef-adapter.ts
@@ -14,6 +14,12 @@ export interface FetchInvoicesOpts {
   subjectType?: InvoiceSubjectType
   pageSize?: number
   pageOffset?: number
+  /**
+   * When true, also fetch the full FA(2)/FA(3) XML body for each invoice via
+   * `GET /invoices/ksef/{ksefNumber}` and put it on `Invoice.rawXml`. Off by
+   * default — metadata alone covers grossAmount/NIPs/dates.
+   */
+  includeXml?: boolean
 }
 
 export interface SendInvoiceInput {