diff --git a/lib/__tests__/jmap-file-capability.test.ts b/lib/__tests__/jmap-file-capability.test.ts
new file mode 100644
index 00000000..0871a13c
--- /dev/null
+++ b/lib/__tests__/jmap-file-capability.test.ts
@@ -0,0 +1,76 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { JMAPClient } from '../jmap/client';
+
+// Session where the SERVER advertises FileNode (session.capabilities) but the
+// per-account accountCapabilities can independently include or omit it. This
+// models the #563 scenario: a Stalwart role that revokes jmap-file-node-*
+// permissions drops the capability from the account while the server still
+// advertises it globally.
+function makeSession(accountCapabilities: Record<string, unknown>, isPersonal = true) {
+  return {
+    capabilities: {
+      'urn:ietf:params:jmap:core': {},
+      'urn:ietf:params:jmap:filenode': {},
+    },
+    accounts: {
+      'acct-1': { name: 'test', isPersonal, accountCapabilities },
+    },
+    primaryAccounts: { 'urn:ietf:params:jmap:mail': 'acct-1' },
+    apiUrl: 'https://mail.example.com/jmap/api',
+    downloadUrl: 'https://mail.example.com/jmap/download/{accountId}/{blobId}/{name}',
+    uploadUrl: 'https://mail.example.com/jmap/upload/{accountId}/',
+    eventSourceUrl: 'https://mail.example.com/jmap/eventsource',
+  };
+}
+
+function mockFetchResponse(status: number, body?: unknown): Response {
+  return new Response(body ? JSON.stringify(body) : null, {
+    status,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}
+
+async function connect(accountCapabilities: Record<string, unknown>, isPersonal = true): Promise<JMAPClient> {
+  const fetchSpy = vi.spyOn(globalThis, 'fetch');
+  fetchSpy.mockResolvedValueOnce(mockFetchResponse(200, makeSession(accountCapabilities, isPersonal)));
+  const client = new JMAPClient('https://mail.example.com', 'user@test.com', 'pass123');
+  await client.connect();
+  fetchSpy.mockReset();
+  return client;
+}
+
+describe('JMAPClient.supportsFiles (#563 - account-scoped capability)', () => {
+  let fetchSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    fetchSpy = vi.spyOn(globalThis, 'fetch');
+  });
+
+  afterEach(() => {
+    fetchSpy.mockRestore();
+  });
+
+  it('returns true when the account advertises the filenode capability', async () => {
+    const client = await connect({ 'urn:ietf:params:jmap:filenode': {} });
+    expect(client.supportsFiles()).toBe(true);
+  });
+
+  it('returns false when the server advertises filenode but the account does not (#563)', async () => {
+    // The revoked-permission case: server-wide capability present, account omits it.
+    const client = await connect({ 'urn:ietf:params:jmap:mail': {} });
+    expect(client.supportsFiles()).toBe(false);
+  });
+
+  it('treats non-personal (shared/group) accounts as capable even without per-account advertisement', async () => {
+    const client = await connect({}, /* isPersonal */ false);
+    expect(client.supportsFiles()).toBe(true);
+  });
+
+  it('probeFileNodeSupport does not probe (no network call) when the account is explicitly denied', async () => {
+    const client = await connect({ 'urn:ietf:params:jmap:mail': {} });
+    fetchSpy.mockClear();
+    await expect(client.probeFileNodeSupport()).resolves.toBe(false);
+    // Explicit per-account denial must short-circuit before any FileNode/query probe.
+    expect(fetchSpy).not.toHaveBeenCalled();
+  });
+});
diff --git a/lib/jmap/client-interface.ts b/lib/jmap/client-interface.ts
index 68c4ce1a..5a7d4223 100644
--- a/lib/jmap/client-interface.ts
+++ b/lib/jmap/client-interface.ts
@@ -40,7 +40,7 @@ export interface IJMAPClient {
   supportsContacts(): boolean;
   supportsCalendars(): boolean;
   supportsSieve(): boolean;
-  supportsFiles(): boolean;
+  supportsFiles(accountId?: string): boolean;
 
   // ── Push / state ──────────────────────────────────────────────
   setupPushNotifications(): boolean;
diff --git a/lib/jmap/client.ts b/lib/jmap/client.ts
index 39e9110b..05bf6505 100644
--- a/lib/jmap/client.ts
+++ b/lib/jmap/client.ts
@@ -5209,14 +5209,30 @@ export class JMAPClient implements IJMAPClient {
 
   // ─── JMAP FileNode methods (draft-ietf-jmap-filenode) ───
 
-  supportsFiles(): boolean {
-    return this.hasCapability("urn:ietf:params:jmap:filenode");
+  supportsFiles(accountId?: string): boolean {
+    // Gate on the ACCOUNT capability, not the server-wide session capability.
+    // A server can advertise urn:ietf:params:jmap:filenode while a specific
+    // account has its jmap-file-node-* permissions revoked, in which case the
+    // capability is absent from that account's accountCapabilities and every
+    // FileNode action fails with an authorization error (#563). Mirror
+    // getFilesCapableAccountIds(): non-personal (shared/group) accounts don't
+    // always advertise per-account, so treat those as capable.
+    const id = accountId || this.accountId;
+    const account = this.accounts[id];
+    if (!account) return false;
+    return !!account.accountCapabilities?.["urn:ietf:params:jmap:filenode"] || !account.isPersonal;
   }
 
   async probeFileNodeSupport(): Promise<boolean> {
     // Some servers support FileNode without advertising a specific capability.
     // Try a minimal FileNode/query to detect support at runtime.
     if (this.supportsFiles()) return true;
+    // If the server advertises FileNode server-wide but this account's
+    // accountCapabilities omits it, that's an explicit per-account denial (#563)
+    // - don't probe (the probe would only confirm the revoked account can't use
+    // it, or worse mislead). Only fall through for servers that don't advertise
+    // the capability at all.
+    if (this.hasCapability("urn:ietf:params:jmap:filenode")) return false;
     if (!this.apiUrl) return false;
     try {
       const accountId = this.getFilesAccountId();