diff --git a/src/lib/__tests__/contact-utils.test.ts b/src/lib/__tests__/contact-utils.test.ts
index 0996391b..ac158b2a 100644
--- a/src/lib/__tests__/contact-utils.test.ts
+++ b/src/lib/__tests__/contact-utils.test.ts
@@ -1,6 +1,8 @@
 import { describe, it, expect } from 'vitest';
 import {
+  deriveFullName,
   getContactDisplayName,
+  getCustomFullName,
   getContactPhotoUri,
   normalizeContactPhotoUri,
   partialDateToString,
@@ -80,3 +82,43 @@ describe('stringToPartialDate', () => {
     }
   });
 });
+
+describe('name.full for the vCard FN (#430)', () => {
+  const person = (full: string | undefined, components: Array<{ kind: string; value: string }>): ContactCard => ({
+    id: 'c',
+    addressBookIds: {},
+    name: { components, isOrdered: true, ...(full !== undefined ? { full } : {}) },
+  });
+
+  it('joins the name components in display order, like the webmail form', () => {
+    expect(deriveFullName([
+      { kind: 'surname', value: 'Doe' },
+      { kind: 'generation', value: 'Jr.' },
+      { kind: 'given', value: ' John ' },
+      { kind: 'title', value: 'Dr.' },
+      { kind: 'given2', value: 'Q' },
+    ])).toBe('Dr. John Q Doe Jr.');
+    // Legacy vCard-style kinds count too.
+    expect(deriveFullName([{ kind: 'prefix', value: 'Ms.' }, { kind: 'given', value: 'Ann' }])).toBe('Ms. Ann');
+    expect(deriveFullName(undefined)).toBe('');
+    expect(deriveFullName([])).toBe('');
+  });
+
+  it('treats a full that repeats the components as derived, so an edit cannot leave it stale', () => {
+    const card = person('John Doe', [{ kind: 'given', value: 'John' }, { kind: 'surname', value: 'Doe' }]);
+    expect(getCustomFullName(card)).toBe('');
+  });
+
+  it('keeps a display name of its own', () => {
+    const card = person('Johnny D', [{ kind: 'given', value: 'John' }, { kind: 'surname', value: 'Doe' }]);
+    expect(getCustomFullName(card)).toBe('Johnny D');
+    expect(getCustomFullName(person('Solo', []))).toBe('Solo');
+    expect(getCustomFullName(person(undefined, [{ kind: 'given', value: 'A' }]))).toBe('');
+  });
+
+  it('treats an organization card whose full is the organization name as derived', () => {
+    const org = person('Acme Corp', []);
+    expect(getCustomFullName(org, 'Acme Corp')).toBe('');
+    expect(getCustomFullName(org, 'Acme Inc')).toBe('Acme Corp');
+  });
+});
diff --git a/src/lib/__tests__/vcard.test.ts b/src/lib/__tests__/vcard.test.ts
index 96e62dc5..da74bca2 100644
--- a/src/lib/__tests__/vcard.test.ts
+++ b/src/lib/__tests__/vcard.test.ts
@@ -8,6 +8,25 @@ import {
 import type { ContactCard } from '../../api/types';
 
 describe('parseVCard', () => {
+  it('keeps FN as name.full so the written card carries the mandatory FN (#430)', () => {
+    const fnOnly = parseVCard('BEGIN:VCARD\r\nVERSION:3.0\r\nFN:John Doe\r\nEND:VCARD');
+    expect(fnOnly[0].name?.full).toBe('John Doe');
+
+    // FN before N: N replaces the components but must keep full.
+    const fnFirst = parseVCard('BEGIN:VCARD\r\nVERSION:3.0\r\nFN:Dr. John Doe Jr.\r\nN:Doe;John;;;\r\nEND:VCARD');
+    expect(fnFirst[0].name?.full).toBe('Dr. John Doe Jr.');
+
+    // N before FN: FN fills full on the existing name.
+    const nFirst = parseVCard('BEGIN:VCARD\r\nVERSION:3.0\r\nN:Doe;John;;;\r\nFN:Dr. John Doe Jr.\r\nEND:VCARD');
+    expect(nFirst[0].name?.full).toBe('Dr. John Doe Jr.');
+    expect(nFirst[0].name?.components?.find((c) => c.kind === 'given')?.value).toBe('John');
+  });
+
+  it('derives name.full from N when a card has no FN (#430)', () => {
+    const [card] = parseVCard('BEGIN:VCARD\r\nVERSION:3.0\r\nN:Doe;John;Q;Dr.;Jr.\r\nEND:VCARD');
+    expect(card.name?.full).toBe('Dr. John Q Doe Jr.');
+  });
+
   it('parses a basic 3.0 card with name, email, and phone', () => {
     const vcf = [
       'BEGIN:VCARD',
diff --git a/src/lib/contact-utils.ts b/src/lib/contact-utils.ts
index 989e6416..09d8bf04 100644
--- a/src/lib/contact-utils.ts
+++ b/src/lib/contact-utils.ts
@@ -1,6 +1,7 @@
 import type {
   ContactCard,
   AnniversaryDate,
+  NameComponent,
   PartialDate,
   Timestamp,
 } from '../api/types';
@@ -59,6 +60,39 @@ export function getPrimaryTitle(contact: ContactCard): string {
   return title?.name || '';
 }
 
+/**
+ * `name.full` derived from the name components in display order (prefix,
+ * given, middle, surname, suffix), as the webmail's form writes it. Every
+ * write should carry `full`: the vCard FN is built from it, FN is mandatory
+ * (RFC 6350 §6.2.1), and strict CardDAV clients such as Apple Contacts drop
+ * cards without it (#430).
+ */
+export function deriveFullName(components: readonly NameComponent[] | undefined): string {
+  const find = (...kinds: string[]) =>
+    components?.find((c) => kinds.includes(c.kind))?.value?.trim() || '';
+  return [
+    find('title', 'prefix'),
+    find('given'),
+    find('given2', 'additional', 'middle'),
+    find('surname'),
+    find('generation', 'suffix'),
+  ].filter(Boolean).join(' ');
+}
+
+/**
+ * The card's `name.full` when it is a display name of its own. Empty when it
+ * only repeats what `deriveFullName` (or, on an organization card, the
+ * organization name) gives, so an edit form re-derives it from the edited
+ * fields on save instead of writing back a stale copy (#430).
+ */
+export function getCustomFullName(contact: ContactCard, orgName?: string): string {
+  const full = contact.name?.full?.trim() || '';
+  if (!full) return '';
+  if (full === deriveFullName(contact.name?.components)) return '';
+  if (orgName && full === orgName.trim()) return '';
+  return full;
+}
+
 export function getContactInitials(contact: ContactCard): string {
   const name = getContactDisplayName(contact).trim();
   if (!name) return '?';
diff --git a/src/lib/vcard.ts b/src/lib/vcard.ts
index f3f99860..71704d9e 100644
--- a/src/lib/vcard.ts
+++ b/src/lib/vcard.ts
@@ -6,6 +6,7 @@ import type {
   PartialDate,
 } from '../api/types';
 import { generateUUID } from './uuid';
+import { deriveFullName } from './contact-utils';
 
 // Convert RFC 9553 AnniversaryDate (PartialDate|Timestamp|string) to vCard date string
 function anniversaryDateToVcardString(date: AnniversaryDate): string {
@@ -573,6 +574,8 @@ function buildContact(raw: Record<string, string[]>): ContactCard | null {
 
       switch (propName) {
         case 'FN':
+          // Keep the verbatim FN in `full` (RFC 9553): it feeds the mandatory
+          // vCard FN on re-export, which strict clients require (#430).
           if (!card.name) {
             const parts = val.split(' ');
             const components: NameComponent[] = [];
@@ -582,7 +585,9 @@ function buildContact(raw: Record<string, string[]>): ContactCard | null {
             } else if (parts.length === 1) {
               components.push({ kind: 'given', value: parts[0] });
             }
-            card.name = { components, isOrdered: true };
+            card.name = { components, isOrdered: true, full: val };
+          } else if (!card.name.full) {
+            card.name.full = val;
           }
           break;
 
@@ -599,7 +604,8 @@ function buildContact(raw: Record<string, string[]>): ContactCard | null {
           if (nParts[0]) components.push({ kind: 'surname', value: nParts[0] });
           if (nParts[4]) components.push({ kind: 'generation', value: nParts[4] });
           if (components.length > 0) {
-            card.name = { components, isOrdered: true };
+            // Preserve `full` captured from FN when FN preceded N.
+            card.name = { ...card.name, components, isOrdered: true };
           }
           break;
         }
@@ -1162,6 +1168,13 @@ function buildContact(raw: Record<string, string[]>): ContactCard | null {
     }
   }
 
+  // A card without FN (invalid, but seen in the wild) still gets a `full`,
+  // derived from N like the contact form does, so the server writes an FN.
+  if (card.name && !card.name.full) {
+    const derived = deriveFullName(card.name.components);
+    if (derived) card.name.full = derived;
+  }
+
   const hasName = (card.name && (card.name.components?.length ?? 0) > 0) || !!card.name?.full;
   const hasEmail = card.emails && Object.keys(card.emails).length > 0;
   // An organization name identifies the card just as well as a personal name.
diff --git a/src/screens/ContactFormScreen.tsx b/src/screens/ContactFormScreen.tsx
index 2abc38ea..5815fb8f 100644
--- a/src/screens/ContactFormScreen.tsx
+++ b/src/screens/ContactFormScreen.tsx
@@ -23,6 +23,7 @@ import { useContactsStore, selectGroupMembers } from '../stores/contacts-store';
 import {
   getContactKeywords, getContactDisplayName, getContactPrimaryEmail,
   normalizeContactPhotoUri, partialDateToString, stringToPartialDate,
+  deriveFullName, getCustomFullName,
 } from '../lib/contact-utils';
 import { splitMailbox } from '../lib/rfc5322-mailbox';
 import Dialog from '../components/Dialog';
@@ -146,7 +147,6 @@ function contactToForm(contact: ContactCard, memberIds: string[]): FormState {
   const middle = findNameComponent(contact, 'given2', 'additional', 'middle');
   const surname = findNameComponent(contact, 'surname');
   const suffix = findNameComponent(contact, 'generation', 'suffix');
-  const full = contact.name?.full || '';
 
   const nicknames = contact.nicknames
     ? Object.values(contact.nicknames).map((n) => n.name || '').filter(Boolean)
@@ -232,6 +232,9 @@ function contactToForm(contact: ContactCard, memberIds: string[]): FormState {
   const isOrg = contact.kind
     ? contact.kind === 'org'
     : !(given || surname) && !!rawOrgs[0]?.name;
+  // Only a display name of its own goes in the field; a derived one is
+  // derived again on save, so it can't go stale when the name changes.
+  const full = getCustomFullName(contact, isOrg ? rawOrgs[0]?.name : undefined);
 
   return {
     isOrg, prefix, given, middle, surname, suffix, full,
@@ -285,9 +288,10 @@ function formToPatch(
     if (form.suffix.trim()) components.push({ kind: 'generation', value: form.suffix.trim() });
   }
 
-  // Without personal name components, carry the organization name in
-  // `name.full` so servers and other clients have something to display.
-  const full = form.full.trim() || (form.isOrg ? orgName : '');
+  // Always send `name.full`: the vCard FN is built from it and is mandatory
+  // (#430). Without personal name components, carry the organization name
+  // so servers and other clients have something to display.
+  const full = form.full.trim() || (form.isOrg ? orgName : deriveFullName(components));
   const name: ContactCard['name'] | undefined =
     components.length > 0 || full
       ? { ...(components.length > 0 ? { components, isOrdered: true } : {}), ...(full ? { full } : {}) }