fix(24-05): quote TXT record values per RFC 1035 character-string format

AWS Route 53 rejects an unquoted TXT Value with:
'InvalidCharacterString (Value should be enclosed in quotation marks)'
— discovered during plan 24-07's live checkpoint (step 2, create) against
a real hosted zone. buildChangeBatch now wraps TXT values in escaped
double quotes, splitting into 255-character segments per RFC 1035's
character-string limit. A/AAAA/CNAME/MX/SRV values pass through
unchanged (only TXT uses the quoted-string wire format).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/services/route53-change-submit.test.ts

@@ -79,6 +79,46 @@ describe('buildChangeBatch', () => {
   it('throws when given record type SOA (case-insensitive)', () => {
     expect(() => buildChangeBatch('UPSERT', { ...baseRecordSet, type: 'soa' })).toThrow(/SOA/i);
   });
+
+  describe('TXT record quoting (RFC 1035 character-string)', () => {
+    it('wraps a plain TXT value in double quotes — AWS rejects an unquoted Value with InvalidCharacterString', () => {
+      const batch = buildChangeBatch('UPSERT', {
+        ...baseRecordSet,
+        type: 'TXT',
+        resourceRecords: [{ value: 'phase24-verification' }],
+      });
+      expect(batch.Changes?.[0].ResourceRecordSet?.ResourceRecords).toEqual([
+        { Value: '"phase24-verification"' },
+      ]);
+    });
+
+    it('escapes embedded double quotes and backslashes before quoting', () => {
+      const batch = buildChangeBatch('UPSERT', {
+        ...baseRecordSet,
+        type: 'TXT',
+        resourceRecords: [{ value: 'v=spf1 include:"weird\\path" ~all' }],
+      });
+      expect(batch.Changes?.[0].ResourceRecordSet?.ResourceRecords?.[0].Value).toBe(
+        '"v=spf1 include:\\"weird\\\\path\\" ~all"'
+      );
+    });
+
+    it('splits a value over 255 characters into multiple quoted segments', () => {
+      const long = 'a'.repeat(300);
+      const batch = buildChangeBatch('UPSERT', {
+        ...baseRecordSet,
+        type: 'TXT',
+        resourceRecords: [{ value: long }],
+      });
+      const value = batch.Changes?.[0].ResourceRecordSet?.ResourceRecords?.[0].Value ?? '';
+      expect(value).toBe(`"${'a'.repeat(255)}" "${'a'.repeat(45)}"`);
+    });
+
+    it('does not quote non-TXT record values', () => {
+      const batch = buildChangeBatch('UPSERT', baseRecordSet);
+      expect(batch.Changes?.[0].ResourceRecordSet?.ResourceRecords).toEqual([{ Value: '1.2.3.4' }]);
+    });
+  });
 });
 
 describe('isRetryableAwsError', () => {

lib/services/route53-change-submit.ts

@@ -28,6 +28,31 @@ import {
 import { getRoute53Client } from './route53-factory';
 
 const ZONE_DELEGATION_TYPES = new Set(['NS', 'SOA']);
+const TXT_MAX_SEGMENT_LENGTH = 255;
+
+/**
+ * TXT (and SPF) records use RFC 1035 character-string RDATA — AWS rejects a
+ * bare, unquoted value with `InvalidCharacterString`. A Value must be one or
+ * more double-quoted segments, each up to 255 bytes; segments longer than
+ * that are split and re-concatenated (segments render back as one string).
+ * Internal backslashes and double quotes must be backslash-escaped before
+ * quoting. A/AAAA/CNAME/MX/SRV values are plain (unquoted) and pass through
+ * `formatResourceRecordValue` unchanged.
+ */
+function formatTxtValue(value: string): string {
+  const escaped = value.replace(/\\/g, '\\\\').replace(/"/g, '\\"');
+  const segments: string[] = [];
+  for (let i = 0; i < escaped.length; i += TXT_MAX_SEGMENT_LENGTH) {
+    segments.push(escaped.slice(i, i + TXT_MAX_SEGMENT_LENGTH));
+  }
+  if (segments.length === 0) segments.push('');
+  return segments.map((segment) => `"${segment}"`).join(' ');
+}
+
+function formatResourceRecordValue(type: string, value: string): string {
+  return type === 'TXT' ? formatTxtValue(value) : value;
+}
+
 const RETRYABLE_ERROR_NAMES = new Set([
   'ThrottlingException',
   'Throttling',
@@ -69,7 +94,9 @@ export function buildChangeBatch(
     Name: recordSet.name,
     Type: type as ResourceRecordSet['Type'],
     TTL: recordSet.ttl,
-    ResourceRecords: recordSet.resourceRecords.map((r) => ({ Value: r.value })),
+    ResourceRecords: recordSet.resourceRecords.map((r) => ({
+      Value: formatResourceRecordValue(type, r.value),
+    })),
   };
 
   if (recordSet.setIdentifier !== null && recordSet.setIdentifier !== undefined) {