Code review:

- reject ill-formed localpart dots and IP literals in parse
- avoid Pair allocation in Nip05Id.parse

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip05DnsIdentifiers/Nip05Id.kt

@@ -47,8 +47,9 @@ data class Nip05Id(
     fun toDomainUrl(): String = domainUrl(domain)
 
     companion object {
-        // NIP-05 localpart: a-z, 0-9, -, _, .
+        // NIP-05 localpart: dot-separated atoms of [a-z0-9_-]. Forbids leading,
-        private val LOCAL_PART_REGEX = Regex("^[a-z0-9._-]+$")
+        // trailing, and consecutive dots (NIP-05 + RFC 5321 local-part rules).
+        private val LOCAL_PART_REGEX = Regex("^[a-z0-9_-]+(\\.[a-z0-9_-]+)*$")
 
         // Hostname: dot-separated labels of [a-z0-9-], no leading/trailing hyphen,
         // require at least one dot so single-label garbage (e.g. "s!ayer") is rejected.
@@ -58,9 +59,13 @@ data class Nip05Id(
         fun parse(nip05address: String): Nip05Id? {
             val parts = nip05address.trim().lowercase().split("@")
             if (parts.size != 2) return null
-            val (name, domain) = parts[0] to parts[1]
+            val name = parts[0]
+            val domain = parts[1]
             if (!LOCAL_PART_REGEX.matches(name)) return null
             if (!DOMAIN_REGEX.matches(domain)) return null
+            // Reject IP literals — NIP-05 expects a hostname, and a digits-only
+            // TLD is the cheapest way to tell them apart from real domains.
+            if (domain.substringAfterLast('.').all { it.isDigit() }) return null
             return Nip05Id(name, domain)
         }
 

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip05DnsIdentifiers/Nip05Test.kt

@@ -133,6 +133,27 @@ class Nip05Test {
         assertNull(Nip05Id.parse("alice@example-.com"))
     }
 
+    @Test
+    fun `parse rejects localpart with leading trailing or consecutive dots`() {
+        assertNull(Nip05Id.parse(".alice@example.com"))
+        assertNull(Nip05Id.parse("alice.@example.com"))
+        assertNull(Nip05Id.parse("alice..bob@example.com"))
+    }
+
+    @Test
+    fun `parse rejects IPv4 literal as domain`() {
+        assertNull(Nip05Id.parse("alice@192.168.1.1"))
+        assertNull(Nip05Id.parse("alice@8.8.8.8"))
+    }
+
+    @Test
+    fun `parse accepts wildcard underscore localpart`() {
+        val nip05 = Nip05Id.parse("_@example.com")
+        assertNotNull(nip05)
+        assertEquals("_", nip05.name)
+        assertEquals("example.com", nip05.domain)
+    }
+
     @Test
     fun `execute assemble url with valid value returns nip05 url`() {
         // given