From b565c37277697cd55825c559956e4588a925a76d Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sun, 14 Jun 2026 15:59:32 +0000
Subject: [PATCH] fix: parse IPv6-literal URLs in post content

UrlParser.parseValidUrls filtered every detected URL through
isValidTopLevelDomain(), which requires the TLD's first character to be
an ASCII letter. IPv6 literal hosts are bracketed (e.g. [2001:db8::1])
and have no dotted TLD, so the whole bracketed host became the candidate
"TLD", starting with '[' and failing the check. As a result, valid
IPv6 URLs like http://[302:68d0:f0d5:b88d::bdb]/<hash> were dropped and
rendered as plain text instead of links.

The UrlDetector already validates the bracketed address as syntactically
correct IPv6, so accept bracketed hosts directly in isValidTopLevelDomain.
---
 .../amethyst/commons/richtext/UrlParser.kt    |  5 +++++
 .../commons/richtext/UrlParserTest.kt         | 21 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParser.kt b/commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParser.kt
index 6356b2e372..04078271c9 100644
--- a/commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParser.kt
+++ b/commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParser.kt
@@ -47,6 +47,11 @@ class UrlParser {
     fun Char.isAsciiLetter(): Boolean = (this in 'a'..'z' || this in 'A'..'Z')
 
     fun Url.isValidTopLevelDomain(): Boolean {
+        // IPv6 literal hosts are bracketed (e.g. [2001:db8::1]) and have no dotted TLD, so the
+        // letter-first TLD rule below would wrongly reject them. The detector already validated
+        // the bracketed address as a syntactically correct IPv6 literal, so accept it directly.
+        if (host.startsWith('[')) return true
+
         /*
         According to the TLD Applicant Guidebook published June 2012, ICANN does not allow numbers in TLDs.
          */
diff --git a/commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParserTest.kt b/commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParserTest.kt
index 600c0f27f0..7ce6c472d3 100644
--- a/commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParserTest.kt
+++ b/commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/richtext/UrlParserTest.kt
@@ -300,6 +300,27 @@ class UrlParserTest {
             Urls(withScheme = emptySet()),
         )
 
+    @Test
+    fun testIPv6UrlWithScheme() =
+        test(
+            "http://[302:68d0:f0d5:b88d::bdb]/08e31992c51b06d8f8ee4e40207ede11d4c69b0db2d268fb2783d45d69094c2b",
+            Urls(withScheme = setOf("http://[302:68d0:f0d5:b88d::bdb]/08e31992c51b06d8f8ee4e40207ede11d4c69b0db2d268fb2783d45d69094c2b")),
+        )
+
+    @Test
+    fun testIPv6UrlWithPort() =
+        test(
+            "http://[2001:db8::1]:8080/path",
+            Urls(withScheme = setOf("http://[2001:db8::1]:8080/path")),
+        )
+
+    @Test
+    fun testIPv6UrlInSentence() =
+        test(
+            "check this http://[2a01:5cc0:1:2::4] out",
+            Urls(withScheme = setOf("http://[2a01:5cc0:1:2::4]")),
+        )
+
     @Test
     fun testBlossom() {
         val blossom = "blossom:b1674191a88ec5cdd733e4240a81803105dc412d6c6708d53ab94fc248f4f553.pdf?xs=cdn.satellite.earth"