From 4a6d17ad7bfea59d451b64b90eb794055c965557 Mon Sep 17 00:00:00 2001
From: Claire <claire.github-309c@sitedethib.com>
Date: Tue, 17 Feb 2026 11:27:36 +0100
Subject: [PATCH] Fix hashtag matching by replacing negative lookbehind with
 positive lookbehind (#37684)

---
 app/models/tag.rb       | 2 +-
 spec/models/tag_spec.rb | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/app/models/tag.rb b/app/models/tag.rb
index 9924d132e6..9c4e0510a9 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -41,7 +41,7 @@ class Tag < ApplicationRecord
   HASHTAG_LAST_SEQUENCE = '([[:word:]_]*[[:alpha:]][[:word:]_]*)'
   HASHTAG_NAME_PAT = "#{HASHTAG_FIRST_SEQUENCE}|#{HASHTAG_LAST_SEQUENCE}".freeze
 
-  HASHTAG_RE = %r{(?<![=/)\p{Alnum}])[#＃](#{HASHTAG_NAME_PAT})}
+  HASHTAG_RE = /(?<=^|\s)[#＃](#{HASHTAG_NAME_PAT})/
   HASHTAG_NAME_RE = /\A(#{HASHTAG_NAME_PAT})\z/i
   HASHTAG_INVALID_CHARS_RE = /[^[:alnum:]\u0E47-\u0E4E#{HASHTAG_SEPARATORS}]/
 
diff --git a/spec/models/tag_spec.rb b/spec/models/tag_spec.rb
index 79f8edf79a..a6406a69a7 100644
--- a/spec/models/tag_spec.rb
+++ b/spec/models/tag_spec.rb
@@ -85,6 +85,10 @@ RSpec.describe Tag do
       expect(subject.match('https://en.wikipedia.org/wiki/Ghostbusters_(song)?foo=#Lawsuit')).to be_nil
     end
 
+    it 'does not match URLs with hashtag-like anchors after a dot' do
+      expect(subject.match('https://en.wikipedia.org/wiki/Google_LLC_v._Oracle_America,_Inc.#Decision')).to be_nil
+    end
+
     it 'matches #ａｅｓｔｈｅｔｉｃ' do
       expect(subject.match('this is #ａｅｓｔｈｅｔｉｃ').to_s).to eq '#ａｅｓｔｈｅｔｉｃ'
     end