Search display name overrides in user fuzzy search

app/models/concerns/user_fuzzy_search.rb

@@ -18,6 +18,7 @@ def fuzzy_ranked_search(term, limit: 20)
       candidate_parts = [
         "SELECT id FROM users WHERE slack_uid = :exact",
         "SELECT id FROM users WHERE username ILIKE :contains",
+        "SELECT id FROM users WHERE display_name_override ILIKE :contains",
         "SELECT id FROM users WHERE github_username ILIKE :contains",
         "SELECT id FROM users WHERE slack_username ILIKE :contains",
         "SELECT user_id AS id FROM email_addresses WHERE email ILIKE :contains"
@@ -33,6 +34,10 @@ def fuzzy_ranked_search(term, limit: 20)
              WHEN users.username ILIKE :prefix THEN 50
              WHEN users.username ILIKE :contains THEN 10
              ELSE 0 END +
+        CASE WHEN users.display_name_override ILIKE :ilike_exact THEN 100
+             WHEN users.display_name_override ILIKE :prefix THEN 50
+             WHEN users.display_name_override ILIKE :contains THEN 10
+             ELSE 0 END +
         CASE WHEN users.github_username ILIKE :ilike_exact THEN 100
              WHEN users.github_username ILIKE :prefix THEN 50
              WHEN users.github_username ILIKE :contains THEN 10

db/migrate/20260804184518_add_trgm_index_to_users_display_name_override.rb

@@ -0,0 +1,21 @@
+class AddTrgmIndexToUsersDisplayNameOverride < ActiveRecord::Migration[8.1]
+  disable_ddl_transaction!
+
+  def up
+    enable_extension :pg_trgm unless extension_enabled?(:pg_trgm)
+
+    add_index :users, :display_name_override,
+              name: :index_users_on_display_name_override_trgm,
+              using: :gin,
+              opclass: :gin_trgm_ops,
+              algorithm: :concurrently,
+              if_not_exists: true
+  end
+
+  def down
+    remove_index :users, :display_name_override,
+                 name: :index_users_on_display_name_override_trgm,
+                 algorithm: :concurrently,
+                 if_exists: true
+  end
+end

test/models/concerns/user_fuzzy_search_test.rb

@@ -13,6 +13,7 @@
 #   - rank scoring tiers (id/slack_uid exact = 1000; field exact = 100;
 #     prefix = 50; contains = 10; tiers compound additively)
 #   - case-insensitive ILIKE on username/email fields
+#   - display name overrides are searchable and ranked like other name fields
 #   - case-sensitive equality on slack_uid
 #   - matched_email picks best email (exact > prefix > contains > any)
 #   - matched_email is nil only when the user has zero emails
@@ -114,6 +115,16 @@ def with_email(user, email)
     assert User.fuzzy_ranked_search("MIXEDCASEUSER").any? { |r| r.id == u.id }
   end
 
+  test "display name override is searchable and ranked case-insensitively" do
+    u = create_user(username: "unrelated_username", display_name_override: "Custom Display Name")
+
+    exact = User.fuzzy_ranked_search("custom display name").find { |r| r.id == u.id }
+    substring = User.fuzzy_ranked_search("DISPLAY").find { |r| r.id == u.id }
+
+    assert_operator exact.rank_score, :>=, 100
+    assert_operator substring.rank_score, :>=, 10
+  end
+
   # ----- multi-field tiers -----
 
   test "github_username, slack_username, and email tiers contribute" do