diff --git a/components/content_settings/core/common/host_indexed_content_settings_unittest.cc b/components/content_settings/core/common/host_indexed_content_settings_unittest.cc
index 7ddfd8f5f9952..0fb29d15509c7 100644
--- a/components/content_settings/core/common/host_indexed_content_settings_unittest.cc
+++ b/components/content_settings/core/common/host_indexed_content_settings_unittest.cc
@@ -297,6 +297,40 @@ TEST_F(HostIndexedContentSettingsTest, CheckIPAddressesMatchIsBlock) {
   EXPECT_THAT(ToVector(index), testing::ContainerEq(test_settings));
 }
 
+// POC: When the primary URL is an IP literal and the rule is indexed by its
+// secondary host (because primary pattern is a full wildcard), the
+// subdomain-walk is wrongly skipped because FindInHostToContentSettings()
+// keys the IP-vs-hostname decision on primary_url instead of the host being
+// looked up. The indexed lookup therefore diverges from the linear-scan
+// reference semantics (ContentSettingsPattern::Matches).
+TEST_F(HostIndexedContentSettingsTest,
+       POC_IPPrimaryWithSecondaryDomainWildcardSubdomain) {
+  ContentSettingsForOneType settings = {
+      CreateSetting("*", "[*.]toplevel.com", CONTENT_SETTING_BLOCK)};
+  HostIndexedContentSettings index = FromVector(settings);
+
+  GURL ip_primary("http://192.168.1.2/");
+  GURL sub_secondary("http://sub.toplevel.com/");
+  GURL exact_secondary("http://toplevel.com/");
+
+  // Reference semantics: both patterns match.
+  ContentSettingsPattern primary_pat = ContentSettingsPattern::FromString("*");
+  ContentSettingsPattern secondary_pat =
+      ContentSettingsPattern::FromString("[*.]toplevel.com");
+  ASSERT_TRUE(primary_pat.Matches(ip_primary));
+  ASSERT_TRUE(secondary_pat.Matches(sub_secondary));
+
+  // Exact-host secondary is found even with IP primary (direct lookup).
+  EXPECT_NE(index.Find(ip_primary, exact_secondary), nullptr)
+      << "control: exact secondary host should be found";
+
+  // BUG: strict-subdomain secondary is NOT found when primary is an IP,
+  // because primary_url.HostIsIPAddress() suppresses the subdomain walk
+  // even though the host being walked is secondary_url.host().
+  EXPECT_NE(index.Find(ip_primary, sub_secondary), nullptr)
+      << "indexed lookup diverges from linear Matches() semantics";
+}
+
 TEST_F(HostIndexedContentSettingsTest, CheckIPAddressesNoMatch) {
   GURL test_primary_url("http://192.168.1.2/");
   GURL test_secondary_url("http://toplevel.com");