diff --git a/src/apm_cli/commands/install.py b/src/apm_cli/commands/install.py
index 71786f5e..e7a0ca73 100644
--- a/src/apm_cli/commands/install.py
+++ b/src/apm_cli/commands/install.py
@@ -247,8 +247,21 @@ def _validate_package_exists(package, verbose=False):
 
         # For virtual packages, use the downloader's validation method
         if dep_ref.is_virtual:
-            downloader = GitHubPackageDownloader()
-            return downloader.validate_virtual_package_exists(dep_ref)
+            ctx = auth_resolver.resolve_for_dep(dep_ref)
+            host = dep_ref.host or default_host()
+            org = dep_ref.repo_url.split('/')[0] if dep_ref.repo_url and '/' in dep_ref.repo_url else None
+            if verbose_log:
+                verbose_log(f"Auth resolved: host={host}, org={org}, source={ctx.source}, type={ctx.token_type}")
+            downloader = GitHubPackageDownloader(auth_resolver=auth_resolver)
+            result = downloader.validate_virtual_package_exists(dep_ref)
+            if not result and verbose_log:
+                try:
+                    err_ctx = auth_resolver.build_error_context(host, f"accessing {package}", org=org)
+                    for line in err_ctx.splitlines():
+                        verbose_log(line)
+                except Exception:
+                    pass
+            return result
 
         # For Azure DevOps or GitHub Enterprise (non-github.com hosts),
         # use the downloader which handles authentication properly
diff --git a/tests/unit/test_install_command.py b/tests/unit/test_install_command.py
index 4d65946e..e5cb15d5 100644
--- a/tests/unit/test_install_command.py
+++ b/tests/unit/test_install_command.py
@@ -314,6 +314,47 @@ def test_verbose_validation_failure_calls_build_error_context(self, mock_urlopen
             assert call_args[0][0] == "github.com"  # host
             assert call_args[0][1].endswith("owner/repo")  # operation
 
+    def test_verbose_virtual_package_validation_shows_auth_diagnostics(self):
+        """When virtual package validation fails in verbose mode, auth diagnostics are shown."""
+        from apm_cli.commands.install import _validate_package_exists
+
+        with patch(
+            "apm_cli.deps.github_downloader.GitHubPackageDownloader.validate_virtual_package_exists",
+            return_value=False,
+        ), patch.object(
+            __import__("apm_cli.core.auth", fromlist=["AuthResolver"]).AuthResolver,
+            "resolve_for_dep",
+            return_value=MagicMock(source="none", token_type="none", token=None),
+        ) as mock_resolve, patch.object(
+            __import__("apm_cli.core.auth", fromlist=["AuthResolver"]).AuthResolver,
+            "build_error_context",
+            return_value="Authentication failed for accessing owner/repo/skills/my-skill on github.com.\nNo token available.",
+        ) as mock_build_ctx:
+            result = _validate_package_exists("owner/repo/skills/my-skill", verbose=True)
+            assert result is False
+            mock_resolve.assert_called_once()
+            mock_build_ctx.assert_called_once()
+            call_args = mock_build_ctx.call_args
+            assert call_args[0][0] == "github.com"  # host
+            assert "owner/repo/skills/my-skill" in call_args[0][1]  # operation
+
+    def test_virtual_package_validation_reuses_auth_resolver(self):
+        """Virtual package validation should pass its AuthResolver to the downloader."""
+        from apm_cli.commands.install import _validate_package_exists
+
+        with patch(
+            "apm_cli.deps.github_downloader.GitHubPackageDownloader.__init__",
+            return_value=None,
+        ) as mock_init, patch(
+            "apm_cli.deps.github_downloader.GitHubPackageDownloader.validate_virtual_package_exists",
+            return_value=True,
+        ):
+            _validate_package_exists("owner/repo/skills/my-skill", verbose=False)
+            mock_init.assert_called_once()
+            # The auth_resolver kwarg should be passed (not creating a new one)
+            _, kwargs = mock_init.call_args
+            assert "auth_resolver" in kwargs
+
 
 # ---------------------------------------------------------------------------
 # Transitive dep parent chain breadcrumb