diff --git a/modules/audit/pages/audit/system-audit/filter-schema.php b/modules/audit/pages/audit/system-audit/filter-schema.php
index 7d8bfe8..416bda1 100644
--- a/modules/audit/pages/audit/system-audit/filter-schema.php
+++ b/modules/audit/pages/audit/system-audit/filter-schema.php
@@ -46,6 +46,14 @@ return gridFilterSchema([
         'dir' => ['type' => 'dir', 'default' => 'desc'],
     ],
     'toolbar' => [
+        [
+            // Dormant capability — kept in toolbar as hidden so Grid.js preserves
+            // the param across refetches if/when a UI is added.
+            'key' => 'target_type',
+            'type' => 'hidden',
+            'input_id' => 'system-audit-target-type-filter',
+            'default' => '',
+        ],
         [
             'key' => 'search',
             'type' => 'text',
diff --git a/tests/Architecture/FilterSchemaConsistencyTest.php b/tests/Architecture/FilterSchemaConsistencyTest.php
new file mode 100644
index 0000000..cfc8268
--- /dev/null
+++ b/tests/Architecture/FilterSchemaConsistencyTest.php
@@ -0,0 +1,110 @@
+<?php
+
+namespace MintyPHP\Tests\Architecture;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Every query key declared in a list's `filter-schema.php` must also appear
+ * in the `toolbar` section (either as a visible field or hidden). Reason:
+ *
+ * - Backend reads filter values via `gridParseFiltersFromSchemaFile()`, which
+ *   parses against the `query` schema.
+ * - Frontend's Grid.js URL-sync only forwards params that are declared in the
+ *   `toolbar` section (derived via `gridSchemaClientFilters()`). If a query
+ *   param is not in `toolbar`, Grid.js drops it on every subsequent request
+ *   (pagination, sort, filter change) — the filter appears to work on page
+ *   load but silently breaks after any user interaction.
+ *
+ * This test ran us into real production pain before it existed: the address
+ * book's tenant-register tabs worked on first load but lost the filter on
+ * every grid refetch. Declaring `tenant` as a hidden toolbar field fixed it.
+ * This test prevents repeat occurrences.
+ *
+ * Exempted keys (framework-provided, always preserved by Grid.js):
+ *   limit, offset, order, dir
+ */
+class FilterSchemaConsistencyTest extends TestCase
+{
+    use ProjectFileAssertionSupport;
+
+    private const FRAMEWORK_KEYS = ['limit', 'offset', 'order', 'dir'];
+
+    public function testEveryQueryKeyHasToolbarDeclaration(): void
+    {
+        $root = $this->projectRootPath();
+        $schemaFiles = [];
+        $this->collectFilterSchemas($root . '/pages', $schemaFiles);
+        $this->collectFilterSchemas($root . '/modules', $schemaFiles);
+
+        $this->assertNotEmpty($schemaFiles, 'No filter-schema.php files found — regex stale?');
+
+        $violations = [];
+
+        foreach ($schemaFiles as $schemaFile) {
+            $schema = @include $schemaFile;
+            if (!is_array($schema)) {
+                $violations[] = sprintf('%s — filter-schema.php did not return an array', $this->relative($schemaFile, $root));
+                continue;
+            }
+
+            $queryKeys = array_keys(is_array($schema['query'] ?? null) ? $schema['query'] : []);
+            $toolbarFields = is_array($schema['toolbar'] ?? null) ? $schema['toolbar'] : [];
+
+            // Schemas without a toolbar are for non-Grid endpoints (e.g. global
+            // search data endpoint consumed by a custom JS dialog). Skip those —
+            // they never participate in Grid.js URL sync.
+            if ($toolbarFields === []) {
+                continue;
+            }
+
+            $toolbarKeys = [];
+            foreach ($toolbarFields as $field) {
+                if (!is_array($field)) {
+                    continue;
+                }
+                $key = trim((string) ($field['key'] ?? ''));
+                if ($key !== '') {
+                    $toolbarKeys[] = $key;
+                }
+            }
+
+            $missing = array_diff($queryKeys, $toolbarKeys, self::FRAMEWORK_KEYS);
+            if ($missing) {
+                $violations[] = sprintf(
+                    "%s — query keys missing from toolbar: %s.\n  Add them to the 'toolbar' section (type 'hidden' is fine) so Grid.js forwards them on refetch.",
+                    $this->relative($schemaFile, $root),
+                    implode(', ', $missing)
+                );
+            }
+        }
+
+        $this->assertSame(
+            [],
+            $violations,
+            "Filter-schema consistency violations:\n" . implode("\n\n", $violations)
+        );
+    }
+
+    /**
+     * @param list<string> &$out
+     */
+    private function collectFilterSchemas(string $base, array &$out): void
+    {
+        if (!is_dir($base)) {
+            return;
+        }
+        $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($base, \FilesystemIterator::SKIP_DOTS));
+        /** @var \SplFileInfo $file */
+        foreach ($iterator as $file) {
+            if ($file->isFile() && $file->getFilename() === 'filter-schema.php') {
+                $out[] = $file->getPathname();
+            }
+        }
+    }
+
+    private function relative(string $path, string $root): string
+    {
+        return str_replace($root . '/', '', $path);
+    }
+}
diff --git a/tests/Architecture/PageTemplateNamingTest.php b/tests/Architecture/PageTemplateNamingTest.php
new file mode 100644
index 0000000..3c15e79
--- /dev/null
+++ b/tests/Architecture/PageTemplateNamingTest.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace MintyPHP\Tests\Architecture;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * MintyPHP's Router parses page filenames by splitting on parentheses. URL
+ * parameters belong ONLY in the `.php` action filename (e.g. `view($id).php`);
+ * the `.phtml` view filename must contain exactly ONE paren group for the
+ * template name (`view(default).phtml` or `view(none).phtml`).
+ *
+ * Nested paren groups like `view($id)(none).phtml` cause the router's regex
+ * split to produce an empty view name — the file silently resolves to the
+ * wrong path and the response is an empty body with no visible error.
+ *
+ * Reference: vendor/mintyphp/core/src/Router.php::extractParts()
+ */
+class PageTemplateNamingTest extends TestCase
+{
+    use ProjectFileAssertionSupport;
+
+    public function testPhtmlFilenamesHaveExactlyOneParenGroup(): void
+    {
+        $root = $this->projectRootPath();
+        $scanRoots = [$root . '/pages'];
+        $modulesDir = $root . '/modules';
+        if (is_dir($modulesDir)) {
+            foreach (scandir($modulesDir) ?: [] as $moduleEntry) {
+                if ($moduleEntry === '.' || $moduleEntry === '..') {
+                    continue;
+                }
+                $modulePages = $modulesDir . '/' . $moduleEntry . '/pages';
+                if (is_dir($modulePages)) {
+                    $scanRoots[] = $modulePages;
+                }
+            }
+        }
+
+        $violations = [];
+
+        foreach ($scanRoots as $scanRoot) {
+            if (!is_dir($scanRoot)) {
+                continue;
+            }
+            $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($scanRoot, \FilesystemIterator::SKIP_DOTS));
+            /** @var \SplFileInfo $file */
+            foreach ($iterator as $file) {
+                if (!$file->isFile() || $file->getExtension() !== 'phtml') {
+                    continue;
+                }
+                $name = $file->getFilename();
+                $openCount = substr_count($name, '(');
+                $closeCount = substr_count($name, ')');
+                $relativePath = str_replace($root . '/', '', $file->getPathname());
+
+                if ($openCount !== $closeCount) {
+                    $violations[] = sprintf('%s — mismatched parens', $relativePath);
+                    continue;
+                }
+
+                // Partials (`_form.phtml`, shared includes) have zero paren groups — skip them.
+                if ($openCount === 0) {
+                    continue;
+                }
+
+                // Routed views must have exactly one paren group: `<view>(<template>).phtml`.
+                if ($openCount !== 1) {
+                    $violations[] = sprintf(
+                        '%s — found %d paren groups, expected exactly 1 (template only). '
+                        . 'URL parameters belong in the .php action filename, not the .phtml view. '
+                        . "Nested paren groups break MintyPHP's Router silently (empty response).",
+                        $relativePath,
+                        $openCount
+                    );
+                }
+            }
+        }
+
+        $this->assertSame(
+            [],
+            $violations,
+            ".phtml filename convention violations:\n" . implode("\n", $violations)
+        );
+    }
+}