diff --git a/.gitignore b/.gitignore
index 46daf3d31..48b8bf907 100755
--- a/.gitignore
+++ b/.gitignore
@@ -1,14 +1 @@
-/vendor/
-/.idea/
-.DS_Store
-mock.json
-data-tests.php
-loader.php
-.phpunit.result.cache
-.vscode
-.vscode/*
-database.sql
-Makefile
-.envrc
-.vscode
-tmp
+vendor/
diff --git a/src/Database/Adapter/Mongo.php b/src/Database/Adapter/Mongo.php
index c8f45b7e8..ce399f5de 100644
--- a/src/Database/Adapter/Mongo.php
+++ b/src/Database/Adapter/Mongo.php
@@ -786,55 +786,60 @@ public function updateRelationship(
         ?string $newKey = null,
         ?string $newTwoWayKey = null
     ): bool {
-        $collection = $this->getNamespace() . '_' . $this->filter($collection);
-        $relatedCollection = $this->getNamespace() . '_' . $this->filter($relatedCollection);
+        $collectionName = $this->getNamespace() . '_' . $this->filter($collection);
+        $relatedCollectionName = $this->getNamespace() . '_' . $this->filter($relatedCollection);
+
+        $escapedKey = $this->escapeMongoFieldName($key);
+        $escapedNewKey = !\is_null($newKey) ? $this->escapeMongoFieldName($newKey) : null;
+        $escapedTwoWayKey = $this->escapeMongoFieldName($twoWayKey);
+        $escapedNewTwoWayKey = !\is_null($newTwoWayKey) ? $this->escapeMongoFieldName($newTwoWayKey) : null;
 
         $renameKey = [
             '$rename' => [
-                $key => $newKey,
+                $escapedKey => $escapedNewKey,
             ]
         ];
 
         $renameTwoWayKey = [
             '$rename' => [
-                $twoWayKey => $newTwoWayKey,
+                $escapedTwoWayKey => $escapedNewTwoWayKey,
             ]
         ];
 
         switch ($type) {
             case Database::RELATION_ONE_TO_ONE:
-                if (!\is_null($newKey)) {
-                    $this->getClient()->update($collection, updates: $renameKey, multi: true);
+                if (!\is_null($newKey) && $key !== $newKey) {
+                    $this->getClient()->update($collectionName, updates: $renameKey, multi: true);
                 }
-                if ($twoWay && !\is_null($newTwoWayKey)) {
-                    $this->getClient()->update($relatedCollection, updates: $renameTwoWayKey, multi: true);
+                if ($twoWay && !\is_null($newTwoWayKey) && $twoWayKey !== $newTwoWayKey) {
+                    $this->getClient()->update($relatedCollectionName, updates: $renameTwoWayKey, multi: true);
                 }
                 break;
             case Database::RELATION_ONE_TO_MANY:
-                if ($twoWay && !\is_null($newTwoWayKey)) {
-                    $this->getClient()->update($relatedCollection, updates: $renameTwoWayKey, multi: true);
+                if ($twoWay && !\is_null($newTwoWayKey) && $twoWayKey !== $newTwoWayKey) {
+                    $this->getClient()->update($relatedCollectionName, updates: $renameTwoWayKey, multi: true);
                 }
                 break;
             case Database::RELATION_MANY_TO_ONE:
-                if (!\is_null($newKey)) {
-                    $this->getClient()->update($collection, updates: $renameKey, multi: true);
+                if (!\is_null($newKey) && $key !== $newKey) {
+                    $this->getClient()->update($collectionName, updates: $renameKey, multi: true);
                 }
                 break;
             case Database::RELATION_MANY_TO_MANY:
                 $metadataCollection = new Document(['$id' => Database::METADATA]);
-                $collection = $this->getDocument($metadataCollection, $collection);
-                $relatedCollection = $this->getDocument($metadataCollection, $relatedCollection);
+                $collectionDoc = $this->getDocument($metadataCollection, $collection);
+                $relatedCollectionDoc = $this->getDocument($metadataCollection, $relatedCollection);
 
-                if ($collection->isEmpty() || $relatedCollection->isEmpty()) {
+                if ($collectionDoc->isEmpty() || $relatedCollectionDoc->isEmpty()) {
                     throw new DatabaseException('Collection or related collection not found');
                 }
 
-                $junction = $this->getNamespace() . '_' . $this->filter('_' . $collection->getSequence() . '_' . $relatedCollection->getSequence());
+                $junction = $this->getNamespace() . '_' . $this->filter('_' . $collectionDoc->getSequence() . '_' . $relatedCollectionDoc->getSequence());
 
-                if (!\is_null($newKey)) {
+                if (!\is_null($newKey) && $key !== $newKey) {
                     $this->getClient()->update($junction, updates: $renameKey, multi: true);
                 }
-                if ($twoWay && !\is_null($newTwoWayKey)) {
+                if ($twoWay && !\is_null($newTwoWayKey) && $twoWayKey !== $newTwoWayKey) {
                     $this->getClient()->update($junction, updates: $renameTwoWayKey, multi: true);
                 }
                 break;
@@ -866,32 +871,52 @@ public function deleteRelationship(
         string $twoWayKey,
         string $side
     ): bool {
-        $junction = $this->getNamespace() . '_' . $this->filter('_' . $collection . '_' . $relatedCollection);
-        $collection = $this->getNamespace() . '_' . $this->filter($collection);
-        $relatedCollection = $this->getNamespace() . '_' . $this->filter($relatedCollection);
+        $collectionName = $this->getNamespace() . '_' . $this->filter($collection);
+        $relatedCollectionName = $this->getNamespace() . '_' . $this->filter($relatedCollection);
+        $escapedKey = $this->escapeMongoFieldName($key);
+        $escapedTwoWayKey = $this->escapeMongoFieldName($twoWayKey);
 
         switch ($type) {
             case Database::RELATION_ONE_TO_ONE:
-                $this->getClient()->update($collection, [], ['$unset' => [$key => '']], multi: true);
-                if ($twoWay) {
-                    $this->getClient()->update($relatedCollection, [], ['$unset' => [$twoWayKey => '']], multi: true);
+                if ($side === Database::RELATION_SIDE_PARENT) {
+                    $this->getClient()->update($collectionName, [], ['$unset' => [$escapedKey => '']], multi: true);
+                    if ($twoWay) {
+                        $this->getClient()->update($relatedCollectionName, [], ['$unset' => [$escapedTwoWayKey => '']], multi: true);
+                    }
+                } elseif ($side === Database::RELATION_SIDE_CHILD) {
+                    $this->getClient()->update($relatedCollectionName, [], ['$unset' => [$escapedTwoWayKey => '']], multi: true);
+                    if ($twoWay) {
+                        $this->getClient()->update($collectionName, [], ['$unset' => [$escapedKey => '']], multi: true);
+                    }
                 }
                 break;
             case Database::RELATION_ONE_TO_MANY:
                 if ($side === Database::RELATION_SIDE_PARENT) {
-                    $this->getClient()->update($collection, [], ['$unset' => [$key => '']], multi: true);
+                    $this->getClient()->update($relatedCollectionName, [], ['$unset' => [$escapedTwoWayKey => '']], multi: true);
                 } else {
-                    $this->getClient()->update($relatedCollection, [], ['$unset' => [$twoWayKey => '']], multi: true);
+                    $this->getClient()->update($collectionName, [], ['$unset' => [$escapedKey => '']], multi: true);
                 }
                 break;
             case Database::RELATION_MANY_TO_ONE:
-                if ($side === Database::RELATION_SIDE_CHILD) {
-                    $this->getClient()->update($collection, [], ['$unset' => [$key => '']], multi: true);
+                if ($side === Database::RELATION_SIDE_PARENT) {
+                    $this->getClient()->update($collectionName, [], ['$unset' => [$escapedKey => '']], multi: true);
                 } else {
-                    $this->getClient()->update($relatedCollection, [], ['$unset' => [$twoWayKey => '']], multi: true);
+                    $this->getClient()->update($relatedCollectionName, [], ['$unset' => [$escapedTwoWayKey => '']], multi: true);
                 }
                 break;
             case Database::RELATION_MANY_TO_MANY:
+                $metadataCollection = new Document(['$id' => Database::METADATA]);
+                $collectionDoc = $this->getDocument($metadataCollection, $collection);
+                $relatedCollectionDoc = $this->getDocument($metadataCollection, $relatedCollection);
+
+                if ($collectionDoc->isEmpty() || $relatedCollectionDoc->isEmpty()) {
+                    throw new DatabaseException('Collection or related collection not found');
+                }
+
+                $junction = $side === Database::RELATION_SIDE_PARENT
+                    ? $this->getNamespace() . '_' . $this->filter('_' . $collectionDoc->getSequence() . '_' . $relatedCollectionDoc->getSequence())
+                    : $this->getNamespace() . '_' . $this->filter('_' . $relatedCollectionDoc->getSequence() . '_' . $collectionDoc->getSequence());
+
                 $this->getClient()->dropCollection($junction);
                 break;
             default:
@@ -1073,7 +1098,7 @@ public function renameIndex(string $collection, string $old, string $new): bool
         $index = null;
 
         foreach ($indexes as $node) {
-            if ($node['key'] === $old) {
+            if (($node['$id'] ?? $node['key'] ?? '') === $old) {
                 $index = $node;
                 break;
             }
@@ -1097,13 +1122,16 @@ public function renameIndex(string $collection, string $old, string $new): bool
         }
 
         try {
+            if (!$index) {
+                throw new DatabaseException('Index not found: ' . $old);
+            }
             $deletedindex = $this->deleteIndex($collection, $old);
             $createdindex = $this->createIndex($collection, $new, $index['type'], $index['attributes'], $index['lengths'] ?? [], $index['orders'] ?? [], $indexAttributeTypes, [], $index['ttl'] ?? 0);
         } catch (\Exception $e) {
             throw $this->processException($e);
         }
 
-        if ($index && $deletedindex && $createdindex) {
+        if ($deletedindex && $createdindex) {
             return true;
         }
 
@@ -1152,8 +1180,9 @@ public function getDocument(Document $collection, string $id, array $queries = [
         $options = $this->getTransactionOptions();
 
         $selections = $this->getAttributeSelections($queries);
+        $hasProjection = !empty($selections) && !\in_array('*', $selections);
 
-        if (!empty($selections) && !\in_array('*', $selections)) {
+        if ($hasProjection) {
             $options['projection'] = $this->getAttributeProjection($selections);
         }
 
@@ -1172,6 +1201,11 @@ public function getDocument(Document $collection, string $id, array $queries = [
         $document = new Document($result);
         $document = $this->castingAfter($collection, $document);
 
+        // Ensure missing relationship attributes are set to null (MongoDB doesn't store null fields)
+        if (!$hasProjection) {
+            $this->ensureRelationshipDefaults($collection, $document);
+        }
+
         return $document;
     }
 
@@ -1972,6 +2006,10 @@ public function find(Document $collection, array $queries = [], ?int $limit = 25
         $name = $this->getNamespace() . '_' . $this->filter($collection->getId());
         $queries = array_map(fn ($query) => clone $query, $queries);
 
+        // Escape query attribute names that contain dots and match collection attributes
+        // (to distinguish from nested object paths like profile.level1.value)
+        $this->escapeQueryAttributes($collection, $queries);
+
         $filters = $this->buildFilters($queries);
 
         if ($this->sharedTables) {
@@ -1998,7 +2036,8 @@ public function find(Document $collection, array $queries = [], ?int $limit = 25
         }
 
         $selections = $this->getAttributeSelections($queries);
-        if (!empty($selections) && !\in_array('*', $selections)) {
+        $hasProjection = !empty($selections) && !\in_array('*', $selections);
+        if ($hasProjection) {
             $options['projection'] = $this->getAttributeProjection($selections);
         }
 
@@ -2127,6 +2166,13 @@ public function find(Document $collection, array $queries = [], ?int $limit = 25
             $found = array_reverse($found);
         }
 
+        // Ensure missing relationship attributes are set to null (MongoDB doesn't store null fields)
+        if (!$hasProjection) {
+            foreach ($found as $document) {
+                $this->ensureRelationshipDefaults($collection, $document);
+            }
+        }
+
         return $found;
     }
 
@@ -2210,6 +2256,9 @@ public function count(Document $collection, array $queries = [], ?int $max = nul
 
         $queries = array_map(fn ($query) => clone $query, $queries);
 
+        // Escape query attribute names that contain dots and match collection attributes
+        $this->escapeQueryAttributes($collection, $queries);
+
         $filters = [];
         $options = [];
 
@@ -2360,6 +2409,91 @@ protected function getClient(): Client
         return $this->client;
     }
 
+    /**
+     * Escape a field name for MongoDB storage.
+     * MongoDB field names cannot start with $ or contain dots.
+     *
+     * @param string $name
+     * @return string
+     */
+    protected function escapeMongoFieldName(string $name): string
+    {
+        if (\str_starts_with($name, '$')) {
+            $name = '_' . \substr($name, 1);
+        }
+        if (\str_contains($name, '.')) {
+            $name = \str_replace('.', '__dot__', $name);
+        }
+        return $name;
+    }
+
+    /**
+     * Escape query attribute names that contain dots and match known collection attributes.
+     * This distinguishes field names with dots (like 'collectionSecurity.Parent') from
+     * nested object paths (like 'profile.level1.value').
+     *
+     * @param Document $collection
+     * @param array<Query> $queries
+     */
+    protected function escapeQueryAttributes(Document $collection, array $queries): void
+    {
+        $attributes = $collection->getAttribute('attributes', []);
+        $dotAttributes = [];
+        foreach ($attributes as $attribute) {
+            $key = $attribute['$id'] ?? '';
+            if (\str_contains($key, '.') || \str_starts_with($key, '$')) {
+                $dotAttributes[$key] = $this->escapeMongoFieldName($key);
+            }
+        }
+
+        if (empty($dotAttributes)) {
+            return;
+        }
+
+        foreach ($queries as $query) {
+            $attr = $query->getAttribute();
+            if (isset($dotAttributes[$attr])) {
+                $query->setAttribute($dotAttributes[$attr]);
+            }
+        }
+    }
+
+    /**
+     * Ensure relationship attributes have default null values in MongoDB documents.
+     * MongoDB doesn't store null fields, so we need to add them for schema compatibility.
+     *
+     * @param Document $collection
+     * @param Document $document
+     */
+    protected function ensureRelationshipDefaults(Document $collection, Document $document): void
+    {
+        $attributes = $collection->getAttribute('attributes', []);
+        foreach ($attributes as $attribute) {
+            $key = $attribute['$id'] ?? '';
+            $type = $attribute['type'] ?? '';
+            if ($type === Database::VAR_RELATIONSHIP && !$document->offsetExists($key)) {
+                $options = $attribute['options'] ?? [];
+                $twoWay = $options['twoWay'] ?? false;
+                $side = $options['side'] ?? '';
+                $relationType = $options['relationType'] ?? '';
+
+                // Determine if this relationship stores data on this collection's documents
+                // Only set null defaults for relationships that would have a column in SQL
+                $storesData = match ($relationType) {
+                    Database::RELATION_ONE_TO_ONE => $side === Database::RELATION_SIDE_PARENT || $twoWay,
+                    Database::RELATION_ONE_TO_MANY => $side === Database::RELATION_SIDE_CHILD,
+                    Database::RELATION_MANY_TO_ONE => $side === Database::RELATION_SIDE_PARENT,
+                    Database::RELATION_MANY_TO_MANY => false,
+                    default => false,
+                };
+
+                if ($storesData) {
+                    $document->setAttribute($key, null);
+                }
+            }
+        }
+    }
+
     /**
      * Keys cannot begin with $ in MongoDB
      * Convert $ prefix to _ on $id, $permissions, and $collection
@@ -2385,13 +2519,26 @@ protected function replaceChars(string $from, string $to, array $array): array
                 $array[$k] = $this->replaceChars($from, $to, $v);
             }
 
+            $newKey = $k;
+
             // Handle key replacement for filtered attributes
             $clean_key = str_replace($from, "", $k);
             if (in_array($clean_key, $filter)) {
                 $newKey = str_replace($from, $to, $k);
-                if ($newKey !== $k) {
-                    $keysToRename[$k] = $newKey;
-                }
+            } elseif (\is_string($k) && \str_starts_with($k, $from) && !in_array($k, ['$id', '$sequence', '$tenant', '_uid', '_id', '_tenant'])) {
+                // Handle any other key starting with the 'from' char (e.g. user-defined $-prefixed keys)
+                $newKey = $to . \substr($k, \strlen($from));
+            }
+
+            // Handle dot escaping in MongoDB field names
+            if ($from === '$' && \is_string($k) && \str_contains($newKey, '.')) {
+                $newKey = \str_replace('.', '__dot__', $newKey);
+            } elseif ($from === '_' && \is_string($k) && \str_contains($k, '__dot__')) {
+                $newKey = \str_replace('__dot__', '.', $newKey);
+            }
+
+            if ($newKey !== $k) {
+                $keysToRename[$k] = $newKey;
             }
         }
 
@@ -2486,6 +2633,9 @@ protected function buildFilter(Query $query): array
             $query->setAttribute('_createdAt');
         } elseif ($query->getAttribute() === '$updatedAt') {
             $query->setAttribute('_updatedAt');
+        } elseif (\str_starts_with($query->getAttribute(), '$')) {
+            // Escape $ prefix and dots in user-defined $-prefixed attribute names for MongoDB
+            $query->setAttribute($this->escapeMongoFieldName($query->getAttribute()));
         }
 
         $attribute = $query->getAttribute();
@@ -2700,13 +2850,11 @@ protected function getQueryValue(string $method, mixed $value): mixed
         switch ($method) {
             case Query::TYPE_STARTS_WITH:
                 $value = preg_quote($value, '/');
-                $value = str_replace(['\\', '$'], ['\\\\', '\\$'], $value);
                 return $value . '.*';
             case Query::TYPE_NOT_STARTS_WITH:
                 return $value;
             case Query::TYPE_ENDS_WITH:
                 $value = preg_quote($value, '/');
-                $value = str_replace(['\\', '$'], ['\\\\', '\\$'], $value);
                 return '.*' . $value;
             case Query::TYPE_NOT_ENDS_WITH:
                 return $value;
@@ -2956,7 +3104,7 @@ public function getSupportForTimeouts(): bool
 
     public function getSupportForRelationships(): bool
     {
-        return false;
+        return true;
     }
 
     public function getSupportForUpdateLock(): bool
diff --git a/tests/e2e/Adapter/Scopes/RelationshipTests.php b/tests/e2e/Adapter/Scopes/RelationshipTests.php
index be4b74a6f..1d23e3f2c 100644
--- a/tests/e2e/Adapter/Scopes/RelationshipTests.php
+++ b/tests/e2e/Adapter/Scopes/RelationshipTests.php
@@ -1104,6 +1104,12 @@ public function testStructureValidationAfterRelationsAttribute(): void
             return;
         }
 
+        if (!$database->getAdapter()->getSupportForAttributes()) {
+            // Schemaless mode allows unknown attributes, so structure validation won't reject them
+            $this->expectNotToPerformAssertions();
+            return;
+        }
+
         $database->createCollection("structure_1", [], [], [Permission::create(Role::any())]);
         $database->createCollection("structure_2", [], [], [Permission::create(Role::any())]);