diff --git a/application/Espo/ORM/BaseEntity.php b/application/Espo/ORM/BaseEntity.php
index c0f538b1d8..ba637e3030 100644
--- a/application/Espo/ORM/BaseEntity.php
+++ b/application/Espo/ORM/BaseEntity.php
@@ -31,6 +31,7 @@ namespace Espo\ORM;
 
 use Espo\ORM\Relation\EmptyRelations;
 use Espo\ORM\Relation\Relations;
+use Espo\ORM\Type\AttributeType;
 use Espo\ORM\Type\RelationType;
 use Espo\ORM\Value\ValueAccessorFactory;
 use Espo\ORM\Value\ValueAccessor;
@@ -139,6 +140,8 @@ class BaseEntity implements Entity
     public function reset(): void
     {
         $this->valuesContainer = [];
+
+        $this->relations->resetAll();
     }
 
     /**
@@ -458,6 +461,29 @@ class BaseEntity implements Entity
         }
 
         $this->setInContainer($attribute, $preparedValue);
+
+        $type = $this->getAttributeType($attribute);
+
+        if (
+            $type === AttributeType::FOREIGN_ID ||
+            $type === AttributeType::FOREIGN &&
+            $this->isAttributeHasOneForeignId($attribute)
+            // @todo Move the logic for hasOne to Espo\Core\ORM\Entity ?
+        ) {
+            $this->relations->reset(substr($attribute, 0, -2));
+        } else if ($type === AttributeType::FOREIGN_TYPE) {
+            $this->relations->reset(substr($attribute, 0, -4));
+        }
+    }
+
+    private function isAttributeHasOneForeignId(string $attribute): bool
+    {
+        $type = $this->getAttributeType($attribute);
+
+        return $type === AttributeType::FOREIGN &&
+            $this->getAttributeParam($attribute, 'relation') === substr($attribute, 0, -2) &&
+            $this->getAttributeParam($attribute, 'foreign') === 'id' &&
+            str_ends_with($attribute, 'Id');
     }
 
     protected function prepareAttributeValue(string $attribute, mixed $value): mixed
@@ -945,7 +971,7 @@ class BaseEntity implements Entity
     }
 
     /**
-     * Copy all current values to fetched values. All current attribute values will beset as those
+     * Copy all current values to fetched values. All current attribute values will be set as those
      * that are fetched from DB.
      */
     public function updateFetchedValues(): void
@@ -1117,12 +1143,13 @@ class BaseEntity implements Entity
                 continue;
             }
 
-            if ($attribute == 'id') {
+            if ($attribute === 'id') {
                 $this->id = $data[$attribute];
 
                 continue;
             }
 
+            // @todo Revise. To remove?
             if ($onlyAccessible && $this->getAttributeParam($attribute, 'notAccessible')) {
                 continue;
             }
diff --git a/application/Espo/ORM/EntityManager.php b/application/Espo/ORM/EntityManager.php
index ae2788e5d5..145c9fe2a4 100644
--- a/application/Espo/ORM/EntityManager.php
+++ b/application/Espo/ORM/EntityManager.php
@@ -281,7 +281,7 @@ class EntityManager
             throw new RuntimeException("Can't refresh a non-existent entity.");
         }
 
-        $this->relationsMap->get($entity)?->reset();
+        $this->relationsMap->get($entity)?->resetAll();
 
         $entity->set($fetchedEntity->getValueMap());
         $entity->setAsFetched();
diff --git a/application/Espo/ORM/Relation/EmptyRelations.php b/application/Espo/ORM/Relation/EmptyRelations.php
index 803f91355d..6b76e18278 100644
--- a/application/Espo/ORM/Relation/EmptyRelations.php
+++ b/application/Espo/ORM/Relation/EmptyRelations.php
@@ -31,17 +31,60 @@ namespace Espo\ORM\Relation;
 
 use Espo\ORM\Entity;
 use Espo\ORM\EntityCollection;
+use LogicException;
+use RuntimeException as RuntimeExceptionAlias;
 
 class EmptyRelations implements Relations
 {
+    /** @var array<string, Entity|EntityCollection<Entity>|null> */
+    private array $setData = [];
+
     public function __construct() {}
 
-    public function reset(): void
-    {}
+    public function resetAll(): void
+    {
+        $this->setData = [];
+    }
+
+    public function reset(string $relation): void
+    {
+        unset($this->setData[$relation]);
+    }
+
+    /**
+     * @param Entity|EntityCollection<Entity>|null $related
+     */
+    public function set(string $relation, Entity|EntityCollection|null $related): void
+    {
+        $this->setData[$relation] = $related;
+    }
+
+    public function isSet(string $relation): bool
+    {
+        return array_key_exists($relation, $this->setData);
+    }
+
+    /**
+     * @return Entity|EntityCollection<Entity>|null
+     */
+    public function getSet(string $relation): Entity|EntityCollection|null
+    {
+        if (!array_key_exists($relation, $this->setData)) {
+            throw new RuntimeExceptionAlias("Relation '$relation' is not set.");
+        }
+
+        return $this->setData[$relation];
+    }
 
     public function getOne(string $relation): ?Entity
     {
-        return null;
+        $entity = $this->setData[$relation] ?? null;
+
+        if ($entity instanceof EntityCollection) {
+            throw new LogicException("Not an entity.");
+        }
+
+        return $entity;
     }
 
     /***
@@ -49,7 +92,13 @@ class EmptyRelations implements Relations
      */
     public function getMany(string $relation): EntityCollection
     {
+        $collection = $this->setData[$relation] ?? new EntityCollection();
+
+        if (!$collection instanceof EntityCollection) {
+            throw new LogicException("Not a collection.");
+        }
+
         /** @var EntityCollection<Entity> */
-        return new EntityCollection();
+        return $collection;
     }
 }
diff --git a/application/Espo/ORM/Relation/RDBRelations.php b/application/Espo/ORM/Relation/RDBRelations.php
index 5a4d810f31..13dd0b23d8 100644
--- a/application/Espo/ORM/Relation/RDBRelations.php
+++ b/application/Espo/ORM/Relation/RDBRelations.php
@@ -29,23 +29,33 @@
 
 namespace Espo\ORM\Relation;
 
-use Espo\ORM\Collection;
 use Espo\ORM\Entity;
 use Espo\ORM\EntityCollection;
 use Espo\ORM\EntityManager;
 use Espo\ORM\Query\Part\Order;
 use Espo\ORM\Type\RelationType;
+use InvalidArgumentException;
 use LogicException;
+use RuntimeException;
 
 /**
  * @internal
  */
 class RDBRelations implements Relations
 {
-    /** @var array<string, Entity|Collection<Entity>|null> */
+    /** @var array<string, Entity|EntityCollection<Entity>|null> */
     private array $data = [];
+    /** @var array<string, Entity|EntityCollection<Entity>|null> */
+    private array $setData = [];
     private ?Entity $entity = null;
 
+    /** @var string[] */
+    private array $manyTypeList = [
+        RelationType::MANY_MANY,
+        RelationType::HAS_MANY,
+        RelationType::HAS_CHILDREN,
+    ];
+
     public function __construct(
         private EntityManager $entityManager,
     ) {}
@@ -59,16 +69,68 @@ class RDBRelations implements Relations
         $this->entity = $entity;
     }
 
-    public function reset(): void
+    public function reset(string $relation): void
+    {
+        unset($this->data[$relation]);
+        unset($this->setData[$relation]);
+    }
+
+    public function resetAll(): void
     {
         $this->data = [];
+        $this->setData = [];
+    }
+
+    public function isSet(string $relation): bool
+    {
+        return array_key_exists($relation, $this->setData);
+    }
+
+    /**
+     * @return Entity|EntityCollection<Entity>|null
+     */
+    public function getSet(string $relation): Entity|EntityCollection|null
+    {
+        if (!array_key_exists($relation, $this->setData)) {
+            throw new RuntimeException("Relation '$relation' is not set.");
+        }
+
+        return $this->setData[$relation];
+    }
+
+    /**
+     * @param Entity|EntityCollection<Entity>|null $related
+     */
+    public function set(string $relation, Entity|EntityCollection|null $related): void
+    {
+        $type = $this->getRelationType($relation);
+
+        if (!$type) {
+            throw new LogicException("Relation '$relation' does not exist.");
+        }
+
+        if (in_array($type, $this->manyTypeList) && !$related instanceof EntityCollection) {
+            throw new InvalidArgumentException("Non-collection passed for relation '$relation'.");
+        }
+
+        if (
+            !in_array($type, [
+                RelationType::BELONGS_TO,
+                RelationType::BELONGS_TO_PARENT,
+                RelationType::HAS_ONE,
+            ])
+        ) {
+            throw new LogicException("Relation type '$type' is not supported for setting.");
+        }
+
+        $this->setData[$relation] = $related;
     }
 
     public function getOne(string $relation): ?Entity
     {
         $entity = $this->get($relation);
 
-        if ($entity instanceof Collection) {
+        if ($entity instanceof EntityCollection) {
             throw new LogicException("Not an entity. Use `getMany` instead.");
         }
 
@@ -96,16 +158,16 @@ class RDBRelations implements Relations
      */
     private function get(string $relation): Entity|EntityCollection|null
     {
+        if (array_key_exists($relation, $this->setData)) {
+            return $this->setData[$relation];
+        }
+
         if (!array_key_exists($relation, $this->data)) {
             if (!$this->entity) {
                 throw new LogicException("No entity set.");
             }
 
-            $isMany = in_array($this->getRelationType($relation), [
-                RelationType::MANY_MANY,
-                RelationType::HAS_MANY,
-                RelationType::HAS_CHILDREN,
-            ]);
+            $isMany = in_array($this->getRelationType($relation), $this->manyTypeList);
 
             $this->data[$relation] = $isMany ?
                 $this->findMany($relation) :
@@ -114,7 +176,7 @@ class RDBRelations implements Relations
 
         $object = $this->data[$relation];
 
-        if ($object instanceof Collection) {
+        if ($object instanceof EntityCollection) {
             /** @var EntityCollection<Entity> $object */
             $object = new EntityCollection(iterator_to_array($object));
         }
@@ -183,7 +245,7 @@ class RDBRelations implements Relations
         return $collection;
     }
 
-    private function getRelationType(string $relation): string
+    private function getRelationType(string $relation): ?string
     {
         if (!$this->entity) {
             throw new LogicException();
@@ -192,7 +254,7 @@ class RDBRelations implements Relations
         return $this->entityManager
             ->getDefs()
             ->getEntity($this->entity->getEntityType())
-            ->getRelation($relation)
-            ->getType();
+            ->tryGetRelation($relation)
+            ?->getType();
     }
 }
diff --git a/application/Espo/ORM/Relation/Relations.php b/application/Espo/ORM/Relation/Relations.php
index 5e84d02d9f..a5138854fe 100644
--- a/application/Espo/ORM/Relation/Relations.php
+++ b/application/Espo/ORM/Relation/Relations.php
@@ -33,14 +33,31 @@ use Espo\ORM\Entity;
 use Espo\ORM\EntityCollection;
 
 /**
- * @internal
+ * @internal Not ready for production.
  */
 interface Relations
 {
     /**
-     * Reset.
+     * Reset a specific relation.
      */
-    public function reset(): void;
+    public function reset(string $relation): void;
+
+    /**
+     * Reset all.
+     */
+    public function resetAll(): void;
+
+    /**
+     * @param Entity|EntityCollection<Entity>|null $related
+     */
+    public function set(string $relation, Entity|EntityCollection|null $related): void;
+
+    public function isSet(string $relation): bool;
+
+    /**
+     * @return Entity|EntityCollection<Entity>|null
+     */
+    public function getSet(string $relation): Entity|EntityCollection|null;
 
     /**
      * Get one related record. For has-one, belongs-to.
diff --git a/application/Espo/ORM/Repository/RDBRepository.php b/application/Espo/ORM/Repository/RDBRepository.php
index cb57281b70..d0b047f5cf 100644
--- a/application/Espo/ORM/Repository/RDBRepository.php
+++ b/application/Espo/ORM/Repository/RDBRepository.php
@@ -182,7 +182,7 @@ class RDBRepository implements Repository
             $entity->setAsNotBeingSaved();
         }
 
-        $this->relationsMap?->get($entity)?->reset();
+        $this->relationsMap?->get($entity)?->resetAll();
     }
 
     /**