diff --git a/backend/capellacollab/core/database/__init__.py b/backend/capellacollab/core/database/__init__.py
index 12fdc4be6d..581e427b21 100644
--- a/backend/capellacollab/core/database/__init__.py
+++ b/backend/capellacollab/core/database/__init__.py
@@ -17,7 +17,7 @@
 SessionLocal = orm.sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
 
-class Base(orm.DeclarativeBase):
+class Base(orm.MappedAsDataclass, orm.DeclarativeBase):
     type_annotation_map = {
         dict[str, str]: postgresql.JSONB,
         dict[str, t.Any]: postgresql.JSONB,
diff --git a/backend/capellacollab/core/database/migration.py b/backend/capellacollab/core/database/migration.py
index 66ddbc1491..6be39b3732 100644
--- a/backend/capellacollab/core/database/migration.py
+++ b/backend/capellacollab/core/database/migration.py
@@ -84,7 +84,7 @@ def migrate_db(engine, database_url: str):
                 create_coffee_machine_model(session)
 
 
-def initialize_admin_user(db):
+def initialize_admin_user(db: orm.Session):
     LOGGER.info("Initialized adminuser %s", config["initial"]["admin"])
     admin_user = users_crud.create_user(
         db=db,
@@ -94,7 +94,7 @@ def initialize_admin_user(db):
     events_crud.create_user_creation_event(db, admin_user)
 
 
-def initialize_default_project(db):
+def initialize_default_project(db: orm.Session):
     LOGGER.info("Initialized project 'default'")
     projects_crud.create_project(
         db=db,
@@ -104,7 +104,7 @@ def initialize_default_project(db):
     )
 
 
-def initialize_coffee_machine_project(db):
+def initialize_coffee_machine_project(db: orm.Session):
     LOGGER.info("Initialize project 'Coffee Machine'")
     projects_crud.create_project(
         db=db,
@@ -114,7 +114,7 @@ def initialize_coffee_machine_project(db):
     )
 
 
-def create_tools(db):
+def create_tools(db: orm.Session):
     LOGGER.info("Initialized tools")
     registry = config["docker"]["registry"]
     if os.getenv("DEVELOPMENT_MODE", "").lower() in ("1", "true", "t"):
@@ -131,12 +131,12 @@ def create_tools(db):
         )
         tools_crud.create_tool(db, papyrus)
 
-        tools_crud.create_version(db, papyrus.id, "6.1")
-        tools_crud.create_version(db, papyrus.id, "6.0")
+        tools_crud.create_version(db, papyrus, "6.1")
+        tools_crud.create_version(db, papyrus, "6.0")
 
-        tools_crud.create_nature(db, papyrus.id, "UML 2.5")
-        tools_crud.create_nature(db, papyrus.id, "SysML 1.4")
-        tools_crud.create_nature(db, papyrus.id, "SysML 1.1")
+        tools_crud.create_nature(db, papyrus, "UML 2.5")
+        tools_crud.create_nature(db, papyrus, "SysML 1.4")
+        tools_crud.create_nature(db, papyrus, "SysML 1.1")
 
     else:
         # Use public Github images per default
@@ -160,15 +160,15 @@ def create_tools(db):
         integrations_models.PatchToolIntegrations(jupyter=True),
     )
 
-    default_version = tools_crud.create_version(db, capella.id, "6.0.0", True)
-    tools_crud.create_version(db, capella.id, "5.2.0")
-    tools_crud.create_version(db, capella.id, "5.0.0")
+    default_version = tools_crud.create_version(db, capella, "6.0.0", True)
+    tools_crud.create_version(db, capella, "5.2.0")
+    tools_crud.create_version(db, capella, "5.0.0")
 
-    tools_crud.create_version(db, jupyter.id, "python-3.11")
-    tools_crud.create_nature(db, jupyter.id, "notebooks")
+    tools_crud.create_version(db, jupyter, "python-3.11")
+    tools_crud.create_nature(db, jupyter, "notebooks")
 
-    default_nature = tools_crud.create_nature(db, capella.id, "model")
-    tools_crud.create_nature(db, capella.id, "library")
+    default_nature = tools_crud.create_nature(db, capella, "model")
+    tools_crud.create_nature(db, capella, "library")
 
     for model in toolmodels_crud.get_models(db):
         toolmodels_crud.set_tool_for_model(db, model, capella)
diff --git a/backend/capellacollab/events/crud.py b/backend/capellacollab/events/crud.py
index b63df31c21..12954b949f 100644
--- a/backend/capellacollab/events/crud.py
+++ b/backend/capellacollab/events/crud.py
@@ -26,14 +26,16 @@ def create_event(
         raise ValueError(
             f"Event type must of one of the following: {allowed_types}"
         )
+
     event = models.DatabaseUserHistoryEvent(
-        user_id=user.id,
+        user=user,
         event_type=event_type,
         execution_time=datetime.datetime.now(datetime.UTC),
-        executor_id=executor.id if executor else None,
-        project_id=project.id if project else None,
+        executor=executor,
+        project=project,
         reason=reason,
     )
+
     db.add(event)
     db.commit()
 
diff --git a/backend/capellacollab/events/models.py b/backend/capellacollab/events/models.py
index b74186bfe9..fb5ed2e10f 100644
--- a/backend/capellacollab/events/models.py
+++ b/backend/capellacollab/events/models.py
@@ -14,10 +14,6 @@
 from capellacollab.projects import models as projects_models
 from capellacollab.users import models as users_models
 
-if t.TYPE_CHECKING:
-    from capellacollab.projects.models import DatabaseProject
-    from capellacollab.users.models import DatabaseUser
-
 
 class EventType(enum.Enum):
     CREATED_USER = "CreatedUser"
@@ -55,27 +51,37 @@ class HistoryEvent(BaseHistoryEvent):
 class DatabaseUserHistoryEvent(database.Base):
     __tablename__ = "user_history_events"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True, index=True)
+    id: orm.Mapped[int] = orm.mapped_column(
+        init=False, primary_key=True, index=True
+    )
 
-    user_id: orm.Mapped[int] = orm.mapped_column(sa.ForeignKey("users.id"))
-    user: orm.Mapped["DatabaseUser"] = orm.relationship(
+    user_id: orm.Mapped[int] = orm.mapped_column(
+        sa.ForeignKey("users.id"),
+        init=False,
+    )
+    user: orm.Mapped[users_models.DatabaseUser] = orm.relationship(
         back_populates="events", foreign_keys=[user_id]
     )
 
+    event_type: orm.Mapped[EventType]
+    reason: orm.Mapped[str | None] = orm.mapped_column(default=None)
+
     executor_id: orm.Mapped[int | None] = orm.mapped_column(
-        sa.ForeignKey("users.id")
+        sa.ForeignKey("users.id"),
+        init=False,
     )
-    executor: orm.Mapped["DatabaseUser"] = orm.relationship(
-        foreign_keys=[executor_id]
+    executor: orm.Mapped[users_models.DatabaseUser | None] = orm.relationship(
+        default=None, foreign_keys=[executor_id]
     )
 
     project_id: orm.Mapped[int | None] = orm.mapped_column(
-        sa.ForeignKey("projects.id")
-    )
-    project: orm.Mapped["DatabaseProject"] = orm.relationship(
-        foreign_keys=[project_id]
+        sa.ForeignKey("projects.id"),
+        init=False,
     )
+    project: orm.Mapped[
+        projects_models.DatabaseProject | None
+    ] = orm.relationship(default=None, foreign_keys=[project_id])
 
-    execution_time: orm.Mapped[datetime.datetime]
-    event_type: orm.Mapped[EventType]
-    reason: orm.Mapped[str | None]
+    execution_time: orm.Mapped[datetime.datetime] = orm.mapped_column(
+        default=datetime.datetime.now(datetime.UTC)
+    )
diff --git a/backend/capellacollab/notices/models.py b/backend/capellacollab/notices/models.py
index ef38002985..e454a21f6a 100644
--- a/backend/capellacollab/notices/models.py
+++ b/backend/capellacollab/notices/models.py
@@ -34,7 +34,9 @@ class NoticeResponse(CreateNoticeRequest):
 class DatabaseNotice(database.Base):
     __tablename__ = "notices"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True, index=True)
+    id: orm.Mapped[int] = orm.mapped_column(
+        init=False, primary_key=True, index=True
+    )
     title: orm.Mapped[str]
     message: orm.Mapped[str]
     level: orm.Mapped[NoticeLevel]
diff --git a/backend/capellacollab/projects/models.py b/backend/capellacollab/projects/models.py
index be808655c6..675f3caa02 100644
--- a/backend/capellacollab/projects/models.py
+++ b/backend/capellacollab/projects/models.py
@@ -105,20 +105,25 @@ class DatabaseProject(database.Base):
     __tablename__ = "projects"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        unique=True, primary_key=True, index=True
+        init=False, unique=True, primary_key=True, index=True
     )
 
     name: orm.Mapped[str] = orm.mapped_column(unique=True, index=True)
     slug: orm.Mapped[str] = orm.mapped_column(unique=True, index=True)
-    description: orm.Mapped[str | None]
-    visibility: orm.Mapped[Visibility]
-    type: orm.Mapped[ProjectType]
+
+    description: orm.Mapped[str | None] = orm.mapped_column(default=None)
+    visibility: orm.Mapped[Visibility] = orm.mapped_column(
+        default=Visibility.PRIVATE
+    )
+    type: orm.Mapped[ProjectType] = orm.mapped_column(
+        default=ProjectType.GENERAL
+    )
 
     users: orm.Mapped[list[ProjectUserAssociation]] = orm.relationship(
-        back_populates="project"
+        default_factory=list, back_populates="project"
     )
     models: orm.Mapped[list[DatabaseCapellaModel]] = orm.relationship(
-        back_populates="project"
+        default_factory=list, back_populates="project"
     )
 
     is_archived: orm.Mapped[bool] = orm.mapped_column(default=False)
diff --git a/backend/capellacollab/projects/toolmodels/backups/models.py b/backend/capellacollab/projects/toolmodels/backups/models.py
index 356010a270..1efd3e9429 100644
--- a/backend/capellacollab/projects/toolmodels/backups/models.py
+++ b/backend/capellacollab/projects/toolmodels/backups/models.py
@@ -51,7 +51,7 @@ class Backup(pydantic.BaseModel):
 class DatabaseBackup(database.Base):
     __tablename__ = "backups"
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True
+        init=False, primary_key=True, index=True, autoincrement=True
     )
 
     created_by: orm.Mapped[str]
diff --git a/backend/capellacollab/projects/toolmodels/backups/runs/models.py b/backend/capellacollab/projects/toolmodels/backups/runs/models.py
index 21204aa43e..b5007b6dfd 100644
--- a/backend/capellacollab/projects/toolmodels/backups/runs/models.py
+++ b/backend/capellacollab/projects/toolmodels/backups/runs/models.py
@@ -28,7 +28,7 @@ class PipelineRunStatus(enum.Enum):
 class DatabasePipelineRun(Base):
     __tablename__ = "pipeline_run"
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True
+        init=False, primary_key=True, index=True, autoincrement=True
     )
     reference_id: orm.Mapped[str | None]
 
diff --git a/backend/capellacollab/projects/toolmodels/models.py b/backend/capellacollab/projects/toolmodels/models.py
index 0ab55fd171..66120c0cb7 100644
--- a/backend/capellacollab/projects/toolmodels/models.py
+++ b/backend/capellacollab/projects/toolmodels/models.py
@@ -67,7 +67,7 @@ class DatabaseCapellaModel(database.Base):
     __table_args__ = (sa.UniqueConstraint("project_id", "slug"),)
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, unique=True
+        init=False, primary_key=True, index=True, unique=True
     )
 
     name: orm.Mapped[str] = orm.mapped_column(index=True)
diff --git a/backend/capellacollab/projects/toolmodels/modelsources/t4c/models.py b/backend/capellacollab/projects/toolmodels/modelsources/t4c/models.py
index 7fc1f740ae..3c08629fbf 100644
--- a/backend/capellacollab/projects/toolmodels/modelsources/t4c/models.py
+++ b/backend/capellacollab/projects/toolmodels/modelsources/t4c/models.py
@@ -28,7 +28,7 @@ class DatabaseT4CModel(database.Base):
     )
 
     id: orm.Mapped[int] = orm.mapped_column(
-        unique=True, primary_key=True, index=True
+        init=False, unique=True, primary_key=True, index=True
     )
     name: orm.Mapped[str] = orm.mapped_column(index=True)
 
diff --git a/backend/capellacollab/projects/toolmodels/restrictions/models.py b/backend/capellacollab/projects/toolmodels/restrictions/models.py
index e2d93d2a07..544e3f76fc 100644
--- a/backend/capellacollab/projects/toolmodels/restrictions/models.py
+++ b/backend/capellacollab/projects/toolmodels/restrictions/models.py
@@ -28,7 +28,7 @@ class DatabaseToolModelRestrictions(database.Base):
     __tablename__ = "model_restrictions"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, unique=True
+        init=False, primary_key=True, index=True, unique=True
     )
 
     model_id: orm.Mapped[int] = orm.mapped_column(sa.ForeignKey("models.id"))
diff --git a/backend/capellacollab/settings/configuration/models.py b/backend/capellacollab/settings/configuration/models.py
index 829395a052..ea554bfcf1 100644
--- a/backend/capellacollab/settings/configuration/models.py
+++ b/backend/capellacollab/settings/configuration/models.py
@@ -14,7 +14,7 @@ class DatabaseConfiguration(database.Base):
     __tablename__ = "configuration"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        unique=True, primary_key=True, index=True
+        init=False, unique=True, primary_key=True, index=True
     )
 
     name: orm.Mapped[str] = orm.mapped_column(unique=True, index=True)
diff --git a/backend/capellacollab/settings/integrations/purevariants/models.py b/backend/capellacollab/settings/integrations/purevariants/models.py
index bae5c84238..da77d1ad2b 100644
--- a/backend/capellacollab/settings/integrations/purevariants/models.py
+++ b/backend/capellacollab/settings/integrations/purevariants/models.py
@@ -28,7 +28,9 @@ def validate_license_url(value: str | None):
 class DatabasePureVariantsLicenses(database.Base):
     __tablename__ = "pure_variants"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True, index=True)
+    id: orm.Mapped[int] = orm.mapped_column(
+        init=False, primary_key=True, index=True
+    )
     license_server_url: orm.Mapped[str | None]
     license_key_filename: orm.Mapped[str | None]
 
diff --git a/backend/capellacollab/settings/modelsources/git/models.py b/backend/capellacollab/settings/modelsources/git/models.py
index fa47081460..f408c60673 100644
--- a/backend/capellacollab/settings/modelsources/git/models.py
+++ b/backend/capellacollab/settings/modelsources/git/models.py
@@ -34,7 +34,7 @@ class DatabaseGitInstance(database.Base):
     __tablename__ = "git_instances"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True
+        init=False, primary_key=True, index=True, autoincrement=True
     )
 
     name: orm.Mapped[str]
diff --git a/backend/capellacollab/settings/modelsources/t4c/models.py b/backend/capellacollab/settings/modelsources/t4c/models.py
index 91ad5d6586..546e55439e 100644
--- a/backend/capellacollab/settings/modelsources/t4c/models.py
+++ b/backend/capellacollab/settings/modelsources/t4c/models.py
@@ -46,20 +46,14 @@ class DatabaseT4CInstance(database.Base):
     __tablename__ = "t4c_instances"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True
+        init=False, primary_key=True, index=True, autoincrement=True
     )
 
     name: orm.Mapped[str] = orm.mapped_column(unique=True)
 
     license: orm.Mapped[str]
     host: orm.Mapped[str]
-    port: orm.Mapped[int] = orm.mapped_column(
-        sa.CheckConstraint("port >= 0 AND port <= 65535"), default=2036
-    )
-    cdo_port: orm.Mapped[int] = orm.mapped_column(
-        sa.CheckConstraint("cdo_port >= 0 AND cdo_port <= 65535"),
-        default=12036,
-    )
+
     http_port: orm.Mapped[int | None] = orm.mapped_column(
         sa.CheckConstraint("http_port >= 0 AND http_port <= 65535"),
     )
@@ -68,8 +62,6 @@ class DatabaseT4CInstance(database.Base):
     username: orm.Mapped[str]
     password: orm.Mapped[str]
 
-    protocol: orm.Mapped[Protocol] = orm.mapped_column(default=Protocol.tcp)
-
     version_id: orm.Mapped[int] = orm.mapped_column(
         sa.ForeignKey("versions.id")
     )
@@ -79,6 +71,15 @@ class DatabaseT4CInstance(database.Base):
         back_populates="instance", cascade="all, delete"
     )
 
+    port: orm.Mapped[int] = orm.mapped_column(
+        sa.CheckConstraint("port >= 0 AND port <= 65535"), default=2036
+    )
+    cdo_port: orm.Mapped[int] = orm.mapped_column(
+        sa.CheckConstraint("cdo_port >= 0 AND cdo_port <= 65535"),
+        default=12036,
+    )
+    protocol: orm.Mapped[Protocol] = orm.mapped_column(default=Protocol.tcp)
+
     is_archived: orm.Mapped[bool] = orm.mapped_column(default=False)
 
 
diff --git a/backend/capellacollab/settings/modelsources/t4c/repositories/models.py b/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
index 2786d71f15..cad2ff8214 100644
--- a/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
+++ b/backend/capellacollab/settings/modelsources/t4c/repositories/models.py
@@ -27,7 +27,11 @@ class DatabaseT4CRepository(database.Base):
     __table_args__ = (sa.UniqueConstraint("instance_id", "name"),)
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True, unique=True
+        init=False,
+        primary_key=True,
+        index=True,
+        autoincrement=True,
+        unique=True,
     )
     name: orm.Mapped[str]
 
diff --git a/backend/capellacollab/tools/crud.py b/backend/capellacollab/tools/crud.py
index 9692e9b8ec..044820ead9 100644
--- a/backend/capellacollab/tools/crud.py
+++ b/backend/capellacollab/tools/crud.py
@@ -38,7 +38,7 @@ def create_tool(
     db: orm.Session, tool: models.DatabaseTool
 ) -> models.DatabaseTool:
     tool.integrations = integrations_models.DatabaseToolIntegrations(
-        pure_variants=False, t4c=False, jupyter=False
+        tool=tool, pure_variants=False, t4c=False, jupyter=False
     )
     db.add(tool)
     db.commit()
@@ -151,7 +151,7 @@ def update_version(
 
 def create_version(
     db: orm.Session,
-    tool_id: int,
+    tool: models.DatabaseTool,
     name: str,
     is_recommended: bool = False,
     is_deprecated: bool = False,
@@ -160,7 +160,7 @@ def create_version(
         name=name,
         is_recommended=is_recommended,
         is_deprecated=is_deprecated,
-        tool_id=tool_id,
+        tool=tool,
     )
     db.add(version)
     db.commit()
@@ -223,9 +223,9 @@ def get_natures_by_tool_id(
 
 
 def create_nature(
-    db: orm.Session, tool_id: int, name: str
+    db: orm.Session, tool: models.DatabaseTool, name: str
 ) -> models.DatabaseNature:
-    nature = models.DatabaseNature(name=name, tool_id=tool_id)
+    nature = models.DatabaseNature(name=name, tool=tool)
     db.add(nature)
     db.commit()
     return nature
diff --git a/backend/capellacollab/tools/integrations/models.py b/backend/capellacollab/tools/integrations/models.py
index 9615d5663b..937885194e 100644
--- a/backend/capellacollab/tools/integrations/models.py
+++ b/backend/capellacollab/tools/integrations/models.py
@@ -32,9 +32,11 @@ class PatchToolIntegrations(pydantic.BaseModel):
 class DatabaseToolIntegrations(database.Base):
     __tablename__ = "tool_integrations"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+    id: orm.Mapped[int] = orm.mapped_column(init=False, primary_key=True)
 
-    tool_id: orm.Mapped[int] = orm.mapped_column(sa.ForeignKey("tools.id"))
+    tool_id: orm.Mapped[int] = orm.mapped_column(
+        sa.ForeignKey("tools.id"), init=False
+    )
     tool: orm.Mapped[DatabaseTool] = orm.relationship(
         back_populates="integrations"
     )
diff --git a/backend/capellacollab/tools/models.py b/backend/capellacollab/tools/models.py
index ec682ad095..07016ef2af 100644
--- a/backend/capellacollab/tools/models.py
+++ b/backend/capellacollab/tools/models.py
@@ -20,22 +20,30 @@
 class DatabaseTool(database.Base):
     __tablename__ = "tools"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+    id: orm.Mapped[int] = orm.mapped_column(init=False, primary_key=True)
 
     name: orm.Mapped[str]
     docker_image_template: orm.Mapped[str]
-    docker_image_backup_template: orm.Mapped[str | None]
-    readonly_docker_image_template: orm.Mapped[str | None]
+    docker_image_backup_template: orm.Mapped[str | None] = orm.mapped_column(
+        default=None
+    )
+    readonly_docker_image_template: orm.Mapped[str | None] = orm.mapped_column(
+        default=None
+    )
+
+    integrations: orm.Mapped[
+        DatabaseToolIntegrations | None
+    ] = orm.relationship(
+        default=None,
+        back_populates="tool",
+        uselist=False,
+    )
 
     versions: orm.Mapped[list[DatabaseVersion]] = orm.relationship(
-        back_populates="tool"
+        default_factory=list, back_populates="tool"
     )
     natures: orm.Mapped[list[DatabaseNature]] = orm.relationship(
-        back_populates="tool"
-    )
-
-    integrations: orm.Mapped[DatabaseToolIntegrations] = orm.relationship(
-        back_populates="tool", uselist=False
+        default_factory=list, back_populates="tool"
     )
 
 
@@ -43,14 +51,15 @@ class DatabaseVersion(database.Base):
     __tablename__ = "versions"
     __table_args__ = (sa.UniqueConstraint("tool_id", "name"),)
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+    id: orm.Mapped[int] = orm.mapped_column(init=False, primary_key=True)
 
     name: orm.Mapped[str]
     is_recommended: orm.Mapped[bool]
     is_deprecated: orm.Mapped[bool]
 
     tool_id: orm.Mapped[int | None] = orm.mapped_column(
-        sa.ForeignKey("tools.id")
+        sa.ForeignKey("tools.id"),
+        init=False,
     )
     tool: orm.Mapped[DatabaseTool] = orm.relationship(
         back_populates="versions"
@@ -61,7 +70,7 @@ class DatabaseNature(database.Base):
     __tablename__ = "types"
     __table_args__ = (sa.UniqueConstraint("tool_id", "name"),)
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+    id: orm.Mapped[int] = orm.mapped_column(init=False, primary_key=True)
     name: orm.Mapped[str]
 
     tool_id: orm.Mapped[int | None] = orm.mapped_column(
diff --git a/backend/capellacollab/tools/routes.py b/backend/capellacollab/tools/routes.py
index 0b89b32072..668310a58a 100644
--- a/backend/capellacollab/tools/routes.py
+++ b/backend/capellacollab/tools/routes.py
@@ -130,7 +130,7 @@ def create_tool_version(
     tool: models.DatabaseTool = fastapi.Depends(injectables.get_existing_tool),
     db: orm.Session = fastapi.Depends(database.get_db),
 ) -> models.DatabaseVersion:
-    return crud.create_version(db, tool.id, body.name)
+    return crud.create_version(db, tool, body.name)
 
 
 @router.patch(
@@ -194,11 +194,11 @@ def get_tool_natures(
     ],
 )
 def create_tool_nature(
-    tool_id: int,
     body: models.CreateToolNature,
+    tool: models.DatabaseTool = fastapi.Depends(injectables.get_existing_tool),
     db: orm.Session = fastapi.Depends(database.get_db),
 ) -> models.DatabaseNature:
-    return crud.create_nature(db, tool_id, body.name)
+    return crud.create_nature(db, tool, body.name)
 
 
 @router.delete(
diff --git a/backend/capellacollab/users/models.py b/backend/capellacollab/users/models.py
index d1ffef652e..a4431c886e 100644
--- a/backend/capellacollab/users/models.py
+++ b/backend/capellacollab/users/models.py
@@ -8,7 +8,7 @@
 import typing as t
 
 import pydantic
-from sqlalchemy import orm
+from sqlalchemy import func, orm
 
 from capellacollab.core import database
 from capellacollab.core import pydantic as core_pydantic
@@ -59,23 +59,34 @@ class PostUser(pydantic.BaseModel):
 class DatabaseUser(database.Base):
     __tablename__ = "users"
 
-    id: orm.Mapped[int] = orm.mapped_column(primary_key=True, index=True)
+    id: orm.Mapped[int] = orm.mapped_column(
+        init=False, primary_key=True, index=True
+    )
 
     name: orm.Mapped[str] = orm.mapped_column(unique=True, index=True)
     role: orm.Mapped[Role]
-    created: orm.Mapped[datetime.datetime | None]
-    last_login: orm.Mapped[datetime.datetime | None]
+    created: orm.Mapped[datetime.datetime | None] = orm.mapped_column(
+        default=datetime.datetime.now(datetime.UTC)
+    )
 
     projects: orm.Mapped[list[ProjectUserAssociation]] = orm.relationship(
-        back_populates="user"
+        default_factory=list, back_populates="user"
     )
     sessions: orm.Mapped[list[DatabaseSession]] = orm.relationship(
-        back_populates="owner"
+        default_factory=list, back_populates="owner"
     )
     events: orm.Mapped[list[DatabaseUserHistoryEvent]] = orm.relationship(
-        back_populates="user", foreign_keys="DatabaseUserHistoryEvent.user_id"
+        default_factory=list,
+        back_populates="user",
+        foreign_keys="DatabaseUserHistoryEvent.user_id",
     )
 
     tokens: orm.Mapped[list[DatabaseUserToken]] = orm.relationship(
-        back_populates="user", cascade="all, delete-orphan"
+        default_factory=list,
+        back_populates="user",
+        cascade="all, delete-orphan",
+    )
+
+    last_login: orm.Mapped[datetime.datetime | None] = orm.mapped_column(
+        default=None
     )
diff --git a/backend/capellacollab/users/tokens/models.py b/backend/capellacollab/users/tokens/models.py
index 38345a8403..7f3cee2128 100644
--- a/backend/capellacollab/users/tokens/models.py
+++ b/backend/capellacollab/users/tokens/models.py
@@ -38,7 +38,7 @@ class DatabaseUserToken(database.Base):
     __tablename__ = "basic_auth_token"
 
     id: orm.Mapped[int] = orm.mapped_column(
-        primary_key=True, index=True, autoincrement=True
+        init=False, primary_key=True, index=True, autoincrement=True
     )
     user_id: orm.Mapped[int] = orm.mapped_column(sa.ForeignKey("users.id"))
     user: orm.Mapped["DatabaseUser"] = orm.relationship(
diff --git a/backend/tests/sessions/test_sessions_routes.py b/backend/tests/sessions/test_sessions_routes.py
index 695c6b906d..cfdec31752 100644
--- a/backend/tests/sessions/test_sessions_routes.py
+++ b/backend/tests/sessions/test_sessions_routes.py
@@ -34,14 +34,8 @@
 )
 from capellacollab.sessions.operators import get_operator
 from capellacollab.sessions.operators import models as operators_models
+from capellacollab.tools import crud as tools_crud
 from capellacollab.tools import models as tools_models
-from capellacollab.tools.crud import (
-    create_tool,
-    create_tool_with_name,
-    create_version,
-    get_natures,
-    get_versions,
-)
 from capellacollab.tools.integrations.crud import update_integrations
 from capellacollab.tools.integrations.models import PatchToolIntegrations
 from capellacollab.users.crud import create_user
@@ -179,7 +173,7 @@ def test_create_readonly_session_as_user(
 ):
     _, version = next(
         (v.tool, v)
-        for v in get_versions(db)
+        for v in tools_crud.get_versions(db)
         if v.tool.name == "Capella" and v.name == "5.0.0"
     )
 
@@ -217,8 +211,8 @@ def test_create_readonly_session_as_user(
 
 
 def test_no_readonly_session_as_user(client, db, user, kubernetes):
-    tool = create_tool_with_name(db, "Test")
-    version = create_version(db, tool.id, "test")
+    tool = tools_crud.create_tool_with_name(db, "Test")
+    version = tools_crud.create_version(db, tool, "test")
 
     model, git_model = setup_git_model_for_user(db, user, version)
 
@@ -249,7 +243,7 @@ def test_one_readonly_sessions_as_user_per_tool_version(
 ):
     version = next(
         v
-        for v in get_versions(db)
+        for v in tools_crud.get_versions(db)
         if v.tool.name == "Capella" and v.name == "5.0.0"
     )
 
@@ -276,7 +270,7 @@ def test_one_readonly_sessions_as_user_per_tool_version(
 
 def setup_git_model_for_user(db, user, version):
     project = create_project(db, name=str(uuid1()))
-    nature = get_natures(db)[0]
+    nature = tools_crud.get_natures(db)[0]
     add_user_to_project(
         db,
         project,
@@ -357,7 +351,7 @@ def test_create_read_only_session_as_user(
 ):
     version = next(
         v
-        for v in get_versions(db)
+        for v in tools_crud.get_versions(db)
         if v.tool.name == "Capella" and v.name == "6.0.0"
     )
 
@@ -377,7 +371,6 @@ def test_create_read_only_session_as_user(
         },
     )
     out = response.json()
-    print(out)
     session = get_session_by_id(db, out["id"])
 
     assert response.status_code == 200
@@ -393,7 +386,7 @@ def test_create_read_only_session_as_user(
 
 
 def test_create_persistent_jupyter_session(client, db, user, kubernetes):
-    jupyter = create_tool(
+    jupyter = tools_crud.create_tool(
         db,
         tools_models.DatabaseTool(
             name="jupyter",
@@ -404,8 +397,8 @@ def test_create_persistent_jupyter_session(client, db, user, kubernetes):
         db, jupyter.integrations, PatchToolIntegrations(jupyter=True)
     )
 
-    jupyter_version = create_version(
-        db, name="python-3.10.8", tool_id=jupyter.id
+    jupyter_version = tools_crud.create_version(
+        db, name="python-3.10.8", tool=jupyter
     )
 
     response = client.post(
diff --git a/backend/tests/settings/conftest.py b/backend/tests/settings/conftest.py
index d0aa936b11..e27b2bd9ae 100644
--- a/backend/tests/settings/conftest.py
+++ b/backend/tests/settings/conftest.py
@@ -15,7 +15,7 @@
 @pytest.fixture(name="test_tool_version")
 def fixture_test_tool_version(db: orm.Session) -> tools_models.DatabaseVersion:
     tool = tools_crud.create_tool_with_name(db, "Test")
-    return tools_crud.create_version(db, tool.id, "test")
+    return tools_crud.create_version(db, tool, "test")
 
 
 @pytest.fixture(name="admin_user")