diff --git a/backend/app/db/base_class.py b/backend/app/db/base_class.py
index fa2b68a5..92ce9cf3 100644
--- a/backend/app/db/base_class.py
+++ b/backend/app/db/base_class.py
@@ -1,5 +1,45 @@
+from __future__ import annotations
+
+import uuid
+
+from sqlalchemy import String, TypeDecorator
+from sqlalchemy.dialects.postgresql import UUID as PG_UUID
 from sqlalchemy.orm import DeclarativeBase
 
 
+class GUID(TypeDecorator):
+    """Platform-independent UUID type.
+
+    PostgreSQL keeps native UUID columns; SQLite test databases store canonical
+    UUID strings so bind/result behavior stays consistent.
+    """
+
+    impl = String
+    cache_ok = True
+
+    def load_dialect_impl(self, dialect):
+        if dialect.name == "sqlite":
+            return dialect.type_descriptor(String(36))
+        return dialect.type_descriptor(PG_UUID(as_uuid=True))
+
+    def process_bind_param(self, value, dialect):
+        if value is None:
+            return None
+        if dialect.name == "sqlite":
+            return str(value)
+        return value
+
+    def process_result_value(self, value, dialect):
+        if value is None:
+            return None
+        if dialect.name == "sqlite" and isinstance(value, str):
+            return uuid.UUID(value)
+        return value
+
+
 class Base(DeclarativeBase):
+    type_annotation_map = {
+        uuid.UUID: GUID(),
+    }
+
     pass
diff --git a/backend/app/models/study_setup_config.py b/backend/app/models/study_setup_config.py
index 0fb8ad27..26dda9d8 100644
--- a/backend/app/models/study_setup_config.py
+++ b/backend/app/models/study_setup_config.py
@@ -4,12 +4,14 @@ from typing import Optional
 import uuid
 from datetime import datetime
 
-from sqlalchemy import DateTime, ForeignKey, Integer, UniqueConstraint, func
+from sqlalchemy import DateTime, ForeignKey, Integer, JSON, UniqueConstraint, func
 from sqlalchemy.dialects.postgresql import JSONB, UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.db.base_class import Base
 
+JSONB_TYPE = JSON().with_variant(JSONB, "postgresql")
+
 
 class StudySetupConfig(Base):
     __tablename__ = "study_setup_configs"
@@ -18,10 +20,10 @@ class StudySetupConfig(Base):
     id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     study_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("studies.id"), nullable=False, index=True)
     version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
-    config: Mapped[dict] = mapped_column(JSONB, nullable=False)
+    config: Mapped[dict] = mapped_column(JSONB_TYPE, nullable=False)
     publish_status: Mapped[str] = mapped_column(default="DRAFT", nullable=False)
-    published_config: Mapped[dict | None] = mapped_column(JSONB, nullable=True)
-    published_project_snapshot: Mapped[dict | None] = mapped_column(JSONB, nullable=True)
+    published_config: Mapped[dict | None] = mapped_column(JSONB_TYPE, nullable=True)
+    published_project_snapshot: Mapped[dict | None] = mapped_column(JSONB_TYPE, nullable=True)
     current_branch_name: Mapped[str] = mapped_column(nullable=False, default="main")
     active_branch_base_version_id: Mapped[Optional[uuid.UUID]] = mapped_column(
         UUID(as_uuid=True), ForeignKey("study_setup_config_versions.id", ondelete="SET NULL"), nullable=True
diff --git a/backend/app/models/study_setup_config_version.py b/backend/app/models/study_setup_config_version.py
index 52d6fca1..c74a2a25 100644
--- a/backend/app/models/study_setup_config_version.py
+++ b/backend/app/models/study_setup_config_version.py
@@ -4,12 +4,14 @@ from typing import Optional
 import uuid
 from datetime import datetime
 
-from sqlalchemy import DateTime, ForeignKey, Integer, UniqueConstraint, func
+from sqlalchemy import DateTime, ForeignKey, Integer, JSON, UniqueConstraint, func
 from sqlalchemy.dialects.postgresql import JSONB, UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.db.base_class import Base
 
+JSONB_TYPE = JSON().with_variant(JSONB, "postgresql")
+
 
 class StudySetupConfigVersion(Base):
     __tablename__ = "study_setup_config_versions"
@@ -35,8 +37,8 @@ class StudySetupConfigVersion(Base):
     merged_from_version_id: Mapped[Optional[uuid.UUID]] = mapped_column(
         UUID(as_uuid=True), ForeignKey("study_setup_config_versions.id", ondelete="SET NULL"), nullable=True
     )
-    config: Mapped[dict] = mapped_column(JSONB, nullable=False)
-    published_project_snapshot: Mapped[dict | None] = mapped_column(JSONB, nullable=True)
+    config: Mapped[dict] = mapped_column(JSONB_TYPE, nullable=False)
+    published_project_snapshot: Mapped[dict | None] = mapped_column(JSONB_TYPE, nullable=True)
     published_by: Mapped[Optional[uuid.UUID]] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=True)
     published_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())