diff --git a/backend/app/models/models.py b/backend/app/models/models.py
index 4511eb5..f71a237 100755
--- a/backend/app/models/models.py
+++ b/backend/app/models/models.py
@@ -261,7 +261,7 @@ class SpecVersion(Base):
     )
     version_number: Mapped[int] = mapped_column(Integer, nullable=False)
     content: Mapped[str] = mapped_column(Text, nullable=False)
-    source_document_ids: Mapped[Optional[dict]] = mapped_column(JSONB, nullable=True)
+    source_document_ids: Mapped[Optional[list]] = mapped_column(JSONB, nullable=True)
     generated_by_id: Mapped[Optional[uuid.UUID]] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=True)
     generated_by_name: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
     processing_job_id: Mapped[Optional[uuid.UUID]] = mapped_column(
diff --git a/backend/app/services/knowledge_base_service.py b/backend/app/services/knowledge_base_service.py
index bfcabaa..7863184 100644
--- a/backend/app/services/knowledge_base_service.py
+++ b/backend/app/services/knowledge_base_service.py
@@ -292,10 +292,17 @@ class KnowledgeBaseService:
                 prompt = prompt_template.format(combined_markdown=combined_markdown)
 
                 logger.info(f"[KB_SERVICE] Sending {len(combined_markdown)} chars to Gemini for distillation")
-                response = await self.gemini.primary_client.aio.models.generate_content(
-                    model=self.gemini.model,
-                    contents=prompt,
-                )
+                try:
+                    response = await self.gemini.primary_client.aio.models.generate_content(
+                        model=self.gemini.model,
+                        contents=prompt,
+                    )
+                except Exception as e:
+                    logger.warning(f"[KB_SERVICE] Primary model failed: {e}. Retrying with fallback.")
+                    response = await self.gemini.fallback_client.aio.models.generate_content(
+                        model=self.gemini.fallback_model,
+                        contents=prompt,
+                    )
                 spec_content = response.text.strip()
                 logger.info(f"[KB_SERVICE] Distillation complete: {len(spec_content)} chars")