diff --git a/api/core/workflow/workflow_cycle_manager.py b/api/core/workflow/workflow_cycle_manager.py
index 6d33d7372c..673083f003 100644
--- a/api/core/workflow/workflow_cycle_manager.py
+++ b/api/core/workflow/workflow_cycle_manager.py
@@ -504,6 +504,13 @@ class WorkflowCycleManager:
         else:
             raise NotImplementedError(f"unknown created_by_role: {workflow_run.created_by_role}")
 
+        # Handle the case where finished_at is None by using current time as default
+        finished_at_timestamp = (
+            int(workflow_run.finished_at.timestamp())
+            if workflow_run.finished_at
+            else int(datetime.now(UTC).timestamp())
+        )
+
         return WorkflowFinishStreamResponse(
             task_id=task_id,
             workflow_run_id=workflow_run.id,
@@ -519,7 +526,7 @@ class WorkflowCycleManager:
                 total_steps=workflow_run.total_steps,
                 created_by=created_by,
                 created_at=int(workflow_run.created_at.timestamp()),
-                finished_at=int(workflow_run.finished_at.timestamp()),
+                finished_at=finished_at_timestamp,
                 files=self._fetch_files_from_node_outputs(dict(workflow_run.outputs_dict)),
                 exceptions_count=workflow_run.exceptions_count,
             ),
diff --git a/api/models/workflow.py b/api/models/workflow.py
index 8751fd1aa8..bdb144f7a4 100644
--- a/api/models/workflow.py
+++ b/api/models/workflow.py
@@ -425,14 +425,14 @@ class WorkflowRun(Base):
     status: Mapped[str] = mapped_column(db.String(255))  # running, succeeded, failed, stopped, partial-succeeded
     outputs: Mapped[Optional[str]] = mapped_column(sa.Text, default="{}")
     error: Mapped[Optional[str]] = mapped_column(db.Text)
-    elapsed_time = db.Column(db.Float, nullable=False, server_default=sa.text("0"))
+    elapsed_time: Mapped[float] = mapped_column(db.Float, nullable=False, server_default=sa.text("0"))
     total_tokens: Mapped[int] = mapped_column(sa.BigInteger, server_default=sa.text("0"))
-    total_steps = db.Column(db.Integer, server_default=db.text("0"))
+    total_steps: Mapped[int] = mapped_column(db.Integer, server_default=db.text("0"))
     created_by_role: Mapped[str] = mapped_column(db.String(255))  # account, end_user
-    created_by = db.Column(StringUUID, nullable=False)
-    created_at = db.Column(db.DateTime, nullable=False, server_default=func.current_timestamp())
-    finished_at = db.Column(db.DateTime)
-    exceptions_count = db.Column(db.Integer, server_default=db.text("0"))
+    created_by: Mapped[str] = mapped_column(StringUUID, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(db.DateTime, nullable=False, server_default=func.current_timestamp())
+    finished_at: Mapped[Optional[datetime]] = mapped_column(db.DateTime)
+    exceptions_count: Mapped[int] = mapped_column(db.Integer, server_default=db.text("0"))
 
     @property
     def created_by_account(self):
@@ -447,7 +447,7 @@ class WorkflowRun(Base):
         return db.session.get(EndUser, self.created_by) if created_by_role == CreatorUserRole.END_USER else None
 
     @property
-    def graph_dict(self):
+    def graph_dict(self) -> Mapping[str, Any]:
         return json.loads(self.graph) if self.graph else {}
 
     @property
@@ -749,12 +749,12 @@ class WorkflowAppLog(Base):
     id: Mapped[str] = mapped_column(StringUUID, server_default=db.text("uuid_generate_v4()"))
     tenant_id: Mapped[str] = mapped_column(StringUUID)
     app_id: Mapped[str] = mapped_column(StringUUID)
-    workflow_id = db.Column(StringUUID, nullable=False)
+    workflow_id: Mapped[str] = mapped_column(StringUUID, nullable=False)
     workflow_run_id: Mapped[str] = mapped_column(StringUUID)
-    created_from = db.Column(db.String(255), nullable=False)
-    created_by_role = db.Column(db.String(255), nullable=False)
-    created_by = db.Column(StringUUID, nullable=False)
-    created_at = db.Column(db.DateTime, nullable=False, server_default=func.current_timestamp())
+    created_from: Mapped[str] = mapped_column(db.String(255), nullable=False)
+    created_by_role: Mapped[str] = mapped_column(db.String(255), nullable=False)
+    created_by: Mapped[str] = mapped_column(StringUUID, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(db.DateTime, nullable=False, server_default=func.current_timestamp())
 
     @property
     def workflow_run(self):
@@ -779,9 +779,11 @@ class ConversationVariable(Base):
     id: Mapped[str] = mapped_column(StringUUID, primary_key=True)
     conversation_id: Mapped[str] = mapped_column(StringUUID, nullable=False, primary_key=True, index=True)
     app_id: Mapped[str] = mapped_column(StringUUID, nullable=False, index=True)
-    data = mapped_column(db.Text, nullable=False)
-    created_at = mapped_column(db.DateTime, nullable=False, server_default=func.current_timestamp(), index=True)
-    updated_at = mapped_column(
+    data: Mapped[str] = mapped_column(db.Text, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        db.DateTime, nullable=False, server_default=func.current_timestamp(), index=True
+    )
+    updated_at: Mapped[datetime] = mapped_column(
         db.DateTime, nullable=False, server_default=func.current_timestamp(), onupdate=func.current_timestamp()
     )
 
@@ -829,14 +831,14 @@ class WorkflowDraftVariable(Base):
     # id is the unique identifier of a draft variable.
     id: Mapped[str] = mapped_column(StringUUID, primary_key=True, server_default=db.text("uuid_generate_v4()"))
 
-    created_at = mapped_column(
+    created_at: Mapped[datetime] = mapped_column(
         db.DateTime,
         nullable=False,
         default=_naive_utc_datetime,
         server_default=func.current_timestamp(),
     )
 
-    updated_at = mapped_column(
+    updated_at: Mapped[datetime] = mapped_column(
         db.DateTime,
         nullable=False,
         default=_naive_utc_datetime,