diff --git a/api/app/models/multi_agent_model.py b/api/app/models/multi_agent_model.py
index bdaa0a70..985d0cb9 100644
--- a/api/app/models/multi_agent_model.py
+++ b/api/app/models/multi_agent_model.py
@@ -34,7 +34,7 @@ class MultiAgentConfig(Base):
     master_agent_id = Column(UUID(as_uuid=True), ForeignKey("app_releases.id"), nullable=True, comment="主 Agent 发布版本 ID")
     master_agent_name = Column(String(100), comment="主 Agent 名称")
 
-    default_model_config_id = Column(UUID(as_uuid=True), ForeignKey("model_configs.id"), nullable=False,server_default=str(uuid.UUID(int=0)), index=True, comment="默认模型配置ID")
+    default_model_config_id = Column(UUID(as_uuid=True), ForeignKey("model_configs.id", name="multi_agent_configs_default_model_config_id_fkey"), nullable=True, index=True, comment="默认模型配置ID")
     # 结构化配置（直接存储 JSON）
     model_parameters = Column(JSON, nullable=True, comment="模型参数配置（temperature、max_tokens等）")
     # 协作模式
diff --git a/api/migrations/versions/a6452760a140_202512261547.py b/api/migrations/versions/a6452760a140_202512261547.py
new file mode 100644
index 00000000..25e77e5e
--- /dev/null
+++ b/api/migrations/versions/a6452760a140_202512261547.py
@@ -0,0 +1,44 @@
+"""202512261547
+
+Revision ID: a6452760a140
+Revises: 5531240c344d
+Create Date: 2025-12-26 15:57:33.025049
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision: str = 'a6452760a140'
+down_revision: Union[str, None] = '5531240c344d'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('multi_agent_configs', sa.Column('default_model_config_id', sa.UUID(), nullable=True, comment='默认模型配置ID'))
+    op.add_column('multi_agent_configs', sa.Column('model_parameters', postgresql.JSON(astext_type=sa.Text()), nullable=True, comment='模型参数配置（temperature、max_tokens等）'))
+    op.alter_column('multi_agent_configs', 'master_agent_id',
+               existing_type=sa.UUID(),
+               nullable=True,
+               existing_comment='主 Agent 发布版本 ID')
+    op.create_index(op.f('ix_multi_agent_configs_default_model_config_id'), 'multi_agent_configs', ['default_model_config_id'], unique=False)
+    op.create_foreign_key('multi_agent_configs_default_model_config_id_fkey', 'multi_agent_configs', 'model_configs', ['default_model_config_id'], ['id'])
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint('multi_agent_configs_default_model_config_id_fkey', 'multi_agent_configs', type_='foreignkey')
+    op.drop_index(op.f('ix_multi_agent_configs_default_model_config_id'), table_name='multi_agent_configs')
+    op.alter_column('multi_agent_configs', 'master_agent_id',
+               existing_type=sa.UUID(),
+               nullable=False,
+               existing_comment='主 Agent 发布版本 ID')
+    op.drop_column('multi_agent_configs', 'model_parameters')
+    op.drop_column('multi_agent_configs', 'default_model_config_id')
+    # ### end Alembic commands ###