The two cooperating parties have signed the agreement.
Tips
memory
The 方 suffix turns abstract relations into 'side/party': 甲方 'Party A', 乙方 'Party B', 对方 'the other side', 合作方 'the cooperating party'. Useful in any contract context.
register
Business/legal register. In casual speech you'd say 合作伙伴 'partner' instead.
