Have been working on an interesting text by Sakya Pandita on the history of Cakrasamvara.
According to this history, the first human being to receive Cakrasamvara was Saraha I, the teacher of the tantric siddha, Nāgārjuna. In terms of when Saraha lived, he does not really say, apart from asserting that Saraha is present at Shri Parvata (Sri Sailam in modern India) in Andhra Pradesha as a sambhogakāya.
Luhipa was the disciple of Saraha II aka Shavaripa. Sapan definitely situates him during the reign of the famed Buddhist king of Bengal, Shri Dharmapala, whose reign extended circa 775 to 810 CE.
Luihipa was a scribe in the court of Dharmapāla until he met Savaripa. We do not know when Luhipa was active during this 35 year period, but since his retreat was 9-12 years, and since legend holds that Dharmapāla became a disciple of Luhipa, we assume a later date for Luhipa and put his encounter with Dharmapāla around 810. Supposedly Dharmapāla left his kingdom and took a job as a pounder of rice in what is now known as Orrisa becoming known as the siddha Demgipa.
From Demgipa on, a significant feature of Cakrasamvara practice is the requirement that high cast practitioners take low caste occupations under low cast woman.
In any event, we have a fairly firm range to date the Cakrasamvara tantra from -- given this we can presume that the Cakrasamvara must date to the early 8th century CE. Since it mentions the Guhyasamaja and a number of other tantras, we can date those, as well as Saraha I, the first Siddha, to the late 7th century CE.
Also Situ Panchen asserts that Lohipa revealed the Yoginisamcarya tantra, which details the process of the sadhana practice.
This has a happy consequence for the Mahamudra text in the Vima Nyinthig which mentions Saraha by name.