Eleven bards, called Bhatts, have 123 savaiyye in the Guru Granth Sahib Ji. They were Kalsahar, Jalap, Kirat, Bhikha, Sal, Bhal, Nal, Bal, Gayand, Mathura and Harbans, of a family of hereditary genealogists and panegyrists.
They came to Guru Arjan Dev Ji and stayed. Their verses praise the first five Gurus by name and are contemporary witness, composed by people who had seen Guru Ram Das Ji and Guru Arjan Dev Ji in person.
Bhatt verse is a court form, dense with Sanskritic vocabulary and formal comparison, and it sits oddly beside the plain Punjabi of the shloks. Guru Arjan Dev Ji kept it anyway.
The Bhatt Vahis, the family's own genealogical registers written in a private script, were used by twentieth-century historians as a check on Sikh chronology. Their authenticity is disputed and the debate has not closed.
They are the only contemporaries of the Gurus whose direct testimony is inside the scripture.
The Bhatts were hereditary bards who came to Guru Arjan Dev Ji at Amritsar and whose swaiyas were included in the volume. They are the only contemporary voices in it describing the Gurus.
Their compositions are praise poetry in a courtly register and they carry historical detail, including names and successions, which is why they matter as evidence rather than only as verse.
The Bhatt Vahis, ledgers kept by their descendants, record dates and events of the Guru period and were brought to notice in the twentieth century. Their reliability is argued over and they have never been fully published.