… you have a couple of untruths in your documentation. There is no parity between a filidh and a seanachie. A filidh was a recognized rank of bard who had already been at school for several years, learning the lineage of the kings and the stories of the settlement. Bard (entry level), filidh (journeyman), and ollamh (master) are all ranks defined within Brehon Law, which I strongly suggest you look up. Brehon Law was in force, with a few hiccups, for most of our period. Seanachie is rarely an official position, and never a trained one; the problem with calling yourself a seanachie and trying to support Tain Bo is that a seanachie would likely tell stories about his neighbors, not the gods and demigods of Old Eire. Tain Bo, in all its versions, retains the marks of having been written, not developed in a casual oral style, as evidenced by the verse passages of dialogue.
Adelaide de Beaumont

link removed because documentation had many errors and I don’t want anyone building on it.

The Tain Bo Coulgne is an Irish Epic Tale that was written down in the 12th century in several different places. Where did it come from?  From the Book of Leinster we have the “Recovery of the Tain” which tells us that Senchan Torpeist summoned the poets of Ireland and he asked them if they knew the entirety of the story. However, none of them did- they only knew episodes. So he asked whom among them would go ask a ghost for the whole of the story. 

Read the PDF above for more how it turned out.