The Bahir is the earliest text usually counted as kabbalistic. It surfaces in Provence in the second half of the twelfth century, is quoted in Languedoc and Catalonia from around 1200, and is built as a loose sequence of exegetical fragments rather than as a treatise. It opens with a saying introduced in the name of Rabbi Nehunya ben HaKanah, and the tradition took the whole book from that opening, calling it the Sefer ha-Bahir of Rabbi Nehunya ben HaKanah.
The ascription does not survive examination. The book's language, its literary form and the questions it works on belong to the medieval world rather than to the first century, and no ancient source knows of it. Gershom Scholem, whose Origins of the Kabbalah remains the fullest study, read it as an edited compilation drawing on older material of eastern origin that reached Provence in a form nobody can now reconstruct. What stays genuinely open is what that older material was and by what route it travelled, and that is a different question from the question of authorship.
Placing a book in the mouth of an early authority is a normal move in Jewish literature rather than a forgery. It states where the writer believes the teaching belongs. Reading it as a claim about whose hand held the pen is a modern error, and it is why the atlas keeps the attribution visible and marks it disputed instead of quietly deleting it.