Is the pabhassara citta in early Buddhism same as puruṣa/ātman in Sāṃkhya–Yoga? If yes Does this imply nibbana and kaivalya are the same state?

A recurring claim that frequently keeps being brought up both in popular discussions and some academic writings is that early Buddhism is simply a reformulation of ideas already present in Sāṃkhya–Yoga, especially around a kind of “pure” or “luminous” consciousness. In certain suttas like Pabhassara Sutta (AN 1.49–52), the Buddha famously states: “Luminous, monks, is the mind, and it is defiled by incoming defilements.Luminous, monks, is the mind. And it is freed from incoming defilements.” This has often been interpreted as pointing to a kind of underlying “pure” or “radiant” consciousness that is only adventitiously obscured. To reinforce this idea some point to “luminous” or “radiant” consciousness described as “invisible, infinite, luminous all around” in texts like DN 11 / MN 49 (often interpreted as viññāṇaṃ anidassanaṃ) Likewise as per the systems of Sāṃkhya–Yoga, atman or puruṣa is defined as pure witness-consciousness—“absolute, independent…non-attributive consciousness,” neither produced nor producing anything. Liberation (kaivalya) in the system precisely the isolation of this pure consciousness from the defilements of the gunas of prakṛti, leaving it in its own nature as independent awareness.In the Yoga Sutras, the entire trajectory of practice culminates in this separation, where consciousness stands alone in its own nature (kaivalya as the end of misidentification with mental modifications). Given these parallels, one often sees the argument framed more or less like this: Buddhism’s luminous mind = a defilement-free awareness; Sāṃkhya’s puruṣa = pure witnessing awareness; therefore nibbāna (cessation of defilements) and kaivalya (isolation of puruṣa) might be functionally describing the same realization in different conceptual vocabularies. Adding to this, it’s often pointed out that the Buddha studied under Āḷāra Kālāma, who is associated with pre-Buddhist meditative traditions that overlap with early Sāṃkhya ideas. This leads to the broader claim that Buddhism might be a reformulation of an already pre-existing Sāṃkhya-style framework. So the question is how seriously should these structural similarities be taken? When some equate pabhassara citta with puruṣa and nibbāna with kaivalya, are they picking up on a genuine doctrinal overlap, or are they collapsing fundamentally different metaphysical frameworks? And more specifically, does the early Buddhist notion of a “luminous mind” actually support anything like an eternal or underlying consciousness comparable to Sāṃkhya’s puruṣa?