In Jainism, we talk about five types of jñān (knowledge):

1. Mati‑jñān – sense and mind-based knowledge
2. Śruta‑jñān – knowledge from scriptures / hearing
3. Avadhi‑jñān – clairvoyant knowledge
4. Manaḥparyāya‑jñān – knowledge of others’ thoughts
5. Keval‑jñān – perfect, infinite omniscience

Regarding Tirthankar at birth:

• A Tirthankar is not born with Keval‑jñān.
• Like other highly advanced souls, at birth a Tirthankar has extremely pure mati and śruta jñān, and also janma‑labdhi avadhi‑jñān (a special inborn clairvoyant knowledge).
• Keval‑jñān comes later, after:

- taking dīkṣā (renunciation), - doing long and intense tapas (austerities), - completely destroying the knowledge‑obstructing karmas. Then the Tirthankar becomes Kevalī Bhagwān (Arihant).

Both Digambar and Śvetāmbara traditions agree on this main point: Tirthankars attain Keval‑jñān after tapas, not at the moment of birth.

You can read a simple explanation of the five jñāns here: