I read up on B. Analayo's Agama comparative notes between the passage in question in various EBT schools (pali, more than one agama lineage, sanskrit...).
But he didn't have the part I'm interested in. He talks about how one recension talks about Buddha as a boy experiencing all 4 jhanas instead of just first jhana for example.
Does anyone have quote and references for the passages in question?
In the pali version, all it says is while his father was working, buddha sat down in the cool shade of a tree and spontaneously entered first jhana.
I'm especially interested in one of the Agamas, which says the same thing, but adds that right before he entered jhana, he had been observing the dukkha of watching earthworms getting eaten by birds.