Sampajana is observing mental object(dharma) and associated perception and feeling.and its part of all 4 foundation.
It seems there are two different types of dhamma.One is for Sampajana and other is for dhammanupassana.
So what is the dhamma in dhammanupassana and what is dhamma in sampajana.
There is a difference between Dhamma and these dhammā. Excerpt from Milinda Panha below;
“Dhammo kho, mahārāja, sabba-sukhumo, na kho, mahārāja, dhammā sabbe sukhumā, ‘sukhuman’ti vā ‘thūlan’ti vā dhammānam-etam-adhivacanaṃ.
‘Truth (Dhamma), O king, is the most minute and subtle. But this is not true of all qualities (Dhammā). Subtleness or the reverse are epithets of qualities. (I think this is Rhys Davids original pali to english)
Here is a much later translation also pali to english
"Kiṃ pana, bhante, sabbaṃ sukhuman”ti? ..." "What, revered sir, is everything that is subtle?" "Dhamma, sire, is all-subtle, but not all dhammas, sire, are subtle; this is a synonym of dhammas, sire, 'subtle' or 'coarse'."- I. B. Horner
Perhaps this is what you're getting at.
According to MahasatipatthanaSutta Pali's context, 21 meditations are meditated in four postures, iriyāpatha-pabba, for more proficiency, and the most proficient meditations are the 21 meditations in 7 sub-postures, sampajañña-pabba.
SamPajañña is the various proficient understanding of the wholesome's object in various perspective.
Saṃ prefix+pa prefix+ñā root+yu root's suffix+ṇya noun's suffix.
Saṃ prefix = sampanna = perfectly complete.
pa prefix = pakāra = many aspects, various perspective.
ñā root = understanding.
yu (na) root's suffix = making ñā to be noun.
ṇya (ññ) noun's suffix = making sampajana word to be state/condition.
Because they never memorize kayagatasatisutta pali and mahasatipatthanasutta pali. Every Pali word below is from the sutta directly and I understand it because pali has the very perfect relations in the context.
The kayagatasati pali is very clear and easy--the practitioner pajānāti of breath in sitting meditation until getting proficient level. This develops pajānāti to ñāṇa in sitting posture by the first pabba. Then the practitioner pajānāti breath in every postures by the second pabba, iriyāpatha-pabba. Then the practitioner pajānāti breath in every sub-postures by the third pabba, sampajañña-pabba. The end of all are absorbing Jhana ("Sato ca sampajāno sukhañca kāyena paṭisaṅvedeti" at the end of 21 pabba in KayagatasatiSutta).
MahasatipatthanaSutta is same but it is Vipassana, not samatha. It is the explaining Sutta of the word "Vijjā" of KāyagatāsatiSutta, VipassanāñāṇaVijjā.
Sati is keeping conscious on the wholesome's object, to avoid unwholesome. The wholesome are 21 minds and 38 mind-factors. The wholesome's objects are 4 Satipatthana or 21 pabba.
Sampajanna is the perfect understanding in various perspective of the wholesome object.
