Psychology of Friendship What psychological constructs best model friendships, and what are some common classic and contemporary academic literature on the subject?
A few learned works on friendship:

Bell, S., &amp; Coleman, S. (Eds.). (2020). The anthropology of friendship. Routledge. ISBN 9781000320558

Berndt, T. J. (2002). Friendship quality and social development. Current directions in psychological science, 11(1), 7-10. https://doi.org/10.1111/1467-8721.00157   http://onemvweb.com/sources/sources/Friendship_Quality.pdf

Spencer, L., &amp; Pahl, R. (2006). Rethinking friendship: Hidden solidarities today. Princeton University Press. ISBN 9780691127422


Berndt (2002) observed that friendships can be classified as prized or troubled. The characteristics of which are:

Prized friendships: intimacy, loyalty, supporting, helping, sharing, praising, encouraging. and bolstering.

Troubled friendships: conflicts, dominating, and rivalry.


Berndt's analysis can be summarised visually according to the atlas of personality, emotion and behaviour (Mobbs, 2020):

Interestingly (but perhaps not surprisingly), friendship appears to closely align to the Agreeableness dimension of the Five Factor Model.
References

Mobbs AED (2020) An atlas of personality, emotion and behaviour. PLoS ONE 15(1): e0227877. https://doi.org/10.1371/journal.pone.0227877 [Post author = article author]