Biography: Imam Bukhari
Imam Bukhari did not follow any particular jurisprudential school
Qazi Abdul Rahman (Hanafi):

Statement by Qadhi Abdul Rahman Hanafi (Darul Uloom Deoband):

“Due to Imam al-Bukhari’s agreement with Imam al-Shafi‘i in certain jurisprudential matters, it might be permissible to call him Shafi‘i. Similarly, based on certain indicators, he could be called Hanbali. Since he was a student of Ishaq ibn Rahwayh, one may also refer to Imam al-Bukhari as Hanafi in orientation. Furthermore, in many issues, Imam al-Bukhari opposed Imam al-Shafi‘i and supported the Hanafis. Just as he disagreed with the Hanafis, he also disagreed with the Shafi‘is. The truth is that, considering the depth of insight found in the chapter headings (Taraajim) of Imam al-Bukhari, he cannot be considered bound to any one school of thought. He was not a follower of a specific madhhab, but rather possessed the stature of a Mujtahid himself.” [Fadl al-Bari, vol. 1, p. 64]