The level of animosity over these strikes should not be exaggerated. True, they apparently came as a surprise to Pakistan. E.g. CNN says that only a week before Iran and Pakistan held joint naval exercises and had high-level meetings [in Davos].
OTOH after the exchange of strikes, both countries moved to paper over the affair. E.g.:
[Pakistani Foreign Minister Jalil Abbas] Jilani underscored "the close brotherly relations" between the two countries and expressed Islamabad's "desire" to work with Tehran "based on [the] spirit of mutual trust and cooperation," the Pakistani statement said. He "stressed that respect for territorial integrity and sovereignty must underpin this cooperation," it added.
The Iranian Embassy in Islamabad said on its official X social media platform that [Iranian FM] Amir-Abdollahian had "a very good phone talk to restore relations to a high level" and the two countries "can set a new record in de-escalation ... by returning the ambassadors to the capitals" and mutual visits of foreign ministers of Iran and Pakistan.
And consider who's been hit: both countries hit Baluch separatists, basically, just those hiding on (and possibly silently tolerated by) the other side. Who did Iran [claim to] hit: Jaish al-Adl.
WHO IS JAISH AL-ADL?
Jaish al-Adl, or the Army of Justice, surfaced in 2012. It mainly comprises members of the Sunni militant Jundullah group, which was weakened after Iran arrested most of its members.
The anti-Iranian group wants independence for Iran’s eastern Sistan and Pakistan’s southwestern Baluchistan provinces. These goals make it a common target for both governments.
And who did Pakistan claim to hit?
Pakistan said its strikes targeted members of the separatist Baluchistan Liberation Army and Baluchistan Liberation Front [...]
Yeah, these are different groups, with somewhat different ideology, but all are Baluch, basically.
As recently as December 2023, 11 Iranian police officers were killed and several injured when Jaish al-Adl militants attacked a police station in Iran’s Sistan and Balochistan province.
In 2023, a total of 10 Pakistani soldiers and security personnel were killed in three separate attacks in Balochistan carried out by militants reportedly operating from the Iranian side.
The BLA and the BLF have been accused of hitting Chinese targets [too] in Pakistan. Although China in the past called for "severe punishment" on these groups, this time they called for restraint and offered to mediate between Iran and Pakistan.