They wouldn’t hold the phone to their ears to listen to WhatsApp messages, or put on headphones. Instead, they would disperse to far corners — around the bend from a little mosque, deep into the parking lot — with their phone in hand in front of them, like a military radio, the message playing out loud. Then, they would pace back and forth, the record button pressed as they sent a response message.

When it appeared that the Taliban negotiators and the American diplomats had finalized the deal — before Mr. Trump pulled the plug on it — an intense, often emotional, debate on the merits of the agreement erupted among the Taliban ranks, much of it over WhatsApp.

In a 17-minute audio message, one elderly Taliban ideologue voiced concern that negotiators were about to sign away the right to jihad, considered an important pillar in Islam. At times, the elder’s voice broke as he seemed on the verge of tears.

The message, ostensibly addressed to the Taliban chief negotiator, circulated far and wide in Taliban groups and beyond.

In a six-minute response — about 30 seconds of it spent on greetings like “may you not be tired, may God have you in complete health, may you have complete happiness, may Allah keep you happy with the rest of us” — another Taliban commander ripped into the elderly leader’s logic, defending the negotiators by relying on different interpretations of the same Quranic verses the Taliban leader had drawn on.