Practical AI: ZenML's Hamza Tahir Announces 'Kitaru,' an Open-Source Replayable Runtime for Durable Agents

Practical AI·medium signal

Practical AI's 'Building Durable AI Agents' (July 7, 2026) features ZenML co-founder Hamza Tahir, who frames an agent as 'just a while loop that talks to a model, calls a tool, and writes to a filesystem' and announces Kitaru — a new open-source replayable runtime that sits under your existing agent stack and records every step as a checkpoint, so failed or error-prone runs resume from the last saved step instead of restarting. He distinguishes inner vs. outer agent harnesses and what durable execution actually guarantees for running agent fleets in production. For builders: treat agents as durable, checkpointable, replayable workflows rather than fragile scripts, and invest in the harness as much as the model.