The Log is the Agent

At Omnara, long-running agent sessions exposed a failure mode hidden by short-lived agents: the agent’s state was coupled to the process, model provider, or runtime executing it. When a worker crashed, a client disconnected, or execution moved to another machine, recovering the agent’s work became brittle.

We redesigned agent execution around an append-only session log as the source of truth. Model outputs, tool calls and results, user interventions, and other state transitions are persisted as ordered events; the live agent state becomes a replayable projection of that history.

This structural change decouples agent identity from any one model, worker, or harness. It enables crash recovery, resumability, branching, real-time observability, and migration across models and machines, but introduces difficult systems questions around ordering, idempotency, partial tool execution, checkpointing, compaction, concurrent writers, and log ownership.

This session walks through the production failures that motivated the redesign, the resulting event model and recovery path, and the tradeoffs we encountered. Using production traces and forced-failure examples, we will show what happens when a worker dies mid-tool call, how a session resumes under a different runtime, and how replay costs change as histories grow.

Attendees will leave with a practical blueprint for deciding what belongs in the durable log, what can be recomputed, and how to build agent sessions that survive process, machine, and model failure without locking continuity to a single provider.