Event log as the canonical source of truth for agents

A post titled 'The Log is the Agent' generated a small but focused discussion about agent architecture. The core idea is that an append-only event log should be the grounding structure for any agentic system, not the context window, not an external state store. One commenter noted they independently arrived at the same design: all relevant events affecting the context window are stored in the log, and forking agents or sessions is just a matter of setting a pointer.

This is gaining traction as a design pattern because it solves several concrete problems at once: reproducibility, auditability, and the ability to branch or replay agent sessions without expensive re-execution. These are exactly the properties that make agentic systems hard to debug and deploy reliably.

The pattern is borrowed from event sourcing in distributed systems, which is not a new idea. What is new is applying it specifically to manage LLM context, where the log becomes the mechanism for deciding what the agent knows and when.