Where should the agent end and the harness begin? A Rust runtime builder's open question
sreevarshan-xenoz · reddit · 2026-10-03
A developer building an agent runtime in Rust asks how much of the "agent" should live inside the model versus the harness. The basic loop is easy, but edge cases break it: repeated tool calls, mid-command failures, oversized context, needed rollbacks, session restarts, and models claiming completion prematurely.
His current split: keep reasoning in the model, move reliability engineering into the harness — retries, context compaction, loop detection, worktree handling, approval gates, and recovery. He asks experienced agent builders what they initially put in the model and later moved to the harness, and what should stay model-driven.
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