High-signal evals beat harness tweaks beat post-training: a layered agent methodology

abeirami · x · 2026-09-10

A discussion thread lays out a layered optimization framework for agent engineering: evals > harness optimization (fast learning) > model post-training (slow learning), arguing most agentic tasks never need slow learning loops. Key points: define success first and build high-SNR evals to map your agent's current frontier; use evals to attribute how much intelligence a task needs and build model routing policies to save cost; even when post-training, first get high-SNR evals, optimize the harness on that signal, then "distill" the system behavior back into weights.

Related event: Researcher Proposes Agent Capability Pyramid: Evals Over Post-Training(2 posts)→

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