Part 4 of Harness notes: how twelve production agents decide what the model sees.

Codex, Claude Code, Manus and Shopify keep the start of the prompt fixed so the cache hits. Then they split on what a miss costs: coding agents let the agent search for the rest, while Fin and Hebbia retrieve for recall, because a missed rule or passage reaches a customer.

My position: the harness decides what the model sees, and that decision sets most of the bill.

https://harness.psyprasad.tech/jobs/j2/

Previous launch: https://peerlist.io/psyprasad/project/all-about-harness