Learn to optimize your own harness, folks. You can squeeze much more performance and value from a harness. This work claims that a self-modified harness matched Codex for $4.03. Specifically, a coding agent rewrote its own harness until it solved 82.0% of Terminal-Bench 2.1 with DeepSeek V4 Flash, without any task reward during the search. The search cost was $4.03. That matches Codex, the top harness in a public nine-harness comparison run under the same settings. SelfSearch has agents…