Harness Swap Lifts Same Model from 46.7% to 66.7% Success
In a Composio benchmark, DeepSeek V4 Flash running across 8 agent harnesses passed 20 of 30 hard tasks with Pi (66.7%), while Claude Code, Codex, and Deep Agents each passed 16. Pi's cost per successful task was $0.028, about 1/7 of Claude Code's $0.195. Community numbers show Pi and DeepSeek hitting 99.93% cache hits, processing nearly 1B input tokens for just $2.65 instead of an estimated $132. The article explains DeepSeek's prefix cache: matches must start from the first token, so harnesses must keep the prompt head stable. Reasonix and pi-deepseek-cache demonstrate concrete tactics: frozen environment summaries at startup, append-only context, separate sessions for executor and planner, and hash-cached deterministic summaries, cutting input token prices by 98-99%. Useful for engineers choosing agent harnesses or optimizing LLM API spend.