CliffCompaction: up to 50% cheaper long-horizon coding agents

CMU’s CliffCompaction (arXiv 2609.26779) is a drop-in autocompactor that truncates tool I/O instead of summarizing, never rephrases, and discards prior compactions blocks so drift doesn’t stack—cutting cost up to ~50% on Terminal-Bench while matching or beating full-context runs. An open-source API-proxy works with Claude Code, Codex, and other harnesses; with parallel rollouts, compacted Kimi K2.6 matches Opus 4.7 for less than one GPT-5.3 Codex run.