Benchmarks Are Surprisingly Compaction-Friendly

Long-horizon agentic tasks are pushing LLM agents past their context window, so the scaffold has to compact the context, which is usually a lossy process. This repository contains the code for our paper Benchmarks Are Surprisingly Compaction-Friendly: a copy of OpenCode with extra compaction controls.

This is research code, not an official OpenCode release, and it is not affiliated with the OpenCode team.

What's in this repository

Path	Contents
packages/opencode/	OpenCode, with the compaction changes (see docs/COMPACTION.md)
agents/	Launchers used by the benchmark runners; they translate env vars into opencode.json
tools/compact/	MCP server for the compact tool strategy (the model writes its own summary, then the session is restarted)
scripts/prepare_local_opencode.sh	Builds the standalone binary
docs/diff-vs-upstream.patch	Exact diff against upstream
docs/OPENCODE.md	Auth setup and troubleshooting for the agent launchers

Everything else is upstream OpenCode, except that upstream's .github/ directory (CI workflows, templates, maintainer lists) was removed. Upstream's original README is kept in README.upstream.md, and its CONTRIBUTING.md and SECURITY.md are in docs/upstream/.

Quick start

bash scripts/prepare_local_opencode.sh
export OPENCODE_BIN=$PWD/.opencode-local/bin/opencode

Always use this binary. An opencode on your $PATH is the upstream release and silently ignores the new compaction.* keys.

Example opencode.json:

{
  "compaction": {
    "auto": true,
    "reserved": 100000,
    "prune": true,
    "clearThinking": true,
    "keepThinkingTurns": 1
  }
}

Contact

• Jeanne Salle - jeanne.salle@tue.ellis.eu

Citation

@misc{salle2026benchmarks,
  title         = {Benchmarks Are Surprisingly Compaction-Friendly},
  author        = {Salle, Jeanne and Bhatnagar, Hardik and Bethge, Matthias and Abdelnabi, Sahar and Andriushchenko, Maksym},
  year          = {2026},
  eprint        = {2610.31778},
  archivePrefix = {arXiv},
  primaryClass  = {cs.LG},
  doi           = {10.48550/arXiv.2610.31778}
}