Headroom ships context compression with the accuracy deltas attached.

62,876 stars, ~313/day. Compresses tool outputs, logs, RAG chunks and files before they hit the model, and unusually publishes the other side of the trade: GSM8K holds at 0.870 (±0.000), TruthfulQA improves 0.530 → 0.560, SQuAD v2 and BFCL retain 97%. Real workloads: 92% savings on code search (17,765 → 1,408 tokens), 92% on SRE debugging, 73% on GitHub issue triage. Three-stage pipeline routes by content type into SmartCrusher (JSON), an AST-aware CodeCompressor covering eight languages, or a trained Kompress-v2-base for prose. The detail that shows they've actually run this in production: a CacheAligner deliberately preserves provider KV-cache prefixes so compression doesn't destroy prompt caching. Library, proxy (headroom proxy --port 8787) or MCP server. (GitHub)