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Context engines

Author
Tom Rochette
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Created: / Updated: / Status: in progress / Readability: 3 / 3 minutes read (~438 words)
agents 46 context-engines 14
Table of Contents

The tools that decide what enters the context window: semantic engines, code graphs, repo packers, output filters, and local search indexes.

  • Augment Code - the coding platform whose core is a real-time semantic Context Engine feeding Auggie and Cosmos.
  • CodeAlive - the hosted context-engine API serving a code graph and hybrid retrieval to any MCP agent on metered per-action pricing, from a small London company with no independent coverage yet.
  • Context7 - Upstash’s hosted docs-injection service pulling version-specific library documentation into the prompt at question time over MCP or a CLI skill, the category’s only engine that indexes the world’s libraries instead of your repo.
  • Graft - Trail’s MIT context layer feeding agents a code graph instead of grep, 9.8k stars in fourteen weeks with every benchmark still the vendor’s own.
  • Graphify - the local AST knowledge graph exposed as a /graphify skill and MCP server, structure over similarity, no vectors.
  • Headroom - the Apache-2.0 compression layer rewriting tool outputs, logs, files, and RAG chunks before they reach the LLM, reversible through a retrieve tool, 74.6k stars in nine months.
  • Jevgrep - the MIT CLI that answers a question about a repo with files, leads, and excerpts, Jev judging relevance per query with no index at all, 2,424 stars in twelve days.
  • qmd - Tobias Lütke’s local hybrid search engine for notes, docs, and knowledge bases, BM25 plus vectors plus reranking.
  • Repomix - the MIT CLI that packs a whole repo into one AI-friendly file, retrieval-free by design.
  • rtk - the Rust CLI proxy that filters agent command output before it enters the context window.
  • Semble - the local static-embedding-plus-BM25 code search index that indexes in under a second on any CPU, snippets instead of grep-and-read.
  • Serena - the LSP-backed MCP toolkit giving agents IDE-grade symbol retrieval and editing for free, with a paid JetBrains backend, about 30k stars.
  • Sourcegraph code context platform - code search repositioned as the retrieval layer for agents, with value showing up above roughly 400K lines.
  • TOON - the MIT spec-backed Token-Oriented Object Notation that re-encodes JSON as indentation and table rows, about 1.9 million npm downloads a week, cutting the token cost of structured data in prompts.

Its members are compared on shared rows in the Context Engines Feature Matrix.

Changes
#

  • 2026-08-24 - Added Augment Code.
  • 2026-08-24 - Added Repomix.
  • 2026-08-24 - Added Sourcegraph code context platform.
  • 2026-08-30 - Added Graphify.
  • 2026-08-30 - Added qmd.
  • 2026-08-30 - Added rtk.
  • 2026-08-30 - Added Semble.
  • 2026-09-12 - Added Graft.
  • 2026-10-04 - Added Serena.
  • 2026-10-05 - Added CodeAlive.
  • 2026-10-07 - Added Jevgrep.
  • 2026-10-07 - Added Context7.
  • 2026-10-07 - Added Headroom.
  • 2026-10-07 - Added TOON.