ohara

ohara is a local-first context lineage engine that indexes a git repo’s commits, diffs, and source symbols and serves them to AI coding assistants through the Model Context Protocol (MCP).

Where Grep answers “where is this code?”, ohara answers two complementary questions about the history of the code:

• find_pattern — “how was X done before?” Returns historical commits whose diffs resemble a natural-language query, ranked by a three-lane retrieval pipeline (vector + BM25 hunk-text + BM25 symbol-name) → Reciprocal Rank Fusion → cross-encoder rerank → recency tie-break.
• explain_change — “why does THIS code look the way it does?” Given a file + line range, returns the commits that introduced and shaped those lines, ordered newest-first. Deterministic — backed by git blame, not embeddings.

Design principles

• Local-first. All indexing, embedding, and retrieval happens on your machine. No cloud calls. The SQLite-based index lives under $OHARA_HOME/<repo-id>/index.sqlite.
• Stays out of the way. A post-commit hook (installed by ohara init) keeps the index fresh; the --incremental fast path makes that essentially free.
• Idempotent and abort-safe. Killed mid-index? Resume re-does at most ~100 commits.
• Single static binary by default. By default ohara is local-first single-process; an opt-in ohara serve daemon is available for warm-cache workflows. Indexing is still always foreground. Distributed via cargo-dist for macOS and Linux (Windows users: WSL).

Where to go next

• Install — curl | sh install or build from source.
• Quickstart — index a repo and run your first query.
• Wiring into MCP clients — point Claude Code, Cursor, Codex, OpenCode, or any MCP-aware client at the server.
• Architecture overview — for contributors and the curious.

Status

Released versions: v0.1 (foundation + find_pattern) → v0.2 (auto-freshness) → v0.3 (retrieval pipeline upgrade) → v0.4 (Java + Kotlin support) → v0.5 (explain_change tool) → v0.5.1 (progress bar + abort-resume + self-update) → v0.6 (indexing throughput prep) → v0.7.0–v0.7.5 (evals, perf tracing, memory-efficient indexing, ohara serve daemon + multi-repo). Current: v0.7.5. See the Roadmap.