Lore MCP Server

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Lore

     

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The teammate that knows it all

Lore holds the structural knowledge over the codebase in memory so your agent doesn't have to. Lore indexes your code into a structured knowledge base that agents query through MCP. It fully maps symbols, imports, call relationships, type relationships, annotations, docs, and all git data — with optional embeddings for semantic search — so agents can reason about your codebase without re-reading it from scratch.

Lore-enabled agents achieve up to +10pp higher correctness, up to 84% fewer tokens, and up to 62% faster wall-clock time compared to a baseline agent with grep and file reads alone. See the full benchmark results for details.

What Lore does

• Indexes source files using SCIP-first indexing with LSP enrichment for pre-resolved symbols and edges
• Extracts symbols, imports, call refs, type refs, and annotations across all 23 supported languages
• Resolves internal vs external imports and builds call/import/module/inheritance/type-dependency graph edges using a 3-tier resolution strategy (SCIP/LSP containment, same-file name match, unique name match)
• Discovers and indexes documentation (.md, .rst, .adoc, .txt) with inferred kinds/titles
• Stores everything in a normalized SQL schema with optional vector search
• Enables RAG-style retrieval with semantic/fused search across symbols and doc sections
• Indexes git history (commits, touched files, refs/branches/tags)
• Enriches symbols with resolved type signatures and definitions via optional index-time LSP integration (batch-pipelined hover + definition requests)
• Supports line-level git blame through MCP
• Supports automatic refresh via watch mode, poll mode, and git hooks

How Lore integrates with LLMs

flowchart LR
    subgraph Codebase
        SRC[Source Files]
        GIT[Git Repo]
    end

    subgraph INDEXER[Lore Indexer]
        SCIPDIRECT[SCIP Source<br/>pre-resolved symbols + refs] --> WALK
        WALK[Walker] --> PARSE[Parser] --> EXTRACT[Extractors<br/>symbols · imports · call refs<br/>type refs · annotations]
        EXTRACT --> RESOLVE[Import Resolver<br/>internal ↔ external]
        EXTRACT --> CALLGRAPH[Relationship Resolver]
        EXTRACT -.-> LSPENRICH[LSP Enrichment<br/>type signatures · definition locations]
        GITHIST[Git History Ingest<br/>commits · diffs · refs]
    end

    SRC --> SCIPDIRECT
    SRC --> WALK
    GIT --> GITHIST

    DB[(SQL DB)]
    EMBED([Embedding Model])

    subgraph MCP_SERVER[MCP Server]
        LOOKUP[lore_lookup]
        SEARCH[lore_search]
        GRAPH[lore_graph]
        DEPENDENTS[lore_dependents]
        TRACE[lore_trace]
        DIFF[lore_diff]
        COHESION[lore_cohesion]
        STRUCTURE[lore_structure]
        SNIPPET[lore_snippet]
        BLAME[lore_blame]
        HISTORY[lore_history]
        METRICS[lore_metrics]
    end

    subgraph MCP_CLIENTS[MCP Clients — Agents]
        CLAUDE_CODE[Claude Code / Desktop]
        COPILOT[VS Code + Copilot]
        CURSOR[Cursor]
        CUSTOM[Custom Agent Frameworks]
        CLAUDE_CODE ~~~ COPILOT ~~~ CURSOR ~~~ CUSTOM
    end

    GITHIST --> DB

    RESOLVE & CALLGRAPH --> DB
    LSPENRICH -.->|optional| DB
    RESOLVE -.->|optional| EMBED
    EMBED -.-> DB

    DB --- LOOKUP & SEARCH & GRAPH & DEPENDENTS & TRACE & DIFF & COHESION & STRUCTURE & SNIPPET & BLAME & HISTORY & METRICS
    EMBED <-.->|semantic/fused| SEARCH

    LOOKUP & SEARCH & GRAPH & DEPENDENTS & TRACE & DIFF & COHESION & STRUCTURE & SNIPPET & BLAME & HISTORY & METRICS <--> MCP_CLIENTS

Lore sits between your codebase and any LLM-powered tool. The indexer uses SCIP-first indexing with LSP enrichment to extract symbols, imports, and relationships, then persists everything to a normalized SQL database. The MCP server auto-discovers tool modules and exposes the database to any MCP-compatible client. The index stays fresh via git hooks, watch mode, or poll mode — each refresh only re-processes files whose content hash has changed.

See docs/architecture.md for the full schema and pipeline breakdown.

Supported languages

Lore currently supports extractors for:

• C, C++, C#
• Rust, Go, Java, Kotlin, Scala, Swift, Objective-C, Zig
• Python, JavaScript, TypeScript, PHP, Ruby, Lua, Bash, Elixir
• OCaml, Haskell, Julia, Elm

Install

npm install @jafreck/lore

Note: Lore uses native add-ons (better-sqlite3). A working C/C++ toolchain is required the first time dependencies are built.

Quick start (CLI)

# 1) Build an index
npx @jafreck/lore index --root ./my-project --db ./lore.db

# 2) Start MCP server over stdio
npx @jafreck/lore mcp --db ./lore.db

Quick start (programmatic)

import { IndexBuilder } from '@jafreck/lore';

const builder = new IndexBuilder(
  './lore.db',
  { rootDir: './my-project' },
  undefined,
  { history: true },
);

await builder.build();

MCP tools

| Tool | Purpose | |------|----------| | lore_lookup | Find symbols by name or files by path, including external dependency API symbols and LSP-resolved metadata when available | | lore_search | Structural BM25, semantic vector, or fused RRF search across symbols and doc sections | | lore_dependents | Find everything affected by changing a symbol or file — callers, importers, subclasses, and type references with automatic transitive traversal (up to 5 hops) in one call | | lore_trace | Trace an execution path from an entry point and return an ordered call sequence with source code for each step | | lore_diff | Compare exported symbols between two indexed branches; returns added, removed, and changed symbols | | lore_cohesion | Rank directories by module cohesion (ratio of internal to external symbol references) | | lore_structure | Detect structural anomalies — import cycles (Tarjan SCC), layering violations (Kahn toposort), and outlier couplings | | lore_graph | Query call/import/inheritance/type-dependency edges with automatic transitive traversal (up to 5 hops); supports source_id for outbound and target_id for inbound/reverse queries; materializes virtual dispatch edges for polymorphic call resolution | | lore_snippet | Return snippets from indexed source snapshots by file path + line range or by symbol name; path/symbol resolution is branch-aware and responses include containing-symbol context metadata (name, kind, start/end lines) when available | | lore_blame | Query blame, line-range history, or ownership aggregates with optional symbol targeting, commit-context enrichment, and risk signals | | lore_history | Query commit history by file, commit, author, ref, recency, or semantic commit-message similarity | | lore_metrics | Aggregate index metrics |

lore_lookup query options

For symbol lookups (kind: "symbol"), lore_lookup supports:

• match_mode: optional symbol-name matching mode (exact, prefix, contains); defaults to exact (case-insensitive).
• symbol_kind: optional symbol kind filter (for example, function or class).
• path_prefix: optional indexed file-path prefix filter.
• language: optional indexed file language filter.
• limit: optional maximum rows for empty/browse symbol queries (default 20).
• offset: optional rows to skip for empty/browse symbol queries (default 0).

Example symbol lookup requests:

{ "kind": "symbol", "query": "IndexBuilder", "match_mode": "prefix", "symbol_kind": "class" }
{ "kind": "symbol", "query": "", "path_prefix": "src/indexer/", "language": "typescript", "limit": 20, "offset": 20 }

MCP config example

{
  "mcpServers": {
    "lore": {
      "command": "npx",
      "args": ["@jafreck/lore", "mcp", "--db", "/path/to/lore.db"]
    }
  }
}

lore_search filter parameters

lore_search supports additional optional filters to narrow symbol hits:

| Parameter | Applies to | Description | |-----------|------------|-------------| | path_prefix | Symbol results | Restrict symbol hits to files whose source path starts with the prefix | | language | Symbol results | Restrict symbol hits to indexed file language (for example typescript, python) | | kind | Symbol results | Restrict symbol hits to a symbol kind (for example function, class) |

Mode behavior:

• structural: returns symbol hits only; applies path_prefix, language, and kind.
• fused: combines structural and semantic candidates; symbol filters apply to symbol candidates and doc filters apply to semantic doc-section candidates before final fused ranking.

lore_history modes

| Mode | Query | |------|-------| | recent | Newest commits | | semantic | Conceptual commit-message search (falls back to recent when vectors are unavailable) | | file | Commits that touched a path | | commit | Full/prefix SHA lookup (+files +refs) | | author | Commits by author/email substring | | ref | Commits matching branch/tag ref name |

lore_blame examples

{ "path": "/repo/src/index.ts", "line": 120 }
{ "path": "/repo/src/index.ts", "start_line": 120, "end_line": 140 }
{ "path": "/repo/src/index.ts", "line": 120, "ref": "main" }
{ "symbol": "handleAuth", "path": "/repo/src/auth.ts", "branch": "main" }
{ "mode": "history", "symbol": "handleAuth", "path": "/repo/src/auth.ts", "ref": "main" }
{ "mode": "ownership", "path": "/repo/src", "scope": "directory", "ref": "main" }

Legacy line and line-range requests remain fully supported; mode defaults to "blame" when omitted. History and ownership responses include commit context (commits, history[*].commit_context with message/files/refs) and risk indicators (recency, author_dispersion, churn, overall), and symbol-targeted requests return resolved_symbol.

Data ingestion

Lore indexes multiple data sources into a normalized SQLite schema. Each source has its own ingestion pipeline and can be enabled independently.

Source code

The indexer uses SCIP-first indexing with LSP enrichment: SCIP indexers produce symbols and pre-resolved edges directly, and LSP enrichment augments symbols with resolved type signatures and definitions. The import resolver classifies each import as internal or external, and a call-graph builder creates edges between symbols.

Programmatic example:

import { IndexBuilder } from '@jafreck/lore';

await new IndexBuilder('./lore.db', {
  rootDir: './my-project',
  includeGlobs: ['src/**'],
  excludeGlobs: ['**/*.gen.ts'],
  extensions: ['.ts', '.tsx'],
}).build();

Git history

Lore ingests commits, touched files (with change type and diff stats), and refs (branches/tags). Enable with --history; use --history-all to traverse all refs and --history-depth <n> to cap the number of commits.

Indexed tables:

• commits — sha, author, author_email, timestamp, message, parents
• commit_files — per-commit touched paths with change type and diff stats
• commit_refs — refs currently pointing at commits (branch/tag/other)
• commit_embeddings — commit-message vectors keyed to commits for semantic history retrieval

Programmatic example:

await new IndexBuilder('./lore.db', {
  rootDir: './my-project',
}, undefined, {
  history: { all: true, depth: 2000 },
}).build();

Embeddings

Lore optionally generates dense vector embeddings for semantic search using @huggingface/transformers (Transformers.js), which runs ONNX models natively in Node.js — no Python or external processes required. The default model is Qwen/Qwen3-Embedding-0.6B (1024-dim); override with --embedding-model:

npx @jafreck/lore index --root ./my-project --db ./lore.db \
  --embedding-model 'nomic-ai/nomic-embed-text-v1.5'

Hardware acceleration is automatic: CoreML on Apple Silicon, WebGPU when available, CPU elsewhere. Override via the LORE_EMBED_DEVICE env var. Quantized ONNX dtype (fp32/fp16/q8/q4) is configurable with LORE_EMBED_DTYPE. In update/watch/poll mode, symbols and docs whose embedding text is unchanged (SHA-256 hash comparison) are skipped entirely for fast incremental re-embeds.

At query time, lore_search in semantic or fused mode embeds the query and performs cosine similarity against stored vectors. If the model cannot initialize, search gracefully degrades to structural BM25. When history indexing is enabled, Lore also stores commit-message vectors in commit_embeddings so lore_history can serve semantic commit retrieval.

LSP enrichment

Lore can enrich symbols and call refs with resolved type metadata at index time by querying language servers via the Language Server Protocol. Enriched columns:

• resolved_type_signature, resolved_return_type
• definition_uri, definition_path

These are persisted in symbols, symbol_refs, and external_symbols tables. lore_lookup and lore_search return them when present. Query handlers stay SQLite-only — language servers are never invoked at runtime.

LSP precedence:

1. CLI flag (--lsp)
2. .lore.config lsp.enabled
3. Built-in default (false)

.lore.config example:

{
  "lsp": {
    "enabled": true,
    "timeoutMs": 5000,
    "servers": {
      "typescript": { "command": "typescript-language-server", "args": ["--stdio"] },
      "python": { "command": "pyright-langserver", "args": ["--stdio"] }
    }
  }
}

Default server mappings cover all supported extractor languages:

| Language(s) | Default command | |-------------|------------------| | c, cpp, objc | clangd | | rust | rust-analyzer | | python | pyright-langserver --stdio | | typescript, javascript | typescript-language-server --stdio | | go | gopls | | java | jdtls | | csharp | csharp-ls | | ruby | solargraph stdio | | php | intelephense --stdio | | swift | sourcekit-lsp | | kotlin | kotlin-language-server | | scala | metals | | lua | lua-language-server | | bash | bash-language-server start | | elixir | elixir-ls | | zig | zls | | ocaml | ocamllsp | | haskell | haskell-language-server-wrapper --lsp | | julia | julia --startup-file=no --history-file=no --quiet --eval "using LanguageServer, SymbolServer; runserver()" | | elm | elm-language-server |

Install whichever language servers you need on PATH; unavailable servers are auto-detected and skipped without failing indexing.

Dependency APIs

Lore can index declaration-level public API surface from direct dependencies. Enable with --index-deps or indexDependencies: true programmatically.

Supported ecosystems:

• TypeScript/JavaScript — exported declarations from .d.ts files in direct npm dependencies
• Python — stubbed/public declarations from direct dependencies via .pyi and py.typed
• Go — exported declarations from direct module requirements in go.mod
• Rust — pub declarations from crates in Cargo.toml

Implementation bodies are excluded and transitive dependencies are not crawled.

Keeping the index fresh

The index stays current automatically through three mechanisms:

Git hooks — install once with lore hooks, and Lore refreshes on every post-commit, post-merge, post-checkout, and post-rewrite:

npx @jafreck/lore hooks --root ./my-project --db ./lore.db --history

Watch mode — reacts to filesystem events in real time:

npx @jafreck/lore refresh --db ./lore.db --root ./my-project --watch

Poll mode — periodic mtime diffing, most reliable across filesystems:

npx @jafreck/lore refresh --db ./lore.db --root ./my-project --poll

Both watch and poll modes support live embeddings — when an embedding model is configured, changed files have their vectors re-generated incrementally during each refresh cycle.

Each refresh only re-processes files whose content hash has changed, so updates are fast even on large repositories.

CLI reference

lore index

Build or update a knowledge base.

npx @jafreck/lore index --root <dir> --db <path> [--embedding-model <id>] [--blocking-embedder] [--index-deps] [--history] [--history-depth <n>] [--history-all] [--include <glob>] [--exclude <glob>] [--language <lang>] [--lsp] [--no-scip]

lore refresh

Incremental refresh (one-shot, watch, or poll).

npx @jafreck/lore refresh --db <path> --root <dir> [--index-deps] [--history] [--history-depth <n>] [--history-all] [--lsp] [--no-scip]
npx @jafreck/lore refresh --db <path> --root <dir> --watch [--index-deps] [--history] [--lsp] [--no-scip]
npx @jafreck/lore refresh --db <path> --root <dir> --poll [--index-deps] [--history] [--lsp] [--no-scip]

lore hooks

Install repo-local git hooks for automatic refresh.

npx @jafreck/lore hooks --root <repo> --db <path> [--history] [--lsp] [--no-scip]

lore mcp

Start the MCP server over stdio. When --root is given and no database exists yet, Lore auto-indexes before starting.

npx @jafreck/lore mcp --root <dir> [--watch|--poll]
npx @jafreck/lore mcp --db <path> [--root <dir> --watch|--poll] [--blocking-embedder]

Build from source

git clone https://github.com/jafreck/Lore.git
cd Lore
npm install
npm run build

Contributing

Environment expectations:

• Node.js >=22.0.0
• Native build toolchain for better-sqlite3

Common local workflow:

npm run build
npm test
npm run coverage

CI currently enforces minimum coverage thresholds of 77% statements, 64% branches, 80% functions, and 79% lines.