Point it at a repository on your machine. It reads every file, extracts symbols with tree-sitter, resolves imports into a call graph, ingests git history, and exposes the whole thing to Claude as precise retrieval tools.

Then you can ask the questions you actually have — "where is rate limiting handled?", "what breaks if I change this?" — and get real file paths and line numbers instead of plausible-sounding guesses.

Everything runs locally. This extension makes no network requests of any kind.

What it looks like

You: where does indexing decide a file has changed?

3 matches for "where does indexing decide a file has changed"

### src/core/services/index-repository.ts:171-186
method IndexingService.index — src/core/services/index-repository.ts:171-186
why: text match; 15 inbound references; 6 matches in this file

      const hash = contentHash(buffer);
      const previous = known.get(scanned.relPath);
      ...
      if (mode === 'incremental' && previous === hash) {
        unchanged.push(scanned.relPath);
        continue;
      }

That why: line is the point. Results are ranked by how structurally central they are — inbound references, export status, architectural role — not by how many times a word appears. A file that mentions caching loses to the one that implements it.

What you can ask

Eighteen tools in total — see docs/TOOLS.md.

Supported languages

Full symbol extraction — TypeScript · TSX · JavaScript · JSX · Python · Go · Java · Kotlin · C# · Rust · C · C++ · YAML · JSON

Text-searchable only — SQL · Markdown · Dockerfile · Terraform (grammars not yet vendored; files are indexed and searchable, but no symbols are extracted)

Anything else is still catalogued and searchable as text.

Install

From a release — download throughline.mcpb, then in Claude Desktop go to Settings → Extensions → Advanced settings → Install Extension. You'll be asked which directories the connector may read.

From source — see docs/INSTALL.md:

npm install
npm run grammars     # vendor tree-sitter WASM grammars
npm run build
npm run smoke -- .   # watch it index itself

Requires Claude Desktop on macOS or Windows. Node ships with Claude Desktop, so there's nothing else to install.

First run

1. "List my workspaces" — confirms the directory was granted.
2. "Index this project" — a 5,000-file repository takes 20–60 seconds.
3. Ask anything. Later, "refresh the index" picks up your edits in about a second.

Example prompts

• "Index this repo, then explain how authentication works. Cite files."
• "I want to rename getUserById. Show me every caller and flag the risky ones."
• "What are the entry points in this service?"
• "Draw me the dependency graph for src/billing."
• "Which files change most often and are the most complex?"
• "Draft an architecture overview — don't write it to disk yet."

How it works

A two-pass pipeline. Pass 1 parses every file with tree-sitter in parallel, with no shared state. Pass 2 has the global view and resolves names into a symbol table, import graph and call graph.

Search fuses a BM25 lexical ranker with a symbol-name ranker using reciprocal rank fusion, then re-ranks by graph centrality. RRF uses rank position only, so rankers with incomparable score scales compose without calibration — and the graph re-rank is what makes a conceptual query find the implementation rather than the twelve files that merely mention it.

The design rationale, including eleven decisions and what each traded away, is in docs/ARCHITECTURE.md.

Privacy Policy

Effective date: 2026-01-01 · Last updated: 2026-01-01

Throughline is a local desktop extension. It runs entirely on your computer as a child process of Claude Desktop.

What the connector accesses

• Files inside the directories you explicitly grant during installation. Nothing outside those directories is read. Symlinks resolving outside a granted directory are refused.
• Git metadata in those directories: commit subjects, author names and emails, timestamps, and which files each commit touched. Commit message bodies are not stored.
• Nothing else. No environment variables beyond its own configuration, no browser data, no files elsewhere on your system, no other applications.

What the connector stores, and where

An index is written to .throughline/index.db inside each project directory you granted. It contains file paths, symbol names and signatures, documentation comments, import relationships, call edges, git metadata, and excerpts of your source code used for search.

The index never leaves your machine. Deleting the .throughline directory deletes it completely. Uninstalling the extension leaves it in place; remove the directory yourself if you want it gone.

What the connector transmits

The extension makes no network requests of any kind. No telemetry, no analytics, no crash reporting, no update check, no remote API. This is structural rather than a promise: it opens no sockets, and git operations read the local object database directly rather than contacting a remote.

The boundary is worth stating plainly. When Claude calls a tool, the tool's response — code snippets, file paths, symbol names from your project — is returned to Claude and therefore processed by Anthropic under Anthropic's Privacy Policy, exactly as if you had pasted that code into a conversation yourself. The connector controls what leaves your machine only insofar as it controls what it returns; it returns scoped, bounded excerpts rather than whole repositories, and redacts secrets first. If you don't want a directory's contents reaching Claude, don't grant that directory.

Secret redaction

Before any content is stored or returned, it is scanned for credential patterns — API keys, tokens, private keys, connection strings, passwords in assignments — and matches are replaced with [REDACTED:kind]. Redaction happens at write time, so secrets are never persisted in the index either.

This is a safety net, not a guarantee. Pattern matching cannot catch every secret. Don't grant access to directories containing credentials you wouldn't want in a conversation, and use security.denyGlobs to exclude sensitive paths.

Writing to your files

Read-only by default. The single tool that can write — write_documentation — requires both that you enable writes in settings and that you confirm the specific write after seeing a preview of the exact content. It writes only inside granted directories, only to a path you name.

Data sharing, retention, and contact

No data is shared with anyone. There is no server, no account, no third party. Retention is entirely under your control: the index lives in your project directory and is deleted when you delete it. This is a developer tool not directed at children and collects no personal information from anyone.

Questions or concerns: open an issue.

The full policy, including the exact redaction patterns and the data model, is in docs/PRIVACY.md.

Security

• Read-only by default; writes are double-gated and preview-first.
• No shell execution, ever. Git is read in-process rather than by invoking git.
• Path containment is enforced against resolved real paths, so symlinks cannot escape a granted directory.
• stdout carries only JSON-RPC; all diagnostics go to stderr.
• A config file inside a repository cannot widen the connector's access — granted directories come from the install dialog and nothing else can add to them.

Threat model: docs/SECURITY.md.

Configuration

Optional. Drop a connector.config.json in your project root to tune excludes, limits and search behaviour — see connector.config.example.json and docs/CONFIGURATION.md.

Limitations

Worth knowing before you rely on it:

• References resolve by name, not by types. No type checker is involved. Edges are labelled exact or heuristic; heuristic ones can be wrong.
• Dynamic dispatch is invisible. Reflection, dependency injection, string-keyed routing and event buses produce no edges. "Dead code" findings are candidates, not verdicts.
• Blame is approximate. Line attribution is reconstructed by walking history and doesn't track code movement the way git blame -M does.
• Four languages parse as text only — SQL, Markdown, Dockerfile, Terraform.
• Large repositories are bounded, not unbounded. The default file limit is 50,000; hitting it produces a warning, not a silent truncation.

Contributing

docs/CONTRIBUTING.md. Adding a language is usually a grammar, a .scm query file and a registry row — the pipeline shouldn't need to change.

License

MIT — see LICENSE.