A repository-aware AI coding assistant for macOS, Windows and Linux.
Synapse indexes a Git repository into a persistent knowledge graph with vector embeddings, then grounds every answer in that index with citations that open the exact source location. Around that sits a full workspace: a permission-gated agent, an integrated terminal, a browser preview pane, background tasks, scheduled jobs, GitHub pull request and CI monitoring, and a document and vision pipeline for PDFs, DOCX files and images.
Free to use. The source code is not public. Synapse costs nothing, has no trial, no licence key and no account. This repository distributes the application itself; the code behind it stays private. You bring your own AI provider keys, or run a model locally, and you pay whichever provider you chose, never this project.
Download the latest release · Read the User Manual
- What it does
- Download
- Installing
- Getting started
- User manual
- Bring your own models
- Privacy
- Requirements
- Support
- Licence
Answers grounded in your code. Ask a question about a repository and the answer cites the files it came from. Every [^N] footnote opens that exact location in an embedded editor. Generated code can be checked against the index, which flags symbols that do not exist in your codebase.
An agent you can actually restrain. File edits and shell commands run under a per-session permission mode: read-only planning, edits with approval, or fully automatic. A destructive-command deny list is enforced in every mode, including the most permissive one, and the agent cannot reach outside the working directory you gave it.
Any model you want. Eleven providers are built in (OpenAI, Anthropic, DeepSeek, GLM, Kimi, MiniMax, Qwen, Meta, Gemini, Grok and local Ollama), and any other OpenAI-compatible or Anthropic-compatible endpoint can be added from Settings without waiting for an update. Fallback chains fail over automatically when a provider rate-limits you.
A real workspace, not just a chat box. An integrated terminal, a browser preview pane that runs your dev server with working hot reload, background tasks and subagents, cron-scheduled jobs, and pull request and CI monitoring.
Your working copy is yours. Each conversation edits its own copy of the repository, so two conversations never overwrite each other and nothing reaches the folder open in your editor until you press a button. What it changed is listed above the file tree; applying it puts the changes in as ordinary uncommitted work for you to review and commit. If that would clash with edits you made yourself, it stops and tells you rather than writing conflict markers into your files.
It checks its own work. When the assistant changes files, your project's tests run before its answer is accepted, and a failure goes back to it to fix. It says what it is running and what happened, stops after two attempts rather than thrashing, and tells you plainly if the tests still fail instead of quietly calling the job done. Projects with no test suite are left alone.
It tells you what a change touches. When the assistant edits a file, the transcript says which other files depend on it, and flags the ones with no test beside them. That comes from a resolved call graph rather than a text search, so it finds callers that searching for the file name would miss.
Documents and images. Attach PDFs, DOCX files, images or plain text. Digital PDFs are read directly, and scanned pages and images are read by a vision model of your choosing. The extracted text is yours to inspect and edit before it is used.
It updates itself. New releases are downloaded in the background and installed when you press a single button in the sidebar. Your conversations, settings and API keys live outside the application and are never touched by an update. See Keeping Synapse up to date.
Every release publishes a build for each platform on the releases page.
| Platform | File | Notes |
|---|---|---|
| macOS, Apple Silicon | synapse-macos-arm64.app.zip |
M1 and newer |
| macOS, Intel | synapse-macos-amd64.app.zip |
|
| Windows | synapse-windows.zip |
x64 |
| Linux | synapse-linux-amd64.tar.gz |
x64, needs WebKit2GTK (see below) |
Each release also carries SHA256SUMS.txt. To check a download before opening it:
shasum -a 256 -c SHA256SUMS.txt --ignore-missingOn Windows:
Get-FileHash .\synapse-windows.zip -Algorithm SHA256Read this first if you are on macOS or Windows. Synapse is not code-signed. Signing requires paid certificates from Apple and a certificate authority, and this is a free project that asks you for nothing, so those have not been bought. Your operating system will therefore object the first time you open it, and there is one extra step to get past that. It is described below for each platform, it is a one-time step, and the download itself is fine. Verify the checksum if you want to be certain of that before you start.
-
Unzip the download and drag
synapse.appinto/Applications. -
Remove the quarantine flag, by pasting this into Terminal:
xattr -dr com.apple.quarantine /Applications/synapse.app
-
Open it.
You only do this once. Synapse updates itself from then on, and an update it downloaded itself does not carry the flag that step 2 removes.
Why step 2 is needed. macOS attaches a quarantine flag to everything downloaded from the
internet. For an app without a Developer ID signature it then refuses to open it, and reports
"synapse" is damaged and can't be opened. You should move it to the Trash. The app is not damaged
and there is nothing wrong with your download. That is simply the message macOS gives for a missing
signature, and it is the same message whatever the real cause, which is why it is worth knowing what
it actually means.
The command removes that flag from this one app. It changes nothing else on your system, and it does not disable any protection for anything you download in future.
If you would rather not run a command, you can instead try to open the app, then go to System Settings > Privacy & Security, scroll down, and press Open Anyway next to the message about Synapse. This route does not work on every macOS version for an unsigned app, whereas the command above always does.
- Unzip the download.
- Run
synapse.exe. - SmartScreen will warn that the publisher is unknown. Choose More info, then Run anyway.
Step 3 happens because the executable is not code-signed. As on macOS, this is about a missing
certificate rather than anything detected in the file. Check the SHA256 against SHA256SUMS.txt
first if you want independent confirmation of what you downloaded.
Windows also requires WebView2, which is preinstalled on Windows 10 and 11. On an older or stripped install, get it from Microsoft's WebView2 runtime page.
Synapse needs WebKit2GTK at runtime.
# Debian and Ubuntu
sudo apt install libwebkit2gtk-4.1-0 libgtk-3-0
# Fedora
sudo dnf install webkit2gtk4.1 gtk3
# Arch
sudo pacman -S webkit2gtk-4.1 gtk3Linux has no code-signing requirement, so there is no extra step here. Extract and run:
tar -xzf synapse-linux-amd64.tar.gz
chmod +x synapse
./synapse- Add a model. Open Settings, expand a provider, paste an API key and click
SAVE_VERIFY. The key is stored in your operating system's keychain, and the verify step confirms it works by fetching the provider's model list. Ollama needs no key: just have it running locally. - Index a repository. Switch to WIKI in the sidebar, click
+, and either clone a repository by URL or index one already on your disk. A repository indexed in place is never copied or moved. Choose an embedding model when prompted, and stay with it: changing it later requires a full re-index. - Ask something. Answers cite the code they came from. Click a citation to open the source.
- Let it work. Pick a permission mode for the session, then ask for a change rather than a description. Start in plan mode if you want to see the approach before anything is written.
The User Manual walks through every screen in the application with screenshots, from connecting a model to the parts most people never find. Troubleshooting covers the problems people hit first.
Synapse has no hosted service and no account. It talks directly to whichever providers you configure, with your own API keys, and it can point at anything that speaks the OpenAI or Anthropic protocol: a self-hosted gateway, a router such as OpenRouter, a corporate proxy, or a local server.
Running entirely on Ollama is a supported configuration. In that setup the application makes no network calls at all.
- Your code is indexed locally, into a database stored beside the repository. It is never uploaded anywhere.
- API keys go to your operating system's keychain, not to a configuration file and not to the application's database.
- The only outbound traffic is to the providers you configure, plus an update check against the GitHub releases API that you can see in the status bar. Updates are never installed automatically.
- There is no telemetry. No usage analytics, no crash reporting, no account.
| Minimum | |
|---|---|
| macOS | 11 Big Sur or newer, Apple Silicon or Intel |
| Windows | Windows 10 or 11, x64, with the WebView2 runtime |
| Linux | A distribution with WebKit2GTK 4.1 and GTK 3, x64 |
| Memory | 4 GB, though indexing a large repository benefits from more |
| Network | Required for hosted models, not required when running on local Ollama |
Optional, for specific panes: git for repository features, the
GitHub CLI (gh) for the pull request and CI pane, and Xcode with its
command line tools for the iOS Simulator pane on macOS.
- Something is broken: open a bug report.
- Something is missing: request a feature.
- A security problem: please do not open a public issue. Follow SECURITY.md.
Include your version, taken from the status bar, and your platform. Logs help more than descriptions.
Free to use, but not open source. Those are two different things and Synapse is the first without being the second. You may install and use it at no charge, on as many of your own machines as you like. The source code is not published, and the licence does not grant the right to redistribute, resell, or offer it as a service.
See LICENSE.md for the terms, and THIRD-PARTY-NOTICES.md for the open source components Synapse is built with, which remain under their own licences.
If you were looking for the source in order to fix something or add something, open an issue instead and say what you needed. That is the route that exists.
Nahasat Nibir — Building intelligent, High‑performance developer tools, AI‑powered systems, and Adversarial platforms in Go and Rust.
- GitHub: https://github.com/Nibir1
- LinkedIn: https://www.linkedin.com/in/nibir-1/
- ArtStation: https://www.artstation.com/nibir