Muster Agent

The open-source AI Development Environment (ADE) that remembers.

A desktop app for macOS, Windows and Linux where coding agents work in your folders, with long-term memory, sandboxes, and the agents, routers and models you already use, all in one window.

Works with Codex, Claude Code, Cursor, Gemini CLI, OpenCode and Grok, any OpenAI-compatible router (OmniRoute, OpenRouter, LiteLLM) and local models (Ollama, LM Studio). Paperclip tasks run locally with automatic hand-back.

Made in India 🇮🇳 · themuster.dev

https://github.com/user-attachments/assets/9602a60c-2faf-4138-92a1-7d850d0b44ab

⬇ Download Muster Agent

macOS (Apple silicon and Intel) .dmg · Windows 10/11 installer -win-x64-setup.exe · Linux .AppImage / .deb

A chat on the left and the live diff of the agent's edit on the right. Undo any change before you keep it.

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Why Muster Agent

Most agent apps start every chat from zero, run commands straight on your machine, and lock you into one vendor's models. Muster Agent is an agentic development client (ADC) built the other way around:

• It remembers. Long-term memory, backed by the Hindsight memory engine, carries what the agent learned about you and each project into the next chat. You can see what will be recalled before you send.
• It keeps agents contained. Each chat or folder can get its own Docker-backed computer with no network by default, capped memory, CPU and process counts, and only the grants you give it.
• It uses the providers you already have. On first launch it finds your existing sign-ins, gateways, API keys and local model servers. You don't sign in again.
• It stays light. Long chats, terminals and diffs are virtualized and kept in bounded buffers, so memory use stays bounded as a session grows.
• It is a real workbench. Live diffs with Keep/Undo, a terminal, a browser, git history and parallel chats sit next to the conversation, so you rarely have to switch windows.

Tour

What each part of the app looks like, and what to look for. The screenshots use a made-up project, taskboard, a small TypeScript API and web board.

Memory

Agents that learn, not just agents that chat.

• Personal and per-folder memory. Notes live in your Personal scope or with a folder or project, so one repo's conventions never leak into another.

• Recall preview. A chip in the composer shows which notes the next turn will recall for the draft you are typing. Open it to inspect them, or leave one out of this chat.

• Auto-save after runs. Choose Never, Ask after runs, or Save after completed runs. Recall runs automatically before each turn, and you can turn it off.

• You're in control. Browse, search, add and delete memories in the Memory screen. Deletions are tracked until the engine confirms them.

• Powered by Hindsight. Point Muster at a Hindsight endpoint in Memory settings (for example http://localhost:8888), or set HINDSIGHT_API_URL / HINDSIGHT_API_KEY. A key saved in settings is stored encrypted.

Sandboxing

Give an agent a computer of its own instead of your laptop.

The chat runs in a disposable sandbox. Look for No network, the memory, CPU and process meters, and the commands it ran.

• Scoped computers. A chat (session) or a folder (workspace) gets its own Docker container, with its own history, files and services.
• Safe defaults. No network unless you allow egress. Defaults are 512 MiB of memory, 1 CPU and 256 processes, adjustable per computer. At most two computers run at once.
• Explicit grants. Environment variables and tool access are allowlisted. Extra folders can be mounted read-only.
• Optional. Install Docker Desktop to turn sandboxes on. Without it, everything else works normally.

Your providers

Muster Agent detects what is already on your Mac and uses it as-is:

Source	What it picks up
Subscription sign-ins	Your ChatGPT and Claude sign-ins from the command-line tools already on this Mac
Routers and gateways	OpenAI-compatible gateways already configured in your local agent CLI config
API keys in your environment	OPENAI_API_KEY, ANTHROPIC_API_KEY, OPENROUTER_API_KEY, GROQ_API_KEY, MISTRAL_API_KEY, DEEPSEEK_API_KEY, GEMINI_API_KEY, XAI_API_KEY, TOGETHER_API_KEY, FIREWORKS_API_KEY
Local models	Ollama and LM Studio on this Mac, on their default ports or the ports their config names
Anything else	Add a custom OpenAI-compatible endpoint

Models come from each provider's own /models endpoint. There is no hard-coded model list. If nothing is found, guided setup walks you through adding a provider.

Pick any ready provider's model per chat, with its context size, image support and reasoning level.

Built for low RAM

Agent sessions get long. Muster Agent keeps what it holds in memory bounded:

Tool rows fold into one line per step and long output shows only its tail until you ask for more.

• Virtualized timelines. Chat history, tool output and git history render only the rows on screen.
• Incremental streaming. Streaming Markdown re-parses only the part still being written, so finished code blocks are not re-parsed on every token. The timeline syncs as a snapshot plus ordered deltas, and completed rows keep their identity.
• Panes load when you open them. Settings, Projects, Memory, Automations, git history, pull requests and computer tabs load on first use. They are preloaded when the app is idle.
• One terminal emulator per shell. It moves between the bottom panel and the side tab instead of being rebuilt. Scrollback is capped at 5,000 lines.
• Bounded command output. Each command keeps up to 128 KB, and finished commands share a 2 MB budget. Older output keeps only its tail.
• Workers that go away. Diffing and syntax highlighting run in web workers, off the UI thread. Idle workers are shut down and recreated on demand.

Features

Live diffsReview each edit as it lands. Keep or Undo per hunk or per file, or view whole-file inline diffs.	Integrated terminalA bottom panel with real shells and search.	Built-in browserPreview your app, read its console and pick elements for the agent.
Git tabCommit history, and compare any two refs.	Parallel chats and projectsSeveral chats in one checkout, with overlap detection and "Run in a worktree".	Skills, plugins and MCPInstall plugins, write skills, connect MCP servers.
AutomationsScheduled runs, or runs triggered by new pull requests, pushes and failed CI checks.	Import past sessionsBring in conversations from other agent tools and chat exports, read-only.	Spotlight searchSearch chats, messages, files and folders. Type > for commands.

Install

1. Download the newest Muster-Agent-<version>-arm64.dmg (Apple silicon) or -x64.dmg (Intel) from the latest release. All Muster Agent releases are tagged agent-v…. A .zip of the same app is attached too, and SHA256SUMS lets you check the download (shasum -a 256 -c SHA256SUMS --ignore-missing).

2. Drag Muster Agent onto Applications.

3. First open: right-click, then Open. Builds are signed with the self-signed "Muster Agent Self-Signed" identity but are not notarized by Apple, so macOS blocks the first launch. Right-click Muster Agent in Applications, choose Open, then Open again (on recent macOS: System Settings > Privacy & Security > Open Anyway). Or clear the quarantine flag once:

   xattr -dr com.apple.quarantine "/Applications/Muster Agent.app"
   

   The signing identity stays the same from one release to the next, so macOS keeps the permissions you grant (Screen Recording, Accessibility) across updates.

4. Updates arrive automatically. The app checks GitHub Releases, verifies the download against its published SHA-256 and code signature, and accepts it only if it is signed by the same identity. The update installs when you restart.

Requirements: macOS 14 (Sonoma) or later and a model provider (see Your providers). The macOS download comes in Apple silicon (-arm64) and Intel (-x64) builds; building from a clone (below) also works on either. Docker Desktop is optional and only needed for sandboxes.

Windows

1. Download Muster-Agent-<version>-win-x64-setup.exe from the latest release and run it. It installs for your user (no admin needed) and adds a Start menu shortcut. A portable -win-x64.zip is attached too.
2. The installer is not code-signed yet, so SmartScreen may warn: choose More info → Run anyway.
3. Terminals open PowerShell. Muster finds Codex and Claude Code whether they came from npm (codex.cmd) or a native installer. Computer use and Quick Look previews are macOS-only; everything else works.
4. Updates: Muster tells you when a new version is out; Download update opens the release page.

Linux

1. AppImage (any x64 distro): download Muster-Agent-<version>-linux-x86_64.AppImage, then chmod +x Muster-Agent-*.AppImage and run it.
2. Debian / Ubuntu: sudo apt install ./Muster-Agent-<version>-linux-amd64.deb, then open Muster Agent from your app menu. A -linux-x64.tar.gz is attached too.
3. Sandboxes use Docker Engine. Computer use and Quick Look previews are macOS-only.
4. Updates: Muster tells you when a new version is out; Download update opens the release page.

Every file's checksum is in SHA256SUMS on the release.

Run Muster Agent on another Mac (from source)

A fresh clone builds and runs with no sibling checkouts and no environment variables: the few Muster core sources the app bundles are vendored in packages/agent-app/vendor/ (see its README).

Prerequisites

• macOS 14 (Sonoma) or later. Apple silicon and Intel both work: npm installs the matching Electron build and node-pty is compiled for the local architecture.
• Node.js 24 (pinned in packages/agent-app/.nvmrc and .node-version, so nvm use, fnm use or mise pick it up), with the npm that ships with it.
• git.
• Xcode Command Line Tools (xcode-select --install), used to compile node-pty for the integrated terminal. Without them the install still succeeds and falls back to node-pty's prebuilt binary.

One command

git clone https://github.com/musterhq/muster-code.git && cd muster-code \
  && cd packages/agent-app && npm ci && npm start

Or let the helper check prerequisites first (macOS, Node 24 with an nvm/fnm/mise switch if one is installed, git, Xcode tools), then run npm ci and npm start:

git clone https://github.com/musterhq/muster-code.git && cd muster-code \
  && ./packages/agent-app/scripts/run-mac.sh

npm ci installs the exact locked dependencies, downloads Electron (about 100 MB), and its postinstall step rebuilds node-pty for Electron. After that, npm start builds dist/ and opens the app; later runs only need npm start from packages/agent-app.

First launch

Muster Agent looks for providers you are already signed in to on that Mac and uses them directly. If it finds none, it opens guided setup to sign in or add one. Settings and chats live in ~/Library/Application Support/Muster Agent; pass --user-data-dir=/some/dir (for example npx electron . --user-data-dir=/tmp/muster-test) to run an isolated profile.

Optional capabilities

• Sandboxes: install and start Docker Desktop. Without it, sandboxed runs are unavailable and the rest of the app works normally.
• Computer use: grant Screen Recording and Accessibility in System Settings > Privacy & Security when macOS prompts (for a dev run the permission is attributed to Electron or your terminal).

Build a local .app

cd packages/agent-app
npm run build && node scripts/package-preview.mjs   # -> release/Muster Agent Preview.app

Without MUSTER_SIGN_IDENTITY the bundle is ad hoc signed, so Gatekeeper blocks a copy moved to another Mac: right-click the app and choose Open the first time, or clear the quarantine flag with xattr -dr com.apple.quarantine "Muster Agent Preview.app". Developer ID signing and notarization are covered in packages/agent-app/docs/RELEASE.md.

Troubleshooting

• Wrong Node version (EBADENGINE warning, or build errors): run nvm use / fnm use in packages/agent-app, or install Node 24, then rm -rf node_modules && npm ci.
• The terminal pane fails to start, or postinstall printed a node-pty warning: install Xcode Command Line Tools, then npm run rebuild:native. Set MUSTER_SKIP_NATIVE_REBUILD=1 to skip the rebuild during npm ci (for example on CI).
• Electron download failed during install: re-run npm ci, or just npm start (Electron retries the download on first launch).
• Contributors with their own Muster core checkouts can override the vendored sources with MUSTER_CORE_CLIENT_ENTRY, MUSTER_RUNTIME_SOURCE_ROOT and MUSTER_SANDBOX_SOURCE_ROOT; the build log prints which source each bundle used. npm run vendor:sync refreshes vendor/ from them.

What's in this repository

This repository holds two apps: Muster Agent (above) and Muster Code, a Code-OSS-based IDE with the Muster agent built in.

• packages/agent-app/ — Muster Agent, the standalone Electron agent app. Developer notes are in its README.
• product/ — the Muster Code distribution overlay (branding, Open VSX gallery, Muster as the default chat agent, proposed-API grants).
• packages/builtin/ — the built-in Muster layer for Muster Code: default chat participant, agent thread sessions, model provider, threads view, board, live diff, inline completions. Bundled into the app as muster.muster-code.
• scripts/assemble.sh — builds dist/Muster Code.app from a prebuilt Code-OSS binary + overlay + built-in layer, with no editor compile step.
• Engine: @musterhq/core (the open-source muster) linked from the sibling checkout.

Build Muster Code

pnpm install
pnpm assemble          # → dist/Muster Code.app
open "dist/Muster Code.app"

Dev launch (isolated profile): MUSTER_CODE_DEV_SOCK=/tmp/mc-dev.sock "dist/Muster Code.app/Contents/MacOS/Muster Code" --user-data-dir /tmp/mc-udd /tmp/mc-sample

Base: Code-OSS 1.126 (Electron 42, Node 24 with node:sqlite), from prebuilt Code-OSS release binaries.

License

MIT — see LICENSE. Third-party components are listed in THIRD_PARTY_NOTICES.md.

Made in India. Codex, ChatGPT and OpenAI are trademarks of OpenAI; Claude and Claude Code are trademarks of Anthropic; Cursor is a trademark of Anysphere; Gemini is a trademark of Google LLC. Muster Agent is an independent open-source project and is not affiliated with or endorsed by them.