Know what's running on your machine and who started it

Your coding agents start dev servers in five worktrees at once. Sonar tracks every port on your machine and who started it (the project, the worktree, the agent session), so you know what's safe to kill. And your agents can ask it too.

For developers running Claude Code, Cursor and Codex in parallel worktrees.

Free beta · macOS and Linux · Open-source CLIv0.1.0-beta.2, released Sep 7, 2026 · Release notes

Install the beta See how it works

$ brew install raskrebs/sonar/sonar && sonar install desktop

or pick a download ↓

Every port on the machine, filed by project and worktree.

Live demo · click around

Sonar

Starting Sonar…

The problem

“Address already in use.” Again.

Your agents start dev servers in five worktrees at once. Nobody knows what's running, whose it is, or whether it's safe to kill.

~/code/worktrees/fix-ui $ npm run dev

Error: listen EADDRINUSE: address already in use :::5173

~/code/worktrees/fix-ui $ lsof -i :5173

node 48213 you 23u IPv6 TCP *:5173 (LISTEN) # …but whose node?

“I have three Claude sessions in three worktrees and they all want port 5173.”

“I don't dare kill that process. It might be the other agent's.”

“My terminal tabs were the only record of what I started, and I closed them.”

“The staging box has something on 8080 and I have to SSH in to find out what.”

None of today's tools can tell you which agent or worktree owns a port. Sonar can.

How it works

One daemon that knows who owns every port

A small background process, the daemon, keeps one list of every port. The CLI, the desktop app and your agents all read that same list.

Every port has an owner

Not “node on 3000”, but frontend in my-app@fix-ui, started by a Claude session at 14:02. Docker containers, Compose projects and processes you started by hand are picked up too.

$ sonar list --tree
$ sonar info 3000

Built for agents, not just people

Agents query the same list over MCP. Each worktree can claim its own block of ports, and hooks tie everything a session starts back to that session.

See the ten MCP tools

$ sonar sessions

One registry, every surface

The CLI, the MCP server, the desktop app and the tray all read one list. Start a server from a terminal and it appears in the window you're looking at.

$ sonar start --name api -- npm run dev

Your whole project, as one thing

List your services in .sonar.yaml, or prefix the commands in your dev script with sonar start. Either way the project becomes one group, named after the repository, that you can start, wait for, tail and stop in one go.

# start every service in the project
$ sonar up
# stop all of it
$ sonar kill -g my-app

$ sonar list --tree
my-app  (3 ports, running)              ~/code/my-app
├─ 5432  db          postgres:17        http://localhost:5432
├─ 5173  frontend    vite (v5.4)        http://localhost:5173
└─ 8000  api         uvicorn app:app    http://localhost:8000
ungrouped (1 port)
└─ 3000  next-server (v16.1.6)          http://localhost:3000

Coming next

Remote hosts

Add any box you reach over SSH and its ports join the same list, with the same actions. In the CLI as a beta today, in the app next.

Beta in CLI

Sharing

Share a service from the same place, keyed on the project's service, so it gets the same URL every time, from any clone.

Planned

For parallel agents

Your agents can ask

Before an agent kills a port, it can check whose it is. Before it starts a server, it can pick a port no other worktree will use.

Set up in one line each

For Claude Code, Cursor and Codex.

# the registry, over MCP
$ sonar install mcp
# when to use it
$ sonar install skills
# attribute what a session starts
$ sonar install hooks

Keep worktrees apart

Each checkout claims a stable block of ports that its siblings never get.

# this worktree's own ports
$ sonar claim --count 3
# the next free port from 3000
$ sonar next 3000
# stop sleeping in scripts
$ sonar wait 8000 --http=/health

Ten MCP tools, one registry

What an agent can call once Sonar is installed.

list_ports: Every listening port, with its group, service and session
inspect_port: Who started a port, when, and from where
list_sessions: Which agent sessions are running what, in which worktree
claim_port: Reserve ports for this worktree, the same ones every time
next_free_port: A free port that steps over every other worktree's claim
wait_for_port: Block until a service answers instead of sleeping
health_check: Tell a bound port from a service that actually works
tail_logs: Read a service's output
dependency_graph: What talks to what, before you stop anything
port_history: What was on 3000 an hour ago, and where it went

Why not just…

There's a tool for each piece. None of them knows who started what.

Sonar isn't a better port killer. It's the registry the others don't have, and your agents can read it.

Sonar compared with other port and process tools
Capability	Menu-bar port apps	Process runners	lsof & ps	Agent port tools	Sonar
Shows what's listening	Yes	Only what it started	Yes	Yes	Yes
Knows the project, worktree and agent behind a port	No	No	No	No	Yes
Agents can query it over MCP	No	No	No	Some	Yes
Starts and stops whole projects	Kills ports	Yes	No	Not the focus	Yes
Reserves ports per worktree	No	No	No	Named URLs instead	Yes

Menu-bar apps like Ports, Portman and PortKiller. Process runners like process-compose, Overmind and mprocs. Agent port tools like port-kill and Vercel's portless. Each does its one job well; Sonar ties the jobs together around who owns what.

Install

Get Sonar running in a minute

Version 0.1.0-beta.2, released Sep 7, 2026. Free, and no account needed.

Install from the terminal

Recommended

Two commands. The first installs the sonar CLI with its MCP server; the second adds the desktop app. Only want the terminal? Stop after the first.

With Homebrew

$ brew install raskrebs/sonar/sonar
$ sonar install desktop

Homebrew 6 asks you to trust the tap once first: brew trust raskrebs/sonar

Or with the install script

$ curl -sfL https://raw.githubusercontent.com/raskrebs/sonar/main/scripts/install.sh | bash
$ sonar install desktop

Or download the app

Every build of v0.1.0-beta.2. On Ubuntu or Debian, take the .deb; on other distros, the AppImage.

macOSApple silicon

Sonar_0.1.0-beta.2_aarch64-apple-darwin.app.tar.gz · 15.9 MB

.tar.gz

macOSIntel

Sonar_0.1.0-beta.2_x86_64-apple-darwin.app.tar.gz · 17.1 MB

.tar.gz

Linuxx86_64

Sonar_0.1.0-beta.2_amd64.AppImage · 94.5 MB

.deb AppImage

Linuxarm64

Sonar_0.1.0-beta.2_arm64.AppImage · 92.1 MB

.deb AppImage

Windows

x64 installer on the way

Soon

Then try it

See every port filed by project, ask who owns one, and give your agent the same view. The app shows the same list the moment it opens.

# every port, by project
$ sonar list --tree
# who started it, when, from where
$ sonar info 3000
# give your agent the same view
$ sonar install mcp

FAQs

Questions people ask

Straight answers about installing, running and trusting Sonar on your machine.

Those answer what's on port 3000. Sonar answers who started it (which project, worktree and agent session) and whether it's yours to kill. It's also a daemon, so your agents can ask the same question over MCP.

Claude Code, Cursor and Codex. sonar install mcp gives an agent the MCP server, sonar install skills teaches it when to use it, and sonar install hooks ties everything a session starts back to that session.

See who owns every port in under a minute.

Install the CLI and the app, then run sonar list --tree.

$ brew install raskrebs/sonar/sonar && sonar install desktop

All downloads

Contact

Talk to the people building it

Still have a question, found a bug, or want Sonar to understand your stack? We read every message.

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Questions, feedback and anything else.

Report an issue

Bugs and feature requests, in the open.

Know what's running on your machine and who started it

“Address already in use.” Again.

One daemon that knows who owns every port

Every port has an owner

Built for agents, not just people

One registry, every surface

Your whole project, as one thing

Your agents can ask

There's a tool for each piece. None of them knows who started what.

Get Sonar running in a minute

Then try it

Questions people ask

How is this different from a menu-bar port killer?

Does Sonar stop port conflicts?

Can I use just the CLI and MCP, without the app?

Do I need to install the CLI before the app?

Which platforms does it run on?

Which agents does it work with?

Why does macOS warn me about the app?

Does Sonar send anything off my machine?

Is it open source?

What does it cost?

See who owns every port in under a minute.

Talk to the people building it