libtmux-go

README

libtmux for Go

Drive tmux from Go: sessions, windows, and panes as typed values, every tmux option and hook as a typed accessor, and errors classified by what tmux actually refused.

Run a command in a real terminal and read what it printed, find and filter what a tmux server holds, type into a pane and wait for its answer, and hear about changes as tmux makes them. It suits tools that drive a terminal program, test suites that need a real tmux, and agents that share a terminal.

Add it to your module:

$ go get github.com/libtmux/libtmux-go/tmux@latest

Alpha software. Releases carry an -alpha prerelease tag and the API is not settled. Pin an exact version.

It needs Go 1.26 or newer and tmux 3.3a or newer, on a Unix host. Before an operation reaches a daemon older than 3.3a, including unpatched 3.3, it returns tmux.ErrVersionTooLow and sends nothing; a plan leaves its operations skipped. A tmux that names no release, such as OpenBSD's base tmux or a bare master build, is refused too, and its error says the version is unrecognized rather than too low. A tmux older than 3.2 cannot answer the check and is refused the same way. To fix it, upgrade tmux and restart its server, since a running daemon keeps its version until it exits, or pin the previous libtmux-go release.

Server.Version and standalone Cmd calls with -V or -h report the executable, not a daemon, and do not clear later operations. The check relies on tmux's built-in commands, so a command-alias that redefines one defeats it.

A tmux server for AI agents and a tmuxp-style workspace builder ship beside the library, under Packages.

Contents — Quick start · Find things · Type and wait · Watch tmux · Choosing a path · Testing · Packages · Leaves out · Support · Documentation

Quick start

Run a command in tmux and print what its terminal showed. This is the whole program:

// Command quickstart runs a command in tmux and prints what it showed.
package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"os"

	"github.com/libtmux/libtmux-go/tmux"
)

func main() {
	if err := run(context.Background()); err != nil {
		log.Fatal(err)
	}
}

func run(ctx context.Context) (err error) {
	// A private server: a socket and an empty config of its own, so this
	// neither touches nor is changed by a tmux you already use.
	server, err := tmux.NewServer(tmux.ServerOptions{
		SocketName: "libtmux-quickstart",
		ConfigFile: os.DevNull,
	})
	if err != nil {
		return fmt.Errorf("configure tmux: %w", err)
	}
	session, err := server.NewSession(ctx, tmux.NewSessionRequest{Name: "demo"})
	if err != nil {
		return fmt.Errorf("create session: %w", err)
	}
	// Cleanup runs even when ctx is the reason the program is leaving.
	defer func() {
		err = errors.Join(err, server.Kill(context.WithoutCancel(ctx)))
	}()

	// The command runs in a window of its own, with a terminal.
	result, err := session.Run(ctx, "echo hello from tmux", tmux.RunOptions{})
	if err != nil {
		return fmt.Errorf("run command: %w", err)
	}
	for _, line := range result.Lines {
		fmt.Println(line)
	}
	fmt.Println("exit status:", result.Status)
	return nil
}

It prints:

hello from tmux
exit status: 0

To run it, save it as main.go in an empty directory, with tmux 3.3a or newer on PATH:

$ go mod init demo && \
    go get github.com/libtmux/libtmux-go/tmux@latest && \
    go run .

The program starts a tmux server on a socket and config of its own and kills it on the way out, so it leaves nothing behind and never touches a tmux you have open. Drop ServerOptions to its zero value and it drives the same server your tmux command does.

Session.Run is os/exec for a program that needs a terminal: the command runs in a window of its own with a tty, and what comes back is its exit status and the screen tmux rendered. A nonzero status is a result, not an error. examples/run-to-completion shows one, on a tmux server of its own.

Every Go block on this page comes from a program or test that runs on every supported release, against a real tmux wherever the block uses one, and each output shown is what that run printed.

Find sessions, windows, and panes

Server.Sessions: what tmux has now

One call asks tmux for every session. Server.Windows and Server.Panes are its siblings:

// Given: ctx context.Context; server tmux.Server
sessions, err := server.Sessions(ctx)
if err != nil {
	return fmt.Errorf("list sessions: %w", err)
}
for _, session := range sessions {
	name, _ := session.Name()
	fmt.Println("session:", name)
}

Each block on this page is the body of a function that returns an error, with the values its first line names already in hand.

examples/filter-query runs this and the two blocks below on a tmux server of its own. Like every example, it runs from a clone of the repository, with go -C examples run ./filter-query; examples/README.md has the commands to clone it.

This one prints session: libtmux-filter.

What comes back is a record: a Session you hold is what tmux said when you asked, not a live handle that changes underneath you. When no tmux server is running, a listing returns an error matching ErrNoServer rather than an empty list, so "nothing there" and "nobody to ask" stay different answers.

tmuxq.Matching: several answers from one read

Read the server once with Server.Snapshot and filter that read in Go. Matching takes any filter the tmux package declares:

// Given: ctx context.Context; server tmux.Server
snapshot, err := server.Snapshot(ctx)
if err != nil {
	return err
}
active, err := tmuxq.Matching(snapshot.Panes(), tmux.PaneActiveIs(true))
if err != nil {
	return err
}
fmt.Println("active panes:", len(active))

That session has one window with one pane in it, which is the active one, so the example goes on to print active panes: 1.

Server.SearchSessions: let tmux filter

One command goes out and only the matches come back:

// Given: ctx context.Context; server tmux.Server
live := tmux.TmuxFilter("#{==:#{session_name},libtmux-filter}")
sessions, err := server.SearchSessions(ctx, &live)
if err != nil {
	return err
}
fmt.Println("live matches:", len(sessions))

One session has that name, so this prints live matches: 1.

The filter is a tmux format, written the way the FORMATS section of the tmux manual describes, and tmux evaluates it while it lists. tmuxq/ has the filters that run in Go and the helpers that apply them.

Type into a pane and wait

PaneObservation.WaitFor: wait for what a command prints

A pane is an io.Writer through Pane.Writer, and a newline is the Enter key. Open an observation with Pane.OpenObservation before typing, then wait for text the command prints:

// Given: ctx context.Context; pane tmux.Pane
// Open the observation before typing, so no output is missed.
output, err := pane.OpenObservation(ctx)
if err != nil {
	return fmt.Errorf("observe pane: %w", err)
}
defer func() { err = errors.Join(err, output.Close()) }()

// A pane is an io.Writer, and a newline is the Enter key.
command := `echo "6 x 7 = $((6 * 7))"`
if _, err := fmt.Fprintln(pane.Writer(ctx), command); err != nil {
	return fmt.Errorf("type command: %w", err)
}
// The terminal echoes what is typed, so wait for the answer: the typed
// line says "$((6 * 7))" and never "42".
if _, err := output.WaitFor(ctx, func(text string) bool {
	return strings.Contains(text, "6 x 7 = 42")
}); err != nil {
	return fmt.Errorf("wait for answer: %w", err)
}
fmt.Println("the pane answered 6 x 7 = 42")

tmux pushes each write as it happens, so nothing polls. The terminal echoes what is typed, and that echo is output too, which is why the wait names the answer rather than the request.

Runnable: examples/pane-io, which goes on to read the pane as an io.Reader.

Typing is the wrong way to move a payload: the shell in the pane reads quotes, $, and backslashes in it as shell syntax. Server.LoadBufferFrom fills a tmux buffer from an io.Reader instead, and Pane.CaptureTo writes a scrollback to an io.Writer. examples/byte-streams does both.

Watch tmux change

Session.OpenNotifications: hear changes as they happen

It returns a stream of what tmux does, such as a window opening or a session being renamed. tmux pushes each change when it happens, so nothing has to guess how often to ask:

// Given: ctx context.Context; session tmux.Session
stream, err := session.OpenNotifications(ctx, tmux.NotificationOptions{})
if err != nil {
	return fmt.Errorf("open notification stream: %w", err)
}
defer func() { err = errors.Join(err, stream.Close()) }()

// Rename after subscribing; notifications do not include earlier changes.
if _, err := session.Rename(ctx, "control-example"); err != nil {
	return fmt.Errorf("rename session: %w", err)
}

for {
	notification, err := stream.Next(ctx)
	if err != nil {
		return fmt.Errorf("read notification: %w", err)
	}
	fmt.Printf("notification: %s\n", notification.Kind())
	if notification.Kind() == tmux.ControlNotificationSessionRenamed {
		fmt.Println("heard the rename")
		break
	}
}

The first notification a new stream reads is %session-changed, which is tmux telling the client which session it joined. The rename follows it.

This prints notification: %session-changed, then notification: %session-renamed, then heard the rename.

NotificationStream.Subscribe: have tmux watch a value

A subscription goes further: tmux evaluates a format for you and reports it each time its value changes, so a program hears about a window count or a pane's current command without asking again:

// Given: ctx context.Context; session tmux.Session;
// stream *tmux.NotificationStream
// A subscription is a format tmux evaluates for you: it reports the value
// when it first looks, about a second later, and then each time it changes.
if err := stream.Subscribe(ctx, tmux.SubscriptionRequest{
	Name: "windows", Format: "#{session_windows}",
}); err != nil {
	return fmt.Errorf("subscribe: %w", err)
}
if _, err := session.NewWindow(ctx, tmux.NewWindowRequest{}); err != nil {
	return fmt.Errorf("open window: %w", err)
}
for {
	notification, err := stream.Next(ctx)
	if err != nil {
		return fmt.Errorf("read notification: %w", err)
	}
	if change, ok := notification.Subscription(); ok && change.Value == "2" {
		fmt.Println("session has", change.Value, "windows")
		return nil
	}
}

The session started with one window, so this prints session has 2 windows.

Runnable: examples/control-mode-subscribe is the program both blocks come from.

Choosing how to reach tmux

Start with a plain Server, which starts one tmux process per command. The other paths keep a tmux client attached, or send several commands at once, to start fewer:

Path	Construct it with	Cost	Reach for it
a process per command	tmux.NewServer	a tmux process per command sent	one-shot commands
a connection	Session.OpenControl	one tmux client, kept attached	repeated commands
several connections	ConnectionOptions{Lanes: N}	N tmux clients, kept attached	readers running in parallel
a plan	tmux.NewPlan then Plan.Run	fewer process starts	builds and layouts
a stream	Session.OpenNotifications	one tmux client, kept attached	watching what tmux does

tmux.NewPlan: write a layout in one pass

A plan records commands instead of running them, sends the ones needing no answer together, and hands back a reference to what a step will create. new("echo built") is how Go 1.26 writes a pointer to a value, for a field that may be left unset:

// Given: window tmux.Window
plan := tmux.NewPlan()
plan.SelectLayout(window.Ref(), tmux.SelectLayoutRequest{Layout: "tiled"})
editor := plan.SplitPane(window.Ref(), tmux.SplitPaneRequest{Attach: true})
plan.SetPaneTitle(editor, "editor")
plan.SendKeys(editor, tmux.SendKeysRequest{Command: new("echo built")})
plan.DisplayMessage(editor, "#{pane_title}")

Plan.Run sends it, and reports on each step by itself even where several shared one tmux process:

// Given: ctx context.Context; server tmux.Server; plan *tmux.Plan
result, err := plan.Run(ctx, server)
if err != nil {
	return fmt.Errorf("run plan: %w", err)
}
if !result.OK() {
	return fmt.Errorf("plan did not complete: %w", result.Err())
}

// Results remain per operation even when operations share an invocation.
for index, op := range result.Ops {
	fmt.Printf("step %d %-16s %-8s created %q stdout %q\n",
		index, op.Command, op.Status, op.Created, op.Stdout)
}

examples/planned-build is the program both blocks come from.

It prints operations: 6, tmux invocations: 4 before it runs the plan: six tmux commands, in four process starts rather than six. The last step reads back the title the plan set, so its line ends stdout ["editor"].

A connection appears in list-clients and counts toward session_attached, which is why opening one is explicit. "Execution modes" in the package documentation has the rules each path follows, and BENCHMARKS.md is what each costs, measured on every supported tmux. examples/fast-path runs the same reads down each path.

Testing your own code

tmuxtest.RunInPane: run your program in a real pane

tmux/tmuxtest runs your program inside a real tmux and lets a test assert on what it drew, without a sleep in it. This is a whole test file:

package greeter_test

import (
	"context"
	"os"
	"testing"
	"time"

	"github.com/libtmux/libtmux-go/tmux/tmuxtest"
)

func TestMain(m *testing.M) {
	os.Exit(tmuxtest.Main(m))
}

func TestGreeterAnswersALine(t *testing.T) {
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	// A stand-in for your program: it greets each name it reads.
	greeter := `while read name; do echo "hello, $name"; done`
	pane := tmuxtest.RunInPane(ctx, t, greeter)

	tmuxtest.Type(ctx, t, pane, "world")
	tmuxtest.WaitForLine(ctx, t, pane, "hello, world")
}

tmuxtest.WaitForText: a failed wait shows the screen

A wait that runs out fails with the screen the pane last held, which is what you would have added a print statement to see. This one was waiting for ready:

tmuxtest: pane %1 never showed a line containing "ready"
the pane showed 3 line(s):
    | tmuxtest$ printf 'loading widgets\nconnecting\n'; cat
    | loading widgets
    | connecting

More in tmuxtest

tmuxtest.NewServer gives a test whose subject is tmux itself a server on a socket of its own, killed when the test ends. tmuxtest.ScriptedTmux answers the tmux commands you name instead, so a test of your own code needs no tmux installed. tmux/tmuxtest shows both.

Packages

Package	Source	Reference	What it is
tmux	tmux/	pkg.go.dev	The library. Sessions, windows, panes, options, hooks, formats, filters, snapshots, plans.
tmuxtest	tmux/tmuxtest/	pkg.go.dev	Run your program in a real tmux and assert on what it drew.
tmuxq	tmuxq/	pkg.go.dev	Model-free generic helpers for slices and iter.Seq.

Others ship as separate modules, so go get on the library pulls in none of them:

Module	Source	Reference	What it is
mcp	mcp/	pkg.go.dev	A tmux server for AI agents, over the Model Context Protocol
workspace	workspace/	pkg.go.dev	Loads tmuxp-style YAML workspaces and builds them, with a CLI
benchmarks	benchmarks/	—	Prints what each way of reaching tmux costs

The MCP server:

$ go install github.com/libtmux/libtmux-go/mcp/cmd/libtmux-mcp@latest

The workspace CLI:

$ go install github.com/libtmux/libtmux-go/workspace/cmd/tmux-workspace@latest

tmux: the library

Sessions, windows, panes, options, hooks, formats, filters, snapshots, and plans, with no dependency outside the standard library. Reference: pkg.go.dev and libtmux.org.

Session.Run runs a command in a window of its own, with a terminal. A nonzero exit status is a result, not an error:

// Given: ctx context.Context; session tmux.Session
// The command runs with a terminal, so test -t holds where a pipe fails.
command := "test -t 1 && echo stdout is a terminal; exit 3"
result, err := session.Run(ctx, command, tmux.RunOptions{})
if err != nil {
	return fmt.Errorf("run command: %w", err)
}
for _, line := range result.Lines {
	fmt.Println("screen:", line)
}
fmt.Println("exited", result.Status)

This prints screen: stdout is a terminal, then exited 3.

tmuxq: filters for any slice

Helpers that find records in a slice or an iter.Seq. The package imports no tmux type, so they work on a slice of your own as well as on the records tmux returns. Reference: pkg.go.dev and libtmux.org.

tmuxq.Where keeps what a function accepts, and tmuxq.First returns the first match. This needs no tmux:

type task struct {
	name string
	done bool
}
tasks := []task{{"build", true}, {"test", false}, {"deploy", false}}
open := func(t *task) bool { return !t.done }

for _, t := range tmuxq.Where(tasks, open) {
	fmt.Println("open:", t.name)
}
first, _ := tmuxq.First(tasks, open)
fmt.Println("first open:", first.name)

This prints open: test and open: deploy, then first open: test.

tmuxtest: a real tmux for tests

Runs your program in a real pane and lets a test assert on what it drew. The server, its sessions, and its panes end with the test. Reference: pkg.go.dev and libtmux.org.

tmuxtest.NewServer gives a test whose subject is tmux itself a server on a socket of its own. This is the body of a test, in a package whose TestMain calls tmuxtest.Main, as in the test above:

// Given: ctx context.Context; t *testing.T
server := tmuxtest.NewServer(ctx, t)

session, err := server.NewSession(ctx, tmux.NewSessionRequest{Name: "under-test"})
if err != nil {
	t.Fatal(err)
}
if name, _ := session.Name(); name != "under-test" {
	t.Errorf("session name = %q, want under-test", name)
}

workspace: tmuxp-style workspaces

Loads tmuxp-style YAML workspace files and builds them in tmux, from Go or with the tmux-workspace command. Reference: pkg.go.dev, libtmux.org, and the command reference. workspace/CLI.md covers every command and its output formats.

With the command installed as above and a workspace file saved as project.yaml, build it on a tmux socket named project without attaching to it:

$ tmux-workspace load \
    -L project \
    -d \
    ./project.yaml

mcp: a tmux server for agents

Serves one tmux server to Model Context Protocol clients, as the libtmux-mcp command or from a program of your own. Reference: pkg.go.dev, libtmux.org, and the tool pages. mcp/README.md covers client configuration, and mcp/TOOLS.md lists each tool's arguments and results.

An MCP client starts the server installed above itself and speaks to it over stdin and stdout. Register it with Claude Code:

$ claude mcp add tmux -- libtmux-mcp

Check which socket it reaches, and what that holds, without a client:

$ libtmux-mcp -doctor

The benchmarks module is a tool rather than a library. It prints what each way of reaching tmux costs.

What it leaves out

• Live objects. A Session or a Pane is a record of what tmux reported when it was read, and does not change when tmux does. Read again, or subscribe, to see a change.
• A terminal emulator. A capture and Session.Run return the screen tmux drew. PaneObservation returns the bytes a program wrote.
• Your tmux configuration file. Options and hooks are read and set on a running server, and nothing here edits ~/.tmux.conf. tmux reads it when it starts a server, unless ServerOptions.ConfigFile names another.

Support and status

Any release may change or remove exported identifiers without a deprecation period, so pin an exact version. Not recommended for production.

• No runtime dependencies. The core module imports only the standard library.
• Go 1.26+, rising with Go's own support window, about twice a year. tmux 3.3a through 3.8 across the core, workspace, and MCP modules, tested on releases spanning that range.
• Unix. Linux and macOS are tested on every change, and the BSDs, illumos, and Plan 9 build. A Windows build compiles, so a cross-platform program still builds, but there is no tmux there to reach.
• Tagged per directory. Each module carries its own version: the tags are mcp/vN and workspace/vN beside the core's plain vN. Pin the exact ones you want in your own go.mod; the commands here fetch the newest.

Documentation

The package documentation is the reference, written to be read start to finish rather than searched:

$ go doc github.com/libtmux/libtmux-go/tmux

It opens with a task index, and carries the rule mapping a tmux command to its Go method: kill-pane is Pane.Kill, and rename-session is Session.Rename. A command usually leads to its method without a lookup.

Reference	Every exported identifier, method, and field, one page each
tmux/	How the library is shaped: records, naming, options, errors
examples/	Runnable programs, one per topic, each with a page of notes
DESIGN.md	The conventions this package holds itself to, and the bakeoffs behind them
PARITY.md	How the surface is checked against the Python libtmux
BENCHMARKS.md	What each way of reaching tmux costs
CHANGELOG.md	What each release changed
SECURITY.md	What this software executes, and how to report a hole in it
CONTRIBUTING.md	The gates a change has to pass, and where the writing rules live
WRITING.md	How this repository writes: docs, the changelog, commits
AGENTS.md	Which of the above applies to what you are changing

Attribution

Please use the following BibTeX template to cite libtmux-go in scientific discourse:

@misc{libtmux-go,
   author = {Tony Narlock},
   year = {2026},
   note = {https://libtmux.org/en/go/},
   title = {libtmux-go: Go wrapper for tmux}
}

License

MIT. See LICENSE.