diff --git a/.gitignore b/.gitignore
index 3c4ebb2..33a11fa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 /bin/
+.dev-home/
 *.exe
 *.test
 *.out
diff --git a/Makefile b/Makefile
index 88acaca..6ce7d5b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,16 @@
-BINARY      := task-master
+BINARY      := tm
 CMD         := ./cmd/task-master
 VERSION_PKG := task/internal/version
 GIT_HASH    := $(shell git rev-parse --short HEAD 2>/dev/null || echo unknown)
 LDFLAGS     := -X $(VERSION_PKG).BuildVersion=$(GIT_HASH)
 
-.PHONY: build run version demo
+# Default: Go workspace bin (e.g. ~/go/bin). Override with: make install PREFIX=...
+GOPATH      ?= $(shell go env GOPATH)
+PREFIX      ?= $(GOPATH)
+INSTALL_BIN := $(PREFIX)/bin
+DEV_HOME    := $(CURDIR)/.dev-home
+
+.PHONY: build run run-dev install uninstall test version demo
 
 build:
 	go build -ldflags "$(LDFLAGS)" -o bin/$(BINARY) $(CMD)
@@ -12,6 +18,22 @@ build:
 run: build
 	./bin/$(BINARY)
 
+# Sandbox: isolated config/data under ./.dev-home (does not touch ~/.config)
+run-dev: build
+	TASK_MASTER_HOME=$(DEV_HOME) ./bin/$(BINARY)
+
+install: build
+	install -d $(INSTALL_BIN)
+	install -m 755 bin/$(BINARY) $(INSTALL_BIN)/$(BINARY)
+	@echo "installed $(INSTALL_BIN)/$(BINARY)"
+
+uninstall:
+	rm -f $(INSTALL_BIN)/$(BINARY)
+	@echo "removed $(INSTALL_BIN)/$(BINARY)"
+
+test:
+	go test ./...
+
 version: build
 	./bin/$(BINARY) version
 
diff --git a/cmd/task-master/main.go b/cmd/task-master/main.go
index 2da5266..e28394d 100644
--- a/cmd/task-master/main.go
+++ b/cmd/task-master/main.go
@@ -18,7 +18,7 @@ func main() {
 	if len(os.Args) > 1 {
 		switch os.Args[1] {
 		case "version", "--version", "-v":
-			fmt.Printf("%s  %s\n", config.AppName, version.BuildVersion)
+			fmt.Printf("%s  %s\n", config.CliName, version.BuildVersion)
 			return
 		case "help", "--help", "-h":
 			printHelp()
@@ -69,5 +69,9 @@ Usage:
   %s version   Print build version
   %s help      Show this help
 
-`, config.AppName, config.AppName, config.AppName, config.AppName)
+Env:
+  TASK_MASTER_HOME      Override home for config/data (dev/demo sandbox)
+  TASK_MASTER_DATA_DIR  Override data directory only
+
+`, config.CliName, config.CliName, config.CliName, config.CliName)
 }
diff --git a/demo.tape b/demo.tape
index c0c04b5..3613260 100644
--- a/demo.tape
+++ b/demo.tape
@@ -18,7 +18,7 @@ Set Padding 12
 Set Framerate 30
 
 # Isolated config/data so the demo never touches your real ~/.config
-Env HOME "/tmp/task-master-vhs"
+Env TASK_MASTER_HOME "/tmp/task-master-vhs"
 Env TERM "xterm-256color"
 Env EDITOR "vim"
 
@@ -33,7 +33,7 @@ Sleep 5s
 Show
 
 # --- launch ------------------------------------------------------------------
-Type "./bin/task-master"
+Type "./bin/tm"
 Enter
 Sleep 1s
 
diff --git a/internal/config/config.go b/internal/config/config.go
index cbc3cec..7134761 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -3,17 +3,23 @@ package config
 import "path/filepath"
 
 const (
-	AppName         = "task-master"
-	DefaultProject  = "inbox"
-	DefaultTheme    = "default"
-	configFileName  = "config.json"
+	// AppName is used for config/data directory names under XDG paths.
+	AppName = "task-master"
+	// CliName is the installed binary / command name.
+	CliName        = "tm"
+	DefaultProject = "inbox"
+	DefaultTheme   = "default"
+	configFileName = "config.json"
+
+	envHome    = "TASK_MASTER_HOME"
+	envDataDir = "TASK_MASTER_DATA_DIR"
 )
 
 // Config holds application settings persisted under ~/.config/task-master.
 type Config struct {
-	ActiveProject string            `json:"activeProject"`
-	DataDir       string            `json:"dataDir"`
-	Theme         string            `json:"theme"`
+	ActiveProject string `json:"activeProject"`
+	DataDir       string `json:"dataDir"`
+	Theme         string `json:"theme"`
 	// ProjectLists maps project ID → comma-separated board list ids
 	// (e.g. "all" or "backlog,in_progress").
 	ProjectLists map[string]string `json:"projectLists,omitempty"`
diff --git a/internal/config/loader.go b/internal/config/loader.go
index d0cecc6..2eac7c0 100644
--- a/internal/config/loader.go
+++ b/internal/config/loader.go
@@ -5,14 +5,28 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
+// ResolveHome returns the effective home for config/data paths.
+// TASK_MASTER_HOME overrides the real user home (useful for demos/dev sandboxes).
+func ResolveHome() (string, error) {
+	if h := strings.TrimSpace(os.Getenv(envHome)); h != "" {
+		return filepath.Clean(h), nil
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("resolve home directory: %w", err)
+	}
+	return home, nil
+}
+
 // LoadOrCreate loads the config from disk, creating defaults if missing.
 // It also ensures DataDir and the active project directory exist.
 func LoadOrCreate() (*Config, error) {
-	home, err := os.UserHomeDir()
+	home, err := ResolveHome()
 	if err != nil {
-		return nil, fmt.Errorf("resolve home directory: %w", err)
+		return nil, err
 	}
 
 	cfgPath := Path(home)
@@ -26,6 +40,10 @@ func LoadOrCreate() (*Config, error) {
 		return nil, err
 	}
 
+	if d := strings.TrimSpace(os.Getenv(envDataDir)); d != "" {
+		cfg.DataDir = filepath.Clean(d)
+	}
+
 	if err := ensureDataDirs(cfg); err != nil {
 		return nil, err
 	}
@@ -54,11 +72,12 @@ func readOrCreate(cfgPath, home string) (*Config, error) {
 	return &cfg, nil
 }
 
-// Save writes the config to ~/.config/task-master/config.json.
+// Save writes the config to ~/.config/task-master/config.json
+// (or under TASK_MASTER_HOME when set).
 func Save(cfg *Config) error {
-	home, err := os.UserHomeDir()
+	home, err := ResolveHome()
 	if err != nil {
-		return fmt.Errorf("resolve home directory: %w", err)
+		return err
 	}
 
 	cfgPath := Path(home)
diff --git a/internal/config/loader_test.go b/internal/config/loader_test.go
index d1ed440..4ec01bd 100644
--- a/internal/config/loader_test.go
+++ b/internal/config/loader_test.go
@@ -30,6 +30,8 @@ func TestDefaultsAndApplyDefaults(t *testing.T) {
 func TestSaveRoundTrip(t *testing.T) {
 	home := t.TempDir()
 	t.Setenv("HOME", home)
+	t.Setenv("TASK_MASTER_HOME", "")
+	t.Setenv("TASK_MASTER_DATA_DIR", "")
 
 	cfg := config.Defaults(home)
 	cfg.ActiveProject = "work"
@@ -54,6 +56,8 @@ func TestSaveRoundTrip(t *testing.T) {
 func TestLoadOrCreate(t *testing.T) {
 	home := t.TempDir()
 	t.Setenv("HOME", home)
+	t.Setenv("TASK_MASTER_HOME", "")
+	t.Setenv("TASK_MASTER_DATA_DIR", "")
 
 	cfg, err := config.LoadOrCreate()
 	if err != nil {
@@ -81,3 +85,38 @@ func TestLoadOrCreate(t *testing.T) {
 		t.Fatalf("DataDir mismatch")
 	}
 }
+
+func TestTASK_MASTER_HOME(t *testing.T) {
+	sandbox := t.TempDir()
+	t.Setenv("TASK_MASTER_HOME", sandbox)
+	t.Setenv("TASK_MASTER_DATA_DIR", "")
+
+	cfg, err := config.LoadOrCreate()
+	if err != nil {
+		t.Fatalf("LoadOrCreate: %v", err)
+	}
+	wantCfg := config.Path(sandbox)
+	if _, err := os.Stat(wantCfg); err != nil {
+		t.Fatalf("config under sandbox missing: %v", err)
+	}
+	wantData := filepath.Join(sandbox, ".local", "share", config.AppName)
+	if cfg.DataDir != wantData {
+		t.Fatalf("DataDir = %q, want %q", cfg.DataDir, wantData)
+	}
+}
+
+func TestTASK_MASTER_DATA_DIR(t *testing.T) {
+	home := t.TempDir()
+	data := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("TASK_MASTER_HOME", "")
+	t.Setenv("TASK_MASTER_DATA_DIR", data)
+
+	cfg, err := config.LoadOrCreate()
+	if err != nil {
+		t.Fatalf("LoadOrCreate: %v", err)
+	}
+	if cfg.DataDir != data {
+		t.Fatalf("DataDir = %q, want %q", cfg.DataDir, data)
+	}
+}
diff --git a/internal/ui/layout.go b/internal/ui/layout.go
index 76a67f7..687496b 100644
--- a/internal/ui/layout.go
+++ b/internal/ui/layout.go
@@ -10,7 +10,7 @@ import (
 )
 
 func (m Model) renderHeader() string {
-	brand := m.styles.HeaderBrand.Render(config.AppName)
+	brand := m.styles.HeaderBrand.Render(config.CliName)
 	project := m.styles.HeaderMeta.Render(fmt.Sprintf("project: %s", m.cfg.ActiveProject))
 	board := m.styles.FilterHint.Render(fmt.Sprintf("list: %s", m.boardFilter.Label()))
 	count := m.styles.HeaderMeta.Render(fmt.Sprintf("%d tickets", m.ticketCount()))