feat(config): add LogDir and move diagnostic logs to XDG state

CLAUDE.md

@@ -14,6 +14,7 @@ make clean              # Remove build artifacts
 ```
 
 Run a single integration test:
+
 ```bash
 make test-integration RUN=TestStartCommandSucceedsWithValidToken
 ```
@@ -36,14 +37,15 @@ Note: Integration tests require `LOCALSTACK_AUTH_TOKEN` environment variable for
 
 # Logging
 
-lstk always writes diagnostic logs to `$CONFIG_DIR/lstk.log` (appends across runs, cleared at 1 MB). Two log levels: `Info` and `Error`.
+lstk always writes diagnostic logs to `$LOG_DIR/lstk.log` (appends across runs, cleared at 1 MB). Two log levels: `Info` and `Error`.
 
 - `log.Logger` is injected as a dependency (via `StartOptions` or constructor params). Use `log.Nop()` in tests.
 - This is separate from `output.Sink` — the logger is for internal diagnostics, the sink is for user-facing output.
 
 # Configuration
 
 Uses Viper with TOML format. lstk uses the first `config.toml` found in this order:
+
 1. `./.lstk/config.toml` (project-local)
 2. `$HOME/.config/lstk/config.toml`
 3. **macOS**: `$HOME/Library/Application Support/lstk/config.toml` / **Windows**: `%AppData%\lstk\config.toml`
@@ -58,12 +60,14 @@ Created automatically on first run with defaults. Supports emulator types (aws,
 # Emulator Setup Commands
 
 Use `lstk setup <emulator>` to set up CLI integration for an emulator type:
+
 - `lstk setup aws` — Sets up AWS CLI profile in `~/.aws/config` and `~/.aws/credentials`
 
 This naming avoids AWS-specific "profile" terminology and uses a clear verb for mutation operations.
 The deprecated `lstk config profile` command still works but points users to `lstk setup aws`.
 
 Environment variables:
+
 - `LOCALSTACK_AUTH_TOKEN` - Auth token (skips browser login if set)
 
 # Code Style
@@ -116,6 +120,7 @@ Domain code must never read from stdin or wait for user input directly. Instead:
 4. In non-interactive mode, commands requiring user input should fail early with a helpful error (e.g., "set LOCALSTACK_AUTH_TOKEN or run in interactive mode").
 
 Example flow in auth login:
+
 ```go
 responseCh := make(chan output.InputResponse, 1)
 output.EmitUserInputRequest(sink, output.UserInputRequestEvent{
@@ -138,11 +143,13 @@ case <-ctx.Done():
 # UI Development (Bubble Tea TUI)
 
 ## Structure
+
 - `internal/ui/` - Bubble Tea app model and run orchestration
 - `internal/ui/components/` - Reusable presentational components
 - `internal/ui/styles/` - Lipgloss style definitions and palette constants
 
 ## Component and Model Rules
+
 1. Keep components small and focused (single concern each).
 2. Keep UI as presentation/orchestration only; business logic stays in domain packages.
 3. Long-running work must run outside `Update()` (goroutine or command path), with UI updates sent asynchronously.
@@ -152,6 +159,7 @@ case <-ctx.Done():
 7. Keep message/history state bounded (for example, capped line buffer).
 
 ## Styling Rules
+
 - Define styles with semantic names in `internal/ui/styles/styles.go`.
 - Preserve the Nimbo palette constants (`#3F51C7`, `#5E6AD2`, `#7E88EC`) unless intentionally changing branding.
 - If changing palette constants, update/add tests to guard against accidental drift.

cmd/root.go

@@ -104,7 +104,6 @@ func Execute(ctx context.Context) error {
 }
 
 func startEmulator(ctx context.Context, rt runtime.Runtime, cfg *env.Env, tel *telemetry.Client, logger log.Logger) error {
-
 	appConfig, err := config.Get()
 	if err != nil {
 		return fmt.Errorf("failed to get config: %w", err)
@@ -211,20 +210,20 @@ func isInteractiveMode(cfg *env.Env) bool {
 const maxLogSize = 1 << 20 // 1 MB
 
 func newLogger() (log.Logger, func(), error) {
-	configDir, err := config.ConfigDir()
+	logDir, err := config.LogDir()
 	if err != nil {
-		return nil, func() {}, fmt.Errorf("resolve config directory: %w", err)
+		return nil, func() {}, fmt.Errorf("resolve log directory: %w", err)
 	}
-	if err := os.MkdirAll(configDir, 0755); err != nil {
-		return nil, func() {}, fmt.Errorf("create config directory %s: %w", configDir, err)
+	if err := os.MkdirAll(logDir, 0o755); err != nil {
+		return nil, func() {}, fmt.Errorf("create log directory %s: %w", logDir, err)
 	}
-	path := filepath.Join(configDir, "lstk.log")
+	path := filepath.Join(logDir, "lstk.log")
 	if info, err := os.Stat(path); err == nil && info.Size() > maxLogSize {
 		if err := os.Truncate(path, 0); err != nil {
 			return nil, func() {}, fmt.Errorf("truncate log file %s: %w", path, err)
 		}
 	}
-	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
+	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o600)
 	if err != nil {
 		return nil, func() {}, fmt.Errorf("open log file %s: %w", path, err)
 	}

internal/config/paths.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 )
 
@@ -14,6 +15,32 @@ const (
 	configFileName = configName + "." + configType
 )
 
+// LogDir returns the standard path for diagnostic logs.
+func LogDir() (string, error) {
+	return logDirForOS(runtime.GOOS)
+}
+
+func logDirForOS(goos string) (string, error) {
+	if goos == "windows" {
+		dir := os.Getenv("LOCALAPPDATA")
+		if dir == "" {
+			home, _ := os.UserHomeDir()
+			dir = filepath.Join(home, "AppData", "Local")
+		}
+		return filepath.Join(dir, "lstk"), nil
+	}
+
+	dir := os.Getenv("XDG_STATE_HOME")
+	if dir == "" {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return "", err
+		}
+		dir = filepath.Join(home, ".local", "state")
+	}
+	return filepath.Join(dir, "lstk"), nil
+}
+
 func ConfigFilePath() (string, error) {
 	if resolved := resolvedConfigPath(); resolved != "" {
 		absResolved, err := filepath.Abs(resolved)

internal/config/paths_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
 
 	"github.com/spf13/viper"
@@ -16,10 +17,10 @@ func TestFriendlyConfigPathRelativeForProjectLocal(t *testing.T) {
 	dir, err := filepath.EvalSymlinks(tmpDir)
 	require.NoError(t, err)
 	configDir := filepath.Join(dir, ".lstk")
-	require.NoError(t, os.MkdirAll(configDir, 0755))
+	require.NoError(t, os.MkdirAll(configDir, 0o755))
 
 	configFile := filepath.Join(configDir, "config.toml")
-	require.NoError(t, os.WriteFile(configFile, []byte("[aws]\n"), 0644))
+	require.NoError(t, os.WriteFile(configFile, []byte("[aws]\n"), 0o644))
 
 	origDir, err := os.Getwd()
 	require.NoError(t, err)
@@ -45,10 +46,10 @@ func TestFriendlyConfigPathTildeForHomeDir(t *testing.T) {
 	require.NoError(t, err)
 
 	configDir := filepath.Join(resolvedHome, ".config", "lstk")
-	require.NoError(t, os.MkdirAll(configDir, 0755))
+	require.NoError(t, os.MkdirAll(configDir, 0o755))
 
 	configFile := filepath.Join(configDir, "config.toml")
-	require.NoError(t, os.WriteFile(configFile, []byte("[aws]\n"), 0644))
+	require.NoError(t, os.WriteFile(configFile, []byte("[aws]\n"), 0o644))
 
 	t.Setenv("HOME", resolvedHome)
 
@@ -61,3 +62,36 @@ func TestFriendlyConfigPathTildeForHomeDir(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, filepath.Join("~", ".config", "lstk", "config.toml"), friendly)
 }
+
+func TestLogDir(t *testing.T) {
+	// Cannot run in parallel: mutates process-wide environment variables.
+
+	tmp := t.TempDir()
+	resolvedTmp, err := filepath.EvalSymlinks(tmp)
+	require.NoError(t, err)
+
+	if runtime.GOOS == "windows" {
+		t.Setenv("LOCALAPPDATA", resolvedTmp)
+
+		path, err := LogDir()
+		require.NoError(t, err)
+		require.Equal(t, filepath.Join(resolvedTmp, "lstk"), path)
+	} else {
+		// Test XDG_STATE_HOME preference
+		t.Setenv("XDG_STATE_HOME", resolvedTmp)
+
+		path, err := LogDir()
+		require.NoError(t, err)
+		require.Equal(t, filepath.Join(resolvedTmp, "lstk"), path)
+
+		// Test fallback to HOME
+		t.Setenv("XDG_STATE_HOME", "")
+		fakeHome := t.TempDir()
+		resolvedHome, _ := filepath.EvalSymlinks(fakeHome)
+		t.Setenv("HOME", resolvedHome)
+
+		path, err = LogDir()
+		require.NoError(t, err)
+		require.Equal(t, filepath.Join(resolvedHome, ".local", "state", "lstk"), path)
+	}
+}