feat: implement account management for multi-account Claude Code (gt-3133)

Adds support for managing multiple Claude Code accounts in Gas Town:

- accounts.json config parsing in mayor/ directory
- gt account list/add/default commands
- GT_ACCOUNT env var support with priority resolution
- --account flag on gt spawn and gt crew at commands
- CLAUDE_CONFIG_DIR injection into tmux sessions

Priority order: GT_ACCOUNT env var > --account flag > default from config

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/design/account-management.md

@@ -34,24 +34,27 @@ Each registered account gets its own config directory:
 
 ### Town Configuration
 
-File: `~/gt/mayor/accounts.yaml`
+File: `~/gt/mayor/accounts.json`
 
 This follows the existing pattern where town-level config lives in `mayor/`.
 
-```yaml
-accounts:
-  yegge:
-    email: steve.yegge@gmail.com
-    description: "Personal/Gmail account"
-    config_dir: ~/.claude-accounts/yegge
-
-  ghosttrack:
-    email: steve@ghosttrack.com
-    description: "Ghost Track business account"
-    config_dir: ~/.claude-accounts/ghosttrack
-
-# Global default used when no override specified
-default: ghosttrack
+```json
+{
+  "version": 1,
+  "accounts": {
+    "yegge": {
+      "email": "steve.yegge@gmail.com",
+      "description": "Personal/Gmail account",
+      "config_dir": "~/.claude-accounts/yegge"
+    },
+    "ghosttrack": {
+      "email": "steve@ghosttrack.com",
+      "description": "Ghost Track business account",
+      "config_dir": "~/.claude-accounts/ghosttrack"
+    }
+  },
+  "default": "ghosttrack"
+}
 ```
 
 ### Environment Variable: GT_ACCOUNT
@@ -196,7 +199,7 @@ claude  # Login as ghosttrack
 
 ### Phase 1: Basic Support
 
-- Add `accounts.yaml` parsing
+- Add `accounts.json` parsing
 - Add `gt account` subcommands
 - Wire up `GT_ACCOUNT` env var in spawn
 

internal/cmd/account.go

@@ -0,0 +1,263 @@
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"sort"
+
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/config"
+	"github.com/steveyegge/gastown/internal/constants"
+	"github.com/steveyegge/gastown/internal/style"
+	"github.com/steveyegge/gastown/internal/workspace"
+)
+
+// Account command flags
+var (
+	accountJSON        bool
+	accountEmail       string
+	accountDescription string
+)
+
+var accountCmd = &cobra.Command{
+	Use:   "account",
+	Short: "Manage Claude Code accounts",
+	Long: `Manage multiple Claude Code accounts for Gas Town.
+
+This enables switching between accounts (e.g., personal vs work) with
+easy account selection per spawn or globally.
+
+Commands:
+  gt account list              List registered accounts
+  gt account add <handle>      Add a new account
+  gt account default <handle>  Set the default account
+  gt account status            Show current account info`,
+}
+
+var accountListCmd = &cobra.Command{
+	Use:   "list",
+	Short: "List registered accounts",
+	Long: `List all registered Claude Code accounts.
+
+Shows account handles, emails, and which is the default.
+
+Examples:
+  gt account list           # Text output
+  gt account list --json    # JSON output`,
+	RunE: runAccountList,
+}
+
+var accountAddCmd = &cobra.Command{
+	Use:   "add <handle>",
+	Short: "Add a new account",
+	Long: `Add a new Claude Code account.
+
+Creates a config directory at ~/.claude-accounts/<handle> and registers
+the account. You'll need to run 'claude' with CLAUDE_CONFIG_DIR set to
+that directory to complete the login.
+
+Examples:
+  gt account add work
+  gt account add work --email steve@company.com
+  gt account add work --email steve@company.com --desc "Work account"`,
+	Args: cobra.ExactArgs(1),
+	RunE: runAccountAdd,
+}
+
+var accountDefaultCmd = &cobra.Command{
+	Use:   "default <handle>",
+	Short: "Set the default account",
+	Long: `Set the default Claude Code account.
+
+The default account is used when no --account flag or GT_ACCOUNT env var
+is specified during spawn or attach.
+
+Examples:
+  gt account default work
+  gt account default personal`,
+	Args: cobra.ExactArgs(1),
+	RunE: runAccountDefault,
+}
+
+// AccountListItem represents an account in list output.
+type AccountListItem struct {
+	Handle      string `json:"handle"`
+	Email       string `json:"email"`
+	Description string `json:"description,omitempty"`
+	ConfigDir   string `json:"config_dir"`
+	IsDefault   bool   `json:"is_default"`
+}
+
+func runAccountList(cmd *cobra.Command, args []string) error {
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+
+	accountsPath := constants.MayorAccountsPath(townRoot)
+	cfg, err := config.LoadAccountsConfig(accountsPath)
+	if err != nil {
+		// If file doesn't exist, show empty message
+		fmt.Println("No accounts configured.")
+		fmt.Println("\nTo add an account:")
+		fmt.Println("  gt account add <handle>")
+		return nil
+	}
+
+	if len(cfg.Accounts) == 0 {
+		fmt.Println("No accounts configured.")
+		fmt.Println("\nTo add an account:")
+		fmt.Println("  gt account add <handle>")
+		return nil
+	}
+
+	// Build list items
+	var items []AccountListItem
+	for handle, acct := range cfg.Accounts {
+		items = append(items, AccountListItem{
+			Handle:      handle,
+			Email:       acct.Email,
+			Description: acct.Description,
+			ConfigDir:   acct.ConfigDir,
+			IsDefault:   handle == cfg.Default,
+		})
+	}
+
+	// Sort by handle for consistent output
+	sort.Slice(items, func(i, j int) bool {
+		return items[i].Handle < items[j].Handle
+	})
+
+	if accountJSON {
+		enc := json.NewEncoder(os.Stdout)
+		enc.SetIndent("", "  ")
+		return enc.Encode(items)
+	}
+
+	// Text output
+	fmt.Printf("%s\n\n", style.Bold.Render("Claude Code Accounts"))
+	for _, item := range items {
+		marker := "  "
+		if item.IsDefault {
+			marker = "* "
+		}
+
+		fmt.Printf("%s%s", marker, style.Bold.Render(item.Handle))
+		if item.Email != "" {
+			fmt.Printf("  %s", item.Email)
+		}
+		if item.IsDefault {
+			fmt.Printf("  %s", style.Dim.Render("(default)"))
+		}
+		fmt.Println()
+
+		if item.Description != "" {
+			fmt.Printf("    %s\n", style.Dim.Render(item.Description))
+		}
+	}
+
+	return nil
+}
+
+func runAccountAdd(cmd *cobra.Command, args []string) error {
+	handle := args[0]
+
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+
+	accountsPath := constants.MayorAccountsPath(townRoot)
+
+	// Load existing config or create new
+	cfg, err := config.LoadAccountsConfig(accountsPath)
+	if err != nil {
+		cfg = config.NewAccountsConfig()
+	}
+
+	// Check if account already exists
+	if _, exists := cfg.Accounts[handle]; exists {
+		return fmt.Errorf("account '%s' already exists", handle)
+	}
+
+	// Build config directory path
+	configDir := config.DefaultAccountsConfigDir() + "/" + handle
+
+	// Create the config directory
+	if err := os.MkdirAll(configDir, 0755); err != nil {
+		return fmt.Errorf("creating config directory: %w", err)
+	}
+
+	// Add account
+	cfg.Accounts[handle] = config.Account{
+		Email:       accountEmail,
+		Description: accountDescription,
+		ConfigDir:   configDir,
+	}
+
+	// If this is the first account, make it default
+	if cfg.Default == "" {
+		cfg.Default = handle
+	}
+
+	// Save config
+	if err := config.SaveAccountsConfig(accountsPath, cfg); err != nil {
+		return fmt.Errorf("saving accounts config: %w", err)
+	}
+
+	fmt.Printf("Added account '%s'\n", handle)
+	fmt.Printf("Config directory: %s\n", configDir)
+	fmt.Println()
+	fmt.Println("To complete login, run:")
+	fmt.Printf("  CLAUDE_CONFIG_DIR=%s claude\n", configDir)
+	fmt.Println("Then use /login to authenticate.")
+
+	return nil
+}
+
+func runAccountDefault(cmd *cobra.Command, args []string) error {
+	handle := args[0]
+
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+
+	accountsPath := constants.MayorAccountsPath(townRoot)
+	cfg, err := config.LoadAccountsConfig(accountsPath)
+	if err != nil {
+		return fmt.Errorf("loading accounts config: %w", err)
+	}
+
+	// Check if account exists
+	if _, exists := cfg.Accounts[handle]; !exists {
+		return fmt.Errorf("account '%s' not found", handle)
+	}
+
+	// Update default
+	cfg.Default = handle
+
+	// Save config
+	if err := config.SaveAccountsConfig(accountsPath, cfg); err != nil {
+		return fmt.Errorf("saving accounts config: %w", err)
+	}
+
+	fmt.Printf("Default account set to '%s'\n", handle)
+	return nil
+}
+
+func init() {
+	// Add flags
+	accountListCmd.Flags().BoolVar(&accountJSON, "json", false, "Output as JSON")
+
+	accountAddCmd.Flags().StringVar(&accountEmail, "email", "", "Account email address")
+	accountAddCmd.Flags().StringVar(&accountDescription, "desc", "", "Account description")
+
+	// Add subcommands
+	accountCmd.AddCommand(accountListCmd)
+	accountCmd.AddCommand(accountAddCmd)
+	accountCmd.AddCommand(accountDefaultCmd)
+
+	rootCmd.AddCommand(accountCmd)
+}

internal/cmd/crew.go

@@ -12,6 +12,7 @@ var (
 	crewForce   bool
 	crewNoTmux  bool
 	crewMessage string
+	crewAccount string
 )
 
 var crewCmd = &cobra.Command{
@@ -197,6 +198,7 @@ func init() {
 
 	crewAtCmd.Flags().StringVar(&crewRig, "rig", "", "Rig to use")
 	crewAtCmd.Flags().BoolVar(&crewNoTmux, "no-tmux", false, "Just print directory path")
+	crewAtCmd.Flags().StringVar(&crewAccount, "account", "", "Claude Code account handle to use (overrides default)")
 
 	crewRemoveCmd.Flags().StringVar(&crewRig, "rig", "", "Rig to use")
 	crewRemoveCmd.Flags().BoolVar(&crewForce, "force", false, "Force remove (skip safety checks)")

internal/cmd/crew_at.go

@@ -5,9 +5,12 @@ import (
 	"time"
 
 	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/config"
+	"github.com/steveyegge/gastown/internal/constants"
 	"github.com/steveyegge/gastown/internal/crew"
 	"github.com/steveyegge/gastown/internal/style"
 	"github.com/steveyegge/gastown/internal/tmux"
+	"github.com/steveyegge/gastown/internal/workspace"
 )
 
 func runCrewAt(cmd *cobra.Command, args []string) error {
@@ -52,6 +55,20 @@ func runCrewAt(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 
+	// Resolve account for Claude config
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+	accountsPath := constants.MayorAccountsPath(townRoot)
+	claudeConfigDir, accountHandle, err := config.ResolveAccountConfigDir(accountsPath, crewAccount)
+	if err != nil {
+		return fmt.Errorf("resolving account: %w", err)
+	}
+	if accountHandle != "" {
+		fmt.Printf("Using account: %s\n", accountHandle)
+	}
+
 	// Check if session exists
 	t := tmux.NewTmux()
 	sessionID := crewSessionName(r.Name, name)
@@ -70,6 +87,11 @@ func runCrewAt(cmd *cobra.Command, args []string) error {
 		_ = t.SetEnvironment(sessionID, "GT_RIG", r.Name)
 		_ = t.SetEnvironment(sessionID, "GT_CREW", name)
 
+		// Set CLAUDE_CONFIG_DIR for account selection
+		if claudeConfigDir != "" {
+			_ = t.SetEnvironment(sessionID, "CLAUDE_CONFIG_DIR", claudeConfigDir)
+		}
+
 		// Apply rig-based theming (uses config if set, falls back to hash)
 		theme := getThemeForRig(r.Name)
 		_ = t.ConfigureGasTownSession(sessionID, theme, r.Name, name, "crew")

internal/cmd/spawn.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/steveyegge/gastown/internal/config"
+	"github.com/steveyegge/gastown/internal/constants"
 	"github.com/steveyegge/gastown/internal/git"
 	"github.com/steveyegge/gastown/internal/mail"
 	"github.com/steveyegge/gastown/internal/polecat"
@@ -32,6 +33,7 @@ var (
 	spawnRig      string
 	spawnMolecule string
 	spawnForce    bool
+	spawnAccount  string
 )
 
 var spawnCmd = &cobra.Command{
@@ -71,6 +73,7 @@ func init() {
 	spawnCmd.Flags().StringVar(&spawnRig, "rig", "", "Rig name (defaults to current directory's rig)")
 	spawnCmd.Flags().StringVar(&spawnMolecule, "molecule", "", "Molecule ID to instantiate on the issue")
 	spawnCmd.Flags().BoolVar(&spawnForce, "force", false, "Force spawn even if polecat has unread mail")
+	spawnCmd.Flags().StringVar(&spawnAccount, "account", "", "Claude Code account handle to use (overrides default)")
 
 	rootCmd.AddCommand(spawnCmd)
 }
@@ -348,6 +351,16 @@ func runSpawn(cmd *cobra.Command, args []string) error {
 	}
 	fmt.Printf("%s Work assignment sent\n", style.Bold.Render("✓"))
 
+	// Resolve account for Claude config
+	accountsPath := constants.MayorAccountsPath(townRoot)
+	claudeConfigDir, accountHandle, err := config.ResolveAccountConfigDir(accountsPath, spawnAccount)
+	if err != nil {
+		return fmt.Errorf("resolving account: %w", err)
+	}
+	if accountHandle != "" {
+		fmt.Printf("Using account: %s\n", accountHandle)
+	}
+
 	// Start session
 	t := tmux.NewTmux()
 	sessMgr := session.NewManager(t, r)
@@ -359,7 +372,10 @@ func runSpawn(cmd *cobra.Command, args []string) error {
 	} else {
 		// Start new session
 		fmt.Printf("Starting session for %s/%s...\n", rigName, polecatName)
-		if err := sessMgr.Start(polecatName, session.StartOptions{}); err != nil {
+		startOpts := session.StartOptions{
+			ClaudeConfigDir: claudeConfigDir,
+		}
+		if err := sessMgr.Start(polecatName, startOpts); err != nil {
 			return fmt.Errorf("starting session: %w", err)
 		}
 	}

internal/config/loader.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -417,3 +418,150 @@ func NewMayorConfig() *MayorConfig {
 		Version: CurrentMayorConfigVersion,
 	}
 }
+
+// LoadAccountsConfig loads and validates an accounts configuration file.
+func LoadAccountsConfig(path string) (*AccountsConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("%w: %s", ErrNotFound, path)
+		}
+		return nil, fmt.Errorf("reading accounts config: %w", err)
+	}
+
+	var config AccountsConfig
+	if err := json.Unmarshal(data, &config); err != nil {
+		return nil, fmt.Errorf("parsing accounts config: %w", err)
+	}
+
+	if err := validateAccountsConfig(&config); err != nil {
+		return nil, err
+	}
+
+	return &config, nil
+}
+
+// SaveAccountsConfig saves an accounts configuration to a file.
+func SaveAccountsConfig(path string, config *AccountsConfig) error {
+	if err := validateAccountsConfig(config); err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return fmt.Errorf("creating directory: %w", err)
+	}
+
+	data, err := json.MarshalIndent(config, "", "  ")
+	if err != nil {
+		return fmt.Errorf("encoding accounts config: %w", err)
+	}
+
+	if err := os.WriteFile(path, data, 0644); err != nil {
+		return fmt.Errorf("writing accounts config: %w", err)
+	}
+
+	return nil
+}
+
+// validateAccountsConfig validates an AccountsConfig.
+func validateAccountsConfig(c *AccountsConfig) error {
+	if c.Version > CurrentAccountsVersion {
+		return fmt.Errorf("%w: got %d, max supported %d", ErrInvalidVersion, c.Version, CurrentAccountsVersion)
+	}
+	if c.Accounts == nil {
+		c.Accounts = make(map[string]Account)
+	}
+	// Validate default refers to an existing account (if set and accounts exist)
+	if c.Default != "" && len(c.Accounts) > 0 {
+		if _, ok := c.Accounts[c.Default]; !ok {
+			return fmt.Errorf("%w: default account '%s' not found in accounts", ErrMissingField, c.Default)
+		}
+	}
+	// Validate each account has required fields
+	for handle, acct := range c.Accounts {
+		if acct.ConfigDir == "" {
+			return fmt.Errorf("%w: config_dir for account '%s'", ErrMissingField, handle)
+		}
+	}
+	return nil
+}
+
+// NewAccountsConfig creates a new AccountsConfig with defaults.
+func NewAccountsConfig() *AccountsConfig {
+	return &AccountsConfig{
+		Version:  CurrentAccountsVersion,
+		Accounts: make(map[string]Account),
+	}
+}
+
+// GetAccount returns an account by handle, or nil if not found.
+func (c *AccountsConfig) GetAccount(handle string) *Account {
+	if acct, ok := c.Accounts[handle]; ok {
+		return &acct
+	}
+	return nil
+}
+
+// GetDefaultAccount returns the default account, or nil if not set.
+func (c *AccountsConfig) GetDefaultAccount() *Account {
+	if c.Default == "" {
+		return nil
+	}
+	return c.GetAccount(c.Default)
+}
+
+// ResolveAccountConfigDir resolves the CLAUDE_CONFIG_DIR for account selection.
+// Priority order:
+//  1. GT_ACCOUNT environment variable
+//  2. accountFlag (from --account command flag)
+//  3. Default account from config
+//
+// Returns empty string if no account configured or resolved.
+// Returns the handle that was resolved as second value.
+func ResolveAccountConfigDir(accountsPath, accountFlag string) (configDir, handle string, err error) {
+	// Load accounts config
+	cfg, loadErr := LoadAccountsConfig(accountsPath)
+	if loadErr != nil {
+		// No accounts configured - that's OK, return empty
+		return "", "", nil
+	}
+
+	// Priority 1: GT_ACCOUNT env var
+	if envAccount := os.Getenv("GT_ACCOUNT"); envAccount != "" {
+		acct := cfg.GetAccount(envAccount)
+		if acct == nil {
+			return "", "", fmt.Errorf("GT_ACCOUNT '%s' not found in accounts config", envAccount)
+		}
+		return expandPath(acct.ConfigDir), envAccount, nil
+	}
+
+	// Priority 2: --account flag
+	if accountFlag != "" {
+		acct := cfg.GetAccount(accountFlag)
+		if acct == nil {
+			return "", "", fmt.Errorf("account '%s' not found in accounts config", accountFlag)
+		}
+		return expandPath(acct.ConfigDir), accountFlag, nil
+	}
+
+	// Priority 3: Default account
+	if cfg.Default != "" {
+		acct := cfg.GetDefaultAccount()
+		if acct != nil {
+			return expandPath(acct.ConfigDir), cfg.Default, nil
+		}
+	}
+
+	return "", "", nil
+}
+
+// expandPath expands ~ to home directory.
+func expandPath(path string) string {
+	if strings.HasPrefix(path, "~/") {
+		home, err := os.UserHomeDir()
+		if err == nil {
+			return filepath.Join(home, path[2:])
+		}
+	}
+	return path
+}

internal/config/loader_test.go

@@ -434,3 +434,118 @@ func TestLoadMayorConfigNotFound(t *testing.T) {
 		t.Fatal("expected error for nonexistent file")
 	}
 }
+
+func TestAccountsConfigRoundTrip(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "mayor", "accounts.json")
+
+	original := NewAccountsConfig()
+	original.Accounts["yegge"] = Account{
+		Email:       "steve.yegge@gmail.com",
+		Description: "Personal account",
+		ConfigDir:   "~/.claude-accounts/yegge",
+	}
+	original.Accounts["ghosttrack"] = Account{
+		Email:       "steve@ghosttrack.com",
+		Description: "Business account",
+		ConfigDir:   "~/.claude-accounts/ghosttrack",
+	}
+	original.Default = "ghosttrack"
+
+	if err := SaveAccountsConfig(path, original); err != nil {
+		t.Fatalf("SaveAccountsConfig: %v", err)
+	}
+
+	loaded, err := LoadAccountsConfig(path)
+	if err != nil {
+		t.Fatalf("LoadAccountsConfig: %v", err)
+	}
+
+	if loaded.Version != CurrentAccountsVersion {
+		t.Errorf("Version = %d, want %d", loaded.Version, CurrentAccountsVersion)
+	}
+	if len(loaded.Accounts) != 2 {
+		t.Errorf("Accounts count = %d, want 2", len(loaded.Accounts))
+	}
+	if loaded.Default != "ghosttrack" {
+		t.Errorf("Default = %q, want 'ghosttrack'", loaded.Default)
+	}
+
+	yegge := loaded.GetAccount("yegge")
+	if yegge == nil {
+		t.Fatal("GetAccount('yegge') returned nil")
+	}
+	if yegge.Email != "steve.yegge@gmail.com" {
+		t.Errorf("yegge.Email = %q, want 'steve.yegge@gmail.com'", yegge.Email)
+	}
+
+	defAcct := loaded.GetDefaultAccount()
+	if defAcct == nil {
+		t.Fatal("GetDefaultAccount() returned nil")
+	}
+	if defAcct.Email != "steve@ghosttrack.com" {
+		t.Errorf("default.Email = %q, want 'steve@ghosttrack.com'", defAcct.Email)
+	}
+}
+
+func TestAccountsConfigValidation(t *testing.T) {
+	tests := []struct {
+		name    string
+		config  *AccountsConfig
+		wantErr bool
+	}{
+		{
+			name:    "valid empty config",
+			config:  NewAccountsConfig(),
+			wantErr: false,
+		},
+		{
+			name: "valid config with accounts",
+			config: &AccountsConfig{
+				Version: 1,
+				Accounts: map[string]Account{
+					"test": {Email: "test@example.com", ConfigDir: "~/.claude-accounts/test"},
+				},
+				Default: "test",
+			},
+			wantErr: false,
+		},
+		{
+			name: "default refers to nonexistent account",
+			config: &AccountsConfig{
+				Version: 1,
+				Accounts: map[string]Account{
+					"test": {Email: "test@example.com", ConfigDir: "~/.claude-accounts/test"},
+				},
+				Default: "nonexistent",
+			},
+			wantErr: true,
+		},
+		{
+			name: "account missing config_dir",
+			config: &AccountsConfig{
+				Version: 1,
+				Accounts: map[string]Account{
+					"test": {Email: "test@example.com"},
+				},
+			},
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validateAccountsConfig(tt.config)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("validateAccountsConfig() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func TestLoadAccountsConfigNotFound(t *testing.T) {
+	_, err := LoadAccountsConfig("/nonexistent/path.json")
+	if err == nil {
+		t.Fatal("expected error for nonexistent file")
+	}
+}

internal/config/types.go

@@ -1,7 +1,10 @@
 // Package config provides configuration types and serialization for Gas Town.
 package config
 
-import "time"
+import (
+	"os"
+	"time"
+)
 
 // TownConfig represents the main town identity (mayor/town.json).
 type TownConfig struct {
@@ -208,3 +211,27 @@ func DefaultNamepoolConfig() *NamepoolConfig {
 		MaxBeforeNumbering: 50,
 	}
 }
+
+// AccountsConfig represents Claude Code account configuration (mayor/accounts.json).
+// This enables Gas Town to manage multiple Claude Code accounts with easy switching.
+type AccountsConfig struct {
+	Version  int                `json:"version"`  // schema version
+	Accounts map[string]Account `json:"accounts"` // handle -> account details
+	Default  string             `json:"default"`  // default account handle
+}
+
+// Account represents a single Claude Code account.
+type Account struct {
+	Email       string `json:"email"`                 // account email
+	Description string `json:"description,omitempty"` // human description
+	ConfigDir   string `json:"config_dir"`            // path to CLAUDE_CONFIG_DIR
+}
+
+// CurrentAccountsVersion is the current schema version for AccountsConfig.
+const CurrentAccountsVersion = 1
+
+// DefaultAccountsConfigDir returns the default base directory for account configs.
+func DefaultAccountsConfigDir() string {
+	home, _ := os.UserHomeDir()
+	return home + "/.claude-accounts"
+}

internal/constants/constants.go

@@ -48,6 +48,9 @@ const (
 
 	// FileConfigYAML is the beads config file.
 	FileConfigYAML = "config.yaml"
+
+	// FileAccountsJSON is the accounts configuration file in mayor/.
+	FileAccountsJSON = "accounts.json"
 )
 
 // Git branch names.
@@ -154,3 +157,8 @@ func RigRuntimePath(rigPath string) string {
 func RigSettingsPath(rigPath string) string {
 	return rigPath + "/" + DirSettings
 }
+
+// MayorAccountsPath returns the path to mayor/accounts.json within a town root.
+func MayorAccountsPath(townRoot string) string {
+	return townRoot + "/" + DirMayor + "/" + FileAccountsJSON
+}

internal/session/manager.go

@@ -46,6 +46,13 @@ type StartOptions struct {
 
 	// Command overrides the default "claude" command.
 	Command string
+
+	// Account specifies the account handle to use (overrides default).
+	Account string
+
+	// ClaudeConfigDir is resolved CLAUDE_CONFIG_DIR for the account.
+	// If set, this is injected as an environment variable.
+	ClaudeConfigDir string
 }
 
 // Info contains information about a running session.
@@ -133,6 +140,11 @@ func (m *Manager) Start(polecat string, opts StartOptions) error {
 	_ = m.tmux.SetEnvironment(sessionID, "GT_RIG", m.rig.Name)
 	_ = m.tmux.SetEnvironment(sessionID, "GT_POLECAT", polecat)
 
+	// Set CLAUDE_CONFIG_DIR for account selection
+	if opts.ClaudeConfigDir != "" {
+		_ = m.tmux.SetEnvironment(sessionID, "CLAUDE_CONFIG_DIR", opts.ClaudeConfigDir)
+	}
+
 	// CRITICAL: Set beads environment for worktree polecats
 	// Polecats share the rig's beads directory (at rig root, not mayor/rig)
 	// BEADS_NO_DAEMON=1 prevents daemon from committing to wrong branch