diff --git a/internal/daemon/daemon.go b/internal/daemon/daemon.go
index 91f73beaf6..375c589dce 100755
--- a/internal/daemon/daemon.go
+++ b/internal/daemon/daemon.go
@@ -165,7 +165,11 @@ func New(config *Config) (*Daemon, error) {
 		logger.Printf("Warning: failed to initialize town registry: %v", err)
 	}
 
-	// Set GT_TOWN_ROOT in tmux global environment so run-shell subprocesses
+	// Set GT_TOWN_ROOT in the daemon process env so Go code (e.g.,
+	// sessionPrefixPattern) can read it without relying on GT_ROOT.
+	os.Setenv("GT_TOWN_ROOT", config.TownRoot)
+
+	// Also set GT_TOWN_ROOT in tmux global environment so run-shell subprocesses
 	// (e.g., gt cycle next/prev) can find the workspace even when CWD is $HOME.
 	// Non-fatal: tmux server may not be running yet — daemon creates sessions shortly.
 	t := tmux.NewTmux()
diff --git a/internal/tmux/tmux.go b/internal/tmux/tmux.go
index 49ff7662ea..0eb7a0cb6c 100644
--- a/internal/tmux/tmux.go
+++ b/internal/tmux/tmux.go
@@ -3426,6 +3426,9 @@ var safePrefixRe = regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9-]{0,19}$`)
 func sessionPrefixPattern() string {
 	seen := map[string]bool{"hq": true, "gt": true} // always include HQ + gastown fallback
 	townRoot := os.Getenv("GT_ROOT")
+	if townRoot == "" {
+		townRoot = os.Getenv("GT_TOWN_ROOT")
+	}
 	if townRoot != "" {
 		for _, p := range config.AllRigPrefixes(townRoot) {
 			if safePrefixRe.MatchString(p) {
diff --git a/internal/tmux/tmux_test.go b/internal/tmux/tmux_test.go
index 3e1d86ddde..cb14926c88 100644
--- a/internal/tmux/tmux_test.go
+++ b/internal/tmux/tmux_test.go
@@ -2146,6 +2146,38 @@ func TestSessionPrefixPattern_WithTownRoot(t *testing.T) {
 	}
 }
 
+func TestSessionPrefixPattern_FallsBackToGTTownRoot(t *testing.T) {
+	// When GT_ROOT is empty but GT_TOWN_ROOT is set, sessionPrefixPattern
+	// should use GT_TOWN_ROOT to discover rig prefixes.
+	townRoot := os.Getenv("GT_ROOT")
+	if townRoot == "" {
+		townRoot = os.Getenv("GT_TOWN_ROOT")
+	}
+	if townRoot == "" {
+		t.Skip("neither GT_ROOT nor GT_TOWN_ROOT set; skipping")
+	}
+
+	// Clear GT_ROOT, set GT_TOWN_ROOT — simulates daemon startup env.
+	t.Setenv("GT_ROOT", "")
+	t.Setenv("GT_TOWN_ROOT", townRoot)
+
+	pattern := sessionPrefixPattern()
+	if !strings.Contains(pattern, "gt") {
+		t.Errorf("pattern %q missing 'gt'", pattern)
+	}
+	if !strings.Contains(pattern, "hq") {
+		t.Errorf("pattern %q missing 'hq'", pattern)
+	}
+	// With a real rigs.json via GT_TOWN_ROOT, we expect more than just gt+hq.
+	// At minimum there should be 3+ prefixes in a multi-rig town.
+	inner := strings.TrimPrefix(pattern, "^(")
+	inner = strings.TrimSuffix(inner, ")-")
+	prefixes := strings.Split(inner, "|")
+	if len(prefixes) < 3 {
+		t.Errorf("expected at least 3 prefixes via GT_TOWN_ROOT fallback, got %d: %v", len(prefixes), prefixes)
+	}
+}
+
 func TestZombieStatusString(t *testing.T) {
 	t.Parallel()
 	tests := []struct {