diff --git a/internal/cmd/sling_schedule.go b/internal/cmd/sling_schedule.go
index 318a606e28..52f442a31e 100644
--- a/internal/cmd/sling_schedule.go
+++ b/internal/cmd/sling_schedule.go
@@ -11,6 +11,7 @@ import (
 	"github.com/steveyegge/gastown/internal/beads"
 	"github.com/steveyegge/gastown/internal/config"
 	"github.com/steveyegge/gastown/internal/events"
+	"github.com/steveyegge/gastown/internal/rig"
 	"github.com/steveyegge/gastown/internal/scheduler/capacity"
 	"github.com/steveyegge/gastown/internal/style"
 	"github.com/steveyegge/gastown/internal/workspace"
@@ -252,8 +253,16 @@ func resolveRigForBead(townRoot, beadID string) string {
 }
 
 // resolveFormula determines the formula name from user flags and rig settings.
-// It checks the rig's workflow.default_formula setting before falling back to
-// the hardcoded "mol-polecat-work" default.
+// Resolution order:
+//  1. Explicit --formula flag
+//  2. Rig property layers (wisp → bead → system default "mol-polecat-work")
+//  3. Rig settings file (workflow.default_formula in settings/config.json)
+//  4. Hardcoded fallback "mol-polecat-work"
+//
+// The property layers are the primary mechanism, supporting:
+//
+//	gt rig config set <rig> default_formula mol-evolve         # wisp layer
+//	gt rig config set <rig> default_formula mol-evolve --global # bead layer
 func resolveFormula(explicit string, hookRawBead bool, townRoot, rigName string) string {
 	if hookRawBead {
 		return ""
@@ -261,7 +270,17 @@ func resolveFormula(explicit string, hookRawBead bool, townRoot, rigName string)
 	if explicit != "" {
 		return explicit
 	}
-	// Check rig's default_formula setting (issue gt-boc).
+	// Check rig property layers: wisp → bead → system default (issue gt-y18).
+	if townRoot != "" && rigName != "" {
+		r := &rig.Rig{
+			Name: rigName,
+			Path: filepath.Join(townRoot, rigName),
+		}
+		if df := r.GetStringConfig("default_formula"); df != "" {
+			return df
+		}
+	}
+	// Fallback: check rig settings file (legacy path, issue gt-boc).
 	if townRoot != "" && rigName != "" {
 		rigPath := filepath.Join(townRoot, rigName)
 		if df := config.GetDefaultFormula(rigPath); df != "" {
diff --git a/internal/cmd/sling_schedule_test.go b/internal/cmd/sling_schedule_test.go
index f7f296e554..43bf3e3f89 100644
--- a/internal/cmd/sling_schedule_test.go
+++ b/internal/cmd/sling_schedule_test.go
@@ -2,7 +2,10 @@ package cmd
 
 import (
 	"os"
+	"path/filepath"
 	"testing"
+
+	"github.com/steveyegge/gastown/internal/wisp"
 )
 
 // TestAreScheduledFailClosed verifies that areScheduled fails closed when
@@ -40,3 +43,78 @@ func TestAreScheduledEmptyInput(t *testing.T) {
 		t.Errorf("areScheduled([]) should return empty map, got %d entries", len(result))
 	}
 }
+
+// TestResolveFormula verifies formula resolution precedence:
+// explicit flag > wisp layer > bead layer > system default > settings file > hardcoded fallback.
+func TestResolveFormula(t *testing.T) {
+	t.Parallel()
+
+	t.Run("explicit flag wins", func(t *testing.T) {
+		t.Parallel()
+		got := resolveFormula("mol-evolve", false, "/tmp/nonexistent", "myrig")
+		if got != "mol-evolve" {
+			t.Errorf("got %q, want %q", got, "mol-evolve")
+		}
+	})
+
+	t.Run("hookRawBead returns empty", func(t *testing.T) {
+		t.Parallel()
+		got := resolveFormula("mol-evolve", true, "/tmp/nonexistent", "myrig")
+		if got != "" {
+			t.Errorf("got %q, want empty", got)
+		}
+	})
+
+	t.Run("system default mol-polecat-work", func(t *testing.T) {
+		t.Parallel()
+		tmpDir := t.TempDir()
+		rigName := "testrig"
+		_ = os.MkdirAll(filepath.Join(tmpDir, rigName), 0o755)
+		got := resolveFormula("", false, tmpDir, rigName)
+		if got != "mol-polecat-work" {
+			t.Errorf("got %q, want %q", got, "mol-polecat-work")
+		}
+	})
+
+	t.Run("wisp layer overrides system default", func(t *testing.T) {
+		t.Parallel()
+		tmpDir := t.TempDir()
+		rigName := "testrig"
+		_ = os.MkdirAll(filepath.Join(tmpDir, rigName), 0o755)
+
+		wispCfg := wisp.NewConfig(tmpDir, rigName)
+		if err := wispCfg.Set("default_formula", "mol-evolve"); err != nil {
+			t.Fatalf("wisp set: %v", err)
+		}
+
+		got := resolveFormula("", false, tmpDir, rigName)
+		if got != "mol-evolve" {
+			t.Errorf("got %q, want %q", got, "mol-evolve")
+		}
+	})
+
+	t.Run("explicit flag overrides wisp layer", func(t *testing.T) {
+		t.Parallel()
+		tmpDir := t.TempDir()
+		rigName := "testrig"
+		_ = os.MkdirAll(filepath.Join(tmpDir, rigName), 0o755)
+
+		wispCfg := wisp.NewConfig(tmpDir, rigName)
+		if err := wispCfg.Set("default_formula", "mol-evolve"); err != nil {
+			t.Fatalf("wisp set: %v", err)
+		}
+
+		got := resolveFormula("mol-custom", false, tmpDir, rigName)
+		if got != "mol-custom" {
+			t.Errorf("got %q, want %q", got, "mol-custom")
+		}
+	})
+
+	t.Run("empty rigName falls back to hardcoded default", func(t *testing.T) {
+		t.Parallel()
+		got := resolveFormula("", false, "/tmp/nonexistent", "")
+		if got != "mol-polecat-work" {
+			t.Errorf("got %q, want %q", got, "mol-polecat-work")
+		}
+	})
+}
diff --git a/internal/rig/config.go b/internal/rig/config.go
index 8ff7f2149a..0d680e3bc7 100644
--- a/internal/rig/config.go
+++ b/internal/rig/config.go
@@ -38,6 +38,7 @@ var SystemDefaults = map[string]interface{}{
 	"priority_adjustment":     0,
 	"dnd":                     false,
 	"polecat_branch_template": "", // Empty = use default behavior (polecat/{name}/...)
+	"default_formula":         "mol-polecat-work",
 }
 
 // StackingKeys defines which keys use stacking semantics (values add up).