fix: allow vars with formula-on-bead slings (#966)

internal/cmd/sling.go

@@ -131,11 +131,6 @@ func runSling(cmd *cobra.Command, args []string) error {
 	}
 	townBeadsDir := filepath.Join(townRoot, ".beads")
 
-	// --var is only for standalone formula mode, not formula-on-bead mode
-	if slingOnTarget != "" && len(slingVars) > 0 {
-		return fmt.Errorf("--var cannot be used with --on (formula-on-bead mode doesn't support variables)")
-	}
-
 	// Batch mode detection: multiple beads with rig target
 	// Pattern: gt sling gt-abc gt-def gt-ghi gastown
 	// When len(args) > 2 and last arg is a rig, sling each bead to its own polecat
@@ -191,8 +186,8 @@ func runSling(cmd *cobra.Command, args []string) error {
 	// Determine target agent (self or specified)
 	var targetAgent string
 	var targetPane string
-	var hookWorkDir string        // Working directory for running bd hook commands
+	var hookWorkDir string     // Working directory for running bd hook commands
-	var hookSetAtomically bool    // True if hook was set during polecat spawn (skip redundant update)
+	var hookSetAtomically bool // True if hook was set during polecat spawn (skip redundant update)
 
 	if len(args) > 1 {
 		target := args[1]
@@ -434,7 +429,7 @@ func runSling(cmd *cobra.Command, args []string) error {
 	if formulaName != "" {
 		fmt.Printf("  Instantiating formula %s...\n", formulaName)
 
-		result, err := InstantiateFormulaOnBead(formulaName, beadID, info.Title, hookWorkDir, townRoot, false)
+		result, err := InstantiateFormulaOnBead(formulaName, beadID, info.Title, hookWorkDir, townRoot, false, slingVars)
 		if err != nil {
 			return fmt.Errorf("instantiating formula %s: %w", formulaName, err)
 		}

internal/cmd/sling_288_test.go

@@ -120,7 +120,8 @@ exit /b 0
 	}
 
 	// Test the helper function directly
-	result, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-abc123", "Test Bug Fix", "", townRoot, false)
+	extraVars := []string{"branch=polecat/furiosa/gt-abc123"}
+	result, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-abc123", "Test Bug Fix", "", townRoot, false, extraVars)
 	if err != nil {
 		t.Fatalf("InstantiateFormulaOnBead failed: %v", err)
 	}
@@ -145,6 +146,9 @@ exit /b 0
 	if !strings.Contains(logContent, "mol wisp mol-polecat-work") {
 		t.Errorf("mol wisp command not found in log:\n%s", logContent)
 	}
+	if !strings.Contains(logContent, "--var branch=polecat/furiosa/gt-abc123") {
+		t.Errorf("extra vars not passed to wisp command:\n%s", logContent)
+	}
 	if !strings.Contains(logContent, "mol bond") {
 		t.Errorf("mol bond command not found in log:\n%s", logContent)
 	}
@@ -219,7 +223,7 @@ exit /b 0
 	_ = os.Chdir(townRoot)
 
 	// Test with skipCook=true
-	_, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-test", "Test", "", townRoot, true)
+	_, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-test", "Test", "", townRoot, true, nil)
 	if err != nil {
 		t.Fatalf("InstantiateFormulaOnBead failed: %v", err)
 	}
@@ -295,11 +299,11 @@ func TestSlingHookRawBeadFlag(t *testing.T) {
 // When formulaName is empty and target contains "/polecats/", mol-polecat-work should be applied.
 func TestAutoApplyLogic(t *testing.T) {
 	tests := []struct {
-		name           string
+		name          string
-		formulaName    string
+		formulaName   string
-		hookRawBead    bool
+		hookRawBead   bool
-		targetAgent    string
+		targetAgent   string
-		wantAutoApply  bool
+		wantAutoApply bool
 	}{
 		{
 			name:          "bare bead to polecat - should auto-apply",
@@ -416,7 +420,7 @@ exit /b 0
 	t.Cleanup(func() { _ = os.Chdir(cwd) })
 	_ = os.Chdir(townRoot)
 
-	_, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-abc123", "My Cool Feature", "", townRoot, false)
+	_, err := InstantiateFormulaOnBead("mol-polecat-work", "gt-abc123", "My Cool Feature", "", townRoot, false, nil)
 	if err != nil {
 		t.Fatalf("InstantiateFormulaOnBead: %v", err)
 	}

internal/cmd/sling_batch.go

@@ -113,7 +113,7 @@ func runBatchSling(beadIDs []string, rigName string, townBeadsDir string) error
 		beadToHook := beadID
 		attachedMoleculeID := ""
 		if formulaCooked {
-			result, err := InstantiateFormulaOnBead(formulaName, beadID, info.Title, hookWorkDir, townRoot, true)
+			result, err := InstantiateFormulaOnBead(formulaName, beadID, info.Title, hookWorkDir, townRoot, true, slingVars)
 			if err != nil {
 				fmt.Printf("  %s Could not apply formula: %v (hooking raw bead)\n", style.Dim.Render("Warning:"), err)
 			} else {

internal/cmd/sling_helpers.go

@@ -475,9 +475,10 @@ type FormulaOnBeadResult struct {
 //   - hookWorkDir: working directory for bd commands (polecat's worktree)
 //   - townRoot: the town root directory
 //   - skipCook: if true, skip cooking (for batch mode optimization where cook happens once)
+//   - extraVars: additional --var values supplied by the user
 //
 // Returns the wisp root ID which should be hooked.
-func InstantiateFormulaOnBead(formulaName, beadID, title, hookWorkDir, townRoot string, skipCook bool) (*FormulaOnBeadResult, error) {
+func InstantiateFormulaOnBead(formulaName, beadID, title, hookWorkDir, townRoot string, skipCook bool, extraVars []string) (*FormulaOnBeadResult, error) {
 	// Route bd mutations (wisp/bond) to the correct beads context for the target bead.
 	formulaWorkDir := beads.ResolveHookDir(townRoot, beadID, hookWorkDir)
 
@@ -494,7 +495,11 @@ func InstantiateFormulaOnBead(formulaName, beadID, title, hookWorkDir, townRoot
 	// Step 2: Create wisp with feature and issue variables from bead
 	featureVar := fmt.Sprintf("feature=%s", title)
 	issueVar := fmt.Sprintf("issue=%s", beadID)
-	wispArgs := []string{"--no-daemon", "mol", "wisp", formulaName, "--var", featureVar, "--var", issueVar, "--json"}
+	wispArgs := []string{"--no-daemon", "mol", "wisp", formulaName, "--var", featureVar, "--var", issueVar}
+	for _, variable := range extraVars {
+		wispArgs = append(wispArgs, "--var", variable)
+	}
+	wispArgs = append(wispArgs, "--json")
 	wispCmd := exec.Command("bd", wispArgs...)
 	wispCmd.Dir = formulaWorkDir
 	wispCmd.Env = append(os.Environ(), "GT_ROOT="+townRoot)

internal/rig/overlay.go

@@ -66,6 +66,7 @@ func EnsureGitignorePatterns(worktreePath string) error {
 		".runtime/",
 		".claude/",
 		".logs/",
+		".beads/",
 	}
 
 	// Read existing gitignore content