fix(config): reject ambiguous checklist comma format and propagate encode errors

ParseChecklistValue now accepts JSON arrays or single bare values and rejects
  legacy comma-separated input. Empty JSON segments are validated consistently,
  and FormatChecklistValue returns marshal errors instead of an empty string

service/internal/config/checklist.go

@@ -7,7 +7,7 @@ import (
 )
 
 // ParseChecklistValue parses a checklist argument wire value.
-// New values are JSON arrays; legacy comma-separated values are still accepted.
+// Values must be JSON arrays, or a single choice without commas.
 func ParseChecklistValue(value string) ([]string, error) {
 	trimmed := strings.TrimSpace(value)
 	if trimmed == "" {
@@ -18,7 +18,11 @@ func ParseChecklistValue(value string) ([]string, error) {
 		return parseJSONChecklistValue(trimmed)
 	}
 
-	return parseLegacyChecklistValue(value)
+	if strings.Contains(trimmed, ",") {
+		return nil, fmt.Errorf("checklist value uses legacy comma-separated format; use a JSON array instead")
+	}
+
+	return []string{trimmed}, nil
 }
 
 func parseJSONChecklistValue(value string) ([]string, error) {
@@ -27,34 +31,25 @@ func parseJSONChecklistValue(value string) ([]string, error) {
 		return nil, fmt.Errorf("invalid checklist JSON value: %w", err)
 	}
 
-	return values, nil
-}
-
-func parseLegacyChecklistValue(value string) ([]string, error) {
-	segments := strings.Split(value, ",")
-	values := make([]string, 0, len(segments))
-	for _, segment := range segments {
-		trimmedSegment := strings.TrimSpace(segment)
-		if trimmedSegment == "" {
+	for _, segment := range values {
+		if strings.TrimSpace(segment) == "" {
 			return nil, fmt.Errorf("checklist value contains an empty segment")
 		}
-
-		values = append(values, trimmedSegment)
 	}
 
 	return values, nil
 }
 
 // FormatChecklistValue serializes selected checklist values for API transport.
-func FormatChecklistValue(values []string) string {
+func FormatChecklistValue(values []string) (string, error) {
 	if len(values) == 0 {
-		return ""
+		return "", nil
 	}
 
 	encoded, err := json.Marshal(values)
 	if err != nil {
-		return ""
+		return "", fmt.Errorf("encoding checklist value: %w", err)
 	}
 
-	return string(encoded)
+	return string(encoded), nil
 }

service/internal/config/checklist_test.go

@@ -19,25 +19,40 @@ func TestParseChecklistValueJSON(t *testing.T) {
 	assert.Equal(t, []string{"kitchen,bedroom", "hallway"}, values)
 }
 
-func TestParseChecklistValueLegacyCommaSeparated(t *testing.T) {
+func TestParseChecklistValueSingleValue(t *testing.T) {
 	t.Parallel()
 
-	values, err := ParseChecklistValue("documents, photos")
+	values, err := ParseChecklistValue("documents")
 	require.NoError(t, err)
-	assert.Equal(t, []string{"documents", "photos"}, values)
+	assert.Equal(t, []string{"documents"}, values)
 }
 
-func TestParseChecklistValueRejectsEmptyLegacySegment(t *testing.T) {
+func TestParseChecklistValueRejectsLegacyCommaSeparated(t *testing.T) {
 	t.Parallel()
 
-	_, err := ParseChecklistValue("documents,,photos")
+	_, err := ParseChecklistValue("documents, photos")
+	require.Error(t, err)
+}
+
+func TestParseChecklistValueRejectsEmptyJSONSegment(t *testing.T) {
+	t.Parallel()
+
+	_, err := ParseChecklistValue(`["documents","","photos"]`)
 	require.Error(t, err)
 }
 
 func TestFormatChecklistValueJSON(t *testing.T) {
 	t.Parallel()
 
-	assert.Equal(t, `["documents","photos"]`, FormatChecklistValue([]string{"documents", "photos"}))
-	assert.Equal(t, `["kitchen,bedroom"]`, FormatChecklistValue([]string{"kitchen,bedroom"}))
-	assert.Empty(t, FormatChecklistValue(nil))
+	encoded, err := FormatChecklistValue([]string{"documents", "photos"})
+	require.NoError(t, err)
+	assert.Equal(t, `["documents","photos"]`, encoded)
+
+	encoded, err = FormatChecklistValue([]string{"kitchen,bedroom"})
+	require.NoError(t, err)
+	assert.Equal(t, `["kitchen,bedroom"]`, encoded)
+
+	encoded, err = FormatChecklistValue(nil)
+	require.NoError(t, err)
+	assert.Empty(t, encoded)
 }

service/internal/executor/arguments.go

@@ -499,16 +499,21 @@ func mangleChecklistValue(arg *config.ActionArgument, value string, actionTitle
 		return value
 	}
 
-	return mangleChecklistSegments(arg, segments, actionTitle)
+	return mangleChecklistSegments(arg, segments, value, actionTitle)
 }
 
-func mangleChecklistSegments(arg *config.ActionArgument, segments []string, actionTitle string) string {
+func mangleChecklistSegments(arg *config.ActionArgument, segments []string, fallback string, actionTitle string) string {
 	mangled := make([]string, len(segments))
 	for i, segment := range segments {
 		mangled[i] = mangleChecklistSegment(arg, segment, actionTitle)
 	}
 
-	return config.FormatChecklistValue(mangled)
+	formatted, err := config.FormatChecklistValue(mangled)
+	if err != nil {
+		return fallback
+	}
+
+	return formatted
 }
 
 func mangleChecklistSegment(arg *config.ActionArgument, segment string, actionTitle string) string {

service/internal/executor/arguments_test.go

@@ -136,10 +136,10 @@ func TestValidateArgumentChecklistSelections(t *testing.T) {
 	err := ValidateArgument(&arg, "documents", &action)
 	assert.Nil(t, err)
 
-	err = ValidateArgument(&arg, "documents,photos", &action)
+	err = ValidateArgument(&arg, `["documents","photos"]`, &action)
 	assert.Nil(t, err)
 
-	err = ValidateArgument(&arg, "documents,unknown", &action)
+	err = ValidateArgument(&arg, `["documents","unknown"]`, &action)
 	assert.NotNil(t, err)
 }
 
@@ -149,7 +149,7 @@ func TestValidateArgumentChecklistTitleMangling(t *testing.T) {
 	arg := checklistTestArg()
 	action := config.Action{Title: "Test checklist title mangling"}
 
-	err := ValidateArgument(&arg, "Documents,Photos", &action)
+	err := ValidateArgument(&arg, `["Documents","Photos"]`, &action)
 	assert.Nil(t, err)
 }
 
@@ -186,7 +186,7 @@ func TestValidateArgumentChecklistRejectsEmptySegment(t *testing.T) {
 	arg := checklistTestArg()
 	action := config.Action{Title: "Test checklist empty segment"}
 
-	err := ValidateArgument(&arg, "documents,,photos", &action)
+	err := ValidateArgument(&arg, `["documents","","photos"]`, &action)
 	assert.NotNil(t, err)
 }
 
@@ -195,10 +195,10 @@ func TestMangleArgumentValueChecklist(t *testing.T) {
 
 	arg := checklistTestArg()
 
-	out := MangleArgumentValue(&arg, "Documents,Music", "Test action")
+	out := MangleArgumentValue(&arg, `["Documents","Music"]`, "Test action")
 	assert.Equal(t, `["documents","music"]`, out)
 
-	out = MangleArgumentValue(&arg, "documents,photos", "Test action")
+	out = MangleArgumentValue(&arg, `["documents","photos"]`, "Test action")
 	assert.Equal(t, `["documents","photos"]`, out)
 }
 
@@ -225,10 +225,10 @@ func TestValidateArgumentChecklistEntitySelections(t *testing.T) {
 	err := ValidateArgument(&arg, "attic", &action)
 	assert.Nil(t, err)
 
-	err = ValidateArgument(&arg, "attic,basement", &action)
+	err = ValidateArgument(&arg, `["attic","basement"]`, &action)
 	assert.Nil(t, err)
 
-	err = ValidateArgument(&arg, "attic,unknown", &action)
+	err = ValidateArgument(&arg, `["attic","unknown"]`, &action)
 	assert.NotNil(t, err)
 }
 
@@ -247,7 +247,7 @@ func TestMangleArgumentValueChecklistEntityTitles(t *testing.T) {
 		},
 	}
 
-	out := MangleArgumentValue(&arg, "attic room,basement room", "Test checklist entity titles")
+	out := MangleArgumentValue(&arg, `["attic room","basement room"]`, "Test checklist entity titles")
 	assert.Equal(t, `["attic","basement"]`, out)
 }
 

service/internal/executor/log_arguments_test.go

@@ -92,7 +92,7 @@ func TestStorableArgumentsFromRequestStoresMangledChecklistValue(t *testing.T) {
 		},
 	}
 	req.Arguments = map[string]string{
-		"directories": "Documents,Photos",
+		"directories": `["Documents","Photos"]`,
 	}
 
 	mangleInvalidArgumentValues(req)