operation %d: modify requires at least title or description

Error message

operation %d: modify requires at least title or description

What it means

For SubtaskOpModify, Validate requires at least one of Title or Description to be non-empty (a modify that changes nothing is rejected). This error fires when an ID is supplied but both fields are empty.

Source

Thrown at backend/pkg/tools/args.go:337

	for i, op := range sp.Operations {
		switch op.Op {
		case SubtaskOpAdd:
			if op.Title == "" {
				return fmt.Errorf("operation %d: add requires title", i)
			}
			if op.Description == "" {
				return fmt.Errorf("operation %d: add requires description", i)
			}
		case SubtaskOpRemove:
			if op.ID == nil {
				return fmt.Errorf("operation %d: remove requires id", i)
			}
		case SubtaskOpModify:
			if op.ID == nil {
				return fmt.Errorf("operation %d: modify requires id", i)
			}
			if op.Title == "" && op.Description == "" {
				return fmt.Errorf("operation %d: modify requires at least title or description", i)
			}
		case SubtaskOpReorder:
			if op.ID == nil {
				return fmt.Errorf("operation %d: reorder requires id", i)
			}
		default:
			return fmt.Errorf("operation %d: unknown operation type %q", i, op.Op)
		}
	}
	return nil
}

type Bool bool

func (b *Bool) UnmarshalJSON(data []byte) error {
	sdata := strings.Trim(strings.ToLower(string(data)), "' \"\n\r\t")
	switch sdata {
	case "true":

View on GitHub (pinned to ea665308ba)

Solutions

Provide the new title or description the modify should apply.
Drop no-op modify operations from the patch before validation.
Use remove+add instead if the intent was to replace a subtask entirely.

Example fix

// before
ops := []SubtaskOperation{{Op: SubtaskOpModify, ID: int64Ptr(7)}}
// after
ops := []SubtaskOperation{{Op: SubtaskOpModify, ID: int64Ptr(7), Description: "Escalate privileges after initial access"}}

Defensive patterns

Strategy: validation

Validate before calling

for i, op := range ops {
    if op.Op == "modify" && op.Title == "" && op.Description == "" {
        return fmt.Errorf("op %d: modify needs title or description", i)
    }
}

Type guard

func isMeaningfulModify(op SubtaskOperation) bool {
    return op.Op != SubtaskOpModify || op.Title != "" || op.Description != ""
}

Try / catch

if err := patch.Validate(); err != nil {
    if strings.Contains(err.Error(), "modify requires at least title or description") {
        // drop the no-op operation or fill in the intended change
    }
}

Prevention

Strip no-op modify operations before applying a patch.
Require at least one changed field when building modify ops programmatically.
Make prompts forbid empty modify operations.
Diff current vs desired subtask content and only emit modify ops with real changes.

When it happens

Trigger: Patch operation {"op":"modify","id":7} with empty/omitted title and description, via patch_flow_subtasks or SubtaskPatch.Validate.

Common situations: LLM emits no-op modify entries; code that copies an operation struct and blanks both fields; attempting to 'touch' a subtask to trigger refresh.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of vxcontrol/pentagi@ea665308ba (2026-09-01). Data as JSON: /api/errors/6b2220f7dba10205. Report an issue: GitHub.