operation %d: modify operation missing required id field

Error message

operation %d: modify operation missing required id field

What it means

For Op == SubtaskOpModify, applySubtaskOperations requires an ID identifying which subtask to change. A modify operation without ID is rejected before any field is applied, since modifying 'the current subtask' implicitly is ambiguous.

Source

Thrown at backend/pkg/providers/subtask_patch.go:73

		switch op.Op {
		case tools.SubtaskOpRemove:
			if op.ID == nil {
				err := fmt.Errorf("operation %d: remove operation missing required id field", i)
				opLogger.Error(err.Error())
				return nil, err
			}
			if _, ok := idToIdx[*op.ID]; !ok {
				err := fmt.Errorf("operation %d: subtask with id %d not found for removal", i, *op.ID)
				opLogger.Error(err.Error())
				return nil, err
			}
			removed[*op.ID] = true
			opLogger.WithField("subtask_id", *op.ID).Debug("marked subtask for removal")

		case tools.SubtaskOpModify:
			if op.ID == nil {
				err := fmt.Errorf("operation %d: modify operation missing required id field", i)
				opLogger.Error(err.Error())
				return nil, err
			}
			if op.Title == "" && op.Description == "" {
				err := fmt.Errorf("operation %d: modify operation missing both title and description fields", i)
				opLogger.Error(err.Error())
				return nil, err
			}
			idx, ok := idToIdx[*op.ID]
			if !ok {
				err := fmt.Errorf("operation %d: subtask with id %d not found for modification", i, *op.ID)
				opLogger.Error(err.Error())
				return nil, err
			}
			// Only update fields that are provided
			if op.Title != "" {
				result[idx].Title = op.Title
				opLogger.WithField("new_title", op.Title).Debug("updated subtask title")

View on GitHub (pinned to ea665308ba)

Solutions

Retry the LLM call; malformed output is frequently transient.
Make "id" required in the tool/JSON schema for modify operations.
Add explicit prompt instructions: every modify must include the target subtask id.
Reduce patch size to avoid truncation dropping fields.

Example fix

// before
{"op":"modify","description":"Use nmap -sV"} // missing id
// after
{"op":"modify","id":1,"description":"Use nmap -sV"}

Defensive patterns

Strategy: validation

Validate before calling

for i, op := range ops {
    if op.Op == tools.SubtaskOpModify && op.ID == nil {
        return fmt.Errorf("op %d: modify requires id", i)
    }
}

Type guard

func isTargetedModify(op tools.SubtaskOperation) bool {
    return op.Op == tools.SubtaskOpModify && op.ID != nil
}

Try / catch

patched, err := applySubtaskOperations(ctx, logger, ops, subtasks)
if err != nil && strings.Contains(err.Error(), "modify operation missing required id") {
    return retryRefinerWithSchemaReminder(ctx)
}

Prevention

Require id in the modify-op JSON schema.
Prompt the model to always target a specific subtask id for modify.
Check for output truncation if fields are systematically missing.

When it happens

Trigger: LLM-generated patch contains {"op":"modify","title":"..."} with no "id"; validation in applySubtaskOperations (via patchAssistantFlowSubtasks / performSubtasksRefiner) aborts the patch.

Common situations: Model omitting required fields; prompt/tool schema not marking id as required for modify; truncation of long JSON outputs dropping fields.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of vxcontrol/pentagi@ea665308ba (2026-09-01). Data as JSON: /api/errors/b3760ba26301742e. Report an issue: GitHub.