infiniflow/ragflow · error · listOpPanic

ListOperations: tail requires n to be within the valid range

Error message

ListOperations: tail requires n to be within the valid range in strict mode, got %d

What it means

opTail panics in strict mode when n < 1 or n > len(items). The tail operation returns the last n items and strict mode enforces 1 <= n <= len(items); anything outside that range panics via strictRangePanic instead of returning empty or clamping.

Source

Thrown at internal/agent/component/list_operations.go:432

			panic(strictRangePanic("head", n))
		}
		return append([]any{}, items[:n]...)
	}
	if n < 1 {
		return []any{}
	}
	if n > len(items) {
		n = len(items)
	}
	return append([]any{}, items[:n]...)
}

// opTail: last n items. n < 1 → empty. Strict: 1 ≤ n ≤ len(items).
func (l *ListOperationsComponent) opTail(items []any) []any {
	n := l.param.N
	if l.param.Strict {
		if n < 1 || n > len(items) {
			panic(strictRangePanic("tail", n))
		}
		return append([]any{}, items[len(items)-n:]...)
	}
	if n < 1 {
		return []any{}
	}
	if n > len(items) {
		n = len(items)
	}
	return append([]any{}, items[len(items)-n:]...)
}

// opFilter: keep items whose _norm(v) matches the filter rule.
func (l *ListOperationsComponent) opFilter(items []any) []any {
	op, _ := l.param.Filter["operator"].(string)
	val, _ := l.param.Filter["value"].(string)
	out := make([]any, 0, len(items))
	for _, item := range items {

View on GitHub (pinned to 554fb1133a)

Solutions

1. Set N within 1..len(items) — e.g. n: 1 to take only the last item
2. Guard dynamic N values and empty upstream lists before tail executes
3. Disable strict mode if clamped/empty results are acceptable for edge cases

Example fix

# before
operation: tail
strict: true
n: 10       # list has 4 items -> panic

# after
operation: tail
strict: true
n: 4        # whole list; n:1 for last item only

if op == "tail" && strict && (n < 1 || n > len(items)) {
    return fmt.Errorf("tail requires 1 <= n <= %d, got %d", len(items), n)
}

When it happens

Trigger: ListOperations with operation tail, Strict: true, and N set to 0, a negative number, or a value larger than the input list length.

Common situations: Unset N defaulting to 0; dynamic counts that hit 0 on short upstream lists; fixed tail sizes assumed to fit any list but applied to filtered or split data.

Related errors

• ListOperations: head requires n to be within the valid range
• ListOperations: nth requires n to be within the valid range
• should be a numeric number between 0 and 1 exclusively
• {operation} requires n to be within the valid range in stric
• failed to initialize logger: {err}

AI-assisted analysis of infiniflow/ragflow@554fb1133a (2026-08-15). Data as JSON: /api/errors/0f922411b1690900. Report an issue: GitHub.