instructure/canvas-lms · error · GraphQL::ExecutionError

Only one assessor is allowed when creating reciprocal rules

Error message

Only one assessor is allowed when creating reciprocal rules

What it means

Raised by validate_id_arrays! in AllocationRuleBase when the mutation input has reciprocal: true but the assessor_ids array contains more than one ID. Reciprocal allocation rules pair exactly one assessor with exactly one assessee, so multiple assessors are rejected. The error surfaces as a GraphQL ExecutionError on the mutation result.

Solutions

1. Send only one assessor ID when reciprocal: true.
2. Split multiple pairs into separate mutation calls (one per reciprocal pair).
3. Omit reciprocal: true if multiple assessors are actually intended.
4. Add client-side validation limiting assessorIds to length 1 when the reciprocal checkbox is on.

Example fix

// before
{ reciprocal: true, assessorIds: ["11", "12"], assesseeIds: ["21"] }
// after (one pair per call)
{ reciprocal: true, assessorIds: ["11"], assesseeIds: ["21"] }
{ reciprocal: true, assessorIds: ["12"], assesseeIds: ["21"] }

if (input.reciprocal && input.assessorIds.length > 1) {
  throw new Error('Reciprocal rules require exactly one assessor');
}

try {
  await createAllocationRules(input);
} catch (e) {
  if (e.message.includes('Only one assessor is allowed when creating reciprocal rules')) {
    // fall back to per-pair mutation calls
  }
}

When it happens

Trigger: Calling an allocation-rule create mutation with input { reciprocal: true, assessorIds: [id1, id2, ...], assesseeIds: [x] } — i.e. reciprocal flag set with assessor_ids.length > 1.

Common situations: A frontend batch-creates reciprocal rules in one call instead of one call per pair; copying a bulk-assessor payload from a non-reciprocal flow and adding reciprocal: true; misunderstanding that reciprocal means pair-wise and must be created one pair at a time.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Only one assessee is allowed when creating reciprocal rules
• A maximum of 50 assessees can be provided at once
• A maximum of 50 assessors can be provided at once
• At least one assessee is required
• At least one assessor is required

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/0ada1ddb5ea976d8. Report an issue: GitHub.

Appendix: source

Thrown at app/graphql/mutations/allocation_rule_base.rb:86

    field :allocation_rules, [Types::AllocationRuleType], null: true

    protected

    def validate_feature_flag!(course)
      unless course.feature_enabled?(:peer_review_allocation_and_grading)
        raise GraphQL::ExecutionError, I18n.t("peer_review_allocation_and_grading feature flag is not enabled for this course")
      end
    end

    def validate_id_arrays!(input)
      assessor_ids = input[:assessor_ids]
      assessee_ids = input[:assessee_ids]
      applies_to_assessor = input[:applies_to_assessor]
      reciprocal = input[:reciprocal]

      if reciprocal
        if assessor_ids.length > 1
          raise GraphQL::ExecutionError, I18n.t("Only one assessor is allowed when creating reciprocal rules")
        end
        if assessee_ids.length > 1
          raise GraphQL::ExecutionError, I18n.t("Only one assessee is allowed when creating reciprocal rules")
        end
      elsif applies_to_assessor
        if assessor_ids.length > 1
          raise GraphQL::ExecutionError, I18n.t("Only one assessor is allowed when rule applies to assessor")
        end
      elsif assessee_ids.length > 1
        raise GraphQL::ExecutionError, I18n.t("Only one assessee is allowed when rule applies to assessee")
      end

      if assessor_ids.empty?
        raise GraphQL::ExecutionError, I18n.t("At least one assessor is required")
      end
      if assessee_ids.empty?
        raise GraphQL::ExecutionError, I18n.t("At least one assessee is required")
      end

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