instructure/canvas-lms · error

Submission must be at least 5 words long

Error message

Submission must be at least 5 words long

What it means

GradeService#validate_essay_length requires the (sanitized) essay to contain at least 5 words before sending it to the external Cedar AI grader. This minimum-length guard avoids wasting grading API calls on trivially short submissions. It runs during call(), after sanitize_essay.

Solutions

1. Have the student resubmit with a longer response, or disable AI/essay grading for short-answer questions
2. Guard in the caller: text.split.size >= 5 before constructing GradeService, showing a friendly message otherwise
3. If legitimate short responses should be graded, lower the threshold or bypass GradeService for those items

Example fix

// before
GradeService.new(essay: submission.body, rubric:).call
// after
if submission.body.split.size < 5
  return { error: I18n.t('Submission must be at least 5 words long') }
end
GradeService.new(essay: submission.body, rubric:).call

raise 'too short' if essay.to_s.split.size < 5

essay.to_s.split.size >= 5

begin
  GradeService.new(essay:, rubric:, rubric_association:).call
rescue RuntimeError => e
  show_too_short_error if e.message.include?('at least 5 words')
end

When it happens

Trigger: Calling GradeService.call with an essay of fewer than 5 whitespace-separated words after sanitization; very short answers to an essay question on an assignment with AI grading enabled; a submission that shrinks below 5 words once tags/multiple spaces are stripped.

Common situations: Students submitting one-line answers to essay prompts; auto-graded practice assignments with AI grading enabled on short-answer questions; tests with stub essays shorter than 5 words.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• Peer review sub assignments cannot have a not_graded…
• Rubric criteria not descriptive enough
• A course did not pass validation
• A # user did not pass validation (user: # , # : # , error…
• A maximum of 50 assessees can be provided at once

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/b953f98cb9615e64. Report an issue: GitHub.

Appendix: source

Thrown at app/services/grade_service.rb:158

               .gsub(/<[^>]*>/, "")                                       # Remove any remaining opening tags
               .gsub(%r{</[^>]*>}, "")                                    # Remove any remaining closing tags

    # Remove any content between \&lt; and \&gt; (including the entities themselves)
    text = text.gsub(%r{\\&lt;[^&]*\\&gt;.*?\\&lt;/[^&]*\\&gt;}, "")      # Remove content between encoded opening and closing tags
               .gsub(/\\&lt;[^&]*\\&gt;/, "")                             # Remove any remaining encoded opening tags
               .gsub(%r{\\&lt;/[^&]*\\&gt;}, "")                          # Remove any remaining encoded closing tags

    raise "No essay submission found after removing text between <>" if text.blank?

    # Remove lines starting with more than 3 # characters
    text = text.split("\n").reject { |line| line.strip.start_with?("####") }.join("\n")

    # Clean up any resulting double spaces and trim
    text.gsub(/\s+/, " ").strip
  end

  def validate_essay_length(text)
    raise "Submission must be at least 5 words long" if text.split.size < 5
  end

  def friendly_cedar_error_for(error)
    case error
    when InstructureMiscPlugin::Extensions::CedarClient::CedarLimitReachedError
      I18n.t("Grading is temporarily unavailable. Please try again later.")
    when InstructureMiscPlugin::Extensions::CedarClient::ContentTooLongError
      I18n.t("The submission is too long to be graded automatically.")
    when InstructureMiscPlugin::Extensions::CedarClient::UnsupportedLanguageError
      I18n.t("The submission language is not supported for automatic grading.")
    else
      I18n.t("An unexpected error occurred while grading.")
    end
  end

  def rubric_matches_default_template?
    predefined_criteria_templates = [
      ["Exit Ticket Prompt", "Preparation", "Time", "Participation"],

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