instructure/canvas-lms · error · ConversationsHelper::Error

Too many participants for group conversation

Error message

Too many participants for group conversation

What it means

process_response enforces group conversation size limits: conversation#can_add_participants?(recipients) must be true for the recipients being added. When the addition would exceed the allowed number of participants, ConversationsHelper::Error is raised with status :bad_request and attribute 'recipients'.

Solutions

1. Split the recipients into smaller batches that stay within the conversation participant limit
2. Check conversation#can_add_participants?(recipients) before calling and show the user a friendly limit error
3. Increase the conversation participant limit setting if the policy allows
4. Trim the recipient list (e.g. use course sections or filters) instead of one giant add

Example fix

// before
add_recipients(conversation, all_student_ids)
// after
recipients.take(max_participants) # or chunk and send separate conversations
add_recipients(conversation, recipients) if conversation.can_add_participants?(recipients)

return render json: { error: 'too many recipients' }, status: :bad_request unless conversation.conversation.can_add_participants?(recipients)

begin
  process_response(...)
rescue ConversationsHelper::Error => e
  render json: { error: e.message }, status: :bad_request if e.message.include?('Too many participants')
end

When it happens

Trigger: Adding a batch of recipients to a group conversation that would push the participant count past the configured maximum (conversation batch size / max participants setting).

Common situations: Bulk 'message all students' flows with very large enrollments; an admin lowering the max-participants setting below existing group sizes; copy/pasting a large recipient list into the composer.

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

• The following recipients have no active enrollment in the…
• Unable to create message without a body
• 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/75b27f13a8d2fba1. Report an issue: GitHub.

Appendix: source

Thrown at app/helpers/conversations_helper.rb:57

    if context.is_a?(Course) && context.workflow_state == "completed" && !context.grants_right?(current_user, session, :read_as_admin)
      raise ConversationsHelper::Error.new(message: I18n.t("Course concluded, unable to send messages"), status: :unauthorized, attribute: "workflow_state")
    end

    if body.blank?
      raise ConversationsHelper::Error.new(message: I18n.t("Unable to create message without a body"), status: :bad_request, attribute: "empty_message")
    end

    recipients = normalize_recipients(
      recipients:,
      context_code:,
      conversation_id: conversation.conversation_id,
      current_user:,
      session:
    )

    if recipients && !conversation.conversation.can_add_participants?(recipients)
      raise ConversationsHelper::Error.new(message: I18n.t("Too many participants for group conversation"), status: :bad_request, attribute: "recipients")
    end

    invalid_recipients = get_invalid_recipients(context, recipients, current_user)
    unless invalid_recipients.to_a.empty?
      invalid_recipients = invalid_recipients.pluck(1)
      raise ConversationsHelper::Error.new(message: I18n.t("The following recipients have no active enrollment in the course, %{invalid_recipients}, unable to send messages", invalid_recipients:), status: :unauthorized, attribute: "recipients")
    end

    tags = infer_tags(
      recipients: conversation.conversation.participants.pluck(:id),
      context_code:
    )

    validate_message_ids(message_ids, conversation, current_user:)
    message_args = build_message_args(
      body:,
      attachment_ids:,
      domain_root_account_id:,

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