What causes "sequence object not found" in hcengineering/platform?

Run workspace upgrade/initialization so sequences for board.class.Card are generated.

sequence object not found

Error message

sequence object not found

What it means

AddCard.svelte fetches the Sequence attached to `board.class.Card` to allocate the next card number; if findOne returns undefined the add operation aborts with this error. The sequence is required before incrementing and creating the attached card document.

Source

Thrown at plugins/board-resources/src/components/add-card/AddCard.svelte:35

  import board from '../../plugin'
  import core, { AttachedData, generateId, Ref, Space } from '@hcengineering/core'
  import { IconAdd, Button, showPopup } from '@hcengineering/ui'
  import { getClient } from '@hcengineering/presentation'
  import AddCardEditor from './AddCardEditor.svelte'
  import AddMultipleCardsPopup from './AddMultipleCardsPopup.svelte'

  export let space: Ref<Space>
  export let state: any

  let anchorRef: HTMLDivElement
  const client = getClient()

  async function addCard (title: string) {
    const newCardId = generateId()

    const sequence = await client.findOne(core.class.Sequence, { attachedTo: board.class.Card })
    if (sequence === undefined) {
      throw new Error('sequence object not found')
    }

    const incResult = await client.update(sequence, { $inc: { sequence: 1 } }, true)

    const value: AttachedData<BoardCard> = {
      status: state._id,
      number: (incResult as any).object.sequence,
      title,
      rank: '',
      assignee: null,
      description: '',
      members: [],
      location: '',
      startDate: null,
      dueDate: null
    }

    return await client.addCollection(board.class.Card, space, space, board.class.Board, 'cards', value, newCardId)

View on GitHub (pinned to 63e28dc964)

Solutions

Run workspace upgrade/initialization so sequences for board.class.Card are generated.
Create the missing Sequence document via a migration or admin tool.
Check that the query's attachedTo class matches the class the sequence was seeded with.

Example fix

// before
const sequence = await client.findOne(core.class.Sequence, { attachedTo: board.class.Card })
if (sequence === undefined) throw new Error('sequence object not found')
// after
const sequence = await client.findOne(core.class.Sequence, { attachedTo: board.class.Card })
if (sequence === undefined) {
  await showError(plugin.string.SequenceMissing)
  return
}

Defensive patterns

Strategy: try-catch

Validate before calling

const sequence = await client.findOne(core.class.Sequence, { attachedTo: board.class.Card })
if (sequence === undefined) return // or create the sequence lazily before proceeding

Type guard

function isSequence(s: Sequence | undefined): s is Sequence { return s != null }

Try / catch

try {
  await addCard(title)
} catch (e) {
  if (e instanceof Error && e.message === 'sequence object not found') {
    ui.notify('Cannot add card: numbering sequence missing')
  } else throw e
}

Prevention

Ensure migrations/seed scripts create Sequence objects for board.class.Card in every workspace.
Lazily create the sequence if missing instead of failing hard.
Verify database snapshots used for environments include sequence seed data.

When it happens

Trigger: `client.findOne(core.class.Sequence, { attachedTo: board.class.Card })` returns undefined when a user clicks add-card on a board whose sequence object is absent from the workspace.

Common situations: Workspaces created before sequence seeding was added, databases where the upgrade/migration did not run, or a board class mismatch (sequence attached to a different class).

Related errors

AI-assisted analysis of hcengineering/platform@63e28dc964 (2026-08-29). Data as JSON: /api/errors/ea5c6b89657aadf3. Report an issue: GitHub.