What causes "Sequence for ${training.class.Training} not found" in hcengineering/platform?

Create the missing Sequence document attached to training.class.Training (or re-run the model migration that seeds it).

Sequence for ${training.class.Training} not found

Error message

Sequence for ${training.class.Training} not found

What it means

getNextTrainingSeqNumber looks up the core Sequence document attached to training.class.Training and throws when none exists. Sequences allocate monotonic training numbers by incrementing a counter; without the Sequence document numbering cannot proceed. The Sequence must be created by the model setup/migration.

Source

Thrown at plugins/training-resources/src/utils/getNextTrainingSeqNumber.ts:14

//
// Copyright @ 2024 Hardcore Engineering Inc.
//

import { getClient } from '@hcengineering/presentation'
import core, { type Sequence } from '@hcengineering/core'
import training from '../plugin'

export async function getNextTrainingSeqNumber (): Promise<number> {
  const client = getClient()

  const sequence = await client.findOne(core.class.Sequence, { attachedTo: training.class.Training })
  if (sequence === undefined) {
    throw new Error(`Sequence for ${training.class.Training} not found`)
  }

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

  return (inc as { object: Sequence }).object.sequence
}

View on GitHub (pinned to 63e28dc964)

Solutions

Create the missing Sequence document attached to training.class.Training (or re-run the model migration that seeds it).
Verify with a query: findOne(core.class.Sequence, { attachedTo: training.class.Training }).
Check that domain migration/seeding scripts ran on this workspace.
Wrap training creation to surface a clear setup error when sequences are absent.

Example fix

// before
const seqNumber = await getNextTrainingSeqNumber()
// after
let seq = await client.findOne(core.class.Sequence, { attachedTo: training.class.Training })
if (seq === undefined) {
  seq = await client.createDoc(core.class.Sequence, core.space.Model, { attachedTo: training.class.Training, sequence: 0 })
}
const seqNumber = seq.sequence + 1

Defensive patterns

Strategy: validation

Validate before calling

const seq = await client.findOne(core.class.Sequence, { attachedTo: training.class.Training })
if (seq === undefined) throw new Error('Training sequence not seeded; run model migration')

Type guard

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

Try / catch

try { return await createTraining(data) } catch (e) { if (e.message.includes('Sequence')) await seedSequences(); else throw e }

Prevention

Ensure sequence-seeding migrations run on every workspace
Never delete core Sequence documents
Add a health check that all required sequences exist

When it happens

Trigger: Calling createTraining (which calls getNextTrainingSeqNumber) on a workspace where the training Sequence document was never seeded or was deleted.

Common situations: Fresh/test databases without full model seeding; migrations that reset sequences; someone deleting the Sequence object manually; upgrading a project where sequence creation step was added later.

Related errors

AI-assisted analysis of hcengineering/platform@63e28dc964 (2026-08-29). Data as JSON: /api/errors/372e825ce75f67f7. Report an issue: GitHub.