What does "Invalid stack, only stop 1 and 5 are supported for assembly" mean?

Question

I am trying to start a new Wercker build by clicking on the API endpoint mentioned in the documentation , but the API returns the following response:

{"statusCode"=>400, "error"=>"Bad Request", "message"=>"Invalid stack, only stack 1 and 5 are supported for builds"}

What does the error message "Invalid stack, only for stack 1 and 5 for assembly" mean?

I tried to send a request using the following script:

$ jq . -c <<JSON | curl -s -d @- -H 'Authorization: Bearer token' -H 'Content-type: application/json' 'https://app.wercker.com/api/v3/builds' | jq .
{
  "applicationId": "applicationid",
  "branch":"develop",
  "envVars":[
    {"key":"HOGE_FOO","value":"true"}
  ]
}
JSON

{
  "statusCode": 400,
  "error": "Bad Request",
  "message": "Invalid stack, only stack 1 and 5 are supported for builds"
}

Answer 1

[Wercker employee is here!]

Wercker, . Wercker Workflows API .

, , . 6 Workflows, 1 5 - / . , API API Runs, !