Number of dimensions allowed in GA4 data API - google-analytics

Question

While going through the new GA4 data API documentation, I didn't come across any specification for the number of dimensions allowed in a single request.
It seemed like there was no upper limit. This document doesn’t mention an upper limit and states the following:
“In a report request, you can specify zero or more dimensions.”
However when I try executing the v1alpha:runReport API via postman I get this response if I give more than 8 dimensions:
{
"error": {
"code": 400,
"message": "Requests are limited to 8 dimensions within a nested request.\n This request is for 9 dimensions.",
"status": "INVALID_ARGUMENT"
}
}
Has the number of dimensions allowed in a request been reduced to 8? If yes, can you point me to some document that states this?
The earlier UA batchGet API used to allow max 9 dimensions and I was expecting the same limit with the new GA4 data API.
Steps to Reproduce:
Post a request to v1alpha:runReport with more than 8 dimensions:
Request URL: https://analyticsdata.googleapis.com/v1alpha:runReport
Request Auth: A valid bearer token
Request Body:
{
"entity":{
"propertyId":"123456789"
},
"dateRanges":[
{
"startDate":"2021-03-29",
"endDate":"2021-03-29"
}
],
"dimensions":[
{
"name":"eventName"
},
{
"name":"source"
},
{
"name":"medium"
},
{
"name":"hostname"
},
{
"name":"dateHour"
},
{
"name":"deviceCategory"
},
{
"name":"browser"
},
{
"name":"city"
},
{
"name":"country"
}
],
"metrics":[
{
"name":"screenPageViews"
},
{
"name":"userEngagementDuration"
},
{
"name":"eventCount"
}
]
}

Answer 1

The Google analytics GA4 data api is a brand new api, released as part of GA4. As such it has not been reduced to 8 dimensions this is the current limit as it stands
Requests are limited to 8 dimensions within a nested request.
The Google analytics reporting api may allow for additional dimensions and metrics but they are it's a completely different system. You can't compare universal analytics and GA4
Note: i have submitted a note about the lack of documentation to the team

Answer 2

Updated docs state up to 9 dimensions are now allowed.
https://developers.google.com/analytics/devguides/reporting/data/v1/basics#dimensions