Posting here because the Reddit post didn't get any traction and unsure if this is still a supported product based on lack of response? I'm integrating WhereParcel's Tracking API into a shipping audit workflow and ran into something confusing.

According to the docs, /v2/track supports batching multiple tracking numbers (up to 5), and our implementation has been using that pattern successfully.

Request format:

{
"trackingItems": [
{
"carrier": "us.ups",
"trackingNumber": "..."
},
{
"carrier": "us.ups",
"trackingNumber": "..."
}
]
}
Authentication is working — the request reaches WhereParcel and is visible in the API dashboard.

However, when sending 5 UPS tracking numbers in a single synchronous /v2/track request, the API now returns:

INVALID_REQUEST

Maximum 1 item allowed per synchronous request for these carriers:
us.ups (5 requested)
The confusing part:

The public tracking API docs indicate up to 5 parcels per request.

Rate limits are nowhere near being exceeded.

Authentication is successful.

The carrier code (us.ups) appears to be the documented value.

Questions:

Is there currently a carrier-specific limitation where us.ups only supports one tracking item per synchronous /v2/track request?

If so, is this a recent API behavior change that hasn't made it into the docs yet?

Should integrations handle UPS by splitting into one request per tracking number, while continuing to batch other carriers?

Is there another recommended approach (webhooks, async tracking registration, etc.) for multiple UPS shipments?

I can obviously work around this by making singleton UPS requests, but I want to make sure I'm implementing against the intended API behavior rather than coding around an undocumented restriction.