Hi,

Just been looking into this for you. All the docs I found suggested it would reject to I tried testing it myself. I tried setting traffic_config with various percentage combinations that don't sum to 100, on both Azure and AWS:

In my case, every non-100% configuration was rejected with a validation error on both clouds. So I wasn't able to reproduce what you're describing.

What the docs say

The docs are consistent with what I saw:

• The Model Serving concepts page shows all examples with percentages summing to exactly 100.
• The Serve multiple models page demonstrates traffic splits of 50/50 and 60/40.
• The AI Gateway traffic splitting docs explicitly state: "Percentages must sum to 100%."

A few thoughts on why yours might have been accepted

I don't doubt you saw it work, but here are some things worth checking:

• Check what the API actually persisted. Use GET /api/2.0/serving-endpoints/{name} and look at the traffic_config in the response. It's possible the UI normalised the values before saving them (so it might show 50/50 even though you entered 100/100).
• It could be a timing thing. If you tested this a while back, validation may have been tightened since then. The current API (as of July 2026) rejects it consistently for me.
• If it genuinely is still being accepted in your environment, that sounds like a bug worth reporting. I'd suggest filing a support ticket with the workspace ID, endpoint name, and the exact config you used. That way the engineering team can check whether there's a validation gap specific to your region or workspace.

On the 50/50 routing question

Your observation of a 50/50 split from 100/100 does make sense if the values were being treated as relative weights (100/(100+100) = 50% each). That's a common pattern in load balancers. But since the API is supposed to reject the config outright, the routing behaviour is somewhat academic unless you can still reproduce the acceptance.

If you do manage to reproduce it, an asymmetric test like 150/50 would be the way to confirm whether it's true proportional normalisation (which would give 75/25) or just a fallback to equal distribution (which would give 50/50).

References

• Model Serving concepts
• Serve multiple models to a model serving endpoint
• Configure traffic splitting and fallbacks (AI Gateway)

Hope that helps!

Thanks,

Emma