Update fallbacks.mdx (#17891)

* Update fallbacks.mdx

added info on new fallback step response header `cf-aig-step`

* URL added

* URL added

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Co-authored-by: daisyfaithauma <[email protected]>

Author: kathayl

src/content/docs/ai-gateway/configuration/fallbacks.mdx

@@ -3,10 +3,9 @@ pcx_content_type: configuration
 title: Fallbacks
 sidebar:
   order: 2
-
 ---
 
-import { Render } from "~/components"
+import { Render } from "~/components";
 
 Specify model or provider fallback with your [Universal endpoint](/ai-gateway/providers/universal/) to specify what to do if a request fails.
 
@@ -25,8 +24,17 @@ graph TD
     D --> E[Return Response]
 ```
 
-<br/>
+<br />
 
 You can add as many fallbacks as you need, just by adding another object in the array.
 
 <Render file="universal-gateway-example" />
+
+## Response header(cf-aig-step)
+
+When using the [Universal endpoint](/ai-gateway/providers/universal/) with fallbacks, the response header `cf-aig-step` indicates which model successfully processed the request by returning the step number. This header provides visibility into whether a fallback was triggered and which model ultimately processed the response.
+
+- `cf-aig-step:0` – The first (primary) model was used successfully.
+- `cf-aig-step:1` – The request fell back to the second model.
+- `cf-aig-step:2` – The request fell back to the third model.
+- Subsequent steps – Each fallback increments the step number by 1.