[GDN] Auto-select FlashInfer GDN prefill on validated SM100 configs (#29734)

docs_new/docs/advanced_features/attention_backend.mdx

@@ -328,6 +328,8 @@ GDN (Gated Delta Network) is a linear attention mechanism with O(n) complexity,
 
 The GDN linear attention layers have their own kernel backends, selected via `--linear-attn-backend` (default: `triton`). You can override the kernel per phase with `--linear-attn-decode-backend` and `--linear-attn-prefill-backend`.
 
+On SM100/SM103 with CUDA 13+, SGLang automatically selects FlashInfer for GDN prefill when the per-phase override is unset, the base linear-attention backend is Triton, recurrent state is BF16, key/value head dimensions are 128, dynamic chunking and page-major KV layout are disabled, and `--chunked-prefill-size` is between 1 and 8192. Radix caching may be disabled or use the `no_buffer` strategy; extra-buffer strategies require state checkpoint support.
+
 <table style={{width: "100%", borderCollapse: "collapse", tableLayout: "fixed"}}>
   <colgroup>
     <col style={{width: "28%"}} />
@@ -374,6 +376,12 @@ The GDN linear attention layers have their own kernel backends, selected via `--
       <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>❌</td>
       <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>❌</td>
     </tr>
+    <tr>
+      <td style={{padding: "9px 12px", fontWeight: 500, backgroundColor: "rgba(255,255,255,0.02)"}}><strong>FlashInfer (CUDA, SM90/SM100/SM103)</strong></td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>✅</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>✅</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>✅ linear chain; tree falls back to Triton</td>
+    </tr>
   </tbody>
 </table>