diff --git a/python/sglang/srt/mem_cache/hiradix_cache.py b/python/sglang/srt/mem_cache/hiradix_cache.py
index 9a7f620fc..ad3d2b57d 100644
--- a/python/sglang/srt/mem_cache/hiradix_cache.py
+++ b/python/sglang/srt/mem_cache/hiradix_cache.py
@@ -1553,6 +1553,16 @@ class HiRadixCache(RadixCache):
                 self.ongoing_l3_reload[existing]["waiters"].append(rid)  # piggyback on the in-flight reload
                 self.cp_l3_reload_done[rid] = False
                 continue
+            # Re-validate the clean-attach against the POST-admit tree (the contract _cp_l3_reload_attach_ok
+            # documents: "checked at reserve AND at admission -- the tree may change in between"). valid_cands
+            # was built BEFORE _cp_l3_admit_reload ran this tick; a same-tick admit of THIS suffix inserts its
+            # node and pops its inflight key while leaving the l3rl object committed-and-live in the allocator.
+            # Without this recheck the dedup guard above misses (inflight key gone) and reserve() below would
+            # raise "duplicate live reservation" on the still-live object. If the suffix is now present, drop
+            # the candidate; the (un-held) request re-matches and hits the just-inserted L2 node. Rank-uniform
+            # (replicated radix + rank-uniform admit -> every rank skips the same candidate).
+            if not self._cp_l3_reload_attach_ok(lhn, skey):
+                continue
             if len(self.ongoing_l3_reload) >= self.cp_l3_reload_max_inflight:
                 continue  # cap reached (len is replicated) -> recompute
             ranges = self._cp_l3_reserve_reload_object(reload_key, store.payloads, c, allocator)