diff --git a/scripts/frank-small.env b/scripts/frank-small.env
index c84a785..b3d68b1 100644
--- a/scripts/frank-small.env
+++ b/scripts/frank-small.env
@@ -85,6 +85,14 @@ LISTEN_PORT=8000
 MAX_MODEL_LEN=262144
 GPU_MEM_UTIL=0.95
 KV_CACHE_DTYPE=turboquant_k8v4
+# Gemma4's config hook force-selects TRITON_ATTN for the mixed 256/512 head
+# dims, but only when no backend is selected — and TRITON_ATTN rejects the
+# turboquant KV dtype (measured: ValueError "kv_cache_dtype not supported",
+# crash loop). Pin the TURBOQUANT backend explicitly: it accepts any head
+# size, the turboquant dtypes, and has the Ampere path, and the Gemma4 MTP
+# speculator carries the target's selected backend through to the draft
+# layers, so the drafter follows.
+VLLM_ATTENTION_BACKEND=TURBOQUANT
 MAX_NUM_SEQS=16
 MAX_NUM_BATCHED_TOKENS=16384
 SPEC_NUM_TOKENS=4
diff --git a/tests/frank_small_unit.bats b/tests/frank_small_unit.bats
index 2fdef35..d64f7b0 100755
--- a/tests/frank_small_unit.bats
+++ b/tests/frank_small_unit.bats
@@ -98,7 +98,7 @@ QUADLET_LARGE="$REPO_ROOT/dankclaw/frank-large/quadlet/frank-large.container"
     ! grep -q 'HALOGEN_VISION_TOWER' "$QUADLET_LARGE"
 }
 
-@test "frank-small serves the full window with turboquant k8v4 KV on a dedicated card" {
+@test "frank-small serves the full window with turboquant KV on a dedicated card" {
     local maxlen kvdtype util seqs
     maxlen="$(sed -nE 's/^MAX_MODEL_LEN=([0-9]+)$/\1/p' "$ENV_FILE")"
     kvdtype="$(sed -nE 's/^KV_CACHE_DTYPE=(.+)$/\1/p' "$ENV_FILE")"
@@ -113,6 +113,10 @@ QUADLET_LARGE="$REPO_ROOT/dankclaw/frank-large/quadlet/frank-large.container"
     # (head_dim 256) and full-attention (head_dim 512) layers, and fp8 is
     # hardware-dead on sm_86 anyway.
     [ "$kvdtype" = "turboquant_k8v4" ]
+    # The TURBOQUANT backend must be pinned explicitly: Gemma4's config
+    # hook force-selects TRITON_ATTN (mixed 256/512 head dims) whenever no
+    # backend is selected, and TRITON_ATTN rejects the turboquant dtype.
+    grep -q '^VLLM_ATTENTION_BACKEND=TURBOQUANT$' "$ENV_FILE"
     # The 3090 is dedicated to this service, so the engine may take most of
     # it; the KV pool, not the seq ceiling, caps full-context concurrency.
     [ "$util" = "0.95" ]