diff --git a/NAM/wavenet/a2_fast.cpp b/NAM/wavenet/a2_fast.cpp
index 67093c88..512adc47 100644
--- a/NAM/wavenet/a2_fast.cpp
+++ b/NAM/wavenet/a2_fast.cpp
@@ -763,6 +763,17 @@ bool is_a2_shape(const nlohmann::json& config, int* channels)
   if (head_it != config.end() && !head_it->is_null())
     return false;
 
+  // No conditioning DSP. When given a non-null condition_dsp the generic WaveNet
+  // builds a nested model and routes the conditioning signal through it before the
+  // layer stack; the fast path has no such stage and feeds the raw input as the
+  // condition. The condition DSP carries its own weights, so the parent weight
+  // stream is identical with or without it and the loader cannot detect the
+  // difference -- the detector must reject it here, or the fast path would silently
+  // produce different audio than the model it replaces.
+  auto cond_it = config.find("condition_dsp");
+  if (cond_it != config.end() && !cond_it->is_null())
+    return false;
+
   // head_scale is loaded from the trailing weight, but require the field to
   // stay schema-compatible with the generic WaveNet parser.
   auto hs_it = config.find("head_scale");
@@ -827,6 +838,14 @@ bool is_a2_shape(const nlohmann::json& config, int* channels)
       return false;
   }
 
+  // Legacy boolean `gated` (the pre-gating_mode schema): the generic parser maps
+  // gated==true to GATED layers, which the fast path does not implement. A genuinely
+  // gated model has a larger weight stream and the loader would throw, but reject it
+  // here so the boundary is enforced by the detector rather than a downstream error.
+  auto gated_it = la.find("gated");
+  if (gated_it != la.end() && gated_it->is_boolean() && gated_it->get<bool>())
+    return false;
+
   // secondary_activation: all null (or field absent)
   auto sa_it = la.find("secondary_activation");
   if (sa_it != la.end() && !sa_it->is_null())
diff --git a/tools/run_tests.cpp b/tools/run_tests.cpp
index 61c7ba4a..0d8713d3 100644
--- a/tools/run_tests.cpp
+++ b/tools/run_tests.cpp
@@ -351,6 +351,8 @@ int main()
   test_a2_fast::test_detector_rejects_wrong_kernel_sizes();
   test_a2_fast::test_detector_rejects_wrong_activation();
   test_a2_fast::test_detector_rejects_gating();
+  test_a2_fast::test_detector_rejects_condition_dsp();
+  test_a2_fast::test_detector_rejects_legacy_gated();
   test_a2_fast::test_matches_generic_nano();
   test_a2_fast::test_matches_generic_standard();
   test_a2_fast::test_process_realtime_safe_nano();
diff --git a/tools/test/test_a2_fast.cpp b/tools/test/test_a2_fast.cpp
index 7761f7eb..89c96070 100644
--- a/tools/test/test_a2_fast.cpp
+++ b/tools/test/test_a2_fast.cpp
@@ -228,6 +228,27 @@ void test_detector_rejects_gating()
   assert(!nam::wavenet::a2_fast::is_a2_shape(cfg, nullptr));
 }
 
+// A condition DSP routes the conditioning signal through a nested model; the fast
+// path has no such stage. The nested model holds its own weights, so the parent
+// weight stream is unchanged and only the detector can catch this -- otherwise the
+// fast path would silently produce different audio than the generic WaveNet.
+void test_detector_rejects_condition_dsp()
+{
+  auto cfg = build_a2_config(8);
+  cfg["condition_dsp"] = {{"version", "0.5.0"}, {"architecture", "Linear"},
+                          {"config", nlohmann::json::object()}, {"weights", nlohmann::json::array()}};
+  assert(!nam::wavenet::a2_fast::is_a2_shape(cfg, nullptr));
+}
+
+// Legacy boolean `gated` (pre-gating_mode schema) maps to GATED layers in the
+// generic parser, which the fast path does not implement.
+void test_detector_rejects_legacy_gated()
+{
+  auto cfg = build_a2_config(3);
+  cfg["layers"][0]["gated"] = true;
+  assert(!nam::wavenet::a2_fast::is_a2_shape(cfg, nullptr));
+}
+
 void test_matches_generic(int channels)
 {
   const auto cfg = build_a2_config(channels);