diff --git a/crates/ruvector-core/Cargo.toml b/crates/ruvector-core/Cargo.toml
index 52bb4f33..a20467c3 100644
--- a/crates/ruvector-core/Cargo.toml
+++ b/crates/ruvector-core/Cargo.toml
@@ -95,8 +95,13 @@ name = "bench_memory"
 harness = false
 
 [features]
-default = ["simd", "storage", "hnsw", "api-embeddings", "parallel"]
+default = ["simd", "simd-avx512", "storage", "hnsw", "api-embeddings", "parallel"]
 simd = ["simsimd"]  # SIMD acceleration (not available in WASM)
+# AVX-512 intrinsics. Requires Rust >= 1.89 (where avx512f stabilized).
+# Downstream consumers on older stable (1.77–1.88) can opt out:
+#   --no-default-features --features simd,storage,hnsw,api-embeddings,parallel
+# See issue #438.
+simd-avx512 = []
 parallel = ["rayon", "crossbeam"]  # Parallel processing (not available in WASM)
 storage = ["redb", "memmap2"]  # File-based storage (not available in WASM)
 hnsw = ["hnsw_rs"]  # HNSW indexing (not available in WASM due to mmap dependency)
diff --git a/crates/ruvector-core/src/simd_intrinsics.rs b/crates/ruvector-core/src/simd_intrinsics.rs
index fcb7f8a7..74c61e10 100644
--- a/crates/ruvector-core/src/simd_intrinsics.rs
+++ b/crates/ruvector-core/src/simd_intrinsics.rs
@@ -42,9 +42,13 @@ const PREFETCH_DISTANCE: usize = 64;
 pub fn euclidean_distance_simd(a: &[f32], b: &[f32]) -> f32 {
     #[cfg(target_arch = "x86_64")]
     {
-        if is_x86_feature_detected!("avx512f") {
-            unsafe { euclidean_distance_avx512_impl(a, b) }
-        } else if is_x86_feature_detected!("avx2") && is_x86_feature_detected!("fma") {
+        #[cfg(feature = "simd-avx512")]
+        {
+            if is_x86_feature_detected!("avx512f") {
+                return unsafe { euclidean_distance_avx512_impl(a, b) };
+            }
+        }
+        if is_x86_feature_detected!("avx2") && is_x86_feature_detected!("fma") {
             unsafe { euclidean_distance_avx2_fma_impl(a, b) }
         } else if is_x86_feature_detected!("avx2") {
             unsafe { euclidean_distance_avx2_impl(a, b) }
@@ -192,7 +196,7 @@ unsafe fn euclidean_distance_avx2_fma_impl(a: &[f32], b: &[f32]) -> f32 {
 // ============================================================================
 
 /// AVX-512 euclidean distance - processes 16 floats per iteration
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", feature = "simd-avx512"))]
 #[target_feature(enable = "avx512f")]
 unsafe fn euclidean_distance_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
     assert_eq!(a.len(), b.len(), "Input arrays must have the same length");
@@ -223,7 +227,7 @@ unsafe fn euclidean_distance_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
 }
 
 /// AVX-512 dot product - processes 16 floats per iteration
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", feature = "simd-avx512"))]
 #[target_feature(enable = "avx512f")]
 unsafe fn dot_product_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
     assert_eq!(a.len(), b.len(), "Input arrays must have the same length");
@@ -249,7 +253,7 @@ unsafe fn dot_product_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
 }
 
 /// AVX-512 cosine similarity - processes 16 floats per iteration
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", feature = "simd-avx512"))]
 #[target_feature(enable = "avx512f")]
 unsafe fn cosine_similarity_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
     assert_eq!(a.len(), b.len(), "Input arrays must have the same length");
@@ -284,7 +288,7 @@ unsafe fn cosine_similarity_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
 }
 
 /// AVX-512 Manhattan distance - processes 16 floats per iteration
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", feature = "simd-avx512"))]
 #[target_feature(enable = "avx512f")]
 unsafe fn manhattan_distance_avx512_impl(a: &[f32], b: &[f32]) -> f32 {
     assert_eq!(a.len(), b.len(), "Input arrays must have the same length");
@@ -783,9 +787,13 @@ unsafe fn manhattan_distance_neon_unrolled_impl(a: &[f32], b: &[f32]) -> f32 {
 pub fn dot_product_simd(a: &[f32], b: &[f32]) -> f32 {
     #[cfg(target_arch = "x86_64")]
     {
-        if is_x86_feature_detected!("avx512f") {
-            unsafe { dot_product_avx512_impl(a, b) }
-        } else if is_x86_feature_detected!("avx2") {
+        #[cfg(feature = "simd-avx512")]
+        {
+            if is_x86_feature_detected!("avx512f") {
+                return unsafe { dot_product_avx512_impl(a, b) };
+            }
+        }
+        if is_x86_feature_detected!("avx2") {
             unsafe { dot_product_avx2_impl(a, b) }
         } else {
             dot_product_scalar(a, b)
@@ -847,9 +855,13 @@ unsafe fn dot_product_avx2_impl(a: &[f32], b: &[f32]) -> f32 {
 pub fn cosine_similarity_simd(a: &[f32], b: &[f32]) -> f32 {
     #[cfg(target_arch = "x86_64")]
     {
-        if is_x86_feature_detected!("avx512f") {
-            unsafe { cosine_similarity_avx512_impl(a, b) }
-        } else if is_x86_feature_detected!("avx2") {
+        #[cfg(feature = "simd-avx512")]
+        {
+            if is_x86_feature_detected!("avx512f") {
+                return unsafe { cosine_similarity_avx512_impl(a, b) };
+            }
+        }
+        if is_x86_feature_detected!("avx2") {
             unsafe { cosine_similarity_avx2_impl(a, b) }
         } else {
             cosine_similarity_scalar(a, b)
@@ -883,9 +895,13 @@ pub fn cosine_similarity_avx2(a: &[f32], b: &[f32]) -> f32 {
 pub fn manhattan_distance_simd(a: &[f32], b: &[f32]) -> f32 {
     #[cfg(target_arch = "x86_64")]
     {
-        if is_x86_feature_detected!("avx512f") {
-            unsafe { manhattan_distance_avx512_impl(a, b) }
-        } else if is_x86_feature_detected!("avx2") {
+        #[cfg(feature = "simd-avx512")]
+        {
+            if is_x86_feature_detected!("avx512f") {
+                return unsafe { manhattan_distance_avx512_impl(a, b) };
+            }
+        }
+        if is_x86_feature_detected!("avx2") {
             unsafe { manhattan_distance_avx2_impl(a, b) }
         } else {
             manhattan_distance_scalar(a, b)
diff --git a/crates/ruvector-router-core/src/vector_db.rs b/crates/ruvector-router-core/src/vector_db.rs
index eacb8035..a0b38f09 100644
--- a/crates/ruvector-router-core/src/vector_db.rs
+++ b/crates/ruvector-router-core/src/vector_db.rs
@@ -150,7 +150,8 @@ impl VectorDB {
 
         if deleted {
             self.index.remove(id)?;
-            self.stats.write().total_vectors = self.stats.write().total_vectors.saturating_sub(1);
+            let mut stats = self.stats.write();
+            stats.total_vectors = stats.total_vectors.saturating_sub(1);
         }
 
         Ok(deleted)
diff --git a/docs/research/claude-code-rvsource/versions/v2.1.x/modules-manifest.json b/docs/research/claude-code-rvsource/versions/v2.1.x/modules-manifest.json
index 639e90a1..696b14d6 100644
--- a/docs/research/claude-code-rvsource/versions/v2.1.x/modules-manifest.json
+++ b/docs/research/claude-code-rvsource/versions/v2.1.x/modules-manifest.json
@@ -1418,7 +1418,7 @@
       "size": 387
     },
     {
-      "name": "type.js",
+      "name": "type_lc.js",
       "size": 387
     },
     {
@@ -2330,7 +2330,7 @@
       "size": 176
     },
     {
-      "name": "tmux.js",
+      "name": "tmux_lc.js",
       "size": 176
     },
     {
diff --git a/docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/tmux.js b/docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/tmux_lc.js
similarity index 100%
rename from docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/tmux.js
rename to docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/tmux_lc.js
diff --git a/docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/type.js b/docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/type_lc.js
similarity index 100%
rename from docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/type.js
rename to docs/research/claude-code-rvsource/versions/v2.1.x/tree/react_memo_cache_sentinel/react_memo_cache_sentinel/type_lc.js