diff --git a/embed/build.sh b/embed/build.sh
index 117f8f1..88e12be 100755
--- a/embed/build.sh
+++ b/embed/build.sh
@@ -12,7 +12,7 @@ trap 'rm -f sqlite3.tmp' EXIT
 "$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
 	-Wall -Wextra -Wno-unused-parameter -Wno-unused-function \
 	-o sqlite3.wasm "$ROOT/sqlite3/main.c" \
-	-I"$ROOT/sqlite3" \
+	-I"$ROOT/sqlite3/libc" -I"$ROOT/sqlite3" \
 	-mexec-model=reactor \
 	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
diff --git a/sqlite3/libc/build.sh b/sqlite3/libc/build.sh
index 3d9aa3d..855a393 100755
--- a/sqlite3/libc/build.sh
+++ b/sqlite3/libc/build.sh
@@ -6,13 +6,14 @@ cd -P -- "$(dirname -- "$0")"
 ROOT=../../
 BINARYEN="$ROOT/tools/binaryen/bin"
 WASI_SDK="$ROOT/tools/wasi-sdk/bin"
-SRCS="${1:-../strings.c}"
+SRCS="${1:-libc.c}"
 "../tools.sh"
 
-trap 'rm -f libc.tmp' EXIT
+trap 'rm -f libc.c libc.tmp' EXIT
+echo '#include <string.h>' > libc.c
 
 "$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
-	-o libc.wasm "$SRCS" \
+	-o libc.wasm -I. "$SRCS" \
 	-mexec-model=reactor \
 	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
diff --git a/sqlite3/libc/libc.wasm b/sqlite3/libc/libc.wasm
index f376156..995c28e 100755
Binary files a/sqlite3/libc/libc.wasm and b/sqlite3/libc/libc.wasm differ
diff --git a/sqlite3/libc/libc.wat b/sqlite3/libc/libc.wat
index 65e52cc..738ab4c 100644
--- a/sqlite3/libc/libc.wat
+++ b/sqlite3/libc/libc.wat
@@ -849,9 +849,11 @@
  (func $strspn (param $0 i32) (param $1 i32) (result i32)
   (local $2 i32)
   (local $3 i32)
+  (local $4 v128)
+  (local $scratch i32)
   (if
    (i32.eqz
-    (local.tee $2
+    (local.tee $3
      (i32.load8_u
       (local.get $1)
      )
@@ -863,48 +865,108 @@
     )
    )
   )
-  (v128.store
-   (i32.const 65520)
-   (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
-  )
-  (v128.store
-   (i32.const 65504)
-   (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
-  )
-  (local.set $1
-   (i32.add
-    (local.get $1)
-    (i32.const 1)
-   )
-  )
-  (loop $label
-   (i32.store
-    (local.tee $3
-     (i32.add
-      (i32.and
-       (i32.shr_u
-        (local.get $2)
-        (i32.const 3)
+  (block $block1
+   (if
+    (i32.eqz
+     (i32.load8_u offset=1
+      (local.get $1)
+     )
+    )
+    (then
+     (block $block
+      (br_if $block
+       (i32.gt_u
+        (local.tee $1
+         (local.get $0)
+        )
+        (local.tee $2
+         (i32.sub
+          (i32.shl
+           (memory.size)
+           (i32.const 16)
+          )
+          (i32.const 16)
+         )
+        )
+       )
+      )
+      (local.set $4
+       (i8x16.splat
+        (local.get $3)
+       )
+      )
+      (loop $label
+       (br_if $block
+        (i32.eqz
+         (i8x16.all_true
+          (i8x16.eq
+           (v128.load align=1
+            (local.get $1)
+           )
+           (local.get $4)
+          )
+         )
+        )
+       )
+       (br_if $label
+        (i32.le_u
+         (local.tee $1
+          (i32.add
+           (local.get $1)
+           (i32.const 16)
+          )
+         )
+         (local.get $2)
+        )
        )
-       (i32.const 28)
       )
-      (i32.const 65504)
      )
-    )
-    (i32.or
-     (i32.load
-      (local.get $3)
+     (local.set $2
+      (i32.add
+       (i32.xor
+        (local.get $0)
+        (i32.const -1)
+       )
+       (local.get $1)
+      )
      )
-     (i32.shl
-      (i32.const 1)
-      (local.get $2)
+     (loop $label1
+      (local.set $2
+       (i32.add
+        (local.get $2)
+        (i32.const 1)
+       )
+      )
+      (br_if $label1
+       (i32.eq
+        (block (result i32)
+         (local.set $scratch
+          (i32.load8_u
+           (local.get $1)
+          )
+         )
+         (local.set $1
+          (i32.add
+           (local.get $1)
+           (i32.const 1)
+          )
+         )
+         (local.get $scratch)
+        )
+        (local.get $3)
+       )
+      )
      )
+     (br $block1)
     )
    )
-   (local.set $2
-    (i32.load8_u
-     (local.get $1)
-    )
+   (v128.store
+    (i32.const 65520)
+    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+   )
+   (v128.store
+    (i32.const 65504)
+    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
    )
    (local.set $1
     (i32.add
@@ -912,20 +974,62 @@
      (i32.const 1)
     )
    )
-   (br_if $label
-    (local.get $2)
-   )
-  )
-  (if
-   (local.tee $2
-    (i32.load8_u
-     (local.tee $1
-      (local.get $0)
+   (loop $label2
+    (i32.store
+     (local.tee $2
+      (i32.add
+       (i32.and
+        (i32.shr_u
+         (local.get $3)
+         (i32.const 3)
+        )
+        (i32.const 28)
+       )
+       (i32.const 65504)
+      )
+     )
+     (i32.or
+      (i32.load
+       (local.get $2)
+      )
+      (i32.shl
+       (i32.const 1)
+       (local.get $3)
+      )
      )
     )
+    (local.set $3
+     (i32.load8_u
+      (local.get $1)
+     )
+    )
+    (local.set $1
+     (i32.add
+      (local.get $1)
+      (i32.const 1)
+     )
+    )
+    (br_if $label2
+     (local.get $3)
+    )
    )
-   (then
-    (loop $label1
+   (local.set $2
+    (local.get $0)
+   )
+   (block $block2
+    (br_if $block2
+     (i32.eqz
+      (local.tee $3
+       (i32.load8_u
+        (local.get $0)
+       )
+      )
+     )
+    )
+    (local.set $1
+     (local.get $0)
+    )
+    (loop $label3
      (if
       (i32.eqz
        (i32.and
@@ -934,7 +1038,7 @@
           (i32.add
            (i32.and
             (i32.shr_u
-             (local.get $2)
+             (local.get $3)
              (i32.const 3)
             )
             (i32.const 28)
@@ -942,41 +1046,44 @@
            (i32.const 65504)
           )
          )
-         (local.get $2)
+         (local.get $3)
         )
         (i32.const 1)
        )
       )
       (then
-       (return
-        (i32.sub
-         (local.get $1)
-         (local.get $0)
-        )
+       (local.set $2
+        (local.get $1)
        )
+       (br $block2)
       )
      )
-     (local.set $2
+     (local.set $3
       (i32.load8_u offset=1
        (local.get $1)
       )
      )
      (local.set $1
-      (i32.add
-       (local.get $1)
-       (i32.const 1)
+      (local.tee $2
+       (i32.add
+        (local.get $1)
+        (i32.const 1)
+       )
       )
      )
-     (br_if $label1
-      (local.get $2)
+     (br_if $label3
+      (local.get $3)
      )
     )
    )
+   (local.set $2
+    (i32.sub
+     (local.get $2)
+     (local.get $0)
+    )
+   )
   )
-  (i32.sub
-   (local.get $1)
-   (local.get $0)
-  )
+  (local.get $2)
  )
  (func $strcspn (param $0 i32) (param $1 i32) (result i32)
   (local $2 i32)
diff --git a/sqlite3/strings.c b/sqlite3/libc/string.h
similarity index 79%
rename from sqlite3/strings.c
rename to sqlite3/libc/string.h
index cdf5389..a785887 100644
--- a/sqlite3/strings.c
+++ b/sqlite3/libc/string.h
@@ -1,10 +1,23 @@
+#ifndef _WASM_SIMD128_STRING_H
+#define _WASM_SIMD128_STRING_H
+
 #include <stddef.h>
 #include <stdint.h>
 #include <wasm_simd128.h>
 #include <__macro_PAGESIZE.h>
 
+#include_next <string.h> // the system string.h
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #ifdef __wasm_bulk_memory__
 
+// Use the builtins if compiled with bulk memory operations.
+// Clang will intrinsify using SIMD for small, constant N.
+// For everything else, this helps inlining.
+
 void *memset(void *dest, int c, size_t n) {
   return __builtin_memset(dest, c, n);
 }
@@ -17,10 +30,19 @@ void *memmove(void *dest, const void *src, size_t n) {
   return __builtin_memmove(dest, src, n);
 }
 
-#endif
+#endif  // __wasm_bulk_memory__
 
 #ifdef __wasm_simd128__
 
+// SIMD versions of some string.h functions.
+//
+// These assume aligned v128_t reads can't fail,
+// and so can't unaligned reads up to the last
+// aligned address less than memory size.
+//
+// These also assume unaligned access is not painfully slow,
+// but that bitmask extraction is slow on AArch64.
+
 int memcmp(const void *v1, const void *v2, size_t n) {
   const v128_t *w1 = v1;
   const v128_t *w2 = v2;
@@ -166,16 +188,34 @@ char *strchr(const char *s, int c) {
   return *(char *)r == (char)c ? r : NULL;
 }
 
-#endif
+#pragma push_macro("BITOP")
 
 #define BITOP(a, b, op)                          \
   ((a)[(b) / (8 * sizeof(size_t))] op((size_t)1) \
    << ((b) % (8 * sizeof(size_t))))
 
 size_t strspn(const char *s, const char *c) {
-  if (!c[0]) return 0;
-
   const char *const a = s;
+
+  if (!c[0]) return 0;
+  if (!c[1]) {
+    const v128_t *const limit =
+        (v128_t *)(__builtin_wasm_memory_size(0) * PAGESIZE) - 1;
+
+    const v128_t *w = (void *)s;
+    const v128_t wc = wasm_i8x16_splat(*c);
+    while (w <= limit) {
+      if (!wasm_i8x16_all_true(wasm_i8x16_eq(wasm_v128_load(w), wc))) {
+        break;
+      }
+      w++;
+    }
+
+    s = (void *)w;
+    while (*s == *c) s++;
+    return s - a;
+  }
+
   size_t byteset[32 / sizeof(size_t)] = {0};
 
   for (; *c && BITOP(byteset, *(uint8_t *)c, |=); c++);
@@ -194,4 +234,12 @@ size_t strcspn(const char *s, const char *c) {
   return s - a;
 }
 
-#undef BITOP
+#pragma pop_macro("BITOP")
+
+#endif  // __wasm_simd128__
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // _WASM_SIMD128_STRING_H
\ No newline at end of file
diff --git a/sqlite3/main.c b/sqlite3/main.c
index 88da7e7..62eb1aa 100644
--- a/sqlite3/main.c
+++ b/sqlite3/main.c
@@ -1,4 +1,3 @@
-#include "strings.c"
 // Amalgamation
 #include "sqlite3.c"
 // Extensions
diff --git a/util/sql3util/wasm/build.sh b/util/sql3util/wasm/build.sh
index 53a00c5..e445a5b 100755
--- a/util/sql3util/wasm/build.sh
+++ b/util/sql3util/wasm/build.sh
@@ -12,7 +12,7 @@ trap 'rm -f sql3parse_table.tmp' EXIT
 "$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -Oz \
 	-Wall -Wextra -Wno-unused-parameter -Wno-unused-function \
 	-o sql3parse_table.wasm main.c \
-	-I"$ROOT/sqlite3" \
+	-I"$ROOT/sqlite3/libc" -I"$ROOT/sqlite3" \
 	-mexec-model=reactor \
 	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
diff --git a/util/sql3util/wasm/main.c b/util/sql3util/wasm/main.c
index 3f04173..ede7edb 100644
--- a/util/sql3util/wasm/main.c
+++ b/util/sql3util/wasm/main.c
@@ -1,6 +1,5 @@
 #include <stddef.h>
 
-#include "strings.c"
 #include "sql3parse_table.c"
 
 static_assert(offsetof(sql3table, name) == 0, "Unexpected offset");
diff --git a/vfs/tests/mptest/wasm/build.sh b/vfs/tests/mptest/wasm/build.sh
index 18c2fd5..1596c60 100755
--- a/vfs/tests/mptest/wasm/build.sh
+++ b/vfs/tests/mptest/wasm/build.sh
@@ -9,7 +9,7 @@ WASI_SDK="$ROOT/tools/wasi-sdk/bin"
 
 "$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
 	-o mptest.wasm main.c \
-	-I"$ROOT/sqlite3" \
+	-I"$ROOT/sqlite3/libc" -I"$ROOT/sqlite3" \
 	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
 	-mnontrapping-fptoint -msign-ext \
diff --git a/vfs/tests/mptest/wasm/main.c b/vfs/tests/mptest/wasm/main.c
index ba70fc9..57d0ef7 100644
--- a/vfs/tests/mptest/wasm/main.c
+++ b/vfs/tests/mptest/wasm/main.c
@@ -3,7 +3,6 @@
 // Use the default callback, not the Go one we patched in.
 #define sqliteBusyCallback sqliteDefaultBusyCallback
 
-#include "strings.c"
 // Amalgamation
 #include "sqlite3.c"
 // VFS
diff --git a/vfs/tests/speedtest1/wasm/build.sh b/vfs/tests/speedtest1/wasm/build.sh
index ffcf157..0a22ee9 100755
--- a/vfs/tests/speedtest1/wasm/build.sh
+++ b/vfs/tests/speedtest1/wasm/build.sh
@@ -9,7 +9,7 @@ WASI_SDK="$ROOT/tools/wasi-sdk/bin"
 
 "$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
 	-o speedtest1.wasm main.c \
-	-I"$ROOT/sqlite3" \
+	-I"$ROOT/sqlite3/libc" -I"$ROOT/sqlite3" \
 	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
 	-mnontrapping-fptoint -msign-ext \
diff --git a/vfs/tests/speedtest1/wasm/main.c b/vfs/tests/speedtest1/wasm/main.c
index d191e8e..cc08d56 100644
--- a/vfs/tests/speedtest1/wasm/main.c
+++ b/vfs/tests/speedtest1/wasm/main.c
@@ -1,7 +1,6 @@
 // Use the default callback, not the Go one we patched in.
 #define sqliteBusyCallback sqliteDefaultBusyCallback
 
-#include "strings.c"
 // Amalgamation
 #include "sqlite3.c"
 // VFS