diff --git a/AGENTS.md b/AGENTS.md
index 424b38c..309d45b 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -19,7 +19,9 @@ R CMD INSTALL .
 ```r
 # Run tests (in the R console)
 devtools::test()
-# or without devtools:
+# or without devtools (package must be installed and attached;
+# NOT_CRAN=true also runs the tests that skip on aarch64):
+library(watcher)
 testthat::test_dir("tests/testthat")
 ```
 
@@ -69,6 +71,9 @@ The package uses GitHub Actions workflows in `.github/workflows/`:
 **Callback Mechanism:**
 - File events trigger `process_events()` callback in C
 - Events are bundled by path and passed to R via the 'later' package's `execLaterNative2`
+- Paths are deduplicated per callback (first occurrence kept) and copied in a
+  single allocation; combined with the patched-in event bubbling (see Build
+  System), paths reported by a single callback are always unique
 - R callbacks execute when R is idle or when `later::run_now()` is called
 - If no callback is provided, events are printed to stdout
 
@@ -100,10 +105,15 @@ hand-maintained config header, not host probing.
 - `src/link.cpp`: empty `.cpp` that forces R to link with the C++ linker.
 - `tools/update_libfswatch.sh`: re-vendors libfswatch and regenerates the config
   header, object list, and Makevars; calls `tools/patch_libfswatch.sh`.
-- `tools/patch_libfswatch.sh`: idempotent source patches — a null-format guard
-  in `string_utils`, self-guards on the fsevents/inotify/fanotify monitors, and
-  neutering of libfswatch's stdout/stderr/cerr logging (for the R CMD check
-  "compiled code" policy).
+- `tools/patch_libfswatch.sh`: idempotent source patches — (1) empty
+  `string_utils.cpp` to an include-only TU: after the logging neutering its
+  only live references are two regex-error exception messages in `monitor.cpp`,
+  unreachable in watcher (no text filters are ever added), so those are
+  replaced with a static message; also fixes a GCC 16 `-Warray-bounds` false
+  positive. (2) Self-guards on the fsevents/inotify/fanotify monitors. (3)
+  Neutering of libfswatch's stdout/stderr/cerr logging (for the R CMD check
+  "compiled code" policy). (4) `bubble_events = true` by default (the C API
+  does not expose `set_bubble_events()`).
 
 **Key dependencies:** an R C/C++ toolchain plus `make`; pthread; the
 'later' R package. A system libfswatch is used automatically when present.
diff --git a/src/fswatch/libfswatch/src/libfswatch/c++/monitor.cpp b/src/fswatch/libfswatch/src/libfswatch/c++/monitor.cpp
index 28b75b0..7e51c35 100644
--- a/src/fswatch/libfswatch/src/libfswatch/c++/monitor.cpp
+++ b/src/fswatch/libfswatch/src/libfswatch/c++/monitor.cpp
@@ -127,9 +127,7 @@ namespace fsw
     catch (const std::regex_error& error)
     {
       throw libfsw_exception(
-        string_utils::string_from_format(
-          _("An error occurred during the compilation of %s"),
-          filter.text.c_str()),
+        _("An error occurred during the compilation of a filter regex"),
         FSW_ERR_INVALID_REGEX);
     }
   }
@@ -148,9 +146,7 @@ namespace fsw
     catch (const std::regex_error& error)
     {
       throw libfsw_exception(
-        string_utils::string_from_format(
-          _("An error occurred during the compilation of %s"),
-          filter.text.c_str()),
+        _("An error occurred during the compilation of a filter regex"),
         FSW_ERR_INVALID_REGEX);
     }
   }
diff --git a/src/fswatch/libfswatch/src/libfswatch/c++/string/string_utils.cpp b/src/fswatch/libfswatch/src/libfswatch/c++/string/string_utils.cpp
index 343267a..64d11d5 100644
--- a/src/fswatch/libfswatch/src/libfswatch/c++/string/string_utils.cpp
+++ b/src/fswatch/libfswatch/src/libfswatch/c++/string/string_utils.cpp
@@ -13,54 +13,8 @@
  * You should have received a copy of the GNU General Public License along with
  * this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-#include <cstdarg>
-#include <cstdio>
-#include <vector>
+/* watcher: bodies removed as dead code. Logging is neutered, and the only
+ * other callers (regex-error paths in monitor.cpp) are unreachable in watcher.
+ * Also sidesteps a GCC 16 -Warray-bounds false positive.
+ * See tools/patch_libfswatch.sh. */
 #include "string_utils.hpp"
-
-using namespace std;
-
-namespace fsw
-{
-  namespace string_utils
-  {
-    string vstring_from_format(const char *format, va_list args)
-    {
-      if (!format) return string();
-      size_t current_buffer_size = 0;
-      int required_chars = 512;
-
-      vector<char> buffer;
-
-      do
-      {
-        current_buffer_size += required_chars;
-        buffer.resize(current_buffer_size);
-        required_chars = vsnprintf(&buffer[0], current_buffer_size, format, args);
-
-        // If an encoding error occurs, break and write an empty string into the
-        // buffer.
-        if (required_chars < 0)
-        {
-          buffer.resize(1);
-          break;
-        }
-      }
-      while ((size_t) required_chars > current_buffer_size);
-
-      return string(&buffer[0]);
-    }
-
-    string string_from_format(const char *format, ...)
-    {
-      va_list args;
-      va_start(args, format);
-
-      string ret = vstring_from_format(format, args);
-
-      va_end(args);
-
-      return ret;
-    }
-  }
-}
\ No newline at end of file
diff --git a/tools/patch_libfswatch.sh b/tools/patch_libfswatch.sh
index 71324ea..0b46dc0 100755
--- a/tools/patch_libfswatch.sh
+++ b/tools/patch_libfswatch.sh
@@ -10,8 +10,14 @@
 #
 # Every patch is IDEMPOTENT: running this on already-patched sources is a no-op.
 # The patches are:
-#   1. string_utils.cpp  - guard against a null format string (GCC
-#      -Wformat-truncation in stricter CRAN/rhub builds).
+#   1. string_utils.cpp body removal - after patch 3's logging neutering,
+#      string_from_format()/vstring_from_format() are referenced only by two
+#      regex-error exception messages in monitor.cpp, which watcher can never
+#      reach (it adds only event-flag filters, never text filters). Replace
+#      those call sites with a static message (1a) and empty string_utils.cpp
+#      to an include-only TU (1b). Also resolves a GCC 16 -Warray-bounds false
+#      positive against the upstream vector<char>::resize implementation, which
+#      R CMD check reports as a significant warning.
 #   2. Monitor self-guards - wrap fsevents/inotify/fanotify monitor bodies in
 #      their platform #ifdef so they compile to empty objects on the wrong OS
 #      (kqueue/fen/windows monitors already self-guard upstream).
@@ -59,19 +65,47 @@ add_guard() {
   echo -e "${GREEN}  ✓ self-guard $macro applied${NC}"
 }
 
-# --- Patch 1: string_utils.cpp null-format guard -----------------------------
-STRING_UTILS="$LIBFSW_SRC/c++/string/string_utils.cpp"
-if [ -f "$STRING_UTILS" ]; then
-  if grep -q "if (!format) return" "$STRING_UTILS"; then
-    echo -e "${GREEN}  ✓ string_utils null-format guard already present${NC}"
-  else
-    sed -i.bak 's|^      size_t current_buffer_size = 0;$|      if (!format) return string();\
-      size_t current_buffer_size = 0;|' "$STRING_UTILS"
-    rm -f "$STRING_UTILS.bak"
-    echo -e "${GREEN}  ✓ string_utils null-format guard applied${NC}"
+# --- Patch 1a: static regex-error messages in monitor.cpp --------------------
+# watcher never adds text filters (only event-flag filters), so the regex-error
+# exceptions in add_filter()/add_prune_filter() are unreachable. Replace their
+# string_from_format() messages with a static string so string_utils.cpp can be
+# emptied (patch 1b).
+MON_CPP="$LIBFSW_SRC/c++/monitor.cpp"
+if grep -q 'compilation of a filter regex' "$MON_CPP" 2>/dev/null; then
+  echo -e "${GREEN}  ✓ monitor.cpp regex-error messages already static${NC}"
+else
+  perl -0777 -pi -e 's/        string_utils::string_from_format\(\n          _\("An error occurred during the compilation of %s"\),\n          filter\.text\.c_str\(\)\),/        _("An error occurred during the compilation of a filter regex"),/g' "$MON_CPP"
+  if grep -q 'filter\.text\.c_str()' "$MON_CPP"; then
+    echo "Error: failed to patch string_from_format call sites in $MON_CPP" >&2
+    exit 1
   fi
+  echo -e "${GREEN}  ✓ monitor.cpp regex-error messages made static${NC}"
+fi
+
+# --- Patch 1b: empty string_utils.cpp bodies (dead code) ---------------------
+# After patch 3's logging neutering and patch 1a, nothing references
+# string_from_format()/vstring_from_format(): empty the TU. The object stays in
+# the build, compiling empty like the self-guarded monitors. This also resolves
+# the GCC 16 -Warray-bounds false positive against the upstream
+# vector<char>::resize implementation, which R CMD check reports as a
+# significant warning.
+STRING_UTILS="$LIBFSW_SRC/c++/string/string_utils.cpp"
+if grep -q 'watcher: bodies removed' "$STRING_UTILS" 2>/dev/null; then
+  echo -e "${GREEN}  ✓ string_utils.cpp bodies already removed${NC}"
 else
-  echo -e "${YELLOW}  ⚠ string_utils.cpp not found, skipping${NC}"
+  # Preserve the upstream licence header (everything before the first #include).
+  HEADER=$(awk '/^#include/{exit} {print}' "$STRING_UTILS")
+  {
+    printf '%s\n' "$HEADER"
+    cat <<'EOF'
+/* watcher: bodies removed as dead code. Logging is neutered, and the only
+ * other callers (regex-error paths in monitor.cpp) are unreachable in watcher.
+ * Also sidesteps a GCC 16 -Warray-bounds false positive.
+ * See tools/patch_libfswatch.sh. */
+#include "string_utils.hpp"
+EOF
+  } > "$STRING_UTILS.tmp" && mv "$STRING_UTILS.tmp" "$STRING_UTILS"
+  echo -e "${GREEN}  ✓ string_utils.cpp bodies removed${NC}"
 fi
 
 # --- Patch 2: self-guard the three non-self-guarding monitors ----------------