diff --git a/CMakeLists.txt b/CMakeLists.txt
index 09c10f6..a55d93e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,9 +26,9 @@ elseif(NOT SANITIZER STREQUAL "none")
 endif()
 
 # --- Strict warnings option ---
-option(STRICT_WARNINGS "Enable strict warnings (Wextra, Wpedantic, Werror)" OFF)
+option(STRICT_WARNINGS "Enable strict warnings (Wextra, Wpedantic, Wformat-signedness, Werror)" OFF)
 if(STRICT_WARNINGS)
-	add_compile_options(-Wextra -Wpedantic -Werror)
+	add_compile_options(-Wextra -Wpedantic -Wformat-signedness -Werror)
 endif()
 
 # --- Coverage option ---
diff --git a/src/client/client_cli.c b/src/client/client_cli.c
index 8565b63..fb0411b 100644
--- a/src/client/client_cli.c
+++ b/src/client/client_cli.c
@@ -3296,7 +3296,7 @@ int main(int argc, char* argv[]) {
       exit_code = 1;
     }
   } else if (config->use_multithreading) {
-    exit_code = send_files_multithreaded(&config);
+    exit_code = send_files_multithreaded(config);
   } else {
     exit_code = send_files(config);
   }
diff --git a/src/client/client_send.c b/src/client/client_send.c
index c777d52..e5c71f4 100644
--- a/src/client/client_send.c
+++ b/src/client/client_send.c
@@ -37,8 +37,6 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-#define STREAM_THRESHOLD (64ULL * 1024 * 1024)
-
 /* Aggregate loaded payload bytes the sender may buffer across the loader queue
    and the chunk in flight.  Sending one chunk adds up to ~2 * MAX_CHUNK_SIZE of
    transient serialize/compress buffers on top of the queued payloads, so this
@@ -1115,7 +1113,7 @@ static Client* connect_transfer_client(const Config* config) {
       return NULL;
     }
     return client_connect_ssh(config->ssh_destination, config->ssh_port,
-                              config->fastsync_server_path, config->old_args, config->rsh_command,
+                              config->fastsync_server_path, config->rsh_command,
                               config->blocking_io, config->remote_options,
                               config->remote_option_count);
   }
@@ -3617,10 +3615,9 @@ send_fail:
   return ret;
 }
 
-int send_files_multithreaded(Config** config_ptr) {
-  if (!config_ptr || !*config_ptr)
+int send_files_multithreaded(Config* config) {
+  if (!config)
     return 1;
-  Config* config = *config_ptr;
   if (config->list_only)
     return send_list_only(config);
   if (config->dry_run)
diff --git a/src/client/client_send.h b/src/client/client_send.h
index f8f3706..c8146c9 100644
--- a/src/client/client_send.h
+++ b/src/client/client_send.h
@@ -22,7 +22,7 @@ void client_set_abort_armed(bool armed);
  * never free it, and the caller retains ownership (freeing it with
  * config_delete() once the call returns). */
 int send_files(Config* config);
-int send_files_multithreaded(Config** config);
+int send_files_multithreaded(Config* config);
 /* rsync's --ignore-errors deletion gate: with no I/O error during the scan the
  * deletion phase always proceeds; with one it is suppressed unless
  * `--ignore-errors` was given.  Exposed so the decision can be unit-tested
diff --git a/src/shared/chunk.c b/src/shared/chunk.c
index ab0fb4c..54e8730 100644
--- a/src/shared/chunk.c
+++ b/src/shared/chunk.c
@@ -17,8 +17,9 @@
 #include "protocol.h"
 #include "utils.h"
 
-/* Maximum individual file data size within a chunk (64 MB) */
-#define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)
+/* Maximum individual file data size within a chunk (64 MB).  Distinct from the
+ * receiver's whole-file MAX_FILE_DATA_SIZE (256 MB) in file_receive.c. */
+#define MAX_CHUNK_FILE_DATA_SIZE (64ULL * 1024 * 1024)
 #define MAX_FILES_PER_CHUNK 65536U
 
 /* Reserve `charge` against `session`'s connection budget.  This mirrors the
@@ -382,9 +383,9 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
     }
 
     // Reject individual file data larger than the maximum allowed size.
-    if (file_data_size > MAX_FILE_DATA_SIZE) {
+    if (file_data_size > MAX_CHUNK_FILE_DATA_SIZE) {
       log_message(LOG_LEVEL_ERROR, "File data size %zu exceeds maximum %llu", file_data_size,
-                  (unsigned long long)MAX_FILE_DATA_SIZE);
+                  (unsigned long long)MAX_CHUNK_FILE_DATA_SIZE);
       goto error;
     }
 
diff --git a/src/shared/file.c b/src/shared/file.c
index 9ec981e..bcb46f4 100644
--- a/src/shared/file.c
+++ b/src/shared/file.c
@@ -26,11 +26,6 @@
 #include "protocol.h"
 #include "xattr.h"
 
-/* Files larger than this are not loaded whole for transfer (the sender streams
- * them); a whole-file digest is computed from the path instead.  Kept in sync
- * with the sender's streaming threshold. */
-#define STREAM_THRESHOLD (64ULL * 1024 * 1024)
-
 static bool write_all(int fd, const void* data, unsigned long long size) {
   const unsigned char* p = data;
   unsigned long long done = 0;
diff --git a/src/shared/protocol.h b/src/shared/protocol.h
index 73b9132..d13c3f7 100644
--- a/src/shared/protocol.h
+++ b/src/shared/protocol.h
@@ -28,6 +28,10 @@
 
 /* Maximum chunk size (64 MB) — prevents unbounded allocation from the wire */
 #define MAX_CHUNK_SIZE (64ULL * 1024 * 1024)
+/* Files larger than this are not kept fully in memory while loading: the
+ * loader skips them so the sender streams from the path, and file_checksum
+ * hashes them from disk in bounded buffers instead of forcing a full load. */
+#define STREAM_THRESHOLD (64ULL * 1024 * 1024)
 #define MAX_MANIFEST_ENTRIES (1024 * 1024)
 /* Aggregate bytes retained by one received deletion manifest. */
 #define MAX_MANIFEST_BYTES (16ULL * 1024 * 1024)
diff --git a/src/shared/transport_ssh.c b/src/shared/transport_ssh.c
index 7236133..1be7f21 100644
--- a/src/shared/transport_ssh.c
+++ b/src/shared/transport_ssh.c
@@ -87,7 +87,7 @@ static int parse_remote_dest(const char* dest, RemoteDest* r) {
   return 0;
 }
 
-char* ssh_build_remote_command(const char* server_path, bool old_args, char* const* remote_options,
+char* ssh_build_remote_command(const char* server_path, char* const* remote_options,
                                int remote_option_count) {
   const char* path = server_path ? server_path : "fastsync-server";
   const char* suffix = " --stdio";
@@ -105,9 +105,7 @@ char* ssh_build_remote_command(const char* server_path, bool old_args, char* con
      shell word (remote options below reuse the same escaping), then
      " --stdio".  Quoting the path is the only injection-safe construction: an
      unquoted path would carry shell metacharacters straight into the remote
-     shell command.  --old-args is kept for CLI/ABI compatibility but no longer
-     disables that protection. */
-  (void)old_args;
+     shell command.  (rsync's --old-args no longer disables that protection.) */
   size_t quote_count = 0;
   for (const char* p = path; *p; p++)
     if (*p == '\'')
@@ -296,8 +294,8 @@ void ssh_free_client_argv(char** argv) {
 }
 
 Client* client_connect_ssh(const char* destination, int port, const char* server_path,
-                           bool old_args, const char* rsh_command, bool blocking_io,
-                           char* const* remote_options, int remote_option_count) {
+                           const char* rsh_command, bool blocking_io, char* const* remote_options,
+                           int remote_option_count) {
   RemoteDest r;
   if (parse_remote_dest(destination, &r) != 0) {
     char* escaped = output_escape(destination, false);
@@ -376,7 +374,7 @@ Client* client_connect_ssh(const char* destination, int port, const char* server
       snprintf(ssh_user, ssh_user_len, "%s", r.host);
 
     char* remote_command =
-        ssh_build_remote_command(server_path, old_args, remote_options, remote_option_count);
+        ssh_build_remote_command(server_path, remote_options, remote_option_count);
     if (!remote_command)
       ssh_child_setup_failed(exec_pipe[1]);
     char** ssh_argv = ssh_build_client_argv(rsh_command, port, ssh_user, remote_command);
diff --git a/src/shared/transport_ssh.h b/src/shared/transport_ssh.h
index 08908ce..0ed923e 100644
--- a/src/shared/transport_ssh.h
+++ b/src/shared/transport_ssh.h
@@ -4,17 +4,17 @@
 #include "transport_tcp.h"
 
 Client* client_connect_ssh(const char* destination, int port, const char* server_path,
-                           bool old_args, const char* rsh_command, bool blocking_io,
-                           char* const* remote_options, int remote_option_count);
+                           const char* rsh_command, bool blocking_io, char* const* remote_options,
+                           int remote_option_count);
 /* Build the escaped remote-shell command string (the server program path always
  * quoted as one remote-shell word, followed by ` --stdio` and each
  * --remote-option value appended as an individually single-quoted shell word).
- * `old_args` is accepted for CLI/ABI compatibility but no longer disables
- * quoting: the path is always escaped so a metacharacter-bearing
- * --rsync-path can never be interpreted by the remote shell.  Every
- * --remote-option value is individually escaped with the '\'' sequence and
- * values with empty/control characters are rejected at the CLI parse layer. */
-char* ssh_build_remote_command(const char* server_path, bool old_args, char* const* remote_options,
+ * The path is always escaped so a metacharacter-bearing --rsync-path can never
+ * be interpreted by the remote shell (the --old-args no-op does not disable
+ * quoting).  Every --remote-option value is individually escaped with the '\''
+ * sequence and values with empty/control characters are rejected at the CLI
+ * parse layer. */
+char* ssh_build_remote_command(const char* server_path, char* const* remote_options,
                                int remote_option_count);
 /* Build the NULL-terminated child argv for the remote-shell client (argv[0] is
  * the exec/execvp program).  rsh_command is whitespace-split into leading argv
diff --git a/tests/test_transport_ssh.c b/tests/test_transport_ssh.c
index 2889444..a99630f 100644
--- a/tests/test_transport_ssh.c
+++ b/tests/test_transport_ssh.c
@@ -5,13 +5,13 @@
 static void test_ssh_connect_invalid_dest_no_colon() {
   /* cppcheck-suppress constVariablePointer */
   Client* client =
-      client_connect_ssh("invalid-destination-no-colon", 22, NULL, false, NULL, false, NULL, 0);
+      client_connect_ssh("invalid-destination-no-colon", 22, NULL, NULL, false, NULL, 0);
   EXPECT_NULL(client);
 }
 
 static void test_ssh_connect_invalid_dest_empty() {
   /* cppcheck-suppress constVariablePointer */
-  Client* client = client_connect_ssh("", 22, NULL, false, NULL, false, NULL, 0);
+  Client* client = client_connect_ssh("", 22, NULL, NULL, false, NULL, 0);
   EXPECT_NULL(client);
 }
 
@@ -22,7 +22,7 @@ static void test_ssh_connect_malformed() {
   setenv("PATH", "", 1);
 
   /* cppcheck-suppress constVariablePointer */
-  Client* client = client_connect_ssh(":", 22, NULL, false, NULL, false, NULL, 0);
+  Client* client = client_connect_ssh(":", 22, NULL, NULL, false, NULL, 0);
 
   if (saved_path) {
     setenv("PATH", saved_path, 1);
@@ -38,7 +38,7 @@ static void test_ssh_connect_malformed() {
  * The function launches ssh which will fail to connect, returns a Client. */
 static void test_ssh_connect_unreachable() {
   Client* client =
-      client_connect_ssh("nonexistent.invalid:/remote/path", 22, NULL, false, NULL, false, NULL, 0);
+      client_connect_ssh("nonexistent.invalid:/remote/path", 22, NULL, NULL, false, NULL, 0);
   if (client != NULL) {
     client_disconnect(client);
     client_delete(client);
@@ -47,23 +47,13 @@ static void test_ssh_connect_unreachable() {
 }
 
 static void test_ssh_remote_command_argument_modes() {
-  char* command = ssh_build_remote_command("fast sync; touch /tmp/pwned", false, NULL, 0);
+  char* command = ssh_build_remote_command("fast sync; touch /tmp/pwned", NULL, 0);
   EXPECT_EQ_STR(command, "'fast sync; touch /tmp/pwned' --stdio");
   free(command);
 
-  command = ssh_build_remote_command("fast'sync", false, NULL, 0);
+  command = ssh_build_remote_command("fast'sync", NULL, 0);
   EXPECT_EQ_STR(command, "'fast'\\''sync' --stdio");
   free(command);
-
-  /* --old-args no longer disables injection-safe quoting: the path is still one
-     single-quoted word, even when it carries shell metacharacters. */
-  command = ssh_build_remote_command("fast sync; touch /tmp/pwned", true, NULL, 0);
-  EXPECT_EQ_STR(command, "'fast sync; touch /tmp/pwned' --stdio");
-  free(command);
-
-  command = ssh_build_remote_command("fast'sync; rm -rf /", true, NULL, 0);
-  EXPECT_EQ_STR(command, "'fast'\\''sync; rm -rf /' --stdio");
-  free(command);
 }
 
 /* The build for a single-word argv is [prog, six -o args, "--", user, command]. */
@@ -120,12 +110,12 @@ static void test_ssh_build_client_argv_whitespace_command_and_port() {
  * returned and no command can run. */
 static void test_ssh_connect_rejects_option_host() {
   /* cppcheck-suppress constVariablePointer */
-  Client* client = client_connect_ssh("-oProxyCommand=touch /tmp/pwned:/remote", 22, NULL, false,
-                                      NULL, false, NULL, 0);
+  Client* client =
+      client_connect_ssh("-oProxyCommand=touch /tmp/pwned:/remote", 22, NULL, NULL, false, NULL, 0);
   EXPECT_NULL(client);
-  client = client_connect_ssh("-evil:/remote", 22, NULL, false, NULL, false, NULL, 0);
+  client = client_connect_ssh("-evil:/remote", 22, NULL, NULL, false, NULL, 0);
   EXPECT_NULL(client);
-  client = client_connect_ssh("user@:/remote", 22, NULL, false, NULL, false, NULL, 0);
+  client = client_connect_ssh("user@:/remote", 22, NULL, NULL, false, NULL, 0);
   EXPECT_NULL(client);
 }
 
@@ -135,13 +125,13 @@ static void test_ssh_connect_rejects_option_host() {
  * ssh_build_remote_command safety boundary for the server path. */
 static void test_ssh_remote_command_with_remote_options() {
   char* noop[] = {"--allow-delete"};
-  char* command = ssh_build_remote_command("fastsync-server", false, noop, 1);
+  char* command = ssh_build_remote_command("fastsync-server", noop, 1);
   EXPECT_EQ_STR(command, "'fastsync-server' --stdio '--allow-delete'");
   free(command);
 
   /* Multiple options append in order, each as its own quoted word. */
   char* multi[] = {"-v", "--allow-delete"};
-  command = ssh_build_remote_command("srv", false, multi, 2);
+  command = ssh_build_remote_command("srv", multi, 2);
   EXPECT_EQ_STR(command, "'srv' --stdio '-v' '--allow-delete'");
   free(command);
 
@@ -150,29 +140,24 @@ static void test_ssh_remote_command_with_remote_options() {
      break out into an arbitrary remote command. */
   char* val = strdup("--x=un'der; touch /tmp/pwned");
   char* dangerous[1] = {val};
-  command = ssh_build_remote_command("srv", false, dangerous, 1);
+  command = ssh_build_remote_command("srv", dangerous, 1);
   EXPECT_EQ_STR(command, "'srv' --stdio '--x=un'\\''der; touch /tmp/pwned'");
   free(command);
   free(val);
-
-  /* --old-args still quotes both the server path and the remote options. */
-  command = ssh_build_remote_command("srv", true, multi, 2);
-  EXPECT_EQ_STR(command, "'srv' --stdio '-v' '--allow-delete'");
-  free(command);
 }
 
 /* The remote command builder refuses to forward an empty or control-character
  * remote option (defense-in-depth independent of the CLI validation). */
 static void test_ssh_remote_command_rejects_bad_options() {
   char* empty[] = {""};
-  EXPECT_NULL(ssh_build_remote_command("srv", false, empty, 1));
+  EXPECT_NULL(ssh_build_remote_command("srv", empty, 1));
 
   char nl = '\n';
   char* newline[] = {&nl};
-  EXPECT_NULL(ssh_build_remote_command("srv", false, newline, 1));
+  EXPECT_NULL(ssh_build_remote_command("srv", newline, 1));
 
   char* with_null[] = {NULL};
-  EXPECT_NULL(ssh_build_remote_command("srv", false, with_null, 1));
+  EXPECT_NULL(ssh_build_remote_command("srv", with_null, 1));
 }
 
 void test_transport_ssh() {