diff --git a/src/client/change_list.c b/src/client/change_list.c
index 9f3d728..a2c5096 100644
--- a/src/client/change_list.c
+++ b/src/client/change_list.c
@@ -245,7 +245,7 @@ static char* change_render_name_uptodate(const ChangeEvent* event) {
  * resolves to xxh128, so an explicit selection and the default both render the
  * selected algorithm's digest. */
 static ChecksumAlgo out_format_checksum_algo(const Config* config) {
-  return (ChecksumAlgo)config->checksum_transfer_algo;
+  return (ChecksumAlgo)config->cli.checksum_transfer_algo;
 }
 
 /* Render a digest as rsync's sum_as_hex: xxh128 prints the HIGH 64-bit half
diff --git a/src/client/client_cli.c b/src/client/client_cli.c
index fb0411b..12f0c6d 100644
--- a/src/client/client_cli.c
+++ b/src/client/client_cli.c
@@ -170,7 +170,7 @@ static int set_positive_int_option(int* dest, const char* value, const char* opt
  * name is a hard error with rsync's exit code 4, never a silent no-op. */
 static int set_compression_choice(Config* config, const char* value) {
   if (!value) {
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   int algo;
@@ -178,7 +178,7 @@ static int set_compression_choice(Config* config, const char* value) {
     algo = compression_choice_resolve();
     if (algo < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_COMPRESS_LIST names no supported compression algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
   } else {
@@ -189,7 +189,7 @@ static int set_compression_choice(Config* config, const char* value) {
                 "--compress-choice '%s' is not a supported algorithm; FastSync supports zstd, "
                 "lz4, zlib, zlibx, none or auto",
                 value);
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   const char* canonical = compression_algo_name((CompressionAlgo)algo);
@@ -226,7 +226,7 @@ static int resolve_checksum_name(const char* name, size_t len, int* out) {
  * resolves to FastSync's negotiated default (xxh128). */
 static int set_checksum_choice(Config* config, const char* value) {
   if (!value) {
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   const char* comma = strchr(value, ',');
@@ -244,7 +244,7 @@ static int set_checksum_choice(Config* config, const char* value) {
                 "--checksum-choice '%s' is invalid; FastSync supports xxh64 (or xxhash), xxh128, "
                 "xxh3, md5, md4, sha1, none or auto, optionally as 'transfer,pre-transfer'",
                 value);
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
   int negotiated = -1;
@@ -252,7 +252,7 @@ static int set_checksum_choice(Config* config, const char* value) {
     negotiated = checksum_choice_resolve();
     if (negotiated < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_CHECKSUM_LIST names no supported checksum algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
   }
@@ -264,8 +264,8 @@ static int set_checksum_choice(Config* config, const char* value) {
     pre = negotiated;
 
   config->checksum_algo = pre;
-  config->checksum_transfer_algo = transfer;
-  config->checksum_choice_set = true;
+  config->cli.checksum_transfer_algo = transfer;
+  config->cli.checksum_choice_set = true;
   /* rsync: "none" for the transfer checksum forces --whole-file. */
   if (transfer == (int)CHECKSUM_ALGO_NONE)
     config->whole_file = true;
@@ -963,7 +963,10 @@ static const OptionEntry OPTION_TABLE[] = {
      * faithful no-op (accepted silently, never consumes an argument). */
     {"--recursive", "-r", OPT_NOOP, 0},
     {"--update", "-u", OPT_FLAG, offsetof(Config, update)},
-    {"--old-args", NULL, OPT_FLAG, offsetof(Config, old_args)},
+    /* rsync's --old-args: accepted for CLI compatibility as a documented no-op
+     * (the remote server path is always safely quoted; see usage.c).  It is
+     * recognized but stores no Config field. */
+    {"--old-args", NULL, OPT_NOOP, 0},
     {"--rsh", "-e", OPT_STRING, offsetof(Config, rsh_command)},
     {"--blocking-io", NULL, OPT_FLAG, offsetof(Config, blocking_io)},
     {"--links", "-l", OPT_FLAG, offsetof(Config, follow_symlinks)},
@@ -1196,12 +1199,12 @@ static int apply_negation(Config* config, const char* arg) {
     config->preserve_times = false;
     config->preserve_owner = false;
     config->preserve_group = false;
-    config->metadata_explicitly_disabled = true;
+    config->cli.metadata_explicitly_disabled = true;
     /* --no-preserve is an explicit opt-out of the whole bundle: record it so
      * the --incremental/--delta auto-preserve in cli_finalize_config does not
      * silently re-enable perms/times. */
-    config->preserve_perms_explicit_off = true;
-    config->preserve_times_explicit_off = true;
+    config->cli.preserve_perms_explicit_off = true;
+    config->cli.preserve_times_explicit_off = true;
     return 0;
   }
   *(bool*)((char*)config + entry->offset) = false;
@@ -1209,9 +1212,9 @@ static int apply_negation(Config* config, const char* arg) {
    * auto-preserve the OTHER attribute without undoing this one.  A later
    * -p/-t sets the attribute directly; this flag only gates the implication. */
   if (entry->offset == offsetof(Config, preserve_perms))
-    config->preserve_perms_explicit_off = true;
+    config->cli.preserve_perms_explicit_off = true;
   else if (entry->offset == offsetof(Config, preserve_times))
-    config->preserve_times_explicit_off = true;
+    config->cli.preserve_times_explicit_off = true;
   return 0;
 }
 
@@ -1440,7 +1443,7 @@ static bool cli_handle_range_time_options(CliParseCtx* ctx) {
       ctx->exit_code = -1;
       return true;
     }
-    config->stop_at_set = true;
+    config->cli.stop_at_set = true;
     return true;
   }
   if (strcmp(arg, "--stop-at") == 0) {
@@ -1455,7 +1458,7 @@ static bool cli_handle_range_time_options(CliParseCtx* ctx) {
       ctx->exit_code = -1;
       return true;
     }
-    config->stop_at_set = true;
+    config->cli.stop_at_set = true;
     return true;
   }
   const char* threads_prefix = "--compress-threads=";
@@ -1526,7 +1529,7 @@ static bool cli_handle_table_option(CliParseCtx* ctx) {
         return true;
       }
       if (entry->offset == offsetof(Config, compression_level))
-        config->compression_level_set = true;
+        config->cli.compression_level_set = true;
       if (entry->offset == offsetof(Config, chmod_spec)) {
         mode_t ignored;
         if (!chmod_apply(0, config->chmod_spec, &ignored)) {
@@ -1539,7 +1542,7 @@ static bool cli_handle_table_option(CliParseCtx* ctx) {
          defaults to 127.0.0.1, so a value check cannot distinguish it).  Used
          by --dry-run to route an explicit remote target to the server. */
       if (entry->offset == offsetof(Config, server_host))
-        config->server_host_set = true;
+        config->cli.server_host_set = true;
     }
   } else if (apply_table_option(config, entry, NULL) != 0) {
     ctx->exit_code = -1;
@@ -1813,7 +1816,7 @@ static bool cli_handle_transfer_flags(CliParseCtx* ctx) {
           return true;
         }
         config->compression_level = (int)level;
-        config->compression_level_set = true;
+        config->cli.compression_level_set = true;
         log_info_message(LOG_INFO_MISC, "Set Compression level to %ld", level);
         ctx->i++;
       }
@@ -1877,7 +1880,7 @@ static int set_server_port_option(Config* config, const char* value, const char*
     return -1;
   }
   config->server_port = port;
-  config->server_port_set = true;
+  config->cli.server_port_set = true;
   return 0;
 }
 
@@ -2648,7 +2651,7 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
     int resolved = compression_choice_resolve();
     if (resolved < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_COMPRESS_LIST names no supported compression algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
     config->compression_algo = resolved;
@@ -2659,7 +2662,7 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
    * clamped to the codec's range, otherwise the codec's own default is used. */
   if (config->use_compression) {
     CompressionAlgo algo = (CompressionAlgo)config->compression_algo;
-    config->compression_level = config->compression_level_set
+    config->compression_level = config->cli.compression_level_set
                                     ? compression_clamp_level(algo, config->compression_level)
                                     : compression_default_level(algo);
     log_debug_message(LOG_DEBUG_UTIL, "Client compression: %s (level %d)",
@@ -2668,22 +2671,22 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
   /* The negotiated checksum is always resolved (rsync negotiates one for the
    * delta strong sum even without --checksum): RSYNC_CHECKSUM_LIST first, then
    * the compiled-in order.  An explicit --checksum-choice already set it. */
-  if (!config->checksum_choice_set) {
+  if (!config->cli.checksum_choice_set) {
     int resolved = checksum_choice_resolve();
     if (resolved < 0) {
       log_message(LOG_LEVEL_ERROR, "RSYNC_CHECKSUM_LIST names no supported checksum algorithm");
-      config->cli_exit_code = 4;
+      config->cli.cli_exit_code = 4;
       return -1;
     }
     config->checksum_algo = resolved;
-    config->checksum_transfer_algo = resolved;
+    config->cli.checksum_transfer_algo = resolved;
   }
   /* rsync parity: "none" as the pre-transfer checksum cannot be combined with
    * --checksum (exit 4).  The check runs here because --checksum may appear on
    * either side of --checksum-choice. */
   if (config->checksum && config->checksum_algo == (int)CHECKSUM_ALGO_NONE) {
     log_message(LOG_LEVEL_ERROR, "Invalid checksum-choice for --checksum: none");
-    config->cli_exit_code = 4;
+    config->cli.cli_exit_code = 4;
     return -1;
   }
 
@@ -2762,11 +2765,11 @@ static int cli_finalize_config(Config* config, bool verbose, bool no_delta, bool
    * explicitly negated them (--no-perms/--no-times/--no-preserve).  This runs
    * BEFORE the derived use_metadata bit so the transport frame is still sent
    * for the incremental/delta handshake even when both attributes were negated
-   * via --no-preserve (metadata_explicitly_disabled handles that opt-out). */
-  if (preserve_implied && !config->metadata_explicitly_disabled) {
-    if (!config->preserve_perms_explicit_off)
+   * via --no-preserve (cli.metadata_explicitly_disabled handles that opt-out). */
+  if (preserve_implied && !config->cli.metadata_explicitly_disabled) {
+    if (!config->cli.preserve_perms_explicit_off)
       config->preserve_perms = true;
-    if (!config->preserve_times_explicit_off)
+    if (!config->cli.preserve_times_explicit_off)
       config->preserve_times = true;
   }
 
@@ -3153,7 +3156,7 @@ int main(int argc, char* argv[]) {
   int parse_ret = parse_args(config, argc, argv, positional_args, &positional_count);
   if (parse_ret != 0) {
     if (parse_ret < 0)
-      exit_code = config->cli_exit_code ? config->cli_exit_code : 1;
+      exit_code = config->cli.cli_exit_code ? config->cli.cli_exit_code : 1;
     goto cleanup;
   }
 
diff --git a/src/client/client_manifest.c b/src/client/client_manifest.c
index d476bb3..55a3f67 100644
--- a/src/client/client_manifest.c
+++ b/src/client/client_manifest.c
@@ -31,7 +31,7 @@ bool dry_run_targets_server(const Config* config) {
     return true;
   if (config->module && config->module[0] != '\0')
     return true;
-  if (config->server_host_set || config->server_port_set)
+  if (config->cli.server_host_set || config->cli.server_port_set)
     return true;
   if (config->use_tls)
     return true;
diff --git a/src/client/client_send.c b/src/client/client_send.c
index 3b77503..2f3422b 100644
--- a/src/client/client_send.c
+++ b/src/client/client_send.c
@@ -1578,7 +1578,7 @@ static bool send_files_run(Config* config, SendFilesState* state) {
     now_mono.tv_nsec = 0;
   }
   state->stop = stop_condition_make(config->stop_after_mins > 0, config->stop_after_mins,
-                                    config->stop_at_set, config->stop_at, now_mono);
+                                    config->cli.stop_at_set, config->stop_at, now_mono);
   state->prepared.options.stop_condition = &state->stop;
   /* The early-delete pre-scan above already ran; only the data pass should feed
      the directory-time list (otherwise every directory would be captured
@@ -1916,7 +1916,7 @@ int send_files_multithreaded(Config* config) {
     now_mono.tv_nsec = 0;
   }
   context->stop_condition =
-      stop_condition_make(config->stop_after_mins > 0, config->stop_after_mins, config->stop_at_set,
+      stop_condition_make(config->stop_after_mins > 0, config->stop_after_mins, config->cli.stop_at_set,
                           config->stop_at, now_mono);
   bool collect_excluded = config->use_delete && !config->delete_excluded;
   unsigned long long pre_scan_non_dir = 0;
diff --git a/src/shared/config.c b/src/shared/config.c
index f4b255d..eea3974 100644
--- a/src/shared/config.c
+++ b/src/shared/config.c
@@ -20,9 +20,9 @@
 
 static void config_set_defaults(Config* config) {
   config->scanner_threads = 0;
-  config->metadata_explicitly_disabled = false;
-  config->preserve_perms_explicit_off = false;
-  config->preserve_times_explicit_off = false;
+  config->cli.preserve_perms_explicit_off = false;
+  config->cli.preserve_times_explicit_off = false;
+  config->cli.metadata_explicitly_disabled = false;
   config->show_progress = false;
   config->compression_threads = 0;
   config->ssh_port = 22;
@@ -44,8 +44,8 @@ static void config_set_defaults(Config* config) {
   config->tls_ca = NULL;
   config->server_host = str_dup("127.0.0.1");
   config->server_port = 8080;
-  config->server_port_set = false;
-  config->server_host_set = false;
+  config->cli.server_port_set = false;
+  config->cli.server_host_set = false;
   /* rsync defaults: --timeout=0 (I/O timeouts disabled) and --contimeout=60.
    * A value of 0 disables the client's own deadline on both the socket layer
    * (tcp_set_timeouts) and the protocol layer
@@ -68,10 +68,10 @@ static void config_set_defaults(Config* config) {
   config->human_readable = false;
   config->ignore_errors = false;
   config->ignore_missing_args = false;
-  config->checksum_transfer_algo = CHECKSUM_ALGO_DEFAULT;
-  config->cli_exit_code = 0;
-  config->compression_level_set = false;
-  config->checksum_choice_set = false;
+  config->cli.checksum_transfer_algo = CHECKSUM_ALGO_DEFAULT;
+  config->cli.cli_exit_code = 0;
+  config->cli.compression_level_set = false;
+  config->cli.checksum_choice_set = false;
   config->filters = NULL;
   config->files_from = NULL;
   config->files_from_set = NULL;
@@ -85,7 +85,6 @@ static void config_set_defaults(Config* config) {
   config->rsh_command = NULL;
   config->blocking_io = false;
   config->outbuf = OUTBUF_BLOCK;
-  config->old_args = false;
   config->remote_options = NULL;
   config->remote_option_count = 0;
   config->address = NULL;
@@ -101,7 +100,7 @@ static void config_set_defaults(Config* config) {
   config->trust_sender = false;
   config->stop_after_mins = 0;
   config->stop_at = 0;
-  config->stop_at_set = false;
+  config->cli.stop_at_set = false;
   config->write_batch = NULL;
   config->only_write_batch = NULL;
   config->read_batch = NULL;
@@ -342,7 +341,7 @@ bool config_derived_use_metadata(const Config* config) {
       config->chown_uid_set || config->chown_gid_set || config->usermap_count > 0 ||
       config->groupmap_count > 0 || config->update)
     return true;
-  return (config->use_incremental || config->use_delta) && !config->metadata_explicitly_disabled;
+  return (config->use_incremental || config->use_delta) && !config->cli.metadata_explicitly_disabled;
 }
 
 bool config_has_basis(const Config* config) {
diff --git a/src/shared/config.h b/src/shared/config.h
index c4d7130..3596620 100644
--- a/src/shared/config.h
+++ b/src/shared/config.h
@@ -342,22 +342,60 @@ typedef enum SuperMode { SUPER_MODE_AUTO = 0, SUPER_MODE_ON = 1, SUPER_MODE_OFF
   CONFIG_WIRE_CODEC_FIELDS(X)                                                                      \
   CONFIG_WIRE_PROTECT_FIELDS(X)
 
+/* Client-only, CLI-parse bookkeeping (never serialized).  These members exist
+ * only so the client command-line parser can record HOW an option was
+ * specified (explicitly set, explicitly negated, or a parser-requested exit
+ * code); no other module and no wire peer ever needs them.  Grouping them in
+ * one nested member keeps the public Config free of client-CLI-only state. */
+typedef struct {
+  /* Set when the user explicitly turned an attribute off with --no-perms /
+   * --no-times (long or short form).  --incremental/--delta historically
+   * auto-enabled mode and mtime preservation; these flags let
+   * cli_finalize_config restore that behavior while still honoring the
+   * explicit per-attribute negation.  A later -p/-t re-enables the attribute
+   * directly, so the flag only prevents the incremental/delta implication,
+   * never a POSITIVE request. */
+  bool preserve_perms_explicit_off;
+  bool preserve_times_explicit_off;
+  /* Set by --no-preserve, the explicit opt-out of the whole preservation
+   * bundle, so the --incremental/--delta auto-preserve implication stays off. */
+  bool metadata_explicitly_disabled;
+  /* True when --server-port/--port was explicitly given.  --dry-run uses it to
+   * decide whether a real server handshake was requested, so a plain local
+   * destination (no explicit port) keeps the existing client-side dry-run
+   * behavior instead of dialing the default 127.0.0.1:8080. */
+  bool server_port_set;
+  /* True when --server-host was explicitly given, and distinct from the
+   * "127.0.0.1" default: --dry-run uses it to route an explicit remote target
+   * to the server so it reports receiver state exactly like a real run,
+   * instead of silently running the client-side manifest. */
+  bool server_host_set;
+  /* Codec-negotiation CLI state.  The effective pre-transfer checksum is
+   * Config->checksum_algo (serialized); checksum_transfer_algo is the rsync
+   * "transfer" half of a two-name --checksum-choice form (validated and used
+   * only to mirror rsync's whole-file forcing, since FastSync's per-block
+   * strong hash is fixed).  cli_exit_code carries a parser-requested process
+   * exit status (rsync uses 4 for an unsupported checksum/compress algorithm)
+   * so main() can mirror it. */
+  int checksum_transfer_algo;
+  int cli_exit_code;
+  /* "The user explicitly chose" bits.  They let the per-codec default level /
+   * checksum list be applied only when the corresponding rsync option was
+   * omitted (an explicit --compress-level / --checksum-choice always wins). */
+  bool compression_level_set;
+  bool checksum_choice_set;
+  /* True when --stop-at was given. */
+  bool stop_at_set;
+} ConfigCliParse;
+
 typedef struct Config {
   /* -j/--threads=N: number of parallel scanner worker threads for the -m
    * pipeline.  0 (the default, also set by bare -j/--threads) means "use the
    * scanner's built-in default" (4).  CLIENT-ONLY: it is a local scheduling
    * concern and is NEVER serialized into the wire config frame. */
   int scanner_threads;
-  bool metadata_explicitly_disabled;
-  /* CLIENT-ONLY (never serialized; not in CONFIG_WIRE_FIELDS).  Set when the
-   * user explicitly turned an attribute off with --no-perms / --no-times (long
-   * or short form).  --incremental/--delta historically auto-enabled mode and
-   * mtime preservation; these flags let cli_finalize_config restore that
-   * behavior while still honoring the explicit per-attribute negation.  A
-   * later -p/-t re-enables the attribute directly, so the flag only prevents
-   * the incremental/delta implication, never a POSITIVE request. */
-  bool preserve_perms_explicit_off;
-  bool preserve_times_explicit_off;
+  /* Client-only CLI-parse bookkeeping (never serialized).  See ConfigCliParse. */
+  ConfigCliParse cli;
   bool show_progress;
   int compression_threads;
   int ssh_port;
@@ -378,18 +416,6 @@ typedef struct Config {
   bool use_tls;
   char* server_host;
   int server_port;
-  /* True when --server-port/--port was explicitly given.  CLIENT-ONLY (never
-   * serialized): --dry-run uses it to decide whether a real server handshake
-   * was requested, so a plain local destination (no explicit port) keeps the
-   * existing client-side dry-run behavior instead of dialing the default
-   * 127.0.0.1:8080. */
-  bool server_port_set;
-  /* True when --server-host was explicitly given.  CLIENT-ONLY (never
-   * serialized), and distinct from the "127.0.0.1" default: --dry-run uses it
-   * to route an explicit remote target to the server so it reports receiver
-   * state exactly like a real run, instead of silently running the client-side
-   * manifest. */
-  bool server_host_set;
   char* tls_cert;
   char* tls_key;
   char* tls_ca;
@@ -435,22 +461,6 @@ typedef struct Config {
    * enters the keep-set.  Implied by --delete-missing-args. */
   bool ignore_missing_args;
 
-  /* Codec-negotiation CLI state (all client-only, never serialized).  The
-   * effective pre-transfer checksum is Config->checksum_algo (serialized);
-   * checksum_transfer_algo is the rsync "transfer" half of a two-name
-   * --checksum-choice form (validated and used only to mirror rsync's
-   * whole-file forcing, since FastSync's per-block strong hash is fixed).
-   * cli_exit_code carries a parser-requested process exit status (rsync uses 4
-   * for an unsupported checksum/compress algorithm) so main() can mirror it. */
-  int checksum_transfer_algo;
-  int cli_exit_code;
-  /* Client-only "the user explicitly chose" bits.  They let the per-codec
-   * default level / checksum list be applied only when the corresponding
-   * rsync option was omitted (an explicit --compress-level / --checksum-choice
-   * always wins).  Never serialized. */
-  bool compression_level_set;
-  bool checksum_choice_set;
-
   // Issue #129: Advanced file selection. These fields are CLIENT-ONLY: they are
   // never serialized to the wire (the receiver must not learn them).
   ArrayList* filters;   /* --filter=RULE rule strings, in order */
@@ -486,7 +496,6 @@ typedef struct Config {
   /* --outbuf mode (OutbufMode): stdout/stderr buffering.  Client-only launch
    * concern: NEVER crosses the wire. */
   int outbuf;
-  bool old_args;
   /* --remote-option=OPT (Phase 5, long form only): one or more extra command-line
    * options to append to the REMOTE server invocation over SSH.  CLIENT-ONLY:
    * they are composed into the remote command line by ssh_build_remote_command()
@@ -556,7 +565,6 @@ typedef struct Config {
    * process and are NEVER serialized into the config frame. */
   int stop_after_mins; /* --stop-after=MINS minutes; 0 when unset */
   time_t stop_at;      /* --stop-at=... absolute wall-clock deadline */
-  bool stop_at_set;    /* true when --stop-at was given */
 
   /* Client-only residual-batch paths.  A residual batch is a self-contained
    * single-file record of the whole source tree (full file images using the
diff --git a/tests/test_change_list.c b/tests/test_change_list.c
index f9ad8a5..ef0f16d 100644
--- a/tests/test_change_list.c
+++ b/tests/test_change_list.c
@@ -195,7 +195,7 @@ static void test_format_C_padding_uses_transfer_algo() {
       {CHECKSUM_ALGO_NONE, 2},
   };
   for (size_t i = 0; i < sizeof(cases) / sizeof(cases[0]); i++) {
-    config->checksum_transfer_algo = cases[i].algo;
+    config->cli.checksum_transfer_algo = cases[i].algo;
     char expected[64];
     size_t n = 0;
     expected[n++] = '[';
diff --git a/tests/test_client_cli.c b/tests/test_client_cli.c
index d86f8f6..e86aec7 100644
--- a/tests/test_client_cli.c
+++ b/tests/test_client_cli.c
@@ -730,7 +730,7 @@ static void test_parse_args_port_alias() {
   EXPECT_EQ_INT(cfg->server_port, 9000);
   /* The default port is 8080; the explicit bit is what lets --dry-run tell an
      explicit remote target from the default and route to the server. */
-  EXPECT_TRUE(cfg->server_port_set);
+  EXPECT_TRUE(cfg->cli.server_port_set);
   config_delete(cfg);
 
   cfg = config_create();
@@ -738,7 +738,7 @@ static void test_parse_args_port_alias() {
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv_inline, positional_args, &positional_count), 0);
   EXPECT_EQ_INT(cfg->server_port, 9001);
-  EXPECT_TRUE(cfg->server_port_set);
+  EXPECT_TRUE(cfg->cli.server_port_set);
   config_delete(cfg);
 
   cfg = config_create();
@@ -746,7 +746,7 @@ static void test_parse_args_port_alias() {
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv_long, positional_args, &positional_count), 0);
   EXPECT_EQ_INT(cfg->server_port, 9002);
-  EXPECT_TRUE(cfg->server_port_set);
+  EXPECT_TRUE(cfg->cli.server_port_set);
   config_delete(cfg);
 }
 
@@ -757,18 +757,18 @@ static void test_parse_args_server_host_sets_routing_bit() {
   Config* cfg = config_create();
   int positional_args[2];
   int positional_count = 0;
-  EXPECT_FALSE(cfg->server_host_set);
+  EXPECT_FALSE(cfg->cli.server_host_set);
   char* argv_space[] = {"fastsync", "--server-host", "example.test", "/src", "/dst"};
   EXPECT_EQ_INT(parse_args(cfg, 5, argv_space, positional_args, &positional_count), 0);
   EXPECT_EQ_STR(cfg->server_host, "example.test");
-  EXPECT_TRUE(cfg->server_host_set);
+  EXPECT_TRUE(cfg->cli.server_host_set);
   config_delete(cfg);
 
   cfg = config_create();
   char* argv_inline[] = {"fastsync", "--server-host=example.test", "/src", "/dst"};
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv_inline, positional_args, &positional_count), 0);
-  EXPECT_TRUE(cfg->server_host_set);
+  EXPECT_TRUE(cfg->cli.server_host_set);
   config_delete(cfg);
 }
 
@@ -1726,7 +1726,7 @@ static void test_parse_args_no_preserve_blocks_implicit_metadata() {
 
     EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), 0);
     EXPECT_FALSE(cfg->use_metadata);
-    EXPECT_TRUE(cfg->metadata_explicitly_disabled);
+    EXPECT_TRUE(cfg->cli.metadata_explicitly_disabled);
     config_delete(cfg);
   }
 }
@@ -1777,7 +1777,7 @@ static void test_parse_args_checksum_choice_rejects_unsupported() {
     int positional_args[2];
     int positional_count = 0;
     EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), -1);
-    EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+    EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
     config_delete(cfg);
   }
 }
@@ -1817,7 +1817,7 @@ static void test_parse_args_checksum_choice_new_algos() {
     positional_count = 0;
     EXPECT_EQ_INT(parse_args(cfg, 5, argv4, positional_args, &positional_count), 0);
     EXPECT_EQ_INT(cfg->checksum_algo, single[i]);
-    EXPECT_EQ_INT(cfg->checksum_transfer_algo, single[i]);
+    EXPECT_EQ_INT(cfg->cli.checksum_transfer_algo, single[i]);
     config_delete(cfg);
   }
 
@@ -1827,7 +1827,7 @@ static void test_parse_args_checksum_choice_new_algos() {
   char* argv5[] = {"fastsync", "--cc=sha1,md4", "/checksum/src", "/dst"};
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv5, positional_args, &positional_count), 0);
-  EXPECT_EQ_INT(cfg->checksum_transfer_algo, (int)CHECKSUM_ALGO_SHA1);
+  EXPECT_EQ_INT(cfg->cli.checksum_transfer_algo, (int)CHECKSUM_ALGO_SHA1);
   EXPECT_EQ_INT(cfg->checksum_algo, (int)CHECKSUM_ALGO_MD4);
   config_delete(cfg);
 
@@ -1849,14 +1849,14 @@ static void test_parse_args_checksum_none_with_checksum_rejected() {
   int positional_args[2];
   int positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), -1);
-  EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+  EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
   config_delete(cfg);
 
   cfg = config_create();
   char* argv2[] = {"fastsync", "--checksum", "--cc=md5,none", "/checksum/src", "/dst"};
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 5, argv2, positional_args, &positional_count), -1);
-  EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+  EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
   config_delete(cfg);
 
   /* "none" as the TRANSFER checksum with a real pre-transfer checksum is
@@ -1958,7 +1958,7 @@ static void test_parse_args_compress_choice_parity() {
     int positional_args[2];
     int positional_count = 0;
     EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), -1);
-    EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+    EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
     config_delete(cfg);
   }
 }
@@ -2078,6 +2078,9 @@ static void test_parse_args_temp_dir() {
   config_delete(cfg);
 }
 
+/* --old-args is accepted for rsync CLI compatibility as a documented no-op (the
+ * remote server path is always safely quoted); it stores no Config field, so
+ * parsing it must simply succeed and leave the positional arguments intact. */
 static void test_parse_args_old_args() {
   Config* cfg = config_create();
   char* argv[] = {"fastsync", "--old-args", "/src", "/dst"};
@@ -2085,7 +2088,7 @@ static void test_parse_args_old_args() {
   int positional_count = 0;
 
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
-  EXPECT_TRUE(cfg->old_args);
+  EXPECT_EQ_INT(positional_count, 2);
   config_delete(cfg);
 }
 
@@ -2719,7 +2722,7 @@ static void test_parse_args_compression_env_list() {
   cfg = config_create();
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), -1);
-  EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+  EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
   config_delete(cfg);
   unsetenv("RSYNC_COMPRESS_LIST");
 }
@@ -2734,7 +2737,7 @@ static void test_parse_args_checksum_env_list() {
   setenv("RSYNC_CHECKSUM_LIST", "md5", 1);
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
   EXPECT_EQ_INT(cfg->checksum_algo, (int)CHECKSUM_ALGO_MD5);
-  EXPECT_EQ_INT(cfg->checksum_transfer_algo, (int)CHECKSUM_ALGO_MD5);
+  EXPECT_EQ_INT(cfg->cli.checksum_transfer_algo, (int)CHECKSUM_ALGO_MD5);
   config_delete(cfg);
 
   /* An explicit --cc wins. */
@@ -2750,7 +2753,7 @@ static void test_parse_args_checksum_env_list() {
   cfg = config_create();
   positional_count = 0;
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), -1);
-  EXPECT_EQ_INT(cfg->cli_exit_code, 4);
+  EXPECT_EQ_INT(cfg->cli.cli_exit_code, 4);
   config_delete(cfg);
   unsetenv("RSYNC_CHECKSUM_LIST");
 }
@@ -4385,7 +4388,7 @@ static void test_parse_args_preserve_long_form() {
 }
 
 /* --no-perms/--no-times/--no-owner/--no-group (long and short) clear only
- * their own attribute bit; they never set metadata_explicitly_disabled. */
+ * their own attribute bit; they never set cli.metadata_explicitly_disabled. */
 static void test_parse_args_preserve_negations() {
   struct {
     const char* arg;
@@ -4413,7 +4416,7 @@ static void test_parse_args_preserve_negations() {
       bool expected = all[j] != cases[i].offset;
       EXPECT_TRUE(*(bool*)((char*)cfg + all[j]) == expected);
     }
-    EXPECT_FALSE(cfg->metadata_explicitly_disabled);
+    EXPECT_FALSE(cfg->cli.metadata_explicitly_disabled);
     /* -a's devices/specials keep the metadata frame on. */
     EXPECT_TRUE(cfg->use_metadata);
     config_delete(cfg);
@@ -4456,7 +4459,7 @@ static void test_parse_args_no_preserve_disables_bundle() {
   EXPECT_FALSE(cfg->preserve_times);
   EXPECT_FALSE(cfg->preserve_owner);
   EXPECT_FALSE(cfg->preserve_group);
-  EXPECT_TRUE(cfg->metadata_explicitly_disabled);
+  EXPECT_TRUE(cfg->cli.metadata_explicitly_disabled);
   EXPECT_TRUE(cfg->use_incremental);
   EXPECT_FALSE(cfg->use_metadata);
   config_delete(cfg);
@@ -4509,7 +4512,7 @@ static void test_parse_args_incremental_implies_preserve() {
   EXPECT_EQ_INT(parse_args(cfg, 5, argv4, positional_args, &positional_count), 0);
   EXPECT_FALSE(cfg->preserve_perms);
   EXPECT_FALSE(cfg->preserve_times);
-  EXPECT_TRUE(cfg->metadata_explicitly_disabled);
+  EXPECT_TRUE(cfg->cli.metadata_explicitly_disabled);
   EXPECT_FALSE(cfg->use_metadata);
   config_delete(cfg);
 }
diff --git a/tests/test_config.c b/tests/test_config.c
index a801d70..4c87b34 100644
--- a/tests/test_config.c
+++ b/tests/test_config.c
@@ -2533,15 +2533,15 @@ static void test_config_derived_use_metadata() {
   /* Incremental/delta imply metadata unless --no-preserve disabled it. */
   c->use_incremental = true;
   EXPECT_TRUE(config_derived_use_metadata(c));
-  c->metadata_explicitly_disabled = true;
+  c->cli.metadata_explicitly_disabled = true;
   EXPECT_FALSE(config_derived_use_metadata(c));
-  c->metadata_explicitly_disabled = false;
+  c->cli.metadata_explicitly_disabled = false;
   c->use_incremental = false;
   c->use_delta = true;
   EXPECT_TRUE(config_derived_use_metadata(c));
-  c->metadata_explicitly_disabled = true;
+  c->cli.metadata_explicitly_disabled = true;
   EXPECT_FALSE(config_derived_use_metadata(c));
-  c->metadata_explicitly_disabled = false;
+  c->cli.metadata_explicitly_disabled = false;
   c->use_delta = false;
 
   /* Flags that must NOT imply metadata on their own. */