fix: clarify secluded args compatibility semantics

README.md

@@ -89,7 +89,7 @@ partial, alternate, and planned behavior.
 | `-a, --archive` | Archive mode: enables `-c -m -M` (no `-s`) |
 | `-m` | Multithreading mode |
 | `-s` | Chunk serialization (batch all files per chunk) |
-| `--secluded-args` | Rsync-compatible long form. SSH already sends transfer arguments through FastSync's protocol; `-s` remains chunk serialization. |
+| `--secluded-args` | Accepted as an rsync compatibility option with no effect; `-s` remains chunk serialization. |
 | `-f, --sendfile` | Sendfile zero-copy. Incompatible with `-c` / `-s`. TCP only. |
 | `-M, --preserve` | Preserve supported file metadata (mode and mtime; ownership and atime are unsupported) |
 | `-n, --dry-run` | Scan and print what would be transferred |
@@ -360,10 +360,9 @@ particular, FastSync currently uses `-p` for SSH port, `-s` for chunk
 serialization, and `-S` for sparse handling. These meanings must be reconciled
 before FastSync can claim full rsync CLI compatibility.
 
-`--secluded-args` is supported as a long-form compatibility option. FastSync's
+`--secluded-args` is accepted as a long-form compatibility no-op. It does not
-SSH transport already launches only the remote server's `--stdio` command and
+change FastSync's transport or protocol behavior. The rsync short form `-s` is
-sends transfer configuration through its protocol. The rsync short form `-s`
+intentionally not aliased because it remains FastSync's chunk-serialization
-is intentionally not aliased because it remains FastSync's chunk-serialization
 option.
 
 ## Client Options

RSYNC_COMPAT.md

@@ -6,9 +6,10 @@ This document maps rsync's full feature set to FastSync's current implementation
 
 | Status | Count | Description |
 |--------|-------|-------------|
-| ✅ Implemented | 34 | Feature works end-to-end |
+| ✅ Implemented | 33 | Feature works end-to-end |
 | 🔀 Alt Arg | 3 | Functionality exists but under different flag/semantics |
 | ⚠️ Partial | 1 | Flag parsed/stored but behavior incomplete |
+| 🔄 Compatibility No-op | 1 | Flag is accepted for CLI compatibility but has no effect |
 | ❌ Not Implemented | 98 | Flag not recognized or no behavior |
 | **Total** | **136** | |
 
@@ -233,7 +234,7 @@ This document maps rsync's full feature set to FastSync's current implementation
 | `--protocol=NUM` | Force older protocol version | ❌ Not Implemented | |
 | `--iconv=CONVERT_SPEC` | Charset conversion | ❌ Not Implemented | |
 | `--checksum-seed=NUM` | Set checksum seed | ❌ Not Implemented | |
-| `--secluded-args` | Use protocol to send args | ✅ Implemented | SSH already sends transfer configuration through FastSync's protocol; `-s` remains chunk serialization because of the existing FastSync short-option meaning. |
+| `--secluded-args` | Use protocol to send args | 🔄 Compatibility No-op | Accepted for CLI compatibility; it does not change FastSync transport or protocol behavior. `-s` remains chunk serialization. |
 | `--no-OPTION` | Turn off implied option | ❌ Not Implemented | |
 
 ---

src/client/client_cli.c

@@ -121,6 +121,7 @@ static int config_add_pattern(char*** patterns, int* count, const char* value,
 
 typedef enum {
   OPT_FLAG,
+  OPT_NOOP,
   OPT_STRING,
   OPT_POS_INT,
   OPT_NONNEG_INT,
@@ -131,10 +132,10 @@ typedef struct {
   const char* name;
   const char* alias;
   OptKind kind;
-  size_t offset; /* offsetof of the target field in Config */
+  size_t offset; /* offsetof of the target field in Config, or 0 for OPT_NOOP */
 } OptionEntry;
 
-/* Options that map directly onto a Config field with no side effects. */
+/* Options parsed directly into Config, plus compatibility options with no effect. */
 static const OptionEntry OPTION_TABLE[] = {
     {"--dry-run", "-n", OPT_FLAG, offsetof(Config, dry_run)},
     {"--delete", NULL, OPT_FLAG, offsetof(Config, use_delete)},
@@ -146,7 +147,7 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--backup", NULL, OPT_FLAG, offsetof(Config, backup)},
     {"--stats", NULL, OPT_FLAG, offsetof(Config, stats)},
     {"--partial", NULL, OPT_FLAG, offsetof(Config, partial)},
-    {"--secluded-args", NULL, OPT_FLAG, offsetof(Config, use_secluded_args)},
+    {"--secluded-args", NULL, OPT_NOOP, 0},
     {"--links", "-l", OPT_FLAG, offsetof(Config, follow_symlinks)},
     {"--copy-links", NULL, OPT_FLAG, offsetof(Config, copy_links)},
     {"--safe-links", NULL, OPT_FLAG, offsetof(Config, safe_links)},
@@ -186,11 +187,16 @@ static const OptionEntry* find_table_option(const char* arg) {
 }
 
 static int apply_table_option(Config* config, const OptionEntry* entry, const char* value) {
+  if (entry->kind == OPT_NOOP)
+    return 0;
+
   void* field = (char*)config + entry->offset;
   switch (entry->kind) {
   case OPT_FLAG:
     *(bool*)field = true;
     return 0;
+  case OPT_NOOP:
+    return 0;
   case OPT_STRING:
     return set_string_option((char**)field, value, entry->name);
   case OPT_POS_INT:

src/client/usage.c

@@ -35,7 +35,7 @@ void print_usage(void) {
          DELTA_MAX_FILE_SIZE);
   printf("  -m                  Enable multithreading\n");
   printf("  -s                  Enable chunk serialization\n");
-  printf("  --secluded-args    Send transfer arguments through the protocol (SSH)\n");
+  printf("  --secluded-args    Accept rsync compatibility option (no effect)\n");
   printf("  -f                  Enable sendfile (TCP only, not with -c or -s)\n");
   printf("  -v, --verbose       Enable debug logging\n");
   printf("  -M, --preserve      Preserve file metadata\n");

src/shared/config.c

@@ -82,7 +82,6 @@ static void config_set_defaults(Config* config) {
   config->relative = false;
   config->rsh_command = NULL;
   config->rsync_path = NULL;
-  config->use_secluded_args = false;
   config->temp_dir = NULL;
   config->compare_dest = NULL;
   config->copy_dest = NULL;

src/shared/config.h

@@ -96,7 +96,6 @@ typedef struct Config {
   // Issue #130: Remote shell/connection options
   char* rsh_command;
   char* rsync_path;
-  bool use_secluded_args;
   char* temp_dir;
   char* compare_dest;
   char* copy_dest;

tests/test_client_cli.c

@@ -339,7 +339,7 @@ static void test_parse_args_archive() {
   config_delete(cfg);
 }
 
-/* --secluded-args is the rsync-compatible long form; -s keeps its FastSync meaning. */
+/* --secluded-args is accepted for compatibility but has no effect. */
 static void test_parse_args_secluded_args() {
   Config* cfg = config_create();
   char* argv[] = {"fastsync", "--secluded-args", "/src", "/dst"};
@@ -347,7 +347,6 @@ static void test_parse_args_secluded_args() {
   int positional_count = 0;
 
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
-  EXPECT_TRUE(cfg->use_secluded_args);
   EXPECT_FALSE(cfg->use_chunk_serialization);
   config_delete(cfg);
 }
@@ -360,7 +359,6 @@ static void test_parse_args_short_s_remains_chunk_serialization() {
 
   EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
   EXPECT_TRUE(cfg->use_chunk_serialization);
-  EXPECT_FALSE(cfg->use_secluded_args);
   config_delete(cfg);
 }