Fix Switch OTA launcher self-update via a bootstrap NRO.

A running launcher cannot replace its own NRO on sdmc/FAT; stage the new
binary and chainload a tiny helper from romfs to swap it in before loading
the game.

native/switch-ota-launcher/Makefile

@@ -130,7 +130,10 @@ ifneq ($(ROMFS),)
 	export NROFLAGS += --romfsdir=$(CURDIR)/$(ROMFS)
 endif
 
-.PHONY: $(BUILD) clean all host-test sync-romfs
+BOOTSTRAP_DIR	:=	$(TOPDIR)/../switch-ota-bootstrap
+BOOTSTRAP_ROMFS	:=	$(CURDIR)/$(ROMFS)/ota-bootstrap.nro
+
+.PHONY: $(BUILD) clean all host-test sync-romfs bootstrap-romfs
 
 #---------------------------------------------------------------------------------
 all: sync-romfs $(BUILD)
@@ -138,7 +141,12 @@ all: sync-romfs $(BUILD)
 CACERT_URL	:=	https://curl.se/ca/cacert.pem
 CACERT_ROMFS	:=	$(CURDIR)/$(ROMFS)/cacert.pem
 
-sync-romfs:
+bootstrap-romfs:
+	@$(MAKE) --no-print-directory -C $(BOOTSTRAP_DIR) all
+	@mkdir -p $(CURDIR)/$(ROMFS)
+	@cp -f $(BOOTSTRAP_DIR)/ota-bootstrap.nro $(BOOTSTRAP_ROMFS)
+
+sync-romfs: bootstrap-romfs
 	@mkdir -p $(CURDIR)/$(ROMFS)
 	@cp -f $(LOGO_SRC) $(CURDIR)/$(ROMFS)/logo.png
 	@if ! curl -sfL --time-cond $(CACERT_ROMFS) -o $(CACERT_ROMFS) $(CACERT_URL); then \

native/switch-ota-launcher/README.md

@@ -68,7 +68,10 @@ Manifest: `scripts/switch/ota_launcher.manifest`.
 ## Status / known gaps
 
 - Zip extraction uses `switch-zziplib` (`ota_unzip.c`) on device.
-- OTA replaces launcher + game from the install zip (NACP versions stay aligned).
+- OTA replaces game + launcher from the install zip (NACP versions stay aligned).
+  The running launcher cannot overwrite its own NRO on sdmc/FAT; a tiny
+  `ota-bootstrap.nro` (embedded in romfs) chainloads once to swap the staged
+  launcher, then loads the game.
 - HTTPS uses Mozilla CA bundle in romfs (`cacert.pem`, fetched at build time). `ota_net_init()` mounts romfs before the quiet release check.
 - Sphaira HOME forwarders cache metadata until reinstalled (see docs/switch-install.md).
 - Release runner: `switch-dev` + (`install_devkitpro_deps.sh` **or** Docker)

native/switch-ota-launcher/include/ota_fs.h

@@ -22,6 +22,12 @@ int ota_fs_atomic_replace_game(const char *install_dir, const char *verified_gam
 int ota_fs_atomic_replace_nro(const char *install_dir, const char *nro_name,
                               const char *verified_nro, char *err, size_t err_len);
 
+/* Stage a new launcher + copy romfs bootstrap; chainload bootstrap_out next.
+ * The running launcher cannot replace its own NRO on sdmc/FAT. */
+int ota_fs_stage_launcher_bootstrap(const char *install_dir, const char *verified_launcher,
+                                    char *bootstrap_out, size_t bootstrap_out_len, char *err,
+                                    size_t err_len);
+
 /* Hand off to game NRO via envSetNextLoad (Switch) or no-op stub (host). */
 int ota_fs_handoff_to_game(const char *game_nro_path, char *err, size_t err_len);
 

native/switch-ota-launcher/include/ota_protocol.h

@@ -12,6 +12,9 @@ extern "C" {
 #define OTA_LAUNCHER_NRO_NAME "gen1recomp.nro"
 #define OTA_SAVE_DIR_NAME "pokemon-love2d"
 #define OTA_INSTALL_DIR "switch/gen1recomp"
+#define OTA_LAUNCHER_STAGED_SUFFIX ".staged"
+#define OTA_BOOTSTRAP_ROMFS "romfs:/ota-bootstrap.nro"
+#define OTA_BOOTSTRAP_SD_NAME "ota-bootstrap.nro"
 #define OTA_RELEASES_API \
   "https://api.github.com/repos/bryanthaboi/gen1recomp/releases/latest"
 

native/switch-ota-launcher/src/main.c

@@ -198,12 +198,15 @@ static int run_update_flow(const char *install_dir) {
                       "Update zip is missing launcher files.", err, installed);
     return 0;
   }
-  if (ota_fs_atomic_replace_nro(install_dir, OTA_LAUNCHER_NRO_NAME, extracted_launcher, err,
-                                sizeof(err)) != 0) {
+
+  char bootstrap_path[256];
+  bootstrap_path[0] = '\0';
+  if (ota_fs_stage_launcher_bootstrap(install_dir, extracted_launcher, bootstrap_path,
+                                      sizeof(bootstrap_path), err, sizeof(err)) != 0) {
     remove(extracted_launcher);
     remove(zip_path);
     show_update_error("Could not install",
-                      "Game updated but launcher could not be replaced. Reinstall from the SD zip.",
+                      "Game updated but launcher could not be staged. Reinstall from the SD zip.",
                       err, installed);
     return 0;
   }
@@ -217,8 +220,16 @@ static int run_update_flow(const char *install_dir) {
     fclose(vf);
   }
 
-  ota_ui_show_progress("Ready", "Starting the game...", 1.0f);
+  ota_ui_show_progress("Ready", "Finishing update...", 1.0f);
   svcSleepThread(600000000ULL);
+  remove(zip_path);
+  ota_ui_shutdown();
+
+  if (ota_fs_handoff_to_game(bootstrap_path, err, sizeof(err)) != 0) {
+    show_update_error("Could not install", "Launcher bootstrap failed.", err, installed);
+    return 0;
+  }
+  return 2; /* chainload bootstrap; main must not hand off to game */
 #else
   (void)extracted;
   (void)extracted_launcher;
@@ -233,18 +244,26 @@ int main(int argc, char **argv) {
   (void)argv;
 
   const char *install = SD_INSTALL_DIR;
+  int update_rc = 0;
 
 #if defined(__SWITCH__)
   socketInitializeDefault();
   padConfigureInput(1, HidNpadStyleSet_NpadStandard);
   if (ota_net_init() == 0) {
-    run_update_flow(install);
+    update_rc = run_update_flow(install);
     ota_net_shutdown();
   }
 #else
-  run_update_flow(install);
+  update_rc = run_update_flow(install);
 #endif
 
+  if (update_rc == 2) {
+#if defined(__SWITCH__)
+    socketExit();
+#endif
+    return 0;
+  }
+
   char game[192];
   snprintf(game, sizeof(game), "%s/%s", install, OTA_GAME_NRO_NAME);
   char err[128];

native/switch-ota-launcher/src/ota_fs.c

@@ -7,6 +7,7 @@
 #if defined(__SWITCH__)
 #include <switch.h>
 #include <mbedtls/sha256.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #else
 #include <unistd.h>
@@ -114,6 +115,47 @@ int ota_fs_atomic_replace_nro(const char *install_dir, const char *nro_name,
   return 0;
 }
 
+int ota_fs_stage_launcher_bootstrap(const char *install_dir, const char *verified_launcher,
+                                    char *bootstrap_out, size_t bootstrap_out_len, char *err,
+                                    size_t err_len) {
+  if (!verified_launcher || !*verified_launcher) {
+    if (err && err_len) snprintf(err, err_len, "missing staged launcher path");
+    return -1;
+  }
+  if (!bootstrap_out || bootstrap_out_len == 0) {
+    if (err && err_len) snprintf(err, err_len, "missing bootstrap output buffer");
+    return -1;
+  }
+  bootstrap_out[0] = '\0';
+
+  const char *base = install_dir ? install_dir : OTA_INSTALL_DIR;
+  char staged[256];
+  char bootstrap[256];
+  char updates[192];
+  snprintf(staged, sizeof(staged), "%s/%s%s", base, OTA_LAUNCHER_NRO_NAME,
+           OTA_LAUNCHER_STAGED_SUFFIX);
+  snprintf(updates, sizeof(updates), "%s/updates", base);
+  snprintf(bootstrap, sizeof(bootstrap), "%s/updates/%s", base, OTA_BOOTSTRAP_SD_NAME);
+
+  remove(staged);
+  if (copy_file(verified_launcher, staged) != 0) {
+    if (err && err_len) snprintf(err, err_len, "stage launcher failed");
+    return -1;
+  }
+
+#if defined(__SWITCH__)
+  mkdir(updates, 0755);
+#endif
+  if (copy_file(OTA_BOOTSTRAP_ROMFS, bootstrap) != 0) {
+    remove(staged);
+    if (err && err_len) snprintf(err, err_len, "extract bootstrap failed");
+    return -1;
+  }
+
+  snprintf(bootstrap_out, bootstrap_out_len, "%s", bootstrap);
+  return 0;
+}
+
 int ota_fs_handoff_to_game(const char *game_nro_path, char *err, size_t err_len) {
   if (!game_nro_path || !*game_nro_path) {
     if (err && err_len) snprintf(err, err_len, "missing game path");