diff --git a/ESP32_ZACUS b/ESP32_ZACUS
index a4efce4..5519ed2 160000
--- a/ESP32_ZACUS
+++ b/ESP32_ZACUS
@@ -1 +1 @@
-Subproject commit a4efce4c200b4215e6b68a6d834cbbe7b9885b07
+Subproject commit 5519ed2f724cc2460bd440b47d6b69441e958341
diff --git a/tools/gamebook/build_gamebook.py b/tools/gamebook/build_gamebook.py
index 8cb5ee0..5298945 100644
--- a/tools/gamebook/build_gamebook.py
+++ b/tools/gamebook/build_gamebook.py
@@ -114,7 +114,8 @@ def narration(text: str, choices: list[dict]) -> str:
     return " ".join(parts)
 
 
-def build_book(path: Path, force: bool, dry: bool, ip: str) -> dict | None:
+def build_book(path: Path, force: bool, dry: bool, ip: str,
+               json_only: bool = False) -> dict | None:
     """Synthesise + (optionally) stage one book. Returns its library entry."""
     bid = path.stem
     book = yaml.safe_load(path.read_text())
@@ -133,8 +134,9 @@ def build_book(path: Path, force: bool, dry: bool, ip: str) -> dict | None:
                 print(f"  ! {bid}/{pid} -> '{c['goto']}' inconnu"); return None
         wav = f"{bid}_{pid}.wav"
         out = OUT_DIR / wav
-        if not say_wav(narration(p["text"], choices), voice, out, force):
-            print(f"  ✗ synth {bid}/{pid}"); n_fail += 1; continue
+        if not json_only:                      # text-only (BOX-3 touch) skips audio
+            if not say_wav(narration(p["text"], choices), voice, out, force):
+                print(f"  ✗ synth {bid}/{pid}"); n_fail += 1; continue
         n_ok += 1
         manifest["passages"][pid] = {
             "wav": wav,
@@ -143,7 +145,7 @@ def build_book(path: Path, force: bool, dry: bool, ip: str) -> dict | None:
             "choices": [{"label": fold(c["label"])[:38], "goto": c["goto"]}
                         for c in choices],
         }
-        if not dry:
+        if not dry and not json_only:
             good, _ = push(ip, wav, out.read_bytes())
             n_push += 1 if good else 0
             n_fail += 0 if good else 1
@@ -162,9 +164,11 @@ def build_book(path: Path, force: bool, dry: bool, ip: str) -> dict | None:
 def main() -> int:
     ap = argparse.ArgumentParser(description=__doc__,
                                  formatter_class=argparse.RawDescriptionHelpFormatter)
-    ap.add_argument("--ip", default="192.168.0.188", help="master IP (default .188)")
+    ap.add_argument("--ip", default="192.168.0.188", help="board IP (default .188)")
     ap.add_argument("--force", action="store_true", help="re-synthesise cached WAVs")
     ap.add_argument("--dry-run", action="store_true", help="synthesise only, no push")
+    ap.add_argument("--json-only", action="store_true",
+                    help="build/push only the JSON (no WAVs) — for the BOX-3 touch UI")
     args = ap.parse_args()
 
     books = sorted(p for p in BOOKS_DIR.glob("*.yaml") if p.stem not in EXCLUDE)
@@ -176,7 +180,7 @@ def main() -> int:
 
     entries, fail = [], 0
     for path in books:
-        e = build_book(path, args.force, args.dry_run, args.ip)
+        e = build_book(path, args.force, args.dry_run, args.ip, args.json_only)
         if e is None:
             fail += 1
             continue