Fix regen: CSS-hidden textboxes + remove _rtrig from outputs to fix Too many args

- Replace visible=False textboxes with CSS-hidden (elem_classes=['wf-hidden-input'])
so Gradio 5 SSR renders them to the DOM (visible=False omits them entirely,
making getElementById return null and fireRegen silently fail)
- Remove regen trigger from regen handler outputs — having a .change() component
as its own output causes SSR argument count mismatch
- Drop 4th gr.update() from all regen yield statements to match 3-output list
- Add .wf-hidden-input CSS class: position absolute off-screen, opacity 0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -1409,19 +1409,24 @@ def _make_output_slots(tab_prefix: str) -> tuple:
             waveforms.append(gr.HTML(
                 value="<p style='color:#888;font-size:12px'>Generate audio to see waveform.</p>",
             ))
-            # Hidden textbox: JS writes "<slot_id>|<seg_idx>" to trigger regen
+            # Regen trigger: a Textbox that is CSS-hidden (NOT visible=False).
+            # Gradio 5 SSR omits visible=False components from the DOM entirely,
+            # so getElementById() returns null and JS can never fire the event.
+            # By keeping it visible=True but hiding with CSS (elem_classes),
+            # the input element exists in the DOM and JS can write to it.
             regen_triggers.append(gr.Textbox(
                 value="",
-                visible=False,
                 elem_id=f"regen_trigger_{slot_id}",
-                label=f"regen_trigger_{slot_id}",
+                elem_classes=["wf-hidden-input"],
+                label="",
+                show_label=False,
             ))
-            # Hidden JSON textbox instead of gr.State — Gradio 5 SSR counts
-            # gr.Textbox correctly in endpoint outputs but not gr.State.
+            # State textbox: also CSS-hidden for same reason.
             seg_states.append(gr.Textbox(
                 value="",
-                visible=False,
-                label=f"seg_state_{slot_id}",
+                elem_classes=["wf-hidden-input"],
+                label="",
+                show_label=False,
             ))
         grps.append(g)
     return grps, vids, waveforms, regen_triggers, seg_states
@@ -1487,6 +1492,18 @@ _SLOT_CSS = """
     max-height: 60vh !important;
     object-fit: contain;
 }
+/* Regen trigger and state textboxes are CSS-hidden, NOT visible=False.
+   Gradio 5 SSR omits visible=False components from the DOM entirely,
+   so JS can never find them. CSS-hidden components are always in the DOM. */
+.wf-hidden-input {
+    position: absolute !important;
+    left: -9999px !important;
+    width: 1px !important;
+    height: 1px !important;
+    overflow: hidden !important;
+    pointer-events: none !important;
+    opacity: 0 !important;
+}
 """
 
 _GLOBAL_JS = """
@@ -1529,35 +1546,27 @@ _GLOBAL_JS = """
   }
 
   function fireRegen(slot_id, idx) {
-    const hidden_id = 'regen_trigger_' + slot_id;
-    const el = document.getElementById(hidden_id);
-    if (!el) { console.warn('[fireRegen] element not found:', hidden_id); return; }
+    const el = document.getElementById('regen_trigger_' + slot_id);
+    if (!el) { console.warn('[fireRegen] element not found: regen_trigger_' + slot_id); return; }
     const input = el.querySelector('input, textarea');
-    if (!input) { console.warn('[fireRegen] no input inside', hidden_id); return; }
-
-    // Gradio 5 / React: must use the native setter to bypass React's controlled-
-    // input tracking, otherwise dispatchEvent is swallowed. Also must clear first
-    // so a repeat regen of the same segment triggers a value *change*.
-    const nativeInputDesc = Object.getOwnPropertyDescriptor(HTMLInputElement.prototype, 'value')
-                         || Object.getOwnPropertyDescriptor(HTMLTextAreaElement.prototype, 'value');
-    function setAndFire(val) {
-      if (nativeInputDesc && nativeInputDesc.set) {
-        nativeInputDesc.set.call(input, val);
-      } else {
-        input.value = val;
-      }
+    if (!input) { console.warn('[fireRegen] no input inside regen_trigger_' + slot_id); return; }
+
+    // Use native setter to bypass React's controlled-input tracking.
+    // Clear to '' first so a repeat click on the same segment still fires .change().
+    const desc = Object.getOwnPropertyDescriptor(HTMLInputElement.prototype, 'value')
+              || Object.getOwnPropertyDescriptor(HTMLTextAreaElement.prototype, 'value');
+    function setNative(val) {
+      if (desc && desc.set) desc.set.call(input, val);
+      else input.value = val;
       input.dispatchEvent(new Event('input',  {bubbles: true}));
       input.dispatchEvent(new Event('change', {bubbles: true}));
     }
-
-    // Clear first so even a repeated click on the same segment fires a change
-    setAndFire('');
+    setNative('');
     setTimeout(function() {
-      setAndFire(slot_id + '|' + idx);
+      setNative(slot_id + '|' + idx);
       console.log('[fireRegen] fired', slot_id + '|' + idx);
     }, 50);
 
-    // Update status label
     const lbl = document.getElementById('wf_seglabel_' + slot_id);
     if (lbl) lbl.textContent = 'Regenerating Seg ' + (idx + 1) + '...';
   }
@@ -1662,11 +1671,11 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                         print(f"[regen TARO] trigger_val={trigger_val!r} state_json_len={len(state_json) if state_json else 0} video={video!r}")
                         if not trigger_val or not state_json:
                             print(f"[regen TARO] early-exit: trigger_val empty={not trigger_val} state empty={not state_json}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         parts = trigger_val.split("|")
                         if len(parts) != 2 or parts[0] != _sid:
                             print(f"[regen TARO] early-exit: parts={parts} expected slot={_sid}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         seg_idx = int(parts[1])
                         print(f"[regen TARO] slot={_sid} seg_idx={seg_idx} — acquiring lock")
                         lock = _get_slot_lock(_sid)
@@ -1677,7 +1686,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                                 state["segments"], seg_idx, _sid,
                                 f"regen_trigger_{_sid}"
                             )
-                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json), gr.update()
+                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json)
                             print(f"[regen TARO] slot={_sid} seg_idx={seg_idx} — calling regen_taro_segment")
                             try:
                                 vid, aud, new_meta_json, html = regen_taro_segment(
@@ -1688,14 +1697,13 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                             except Exception as _e:
                                 print(f"[regen TARO] slot={_sid} seg_idx={seg_idx} — ERROR: {_e}")
                                 raise
-                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json), gr.update(value="")
+                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json)
                     return _do
                 _rtrig.change(
                     fn=_make_taro_regen(_i, _slot_id),
                     inputs=[_rtrig, taro_video, taro_seed, taro_cfg, taro_steps,
                             taro_mode, taro_cf_dur, taro_cf_db, taro_slot_states[_i]],
-                    outputs=[taro_slot_vids[_i], taro_slot_waves[_i],
-                             taro_slot_states[_i], _rtrig],
+                    outputs=[taro_slot_vids[_i], taro_slot_waves[_i], taro_slot_states[_i]],
                 )
 
         # ---------------------------------------------------------- #
@@ -1753,11 +1761,11 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                         print(f"[regen MMA] trigger_val={trigger_val!r} state_json_len={len(state_json) if state_json else 0} video={video!r}")
                         if not trigger_val or not state_json:
                             print(f"[regen MMA] early-exit: trigger_val empty={not trigger_val} state empty={not state_json}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         parts = trigger_val.split("|")
                         if len(parts) != 2 or parts[0] != _sid:
                             print(f"[regen MMA] early-exit: parts={parts} expected slot={_sid}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         seg_idx = int(parts[1])
                         print(f"[regen MMA] slot={_sid} seg_idx={seg_idx} — acquiring lock")
                         lock = _get_slot_lock(_sid)
@@ -1768,7 +1776,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                                 state["segments"], seg_idx, _sid,
                                 f"regen_trigger_{_sid}"
                             )
-                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json), gr.update()
+                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json)
                             print(f"[regen MMA] slot={_sid} seg_idx={seg_idx} — calling regen_mmaudio_segment")
                             try:
                                 vid, aud, new_meta_json, html = regen_mmaudio_segment(
@@ -1779,14 +1787,13 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                             except Exception as _e:
                                 print(f"[regen MMA] slot={_sid} seg_idx={seg_idx} — ERROR: {_e}")
                                 raise
-                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json), gr.update(value="")
+                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json)
                     return _do
                 _rtrig.change(
                     fn=_make_mma_regen(_i, _slot_id),
                     inputs=[_rtrig, mma_video, mma_prompt, mma_neg, mma_seed,
                             mma_cfg, mma_steps, mma_cf_dur, mma_cf_db, mma_slot_states[_i]],
-                    outputs=[mma_slot_vids[_i], mma_slot_waves[_i],
-                             mma_slot_states[_i], _rtrig],
+                    outputs=[mma_slot_vids[_i], mma_slot_waves[_i], mma_slot_states[_i]],
                 )
 
         # ---------------------------------------------------------- #
@@ -1845,11 +1852,11 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                         print(f"[regen HF] trigger_val={trigger_val!r} state_json_len={len(state_json) if state_json else 0} video={video!r}")
                         if not trigger_val or not state_json:
                             print(f"[regen HF] early-exit: trigger_val empty={not trigger_val} state empty={not state_json}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         parts = trigger_val.split("|")
                         if len(parts) != 2 or parts[0] != _sid:
                             print(f"[regen HF] early-exit: parts={parts} expected slot={_sid}")
-                            return gr.update(), gr.update(), gr.update(value=""), gr.update()
+                            return gr.update(), gr.update(), gr.update(value="")
                         seg_idx = int(parts[1])
                         print(f"[regen HF] slot={_sid} seg_idx={seg_idx} — acquiring lock")
                         lock = _get_slot_lock(_sid)
@@ -1860,7 +1867,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                                 state["segments"], seg_idx, _sid,
                                 f"regen_trigger_{_sid}"
                             )
-                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json), gr.update()
+                            yield gr.update(), gr.update(value=pending_html), gr.update(value=state_json)
                             print(f"[regen HF] slot={_sid} seg_idx={seg_idx} — calling regen_hunyuan_segment")
                             try:
                                 vid, aud, new_meta_json, html = regen_hunyuan_segment(
@@ -1871,14 +1878,13 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                             except Exception as _e:
                                 print(f"[regen HF] slot={_sid} seg_idx={seg_idx} — ERROR: {_e}")
                                 raise
-                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json), gr.update(value="")
+                            yield gr.update(value=vid), gr.update(value=html), gr.update(value=new_meta_json)
                     return _do
                 _rtrig.change(
                     fn=_make_hf_regen(_i, _slot_id),
                     inputs=[_rtrig, hf_video, hf_prompt, hf_neg, hf_seed,
                             hf_guidance, hf_steps, hf_size, hf_cf_dur, hf_cf_db, hf_slot_states[_i]],
-                    outputs=[hf_slot_vids[_i], hf_slot_waves[_i],
-                             hf_slot_states[_i], _rtrig],
+                    outputs=[hf_slot_vids[_i], hf_slot_waves[_i], hf_slot_states[_i]],
                 )
 
     # ---- Cross-tab video sync ----