fix: the H3 v2a hint only fires when JoyAI audio memory is on; guard the inputs too

Two things, both from the same debugging session.

v2a_grad_scale is JoyAI's coupling knob and is never installed without
joyai_audio_memory (see the call site), so a left-over value with the feature
off was being reported as an H3 limitation — blaming the model for a knob that
would be equally inert on LTX. Both the sampler's pre-run notice and the
Editor's inert-setting hint now gate on joyai_audio_memory.

The NaN guard only saw the sampler's OUTPUT, which cannot tell "the model
computed garbage" from "the model was handed garbage and propagated it" — and
those have disjoint suspect lists. _sample_chunk now checks the incoming latent
and the schedule first, and says which it was. The schedule check is there
because it is hand-typed and our solvers divide by sigma (er = sigma_next /
sigma): an interior zero or a repeated value is an instant Inf that poisons
every value downstream. A trailing zero stays legal — it is only ever a step's
target, never a divisor.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

movie_editor/frontend/pipeline_caps.js

@@ -106,7 +106,10 @@
   // Same idea for non-boolean knobs whose neutral value means "off".
   function h3DeadValueIssues(si) {
     const out = [];
-    if (Math.abs(Number(si.v2a_grad_scale ?? 1) - 1) > 1e-6) {
+    // Only when joyai_audio_memory is on: v2a_grad_scale is that feature's coupling knob and
+    // does nothing without it on ANY model, so flagging a left-over value as an H3 limitation
+    // blames the wrong thing — it would be equally inert on LTX.
+    if (si.joyai_audio_memory && Math.abs(Number(si.v2a_grad_scale ?? 1) - 1) > 1e-6) {
       out.push(["v2a_grad_scale",
         "v2a_grad_scale scales LTXAV's video→audio cross-attention module; H3 has no separate "
         + "video→audio attention, only joint rows."]);

samplers.py

@@ -3037,6 +3037,71 @@ class FunPackLTXAVSceneChainSampler:
         except Exception:  # noqa: BLE001
             return ""
 
+    def _nonfinite_report(self, samples):
+        """['video (12/1000 values, dtype=...)'] for each stream carrying NaN/Inf. Empty when
+        clean, and empty when the latent is not readable — the check must never be the thing
+        that kills a render."""
+        try:
+            tensors = self._latent_tensors({"samples": samples})
+        except Exception:  # noqa: BLE001
+            return []
+        names = ("video", "audio")
+        bad = []
+        for i, t in enumerate(tensors):
+            if not isinstance(t, torch.Tensor):
+                continue
+            finite = torch.isfinite(t)
+            if bool(finite.all()):
+                continue
+            n_bad = int((~finite).sum().item())
+            label = names[i] if i < len(names) else f"stream {i}"
+            bad.append(f"{label} ({n_bad}/{t.numel()} values, dtype={t.dtype})")
+        return bad
+
+    def _assert_finite_inputs(self, samples, sigmas):
+        """Check what the chunk is ABOUT TO be sampled from, so a corrupt run says whether the
+        damage arrived or was produced here.
+
+        Without this the output check alone cannot tell "the model computed garbage" from "the
+        model was handed garbage and faithfully propagated it" — and those have disjoint
+        suspect lists. The schedule is checked too because it is hand-typed: our own solvers
+        divide by sigma (er = sigma_next / sigma), so an INTERIOR zero or a repeat is an
+        instant Inf that then poisons every value in the tensor. A trailing zero is fine — it
+        is only ever the target of the last step, never a divisor.
+        """
+        where = self._current_phase_label() or "this chunk"
+        bad = self._nonfinite_report(samples)
+        if bad:
+            raise RuntimeError(
+                f"[FunPackSceneChain] {where}: the latent handed to the sampler is ALREADY "
+                f"non-finite before any sampling — {'; '.join(bad)}. The model has not run "
+                f"yet, so this is not the checkpoint, the LoRA or the sampler. Look at what "
+                f"produced this latent: the empty-latent node, the i2v anchor encode, or (on "
+                f"a later scene) the previous scene's output."
+            )
+        if not isinstance(sigmas, torch.Tensor) or sigmas.numel() < 2:
+            return
+        s = sigmas.detach().float().reshape(-1).cpu()
+        if not bool(torch.isfinite(s).all()):
+            raise RuntimeError(
+                f"[FunPackSceneChain] {where}: the sigma schedule contains NaN/Inf "
+                f"({[float(v) for v in s]}). Fix the schedule — nothing downstream can."
+            )
+        interior = s[:-1]
+        if bool((interior <= 0).any()):
+            raise RuntimeError(
+                f"[FunPackSceneChain] {where}: the sigma schedule has a zero or negative "
+                f"value before its last entry ({[float(v) for v in s]}). Every value except "
+                f"the final one is divided by, so this produces Inf on that step and NaN "
+                f"everywhere after it. Only the LAST sigma may be 0."
+            )
+        if bool((s[1:] >= s[:-1]).any()):
+            raise RuntimeError(
+                f"[FunPackSceneChain] {where}: the sigma schedule is not strictly "
+                f"descending ({[float(v) for v in s]}). A repeated value makes a zero-length "
+                f"step the solvers divide by; an ascending one integrates backwards."
+            )
+
     def _assert_finite_sample(self, sampled):
         """Stop the run the moment a chunk comes back with NaN/Inf in it.
 
@@ -3049,28 +3114,14 @@ class FunPackLTXAVSceneChainSampler:
         A non-finite latent is unrecoverable, so this raises rather than warns. One
         isfinite() per chunk against a multi-second sample is not a cost worth weighing.
         """
-        try:
-            tensors = self._latent_tensors({"samples": sampled})
-        except Exception:  # noqa: BLE001 — never fail the run over the check itself
-            return
-        names = ("video", "audio")
-        bad = []
-        for i, t in enumerate(tensors):
-            if not isinstance(t, torch.Tensor):
-                continue
-            finite = torch.isfinite(t)
-            if bool(finite.all()):
-                continue
-            n_bad = int((~finite).sum().item())
-            label = names[i] if i < len(names) else f"stream {i}"
-            bad.append(f"{label} ({n_bad}/{t.numel()} values, dtype={t.dtype})")
+        bad = self._nonfinite_report(sampled)
         if not bad:
             return
         where = self._current_phase_label() or "this chunk"
         raise RuntimeError(
             f"[FunPackSceneChain] {where}: the sampler returned a non-finite latent — "
-            f"{'; '.join(bad)}. Sampling itself ran to completion, so this is corrupt "
-            f"MATH, not a wiring or memory problem. Usual causes, in the order worth "
+            f"{'; '.join(bad)}. Its inputs were checked and were clean, so this was produced "
+            f"HERE, by the model or the sampler math. Usual causes, in the order worth "
             f"testing: a LoRA that does not match this checkpoint (ComfyUI logs the keys "
             f"it could not apply at load — check the log), a base checkpoint whose layout "
             f"the loader mis-inferred (third-party repacks of quantised weights are the "
@@ -3089,6 +3140,7 @@ class FunPackLTXAVSceneChainSampler:
             raise ValueError("sigmas input must be a SIGMAS tensor.")
         latent = self._clone_latent(latent)
         samples = latent["samples"]
+        self._assert_finite_inputs(samples, sigmas)
         noise = comfy.sample.prepare_noise(samples, int(seed))
 
         def _progress_cb(step, _denoised, _x, _total_steps):
@@ -5488,7 +5540,12 @@ class FunPackLTXAVSceneChainSampler:
                              "against LTX's 4096-wide cross-attention context, and the overlap "
                              "tokens need LTX's patchifier; H3's native ref2va reference blocks "
                              "are the equivalent and are not wired yet)")
-            if v2a_grad_scale is not None and abs(float(v2a_grad_scale) - 1.0) > 1e-6:
+            # Gated on joyai_audio_memory, not on the value alone: v2a_grad_scale is that
+            # feature's coupling knob and is never installed without it (see the call site),
+            # so reporting a left-over value as an H3 limitation blames the model for a knob
+            # that would be equally inert on LTX.
+            if (joyai_audio_memory and v2a_grad_scale is not None
+                    and abs(float(v2a_grad_scale) - 1.0) > 1e-6):
                 _dead.append("v2a_grad_scale (hooks LTXAV's video_to_audio_attn submodule; H3 "
                              "has no separate video->audio cross-attention to scale)")
             if segmented_detailing:

tests/test_finite_sample_guard.py

@@ -60,3 +60,58 @@ def test_the_check_never_fails_the_run_on_its_own(node):
     """A latent shape the helper cannot read is not a reason to kill a good render."""
     node._assert_finite_sample("not a tensor")
     node._assert_finite_sample(None)
+
+
+# ── inputs ────────────────────────────────────────────────────────────────────
+# The output check alone cannot tell "the model computed garbage" from "the model was handed
+# garbage and propagated it faithfully", and those have disjoint suspect lists.
+
+def _sigmas(*vals):
+    return torch.tensor(list(vals), dtype=torch.float32)
+
+
+def test_clean_inputs_pass(node):
+    node._assert_finite_inputs(torch.zeros(1, 4, 2, 8, 8), _sigmas(1.0, 0.5, 0.0))
+
+
+def test_a_latent_that_arrives_nan_blames_its_producer_not_the_model(node):
+    x = torch.zeros(1, 4, 2, 8, 8)
+    x[0, 0, 0, 0, 0] = float("nan")
+    with pytest.raises(RuntimeError) as e:
+        node._assert_finite_inputs(x, _sigmas(1.0, 0.0))
+    msg = str(e.value)
+    assert "ALREADY" in msg
+    assert "has not run yet" in msg
+    # It names the model-side suspects only to RULE THEM OUT, and points at the producer.
+    assert "not the checkpoint, the LoRA or the sampler" in msg
+    assert "empty-latent node" in msg
+
+
+def test_nan_in_the_schedule_is_named_as_the_schedule(node):
+    with pytest.raises(RuntimeError) as e:
+        node._assert_finite_inputs(torch.zeros(1, 4), _sigmas(1.0, float("nan"), 0.0))
+    assert "sigma schedule contains NaN" in str(e.value)
+
+
+def test_an_interior_zero_sigma_is_caught_before_it_divides(node):
+    """Our solvers divide by sigma, so a 0 anywhere but the end is an instant Inf."""
+    with pytest.raises(RuntimeError) as e:
+        node._assert_finite_inputs(torch.zeros(1, 4), _sigmas(1.0, 0.0, 0.5, 0.0))
+    assert "before its last entry" in str(e.value)
+
+
+def test_a_trailing_zero_is_fine(node):
+    """The last sigma is only ever a target, never a divisor — the normal schedule shape."""
+    node._assert_finite_inputs(torch.zeros(1, 4), _sigmas(1.0, 0.6, 0.3, 0.0))
+
+
+def test_a_repeated_sigma_is_caught(node):
+    with pytest.raises(RuntimeError) as e:
+        node._assert_finite_inputs(torch.zeros(1, 4), _sigmas(1.0, 0.5, 0.5, 0.0))
+    assert "strictly descending" in str(e.value)
+
+
+def test_an_ascending_schedule_is_caught(node):
+    with pytest.raises(RuntimeError) as e:
+        node._assert_finite_inputs(torch.zeros(1, 4), _sigmas(0.3, 0.9, 0.0))
+    assert "strictly descending" in str(e.value)