From e6957ec7ed34d30cfe91aa9f27575c665e79f9b3 Mon Sep 17 00:00:00 2001
From: Glary-Bot <glary-bot@users.noreply.github.com>
Date: Fri, 14 Aug 2026 23:36:15 +0000
Subject: [PATCH] Don't add noise to the alpha channel in the Add Noise to
 Image node

ImageAddNoise added gaussian noise across every channel, so RGBA input came
back with random transparency speckle. Noise belongs on the colour channels;
leave alpha alone.

CORE-392
---
 comfy_extras/nodes_images.py                  |  2 +
 .../image_add_noise_alpha_test.py             | 63 +++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 tests-unit/comfy_extras_test/image_add_noise_alpha_test.py

diff --git a/comfy_extras/nodes_images.py b/comfy_extras/nodes_images.py
index 7011d9c13..5c12ff926 100644
--- a/comfy_extras/nodes_images.py
+++ b/comfy_extras/nodes_images.py
@@ -189,6 +189,8 @@ class ImageAddNoise(IO.ComfyNode):
     def execute(cls, image, seed, strength) -> IO.NodeOutput:
         generator = torch.manual_seed(seed)
         s = torch.clip((image + strength * torch.randn(image.size(), generator=generator, device="cpu").to(image)), min=0.0, max=1.0)
+        if image.shape[-1] == 4:  # alpha stores transparency, not color
+            s[..., 3] = image[..., 3]
         return IO.NodeOutput(s)
 
     repeat = execute  # TODO: remove
diff --git a/tests-unit/comfy_extras_test/image_add_noise_alpha_test.py b/tests-unit/comfy_extras_test/image_add_noise_alpha_test.py
new file mode 100644
index 000000000..3f71e834c
--- /dev/null
+++ b/tests-unit/comfy_extras_test/image_add_noise_alpha_test.py
@@ -0,0 +1,63 @@
+import torch
+
+from comfy.cli_args import args as cli_args
+
+if not torch.cuda.is_available():
+    cli_args.cpu = True
+
+from comfy_extras.nodes_images import ImageAddNoise  # noqa: E402
+
+
+def image(channels, value=0.5, alpha=0.5, size=8):
+    t = torch.full((1, size, size, channels), value)
+    if channels == 4:
+        t[..., 3] = alpha
+    return t
+
+
+def test_rgb_gets_noise_on_every_channel():
+    src = image(3)
+
+    s = ImageAddNoise.execute(src, 0, 0.5).result[0]
+
+    assert s.shape == src.shape
+    assert not torch.equal(s, src)
+
+
+def test_rgba_keeps_alpha_untouched():
+    src = image(4)
+
+    s = ImageAddNoise.execute(src, 0, 0.5).result[0]
+
+    assert s.shape[-1] == 4
+    assert torch.equal(s[..., 3], src[..., 3])
+    assert not torch.equal(s[..., :3], src[..., :3])
+
+
+def test_fully_transparent_pixels_stay_transparent():
+    src = image(4, alpha=0.0)
+
+    s = ImageAddNoise.execute(src, 0, 1.0).result[0]
+
+    assert torch.all(s[..., 3] == 0.0)
+
+
+def test_only_the_alpha_channel_is_guarded():
+    """Colour channels must still get exactly the unguarded noise result."""
+    src = image(4)
+    generator = torch.manual_seed(0)
+    unguarded = torch.clip(src + 0.5 * torch.randn(src.size(), generator=generator), min=0.0, max=1.0)
+
+    s = ImageAddNoise.execute(src, 0, 0.5).result[0]
+
+    assert torch.equal(s[..., :3], unguarded[..., :3])
+    assert torch.equal(s[..., 3], src[..., 3])
+
+
+def test_does_not_mutate_input():
+    src = image(4)
+    before = src.clone()
+
+    ImageAddNoise.execute(src, 0, 0.5)
+
+    assert torch.equal(src, before)