From 38b00ff8e9d6e90ed25bbce68b79dba9dbfc7106 Mon Sep 17 00:00:00 2001
From: digital-garbage <133010426+digital-garbage@users.noreply.github.com>
Date: Fri, 4 Sep 2026 18:45:47 +0300
Subject: [PATCH] feat: record the attention backend in the run fingerprint

It is not an argument of the sampler node, but it decides whether two
runs can be identical at all: comfy_kitchen_int8 costs ~10% of the
picture between runs with everything else fixed (quantisation flips
buckets, which shows up as eyes and mouth changing while the motion
stays put), and pytorch is bit-exact. An A/B unknowingly spanning a
backend switch compares two different machines.

The override function carries its own name now, so the fingerprint can
report which backend was live rather than "something overrode it".
---
 loaders.py  |  5 +++++
 samplers.py | 11 +++++++++++
 2 files changed, 16 insertions(+)

diff --git a/loaders.py b/loaders.py
index 965c3c5f..d834a1c0 100644
--- a/loaders.py
+++ b/loaders.py
@@ -128,6 +128,11 @@ def attention_override(name):
     def override(_func, *args, **kwargs):
         return inner(*args, **kwargs)
 
+    # Named, so anything downstream can report WHICH backend is live. The attention backend
+    # decides whether generation is even reproducible (int8 quantisation flips buckets and
+    # costs ~10% of the picture between identical runs; pytorch is bit-exact), so an A/B that
+    # unknowingly spans a backend switch is comparing two different machines.
+    override.funpack_attention_name = str(name)
     return override
 
 
diff --git a/samplers.py b/samplers.py
index 032199e4..92397537 100644
--- a/samplers.py
+++ b/samplers.py
@@ -7279,6 +7279,17 @@ class FunPackLTXAVSceneChainSampler:
         # repeatability check that is really a prompt change reads as "generation is not
         # reproducible". Cheap stand-in: per-entry shape + mean + std, which differs between
         # any two real prompts and costs two reductions on an already-resident tensor.
+        # The attention backend is not an argument of this node, but it decides whether two
+        # runs can even be identical, so it belongs in the fingerprint next to the ones that
+        # are. Unknown when nothing overrode it (whatever ComfyUI was launched with).
+        try:
+            _att = (model.model_options.get("transformer_options", {})
+                    .get("optimized_attention_override"))
+            _run_settings["attention"] = str(getattr(_att, "funpack_attention_name",
+                                                     "default (as launched)" if _att is None
+                                                     else "override"))
+        except Exception:  # noqa: BLE001
+            pass
         # NUMBERS, not a formatted string: a string is only ever equal or not, so float wobble
         # in the encoder reads identically to the conditioning genuinely moving, and every row
         # says "prompt changed" with no way to tell which. The reader compares these with a