Release 0.12.0: traversal test fix, attention_backend pin fix

.env.example

@@ -102,7 +102,10 @@
 
 # The attention backend for every model that sets none (default native). A
 # workflow's per-component "attention_backend" overrides it. Same values as
-# that setting: native, flash_hub, sage_hub, _native_cudnn, ...
+# that setting: native, flash_hub, sage_hub, _native_cudnn, ... Leave it
+# native: it reaches every model on the server, and sage cannot serve all of
+# them (Music3's head_dim-256 decoder, LTX's attention mask). Pin sage_hub per
+# workflow instead - the MiniMax-H3 templates take attention_backend=sage_hub.
 # DIFFUSERS_ATTN_BACKEND=native
 
 # Refuse any pipeline or component that would load custom code from the Hub.

docs/ACCELERATION.md

@@ -160,6 +160,8 @@ A component can also pin its backend persistently instead, via `set_attention_ba
 
 Prefer the pinned form for a compiled component - the per-call context manager switches implementations under the compiled graph and forces a recompile on every run.
 
+Either form stays on what it names. diffusers' `set_attention_backend` also makes its backend the process-wide default, which the persistent worker would keep for every later model; dw restores the default after pinning, so an H3 `sage_hub` pin cannot reach a Music3 or LTX job that follows it. The server-wide default is `DIFFUSERS_ATTN_BACKEND` in `.env` - leave it `native`, since it reaches every model and sage cannot serve all of them.
+
 ## Attention Slicing
 
 ```json

docs/RELEASING.md

@@ -68,6 +68,12 @@ hallucinations as lyrics.
   so `triton` stays clearable after the first run (#837).
 - `deploy.sh` restarts a `dw.serve` run as a loaded launchd daemon on
   macOS.
+- A component's `attention_backend` pin stays on that component. diffusers
+  also made it the process-wide default, so after an H3 run with
+  `attention_backend=sage_hub` the worker sent every later model through
+  sage, and Music3 failed with `Unsupported head_dim: 256` (LTX's attention
+  mask is refused the same way). Music3 and LTX templates need no pin of
+  their own.
 
 ### 0.11.1
 

dw/pipeline_processors/components.py

@@ -129,7 +129,7 @@ def configure_components(pipeline, configuration, default_device, reused_compone
             logger.info(
                 f"Setting {component_name} attention backend: {component_attention_backend}"
             )
-            component.set_attention_backend(component_attention_backend)
+            set_component_attention_backend(component, component_attention_backend)
 
         # Compile last - the graph must capture final dtypes, adapters,
         # quantization, and offload hooks
@@ -143,6 +143,26 @@ def configure_components(pipeline, configuration, default_device, reused_compone
             )
 
 
+def set_component_attention_backend(component, backend):
+    """Pin one component's attention backend without changing anyone else's.
+
+    diffusers' set_attention_backend writes the backend onto the component's own
+    processors, then also makes it the process-wide active backend - the default
+    for every model that pins none. The persistent worker outlives the job, so an
+    H3 transformer pinned to sage_hub would route every later model through sage,
+    and models sage cannot serve (Music3's head_dim-256 audio decoder, LTX's
+    attention mask) crash. Restoring the active backend keeps the pin on the
+    component it was asked for; its processors pass their own backend explicitly.
+    """
+    from diffusers.models.attention_dispatch import _AttentionBackendRegistry
+
+    active_backend = _AttentionBackendRegistry._active_backend
+    try:
+        component.set_attention_backend(backend)
+    finally:
+        _AttentionBackendRegistry.set_active_backend(active_backend)
+
+
 def enable_tiling(component, component_name, component_configuration):
     """Turn on tiled decoding for a component whose configuration asks for it.
 

tests/test_disk_caches.py

@@ -344,6 +344,18 @@ def tree(root):
     return sorted(str(p.relative_to(root)) for p in root.rglob("*"))
 
 
+def parent_tree(tmp_path):
+    """What is under tmp_path, minus the server's own workspace files: the
+    job history's SQLite -shm/-wal sidecars come and go with its connection,
+    and outputs/ is created on the server's schedule, so a traversal test
+    checks the parent for losses among the rest, not for equality."""
+    return {
+        p
+        for p in tree(tmp_path)
+        if not p.startswith("jobs.sqlite") and not p.startswith("outputs")
+    }
+
+
 class TestCacheRoutes:
     def test_list_reports_both_caches(self, api, tmp_path):
         root, (total, count) = marked_root(tmp_path)
@@ -436,17 +448,14 @@ def test_traversal_name_touches_nothing(self, api, tmp_path, status):
         victim.parent.mkdir()
         victim.write_bytes(b"x" * 8)
         before_root = tree(root)
-        before_parent = tree(tmp_path)
+        before_parent = parent_tree(tmp_path)
 
         response = api.delete("/api/caches/..%2Fx")
 
         assert response.status_code == status
         assert tree(root) == before_root
         assert victim.read_bytes() == b"x" * 8
-        # The server's own workspace lives under tmp_path too (outputs, the
-        # job history's -shm/-wal), and it adds files there on its own
-        # schedule, so the parent is checked for losses, not for equality
-        assert set(before_parent) <= set(tree(tmp_path))
+        assert before_parent <= parent_tree(tmp_path)
 
 
 # ------------------------------------------------------- quantized entries

tests/test_modular_pipeline.py

@@ -679,6 +679,25 @@ def test_attention_backend_is_pinned_on_the_component(self):
 
         pipeline.transformer.set_attention_backend.assert_called_once_with("flash_hub")
 
+    def test_attention_backend_pin_leaves_the_process_default_alone(self):
+        # diffusers' set_attention_backend also sets the process-wide active
+        # backend, which the persistent worker keeps for every later model -
+        # an H3 sage_hub pin crashed Music3's head_dim-256 decoder that way
+        from diffusers.models.attention_dispatch import _AttentionBackendRegistry
+
+        def leaky_pin(backend):
+            _AttentionBackendRegistry.set_active_backend(backend)
+
+        pipeline = MagicMock()
+        pipeline.transformer.set_attention_backend.side_effect = leaky_pin
+        before = _AttentionBackendRegistry._active_backend
+        try:
+            self.configure({"transformer": {"attention_backend": "sage_hub"}}, pipeline)
+
+            assert _AttentionBackendRegistry._active_backend == before
+        finally:
+            _AttentionBackendRegistry.set_active_backend(before)
+
     def test_component_device_override_governs_the_mps_skip(self, caplog):
         # The step may pin this component to another device than the pipeline's
         pipeline = MagicMock()