fix(cookbook): allow local Windows Diffusers serving (#4077)

routes/shell_routes.py

@@ -1063,6 +1063,13 @@ def setup_shell_routes() -> APIRouter:
                 "category": "Image",
                 "target": "remote",
             },
+            {
+                "name": "transformers",
+                "pip": "transformers",
+                "desc": "Hugging Face model components used by SD/Flux pipelines and image tools",
+                "category": "Image",
+                "target": "remote",
+            },
             {
                 "name": "rembg",
                 "pip": "rembg[gpu]",
@@ -1257,6 +1264,7 @@ def setup_shell_routes() -> APIRouter:
             "sglang[all]",
             "diffusers",
             "diffusers[torch]",
+            "transformers",
             "TTS",
             "bark",
             "faster-whisper",

static/js/cookbook.js

@@ -597,7 +597,8 @@ export function _buildServeCmd(f, modelName, backend) {
   } else if (backend === 'diffusers') {
     const gpuStr = f.gpus?.trim();
     if (gpuStr) cmd += `CUDA_VISIBLE_DEVICES=${gpuStr} `;
-    cmd += `python3 scripts/diffusion_server.py --model ${modelName} --port ${f.port || '8100'}`;
+    const diffusersPy = _isWindows() ? 'python' : _py3Bin;
+    cmd += `${diffusersPy} scripts/diffusion_server.py --model ${modelName} --port ${f.port || '8100'}`;
     if (f.diff_dtype && f.diff_dtype !== 'bfloat16') cmd += ` --dtype ${f.diff_dtype}`;
     if (f.diff_device_map && f.diff_device_map !== 'balanced') cmd += ` --device-map ${f.diff_device_map}`;
     if (f.diff_steps) cmd += ` --steps ${f.diff_steps}`;
@@ -718,7 +719,7 @@ async function _fetchDependencies() {
     const data = await resp.json();
     const pkgs = data.packages || [];
     if (!pkgs.length) { list.innerHTML = '<div class="hwfit-loading">No packages found</div>'; return; }
-    const _winUnsupported = new Set(['diffusers', 'hf_transfer', 'vllm', 'rembg', 'gfpgan']);
+    const _winUnsupported = new Set(['hf_transfer', 'vllm', 'rembg', 'gfpgan']);
 
     const _statusTag = (pkg, isLocal, isSystemDep, winBlocked) => {
       if (winBlocked) return `<span class="cookbook-dep-tag cookbook-dep-na">N/A</span>`;

static/js/cookbookServe.js

@@ -530,7 +530,7 @@ function _rerenderCachedModels() {
         : (_lastUsed || (_isLegacyFlat ? _allSs : {}));
       const detectedBackend = _detectBackend(m).backend;
       const _allowedBackends = new Set(_isWindows()
-        ? ['llamacpp']
+        ? ['llamacpp', 'diffusers']
         : (_isMetal() ? ['llamacpp', 'ollama'] : ['vllm', 'sglang', 'llamacpp', 'ollama', 'diffusers']));
       const defaultBackend = (ss._forceBackend && ss.backend && _allowedBackends.has(ss.backend))
         ? ss.backend
@@ -590,7 +590,7 @@ function _rerenderCachedModels() {
       // Row 1: Backend + Server + Env
       panelHtml += `<div class="hwfit-serve-row">`;
       const _backendChoices = _isWindows()
-        ? [['llamacpp','llama.cpp']]
+        ? [['llamacpp','llama.cpp'],['diffusers','Diffusers']]
         : _isMetal()
         // Diffusers (diffusion_server.py) is CUDA-only — omit it on Metal.
         ? [['llamacpp','llama.cpp'],['ollama','Ollama']]

tests/test_cookbook_cpu_only_serve.py

@@ -15,6 +15,7 @@ import re
 from pathlib import Path
 
 SRC = Path(__file__).resolve().parent.parent / "static/js/cookbook.js"
+SERVE_SRC = Path(__file__).resolve().parent.parent / "static/js/cookbookServe.js"
 
 
 def test_cpu_only_drops_gpu_only_flags():
@@ -28,3 +29,25 @@ def test_cpu_only_drops_gpu_only_flags():
     # The CUDA unified-memory env must be suppressed for CPU-only too.
     assert "f.unified_mem && !_cpuOnly" in text, \
         "GGML_CUDA_ENABLE_UNIFIED_MEMORY must be gated on !_cpuOnly"
+
+
+def test_diffusers_is_not_blocked_on_windows_dependencies_panel():
+    text = SRC.read_text(encoding="utf-8")
+
+    assert "const _winUnsupported = new Set(['hf_transfer', 'vllm', 'rembg', 'gfpgan']);" in text
+    assert "new Set(['diffusers'" not in text
+
+
+def test_diffusers_is_available_on_windows_serve_panel():
+    text = SERVE_SRC.read_text(encoding="utf-8")
+
+    assert "? ['llamacpp', 'diffusers']" in text
+    assert "? [['llamacpp','llama.cpp'],['diffusers','Diffusers']]" in text
+
+
+def test_windows_diffusers_uses_python_not_python3():
+    text = SRC.read_text(encoding="utf-8")
+
+    assert "const diffusersPy = _isWindows() ? 'python' : _py3Bin;" in text
+    assert "cmd += `${diffusersPy} scripts/diffusion_server.py" in text
+    assert "cmd += `python3 scripts/diffusion_server.py" not in text

tests/test_cookbook_package_detection.py

@@ -23,6 +23,7 @@ def test_llama_cpp_maps_to_llama_cpp_python_distribution():
 
 def test_extras_and_version_markers_are_stripped():
     assert _pip_dist_name({"name": "diffusers", "pip": "diffusers[torch]"}) == "diffusers"
+    assert _pip_dist_name({"name": "transformers", "pip": "transformers"}) == "transformers"
     assert _pip_dist_name({"name": "sglang", "pip": "sglang[all]"}) == "sglang"
     assert _pip_dist_name({"name": "rembg", "pip": "rembg[gpu]"}) == "rembg"
     assert _pip_dist_name({"name": "x", "pip": "foo>=1.2,<2"}) == "foo"
@@ -48,3 +49,11 @@ def test_route_uses_dist_name_helper_not_munged_import_name():
     src = (Path(__file__).resolve().parents[1] / "routes" / "shell_routes.py").read_text(encoding="utf-8")
     assert "importlib_metadata.version(_pip_dist_name(pkg))" in src
     assert 'importlib_metadata.version(pkg["name"].replace("_", "-"))' not in src
+
+
+def test_transformers_is_listed_as_image_dependency():
+    src = (Path(__file__).resolve().parents[1] / "routes" / "shell_routes.py").read_text(encoding="utf-8")
+
+    assert '"name": "transformers"' in src
+    assert '"pip": "transformers"' in src
+    assert '"transformers",' in src