feat(backends): add darwin/metal build for liquid-audio (#10486)

* feat(backends): add darwin/metal build for liquid-audio

Wire the already-MPS-ready liquid-audio backend (it ships
requirements-mps.txt) into the darwin CI matrix and the gallery so
metal-darwin-arm64 images are built and selectable.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:opus-4.8 [Claude Code]

* ci(liquid-audio): trigger darwin build via requirements-mps note

The changed-backends path filter only builds a backend when a file under
its directory changes. The metal wiring lived in index.yaml + the matrix,
so the darwin job was skipped. Add a documenting comment to the MPS
requirements so CI actually exercises the darwin build.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:opus-4.8 [Claude Code]

* fix(liquid-audio): guard uv-only --index-strategy for the pip/darwin path

Same fix as trl: the darwin/MPS build installs with pip (USE_PIP=true), which
rejects the uv-only --index-strategy flag and failed the darwin backend build.
Add it only on the uv path; Linux/CUDA resolution is unchanged.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:opus-4.8 [Claude Code]

---------

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

.github/backend-matrix.yml

@@ -4974,6 +4974,9 @@ includeDarwin:
   - backend: "kitten-tts"
     tag-suffix: "-metal-darwin-arm64-kitten-tts"
     build-type: "mps"
+  - backend: "liquid-audio"
+    tag-suffix: "-metal-darwin-arm64-liquid-audio"
+    build-type: "mps"
   - backend: "piper"
     tag-suffix: "-metal-darwin-arm64-piper"
     build-type: "metal"

backend/index.yaml

@@ -1284,6 +1284,7 @@
     nvidia-cuda-13: "cuda13-liquid-audio"
     nvidia-cuda-12: "cuda12-liquid-audio"
     nvidia-l4t-cuda-13: "cuda13-nvidia-l4t-arm64-liquid-audio"
+    metal: "metal-liquid-audio"
   icon: https://cdn-avatars.huggingface.co/v1/production/uploads/61b8e2ba285851687028d395/7_6D7rWrLxp2hb6OHSV1p.png
 - &qwen-tts
   urls:
@@ -4613,6 +4614,7 @@
     nvidia-cuda-13: "cuda13-liquid-audio-development"
     nvidia-cuda-12: "cuda12-liquid-audio-development"
     nvidia-l4t-cuda-13: "cuda13-nvidia-l4t-arm64-liquid-audio-development"
+    metal: "metal-liquid-audio-development"
 - !!merge <<: *liquid-audio
   name: "cpu-liquid-audio"
   uri: "quay.io/go-skynet/local-ai-backends:latest-cpu-liquid-audio"
@@ -4623,6 +4625,16 @@
   uri: "quay.io/go-skynet/local-ai-backends:master-cpu-liquid-audio"
   mirrors:
     - localai/localai-backends:master-cpu-liquid-audio
+- !!merge <<: *liquid-audio
+  name: "metal-liquid-audio"
+  uri: "quay.io/go-skynet/local-ai-backends:latest-metal-darwin-arm64-liquid-audio"
+  mirrors:
+    - localai/localai-backends:latest-metal-darwin-arm64-liquid-audio
+- !!merge <<: *liquid-audio
+  name: "metal-liquid-audio-development"
+  uri: "quay.io/go-skynet/local-ai-backends:master-metal-darwin-arm64-liquid-audio"
+  mirrors:
+    - localai/localai-backends:master-metal-darwin-arm64-liquid-audio
 - !!merge <<: *liquid-audio
   name: "cuda12-liquid-audio"
   uri: "quay.io/go-skynet/local-ai-backends:latest-gpu-nvidia-cuda-12-liquid-audio"

backend/python/liquid-audio/install.sh

@@ -14,5 +14,11 @@ else
 fi
 
 # liquid-audio's torch wheels are large; allow upgrades to satisfy transitive pins
-EXTRA_PIP_INSTALL_FLAGS+=" --upgrade --index-strategy=unsafe-first-match"
+EXTRA_PIP_INSTALL_FLAGS+=" --upgrade"
+# --index-strategy is a uv-only flag. The darwin/MPS build installs with pip
+# (USE_PIP=true in scripts/build/python-darwin.sh), which rejects it. Only add
+# it on the uv path; Linux/CUDA resolution is unchanged.
+if [ "x${USE_PIP:-}" != "xtrue" ]; then
+    EXTRA_PIP_INSTALL_FLAGS+=" --index-strategy=unsafe-first-match"
+fi
 installRequirements

backend/python/liquid-audio/requirements-mps.txt

@@ -1,3 +1,4 @@
+# MPS (Apple Silicon / Metal) build profile - installed by the darwin CI job.
 torch>=2.8.0
 torchaudio>=2.8.0
 torchcodec>=0.9.1