fix(backends): darwin/metal support for supertonic (#10488)

The supertonic Go TTS backend dlopens ONNX Runtime, but its runtime and
packaging scripts were Linux-only: run.sh exported LD_LIBRARY_PATH, pointed
ONNXRUNTIME_LIB_PATH at libonnxruntime.so, and always tried the ld.so exec
path, while package.sh hard-failed on any non-Linux host. On macOS dyld has
no ld.so loader, uses DYLD_LIBRARY_PATH, and ONNX Runtime ships as a .dylib.

This applies the same purego .dylib/DYLD_LIBRARY_PATH fix that PR #10481
landed for 15 other ONNX/purego backends (sherpa-onnx, silero-vad, etc.) but
which omitted supertonic:

- run.sh: on darwin export DYLD_LIBRARY_PATH and point ONNXRUNTIME_LIB_PATH
  at libonnxruntime.dylib; guard the ld.so exec path to Linux only.
- package.sh: recognize Darwin instead of erroring out; the bundled .dylib is
  resolved via DYLD_LIBRARY_PATH, no glibc/ld.so to bundle.
- helper.go: platform-native default library extension (dylib on darwin) for
  the last-resort dlopen fallback.

It also wires the darwin CI build and gallery entries, resolving the
inconsistency where backend/index.yaml advertised metal for supertonic but no
includeDarwin matrix entry built the image:

- .github/backend-matrix.yml: add the -metal-darwin-arm64-supertonic Go entry.
- backend/index.yaml: declare metal capabilities and add the concrete
  metal-supertonic / metal-supertonic-development child entries.

The Makefile already detects Darwin/osx/arm64 and stages the per-OS ONNX
Runtime tarball, mirroring sherpa-onnx, so no Makefile change is required.


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

@@ -4974,13 +4974,6 @@ includeDarwin:
   - backend: "kitten-tts"
     tag-suffix: "-metal-darwin-arm64-kitten-tts"
     build-type: "mps"
-  # vLLM on Apple Silicon via vllm-metal (MLX). The install is custom
-  # (backend/python/vllm/install.sh has a darwin branch); lang stays python so
-  # backend_build_darwin.yml drives it through build-darwin-python-backend ->
-  # scripts/build/python-darwin.sh, which runs the backend's install.sh.
-  - backend: "vllm"
-    tag-suffix: "-metal-darwin-arm64-vllm"
-    build-type: "mps"
   - backend: "piper"
     tag-suffix: "-metal-darwin-arm64-piper"
     build-type: "metal"
@@ -4997,6 +4990,10 @@ includeDarwin:
     tag-suffix: "-metal-darwin-arm64-sherpa-onnx"
     build-type: "metal"
     lang: "go"
+  - backend: "supertonic"
+    tag-suffix: "-metal-darwin-arm64-supertonic"
+    build-type: "metal"
+    lang: "go"
   - backend: "local-store"
     tag-suffix: "-metal-darwin-arm64-local-store"
     build-type: "metal"

.github/bump_vllm_metal.sh

@@ -1,55 +0,0 @@
-#!/bin/bash
-# Bump the single vllm-metal pin (VLLM_METAL_VERSION) in the vLLM backend's
-# darwin (Apple Silicon) install path. The macOS/Metal build
-# (backend/python/vllm/install.sh, Darwin branch) installs vllm-metal, which is
-# version-locked to a specific vLLM source release. install.sh derives that vLLM
-# version at build time from vllm-metal's own installer (`vllm_v=`) at the pinned
-# tag, so there is only ONE value to bump here -- mirroring bump_vllm_wheel.sh,
-# which bumps the Linux cu130 wheel pin.
-#
-# This deliberately tracks vllm-project/vllm-metal, NOT vllm-project/vllm: the
-# darwin build can only use the exact vLLM version vllm-metal supports, so it may
-# lag the Linux pin (requirements-cublas13-after.txt) until vllm-metal catches up.
-set -xe
-REPO=$1   # vllm-project/vllm-metal
-FILE=$2   # backend/python/vllm/install.sh
-VAR=$3    # VLLM_METAL_VERSION (used for the workflow's output file names)
-
-if [ -z "$FILE" ] || [ -z "$REPO" ] || [ -z "$VAR" ]; then
-    echo "usage: $0 <repo> <install-file> <var-name>" >&2
-    exit 1
-fi
-
-# vllm-metal ships frequent dev releases, all flagged as non-prerelease, so
-# /releases/latest returns the newest one (with its cp312 wheel asset).
-LATEST_TAG=$(curl -sS -H "Accept: application/vnd.github+json" \
-    "https://api.github.com/repos/$REPO/releases/latest" \
-    | python3 -c "import json,sys; print(json.load(sys.stdin)['tag_name'])")
-
-# The coupled vLLM source version lives in vllm-metal's installer at that tag.
-NEW_VLLM_VERSION=$(curl -fsSL \
-    "https://raw.githubusercontent.com/$REPO/$LATEST_TAG/install.sh" \
-    | grep -oE 'vllm_v="[0-9]+\.[0-9]+\.[0-9]+"' | head -1 | cut -d'"' -f2)
-
-if [ -z "$LATEST_TAG" ] || [ -z "$NEW_VLLM_VERSION" ]; then
-    echo "Could not resolve vllm-metal tag ($LATEST_TAG) or its vllm_v ($NEW_VLLM_VERSION)." >&2
-    exit 1
-fi
-
-set +e
-CURRENT_TAG=$(grep -oE 'VLLM_METAL_VERSION="[^"]*"' "$FILE" | head -1 | cut -d'"' -f2)
-set -e
-
-# Rewrite the single pin. install.sh derives VLLM_VERSION from this tag at build
-# time, so there is nothing else to touch. peter-evans/create-pull-request opens
-# no PR on a clean tree, so a no-op rewrite (already current) is safe.
-sed -i "$FILE" \
-    -e "s|VLLM_METAL_VERSION=\"[^\"]*\"|VLLM_METAL_VERSION=\"$LATEST_TAG\"|"
-
-if [ -z "$CURRENT_TAG" ]; then
-    echo "Could not find VLLM_METAL_VERSION=\"...\" in $FILE." >&2
-    exit 0
-fi
-
-echo "vllm-metal ${CURRENT_TAG} -> ${LATEST_TAG} (builds vLLM ${NEW_VLLM_VERSION}): https://github.com/$REPO/releases/tag/${LATEST_TAG}" >> "${VAR}_message.txt"
-echo "${LATEST_TAG}" >> "${VAR}_commit.txt"

.github/workflows/bump_deps.yaml

@@ -154,39 +154,3 @@ jobs:
           branch: "update/VLLM_VERSION"
           body: ${{ steps.bump.outputs.message }}
           signoff: true
-
-  bump-vllm-metal:
-    # The darwin (Apple Silicon) vLLM build installs vllm-metal, which is locked
-    # to a specific vLLM source release. install.sh pins both VLLM_METAL_VERSION
-    # (the wheel release) and VLLM_VERSION (the vLLM it builds against); this job
-    # tracks vllm-project/vllm-metal and rewrites both atomically. Separate from
-    # bump-vllm-wheel because darwin follows vllm-metal, not vllm/vllm latest.
-    if: github.repository == 'mudler/LocalAI'
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v7
-      - name: Bump vllm-metal pin 🔧
-        id: bump
-        run: |
-          bash .github/bump_vllm_metal.sh vllm-project/vllm-metal backend/python/vllm/install.sh VLLM_METAL_VERSION
-          {
-            echo 'message<<EOF'
-            cat "VLLM_METAL_VERSION_message.txt"
-            echo EOF
-          } >> "$GITHUB_OUTPUT"
-          {
-            echo 'commit<<EOF'
-            cat "VLLM_METAL_VERSION_commit.txt"
-            echo EOF
-          } >> "$GITHUB_OUTPUT"
-          rm -rfv VLLM_METAL_VERSION_message.txt VLLM_METAL_VERSION_commit.txt
-      - name: Create Pull Request
-        uses: peter-evans/create-pull-request@v8
-        with:
-          token: ${{ secrets.UPDATE_BOT_TOKEN }}
-          push-to-fork: ci-forks/LocalAI
-          commit-message: ':arrow_up: Update vllm-project/vllm-metal (darwin)'
-          title: 'chore: :arrow_up: Update vllm-metal (darwin) to `${{ steps.bump.outputs.commit }}`'
-          branch: "update/VLLM_METAL_VERSION"
-          body: ${{ steps.bump.outputs.message }}
-          signoff: true

backend/go/supertonic/helper.go

@@ -16,6 +16,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strings"
 	"time"
 	"unicode"
@@ -943,7 +944,13 @@ func InitializeONNXRuntime() error {
 			}
 		}
 		if libPath == "" {
-			libPath = "/usr/local/lib/libonnxruntime.so"
+			// LocalAI: default to the platform-native shared library
+			// extension when nothing else is found (dyld vs ld.so).
+			if runtime.GOOS == "darwin" {
+				libPath = "/usr/local/lib/libonnxruntime.dylib"
+			} else {
+				libPath = "/usr/local/lib/libonnxruntime.so"
+			}
 		}
 	}
 	ort.SetSharedLibraryPath(libPath)

backend/go/supertonic/package.sh

@@ -32,6 +32,10 @@ elif [ -f "/lib/ld-linux-aarch64.so.1" ]; then
     cp -arfLv /lib/aarch64-linux-gnu/libdl.so.2 $CURDIR/package/lib/libdl.so.2
     cp -arfLv /lib/aarch64-linux-gnu/librt.so.1 $CURDIR/package/lib/librt.so.1
     cp -arfLv /lib/aarch64-linux-gnu/libpthread.so.0 $CURDIR/package/lib/libpthread.so.0
+elif [ $(uname -s) = "Darwin" ]; then
+    # macOS: dyld resolves the bundled .dylib via DYLD_LIBRARY_PATH (set in
+    # run.sh); there is no ld.so loader nor glibc to bundle.
+    echo "Detected Darwin"
 else
     echo "Error: Could not detect architecture"
     exit 1

backend/go/supertonic/run.sh

@@ -3,12 +3,19 @@ set -ex
 
 CURDIR=$(dirname "$(realpath $0)")
 
-export LD_LIBRARY_PATH=$CURDIR/lib:$LD_LIBRARY_PATH
-export ONNXRUNTIME_LIB_PATH=$CURDIR/lib/libonnxruntime.so
+if [ "$(uname)" = "Darwin" ]; then
+	# macOS uses dyld: there is no ld.so loader, and the search path env
+	# var is DYLD_LIBRARY_PATH. ONNX Runtime ships as a .dylib here.
+	export DYLD_LIBRARY_PATH=$CURDIR/lib:$DYLD_LIBRARY_PATH
+	export ONNXRUNTIME_LIB_PATH=$CURDIR/lib/libonnxruntime.dylib
+else
+	export LD_LIBRARY_PATH=$CURDIR/lib:$LD_LIBRARY_PATH
+	export ONNXRUNTIME_LIB_PATH=$CURDIR/lib/libonnxruntime.so
 
-if [ -f $CURDIR/lib/ld.so ]; then
-	echo "Using lib/ld.so"
-	exec $CURDIR/lib/ld.so $CURDIR/supertonic "$@"
+	if [ -f $CURDIR/lib/ld.so ]; then
+		echo "Using lib/ld.so"
+		exec $CURDIR/lib/ld.so $CURDIR/supertonic "$@"
+	fi
 fi
 
 exec $CURDIR/supertonic "$@"

backend/index.yaml

@@ -645,7 +645,6 @@
     nvidia-cuda-13: "cuda13-vllm"
     nvidia-l4t-cuda-13: "cuda13-nvidia-l4t-arm64-vllm"
     cpu: "cpu-vllm"
-    metal: "metal-vllm"
 - &sglang
   name: "sglang"
   license: apache-2.0
@@ -1570,6 +1569,7 @@
     - TTS
   capabilities:
     default: "cpu-supertonic"
+    metal: "metal-supertonic"
 - !!merge <<: *neutts
   name: "neutts-development"
   capabilities:
@@ -2928,17 +2928,6 @@
     nvidia-cuda-13: "cuda13-vllm-development"
     nvidia-l4t-cuda-13: "cuda13-nvidia-l4t-arm64-vllm-development"
     cpu: "cpu-vllm-development"
-    metal: "metal-vllm-development"
-- !!merge <<: *vllm
-  name: "metal-vllm"
-  uri: "quay.io/go-skynet/local-ai-backends:latest-metal-darwin-arm64-vllm"
-  mirrors:
-    - localai/localai-backends:latest-metal-darwin-arm64-vllm
-- !!merge <<: *vllm
-  name: "metal-vllm-development"
-  uri: "quay.io/go-skynet/local-ai-backends:master-metal-darwin-arm64-vllm"
-  mirrors:
-    - localai/localai-backends:master-metal-darwin-arm64-vllm
 - !!merge <<: *vllm
   name: "cuda12-vllm"
   uri: "quay.io/go-skynet/local-ai-backends:latest-gpu-nvidia-cuda-12-vllm"
@@ -5496,6 +5485,7 @@
   name: "supertonic-development"
   capabilities:
     default: "cpu-supertonic-development"
+    metal: "metal-supertonic-development"
 - !!merge <<: *supertonic
   name: "cpu-supertonic"
   uri: "quay.io/go-skynet/local-ai-backends:latest-cpu-supertonic"
@@ -5506,3 +5496,13 @@
   uri: "quay.io/go-skynet/local-ai-backends:master-cpu-supertonic"
   mirrors:
     - localai/localai-backends:master-cpu-supertonic
+- !!merge <<: *supertonic
+  name: "metal-supertonic"
+  uri: "quay.io/go-skynet/local-ai-backends:latest-metal-darwin-arm64-supertonic"
+  mirrors:
+    - localai/localai-backends:latest-metal-darwin-arm64-supertonic
+- !!merge <<: *supertonic
+  name: "metal-supertonic-development"
+  uri: "quay.io/go-skynet/local-ai-backends:master-metal-darwin-arm64-supertonic"
+  mirrors:
+    - localai/localai-backends:master-metal-darwin-arm64-supertonic

backend/python/vllm/install.sh

@@ -43,24 +43,6 @@ if [ "x${BUILD_PROFILE}" == "xcublas13" ]; then
     EXTRA_PIP_INSTALL_FLAGS+=" --index-strategy=unsafe-best-match"
 fi
 
-# Apple Silicon (Metal/MLX) via vllm-metal.
-# vllm-metal (github.com/vllm-project/vllm-metal) brings vLLM to macOS on Apple
-# Silicon: it registers through vLLM's platform-plugin entry point
-# (metal -> vllm_metal:register), MetalPlatform activates, and the vLLM v1
-# AsyncLLM engine runs on the GPU through MLX. LocalAI's backend.py is UNCHANGED
-# on darwin — AsyncEngineArgs(...) -> AsyncLLMEngine.from_engine_args transparently
-# resolves to the MLX engine (proven on a real M4 / macOS 26.5 against Qwen3-0.6B).
-#
-# vllm-metal REQUIRES Python 3.12, so force the portable CPython before the venv
-# is created (ensureVenv reads PYTHON_VERSION/PYTHON_PATCH/PY_STANDALONE_TAG).
-# The patch + standalone tag mirror the l4t13 cp312 pin — a known-good
-# python-build-standalone release that also ships an aarch64-apple-darwin asset.
-if [ "$(uname -s)" = "Darwin" ]; then
-    PYTHON_VERSION="3.12"
-    PYTHON_PATCH="12"
-    PY_STANDALONE_TAG="20251120"
-fi
-
 # JetPack 7 / L4T arm64 vllm + torch wheels come straight from PyPI now
 # (torch 2.11+ ships aarch64 + cu130 manylinux wheels and vllm 0.20+ ships
 # an aarch64 wheel pinned to that torch). They're cp312-only, so bump the
@@ -75,92 +57,11 @@ if [ "x${BUILD_PROFILE}" == "xl4t13" ]; then
     PY_STANDALONE_TAG="20251120"
 fi
 
-# ===================== Apple Silicon (Metal/MLX) =====================
-# Reproduce vllm-metal's upstream installer
-# (curl -fsSL https://raw.githubusercontent.com/vllm-project/vllm-metal/main/install.sh)
-# but INTO LocalAI's managed venv (ensureVenv) instead of a throwaway
-# ~/.venv-vllm-metal, so the backend integrates with LocalAI's venv lifecycle
-# (portable CPython, _makeVenvPortable relocation, runtime activation). The
-# normal CUDA/CPU installRequirements is skipped on darwin — there is no
-# macOS/arm64 vLLM wheel on PyPI; vLLM is built from source and the MLX engine
-# is layered on by the vllm-metal wheel.
-if [ "$(uname -s)" = "Darwin" ]; then
-    # Create/activate the portable 3.12 venv. On darwin USE_PIP=true and
-    # PORTABLE_PYTHON=true (set by scripts/build/python-darwin.sh), so this is a
-    # `python -m venv` based, relocatable venv.
-    ensureVenv
-
-    # vllm-metal's installer drives everything through `uv`: building vLLM from
-    # the CPU requirements needs `--index-strategy unsafe-best-match` (mixes the
-    # pytorch CPU channel with PyPI), a flag plain pip does not have. The darwin
-    # venv is pip-based, so bootstrap uv into it. uv honours $VIRTUAL_ENV (set by
-    # libbackend's _activateVenv) and installs into THIS venv — same pattern the
-    # intel branch below relies on.
-    pip install uv
-
-    # The ONLY darwin version pin -- AUTO-BUMPED by .github/bump_vllm_metal.sh,
-    # which tracks vllm-project/vllm-metal releases (NOT vllm/vllm latest). Keep
-    # it as a plain double-quoted assignment on its own line so the bumper's sed
-    # can rewrite it. Darwin therefore follows vllm-metal and can lag the Linux
-    # vllm pin (requirements-cublas13-after.txt, bumped independently against
-    # vllm/vllm) until vllm-metal supports a newer vLLM.
-    VLLM_METAL_VERSION="v0.3.0.dev20260622062346"
-
-    # The coupled vLLM source version is whatever this vllm-metal release builds
-    # against -- it declares it in its own installer as `vllm_v=`. Derive it from
-    # the PINNED tag rather than hardcoding a second value that could drift. The
-    # tag is immutable, so this stays reproducible across rebuilds.
-    VLLM_VERSION=$(curl -fsSL "https://raw.githubusercontent.com/vllm-project/vllm-metal/${VLLM_METAL_VERSION}/install.sh" \
-        | grep -oE 'vllm_v="[0-9]+\.[0-9]+\.[0-9]+"' | head -n1 | cut -d'"' -f2)
-    if [ -z "${VLLM_VERSION}" ]; then
-        echo "ERROR: could not derive the vLLM version from vllm-metal ${VLLM_METAL_VERSION}" >&2
-        exit 1
-    fi
-    echo "vllm-metal ${VLLM_METAL_VERSION} builds against vLLM ${VLLM_VERSION}"
-
-    _vllm_src=$(mktemp -d)
-    trap 'rm -rf "${_vllm_src}"' EXIT
-    pushd "${_vllm_src}"
-        # 1) Build vLLM ${VLLM_VERSION} from the release source tarball against
-        #    the CPU requirements. vllm-metal layers its MLX platform plugin on
-        #    top of this exact build.
-        curl -fsSL -o "vllm-${VLLM_VERSION}.tar.gz" \
-            "https://github.com/vllm-project/vllm/releases/download/v${VLLM_VERSION}/vllm-${VLLM_VERSION}.tar.gz"
-        tar -xzf "vllm-${VLLM_VERSION}.tar.gz"
-        pushd "vllm-${VLLM_VERSION}"
-            uv pip install -r requirements/cpu.txt --index-strategy unsafe-best-match
-            # -Wno-parentheses: clang on macOS treats one of vLLM's C++ warnings
-            # as an error without it (matches the upstream installer's CXXFLAGS).
-            CXXFLAGS="-Wno-parentheses" uv pip install .
-        popd
-    popd
-
-    # 2) Install the prebuilt vllm-metal wheel from the PINNED release
-    #    (${VLLM_METAL_VERSION}). It pulls mlx / mlx-metal as deps and registers
-    #    the `metal` platform plugin that backend.py resolves to at engine-init
-    #    time. Pinning the tag (vs releases/latest) keeps the wheel and the vLLM
-    #    source build above reproducible and coupled; .github/bump_vllm_metal.sh
-    #    advances both together.
-    _metal_wheel_url=$(curl -fsSL "https://api.github.com/repos/vllm-project/vllm-metal/releases/tags/${VLLM_METAL_VERSION}" \
-        | grep -oE '"browser_download_url"[[:space:]]*:[[:space:]]*"[^"]+\.whl"' \
-        | head -n1 | sed -E 's/.*"(https[^"]+)".*/\1/')
-    if [ -z "${_metal_wheel_url}" ]; then
-        echo "ERROR: could not resolve a vllm-metal wheel URL for release ${VLLM_METAL_VERSION}" >&2
-        exit 1
-    fi
-    echo "Installing vllm-metal wheel: ${_metal_wheel_url}"
-    uv pip install "${_metal_wheel_url}"
-
-    # Generate the gRPC stubs (backend_pb2*). installRequirements normally does
-    # this via runProtogen at the end; we skipped installRequirements on darwin,
-    # so call it explicitly here.
-    runProtogen
-
 # Intel XPU has no upstream-published vllm wheels, so we always build vllm
 # from source against torch-xpu and replace the default triton with
 # triton-xpu (matching torch 2.11). Mirrors the upstream procedure:
 # https://github.com/vllm-project/vllm/blob/main/docs/getting_started/installation/gpu.xpu.inc.md
-elif [ "x${BUILD_TYPE}" == "xintel" ]; then
+if [ "x${BUILD_TYPE}" == "xintel" ]; then
     # Hide requirements-intel-after.txt so installRequirements doesn't
     # try `pip install vllm` (would either fail or grab a non-XPU wheel).
     _intel_after="${backend_dir}/requirements-intel-after.txt"

backend/python/vllm/requirements-cublas13-after.txt

@@ -4,7 +4,4 @@
 # instead — the cublas13 case in install.sh adds --index-strategy=unsafe-best-match
 # so uv consults this index alongside PyPI.
 --extra-index-url https://wheels.vllm.ai/0.23.0/cu130
-# VERSION COUPLING: darwin/Apple-Silicon builds use vllm-metal (see install.sh),
-# which pins this exact vLLM version. Bumping vllm here means coordinating with a
-# vllm-metal release that supports the new version, or macOS/Metal builds break.
 vllm==0.23.0

core/http/endpoints/openai/realtime_model.go

@@ -432,7 +432,7 @@ func loadSoundDetectionConfig(pipeline *config.Pipeline, cl *config.ModelConfigL
 	if pipeline.SoundDetection == "" {
 		return nil, nil
 	}
-	cfg, err := cl.LoadModelConfigFileByName(pipeline.SoundDetection, ml.ModelPath)
+	cfg, err := loadPipelineSubModel(cl, pipeline.SoundDetection, ml.ModelPath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to load sound detection config: %w", err)
 	}
@@ -443,7 +443,7 @@ func loadSoundDetectionConfig(pipeline *config.Pipeline, cl *config.ModelConfigL
 }
 
 func newTranscriptionOnlyModel(pipeline *config.Pipeline, cl *config.ModelConfigLoader, ml *model.ModelLoader, appConfig *config.ApplicationConfig) (Model, *config.ModelConfig, error) {
-	cfgVAD, err := cl.LoadModelConfigFileByName(pipeline.VAD, ml.ModelPath)
+	cfgVAD, err := loadPipelineSubModel(cl, pipeline.VAD, ml.ModelPath)
 	if err != nil {
 
 		return nil, nil, fmt.Errorf("failed to load backend config: %w", err)
@@ -453,7 +453,7 @@ func newTranscriptionOnlyModel(pipeline *config.Pipeline, cl *config.ModelConfig
 		return nil, nil, fmt.Errorf("failed to validate config: %w", err)
 	}
 
-	cfgSST, err := cl.LoadModelConfigFileByName(pipeline.Transcription, ml.ModelPath)
+	cfgSST, err := loadPipelineSubModel(cl, pipeline.Transcription, ml.ModelPath)
 	if err != nil {
 
 		return nil, nil, fmt.Errorf("failed to load backend config: %w", err)
@@ -542,11 +542,30 @@ func buildRealtimeRoutingContext(a *application.Application, sessionID string) *
 	}
 }
 
+// loadPipelineSubModel loads a pipeline sub-model config by name and follows a
+// single alias hop, so a pipeline that references an alias (e.g. `llm: default`)
+// gets the alias target's full config (Backend, Model, ...) rather than the
+// alias stub with an empty Backend. Without this the alias survives unresolved
+// into model loading and fails downstream — notably in distributed mode with
+// "backend name is empty". Mirrors the top-level alias resolution in
+// core/http/middleware/request.go.
+func loadPipelineSubModel(cl *config.ModelConfigLoader, name, modelPath string) (*config.ModelConfig, error) {
+	cfg, err := cl.LoadModelConfigFileByName(name, modelPath)
+	if err != nil {
+		return nil, err
+	}
+	resolved, _, err := cl.ResolveAlias(cfg)
+	if err != nil {
+		return nil, err
+	}
+	return resolved, nil
+}
+
 // returns and loads either a wrapped model or a model that support audio-to-audio
 func newModel(pipeline *config.Pipeline, cl *config.ModelConfigLoader, ml *model.ModelLoader, appConfig *config.ApplicationConfig, evaluator *templates.Evaluator, routing *RealtimeRoutingContext) (Model, error) {
 	xlog.Debug("Creating new model pipeline model", "pipeline", pipeline)
 
-	cfgVAD, err := cl.LoadModelConfigFileByName(pipeline.VAD, ml.ModelPath)
+	cfgVAD, err := loadPipelineSubModel(cl, pipeline.VAD, ml.ModelPath)
 	if err != nil {
 
 		return nil, fmt.Errorf("failed to load backend config: %w", err)
@@ -557,7 +576,7 @@ func newModel(pipeline *config.Pipeline, cl *config.ModelConfigLoader, ml *model
 	}
 
 	// TODO: Do we always need a transcription model? It can be disabled. Note that any-to-any instruction following models don't transcribe as such, so if transcription is required it is a separate process
-	cfgSST, err := cl.LoadModelConfigFileByName(pipeline.Transcription, ml.ModelPath)
+	cfgSST, err := loadPipelineSubModel(cl, pipeline.Transcription, ml.ModelPath)
 	if err != nil {
 
 		return nil, fmt.Errorf("failed to load backend config: %w", err)
@@ -589,7 +608,7 @@ func newModel(pipeline *config.Pipeline, cl *config.ModelConfigLoader, ml *model
 	xlog.Debug("Loading a wrapped model")
 
 	// Otherwise we want to return a wrapped model, which is a "virtual" model that re-uses other models to perform operations
-	cfgLLM, err := cl.LoadModelConfigFileByName(pipeline.LLM, ml.ModelPath)
+	cfgLLM, err := loadPipelineSubModel(cl, pipeline.LLM, ml.ModelPath)
 	if err != nil {
 
 		return nil, fmt.Errorf("failed to load backend config: %w", err)
@@ -604,7 +623,7 @@ func newModel(pipeline *config.Pipeline, cl *config.ModelConfigLoader, ml *model
 	applyPipelineReasoning(cfgLLM, *pipeline)
 	applyPipelineThinking(cfgLLM, *pipeline)
 
-	cfgTTS, err := cl.LoadModelConfigFileByName(pipeline.TTS, ml.ModelPath)
+	cfgTTS, err := loadPipelineSubModel(cl, pipeline.TTS, ml.ModelPath)
 	if err != nil {
 
 		return nil, fmt.Errorf("failed to load backend config: %w", err)

core/http/endpoints/openai/realtime_model_alias_test.go

@@ -0,0 +1,52 @@
+package openai
+
+import (
+	"os"
+	"path/filepath"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	"github.com/mudler/LocalAI/core/config"
+)
+
+// loadPipelineSubModel must resolve a pipeline sub-model that references an
+// alias (e.g. `llm: default`) one hop to the alias target's full config — so
+// the effective backend is the target's backend, not the empty backend of the
+// alias stub. This mirrors the top-level alias resolution done in
+// core/http/middleware/request.go, which the realtime pipeline previously
+// skipped (failing in distributed mode with "backend name is empty").
+var _ = Describe("loadPipelineSubModel", func() {
+	It("resolves a sub-model alias one hop to the target's config", func() {
+		tmpDir := GinkgoT().TempDir()
+
+		// A real model config with a concrete backend.
+		realLLM := `name: real-llm
+backend: llama-cpp
+parameters:
+  model: real-llm.gguf
+`
+		Expect(os.WriteFile(filepath.Join(tmpDir, "real-llm.yaml"), []byte(realLLM), 0644)).To(Succeed())
+
+		// An alias pointing at the real model.
+		aliasCfg := `name: default
+alias: real-llm
+`
+		Expect(os.WriteFile(filepath.Join(tmpDir, "default.yaml"), []byte(aliasCfg), 0644)).To(Succeed())
+
+		cl := config.NewModelConfigLoader(tmpDir)
+		Expect(cl.LoadModelConfigsFromPath(tmpDir)).To(Succeed())
+
+		// Resolving the alias must follow the hop to the target's full config.
+		resolved, err := loadPipelineSubModel(cl, "default", tmpDir)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(resolved.IsAlias()).To(BeFalse())
+		Expect(resolved.Backend).To(Equal("llama-cpp"))
+
+		// A non-alias name must load unchanged.
+		direct, err := loadPipelineSubModel(cl, "real-llm", tmpDir)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(direct.Backend).To(Equal("llama-cpp"))
+		Expect(direct.Name).To(Equal("real-llm"))
+	})
+})