diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index dd4eff2c7fb..7802efa17e9 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -136,12 +136,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
+            apt-get install -y ca-certificates
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential libsdl2-dev cmake git
             cmake -B build
             cmake --build build --config Release -j $(nproc)'
@@ -168,16 +186,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt-get update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
             apt-get install -y ca-certificates
-            sed -i "s|http://ports.ubuntu.com|https://mirror.kumi.systems|g" /etc/apt/sources.list
-
-            apt update
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential libsdl2-dev cmake git
             cmake -B build -DGGML_NATIVE=OFF -DGGML_CPU_ARM_ARCH=armv8-a
             cmake --build build --config Release -j $(nproc)'
@@ -204,16 +236,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt-get update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
             apt-get install -y ca-certificates
-            sed -i "s|http://ports.ubuntu.com|https://mirror.kumi.systems|g" /etc/apt/sources.list
-
-            apt update
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential libsdl2-dev cmake git
             cmake -B build -DGGML_NATIVE=OFF -DGGML_CPU_ARM_ARCH=armv7-a+fp
             cmake --build build --config Release -j $(nproc)'
@@ -332,16 +378,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt-get update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
             apt-get install -y ca-certificates
-            sed -i "s|http://ports.ubuntu.com|https://mirror.kumi.systems|g" /etc/apt/sources.list
-
-            apt update
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential cmake libsdl2-dev git
             cmake . -DWHISPER_SDL2=ON -DCMAKE_BUILD_TYPE=${{ matrix.build }} -DGGML_NATIVE=OFF -DGGML_CPU_ARM_ARCH=armv8-a
             make
@@ -370,16 +430,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt-get update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
             apt-get install -y ca-certificates
-            sed -i "s|http://ports.ubuntu.com|https://mirror.kumi.systems|g" /etc/apt/sources.list
-
-            apt update
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential cmake libsdl2-dev git
             cmake . -DWHISPER_SDL2=ON -DCMAKE_BUILD_TYPE=${{ matrix.build }} -DGGML_NATIVE=OFF -DGGML_CPU_ARM_ARCH=armv7-a+fp
             make
@@ -411,16 +485,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt-get update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
             apt-get install -y ca-certificates
-            sed -i "s|http://ports.ubuntu.com|https://mirror.kumi.systems|g" /etc/apt/sources.list
-
-            apt update
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y clang build-essential cmake libsdl2-dev git
             cmake . -DWHISPER_SDL2=ON -DCMAKE_BUILD_TYPE=${{ matrix.build }} -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang
             make
@@ -449,12 +537,30 @@ jobs:
           docker run --platform ${{ matrix.arch }} --rm \
             -v ${{ github.workspace }}:/workspace \
             -w /workspace ${{ env.ubuntu_image }} /bin/sh -c '
+            # Robust apt setup with mirror fallback
             set -e
             export DEBIAN_FRONTEND=noninteractive
-            sed -i "s|archive.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-            sed -i "s|security.ubuntu.com|mirrors.kernel.org|g" /etc/apt/sources.list
-
-            apt update
+            echo "Acquire::Retries \"3\";" > /etc/apt/apt.conf.d/80-retries
+            echo "Acquire::http::Timeout \"10\";" > /etc/apt/apt.conf.d/80-timeout
+            echo "Acquire::https::Timeout \"10\";" >> /etc/apt/apt.conf.d/80-timeout
+            for mirror in mirrors.kernel.org mirror.pit.teraswitch.com archive.ubuntu.com; do
+                echo "Trying mirror: $mirror"
+                sed -i "s|archive.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                sed -i "s|security.ubuntu.com|$mirror|g" /etc/apt/sources.list
+                if apt-get update; then echo "Using: $mirror"; break; else
+                    echo "Failed: $mirror"; sed -i "s|$mirror|archive.ubuntu.com|g" /etc/apt/sources.list; fi
+            done
+            apt-get install -y ca-certificates
+            if echo "${{ matrix.arch }}" | grep -q arm; then
+                for pm in mirrors.kernel.org mirror.pit.teraswitch.com ports.ubuntu.com; do
+                    url="http://$pm"; echo "Trying ports: $url"
+                    sed -i "s|http://ports.ubuntu.com|$url|g" /etc/apt/sources.list
+                    if apt-get update; then echo "Using ports: $url"; break; else
+                        sed -i "s|$url|http://ports.ubuntu.com|g" /etc/apt/sources.list; fi
+                done
+            fi
+
+            # Install packages and build
             apt install -y build-essential cmake git
             cmake . -DCMAKE_BUILD_TYPE=Debug \
               -DWHISPER_SANITIZE_${{ matrix.sanitizer }}=ON \