diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7f1af8f..b99681f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,42 +12,90 @@ defaults:
 jobs:
   build_engine:
     name: Build Engine
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        build_type: [debug, release]
+    env:
+      WASI_SDK_VERSION: 25
+      BUILD_TYPE: ${{ matrix.build_type }}
     steps:
     - uses: actions/checkout@v2
       with:
         submodules: true
 
     - name: Cache SpiderMonkey tarball
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       id: sm-cache
       with:
         path: |
           dist
-        key: cache-${{ hashFiles('build-engine.sh') }}-${{ hashFiles('gecko-revision') }}-${{ hashFiles('object-files.list') }}
+        key: cache-${{ matrix.build_type }}-${{ hashFiles('build-engine.sh') }}-${{ hashFiles('gecko-revision') }}-${{ hashFiles('object-files.list') }}
 
-    - name: "Build and bundle SpiderMonkey"
+    - name: Install dependencies
+      id: deps
       if: steps.sm-cache.outputs.cache-hit != 'true'
       run: |
-        mkdir dist
+        mkdir -p dist
         sudo apt-get update -y
+        
+        if ! command -v rustup &> /dev/null; then
+          echo "Rustup not found, installing..."
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+          source $HOME/.cargo/env
+        fi
+        rustup target add wasm32-wasip1
+        
+        cargo install cbindgen
+        
+        # Download wasi-sdk
+        sdk_dir_name="wasi-sdk-${WASI_SDK_VERSION}.0-$(uname -m)-linux"
+        sdk_url=https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-${WASI_SDK_VERSION}/${sdk_dir_name}.tar.gz
+        curl --location --output wasi-sdk.tar.gz "${sdk_url}"
+        tar -xf wasi-sdk.tar.gz
 
-        bash ./build-engine.sh release
-        tar -a -cf dist/spidermonkey-wasm-static-lib_release.tar.gz release
-        rm -rf release obj-release
+    - name: Clone Gecko
+      id: clone-gecko
+      if: steps.sm-cache.outputs.cache-hit != 'true'
+      run: |
+        fetch_commits=
+        if [[ ! -a gecko-dev ]]; then
+        
+        # Clone Gecko repository at the required revision
+        mkdir gecko-dev
+        
+        git -C gecko-dev init
+        git -C gecko-dev remote add --no-tags \
+        origin "$(cat "gecko-repository")"
+        
+        fetch_commits=1
+        fi
+    
+        target_rev="$(cat "gecko-revision")"
+        if [[ -n "$fetch_commits" ]] || \
+        [[ "$(git -C gecko-dev rev-parse HEAD)" != "$target_rev" ]]; then
+        git -C gecko-dev fetch --depth 1 origin "$target_rev"
+        # Shallow fetching doesn't fetch tags, so we need to check if the target revision
+        # is a tag name and if so, create a local tag for it.
+        if ! git rev-parse --verify --quiet "$target_rev" > /dev/null; then
+          git tag "$target_rev" FETCH_HEAD
+        fi
+        git -C gecko-dev checkout FETCH_HEAD
+        fi
 
-        bash ./build-engine.sh release weval
-        tar -a -cf dist/spidermonkey-wasm-static-lib_release_weval.tar.gz release-weval
-        rm -rf release-weval obj-release-weval
+    - name: "Build and bundle SpiderMonkey"
+      id: build
+      if: steps.sm-cache.outputs.cache-hit != 'true'
+      run: |
+        export WASI_SDK_PATH=$(pwd)/wasi-sdk-${WASI_SDK_VERSION}.0-$(uname -m)-linux
 
-        bash ./build-engine.sh debug
-        tar -a -cf dist/spidermonkey-wasm-static-lib_debug.tar.gz debug
-        rm -rf debug obj-debug
+        bash ./build-engine.sh $BUILD_TYPE
+        tar -a -cf dist/spidermonkey-wasm-static-lib_${BUILD_TYPE}.tar.gz $BUILD_TYPE
 
     - name: Calculate tag name
       run: |
-        name=rev_$GITHUB_SHA
-        echo ::set-output name=val::$name
+        name=rev_$(cat gecko-revision)
+        echo val=$name >> $GITHUB_OUTPUT
         echo TAG=$name >> $GITHUB_ENV
       id: tagname
 
@@ -57,8 +105,8 @@ jobs:
       uses: actions/upload-artifact@v4
       if: github.event_name != 'push' || (github.ref != 'refs/heads/main' && !startsWith(github.ref, 'refs/tags/v'))
       with:
-        name: spidermonkey-wasm-static-lib.zip
-        path: dist/
+        name: spidermonkey-wasm-static-lib-${{ matrix.build_type }}.tar.gz
+        path: dist/spidermonkey-wasm-static-lib_${{ matrix.build_type }}.tar.gz
 
     # ... and if this was an actual push (tag or `main`) then we publish a
     # new release. This'll automatically publish a tag release or update `dev`
diff --git a/build-engine.sh b/build-engine.sh
index 1ab0083..f0799dc 100755
--- a/build-engine.sh
+++ b/build-engine.sh
@@ -3,22 +3,55 @@
 set -euo pipefail
 set -x
 
+# If WASI_SDK_PATH is set, use it to set up the compiler environment.
+if [[ -n "${WASI_SDK_PATH:-}" ]]; then
+  export CC="${WASI_SDK_PATH}/bin/clang"
+  export CXX="${WASI_SDK_PATH}/bin/clang++"
+  if [[ -z "${HOST_CC:-}" ]]; then
+    export HOST_CC=$(which clang)
+  fi
+  if [[ -z "${HOST_CXX:-}" ]]; then
+    export HOST_CXX=$(which clang++)
+  fi
+else
+  # Otherwise, check that all required environment variables are set.
+  if [[ -z "${WASI_SYSROOT:-}" ]]; then
+      echo "Error: WASI_SYSROOT environment variable is not set."
+      exit 1
+  fi
+  if [[ -z "${CC:-}" ]]; then
+      echo "Error: CC environment variable must be set to a clang that can target wasm32-wasip1."
+      exit 1
+  fi
+  if [[ -z "${CXX:-}" ]]; then
+      echo "Error: CXX environment variable must be set to a clang++ that can target wasm32-wasip1."
+      exit 1
+  fi
+  if [[ -z "${HOST_CC:-}" ]]; then
+      echo "Error: HOST_CC environment variable is not set."
+      exit 1
+  fi
+  if [[ -z "${HOST_CXX:-}" ]]; then
+      echo "Error: HOST_CXX environment variable is not set."
+      exit 1
+  fi
+fi
+
 working_dir="$(pwd)"
 script_dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
 
 mode="${1:-release}"
 weval=""
-if [[ $# > 1 ]] && [[ "$2" == "weval" ]]; then
+if [[ $# -gt 1 ]] && [[ "$2" == "weval" ]]; then
     weval=-weval
 fi
 mozconfig="${working_dir}/mozconfig-${mode}${weval}"
 objdir="obj-$mode${weval}"
 outdir="$mode${weval}"
-rebuild="${REBUILD_ENGINE:-0}"
 
 cat << EOF > "$mozconfig"
 ac_add_options --enable-project=js
-ac_add_options --enable-application=js
+ac_add_options --disable-js-shell # Prevents building Rust code, which we need to do ourselves anyway
 ac_add_options --target=wasm32-unknown-wasi
 ac_add_options --without-system-zlib
 ac_add_options --without-intl-api
@@ -36,14 +69,20 @@ mk_add_options MOZ_OBJDIR=${working_dir}/${objdir}
 mk_add_options AUTOCLOBBER=1
 EOF
 
+if [[ -n "${WASI_SYSROOT:-}" ]]; then
+    echo "ac_add_options --with-sysroot=\"${WASI_SYSROOT}\"" >> "$mozconfig"
+fi
+
 target="$(uname)"
 case "$target" in
   Linux)
     echo "ac_add_options --disable-stdcxx-compat" >> "$mozconfig"
+    platform="linux64-x64"
     ;;
 
   Darwin)
     echo "ac_add_options --host=aarch64-apple-darwin" >> "$mozconfig"
+    platform="macosx64-aarch64"
     ;;
 
   *)
@@ -76,59 +115,11 @@ case "$weval" in
     ;;
 esac
 
-# For a full build (not a rebuild), we need to clone the repo and do some setup work.
-# `rebuild.sh` invokes this script with REBUILD_ENGINE=1 which sets rebuild=1
-# and skips this setup.
-if [[ $rebuild == 0 ]]; then
-    # Ensure the Rust version matches that used by Gecko, and can compile to WASI
-    rustup target add wasm32-wasi
-
-    fetch_commits=
-    if [[ ! -a gecko-dev ]]; then
-
-      # Clone Gecko repository at the required revision
-      mkdir gecko-dev
-
-      git -C gecko-dev init
-      git -C gecko-dev remote add --no-tags -t wasi-embedding \
-        origin "$(cat "$script_dir/gecko-repository")"
-
-      fetch_commits=1
-    fi
-
-    target_rev="$(cat "$script_dir/gecko-revision")"
-    if [[ -n "$fetch_commits" ]] || \
-      [[ "$(git -C gecko-dev rev-parse HEAD)" != "$target_rev" ]]; then
-      git -C gecko-dev fetch --depth 1 origin "$target_rev"
-      git -C gecko-dev checkout FETCH_HEAD
-    fi
-
-    # Use Gecko's build system bootstrapping to ensure all dependencies are
-    # installed
-    cd gecko-dev
-    ./mach --no-interactive bootstrap --application-choice=js --no-system-changes
-
-    # ... except, that doesn't install the wasi-sysroot, which we need, so we do
-    # that manually.
-    cd ~/.mozbuild
-    python3 \
-      "${working_dir}/gecko-dev/mach" \
-      --no-interactive \
-      artifact \
-      toolchain \
-      --bootstrap \
-      --from-build \
-      sysroot-wasm32-wasi
-fi
-
 cd "$working_dir"
 
 # Build SpiderMonkey for WASI
 MOZCONFIG="${mozconfig}" \
 MOZ_FETCHES_DIR=~/.mozbuild \
-CC=~/.mozbuild/clang/bin/clang \
-CXX=~/.mozbuild/clang/bin/clang++ \
-AR=~/.mozbuild/clang/bin/llvm-ar \
   python3 "${working_dir}/gecko-dev/mach" \
   --no-interactive \
     build
@@ -139,9 +130,10 @@ mkdir -p "$outdir/lib"
 
 cd "$objdir"
 cp -Lr dist/include "../$outdir"
+cp js/src/js-confdefs.h "../$outdir/include/"
 
 while read -r file; do
   cp "$file" "../$outdir/lib"
 done < "$script_dir/object-files.list"
 
-cp js/src/build/libjs_static.a "wasm32-wasi/${mode}/libjsrust.a" "../$outdir/lib"
+cp js/src/build/libjs_static.a "../$outdir/lib"
diff --git a/gecko-repository b/gecko-repository
index 0994539..228c12d 100644
--- a/gecko-repository
+++ b/gecko-repository
@@ -1 +1 @@
-https://github.com/bytecodealliance/gecko-dev
\ No newline at end of file
+https://github.com/bytecodealliance/firefox
diff --git a/gecko-revision b/gecko-revision
index 559229f..5870cef 100644
--- a/gecko-revision
+++ b/gecko-revision
@@ -1 +1 @@
-7acfe5fcdb611518ecc36f5720cb784fdda1ad08
+tags/FIREFOX_140_0_4_RELEASE_STARLING
diff --git a/object-files.list b/object-files.list
index ca994c1..f5637ca 100644
--- a/object-files.list
+++ b/object-files.list
@@ -1,18 +1,22 @@
 memory/build/Unified_cpp_memory_build0.o
 memory/mozalloc/Unified_cpp_memory_mozalloc0.o
+mfbt/Unified_cpp_mfbt0.o
+mfbt/Unified_cpp_mfbt1.o
 mozglue/misc/AutoProfilerLabel.o
 mozglue/misc/ConditionVariable_noop.o
+mozglue/misc/Debug.o
+mozglue/misc/Decimal.o
 mozglue/misc/MmapFaultHandler.o
 mozglue/misc/Mutex_noop.o
+mozglue/misc/Now.o
 mozglue/misc/Printf.o
+mozglue/misc/SIMD.o
 mozglue/misc/StackWalk.o
 mozglue/misc/TimeStamp.o
 mozglue/misc/TimeStamp_posix.o
 mozglue/misc/Uptime.o
-mozglue/misc/Decimal.o
-mfbt/lz4.o
-mfbt/lz4frame.o
-mfbt/lz4hc.o
-mfbt/xxhash.o
-mfbt/Unified_cpp_mfbt0.o
-mfbt/Unified_cpp_mfbt1.o
+mozglue/static/lz4.o
+mozglue/static/lz4frame.o
+mozglue/static/lz4hc.o
+mozglue/static/xxhash.o
+third_party/fmt/Unified_cpp_third_party_fmt0.o
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index b9901d2..e7a439c 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,4 +1,4 @@
 [toolchain]
-channel = "1.77.1"
-targets = [ "wasm32-wasi" ]
+channel = "1.88.0"
+targets = [ "wasm32-wasip1" ]
 profile = "minimal"