bytecodealliance · cfallin · Sep 4, 2026
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -24,14 +24,15 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build: [release, debug, weval]
+        build: [release, debug, weval, nightmonkey]
         os: [ubuntu-latest]
     outputs:
       SM_TAG_EXISTS: ${{ steps.check-sm-release.outputs.SM_TAG_EXISTS }}
       SM_TAG: ${{ steps.check-sm-release.outputs.SM_TAG }}
       SM_CACHE_KEY_debug: ${{ steps.check-sm-release.outputs.SM_CACHE_KEY_debug }}
       SM_CACHE_KEY_release: ${{ steps.check-sm-release.outputs.SM_CACHE_KEY_release }}
       SM_CACHE_KEY_weval: ${{ steps.check-sm-release.outputs.SM_CACHE_KEY_weval }}
+      SM_CACHE_KEY_nightmonkey: ${{ steps.check-sm-release.outputs.SM_CACHE_KEY_nightmonkey }}
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
@@ -73,8 +74,9 @@ jobs:
     - name: Configure StarlingMonkey
       run: |
         cmake -S . -B cmake-build-${{ matrix.build }}\
-          -DCMAKE_BUILD_TYPE=${{ (matrix.build == 'release' || matrix.build == 'weval') && 'Release' || 'Debug' }}\
-          ${{matrix.build == 'weval' && '-DUSE_WASM_OPT=OFF -DWEVAL=ON' || ''}}
+          -DCMAKE_BUILD_TYPE=${{ (matrix.build == 'release' || matrix.build == 'weval' || matrix.build == 'nightmonkey') && 'Release' || 'Debug' }}\
+          ${{matrix.build == 'weval' && '-DUSE_WASM_OPT=OFF -DWEVAL=ON' || ''}}\
+          ${{matrix.build == 'nightmonkey' && '-DNIGHTMONKEY=ON' || ''}}
 
     - name: Build StarlingMonkey
       run: |
@@ -153,13 +155,22 @@ jobs:
           spidermonkey-dist-weval
         key: ${{ needs.test.outputs.SM_CACHE_KEY_weval }}
         fail-on-cache-miss: true
+    - name: Restore SpiderMonkey NightMonkey Cache
+      uses: actions/cache/restore@v4
+      id: sm-cache-nightmonkey
+      with:
+        path: |
+          spidermonkey-dist-nightmonkey
+        key: ${{ needs.test.outputs.SM_CACHE_KEY_nightmonkey }}
+        fail-on-cache-miss: true
 
     - name: Create SpiderMonkey Tar Balls
       run: |
         mkdir -p release-artifacts
         tar -a -cf release-artifacts/spidermonkey-static-debug.tar.gz spidermonkey-dist-debug/*
         tar -a -cf release-artifacts/spidermonkey-static-release.tar.gz spidermonkey-dist-release/*
         tar -a -cf release-artifacts/spidermonkey-static-release_weval.tar.gz spidermonkey-dist-weval/*
+        tar -a -cf release-artifacts/spidermonkey-static-release_nightmonkey.tar.gz spidermonkey-dist-nightmonkey/*
         tree release-artifacts
 
     - name: Do the Release
@@ -171,3 +182,47 @@ jobs:
           stability or availability guarantees.
         tag_name: ${{ needs.test.outputs.SM_TAG }}
         files: release-artifacts/*
+
+  nightmonkey-compilers:
+    name: NightMonkey compiler (${{ matrix.artifact }})
+    needs: test
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            artifact: nightmonkey-x86_64-linux
+            binary: nightmonkey
+          - os: ubuntu-24.04-arm
+            artifact: nightmonkey-aarch64-linux
+            binary: nightmonkey
+          - os: macos-14
+            artifact: nightmonkey-aarch64-macos
+            binary: nightmonkey
+          - os: windows-2022
+            artifact: nightmonkey-x86_64-windows.exe
+            binary: nightmonkey.exe
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v4
+    - name: Read Firefox revision
+      id: firefox-revision
+      shell: bash
+      run: |
+        revision="$(awk '/^set\(SM_TAG / {gsub(/set\(SM_TAG |\)/, ""); print}' cmake/spidermonkey.cmake)"
+        echo "revision=$revision" >> "$GITHUB_OUTPUT"
+    - uses: actions/checkout@v4
+      with:
+        repository: bytecodealliance/firefox
+        ref: ${{ steps.firefox-revision.outputs.revision }}
+        path: firefox
+    - name: Build compiler
+      run: |
+        cargo build --release --manifest-path firefox/js/src/night/nightmonkey/Cargo.toml
+        compiler="firefox/js/src/night/nightmonkey/target/release/${{ matrix.binary }}"
+        "$compiler" --help
+        cp "$compiler" "${{ matrix.artifact }}"
+    - uses: actions/upload-artifact@v4
+      with:
+        name: ${{ matrix.artifact }}
+        path: ${{ matrix.artifact }}
diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
@@ -55,6 +55,7 @@ jobs:
           just mode=release builddir=build-release build starling
           just mode=relwithdebinfo builddir=build-debug build starling
           just mode=weval builddir=build-weval build starling-ics.wevalcache
+          just mode=nightmonkey builddir=build-nightmonkey build starling
 
       - name: Prepare Artifacts
         run: |
@@ -64,6 +65,7 @@ jobs:
           cp build-release/starling-raw.wasm release-artifacts/starling-raw.wasm
           cp build-debug/starling-raw.wasm release-artifacts/starling-raw-debug.wasm
           cp build-weval/starling-raw.wasm release-artifacts/starling-raw-weval.wasm
+          cp build-nightmonkey/starling-raw.wasm release-artifacts/starling-raw-nightmonkey.wasm
 
           # Component-versions of the runtime
           cp build-release/starling.wasm release-artifacts/starling.wasm
@@ -72,6 +74,7 @@ jobs:
           # Supporting artifacts
           cp build-release/preview1-adapter.wasm release-artifacts
           cp build-weval/starling-ics.wevalcache release-artifacts
+          cp build-nightmonkey/componentize.sh release-artifacts
 
           echo "Release artifacts:"
           ls -la release-artifacts/
@@ -82,6 +85,53 @@ jobs:
           tag_name: ${{ needs.release-please.outputs.tag_name }}
           files: release-artifacts/*
 
+  build-nightmonkey-compilers:
+    needs: release-please
+    if: ${{ needs.release-please.outputs.release_created }}
+    permissions:
+      contents: write
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            artifact: nightmonkey-x86_64-linux
+            binary: nightmonkey
+          - os: ubuntu-24.04-arm
+            artifact: nightmonkey-aarch64-linux
+            binary: nightmonkey
+          - os: macos-14
+            artifact: nightmonkey-aarch64-macos
+            binary: nightmonkey
+          - os: windows-2022
+            artifact: nightmonkey-x86_64-windows.exe
+            binary: nightmonkey.exe
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Read Firefox revision
+        id: firefox-revision
+        shell: bash
+        run: |
+          revision="$(awk '/^set\(SM_TAG / {gsub(/set\(SM_TAG |\)/, ""); print}' cmake/spidermonkey.cmake)"
+          echo "revision=$revision" >> "$GITHUB_OUTPUT"
+      - uses: actions/checkout@v4
+        with:
+          repository: bytecodealliance/firefox
+          ref: ${{ steps.firefox-revision.outputs.revision }}
+          path: firefox
+      - name: Build compiler
+        run: |
+          cargo build --release --manifest-path firefox/js/src/night/nightmonkey/Cargo.toml
+          compiler="firefox/js/src/night/nightmonkey/target/release/${{ matrix.binary }}"
+          "$compiler" --help
+          cp "$compiler" "${{ matrix.artifact }}"
+      - name: Upload Release Asset
+        uses: softprops/action-gh-release@72f2c25fcb47643c292f7107632f7a47c1df5cd8 #2.3.2
+        with:
+          tag_name: ${{ needs.release-please.outputs.tag_name }}
+          files: ${{ matrix.artifact }}
+
   publish-extension:
     needs: release-please
     if: ${{ needs.release-please.outputs.debugger_release_created }}

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -121,6 +121,12 @@ else()
     set(AOT 0)
 endif()
 
+if(NIGHTMONKEY)
+    set(NIGHTMONKEY_AOT 1)
+else()
+    set(NIGHTMONKEY_AOT 0)
+endif()
+
 set(RUNTIME_FILE "starling-raw.wasm")
 set(ADAPTER_FILE "preview1-adapter.wasm")
 configure_file("componentize.sh.in" "${CMAKE_CURRENT_BINARY_DIR}/componentize.sh" @ONLY)

diff --git a/builtins/web/fetch/fetch_event.cpp b/builtins/web/fetch/fetch_event.cpp
@@ -12,6 +12,9 @@
 #include <allocator.h>
 #include <debugger.h>
 #include <js/SourceText.h>
+#ifdef ENABLE_JS_NIGHTMONKEY
+#  include <js/NightMonkey.h>
+#endif
 
 #include <iostream>
 #include <memory>
@@ -493,6 +496,11 @@ static void dispatch_fetch_event(HandleObject event, double *total_compute) {
 }
 
 bool handle_incoming_request(host_api::HttpIncomingRequest *request) {
+#ifdef ENABLE_JS_NIGHTMONKEY
+  if (!JS::NightActivate(ENGINE->cx())) {
+    return false;
+  }
+#endif
 #ifdef DEBUG
   std::println(stderr, "Warning: Using a DEBUG build. Expect things to be SLOW.");
 #endif

diff --git a/cmake/spidermonkey.cmake b/cmake/spidermonkey.cmake
@@ -1,4 +1,5 @@
-set(SM_TAG FIREFOX_147_0_4_RELEASE_STARLING)
+set(SM_TAG 9f1a4ce9a631039e6898985d842afaf16cebc89e)
+set(SM_REPO_URL https://github.com/bytecodealliance/firefox.git)
 
 include("manage-git-source")
 
@@ -9,9 +10,16 @@ else()
 endif()
 
 option(WEVAL "Build with a SpiderMonkey variant that supports weval-based AOT compilation" OFF)
+option(NIGHTMONKEY "Build with NightMonkey AOT compilation support" OFF)
+
+if (WEVAL AND NIGHTMONKEY)
+    message(FATAL_ERROR "WEVAL and NIGHTMONKEY cannot be enabled together")
+endif()
 
 if (WEVAL)
     set(SM_BUILD_TYPE "${SM_BUILD_TYPE}_weval")
+elseif (NIGHTMONKEY)
+    set(SM_BUILD_TYPE "${SM_BUILD_TYPE}_nightmonkey")
 endif()
 
 # If the developer has specified an alternate local set of SpiderMonkey
@@ -53,16 +61,20 @@ if (DEFINED SM_LIB_DIR)
     target_include_directories(spidermonkey INTERFACE ${SM_INCLUDE_DIR})
     target_link_libraries(spidermonkey INTERFACE ${SM_LIB_DIR}/libspidermonkey.a)
 else()
-    # Clone SpiderMonkey source using git directly for shallow clone
-    # Use deps folder in project root for shared access across build directories
-    set(SM_SOURCE_DIR ${CMAKE_SOURCE_DIR}/deps/spidermonkey-source)
-
-    manage_git_source(
-        NAME spidermonkey
-        REPO_URL https://github.com/bytecodealliance/firefox.git
-        TAG ${SM_TAG}
-        SOURCE_DIR ${SM_SOURCE_DIR}
-    )
+    set(SM_SOURCE_DIR "${CMAKE_SOURCE_DIR}/deps/spidermonkey-source" CACHE PATH
+        "Path to a local Firefox source checkout")
+    if (SM_SOURCE_DIR STREQUAL "${CMAKE_SOURCE_DIR}/deps/spidermonkey-source")
+        manage_git_source(
+            NAME spidermonkey
+            REPO_URL ${SM_REPO_URL}
+            TAG ${SM_TAG}
+            SOURCE_DIR ${SM_SOURCE_DIR}
+        )
+    elseif (NOT EXISTS "${SM_SOURCE_DIR}/mach")
+        message(FATAL_ERROR "SM_SOURCE_DIR does not contain a Firefox checkout: ${SM_SOURCE_DIR}")
+    else()
+        message(STATUS "Using SpiderMonkey source from ${SM_SOURCE_DIR}")
+    endif()
 
     # Each build configuration gets its own object directory
     set(SM_OBJ_DIR ${CMAKE_CURRENT_BINARY_DIR}/spidermonkey-obj)
@@ -151,6 +163,8 @@ mk_add_options AUTOCLOBBER=1
         string(APPEND MOZCONFIG_CONTENT "ac_add_options --enable-aot-ics\n")
         string(APPEND MOZCONFIG_CONTENT "ac_add_options --enable-aot-ics-force\n")
         string(APPEND MOZCONFIG_CONTENT "ac_add_options --enable-pbl-weval\n")
+    elseif(NIGHTMONKEY)
+        string(APPEND MOZCONFIG_CONTENT "ac_add_options --enable-nightmonkey\n")
     endif()
 
     file(GENERATE OUTPUT ${MOZCONFIG} CONTENT "${MOZCONFIG_CONTENT}")
@@ -188,6 +202,11 @@ mk_add_options AUTOCLOBBER=1
     )
     add_custom_target(spidermonkey_build DEPENDS ${LIB_SM})
 
+    if(NIGHTMONKEY)
+        set(NIGHTMONKEY_BIN "${SM_OBJ_DIR}/dist/host/bin/nightmonkey" CACHE FILEPATH
+            "Path to the NightMonkey compiler" FORCE)
+    endif()
+
     add_library(spidermonkey INTERFACE)
     add_dependencies(spidermonkey spidermonkey_build)
     target_include_directories(spidermonkey INTERFACE ${SM_INCLUDE_DIR})