bytecodealliance · cfallin · Sep 4, 2026 · Sep 23, 2026 · Sep 23, 2026 · Sep 23, 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: |
@@ -102,7 +104,15 @@ jobs:
         mkdir -p spidermonkey-dist-${{ matrix.build }}
         cp -a cmake-build-${{ matrix.build }}/spidermonkey-obj/dist/libspidermonkey.a spidermonkey-dist-${{ matrix.build }}/
         cp -aL cmake-build-${{ matrix.build }}/spidermonkey-obj/dist/include spidermonkey-dist-${{ matrix.build }}/
-        tree spidermonkey-dist-${{ matrix.build }}
+        if [ "${{ matrix.build }}" = "nightmonkey" ]; then
+          # The NightMonkey runtime is compiled against the engine's private
+          # headers and with the flags libjs was built with, which a
+          # --enable-external-compiler-hooks build exports alongside the
+          # public headers (see cmake/nightmonkey.cmake).
+          cp -aL cmake-build-${{ matrix.build }}/spidermonkey-obj/dist/include-private spidermonkey-dist-${{ matrix.build }}/
+          cp -aL cmake-build-${{ matrix.build }}/spidermonkey-obj/dist/system_wrappers spidermonkey-dist-${{ matrix.build }}/
+        fi
+        tree -L 2 spidermonkey-dist-${{ matrix.build }}
 
       # Upload tarball as an artifact of the github action run, so the output
       # can be inspected for pull requests.
@@ -153,13 +163,22 @@ 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 +190,52 @@ jobs:
           stability or availability guarantees.
         tag_name: ${{ needs.test.outputs.SM_TAG }}
         files: release-artifacts/*
+
+  # The NightMonkey compiler is a host binary that transforms a wizened
+  # snapshot of the (NightMonkey-enabled) runtime.
+  nightmonkey-compilers:
+    name: NightMonkey compiler (${{ matrix.artifact }})
+    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: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v4
+    - name: Read NightMonkey pins
+      id: nightmonkey
+      shell: bash
+      run: |
+        revision="$(awk '/^set\(NIGHTMONKEY_TAG / {gsub(/set\(NIGHTMONKEY_TAG |\)/, ""); print}' cmake/nightmonkey.cmake)"
+        engine="$(awk '/^set\(NIGHTMONKEY_ENGINE_VERSION / {gsub(/"/, "", $2); print $2}' cmake/nightmonkey.cmake)"
+        echo "revision=$revision" >> "$GITHUB_OUTPUT"
+        echo "engine=$engine" >> "$GITHUB_OUTPUT"
+    - uses: actions/checkout@v4
+      with:
+        repository: bytecodealliance/nightmonkey
+        ref: ${{ steps.nightmonkey.outputs.revision }}
+        path: nightmonkey
+    - name: Build compiler
+      shell: bash
+      run: |
+        cargo build --release -p nightmonkey --manifest-path nightmonkey/Cargo.toml \
+          --no-default-features --features "${{ steps.nightmonkey.outputs.engine }}"
+        compiler="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
@@ -82,6 +84,60 @@ jobs:
           tag_name: ${{ needs.release-please.outputs.tag_name }}
           files: release-artifacts/*
 
+  # The NightMonkey compiler for each supported host, built as in the CI
+  # workflow (see the nightmonkey-compilers job in main.yml) and uploaded next
+  # to the starling-raw-nightmonkey.wasm runtime it belongs to.
+  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: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Read NightMonkey pins
+        id: nightmonkey
+        shell: bash
+        run: |
+          revision="$(awk '/^set\(NIGHTMONKEY_TAG / {gsub(/set\(NIGHTMONKEY_TAG |\)/, ""); print}' cmake/nightmonkey.cmake)"
+          engine="$(awk '/^set\(NIGHTMONKEY_ENGINE_VERSION / {gsub(/"/, "", $2); print $2}' cmake/nightmonkey.cmake)"
+          echo "revision=$revision" >> "$GITHUB_OUTPUT"
+          echo "engine=$engine" >> "$GITHUB_OUTPUT"
+      - uses: actions/checkout@v4
+        with:
+          repository: bytecodealliance/nightmonkey
+          ref: ${{ steps.nightmonkey.outputs.revision }}
+          path: nightmonkey
+      - name: Build compiler
+        shell: bash
+        run: |
+          cargo build --release -p nightmonkey --manifest-path nightmonkey/Cargo.toml \
+            --no-default-features --features "${{ steps.nightmonkey.outputs.engine }}"
+          compiler="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
@@ -38,6 +38,7 @@ include("wasmtime")
 include("cbindgen")
 
 include("spidermonkey")
+include("nightmonkey")
 include("openssl")
 include("${HOST_API}/host_api.cmake")
 include("build-crates")
@@ -49,7 +50,7 @@ add_library(extension_api INTERFACE include/extension-api.h runtime/encode.h run
 if (ENABLE_JS_DEBUGGER)
     target_compile_definitions(extension_api INTERFACE ENABLE_JS_DEBUGGER)
 endif()
-target_link_libraries(extension_api INTERFACE rust-url spidermonkey)
+target_link_libraries(extension_api INTERFACE rust-url spidermonkey nightmonkey)
 target_include_directories(extension_api INTERFACE include deps/include runtime)
 
 include("builtins")
@@ -121,6 +122,12 @@ 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 "runtime/NightRegistration.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