diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index bbfbf536..a6e4940e 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -32,6 +32,8 @@ jobs:
           profile: minimal
           toolchain: 1.81.0
           default: true
+      - name: Select Xcode 15.4
+        run: sudo xcode-select -s /Applications/Xcode_15.4.app
       - name: Build Automerge XCFramework and library
         if: steps.cache-automerge.outputs.cache-hit != 'true'
         run: ./scripts/build-xcframework.sh
@@ -46,11 +48,13 @@ jobs:
             libuniffi_automerge.a
             libuniffi_automerge_threads.a
 
-  test-automerge-swift:
+  mac:
     runs-on: macos-14
     needs: automerge-dependencies
     steps:
       - uses: actions/checkout@v4
+      - name: Select Xcode 15.4
+        run: sudo xcode-select -s /Applications/Xcode_15.4.app
       - name: Restore Automerge XCFramework and library
         uses: actions/cache/restore@v4
         with:
@@ -65,7 +69,7 @@ jobs:
       - name: Swift tests
         run: swift test
 
-  test-automerge-wasm:
+  wasm:
     runs-on: ubuntu-latest
     needs: automerge-dependencies
     strategy:
@@ -86,24 +90,24 @@ jobs:
             libuniffi_automerge.a
             libuniffi_automerge_threads.a
           key: automerge-dependencies-{{ hashFiles(AutomergeUniffi/automerge.swift) }}-{{ hashFiles(rust/Cargo.lock) }}
-      - name: Cache SDK for WebAssembly
-        id: cache-wasm-sdk
+      - name: Cache Toolchain for WebAssembly
+        id: cache-wasm-toolchain
         uses: actions/cache@v4
         with:
-          path: /tmp/swift-sdk.tar.gz
-          key: wasm-sdk-${{ matrix.checksum }}
-      - name: Download SDK for WebAssembly
+          path: /tmp/swift-toolchain.tar.gz
+          key: wasm-toolchain-${{ matrix.checksum }}
+      - name: Download Toolchain for WebAssembly
         if: steps.cache-wasm-sdk.outputs.cache-hit != 'true'
         run: |
           SWIFT_TOOLCHAIN_TAG="${{ matrix.toolchain }}"
           set -ex
-          curl -f -o /tmp/swift-sdk.tar.gz "https://download.swift.org/development/ubuntu2204/$SWIFT_TOOLCHAIN_TAG/$SWIFT_TOOLCHAIN_TAG-ubuntu22.04.tar.gz"
+          curl -f -o /tmp/swift-toolchain.tar.gz "https://download.swift.org/development/ubuntu2204/$SWIFT_TOOLCHAIN_TAG/$SWIFT_TOOLCHAIN_TAG-ubuntu22.04.tar.gz"
       - name: Install Swift and Swift SDK for WebAssembly
         run: |
           PREFIX=/opt/swift
           SWIFT_SDK_TAG="${{ matrix.swift-sdk }}"
           set -ex
-          sudo mkdir -p $PREFIX; sudo tar -xzf /tmp/swift-sdk.tar.gz -C $PREFIX --strip-component 1
+          sudo mkdir -p $PREFIX; sudo tar -xzf /tmp/swift-toolchain.tar.gz -C $PREFIX --strip-component 1
           $PREFIX/usr/bin/swift sdk install "https://github.com/swiftwasm/swift/releases/download/$SWIFT_SDK_TAG/$SWIFT_SDK_TAG-wasm32-unknown-wasi.artifactbundle.zip" --checksum ${{ matrix.checksum }}
           echo "$PREFIX/usr/bin" >> $GITHUB_PATH
       - name: Build tests