diff --git a/.github/workflows/ci-macos-compat.yml b/.github/workflows/ci-macos-compat.yml
index 463e5a56..a51a96c0 100644
--- a/.github/workflows/ci-macos-compat.yml
+++ b/.github/workflows/ci-macos-compat.yml
@@ -73,11 +73,17 @@ jobs:
       - name: Clean DerivedData
         run: rm -rf ~/Library/Developer/Xcode/DerivedData/GhosttyTabs-*
 
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .ci-source-packages
+          key: spm-${{ matrix.os }}-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-${{ matrix.os }}-
+
       - name: Resolve Swift packages
         run: |
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
-          rm -rf "$SOURCE_PACKAGES_DIR"
           mkdir -p "$SOURCE_PACKAGES_DIR"
 
           for attempt in 1 2 3; do
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c106a18a..6c1de0eb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -101,11 +101,17 @@ jobs:
           # Remove stale build cache to avoid incremental build errors
           rm -rf ~/Library/Developer/Xcode/DerivedData/GhosttyTabs-*
 
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .ci-source-packages
+          key: spm-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-
+
       - name: Resolve Swift packages
         run: |
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
-          rm -rf "$SOURCE_PACKAGES_DIR"
           mkdir -p "$SOURCE_PACKAGES_DIR"
 
           for attempt in 1 2 3; do
@@ -226,11 +232,17 @@ jobs:
       - name: Clean DerivedData
         run: rm -rf ~/Library/Developer/Xcode/DerivedData/GhosttyTabs-*
 
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .ci-source-packages
+          key: spm-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-
+
       - name: Resolve Swift packages
         run: |
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
-          rm -rf "$SOURCE_PACKAGES_DIR"
           mkdir -p "$SOURCE_PACKAGES_DIR"
 
           for attempt in 1 2 3; do
diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index da320e73..3b9a0866 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -142,13 +142,12 @@ jobs:
           rm GhosttyKit.xcframework.tar.gz
           test -d GhosttyKit.xcframework
 
-      - name: Configure SwiftPM cache
-        run: |
-          set -euo pipefail
-          CACHE_DIR="${RUNNER_TEMP}/swiftpm-cache/${GITHUB_RUN_ID}"
-          rm -rf "$CACHE_DIR"
-          mkdir -p "$CACHE_DIR"
-          echo "SWIFTPM_CACHE_PATH=$CACHE_DIR" >> "$GITHUB_ENV"
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .spm-cache
+          key: spm-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-
 
       - name: Derive Sparkle public key from private key
         env:
@@ -164,7 +163,9 @@ jobs:
 
       - name: Build app (Release)
         run: |
-          xcodebuild -scheme cmux -configuration Release -derivedDataPath build CODE_SIGNING_ALLOWED=NO ASSETCATALOG_COMPILER_APPICON_NAME=AppIcon-Nightly build
+          xcodebuild -scheme cmux -configuration Release -derivedDataPath build \
+            -clonedSourcePackagesDirPath .spm-cache \
+            CODE_SIGNING_ALLOWED=NO ASSETCATALOG_COMPILER_APPICON_NAME=AppIcon-Nightly build
 
       - name: Inject nightly identity and metadata
         run: |
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 57bfb154..200f003a 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -129,6 +129,14 @@ jobs:
           rm GhosttyKit.xcframework.tar.gz
           test -d GhosttyKit.xcframework
 
+      - name: Cache Swift packages
+        if: steps.guard_release_assets.outputs.skip_all != 'true'
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .spm-cache
+          key: spm-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-
+
       - name: Derive Sparkle public key from private key
         if: steps.guard_release_assets.outputs.skip_all != 'true'
         env:
@@ -145,7 +153,9 @@ jobs:
       - name: Build app (Release)
         if: steps.guard_release_assets.outputs.skip_all != 'true'
         run: |
-          xcodebuild -scheme cmux -configuration Release -derivedDataPath build CODE_SIGNING_ALLOWED=NO build
+          xcodebuild -scheme cmux -configuration Release -derivedDataPath build \
+            -clonedSourcePackagesDirPath .spm-cache \
+            CODE_SIGNING_ALLOWED=NO build
 
       - name: Inject Sparkle keys into Info.plist
         if: steps.guard_release_assets.outputs.skip_all != 'true'
diff --git a/.github/workflows/test-e2e.yml b/.github/workflows/test-e2e.yml
index 48b5e4de..23d595c7 100644
--- a/.github/workflows/test-e2e.yml
+++ b/.github/workflows/test-e2e.yml
@@ -151,11 +151,17 @@ jobs:
       - name: Clean DerivedData
         run: rm -rf ~/Library/Developer/Xcode/DerivedData/GhosttyTabs-*
 
+      - name: Cache Swift packages
+        uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4
+        with:
+          path: .ci-source-packages
+          key: spm-${{ inputs.runner || 'macos-15' }}-${{ hashFiles('GhosttyTabs.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved') }}
+          restore-keys: spm-${{ inputs.runner || 'macos-15' }}-
+
       - name: Resolve Swift packages
         run: |
           set -euo pipefail
           SOURCE_PACKAGES_DIR="$PWD/.ci-source-packages"
-          rm -rf "$SOURCE_PACKAGES_DIR"
           mkdir -p "$SOURCE_PACKAGES_DIR"
           for attempt in 1 2 3; do
             if xcodebuild -project GhosttyTabs.xcodeproj -scheme cmux-unit -configuration Debug \