diff --git a/.github/workflows/chained_e2e.yml b/.github/workflows/chained_e2e.yml
index 722559ec17..494163966e 100644
--- a/.github/workflows/chained_e2e.yml
+++ b/.github/workflows/chained_e2e.yml
@@ -168,6 +168,7 @@ jobs:
           GEMINI_API_KEY: '${{ secrets.GEMINI_API_KEY }}'
           KEEP_OUTPUT: 'true'
           VERBOSE: 'true'
+          BUILD_SANDBOX_FLAGS: '--cache-from type=gha --cache-to type=gha,mode=max'
         shell: 'bash'
         run: |
           if [[ "${{ matrix.sandbox }}" == "sandbox:docker" ]]; then
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fa8ce717f1..3fb1867db7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -50,6 +50,8 @@ jobs:
     runs-on: 'gemini-cli-ubuntu-16-core'
     needs: 'merge_queue_skipper'
     if: "${{needs.merge_queue_skipper.outputs.skip == 'false'}}"
+    env:
+      GEMINI_LINT_TEMP_DIR: '${{ github.workspace }}/.gemini-linters'
     steps:
       - name: 'Checkout'
         uses: 'actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8' # ratchet:actions/checkout@v5
@@ -63,9 +65,21 @@ jobs:
           node-version-file: '.nvmrc'
           cache: 'npm'
 
+      - name: 'Cache Linters'
+        uses: 'actions/cache@v4'
+        with:
+          path: '${{ env.GEMINI_LINT_TEMP_DIR }}'
+          key: "${{ runner.os }}-${{ runner.arch }}-linters-${{ hashFiles('scripts/lint.js') }}"
+
       - name: 'Install dependencies'
         run: 'npm ci'
 
+      - name: 'Cache ESLint'
+        uses: 'actions/cache@v4'
+        with:
+          path: '.eslintcache'
+          key: "${{ runner.os }}-eslint-${{ hashFiles('package-lock.json', 'eslint.config.js') }}"
+
       - name: 'Validate NOTICES.txt'
         run: 'git diff --exit-code packages/vscode-ide-companion/NOTICES.txt'
 
@@ -111,10 +125,9 @@ jobs:
           args: '--verbose --accept 200,503 ./**/*.md'
           fail: true
   test_linux:
-    name: 'Test (Linux)'
+    name: 'Test (Linux) - ${{ matrix.shard }}'
     runs-on: 'gemini-cli-ubuntu-16-core'
     needs:
-      - 'lint'
       - 'merge_queue_skipper'
     if: "${{needs.merge_queue_skipper.outputs.skip == 'false'}}"
     permissions:
@@ -127,6 +140,9 @@ jobs:
           - '20.x'
           - '22.x'
           - '24.x'
+        shard:
+          - 'cli'
+          - 'others'
     steps:
       - name: 'Checkout'
         uses: 'actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8' # ratchet:actions/checkout@v5
@@ -146,7 +162,14 @@ jobs:
       - name: 'Run tests and generate reports'
         env:
           NO_COLOR: true
-        run: 'npm run test:ci'
+        run: |
+          if [[ "${{ matrix.shard }}" == "cli" ]]; then
+            npm run test:ci --workspace @google/gemini-cli
+          else
+            # Explicitly list non-cli packages to ensure they are sharded correctly
+            npm run test:ci --workspace @google/gemini-cli-core --workspace @google/gemini-cli-a2a-server --workspace gemini-cli-vscode-ide-companion --workspace @google/gemini-cli-test-utils --if-present
+            npm run test:scripts
+          fi
 
       - name: 'Bundle'
         run: 'npm run bundle'
@@ -162,7 +185,7 @@ jobs:
           ${{ always() && (github.event.pull_request.head.repo.full_name == github.repository) }}
         uses: 'dorny/test-reporter@dc3a92680fcc15842eef52e8c4606ea7ce6bd3f3' # ratchet:dorny/test-reporter@v2
         with:
-          name: 'Test Results (Node ${{ matrix.node-version }})'
+          name: 'Test Results (Node ${{ matrix.node-version }}, ${{ matrix.shard }})'
           path: 'packages/*/junit.xml'
           reporter: 'java-junit'
           fail-on-error: 'false'
@@ -176,10 +199,9 @@ jobs:
           path: 'packages/*/junit.xml'
 
   test_mac:
-    name: 'Test (Mac)'
+    name: 'Test (Mac) - ${{ matrix.shard }}'
     runs-on: '${{ matrix.os }}'
     needs:
-      - 'lint'
       - 'merge_queue_skipper'
     if: "${{needs.merge_queue_skipper.outputs.skip == 'false'}}"
     permissions:
@@ -195,6 +217,9 @@ jobs:
           - '20.x'
           - '22.x'
           - '24.x'
+        shard:
+          - 'cli'
+          - 'others'
     steps:
       - name: 'Checkout'
         uses: 'actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8' # ratchet:actions/checkout@v5
@@ -214,7 +239,14 @@ jobs:
       - name: 'Run tests and generate reports'
         env:
           NO_COLOR: true
-        run: 'npm run test:ci -- --coverage.enabled=false'
+        run: |
+          if [[ "${{ matrix.shard }}" == "cli" ]]; then
+            npm run test:ci --workspace @google/gemini-cli -- --coverage.enabled=false
+          else
+            # Explicitly list non-cli packages to ensure they are sharded correctly
+            npm run test:ci --workspace @google/gemini-cli-core --workspace @google/gemini-cli-a2a-server --workspace gemini-cli-vscode-ide-companion --workspace @google/gemini-cli-test-utils --if-present -- --coverage.enabled=false
+            npm run test:scripts
+          fi
 
       - name: 'Bundle'
         run: 'npm run bundle'
@@ -230,7 +262,7 @@ jobs:
           ${{ always() && (github.event.pull_request.head.repo.full_name == github.repository) }}
         uses: 'dorny/test-reporter@dc3a92680fcc15842eef52e8c4606ea7ce6bd3f3' # ratchet:dorny/test-reporter@v2
         with:
-          name: 'Test Results (Node ${{ matrix.node-version }})'
+          name: 'Test Results (Node ${{ matrix.node-version }}, ${{ matrix.shard }})'
           path: 'packages/*/junit.xml'
           reporter: 'java-junit'
           fail-on-error: 'false'
diff --git a/.prettierignore b/.prettierignore
index 7b8a75a110..120f04c358 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -17,5 +17,6 @@ eslint.config.js
 **/generated
 gha-creds-*.json
 junit.xml
+.gemini-linters/
 Thumbs.db
 .pytest_cache
diff --git a/package.json b/package.json
index 04c7077437..4328d4e637 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "test:integration:sandbox:none": "cross-env GEMINI_SANDBOX=false vitest run --root ./integration-tests",
     "test:integration:sandbox:docker": "cross-env GEMINI_SANDBOX=docker npm run build:sandbox && cross-env GEMINI_SANDBOX=docker vitest run --root ./integration-tests",
     "test:integration:sandbox:podman": "cross-env GEMINI_SANDBOX=podman vitest run --root ./integration-tests",
-    "lint": "eslint . --ext .ts,.tsx && eslint integration-tests && eslint scripts",
+    "lint": "eslint . --cache",
     "lint:fix": "eslint . --fix --ext .ts,.tsx && eslint integration-tests --fix && eslint scripts --fix && npm run format",
     "lint:ci": "npm run lint:all",
     "lint:all": "node scripts/lint.js",
diff --git a/scripts/lint.js b/scripts/lint.js
index 255c572551..c0c5689a01 100644
--- a/scripts/lint.js
+++ b/scripts/lint.js
@@ -21,7 +21,8 @@ const ACTIONLINT_VERSION = '1.7.7';
 const SHELLCHECK_VERSION = '0.11.0';
 const YAMLLINT_VERSION = '1.35.1';
 
-const TEMP_DIR = join(tmpdir(), 'gemini-cli-linters');
+const TEMP_DIR =
+  process.env.GEMINI_LINT_TEMP_DIR || join(tmpdir(), 'gemini-cli-linters');
 
 function getPlatformArch() {
   const platform = process.platform;
@@ -134,7 +135,9 @@ function runCommand(command, stdio = 'inherit') {
 
 export function setupLinters() {
   console.log('Setting up linters...');
-  rmSync(TEMP_DIR, { recursive: true, force: true });
+  if (!process.env.GEMINI_LINT_TEMP_DIR) {
+    rmSync(TEMP_DIR, { recursive: true, force: true });
+  }
   mkdirSync(TEMP_DIR, { recursive: true });
 
   for (const linter in LINTERS) {
@@ -183,6 +186,9 @@ export function runYamllint() {
 export function runPrettier() {
   console.log('\nRunning Prettier...');
   if (!runCommand('prettier --check .')) {
+    console.log(
+      'Prettier check failed. Please run "npm run format" to fix formatting issues.',
+    );
     process.exit(1);
   }
 }