diff --git a/.github/workflows/compiler_playground.yml b/.github/workflows/compiler_playground.yml
index edd95e365e..a922237cd5 100644
--- a/.github/workflows/compiler_playground.yml
+++ b/.github/workflows/compiler_playground.yml
@@ -42,6 +42,7 @@ jobs:
             **/node_modules
           key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Check Playwright version
         id: playwright_version
         run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
diff --git a/.github/workflows/compiler_prereleases.yml b/.github/workflows/compiler_prereleases.yml
index 7928bd430e..3db1db2cdd 100644
--- a/.github/workflows/compiler_prereleases.yml
+++ b/.github/workflows/compiler_prereleases.yml
@@ -51,6 +51,7 @@ jobs:
             **/node_modules
           key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Publish packages to npm
         run: |
           cp ./scripts/release/ci-npmrc ~/.npmrc
diff --git a/.github/workflows/compiler_typescript.yml b/.github/workflows/compiler_typescript.yml
index 9c749a3bfb..f6f79d65e6 100644
--- a/.github/workflows/compiler_typescript.yml
+++ b/.github/workflows/compiler_typescript.yml
@@ -47,11 +47,13 @@ jobs:
           cache-dependency-path: compiler/yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
           key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler lint
 
   # Hardcoded to improve parallelism
@@ -73,6 +75,7 @@ jobs:
             **/node_modules
           key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler jest
 
   test:
@@ -98,6 +101,7 @@ jobs:
             **/node_modules
           key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: xvfb-run -a yarn workspace ${{ matrix.workspace_name }} test
         if: runner.os == 'Linux' && matrix.workspace_name == 'react-forgive'
       - run: yarn workspace ${{ matrix.workspace_name }} test
diff --git a/.github/workflows/devtools_regression_tests.yml b/.github/workflows/devtools_regression_tests.yml
index cb6a5b68a8..0b70cfaf4e 100644
--- a/.github/workflows/devtools_regression_tests.yml
+++ b/.github/workflows/devtools_regression_tests.yml
@@ -40,7 +40,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download react-devtools artifacts for base revision
         run: |
           git fetch origin main
@@ -75,6 +77,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore archived build
         uses: actions/download-artifact@v4
         with:
@@ -134,6 +137,7 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
@@ -169,14 +173,24 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
         run: ls -R build
-      - name: Playwright install deps
-        run: |
-          npx playwright install
-          sudo npx playwright install-deps
+      - name: Check Playwright version
+        id: playwright_version
+        run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
+      - name: Cache Playwright Browsers for version ${{ steps.playwright_version.outputs.playwright_version }}
+        id: cache_playwright_browsers
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/ms-playwright
+          key: playwright-browsers-v6-${{ runner.arch }}-${{ runner.os }}-${{ steps.playwright_version.outputs.playwright_version }}
+      - run: npx playwright install --with-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit != 'true'
+      - run: npx playwright install-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit == 'true'
       - run: ./scripts/ci/download_devtools_regression_build.js ${{ matrix.version }}
       - run: ls -R build-regression
       - run: ./scripts/ci/run_devtools_e2e_tests.js ${{ matrix.version }}
diff --git a/.github/workflows/runtime_eslint_plugin_e2e.yml b/.github/workflows/runtime_eslint_plugin_e2e.yml
index 9b3d134204..92921646c1 100644
--- a/.github/workflows/runtime_eslint_plugin_e2e.yml
+++ b/.github/workflows/runtime_eslint_plugin_e2e.yml
@@ -46,17 +46,20 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock', 'fixtures/eslint-v*/yarn.lock') }}
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd compiler install --frozen-lockfile
-      - name: Build plugin
-        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
-        run: node build.mjs
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Install fixture dependencies
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Build plugin
+        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
+        run: node build.mjs
       - name: Run lint test
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn lint
diff --git a/.github/workflows/runtime_prereleases.yml b/.github/workflows/runtime_prereleases.yml
index 1449f6af5a..e3cd5bd1a2 100644
--- a/.github/workflows/runtime_prereleases.yml
+++ b/.github/workflows/runtime_prereleases.yml
@@ -51,7 +51,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: |
           GH_TOKEN=${{ secrets.GH_TOKEN }} scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
           cp ./scripts/release/ci-npmrc ~/.npmrc
diff --git a/.github/workflows/runtime_releases_from_npm_manual.yml b/.github/workflows/runtime_releases_from_npm_manual.yml
index 4bc3957486..51e3843955 100644
--- a/.github/workflows/runtime_releases_from_npm_manual.yml
+++ b/.github/workflows/runtime_releases_from_npm_manual.yml
@@ -78,7 +78,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: cp ./scripts/release/ci-npmrc ~/.npmrc
       - if: '${{ inputs.only_packages }}'
         name: 'Prepare ${{ inputs.only_packages }} from NPM'
diff --git a/.github/workflows/shared_lint.yml b/.github/workflows/shared_lint.yml
index e14e9a252b..3c359cff22 100644
--- a/.github/workflows/shared_lint.yml
+++ b/.github/workflows/shared_lint.yml
@@ -29,6 +29,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -36,6 +37,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn prettier-check
 
   eslint:
@@ -50,6 +52,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -57,6 +60,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: node ./scripts/tasks/eslint
 
   check_license:
@@ -71,6 +75,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -78,6 +83,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/check_license.sh
 
   test_print_warnings:
@@ -92,6 +98,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -99,4 +106,5 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/test_print_warnings.sh
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js b/packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js
index 52a0f4bb2f..e80b745587 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js
@@ -28,7 +28,3 @@ export const enableSiblingPrerendering = __VARIANT__;
 export const enableFastAddPropertiesInDiffing = __VARIANT__;
 export const enableLazyPublicInstanceInFabric = __VARIANT__;
 export const renameElementSymbol = __VARIANT__;
-export const ownerStackLimit: number = __VARIANT__
-  ? // Some value that doesn't impact existing tests
-    500
-  : 1e4;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index 12a8d2bb25..70857c99e5 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -30,7 +30,6 @@ export const {
   enableFastAddPropertiesInDiffing,
   enableLazyPublicInstanceInFabric,
   renameElementSymbol,
-  ownerStackLimit,
 } = dynamicFlags;
 
 // The rest of the flags are static for better dead code elimination.
@@ -84,6 +83,7 @@ export const enableViewTransition = false;
 export const enableSwipeTransition = false;
 export const enableScrollEndPolyfill = true;
 export const enableFragmentRefs = false;
+export const ownerStackLimit = 1e4;
 
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
index 89e0cce296..46442874e7 100644
--- a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
+++ b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
@@ -42,11 +42,6 @@ export const enableComponentPerformanceTrack = __VARIANT__;
 export const enableScrollEndPolyfill = __VARIANT__;
 export const enableFragmentRefs = __VARIANT__;
 
-export const ownerStackLimit: number = __VARIANT__
-  ? // Some value that doesn't impact existing tests
-    500
-  : 1e4;
-
 // TODO: These flags are hard-coded to the default values used in open source.
 // Update the tests so that they pass in either mode, then set these
 // to __VARIANT__.
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index 2394f883d4..64a5ff4126 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -39,7 +39,6 @@ export const {
   enableComponentPerformanceTrack,
   enableScrollEndPolyfill,
   enableFragmentRefs,
-  ownerStackLimit,
 } = dynamicFeatureFlags;
 
 // On WWW, __EXPERIMENTAL__ is used for a new modern build.
@@ -114,5 +113,7 @@ export const enableLazyPublicInstanceInFabric = false;
 
 export const enableSwipeTransition = false;
 
+export const ownerStackLimit = 1e4;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/scripts/jest/setupTests.www.js b/scripts/jest/setupTests.www.js
index b0b653bb78..9628dc3e1f 100644
--- a/scripts/jest/setupTests.www.js
+++ b/scripts/jest/setupTests.www.js
@@ -17,6 +17,9 @@ jest.mock('shared/ReactFeatureFlags', () => {
   // we remove the flag.
   actual.disableClientCache = __VARIANT__;
 
+  // Some value that doesn't impact existing tests
+  actual.ownerStackLimit = __VARIANT__ ? 500 : 1e4;
+
   return actual;
 });
 
diff --git a/scripts/jest/setupTests.xplat.js b/scripts/jest/setupTests.xplat.js
index 859a506598..3b05a474a0 100644
--- a/scripts/jest/setupTests.xplat.js
+++ b/scripts/jest/setupTests.xplat.js
@@ -22,6 +22,9 @@ jest.mock('shared/ReactFeatureFlags', () => {
   actual.enableScopeAPI = true;
   actual.enableTaint = false;
 
+  // Some value that doesn't impact existing tests
+  actual.ownerStackLimit = __VARIANT__ ? 500 : 1e4;
+
   return actual;
 });