diff --git a/.github/workflows/build_ios_simulator_app.yml b/.github/workflows/build_ios_simulator_app.yml
index c44f7fd1..1f53d17d 100644
--- a/.github/workflows/build_ios_simulator_app.yml
+++ b/.github/workflows/build_ios_simulator_app.yml
@@ -13,7 +13,7 @@ on:
         description: "Should a parent repo be used for customizations? (Required for branded builds)"
       runner-label:
         type: string
-        default: "macos-latest"
+        default: "macos-15"
       customizations_env_content:
         required: false
         type: string
@@ -61,7 +61,7 @@ jobs:
       - name: Setup Xcode
         uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: latest-stable
+          xcode-version: 16.4
 
       - name: Build release .app for simulators by @${{ github.actor }}
         run: |
diff --git a/.github/workflows/build_tvos_simulator_app.yml b/.github/workflows/build_tvos_simulator_app.yml
index 531f6853..6e198f2b 100644
--- a/.github/workflows/build_tvos_simulator_app.yml
+++ b/.github/workflows/build_tvos_simulator_app.yml
@@ -13,7 +13,7 @@ on:
         description: "Should a parent repo be used for customizations? (Required for branded builds)"
       runner-label:
         type: string
-        default: "macos-latest"
+        default: "macos-15"
       customizations_env_content:
         required: false
         type: string
@@ -61,7 +61,7 @@ jobs:
       - name: Setup Xcode
         uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: latest-stable
+          xcode-version: 16.4
 
       - name: Build release tvOS .app for simulators by @${{ github.actor }}
         run: |
diff --git a/.github/workflows/deploy-static-main.yml b/.github/workflows/deploy-static-main.yml
index 0dc61933..dd62e376 100644
--- a/.github/workflows/deploy-static-main.yml
+++ b/.github/workflows/deploy-static-main.yml
@@ -54,7 +54,7 @@ jobs:
       - name: Set macos runner
         id: set-macos-runner
         run: |
-          echo "runner-label=${{ vars.PREFERRED_MACOS_RUNNER || 'macos-latest' }}" >> $GITHUB_OUTPUT
+          echo "runner-label=${{ vars.PREFERRED_MACOS_RUNNER || 'macos-15' }}" >> $GITHUB_OUTPUT
 
   build_info:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/testflight.yml b/.github/workflows/testflight.yml
index 446882fa..c3b2f398 100644
--- a/.github/workflows/testflight.yml
+++ b/.github/workflows/testflight.yml
@@ -17,7 +17,7 @@ on:
         description: Upload iOS (iphoneos) or tvOS (appletvos) app
       runner-label:
         type: string
-        default: "macos-latest"
+        default: "macos-15"
       customizations_env_content:
         required: false
         type: string
@@ -135,7 +135,7 @@ jobs:
       - name: Setup Xcode
         uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: latest-stable
+          xcode-version: 16.4
 
       - name: Build and archive app for upload to Testflight by @${{ github.actor }}
         env:
diff --git a/CLAUDE.md b/CLAUDE.md
index 12145abe..ce559b19 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -237,6 +237,16 @@ Examples: `cust-app-blender`, `cust-app-xrtube`, `cust-app-basspistol`, `cust-ap
   - App Store Connect and Google Play accounts
   - Certificate/signing keys in GitHub Secrets
 
+### macOS Runner & Xcode Version
+
+iOS/tvOS build workflows pin both the macOS runner image and Xcode version to ensure compatibility with Expo SDK 52 / React Native 0.76:
+
+- **Xcode:** Pinned to `16.4` via `maxim-lobanov/setup-xcode@v1`. Do NOT use `latest-stable` — the `macos-15` runner now ships both Xcode 16.x and Xcode 26.3 RC, and `latest-stable` resolves to 26.x which is incompatible with React Native 0.76. Apple skipped versions 17–25 (jumped from 16 to 26).
+- **Runner:** `macos-15` (default in reusable workflow inputs). Do NOT use `macos-latest` — it resolves to macOS 26.
+- **Override:** The main repo can override the runner via `PREFERRED_MACOS_RUNNER` variable in the `owntube` environment. Downstream branded app repos use the default from the reusable workflow inputs.
+
+When upgrading Expo SDK or React Native, re-evaluate whether newer Xcode/runner versions are compatible and update the pins accordingly.
+
 ### Environments
 
 1. **`owntube` environment:** Stores sensitive secrets for app builds