README: note Xcode 26 requirement

.github/workflows/test.yml

@@ -18,7 +18,6 @@ jobs:
       - build-nix
       - build-snap
       - build-macos
-      - build-macos-sequoia-stable
       - build-macos-tahoe
       - build-macos-matrix
       - build-windows
@@ -310,46 +309,6 @@ jobs:
           cd macos
           xcodebuild -target Ghostty-iOS "CODE_SIGNING_ALLOWED=NO"
 
-  build-macos-sequoia-stable:
-    runs-on: namespace-profile-ghostty-macos-sequoia
-    needs: test
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      # Install Nix and use that to run our tests so our environment matches exactly.
-      - uses: cachix/install-nix-action@v31
-        with:
-          nix_path: nixpkgs=channel:nixos-unstable
-      - uses: cachix/cachix-action@v16
-        with:
-          name: ghostty
-          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
-
-      - name: Xcode Select
-        run: sudo xcode-select -s /Applications/Xcode_16.4.app
-
-      - name: get the Zig deps
-        id: deps
-        run: nix build -L .#deps && echo "deps=$(readlink ./result)" >> $GITHUB_OUTPUT
-
-      # GhosttyKit is the framework that is built from Zig for our native
-      # Mac app to access.
-      - name: Build GhosttyKit
-        run: nix develop -c zig build --system ${{ steps.deps.outputs.deps }}
-
-      # The native app is built with native Xcode tooling. This also does
-      # codesigning. IMPORTANT: this must NOT run in a Nix environment.
-      # Nix breaks xcodebuild so this has to be run outside.
-      - name: Build Ghostty.app
-        run: cd macos && xcodebuild -target Ghostty
-
-      # Build the iOS target without code signing just to verify it works.
-      - name: Build Ghostty iOS
-        run: |
-          cd macos
-          xcodebuild -target Ghostty-iOS "CODE_SIGNING_ALLOWED=NO"
-
   build-macos-tahoe:
     runs-on: namespace-profile-ghostty-macos-tahoe
     needs: test

README.md

@@ -224,6 +224,28 @@ macOS users don't require any additional dependencies.
 > source tarballs, see the
 > [website](http://ghostty.org/docs/install/build).
 
+### Xcode Version and SDKs
+
+Building the Ghostty macOS app requires that Xcode, the macOS SDK,
+and the iOS SDK are all installed.
+
+A common issue is that the incorrect version of Xcode is either
+installed or selected. Use the `xcode-select` command to
+ensure that the correct version of Xcode is selected:
+
+```shell-session
+sudo xcode-select --switch /Applications/Xcode-beta.app
+```
+
+> [!IMPORTANT]
+>
+> Main branch development of Ghostty is preparing for the next major
+> macOS release, Tahoe (macOS 26). Therefore, the main branch requires
+> **Xcode 26 and the macOS 26 SDK**.
+>
+> You do not need to be running on macOS 26 to build Ghostty, you can
+> still use Xcode 26 beta on macOS 15 stable.
+
 ### Linting
 
 #### Prettier