diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 7c30da3..a1fbfe5 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -6,8 +6,10 @@ permissions:
   contents: write
 jobs:
   release:
+    # macOS 26 or later: each runtime imports MLX to check itself, and the default build's
+    # Metal 4 library does not load on earlier macOS.
     runs-on: macos-latest
-    timeout-minutes: 30
+    timeout-minutes: 45
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4.4.0
       - uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e # v6.8.0
@@ -19,10 +21,15 @@ jobs:
           version=${GITHUB_REF_NAME#v}
           uv python install 3.12.12
           python_root="$(uv python dir)/cpython-3.12.12-macos-aarch64-none"
-          "$python_root/bin/python3.12" packaging/build-mlx-runtime.py --python-root "$python_root" --output .build/bundle-mlx
-          python3 packaging/package.py --runtime-dir .build/bundle-mlx --manifest packaging/flint-int4-mlx.json \
-            --version "$version" --output dist/rec-darwin-arm64
-          test "$(dist/rec-darwin-arm64 --version)" = "rec $version"
+          # install.sh picks the -macos15 build on macOS before 26.
+          for target in 26.0:rec-darwin-arm64 15.0:rec-darwin-arm64-macos15; do
+            macos=${target%%:*} artifact=${target#*:}
+            "$python_root/bin/python3.12" packaging/build-mlx-runtime.py --python-root "$python_root" \
+              --macos "$macos" --output ".build/bundle-mlx-$macos"
+            python3 packaging/package.py --runtime-dir ".build/bundle-mlx-$macos" --manifest packaging/flint-int4-mlx.json \
+              --version "$version" --output "dist/$artifact"
+            test "$("dist/$artifact" --version)" = "rec $version"
+          done
       - name: Publish
         env:
           GH_TOKEN: ${{ github.token }}
@@ -38,4 +45,5 @@ jobs:
               ;;
           esac
           gh release create "$GITHUB_REF_NAME" "${notes[@]}" --verify-tag --generate-notes \
-            --title "rec $GITHUB_REF_NAME" dist/rec-darwin-arm64 dist/rec-darwin-arm64.meta
+            --title "rec $GITHUB_REF_NAME" dist/rec-darwin-arm64 dist/rec-darwin-arm64.meta \
+            dist/rec-darwin-arm64-macos15 dist/rec-darwin-arm64-macos15.meta
diff --git a/README.md b/README.md
index 0e08a2a..03ea6e1 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,7 @@ excluded.</sub></p>
 ## Requirements
 
 - Apple Silicon Mac with an M4 Pro, M4 Max, M5 Pro, or M5 Max
+- macOS 15 Sequoia or later
 - At least 48 GB unified memory
 - About 30 GB free disk space
 - [Node.js 22](https://nodejs.org/en/download) and npm for pi
diff --git a/install.sh b/install.sh
index 35c27f7..8be25fd 100644
--- a/install.sh
+++ b/install.sh
@@ -24,7 +24,11 @@ rec_install() (
     esac
   done
   [ "$(uname -s)" = Darwin ] && [ "$(uname -m)" = arm64 ] || fail 'rec requires an Apple Silicon Mac'
-  artifact=rec-darwin-arm64
+  artifact=rec-darwin-arm64 variant=''
+  # The default build's MLX runtime uses Metal 4, which needs macOS 26.
+  macos=$(sw_vers -productVersion) || fail 'could not read the macOS version'
+  [[ "$macos" =~ ^[0-9]+ ]] || fail "unrecognized macOS version: $macos"
+  if [ "${BASH_REMATCH[0]}" -lt 26 ]; then variant=-macos15; artifact=$artifact$variant; fi
   version=${REC_VERSION:-}
   version=${version#v}
   [ -z "$version" ] || [[ "$version" =~ ^[A-Za-z0-9][A-Za-z0-9._-]*$ ]] || fail 'invalid REC_VERSION'
@@ -77,7 +81,7 @@ rec_install() (
   begin 'Checking this Mac'
   doctor=$("$tmp/$artifact" doctor 2>&1) || { printf '%s' "$erase"; printf '%s\n' "$doctor" >&2; fail 'this Mac does not meet the requirements above'; }
   done_step 'This Mac meets the requirements'
-  release="$data/releases/$version"
+  release="$data/releases/$version$variant"
   if [ -e "$release" ]; then
     [ -f "$release/.managed" ] && [ -f "$release/rec" ] || fail 'release directory is not managed'
     installed_hash=$(shasum -a 256 "$release/rec"); installed_hash=${installed_hash%% *}
diff --git a/packaging/build-mlx-runtime.py b/packaging/build-mlx-runtime.py
index 13234d3..dd1aa3c 100644
--- a/packaging/build-mlx-runtime.py
+++ b/packaging/build-mlx-runtime.py
@@ -6,6 +6,8 @@
 
 import argparse
 import json
+import os
+import re
 import shutil
 import subprocess
 import tempfile
@@ -26,9 +28,24 @@ def main():
     )
     parser.add_argument("--output", type=Path, required=True, help="new directory for the runtime")
     parser.add_argument("--uv", default="uv", help="uv executable (default: %(default)s)")
+    parser.add_argument(
+        "--macos",
+        metavar="VERSION",
+        help="oldest macOS the runtime supports, such as 15.0 (default: this Mac's version)",
+    )
     args = parser.parse_args()
     if args.output.exists():
         parser.error("output must be a new directory")
+    if args.macos and not re.fullmatch(r"\d+\.\d+", args.macos):
+        parser.error("--macos must look like 15.0")
+    # MLX publishes a wheel per macOS release; the macOS 26 metallib uses Metal 4 and fails to
+    # load on macOS 15. The deployment target selects those wheels and sets the native
+    # extension's minimum OS.
+    env = dict(os.environ)
+    platform = []
+    if args.macos:
+        env["MACOSX_DEPLOYMENT_TARGET"] = args.macos
+        platform = ["--python-platform", "aarch64-apple-darwin"]
     source_python = args.python_root / "bin/python3.12"
     information = json.loads(
         subprocess.check_output(
@@ -57,6 +74,7 @@ def main():
                 str(wheels),
                 str(ENGINE),
             ],
+            env=env,
             check=True,
         )
         (wheel,) = wheels.glob("rec_mlx-*.whl")
@@ -78,10 +96,12 @@ def main():
                 "--python",
                 str(python),
                 "--break-system-packages",
+                *platform,
                 "--only-binary",
                 ":all:",
                 str(wheel),
             ],
+            env=env,
             check=True,
         )
         launcher = stage / "rec-mlx"
@@ -96,6 +116,7 @@ def main():
                     "os": "darwin",
                     "arch": "arm64",
                     "backend": "metal",
+                    **({"macos": args.macos} if args.macos else {}),
                 },
                 indent=2,
             )
diff --git a/tests/installer_test.py b/tests/installer_test.py
index 8d22788..ea4b092 100644
--- a/tests/installer_test.py
+++ b/tests/installer_test.py
@@ -12,6 +12,7 @@
 ROOT = Path(__file__).resolve().parents[1]
 SCRIPT = ROOT / "install.sh"
 ARTIFACT = "rec-darwin-arm64"
+ARTIFACTS = [ARTIFACT, ARTIFACT + "-macos15"]
 
 
 def fake_rec(version):
@@ -30,15 +31,17 @@ def fake_rec(version):
 
 def publish(directory, version, reported=None, bad_hash=False):
     directory.mkdir(parents=True, exist_ok=True)
-    body = fake_rec(reported or version).encode()
-    (directory / ARTIFACT).write_bytes(body)
-    digest = "0" * 64 if bad_hash else hashlib.sha256(body).hexdigest()
-    (directory / (ARTIFACT + ".meta")).write_text(f"{digest} {len(body)}\n")
+    for artifact in ARTIFACTS:
+        body = fake_rec(reported or version).encode() + f"# {artifact}\n".encode()
+        (directory / artifact).write_bytes(body)
+        digest = "0" * 64 if bad_hash else hashlib.sha256(body).hexdigest()
+        (directory / (artifact + ".meta")).write_text(f"{digest} {len(body)}\n")
 
 
 FIXTURES = {
     "uname": '#!/bin/sh\ncase "$1" in -s) echo "${TEST_OS:-Darwin}";; -m) echo "${TEST_ARCH:-arm64}";; esac\n',
     "curl": "#!/bin/sh\nexit 22\n",
+    "sw_vers": '#!/bin/sh\n[ "$1" = -productVersion ] && echo "${TEST_MACOS:-26.1}"\n',
 }
 
 
@@ -58,7 +61,10 @@ def main():
         publish(releases / "download/v0.6.0", "0.6.0", bad_hash=True)
         bins = root / "bin"
         offline = root / "offline"
-        for directory, names in [(bins, ["uname"]), (offline, ["uname", "curl"])]:
+        for directory, names in [
+            (bins, ["uname", "sw_vers"]),
+            (offline, ["uname", "sw_vers", "curl"]),
+        ]:
             directory.mkdir()
             for name in names:
                 (directory / name).write_text(FIXTURES[name])
@@ -134,6 +140,17 @@ def installed(home):
         assert not (home / "running").exists()
         assert installed(home).parent.name == "0.3.0"
 
+        home, env = new_home({"TEST_MACOS": "15.8.1"})
+        install(env)
+        sequoia = installed(home)
+        assert sequoia == (home / ".local/share/rec/releases/0.3.0-macos15/rec").resolve(), sequoia
+        assert sequoia.read_text().endswith("# rec-darwin-arm64-macos15\n")
+        # After upgrading to macOS 26, the same version installs the default build beside it.
+        install(dict(env, TEST_MACOS="26.0"))
+        assert installed(home).parent.name == "0.3.0"
+        assert installed(home).read_text().endswith("# rec-darwin-arm64\n")
+        assert "unrecognized macOS" in install(dict(env, TEST_MACOS="beta"), ok=False).stderr
+
         home, env = new_home()
         install(env, "--serve")
         assert (home / "serve.log").read_text() == "serve\n"
@@ -157,7 +174,7 @@ def installed(home):
         server.shutdown()
         server.server_close()
         print(
-            "Installer: public default URL, pins, idempotence, checksum/version/device rejection, running-server stop, --serve, platform checks and collision preservation passed"
+            "Installer: public default URL, pins, idempotence, checksum/version/device rejection, running-server stop, --serve, platform checks, macOS 15 build selection and collision preservation passed"
         )