diff --git a/docs/paykit-ios-sdk-preparation.md b/docs/paykit-ios-sdk-preparation.md
new file mode 100644
index 0000000..7ae65cb
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+++ b/docs/paykit-ios-sdk-preparation.md
@@ -0,0 +1,36 @@
+# Prepare the Paykit iOS SDK
+
+`pubky/paykit-rs` is an SDK, not an installable companion app. Its iOS artifact
+is `Paykit.xcframework.zip`, so the `.app` companion cache does not represent its
+availability. The existing `paykit-server` fixture is a separate component.
+
+For the trusted `v0.1.0-rc73` release, prepare a companion checkout at
+`0eff3d4e694ba0dbbea2d47852fe796e456671b0` using the review stack's
+`prepare_test_checkout.py --layout worktrees --companion --repo pubky/paykit-rs
+--head 0eff3d4e694ba0dbbea2d47852fe796e456671b0 --pr <app-pr>` command.
+Use the printed `path` with the helper on a Mac with Xcode:
+
+```bash
+python3 scripts/prepare-paykit-ios-sdk.py \
+  --checkout /path/to/paykit-rs-checkout \
+  --output artifacts/paykit-rc73
+```
+
+The helper verifies the checkout revision, unchanged tracked files, SwiftPM
+manifest URL and checksum, and the downloaded archive's published SHA256
+`511715acf3ca84e322d19ea6651c767c98b5325845d571abe2a9527b1eb6ae26`.
+It then builds and links the published Swift bindings and upstream compile
+fixtures against both arm64 iOS slices, without a simulator or device.
+`verified.json` records the exact revision, archive, checksum and checks.
+A repeat invocation verifies the retained archive again before using it.
+
+Keep the app's pinned SwiftPM dependency and release URL when building it.
+The extracted framework proves artifact availability; it is not a local package
+override or a replacement for SwiftPM's checksum verification. This helper
+does not build the app, install anything on a device, or drive a QA item.
+
+The helper's corruption check runs with:
+
+```bash
+python3 -B scripts/test_prepare_paykit_ios_sdk.py
+```
diff --git a/scripts/prepare-paykit-ios-sdk.py b/scripts/prepare-paykit-ios-sdk.py
new file mode 100644
index 0000000..aa87f7a
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+++ b/scripts/prepare-paykit-ios-sdk.py
@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+"""Prepare the published rc73 SDK without changing an app's SwiftPM dependencies."""
+import argparse
+import hashlib
+import json
+from pathlib import Path
+import subprocess
+import zipfile
+
+COMMIT = "0eff3d4e694ba0dbbea2d47852fe796e456671b0"
+TAG = "v0.1.0-rc73"
+CHECKSUM = "511715acf3ca84e322d19ea6651c767c98b5325845d571abe2a9527b1eb6ae26"
+URL = f"https://github.com/pubky/paykit-rs/releases/download/{TAG}/Paykit.xcframework.zip"
+
+
+def capture(*args):
+    return subprocess.check_output(args, text=True).strip()
+
+
+def verify_archive(archive):
+    digest = hashlib.sha256(archive.read_bytes()).hexdigest()
+    if digest != CHECKSUM:
+        raise ValueError(f"Archive checksum mismatch: {digest}")
+    with zipfile.ZipFile(archive) as zipped:
+        for name in zipped.namelist():
+            if Path(name).is_absolute() or ".." in Path(name).parts:
+                raise ValueError(f"Unsafe archive entry: {name}")
+    return digest
+
+
+def prepare(checkout, output):
+    checkout = checkout.resolve()
+    output = output.resolve()
+    if capture("git", "-C", str(checkout), "rev-parse", "HEAD") != COMMIT:
+        raise ValueError(f"SDK checkout must be at {COMMIT}")
+    subprocess.run(["git", "-C", str(checkout), "diff", "--quiet", "HEAD", "--"], check=True)
+    manifest = json.loads(capture("swift", "package", "--package-path", str(checkout), "dump-package"))
+    binary = next(t for t in manifest["targets"] if t["name"] == "PaykitFFI")
+    if binary.get("url") != URL or binary.get("checksum") != CHECKSUM:
+        raise ValueError("SwiftPM manifest does not name the published rc73 archive")
+    output.mkdir(parents=True, exist_ok=True)
+    archive = output / "Paykit.xcframework.zip"
+    if not archive.exists():
+        subprocess.run([
+            "curl", "--fail", "--location", "--retry", "1", "--connect-timeout", "15",
+            "--max-time", "240", "--output", str(archive), URL,
+        ], check=True)
+    digest = verify_archive(archive)
+    # The checksum is pinned before extraction or compilation.
+    with zipfile.ZipFile(archive) as zipped:
+        zipped.extractall(output)
+    bindings = checkout / "paykit-ffi/bindings/ios"
+    sources = [bindings / name for name in ("paykit.swift", "PaykitPublicKeys.swift", "PaykitRedaction.swift")]
+    sources += [checkout / "paykit-ffi/src/swift" / name for name in (
+        "AllowanceBindingsCompile.swift", "PaymentConversionBindingsCompile.swift",
+    )]
+    for sdk, target, slice_name in (
+        ("iphonesimulator", "arm64-apple-ios15.0-simulator", "ios-arm64-simulator"),
+        ("iphoneos", "arm64-apple-ios15.0", "ios-arm64"),
+    ):
+        library = output / "Paykit.xcframework" / slice_name
+        subprocess.run([
+            "xcrun", "--sdk", sdk, "swiftc", "-emit-library", "-module-name", "Paykit",
+            "-target", target, "-sdk", capture("xcrun", "--sdk", sdk, "--show-sdk-path"),
+            "-module-cache-path", str(output / "module-cache"),
+            "-I", str(library / "Headers"), "-L", str(library), "-lpaykit",
+            *map(str, sources), "-o", str(output / f"Paykit-{slice_name}.dylib"),
+        ], check=True)
+    result = {"repo": "pubky/paykit-rs", "commit": COMMIT, "tag": TAG, "sha256": digest,
+              "archive": str(archive), "xcframework": str(output / "Paykit.xcframework"),
+              "checks": "published bindings and upstream compile fixtures linked for iOS device and simulator"}
+    (output / "verified.json").write_text(json.dumps(result, indent=2) + "\n")
+    print(json.dumps(result))
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--checkout", type=Path, required=True, help="trusted paykit-rs checkout at rc73")
+    parser.add_argument("--output", type=Path, required=True, help="run-owned artifact directory")
+    args = parser.parse_args()
+    prepare(args.checkout, args.output)
diff --git a/scripts/test_prepare_paykit_ios_sdk.py b/scripts/test_prepare_paykit_ios_sdk.py
new file mode 100644
index 0000000..9592c1a
--- /dev/null
+++ b/scripts/test_prepare_paykit_ios_sdk.py
@@ -0,0 +1,22 @@
+"""The SDK preparer must reject a corrupt archive before extracting it."""
+import importlib.util
+from pathlib import Path
+import tempfile
+import unittest
+
+spec = importlib.util.spec_from_file_location("prepare", Path(__file__).with_name("prepare-paykit-ios-sdk.py"))
+prepare = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(prepare)
+
+
+class ArchiveChecks(unittest.TestCase):
+    def test_corrupt_archive_is_rejected(self):
+        with tempfile.TemporaryDirectory() as folder:
+            archive = Path(folder) / "Paykit.xcframework.zip"
+            archive.write_bytes(b"corrupt release archive")
+            with self.assertRaisesRegex(ValueError, "checksum mismatch"):
+                prepare.verify_archive(archive)
+
+
+if __name__ == "__main__":
+    unittest.main()