diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index afaec53..30ca199 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -19,7 +19,12 @@ jobs:
     timeout-minutes: 30
     outputs:
       version: ${{ steps.version.outputs.version }}
+    env:
+      VERSION: ${{ needs.build.outputs.version }}
     steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           fetch-depth: 0
@@ -49,7 +54,14 @@ jobs:
         with:
           name: package
           path: artifacts
-      - uses: pypa/gh-action-pypi-publish@dc37677b2e1c63e2034f94d8a5b11f265b73ba33 # v1.14.2
+      - id: select
+        run: |
+          count=$(python3 scripts/release-files.py "$VERSION" artifacts --pending pending)
+          echo "count=$count" >> "$GITHUB_OUTPUT"
+      - if: steps.select.outputs.count != '0'
+        uses: pypa/gh-action-pypi-publish@dc37677b2e1c63e2034f94d8a5b11f265b73ba33 # v1.14.2
         with:
-          packages-dir: artifacts/
+          packages-dir: pending/
           attestations: true
+      - name: Verify both distributions on PyPI
+        run: python3 scripts/release-files.py "$VERSION" artifacts
diff --git a/scripts/release-files.py b/scripts/release-files.py
new file mode 100644
index 0000000..d08ca21
--- /dev/null
+++ b/scripts/release-files.py
@@ -0,0 +1,68 @@
+"""Verify PyPI release files and select the missing distributions for publication."""
+
+import argparse
+import hashlib
+import json
+import re
+import shutil
+import sys
+import time
+import urllib.error
+import urllib.request
+from pathlib import Path
+
+PACKAGE = "proofline-sdk"
+
+
+def published(version: str) -> dict[str, str]:
+    try:
+        url = f"https://pypi.org/pypi/{PACKAGE}/{version}/json"
+        with urllib.request.urlopen(url, timeout=30) as response:
+            release = json.load(response)
+    except urllib.error.HTTPError as error:
+        if error.code == 404:
+            return {}
+        raise
+    if release["info"]["name"] != PACKAGE or release["info"]["version"] != version:
+        raise ValueError("PyPI returned a different distribution")
+    return {file["filename"]: file["digests"]["sha256"] for file in release["urls"]}
+
+
+def missing(expected: dict[str, str], released: dict[str, str]) -> list[str]:
+    for name, digest in released.items():
+        if expected.get(name) != digest:
+            raise ValueError(f"PyPI has unexpected content for {name}")
+    return sorted(expected.keys() - released.keys())
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("version")
+    parser.add_argument("artifacts", type=Path)
+    parser.add_argument("--pending", type=Path, help="copy only missing files to a new directory")
+    args = parser.parse_args()
+    if not re.fullmatch(r"(0|[1-9][0-9]*)(\.(0|[1-9][0-9]*)){2}", args.version):
+        raise ValueError("expected a stable package version")
+    files = sorted(args.artifacts.iterdir())
+    prefix = f"proofline_sdk-{args.version}"
+    if {file.name for file in files} != {prefix + ".tar.gz", prefix + "-py3-none-any.whl"}:
+        raise ValueError("expected the wheel and source distribution for this version")
+    expected = {file.name: hashlib.sha256(file.read_bytes()).hexdigest() for file in files}
+    if args.pending:
+        names = missing(expected, published(args.version))
+        args.pending.mkdir()
+        for name in names:
+            shutil.copyfile(args.artifacts / name, args.pending / name)
+        print(len(names))
+        return
+    for attempt in range(6):
+        names = missing(expected, published(args.version))
+        if not names:
+            return
+        if attempt < 5:
+            time.sleep(5)
+    sys.exit("PyPI is missing " + ", ".join(names))
+
+
+if __name__ == "__main__":
+    main()