diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 24168af..03202c6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -94,6 +94,9 @@ jobs:
         if: runner.os != 'macOS' || matrix.arch != 'x86_64'
         shell: bash
         run: meson test -C build --list | grep -q aegisub-wrapper
+      - name: Check macOS release tests are enabled
+        if: runner.os == 'macOS'
+        run: meson test -C build --list | grep -q macos-release-tools
       - name: Test
         run: meson test -C build --print-errorlogs
       - name: Check binary architecture and runtime dependencies
diff --git a/docs/releasing.md b/docs/releasing.md
new file mode 100644
index 0000000..0be878a
--- /dev/null
+++ b/docs/releasing.md
@@ -0,0 +1,53 @@
+# macOS release signing
+
+Use the same Developer ID Application identity as Aegisub: its library
+validation requires native Automation libraries to have the same Team ID.
+These scripts use downloaded CI artifacts without rebuilding dependencies.
+They require macOS, Xcode command-line tools, your signing certificate, and
+a stored `notarytool` profile. Signing and notarization need network access.
+
+Check out the commit that produced the artifacts, then download both macOS
+packages from its successful CI run:
+
+```sh
+gh run download RUN_ID --name SubInspector-macos-arm64 --dir build/SubInspector-macos-arm64
+gh run download RUN_ID --name SubInspector-macos-x86_64 --dir build/SubInspector-macos-x86_64
+
+export SUBINSPECTOR_SIGNATURE='Developer ID Application: Your Name (TEAMID)'
+export SUBINSPECTOR_TEAM_ID=TEAMID
+export SUBINSPECTOR_NOTARY_PROFILE=aegisub-notary
+```
+
+You can reuse Aegisub's existing notary profile. To create a new one, run
+`xcrun notarytool store-credentials "$SUBINSPECTOR_NOTARY_PROFILE"` once.
+For non-default keychains, set `SUBINSPECTOR_SIGNING_KEYCHAIN` and/or
+`SUBINSPECTOR_NOTARY_KEYCHAIN`. `SUBINSPECTOR_NOTARY_TIMEOUT` defaults to `30m`.
+Set `SUBINSPECTOR_TEAM_ID` to the 10-character `TeamIdentifier` shown by
+`codesign --display --verbose=4 /path/to/Aegisub.app`. Notarization verifies
+that the dylib is signed by that team before submitting it to Apple.
+
+```sh
+for arch in arm64 x86_64; do
+  artifact="build/SubInspector-macos-$arch"
+  tools/osx-sign.sh "$artifact"
+  tools/osx-notarize.sh "$artifact" "$artifact.zip"
+done
+```
+
+Signing verifies the downloaded checksums, signs the dylib with a secure
+timestamp, and atomically replaces `SHA256SUMS`. The notarization script checks
+the signed package and produces the requested ZIP only after Apple returns `Accepted`.
+The ZIP's top-level folder matches its filename without `.zip`, regardless of
+the input directory's name. It refuses to overwrite an existing output, including
+one created while awaiting notarization. On failure it prints the submission
+ID/status and requests Apple's log when an ID is available; rerun after fixing
+the issue. `SUBINSPECTOR_SIGNATURE=-` permits local ad-hoc signing tests, but
+those artifacts cannot pass the notarization script's Developer ID check.
+
+Test the signed dylibs through the wrapper in the signed Aegisub release.
+Publish the accepted ZIPs and use the **signed** dylibs when updating the
+DependencyControl feed's download URLs and hashes. Keep the wrapper version,
+changelog, and dependency changes together with that feed update.
+
+Standalone dylibs and ZIPs cannot have notarization tickets stapled to them;
+Apple records tickets online. See [Apple's notarization workflow](https://developer.apple.com/documentation/security/customizing-the-notarization-workflow).
diff --git a/readme.md b/readme.md
index d5a8911..c6b9ce2 100644
--- a/readme.md
+++ b/readme.md
@@ -46,6 +46,8 @@ Should you prefer a Visual Studio solution, just pass `--backend=vs` along with
 
 ### Help and Support
 
+For macOS releases, see the [signing instructions](docs/releasing.md).
+
 Talk to `CoffeeFlux` on `irc.rizon.net`.
 
 [libass]: https://github.com/libass/libass
diff --git a/tests/meson.build b/tests/meson.build
index d9e6db3..827b8e7 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -3,6 +3,13 @@ render_test = executable('render-test', 'render.c',
     link_with: subinspector)
 test('render', render_test)
 
+if build_machine.system() == 'darwin' and host_machine.system() == 'darwin'
+    python = import('python').find_installation()
+    test('macos-release-tools', python,
+        args: [files('osx-release.py'), subinspector.full_path()],
+        depends: subinspector)
+endif
+
 if not meson.is_cross_build()
     luajit = find_program('luajit', required: false)
     moonc = find_program('moonc', required: false)
diff --git a/tests/osx-release.py b/tests/osx-release.py
new file mode 100644
index 0000000..e66cbff
--- /dev/null
+++ b/tests/osx-release.py
@@ -0,0 +1,156 @@
+"""Exercise real ad-hoc signing and the release flow without Apple credentials."""
+
+import hashlib
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+
+binary = Path(sys.argv.pop(1)).resolve()
+tools = Path(__file__).resolve().parents[1] / 'tools'
+
+
+class ReleaseTests(unittest.TestCase):
+    def setUp(self):
+        self.temporary = tempfile.TemporaryDirectory(prefix='SubInspector signing ')
+        self.addCleanup(self.temporary.cleanup)
+        self.root = Path(self.temporary.name)
+        self.artifact = self.root / 'macOS artifact'
+        self.artifact.mkdir()
+        shutil.copy2(binary, self.artifact / 'libSubInspector.dylib')
+        (self.artifact / 'COPYING').write_text('License fixture\n')
+        (self.artifact / 'licenses/libass').mkdir(parents=True)
+        (self.artifact / 'licenses/libass/COPYING').write_text('Nested license fixture\n')
+        with (self.artifact / 'SHA256SUMS').open('w') as checksums:
+            for name in ['COPYING', 'libSubInspector.dylib', 'licenses/libass/COPYING']:
+                digest = hashlib.sha256((self.artifact / name).read_bytes()).hexdigest()
+                checksums.write(f'{digest}  {name}\n')
+        self.env = dict(os.environ, SUBINSPECTOR_SIGNATURE='-',
+                        SUBINSPECTOR_TEAM_ID='TESTTEAM01',
+                        SUBINSPECTOR_NOTARY_PROFILE='test-profile')
+        self.commands = self.root / 'commands'
+        self.commands.mkdir()
+        # Never contact Apple, even if a validation regression reaches xcrun.
+        (self.commands / 'xcrun').write_text('#!/bin/sh\necho "Unexpected notary call"\nexit 1\n')
+        (self.commands / 'xcrun').chmod(0o755)
+        self.env['PATH'] = str(self.commands) + os.pathsep + self.env['PATH']
+
+    def run_tool(self, name, *args):
+        return subprocess.run([tools / name, self.artifact, *args], env=self.env,
+                              text=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+
+    def sign(self):
+        result = self.run_tool('osx-sign.sh')
+        self.assertEqual(result.returncode, 0, result.stdout)
+        for line in (self.artifact / 'SHA256SUMS').read_text().splitlines():
+            digest, name = line.split('  ', 1)
+            self.assertEqual(digest, hashlib.sha256((self.artifact / name).read_bytes()).hexdigest())
+
+    def test_sign_and_reject_adhoc_notarization(self):
+        self.sign()
+        output = self.root / 'release.zip'
+        result = self.run_tool('osx-notarize.sh', output)
+        self.assertNotEqual(result.returncode, 0, result.stdout)
+        self.assertFalse(output.exists())
+        self.assertNotIn('Unexpected notary call', result.stdout)
+
+    def test_corrupt_download_is_not_signed(self):
+        original = (self.artifact / 'libSubInspector.dylib').read_bytes()
+        checksums = (self.artifact / 'SHA256SUMS').read_bytes()
+        (self.artifact / 'COPYING').write_text('Changed after download')
+        result = self.run_tool('osx-sign.sh')
+        self.assertNotEqual(result.returncode, 0, result.stdout)
+        self.assertEqual(original, (self.artifact / 'libSubInspector.dylib').read_bytes())
+        self.assertEqual(checksums, (self.artifact / 'SHA256SUMS').read_bytes())
+
+    def test_wrong_platform_is_rejected(self):
+        manifest = self.artifact / 'SHA256SUMS'
+        manifest.write_text(manifest.read_text().replace('libSubInspector.dylib', 'SubInspector.dll'))
+        for script, args in [('osx-sign.sh', []), ('osx-notarize.sh', [self.root / 'release.zip'])]:
+            with self.subTest(script=script):
+                result = self.run_tool(script, *args)
+                self.assertNotEqual(result.returncode, 0, result.stdout)
+                self.assertIn('Expected a macOS CI artifact', result.stdout)
+                self.assertNotIn('Unexpected notary call', result.stdout)
+
+    def simulate_notary(self):
+        self.sign()
+        # Only simulate Developer ID validation and Apple's service. ditto,
+        # checksum verification, plist parsing, and output handling remain real.
+        commands = self.commands
+        (commands / 'codesign').write_text('''#!/usr/bin/env python3
+import sys
+if '--verify' in sys.argv:
+    requirement = next(arg for arg in sys.argv if arg.startswith('-R='))
+    if 'certificate leaf[subject.OU] = "TESTTEAM01"' not in requirement:
+        sys.exit('Wrong signing team')
+else:
+    print('Timestamp=Sep 12, 2026')
+    print('CodeDirectory v=20500 flags=0x10000(runtime)')
+''')
+        (commands / 'xcrun').write_text('''#!/usr/bin/env python3
+import hashlib, os, pathlib, plistlib, sys, zipfile
+assert sys.argv[1] == 'notarytool'
+assert sys.argv[sys.argv.index('--keychain-profile') + 1] == 'test-profile'
+assert sys.argv[sys.argv.index('--keychain') + 1] == 'test keychain'
+if sys.argv[2] == 'log':
+    print('Notary service diagnostic')
+else:
+    assert sys.argv[2] == 'submit'
+    assert sys.argv[sys.argv.index('--timeout') + 1] == '1m'
+    archive = next(arg for arg in sys.argv if arg.endswith('.zip'))
+    with zipfile.ZipFile(archive) as package:
+        prefix = os.environ['TEST_PACKAGE_NAME'] + '/'
+        for line in package.read(prefix + 'SHA256SUMS').decode().splitlines():
+            digest, name = line.split('  ', 1)
+            assert digest == hashlib.sha256(package.read(prefix + name)).hexdigest()
+    if os.environ.get('TEST_CONCURRENT_OUTPUT'):
+        pathlib.Path(os.environ['TEST_CONCURRENT_OUTPUT']).write_text('Created during notarization')
+    plistlib.dump({'id': 'test-submission', 'status': os.environ['TEST_STATUS']}, sys.stdout.buffer)
+    sys.exit(int(os.environ['TEST_EXIT']))
+''')
+        for command in commands.iterdir():
+            command.chmod(0o755)
+        self.env.update(SUBINSPECTOR_NOTARY_KEYCHAIN='test keychain',
+                        SUBINSPECTOR_NOTARY_TIMEOUT='1m')
+
+    def test_notary_results(self):
+        self.simulate_notary()
+        for status, exit_code in [('Accepted', '0'), ('Invalid', '0'), ('In Progress', '1')]:
+            with self.subTest(status=status):
+                self.env.update(TEST_STATUS=status, TEST_EXIT=exit_code, TEST_PACKAGE_NAME=status)
+                output = self.root / f'{status}.zip'
+                result = self.run_tool('osx-notarize.sh', output)
+                accepted = status == 'Accepted'
+                self.assertEqual(result.returncode == 0, accepted, result.stdout)
+                self.assertEqual(output.exists(), accepted)
+                if accepted:
+                    original = output.read_bytes()
+                    self.assertNotEqual(self.run_tool('osx-notarize.sh', output).returncode, 0)
+                    self.assertEqual(original, output.read_bytes())
+                else:
+                    self.assertIn('Notary service diagnostic', result.stdout)
+
+    def test_wrong_team_is_rejected_before_submission(self):
+        self.simulate_notary()
+        self.env['SUBINSPECTOR_TEAM_ID'] = 'OTHERTEAM1'
+        result = self.run_tool('osx-notarize.sh', self.root / 'wrong-team.zip')
+        self.assertNotEqual(result.returncode, 0, result.stdout)
+        self.assertIn('Wrong signing team', result.stdout)
+        self.assertFalse((self.root / 'wrong-team.zip').exists())
+
+    def test_output_created_during_notarization_is_preserved(self):
+        self.simulate_notary()
+        output = self.root / 'concurrent.zip'
+        self.env.update(TEST_STATUS='Accepted', TEST_EXIT='0',
+                        TEST_PACKAGE_NAME='concurrent', TEST_CONCURRENT_OUTPUT=str(output))
+        result = self.run_tool('osx-notarize.sh', output)
+        self.assertNotEqual(result.returncode, 0, result.stdout)
+        self.assertIn('appeared during notarization', result.stdout)
+        self.assertEqual(output.read_text(), 'Created during notarization')
+
+
+unittest.main()
diff --git a/tools/osx-notarize.sh b/tools/osx-notarize.sh
new file mode 100755
index 0000000..e3e951b
--- /dev/null
+++ b/tools/osx-notarize.sh
@@ -0,0 +1,102 @@
+#!/bin/sh
+set -eu
+
+if test "$#" -ne 2; then
+  echo "Usage: $0 ARTIFACT_DIR OUTPUT_ZIP" >&2
+  exit 1
+fi
+if test -z "${SUBINSPECTOR_NOTARY_PROFILE:-}"; then
+  echo "Set SUBINSPECTOR_NOTARY_PROFILE to a notarytool Keychain profile" >&2
+  exit 1
+fi
+if ! printf '%s\n' "${SUBINSPECTOR_TEAM_ID:-}" | grep -Eq '^[A-Z0-9]{10}$'; then
+  echo "Set SUBINSPECTOR_TEAM_ID to Aegisub's 10-character signing Team ID" >&2
+  exit 1
+fi
+
+ARTIFACT_DIR=$(cd "$1" && pwd)
+OUTPUT_DIR=$(cd "$(dirname "$2")" && pwd)
+OUTPUT_ZIP="${OUTPUT_DIR}/$(basename "$2")"
+case "${OUTPUT_ZIP}" in
+  *.zip) ;;
+  *) echo "OUTPUT_ZIP must end in .zip" >&2; exit 1 ;;
+esac
+if test -e "${OUTPUT_ZIP}" || test -L "${OUTPUT_ZIP}"; then
+  echo "${OUTPUT_ZIP} already exists" >&2
+  exit 1
+fi
+
+WORK_DIR=$(mktemp -d "${TMPDIR:-/tmp}/subinspector-notary.XXXXXX")
+trap 'rm -rf "${WORK_DIR}"' EXIT
+trap 'exit 1' HUP INT TERM
+
+# Validate a private copy, then submit exactly those files.
+PACKAGE_DIR="${WORK_DIR}/$(basename "${OUTPUT_ZIP}" .zip)"
+ditto "${ARTIFACT_DIR}" "${PACKAGE_DIR}"
+(
+  cd "${PACKAGE_DIR}"
+  if ! grep -Eq '^[[:xdigit:]]{64}  libSubInspector[.]dylib$' SHA256SUMS; then
+    echo "Expected a macOS CI artifact with libSubInspector.dylib in SHA256SUMS" >&2
+    exit 1
+  fi
+  shasum -a 256 -c SHA256SUMS
+  codesign --verify --strict --verbose=2 \
+    -R="anchor apple generic and certificate leaf[field.1.2.840.113635.100.6.1.13] exists and certificate leaf[subject.OU] = \"${SUBINSPECTOR_TEAM_ID}\"" \
+    libSubInspector.dylib
+  SIGNATURE=$(codesign --display --verbose=4 libSubInspector.dylib 2>&1)
+  if ! printf '%s\n' "${SIGNATURE}" | grep -q '^Timestamp='; then
+    echo "The dylib has no secure signing timestamp" >&2
+    exit 1
+  fi
+  if ! printf '%s\n' "${SIGNATURE}" | grep -q '^CodeDirectory .*flags=.*runtime'; then
+    echo "The dylib was not signed with --options runtime" >&2
+    exit 1
+  fi
+)
+ARCHIVE="${WORK_DIR}/submission.zip"
+ditto -c -k --keepParent "${PACKAGE_DIR}" "${ARCHIVE}"
+
+run_notarytool() {
+  command=$1
+  shift
+  if test -n "${SUBINSPECTOR_NOTARY_KEYCHAIN:-}"; then
+    xcrun notarytool "${command}" --keychain-profile "${SUBINSPECTOR_NOTARY_PROFILE}" \
+      --keychain "${SUBINSPECTOR_NOTARY_KEYCHAIN}" "$@"
+  else
+    xcrun notarytool "${command}" --keychain-profile "${SUBINSPECTOR_NOTARY_PROFILE}" "$@"
+  fi
+}
+
+RESULT="${WORK_DIR}/result.plist"
+if run_notarytool submit "${ARCHIVE}" --wait \
+    --timeout "${SUBINSPECTOR_NOTARY_TIMEOUT:-30m}" --output-format plist > "${RESULT}"; then
+  SUBMIT_EXIT=0
+else
+  SUBMIT_EXIT=$?
+fi
+if test -s "${RESULT}"; then
+  plutil -p "${RESULT}" || cat "${RESULT}"
+fi
+SUBMISSION_ID=$(plutil -extract id raw -o - "${RESULT}" 2>/dev/null || true)
+STATUS=$(plutil -extract status raw -o - "${RESULT}" 2>/dev/null || true)
+if test "${SUBMIT_EXIT}" -ne 0 || test "${STATUS}" != Accepted; then
+  if test -n "${SUBMISSION_ID}"; then
+    run_notarytool log "${SUBMISSION_ID}" || true
+  fi
+  echo "Notarization failed with status ${STATUS:-unknown}" >&2
+  exit 1
+fi
+
+# Apple issues tickets for dylibs, but neither dylibs nor ZIPs support stapling.
+# The destination may have appeared while we waited for Apple.
+if test -e "${OUTPUT_ZIP}" || test -L "${OUTPUT_ZIP}"; then
+  echo "${OUTPUT_ZIP} appeared during notarization; leaving it untouched" >&2
+  exit 1
+fi
+mv -n "${ARCHIVE}" "${OUTPUT_ZIP}"
+if test -e "${ARCHIVE}"; then
+  echo "Could not publish ${OUTPUT_ZIP} without overwriting an existing file" >&2
+  exit 1
+fi
+shasum -a 256 "${OUTPUT_ZIP}"
+echo "Notarized ${OUTPUT_ZIP}"
diff --git a/tools/osx-sign.sh b/tools/osx-sign.sh
new file mode 100755
index 0000000..3297a67
--- /dev/null
+++ b/tools/osx-sign.sh
@@ -0,0 +1,44 @@
+#!/bin/sh
+set -eu
+
+if test "$#" -ne 1; then
+  echo "Usage: $0 ARTIFACT_DIR" >&2
+  exit 1
+fi
+if test -z "${SUBINSPECTOR_SIGNATURE:-}"; then
+  echo "Set SUBINSPECTOR_SIGNATURE to Aegisub's Developer ID identity (or '-' for an ad-hoc test)" >&2
+  exit 1
+fi
+
+cd "$1"
+LIBRARY=libSubInspector.dylib
+if ! grep -Eq '^[[:xdigit:]]{64}  libSubInspector[.]dylib$' SHA256SUMS; then
+  echo "Expected a macOS CI artifact with libSubInspector.dylib in SHA256SUMS" >&2
+  exit 1
+fi
+shasum -a 256 -c SHA256SUMS
+
+if test "${SUBINSPECTOR_SIGNATURE}" = '-'; then
+  codesign --force --sign - "${LIBRARY}"
+else
+  set -- --force --options runtime --timestamp --sign "${SUBINSPECTOR_SIGNATURE}"
+  if test -n "${SUBINSPECTOR_SIGNING_KEYCHAIN:-}"; then
+    set -- "$@" --keychain "${SUBINSPECTOR_SIGNING_KEYCHAIN}"
+  fi
+  codesign "$@" "${LIBRARY}"
+fi
+codesign --verify --strict --verbose=2 "${LIBRARY}"
+
+# Signing changes only the dylib. Preserve the checksums of the other files.
+CHECKSUMS=$(mktemp './.SHA256SUMS.XXXXXX')
+trap 'rm -f "${CHECKSUMS}"' EXIT
+trap 'exit 1' HUP INT TERM
+SIGNED_CHECKSUM=$(shasum -a 256 "${LIBRARY}")
+awk -v signed="${SIGNED_CHECKSUM}" '
+  $2 == "libSubInspector.dylib" { $0 = signed }
+  { print }
+' SHA256SUMS > "${CHECKSUMS}"
+chmod 644 "${CHECKSUMS}"
+mv -f "${CHECKSUMS}" SHA256SUMS
+shasum -a 256 -c SHA256SUMS
+echo "Signed ${LIBRARY} and updated SHA256SUMS"