diff --git a/tools/check-cherry-picks.py b/tools/check-cherry-picks.py
new file mode 100755
index 0000000..adf763c
--- /dev/null
+++ b/tools/check-cherry-picks.py
@@ -0,0 +1,184 @@
+#!/usr/bin/env python3
+# Copyright (c) 2023, the R8 project authors. Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import subprocess
+import sys
+import re
+import r8_release
+
+class Branch:
+  def __init__(self, name, first, last=None):
+    self.name = name
+    self.first = first
+    self.last = last # optional last for testing purposes.
+
+  def origin(self):
+    return "origin/%s" % self.name
+
+  def last_or_origin(self):
+    return self.last if self.last else self.origin()
+
+  def __str__(self):
+    return self.name
+
+# The initial commit is the furthest back we need to search on main.
+# Currently, it is the merge point of main onto 4.0.23-dev
+MAIN = Branch('main', 'a2e203580aa00a36f85cd68d3d584b97aef34d59')
+OLDEST_BRANCH_VERSION = (4, 0)
+DEV_BRANCH_VERSION = [int(s) for s in r8_release.R8_DEV_BRANCH.split('.')]
+
+# List of change ids that should not be reported.
+IGNORED = [
+    'I92d7bf3afbf609fdea21683941cfd15c90305cf2'
+]
+
+VERBOSE = False
+
+# Helper to call and decode a shell command.
+def run_cmd(cmd):
+  if VERBOSE:
+    print(' '.join(cmd))
+  return subprocess.check_output(cmd).decode('UTF-8')
+
+# Comparator on major and minor branch versions.
+def branch_version_less_than(b1, b2):
+  if b1[0] < b2[0]:
+    return True
+  if b1[0] == b2[0] and b1[1] < b2[1]:
+    return True
+  return False
+
+# Find all release branches between OLDEST_BRANCH and DEV_BRANCH
+def get_release_branches():
+  # Release branches are assumed to be of the form 'origin/X.Y'
+  out = run_cmd(['git', 'branch', '-r', '-l'])
+  pattern = re.compile('origin/(\d+).(\d+)')
+  releases = []
+  for line in out.split('\n'):
+    m = pattern.search(line.strip())
+    if m:
+      major = m.group(1)
+      minor = m.group(2)
+      if major and minor:
+        candidate = (int(major), int(minor))
+        if branch_version_less_than(candidate, OLDEST_BRANCH_VERSION):
+          continue
+        if branch_version_less_than(candidate, DEV_BRANCH_VERSION):
+          releases.extend(find_dev_cutoff(candidate))
+  return releases
+
+# Find the most recent commit hash that is for a -dev version.
+# This is the starting point for the map of commits after cutoff from main.
+def find_dev_cutoff(branch_version):
+  out = run_cmd([
+      'git',
+      'log',
+      'origin/%d.%d' % branch_version,
+      '--grep', 'Version .*-dev',
+      '--pretty=oneline',
+  ])
+  # Format of output is: <hash> Version <version>-dev
+  try:
+    hash = out[0:out.index(' ')]
+    return [Branch('%d.%d' % branch_version, hash)]
+  except ValueError:
+    throw_error("Failed to find dev cutoff for branch %d.%d" % branch_version)
+
+# Build a map from each "Change-Id" hash to the hash of its commit.
+def get_change_id_map(branch):
+  out = run_cmd([
+      'git',
+      'log',
+      '%s..%s' % (branch.first, branch.last_or_origin())
+  ])
+  map = {}
+  current_commit = None
+  for line in out.split('\n'):
+    if line.startswith('commit '):
+      current_commit = line[len('commit '):]
+      assert len(current_commit) == 40
+    elif line.strip().startswith('Change-Id: '):
+      change_id = line.strip()[len('Change-Id: '):]
+      assert len(change_id) == 41
+      map[change_id] = current_commit
+  return map
+
+# Check if a specific commit is present on a specific branch.
+def is_commit_in(commit, branch):
+  out = run_cmd(['git', 'branch', '-r', branch.origin(), '--contains', commit])
+  return out.strip() == branch.origin()
+
+def main():
+  found_errors = False
+  # The main map is all commits back to the "init" point.
+  main_map = get_change_id_map(MAIN)
+  # Compute the release branches.
+  release_branches = get_release_branches()
+  # Populate the release maps with all commits after the last -dev point.
+  release_maps = {}
+  for branch in release_branches:
+    release_maps[branch.name] = get_change_id_map(branch)
+  # Each branch is then compared forwards with each subsequent branch.
+  for i in range(len(release_branches)):
+    branch = release_branches[i]
+    newer_branches = release_branches[i+1:]
+    if (len(newer_branches) == 0):
+      print('Last non-dev release branch is %s, nothing to check.' % branch)
+      continue
+    print('Checking branch %s.' % branch)
+    changes = release_maps[branch.name]
+    cherry_picks_count = 0
+    for change in changes.keys():
+      is_cherry_pick = False
+      missing_from = None
+      commit_on_main = main_map.get(change)
+      for newer_branch in newer_branches:
+        if change in release_maps[newer_branch.name]:
+          is_cherry_pick = True
+          # If the change is in the release mappings check for holes.
+          if missing_from:
+            found_errors = change_error(
+                change,
+                'Error: missing Change-Id %s on branch %s. '
+                'Is present on %s and again on %s.' % (
+                    change, missing_from, branch, newer_branch,
+                ))
+        elif commit_on_main:
+          is_cherry_pick = True
+          # The change is not in the non-dev part of the branch, so we need to
+          # check that the fork from main included the change.
+          if not is_commit_in(commit_on_main, newer_branch):
+            found_errors = change_error(
+                change,
+                'Error: missing Change-Id %s on branch %s. '
+                'Is present on %s and on main as commit %s.' % (
+                    change, newer_branch, branch, commit_on_main
+                ))
+        else:
+          # The change is not on "main" so we just record for holes on releases.
+          missing_from = newer_branch
+      if is_cherry_pick:
+        cherry_picks_count += 1
+    print('Found %d cherry-picks (out of %d commits).' % (
+        cherry_picks_count, len(changes)))
+
+  if found_errors:
+    return 1
+  return 0
+
+def change_error(change, msg):
+  if change in IGNORED:
+    return False
+  error(msg)
+  return True
+
+def throw_error(msg):
+  raise ValueError(msg)
+
+def error(msg):
+  print(msg, file=sys.stderr)
+
+if __name__ == '__main__':
+  sys.exit(main())