diff --git a/.github/workflows/sync-cloud-run-env.yml b/.github/workflows/sync-cloud-run-env.yml
index 3f96da9..e7adf5c 100644
--- a/.github/workflows/sync-cloud-run-env.yml
+++ b/.github/workflows/sync-cloud-run-env.yml
@@ -314,6 +314,14 @@ jobs:
             --region="${CLOUD_RUN_REGION}" \
             --service="${CLOUD_RUN_SERVICE}"
 
+      - name: Verify production strategy dependency continuity before build
+        if: steps.deploy_config.outputs.enabled == 'true'
+        run: |
+          set -euo pipefail
+          python scripts/verify_production_ues_continuity.py \
+            --project="${GCP_PROJECT_ID}" \
+            --region="${CLOUD_RUN_REGION}" \
+            --service="${CLOUD_RUN_SERVICE}"
 
       - name: Build, push, and deploy Cloud Run image
         id: deploy_image
diff --git a/scripts/verify_production_ues_continuity.py b/scripts/verify_production_ues_continuity.py
new file mode 100644
index 0000000..7ff1d6a
--- /dev/null
+++ b/scripts/verify_production_ues_continuity.py
@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+"""Reject an unapproved UES dependency change before building a live image.
+
+The currently serving revision is the continuity baseline. This does not
+approve a new strategy release; such a change needs a separate release path.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import re
+import subprocess
+import sys
+import tomllib
+from collections.abc import Mapping
+from pathlib import Path
+
+
+UES = "us-equity-strategies"
+SHA = re.compile(r"^[0-9a-f]{40}$")
+
+
+class ContinuityError(ValueError):
+    pass
+
+
+def _run(*args: str) -> str:
+    result = subprocess.run(args, text=True, capture_output=True, check=False)
+    if result.returncode:
+        raise ContinuityError(f"Unable to read production baseline ({args[0]} failed)")
+    return result.stdout
+
+
+def _ues_lock_revision(data: str) -> str:
+    packages = tomllib.loads(data).get("package", [])
+    matches = [package for package in packages if package.get("name") == UES]
+    if len(matches) != 1:
+        raise ContinuityError("Exactly one locked UES package is required")
+    source = matches[0].get("source") or {}
+    match = re.search(r"[?&]rev=([0-9a-f]{40})#([0-9a-f]{40})$", str(source.get("git") or ""))
+    if not match or match.group(1) != match.group(2):
+        raise ContinuityError("Locked UES package needs an immutable full revision")
+    return match.group(1)
+
+
+def _ues_project_revision(data: str) -> str:
+    dependencies = tomllib.loads(data).get("project", {}).get("dependencies", [])
+    matches = [item for item in dependencies if item.lower().startswith(f"{UES} @ ")]
+    if len(matches) != 1:
+        raise ContinuityError("Exactly one direct UES dependency is required")
+    revision = matches[0].rsplit("@", 1)[-1]
+    if not SHA.fullmatch(revision):
+        raise ContinuityError("Direct UES dependency needs an immutable full revision")
+    return revision
+
+
+def _active_commit(service: str, project: str, region: str) -> str:
+    service_json = json.loads(
+        _run(
+            "gcloud", "run", "services", "describe", service,
+            f"--project={project}", f"--region={region}", "--format=json",
+        )
+    )
+    traffic = service_json.get("status", {}).get("traffic") or []
+    active = [
+        item for item in traffic
+        if isinstance(item, Mapping) and int(item.get("percent") or 0) > 0
+    ]
+    if len(active) != 1 or int(active[0]["percent"]) != 100:
+        raise ContinuityError("A single 100% serving revision is required")
+    revision = str(active[0].get("revisionName") or "")
+    if not revision:
+        raise ContinuityError("Serving revision name is missing")
+    revision_json = json.loads(
+        _run(
+            "gcloud", "run", "revisions", "describe", revision,
+            f"--project={project}", f"--region={region}", "--format=json",
+        )
+    )
+    commit = str(revision_json.get("metadata", {}).get("labels", {}).get("commit-sha") or "")
+    if not SHA.fullmatch(commit):
+        raise ContinuityError("Serving revision has no full commit-sha label")
+    return commit
+
+
+def verify(service: str, project: str, region: str) -> None:
+    active_commit = _active_commit(service, project, region)
+    candidate_lock = _ues_lock_revision(Path("uv.lock").read_text(encoding="utf-8"))
+    candidate_project = _ues_project_revision(Path("pyproject.toml").read_text(encoding="utf-8"))
+    candidate_qsl = tomllib.loads(Path("qsl.toml").read_text(encoding="utf-8")).get("qsl", {}).get("requires", {}).get("us_equity_strategies")
+    if candidate_lock != candidate_project or candidate_qsl != candidate_lock:
+        raise ContinuityError("Candidate UES lock, direct dependency, and QSL contract disagree")
+    _run("git", "fetch", "--no-tags", "--depth=1", "origin", active_commit)
+    active_lock = _ues_lock_revision(_run("git", "show", f"{active_commit}:uv.lock"))
+    active_project = _ues_project_revision(_run("git", "show", f"{active_commit}:pyproject.toml"))
+    active_qsl = tomllib.loads(_run("git", "show", f"{active_commit}:qsl.toml")).get("qsl", {}).get("requires", {}).get("us_equity_strategies")
+    if active_lock != active_project or active_qsl != active_lock:
+        raise ContinuityError("Serving revision UES lock, direct dependency, and QSL contract disagree")
+    if candidate_lock != active_lock:
+        raise ContinuityError("Candidate UES revision differs from the serving production revision")
+    print("Verified production UES dependency continuity")
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--service", required=True)
+    parser.add_argument("--project", required=True)
+    parser.add_argument("--region", required=True)
+    args = parser.parse_args()
+    try:
+        verify(args.service, args.project, args.region)
+    except (ContinuityError, OSError, ValueError, KeyError) as exc:
+        print(f"Production UES continuity check failed: {exc}", file=sys.stderr)
+        return 1
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())