diff --git a/notebooks/__init__.py b/notebooks/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/notebooks/pangenome_refseq.py b/notebooks/pangenome_refseq.py
new file mode 100644
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+++ b/notebooks/pangenome_refseq.py
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+"""
+Utility script to identify missing RefSeq assemblies relative to GTDB.
+
+This script:
+1. Reads a GTDB metastore table.
+2. Removes GB_/RS_ prefixes from genome_id.
+3. Downloads the latest RefSeq assembly summary.
+4. Computes missing GCF assemblies.
+5. Outputs two text files using Spark distributed write:
+   - r214_assemblies
+   - missing_refseq_ids
+"""
+
+from __future__ import annotations
+
+import logging
+import tempfile
+import urllib.request
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+import click
+from pyspark.sql.functions import regexp_replace
+
+from berdl_notebook_utils.setup_spark_session import get_spark_session
+
+if TYPE_CHECKING:
+    from pyspark.sql import SparkSession
+
+logger = logging.getLogger(__name__)
+
+REFSEQ_URL = "https://ftp.ncbi.nlm.nih.gov/genomes/refseq/assembly_summary_refseq.txt"
+
+
+def download_refseq_summary(output_path: Path) -> Path:
+    """
+    Download RefSeq assembly summary file.
+    """
+    logger.info("Downloading RefSeq assembly summary from %s", REFSEQ_URL)
+    urllib.request.urlretrieve(REFSEQ_URL, output_path)  # noqa: S310
+    return output_path
+
+
+def parse_refseq_gcf_ids(file_path: Path) -> list[str]:
+    """
+    Parse all GCF_ assembly accessions from the RefSeq summary file.
+    """
+    assembly_ids: list[str] = []
+
+    with file_path.open(encoding="utf-8") as file:
+        for line in file:
+            if line.startswith("#"):
+                continue
+
+            accession = line.split("\t", 1)[0]
+            if accession.startswith("GCF_"):
+                assembly_ids.append(accession)
+
+    return assembly_ids
+
+
+@click.command()
+@click.option(
+    "--gtdb-table",
+    required=True,
+    help="Metastore table containing genome_id column",
+)
+@click.option(
+    "--output-dir",
+    required=True,
+    help="Output directory (e.g. s3a://...) where text files will be written",
+)
+def main(gtdb_table: str, output_dir: str) -> None:
+    """
+    Run the missing RefSeq assembly detection pipeline.
+    """
+    logging.basicConfig(level=logging.INFO)
+
+    spark: SparkSession = get_spark_session()
+
+    # ------------------------------------------------------------------
+    # 1. Read GTDB genome table
+    # ------------------------------------------------------------------
+    r214_df = spark.table(gtdb_table).select("genome_id").distinct()
+
+    rm_prefix_df = (
+        r214_df.withColumn(
+            "assembly_id",
+            regexp_replace("genome_id", r"^(GB_|RS_)", ""),
+        )
+        .select("assembly_id")
+        .distinct()
+    )
+
+    logger.info("GTDB assemblies: %d", rm_prefix_df.count())
+
+    # ------------------------------------------------------------------
+    # 2. Download RefSeq summary securely
+    # ------------------------------------------------------------------
+    with tempfile.NamedTemporaryFile(delete=False) as tmp:
+        summary_path = Path(tmp.name)
+
+    download_refseq_summary(summary_path)
+
+    # ------------------------------------------------------------------
+    # 3. Parse RefSeq GCF IDs
+    # ------------------------------------------------------------------
+    refseq_ids = parse_refseq_gcf_ids(summary_path)
+
+    refseq_df = spark.createDataFrame(
+        [(x,) for x in refseq_ids],
+        ["assembly_id"],
+    )
+
+    logger.info("RefSeq assemblies: %d", refseq_df.count())
+
+    # ------------------------------------------------------------------
+    # 4. Compute missing assemblies
+    # ------------------------------------------------------------------
+    missing_df = refseq_df.join(
+        rm_prefix_df,
+        on="assembly_id",
+        how="left_anti",
+    )
+
+    logger.info("Missing RefSeq assemblies: %d", missing_df.count())
+
+    # ------------------------------------------------------------------
+    # 5. Distributed Spark text output
+    # ------------------------------------------------------------------
+
+    # Output 1: All GTDB assemblies
+    rm_prefix_df.select("assembly_id").orderBy("assembly_id").coalesce(1).write.mode("overwrite").text(
+        f"{output_dir}/r214_assemblies"
+    )
+
+    # Output 2: Missing RefSeq assemblies
+    missing_df.select("assembly_id").orderBy("assembly_id").coalesce(1).write.mode("overwrite").text(
+        f"{output_dir}/missing_refseq_ids"
+    )
+
+    logger.info("Output files successfully written to %s", output_dir)
+
+
+if __name__ == "__main__":
+    main()