diff --git a/datasets/add_months.sh b/datasets/add_months.sh
index fff2f72..0065d24 100755
--- a/datasets/add_months.sh
+++ b/datasets/add_months.sh
@@ -1,8 +1,9 @@
 #!/usr/bin/env bash
 #
 # Add one or more new months to the existing parquet datasets using a
-# layered append. The live datasets are never touched until the final
-# copy step, so they remain safe and queryable throughout.
+# layered append. Designed to run on a single fat node (e.g. cpu-g2 with
+# 128 cores / ~1TB RAM). For a multi-node Spark cluster instead, see
+# add_months_multinode.sh.
 #
 # Usage:
 #   add_months.sh YYYY-MM [YYYY-MM ...]
@@ -22,18 +23,16 @@
 #   ./add_months.sh 2025-01 2025-02
 #
 # Workflow:
-#   Part 1  — parse new .zst files into per-month parquets (compute node)
-#   Part 2  — sort into staging directories, not the live datasets (fat node)
-#   Verify  — inspect staging before committing (manual step, not scripted)
+#   Part 1  — parse new .zst files into per-month parquets (parallel)
+#   Part 2  — sort into staging directories, not the live datasets (Spark)
+#   [script exits here — verify staging before continuing]
 #   Copy    — move staging files into live datasets (run manually after verify)
 #   Cleanup — remove temp and staging dirs (run manually after copy)
 #
-# Every command below is independently runnable for debugging. The copy
-# and cleanup steps are intentionally left as separate commands so you can
-# verify the staging output before touching the live datasets.
-#
 # NOTE: This script and its workflow are written but not yet tested.
 # Remove this notice after a successful end-to-end run.
+#
+# Every command below is independently runnable for debugging.
 
 set -e
 cd "$(dirname "$0")"
@@ -62,7 +61,7 @@ LIVE_COMMENTS_AUTH="/gscratch/comdata/output/reddit_comments_by_author.parquet"
 LIVE_SUBMISSIONS_SUB="/gscratch/comdata/output/reddit_submissions_by_subreddit.parquet"
 LIVE_SUBMISSIONS_AUTH="/gscratch/comdata/output/reddit_submissions_by_author.parquet"
 
-# --- Part 1: parse new months in parallel (run on a compute node) -----------
+# --- Part 1: parse new months in parallel -----------------------------------
 
 printf "python3 comments_part1.py parse_dump RC_%s.zst --dumpdir=\"$COMMENTS_DUMPDIR\" --outdir=\"$TEMP_COMMENTS\"\n" "$@" \
     > add_months_comments_tasks.txt
@@ -76,26 +75,30 @@ parallel --joblog add_months_comments_joblog.txt --results add_months_comments_l
 parallel --joblog add_months_submissions_joblog.txt --results add_months_submissions_logs \
     < add_months_submissions_tasks.txt
 
-# --- Part 2: sort new months into staging (not the live datasets) -----------
-#
-# start_spark_and_run.sh calls salloc — run from a login node, or replace
-# with start_spark_cluster.sh + spark-submit if already on a suitable node.
+# --- Part 2: sort new months into staging (Spark, single fat node) ----------
 
-start_spark_and_run.sh 1 comments_part2.py \
+source "$SPARK_CONF_DIR/spark-env.sh"
+start_spark_cluster.sh
+
+spark-submit --master "spark://$(hostname):$SPARK_MASTER_PORT" \
+    comments_part2.py \
     --indir="$TEMP_COMMENTS" \
     --out_by_subreddit="$STAGING_COMMENTS_SUB" \
     --out_by_author="$STAGING_COMMENTS_AUTH"
 
-start_spark_and_run.sh 1 submissions_part2.py \
+spark-submit --master "spark://$(hostname):$SPARK_MASTER_PORT" \
+    submissions_part2.py \
     --indir="$TEMP_SUBMISSIONS" \
     --out_by_subreddit="$STAGING_SUBMISSIONS_SUB" \
     --out_by_author="$STAGING_SUBMISSIONS_AUTH"
 
+stop-all.sh
+
 # --- Verify: inspect staging before copying to live -------------------------
 #
-# The script stops here (exit 0 below). Check the staging output looks right
-# before running the copy step manually. The live datasets are untouched at
-# this point. Example checks:
+# The script stops here. Check the staging output looks right before running
+# the copy step manually. The live datasets are untouched at this point.
+# Example checks:
 #
 #   ls -lah "$STAGING_COMMENTS_SUB" | head
 #   python3 -c "
diff --git a/datasets/add_months_multinode.sh b/datasets/add_months_multinode.sh
new file mode 100755
index 0000000..e16b373
--- /dev/null
+++ b/datasets/add_months_multinode.sh
@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+#
+# Multi-node variant of add_months.sh. Uses start_spark_and_run.sh to
+# allocate a Spark cluster across multiple nodes via salloc. Run this
+# from a login node.
+#
+# For the common single-fat-node case, use add_months.sh instead.
+#
+# Usage:
+#   add_months_multinode.sh NODES YYYY-MM [YYYY-MM ...]
+#
+# Example (2 nodes, 3 months):
+#   add_months_multinode.sh 2 2025-01 2025-02 2025-03
+#
+# Override dump directories via environment variables if needed:
+#
+#   COMMENTS_DUMPDIR=/path/to/new/comments \
+#   SUBMISSIONS_DUMPDIR=/path/to/new/submissions \
+#   ./add_months_multinode.sh 2 2025-01 2025-02
+#
+# NOTE: This script and its workflow are written but not yet tested.
+# Remove this notice after a successful end-to-end run.
+
+set -e
+cd "$(dirname "$0")"
+
+NODES="${1:-}"
+if [ -z "$NODES" ] || [ $# -lt 2 ]; then
+    echo "Usage: $0 NODES YYYY-MM [YYYY-MM ...]" >&2
+    exit 1
+fi
+shift
+MONTHS=("$@")
+
+COMMENTS_DUMPDIR="${COMMENTS_DUMPDIR:-/gscratch/comdata/raw_data/reddit_dumps/comments}"
+SUBMISSIONS_DUMPDIR="${SUBMISSIONS_DUMPDIR:-/gscratch/comdata/raw_data/reddit_dumps/submissions}"
+
+TEMP_COMMENTS="/gscratch/comdata/output/temp/add_months_comments.parquet"
+TEMP_SUBMISSIONS="/gscratch/comdata/output/temp/add_months_submissions.parquet"
+STAGING_COMMENTS_SUB="/gscratch/comdata/output/temp/new_layer_comments_by_subreddit.parquet"
+STAGING_COMMENTS_AUTH="/gscratch/comdata/output/temp/new_layer_comments_by_author.parquet"
+STAGING_SUBMISSIONS_SUB="/gscratch/comdata/output/temp/new_layer_submissions_by_subreddit.parquet"
+STAGING_SUBMISSIONS_AUTH="/gscratch/comdata/output/temp/new_layer_submissions_by_author.parquet"
+LIVE_COMMENTS_SUB="/gscratch/comdata/output/reddit_comments_by_subreddit.parquet"
+LIVE_COMMENTS_AUTH="/gscratch/comdata/output/reddit_comments_by_author.parquet"
+LIVE_SUBMISSIONS_SUB="/gscratch/comdata/output/reddit_submissions_by_subreddit.parquet"
+LIVE_SUBMISSIONS_AUTH="/gscratch/comdata/output/reddit_submissions_by_author.parquet"
+
+# --- Part 1: parse new months in parallel -----------------------------------
+
+printf "python3 comments_part1.py parse_dump RC_%s.zst --dumpdir=\"$COMMENTS_DUMPDIR\" --outdir=\"$TEMP_COMMENTS\"\n" "${MONTHS[@]}" \
+    > add_months_comments_tasks.txt
+
+printf "python3 submissions_part1.py parse_dump RS_%s.zst --dumpdir=\"$SUBMISSIONS_DUMPDIR\" --outdir=\"$TEMP_SUBMISSIONS\"\n" "${MONTHS[@]}" \
+    > add_months_submissions_tasks.txt
+
+parallel --joblog add_months_comments_joblog.txt --results add_months_comments_logs \
+    < add_months_comments_tasks.txt
+
+parallel --joblog add_months_submissions_joblog.txt --results add_months_submissions_logs \
+    < add_months_submissions_tasks.txt
+
+# --- Part 2: sort new months into staging (multi-node Spark cluster) --------
+
+start_spark_and_run.sh "$NODES" comments_part2.py \
+    --indir="$TEMP_COMMENTS" \
+    --out_by_subreddit="$STAGING_COMMENTS_SUB" \
+    --out_by_author="$STAGING_COMMENTS_AUTH"
+
+start_spark_and_run.sh "$NODES" submissions_part2.py \
+    --indir="$TEMP_SUBMISSIONS" \
+    --out_by_subreddit="$STAGING_SUBMISSIONS_SUB" \
+    --out_by_author="$STAGING_SUBMISSIONS_AUTH"
+
+# --- Verify staging, then copy and cleanup manually -------------------------
+#
+# See add_months.sh for verify/copy/cleanup commands — they are identical.
+
+exit 0
+
+find "$STAGING_COMMENTS_SUB"  -maxdepth 1 -type f -exec cp {} "$LIVE_COMMENTS_SUB"/  \;
+find "$STAGING_COMMENTS_AUTH" -maxdepth 1 -type f -exec cp {} "$LIVE_COMMENTS_AUTH"/ \;
+find "$STAGING_SUBMISSIONS_SUB"  -maxdepth 1 -type f -exec cp {} "$LIVE_SUBMISSIONS_SUB"/  \;
+find "$STAGING_SUBMISSIONS_AUTH" -maxdepth 1 -type f -exec cp {} "$LIVE_SUBMISSIONS_AUTH"/ \;
+
+rm -rf "$TEMP_COMMENTS" "$TEMP_SUBMISSIONS"
+rm -rf "$STAGING_COMMENTS_SUB" "$STAGING_COMMENTS_AUTH"
+rm -rf "$STAGING_SUBMISSIONS_SUB" "$STAGING_SUBMISSIONS_AUTH"