diff --git a/test/0dt/mzcompose.py b/test/0dt/mzcompose.py
index 52acaada2ec9b..8547bf0ebb613 100644
--- a/test/0dt/mzcompose.py
+++ b/test/0dt/mzcompose.py
@@ -1388,3 +1388,137 @@ def get_correction_metrics():
         raise AssertionError(
             f"unexpected correction metrics: {insertions=}, {deletions=}"
         )
+
+
+def workflow_upsert_sources(c: Composition) -> None:
+    c.down(destroy_volumes=True)
+    c.up("zookeeper", "kafka", "schema-registry", "postgres", "mysql", "mz_old")
+    c.up("testdrive", persistent=True)
+
+    c.sql(
+        """
+        DROP CLUSTER IF EXISTS cluster CASCADE;
+        CREATE CLUSTER cluster SIZE '2-1';
+        GRANT ALL ON CLUSTER cluster TO materialize;
+        ALTER SYSTEM SET cluster = cluster;
+        ALTER SYSTEM SET max_sources = 100000;
+    """,
+        service="mz_old",
+        port=6877,
+        user="mz_system",
+    )
+
+    c.testdrive(
+        dedent(
+            """
+        > SET CLUSTER = cluster;
+        > CREATE TABLE t (a int, b int);
+
+        > CREATE CONNECTION IF NOT EXISTS kafka_conn FOR KAFKA BROKER '${testdrive.kafka-addr}', SECURITY PROTOCOL = 'PLAINTEXT';
+        > CREATE CONNECTION IF NOT EXISTS csr_conn FOR CONFLUENT SCHEMA REGISTRY URL '${testdrive.schema-registry-url}';
+            """
+        )
+    )
+
+    i = 1
+    mz1 = "mz_old"
+    mz2 = "mz_new"
+    while True:
+        with c.override(
+            Materialized(
+                name=mz2,
+                sanity_restart=False,
+                deploy_generation=i,
+                system_parameter_defaults=SYSTEM_PARAMETER_DEFAULTS,
+                restart="on-failure",
+                external_metadata_store=True,
+            ),
+            Testdrive(
+                materialize_url=f"postgres://materialize@{mz1}:6875",
+                materialize_url_internal=f"postgres://materialize@{mz1}:6877",
+                mz_service=mz1,
+                materialize_params={"cluster": "cluster"},
+                no_reset=True,
+                seed=1,
+                default_timeout=DEFAULT_TIMEOUT,
+            ),
+        ):
+            c.up(mz2)
+
+            c.testdrive(
+                dedent(
+                    f"""
+                $ kafka-create-topic topic=kafka{i}
+                $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{i}
+                key1A,key1B:value1A,value1B
+                > CREATE SOURCE kafka_source{i}
+                  IN CLUSTER cluster
+                  FROM KAFKA CONNECTION kafka_conn (TOPIC 'testdrive-kafka{i}-${{testdrive.seed}}');
+                > CREATE TABLE kafka_source_tbl{i} (key1, key2, value1, value2)
+                  FROM SOURCE kafka_source{i} (REFERENCE "testdrive-kafka{i}-${{testdrive.seed}}")
+                  KEY FORMAT CSV WITH 2 COLUMNS DELIMITED BY ','
+                  VALUE FORMAT CSV WITH 2 COLUMNS DELIMITED BY ','
+                  ENVELOPE UPSERT;
+
+                > CREATE MATERIALIZED VIEW mv{i} AS SELECT * FROM kafka_source_tbl{i}
+                """
+                )
+            )
+
+            for j in range(1, i + 1):
+                c.testdrive(
+                    dedent(
+                        f"""
+                    $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{j}
+                    key{i}A,key{i}B:value2A,value2B
+                    $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{j}
+                    key3A,key3B:value{i}A,value3B
+
+                    > SELECT count(*) > 0 FROM kafka_source_tbl{j}
+                    true
+
+                    > SELECT count(*) > 0 FROM mv{i}
+                    true
+                    """
+                    )
+                )
+
+            c.await_mz_deployment_status(DeploymentStatus.READY_TO_PROMOTE, mz2)
+
+            with c.override(
+                Testdrive(
+                    materialize_url=f"postgres://materialize@{mz2}:6875",
+                    materialize_url_internal=f"postgres://materialize@{mz2}:6877",
+                    mz_service=mz2,
+                    materialize_params={"cluster": "cluster"},
+                    no_reset=True,
+                    seed=1,
+                    default_timeout=DEFAULT_TIMEOUT,
+                ),
+            ):
+                for j in range(1, i + 1):
+                    c.testdrive(
+                        dedent(
+                            f"""
+                        $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{j}
+                        key4A,key4B:value4A,value4B
+
+                        $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{j}
+                        key2A,key2B:value5A,value5B
+                        $ kafka-ingest format=bytes key-format=bytes key-terminator=: topic=kafka{j}
+                        key3A,key3B:value6A,value6B
+
+                        > SELECT count(*) > 0 FROM kafka_source_tbl{j}
+                        true
+
+                        > SELECT count(*) > 0 FROM mv{j}
+                        true
+                        """
+                        )
+                    )
+
+            c.promote_mz(mz2)
+            c.await_mz_deployment_status(DeploymentStatus.IS_LEADER, mz2)
+
+        mz1, mz2 = mz2, mz1
+        i += 1