diff --git a/src/core/ddsc/src/dds_write.c b/src/core/ddsc/src/dds_write.c
index cc0b1e8..5d7539c 100644
--- a/src/core/ddsc/src/dds_write.c
+++ b/src/core/ddsc/src/dds_write.c
@@ -96,37 +96,21 @@ struct local_sourceinfo {
 static struct ddsi_serdata *local_make_sample (struct ddsi_tkmap_instance **tk, struct ddsi_domaingv *gv, struct ddsi_sertopic const * const topic, void *vsourceinfo)
 {
   struct local_sourceinfo *si = vsourceinfo;
-  if (topic == si->src_topic)
+  struct ddsi_serdata *d = ddsi_serdata_ref_as_topic (topic, si->src_payload);
+  if (d == NULL)
   {
-    *tk = si->src_tk;
-    /* FIXME: see if this pair of refc increments can't be avoided
-       They're needed because free_sample_after_delivery will always be called, but
-       in the common case of a local writer and a single sertopic, make_sample doesn't
-       actually create a sample, and so free_sample_after_delivery doesn't actually
-       have to free anything */
-    ddsi_tkmap_instance_ref (si->src_tk);
-    return ddsi_serdata_ref (si->src_payload);
+    DDS_CWARNING (&gv->logconfig, "local: deserialization %s/%s failed in topic type conversion\n", topic->name, topic->type_name);
+    return NULL;
   }
+  if (topic != si->src_topic)
+    *tk = ddsi_tkmap_lookup_instance_ref (gv->m_tkmap, d);
   else
   {
-    /* ouch ... convert a serdata from one sertopic to another ... */
-    ddsrt_iovec_t iov;
-    uint32_t size = ddsi_serdata_size (si->src_payload);
-    (void) ddsi_serdata_to_ser_ref (si->src_payload, 0, size, &iov);
-    struct ddsi_serdata *d = ddsi_serdata_from_ser_iov (topic, si->src_payload->kind, 1, &iov, size);
-    ddsi_serdata_to_ser_unref (si->src_payload, &iov);
-    if (d)
-    {
-      d->statusinfo = si->src_payload->statusinfo;
-      d->timestamp = si->src_payload->timestamp;
-      *tk = ddsi_tkmap_lookup_instance_ref (gv->m_tkmap, d);
-    }
-    else
-    {
-      DDS_CWARNING (&gv->logconfig, "local: deserialization %s/%s failed in topic type conversion\n", topic->name, topic->type_name);
-    }
-    return d;
+    // if the topic is the same, we can avoid the lookup
+    ddsi_tkmap_instance_ref (si->src_tk);
+    *tk = si->src_tk;
   }
+  return d;
 }
 
 static dds_return_t local_on_delivery_failure_fastpath (struct entity_common *source_entity, bool source_entity_locked, struct local_reader_ary *fastpath_rdary, void *vsourceinfo)
diff --git a/src/core/ddsc/tests/multi_sertopic.c b/src/core/ddsc/tests/multi_sertopic.c
index f66b89b..31518ed 100644
--- a/src/core/ddsc/tests/multi_sertopic.c
+++ b/src/core/ddsc/tests/multi_sertopic.c
@@ -328,7 +328,48 @@ static void logsink (void *arg, const dds_log_data_t *msg)
     ddsrt_atomic_inc32 (deser_fail);
 }
 
-static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub, bool fastpath)
+enum multi_sertopic_mode {
+  MSM_FASTPATH,
+  MSM_SLOWPATH,
+  MSM_TRANSLOCAL
+};
+
+static const char *multi_sertopic_modestr (enum multi_sertopic_mode mode)
+{
+  switch (mode)
+  {
+    case MSM_FASTPATH: return "fastpath";
+    case MSM_SLOWPATH: return "slowpath";
+    case MSM_TRANSLOCAL: return "transient-local";
+  }
+  return "?";
+}
+
+static void create_readers (dds_entity_t pp_sub, size_t nrds, dds_entity_t *rds, size_t ntps, const dds_entity_t *tps, const dds_qos_t *qos, dds_entity_t waitset)
+{
+  assert (nrds >= ntps && (nrds % ntps) == 0);
+  for (size_t i = 0; i < ntps; i++)
+  {
+    rds[i] = dds_create_reader (pp_sub, tps[i], qos, NULL);
+    CU_ASSERT_FATAL (rds[i] > 0);
+  }
+  for (size_t i = ntps; i < nrds; i++)
+  {
+    rds[i] = dds_create_reader (pp_sub, tps[(i - ntps) / (nrds / ntps - 1)], qos, NULL);
+    CU_ASSERT_FATAL (rds[i] > 0);
+  }
+
+  for (size_t i = 0; i < nrds; i++)
+  {
+    dds_return_t rc;
+    rc = dds_set_status_mask (rds[i], DDS_SUBSCRIPTION_MATCHED_STATUS | DDS_DATA_AVAILABLE_STATUS);
+    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
+    rc = dds_waitset_attach (waitset, rds[i], (dds_attach_t)i);
+    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
+  }
+}
+
+static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub, enum multi_sertopic_mode mode)
 {
 #define SEQ_IDX 0
 #define ARY_IDX 1
@@ -345,7 +386,12 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
   dds_qos_t *qos;
   dds_return_t rc;
 
-  printf ("multi_sertopic: %s %s\n", (pp_pub == pp_sub) ? "local" : "remote", fastpath ? "fastpath" : "slowpath");
+  printf ("multi_sertopic: %s %s\n", (pp_pub == pp_sub) ? "local" : "remote", multi_sertopic_modestr (mode));
+
+  /* Transient-local mode is for checking the local historical data delivery path (for remote, there
+     is nothing special about it), and knowing it is local means we don't have to wait for historical
+     data to arrive.  So check. */
+  assert (pp_pub == pp_sub || mode != MSM_TRANSLOCAL);
 
   waitset = dds_create_waitset (DDS_CYCLONEDDS_HANDLE);
   CU_ASSERT_FATAL (waitset > 0);
@@ -353,8 +399,13 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
   qos = dds_create_qos ();
   CU_ASSERT_FATAL (qos != NULL);
   dds_qset_reliability (qos, DDS_RELIABILITY_RELIABLE, DDS_INFINITY);
-  dds_qset_destination_order (qos, DDS_DESTINATIONORDER_BY_SOURCE_TIMESTAMP);
+  dds_qset_destination_order (qos, DDS_DESTINATIONORDER_BY_RECEPTION_TIMESTAMP);
   dds_qset_history (qos, DDS_HISTORY_KEEP_ALL, 0);
+  if (mode == MSM_TRANSLOCAL)
+  {
+    dds_qset_durability (qos, DDS_DURABILITY_TRANSIENT_LOCAL);
+    dds_qset_durability_service (qos, 0, DDS_HISTORY_KEEP_ALL, 0, DDS_LENGTH_UNLIMITED, DDS_LENGTH_UNLIMITED, DDS_LENGTH_UNLIMITED);
+  }
 
   create_unique_topic_name ("ddsc_multi_sertopic_lease_duration_zero", name, sizeof name);
 
@@ -373,56 +424,37 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
     sub_topics[i] = dds_create_topic (pp_sub, descs[i], name, qos, NULL);
     CU_ASSERT_FATAL (sub_topics[i] > 0);
   }
-  DDSRT_STATIC_ASSERT (sizeof (readers) >= sizeof (sub_topics));
-  DDSRT_STATIC_ASSERT ((sizeof (readers) % sizeof (sub_topics)) == 0);
-  for (size_t i = 0; i < sizeof (sub_topics) / sizeof (sub_topics[0]); i++)
-  {
-    readers[i] = dds_create_reader (pp_sub, sub_topics[i], qos, NULL);
-    CU_ASSERT_FATAL (readers[i] > 0);
-  }
-  for (size_t i = sizeof (sub_topics) / sizeof (sub_topics[0]); i < sizeof (readers) / sizeof (readers[0]); i++)
-  {
-    const size_t nrd = sizeof (readers) / sizeof (readers[0]);
-    const size_t ntp = sizeof (sub_topics) / sizeof (sub_topics[0]);
-    readers[i] = dds_create_reader (pp_sub, sub_topics[(i - ntp) / (nrd / ntp - 1)], qos, NULL);
-    CU_ASSERT_FATAL (readers[i] > 0);
-  }
 
-  dds_delete_qos (qos);
+  if (mode != MSM_TRANSLOCAL)
+  {
+    create_readers (pp_sub, sizeof (readers) / sizeof (readers[0]), readers, sizeof (sub_topics) / sizeof (sub_topics[0]), sub_topics, qos, waitset);
 
-  /* wait for discovery to complete */
-  for (size_t i = 0; i < sizeof (writers) / sizeof (writers[0]); i++)
-  {
-    rc = dds_set_status_mask (writers[i], DDS_PUBLICATION_MATCHED_STATUS);
-    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
-    rc = dds_waitset_attach (waitset, writers[i], -(dds_attach_t)i - 1);
-    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
-  }
-  for (size_t i = 0; i < sizeof (readers) / sizeof (readers[0]); i++)
-  {
-    rc = dds_set_status_mask (readers[i], DDS_SUBSCRIPTION_MATCHED_STATUS | DDS_DATA_AVAILABLE_STATUS);
-    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
-    rc = dds_waitset_attach (waitset, readers[i], (dds_attach_t)i);
-    CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
-  }
+    for (size_t i = 0; i < sizeof (writers) / sizeof (writers[0]); i++)
+    {
+      rc = dds_set_status_mask (writers[i], DDS_PUBLICATION_MATCHED_STATUS);
+      CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
+      rc = dds_waitset_attach (waitset, writers[i], -(dds_attach_t)i - 1);
+      CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
+    }
 
-  printf ("wait for discovery, fastpath_ok; delete & recreate readers\n");
-  while (!(get_and_check_writer_status (sizeof (writers) / sizeof (writers[0]), writers, sizeof (readers) / sizeof (readers[0])) &&
-           get_and_check_reader_status (sizeof (readers) / sizeof (readers[0]), readers, sizeof (writers) / sizeof (writers[0]))))
-  {
-    rc = dds_waitset_wait (waitset, NULL, 0, DDS_SECS(5));
-    CU_ASSERT_FATAL (rc >= 1);
-  }
+    printf ("wait for discovery, fastpath_ok; delete & recreate readers\n");
+    while (!(get_and_check_writer_status (sizeof (writers) / sizeof (writers[0]), writers, sizeof (readers) / sizeof (readers[0])) &&
+             get_and_check_reader_status (sizeof (readers) / sizeof (readers[0]), readers, sizeof (writers) / sizeof (writers[0]))))
+    {
+      rc = dds_waitset_wait (waitset, NULL, 0, DDS_SECS(5));
+      CU_ASSERT_FATAL (rc >= 1);
+    }
 
-  /* we want to check both the fast path and the slow path ... so first wait
-   for it to be set on all (proxy) writers, then possibly reset it */
-  for (size_t i = 0; i < sizeof (readers) / sizeof (readers[0]); i++)
-    waitfor_or_reset_fastpath (readers[i], true, sizeof (writers) / sizeof (writers[0]));
-  if (!fastpath)
-  {
-    printf ("clear fastpath_ok\n");
+    /* we want to check both the fast path and the slow path ... so first wait
+       for it to be set on all (proxy) writers, then possibly reset it */
     for (size_t i = 0; i < sizeof (readers) / sizeof (readers[0]); i++)
-      waitfor_or_reset_fastpath (readers[i], false, sizeof (writers) / sizeof (writers[0]));
+      waitfor_or_reset_fastpath (readers[i], true, sizeof (writers) / sizeof (writers[0]));
+    if (mode == MSM_SLOWPATH)
+    {
+      printf ("clear fastpath_ok\n");
+      for (size_t i = 0; i < sizeof (readers) / sizeof (readers[0]); i++)
+        waitfor_or_reset_fastpath (readers[i], false, sizeof (writers) / sizeof (writers[0]));
+    }
   }
 
   /* check the log output for deserialization failures */
@@ -465,6 +497,11 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
     CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
   }
 
+  if (mode == MSM_TRANSLOCAL)
+  {
+    create_readers (pp_sub, sizeof (readers) / sizeof (readers[0]), readers, sizeof (sub_topics) / sizeof (sub_topics[0]), sub_topics, qos, waitset);
+  }
+
   /* All readers should have received three samples, and those that are of type seq
      should have received one extra (whereas the others should cause deserialization
      failure warnings) */
@@ -472,8 +509,14 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
   const size_t nexp = ((sizeof (writers) / sizeof (writers[0])) *
                          (sizeof (readers) / sizeof (readers[0])) +
                          ((sizeof (readers) / sizeof (readers[0])) / (sizeof (sub_topics) / sizeof (sub_topics[0]))));
-  /* expecting exactly as many deserialization failures as there are topics other than seq */
-  const size_t nexp_fail = sizeof (sub_topics) / sizeof (sub_topics[0]) - 1;
+  /* For the volatile case, expecting exactly as many deserialization failures as there
+     are topics other than seq because the conversion is done only once for each topic,
+     even if there are multiple readers.  For transient-local data, the data set is
+     converted for each new reader (of a different topic) and there will therefore be more
+     conversion failures. */
+  const size_t nexp_fail =
+    (sizeof (sub_topics) / sizeof (sub_topics[0]) - 1) *
+    (mode != MSM_TRANSLOCAL ? 1 : (sizeof (readers) / sizeof (readers[0])) / (sizeof (sub_topics) / sizeof (sub_topics[0])));
   uint32_t nseen = 0;
   while (nseen < nexp)
   {
@@ -572,6 +615,7 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
   /* deleting the waitset is important: it is bound to the library rather than to
      a domain and consequently won't be deleted simply because all domains are */
   rc = dds_delete (waitset);
+  dds_delete_qos (qos);
 
   CU_ASSERT_FATAL (rc == DDS_RETCODE_OK);
   dds_set_log_sink (0, NULL);
@@ -579,20 +623,25 @@ static void ddsc_multi_sertopic_impl (dds_entity_t pp_pub, dds_entity_t pp_sub,
 
 CU_Test(ddsc_multi_sertopic, local, .init = multi_sertopic_init, .fini = multi_sertopic_fini)
 {
-  ddsc_multi_sertopic_impl (g_pub_participant, g_pub_participant, true);
+  ddsc_multi_sertopic_impl (g_pub_participant, g_pub_participant, MSM_FASTPATH);
 }
 
 CU_Test(ddsc_multi_sertopic, remote, .init = multi_sertopic_init, .fini = multi_sertopic_fini)
 {
-  ddsc_multi_sertopic_impl (g_pub_participant, g_sub_participant, true);
+  ddsc_multi_sertopic_impl (g_pub_participant, g_sub_participant, MSM_FASTPATH);
 }
 
 CU_Test(ddsc_multi_sertopic, local_slowpath, .init = multi_sertopic_init, .fini = multi_sertopic_fini)
 {
-  ddsc_multi_sertopic_impl (g_pub_participant, g_pub_participant, false);
+  ddsc_multi_sertopic_impl (g_pub_participant, g_pub_participant, MSM_SLOWPATH);
 }
 
 CU_Test(ddsc_multi_sertopic, remote_slowpath, .init = multi_sertopic_init, .fini = multi_sertopic_fini)
 {
-  ddsc_multi_sertopic_impl (g_pub_participant, g_sub_participant, false);
+  ddsc_multi_sertopic_impl (g_pub_participant, g_sub_participant, MSM_SLOWPATH);
+}
+
+CU_Test(ddsc_multi_sertopic, transient_local, .init = multi_sertopic_init, .fini = multi_sertopic_fini)
+{
+  ddsc_multi_sertopic_impl (g_pub_participant, g_pub_participant, MSM_TRANSLOCAL);
 }
diff --git a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
index 1343c23..39a8841 100644
--- a/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_serdata.h
@@ -163,6 +163,22 @@ struct ddsi_serdata_ops {
 
 DDS_EXPORT void ddsi_serdata_init (struct ddsi_serdata *d, const struct ddsi_sertopic *tp, enum ddsi_serdata_kind kind);
 
+/**
+ * @brief Return a reference to a serdata with possible topic conversion
+ *
+ * If `serdata` is of topic `topic`, this increments the reference count and returns
+ * `serdata`.  Otherwise, it constructs a new one from the serialised representation of
+ * `serdata`.  This can fail, in which case it returns NULL.
+ *
+ * @param[in] topic    sertopic the returned serdata must have
+ * @param[in] serdata  source sample (untouched except for the reference count and/or
+ *   extracting the serialised representation)
+ * @returns A reference to a serdata that is equivalent to the input with the correct
+ *   topic, or a null pointer on failure.  The reference must be released with @ref
+ *   ddsi_serdata_unref.
+ */
+DDS_EXPORT struct ddsi_serdata *ddsi_serdata_ref_as_topic (const struct ddsi_sertopic *topic, struct ddsi_serdata *serdata);
+
 DDS_EXPORT inline struct ddsi_serdata *ddsi_serdata_ref (const struct ddsi_serdata *serdata_const) {
   struct ddsi_serdata *serdata = (struct ddsi_serdata *)serdata_const;
   ddsrt_atomic_inc32 (&serdata->refc);
diff --git a/src/core/ddsi/src/ddsi_serdata.c b/src/core/ddsi/src/ddsi_serdata.c
index d1f5fa6..9bae824 100644
--- a/src/core/ddsi/src/ddsi_serdata.c
+++ b/src/core/ddsi/src/ddsi_serdata.c
@@ -32,6 +32,27 @@ void ddsi_serdata_init (struct ddsi_serdata *d, const struct ddsi_sertopic *tp,
   ddsrt_atomic_st32 (&d->refc, 1);
 }
 
+struct ddsi_serdata *ddsi_serdata_ref_as_topic (const struct ddsi_sertopic *topic, struct ddsi_serdata *serdata)
+{
+  if (serdata->topic == topic)
+    return ddsi_serdata_ref (serdata);
+  else
+  {
+    /* ouch ... convert a serdata from one sertopic to another ... */
+    struct ddsi_serdata *converted;
+    ddsrt_iovec_t iov;
+    uint32_t size = ddsi_serdata_size (serdata);
+    (void) ddsi_serdata_to_ser_ref (serdata, 0, size, &iov);
+    if ((converted = ddsi_serdata_from_ser_iov (topic, serdata->kind, 1, &iov, size)) != NULL)
+    {
+      converted->statusinfo = serdata->statusinfo;
+      converted->timestamp = serdata->timestamp;
+    }
+    ddsi_serdata_to_ser_unref (serdata, &iov);
+    return converted;
+  }
+}
+
 extern inline struct ddsi_serdata *ddsi_serdata_ref (const struct ddsi_serdata *serdata_const);
 extern inline void ddsi_serdata_unref (struct ddsi_serdata *serdata);
 extern inline uint32_t ddsi_serdata_size (const struct ddsi_serdata *d);
diff --git a/src/core/ddsi/src/q_entity.c b/src/core/ddsi/src/q_entity.c
index 3fa1806..51ef631 100644
--- a/src/core/ddsi/src/q_entity.c
+++ b/src/core/ddsi/src/q_entity.c
@@ -2274,6 +2274,34 @@ static void writer_add_connection (struct writer *wr, struct proxy_reader *prd,
   }
 }
 
+static void deliver_historical_data (const struct writer *wr, const struct reader *rd)
+{
+  struct ddsi_domaingv * const gv = wr->e.gv;
+  struct ddsi_tkmap * const tkmap = gv->m_tkmap;
+  struct whc_sample_iter it;
+  struct whc_borrowed_sample sample;
+  /* FIXME: should limit ourselves to what it is available because of durability history, not writer history */
+  whc_sample_iter_init (wr->whc, &it);
+  while (whc_sample_iter_borrow_next (&it, &sample))
+  {
+    struct ddsi_serdata *payload;
+    if ((payload = ddsi_serdata_ref_as_topic (rd->topic, sample.serdata)) == NULL)
+    {
+      GVWARNING ("local: deserialization of %s/%s as %s/%s failed in topic type conversion\n",
+                 wr->topic->name, wr->topic->type_name, rd->topic->name, rd->topic->type_name);
+    }
+    else
+    {
+      struct ddsi_writer_info wrinfo;
+      struct ddsi_tkmap_instance *tk = ddsi_tkmap_lookup_instance_ref (tkmap, payload);
+      ddsi_make_writer_info (&wrinfo, &wr->e, wr->xqos, payload->statusinfo);
+      (void) ddsi_rhc_store (rd->rhc, &wrinfo, payload, tk);
+      ddsi_tkmap_instance_unref (tkmap, tk);
+      ddsi_serdata_unref (payload);
+    }
+  }
+}
+
 static void writer_add_local_connection (struct writer *wr, struct reader *rd)
 {
   struct wr_rd_match *m = ddsrt_malloc (sizeof (*m));
@@ -2296,26 +2324,9 @@ static void writer_add_local_connection (struct writer *wr, struct reader *rd)
   local_reader_ary_insert (&wr->rdary, rd);
 
   /* Store available data into the late joining reader when it is reliable (we don't do
-     historical data for best-effort data over the wire, so also not locally).
-     FIXME: should limit ourselves to what it is available because of durability history,
-     not writer history */
+     historical data for best-effort data over the wire, so also not locally). */
   if (rd->xqos->reliability.kind > DDS_RELIABILITY_BEST_EFFORT && rd->xqos->durability.kind > DDS_DURABILITY_VOLATILE)
-  {
-    struct ddsi_tkmap *tkmap = rd->e.gv->m_tkmap;
-    struct whc_sample_iter it;
-    struct whc_borrowed_sample sample;
-    whc_sample_iter_init(wr->whc, &it);
-    while (whc_sample_iter_borrow_next(&it, &sample))
-    {
-      struct ddsi_writer_info wrinfo;
-      struct ddsi_serdata *payload = sample.serdata;
-      /* FIXME: whc has tk reference in its index nodes, which is what we really should be iterating over anyway, and so we don't really have to look them up anymore */
-      struct ddsi_tkmap_instance *tk = ddsi_tkmap_lookup_instance_ref (tkmap, payload);
-      ddsi_make_writer_info (&wrinfo, &wr->e, wr->xqos, sample.serdata->statusinfo);
-      (void) ddsi_rhc_store (rd->rhc, &wrinfo, payload, tk);
-      ddsi_tkmap_instance_unref (tkmap, tk);
-    }
-  }
+    deliver_historical_data (wr, rd);
 
   ddsrt_mutex_unlock (&wr->e.lock);