diff --git a/pkg/urbit/include/c/motes.h b/pkg/urbit/include/c/motes.h
index 676502461..15320ea06 100644
--- a/pkg/urbit/include/c/motes.h
+++ b/pkg/urbit/include/c/motes.h
@@ -1226,6 +1226,7 @@
 #   define c3__weak   c3_s4('w','e','a','k')
 #   define c3__web    c3_s3('w','e','b')
 #   define c3__wet    c3_s3('w','e','t')
+#   define c3__wend   c3_s4('w','e','n','d')
 #   define c3__werp   c3_s4('w','e','r','p')
 #   define c3__west   c3_s4('w','e','s','t')
 #   define c3__what   c3_s4('w','h','a','t')
diff --git a/pkg/urbit/include/vere/vere.h b/pkg/urbit/include/vere/vere.h
index de62a3fdd..68374e590 100644
--- a/pkg/urbit/include/vere/vere.h
+++ b/pkg/urbit/include/vere/vere.h
@@ -542,8 +542,9 @@
           u3_psat_init = 0,                   //  initialized
           u3_psat_boot = 1,                   //  bootstrap
           u3_psat_play = 2,                   //  replaying
-          u3_psat_work = 3,                   //  working
-          u3_psat_done = 4                    //  shutting down
+          u3_psat_wyrd = 3,                   //  versioning
+          u3_psat_work = 4,                   //  working
+          u3_psat_done = 5                    //  shutting down
         } u3_psat;
 
       /* u3_boot: bootstrap event sequence
diff --git a/pkg/urbit/vere/io/hind.c b/pkg/urbit/vere/io/hind.c
index 37d090399..b8b1577ee 100644
--- a/pkg/urbit/vere/io/hind.c
+++ b/pkg/urbit/vere/io/hind.c
@@ -53,6 +53,14 @@ _hind_io_kick(u3_auto* car_u, u3_noun wir, u3_noun cad)
         ret_o = c3y;
         u3l_log("<<<reset>>>\n");
       } break;
+
+      //  NB: startup explicitly handled in pier.c
+      //
+      //    XX review arvo upgrade scenaria
+      //
+      case c3__wend: {
+        ret_o = c3y;
+      } break;
     }
   }
 
diff --git a/pkg/urbit/vere/lord.c b/pkg/urbit/vere/lord.c
index f148f1c69..394cb6c5e 100644
--- a/pkg/urbit/vere/lord.c
+++ b/pkg/urbit/vere/lord.c
@@ -1090,6 +1090,7 @@ u3_lord_init(c3_c* pax_c, c3_w wag_w, c3_d key_d[4], u3_lord_cb cb_u)
 {
   u3_lord* god_u = c3_calloc(sizeof *god_u);
   god_u->liv_o = c3n;
+  god_u->pin_o = c3n;
   god_u->wag_w = wag_w;
   god_u->bin_c = u3_Host.wrk_c; //  XX strcopy
   god_u->pax_c = pax_c;  //  XX strcopy
diff --git a/pkg/urbit/vere/pier.c b/pkg/urbit/vere/pier.c
index 41b48fc09..2130a540b 100644
--- a/pkg/urbit/vere/pier.c
+++ b/pkg/urbit/vere/pier.c
@@ -285,7 +285,8 @@ _pier_on_lord_work_spin(void* ptr_v, u3_atom pin, c3_o del_o)
 {
   u3_pier* pir_u = ptr_v;
 
-  c3_assert(  (u3_psat_work == pir_u->sat_e)
+  c3_assert(  (u3_psat_wyrd == pir_u->sat_e)
+           || (u3_psat_work == pir_u->sat_e)
            || (u3_psat_done == pir_u->sat_e) );
 
   u3_term_start_spinner(pin, del_o);
@@ -298,7 +299,8 @@ _pier_on_lord_work_spun(void* ptr_v)
 {
   u3_pier* pir_u = ptr_v;
 
-  c3_assert(  (u3_psat_work == pir_u->sat_e)
+  c3_assert(  (u3_psat_wyrd == pir_u->sat_e)
+           || (u3_psat_work == pir_u->sat_e)
            || (u3_psat_done == pir_u->sat_e) );
 
   u3_term_stop_spinner();
@@ -402,13 +404,14 @@ u3_pier_spin(u3_pier* pir_u)
 {
   //  XX return c3n instead?
   //
-  c3_assert(  (u3_psat_work == pir_u->sat_e)
-           || (u3_psat_done == pir_u->sat_e) );
+  if (  u3_psat_work == pir_u->sat_e
+     || u3_psat_done == pir_u->sat_e )
+  {
+    u3_work* wok_u = pir_u->wok_u;
 
-  u3_work* wok_u = pir_u->wok_u;
-
-  if ( !uv_is_active((uv_handle_t*)&wok_u->idl_u) ) {
-    uv_idle_start(&wok_u->idl_u, _pier_work_idle_cb);
+    if ( !uv_is_active((uv_handle_t*)&wok_u->idl_u) ) {
+      uv_idle_start(&wok_u->idl_u, _pier_work_idle_cb);
+    }
   }
 }
 
@@ -488,8 +491,7 @@ _pier_work_init(u3_pier* pir_u)
 {
   u3_work* wok_u;
 
-  c3_assert(  (u3_psat_init == pir_u->sat_e)
-           || (u3_psat_play == pir_u->sat_e) );
+  c3_assert( u3_psat_wyrd == pir_u->sat_e );
 
   pir_u->sat_e = u3_psat_work;
   pir_u->wok_u = wok_u = c3_calloc(sizeof(*wok_u));
@@ -552,6 +554,206 @@ _pier_work_init(u3_pier* pir_u)
   _pier_work(wok_u);
 }
 
+/* _pier_wyrd_good(): %wyrd version negotation succeeded.
+*/
+static void
+_pier_wyrd_good(u3_pier* pir_u, u3_ovum* egg_u, u3_gift* gif_u)
+{
+  //  restore event callbacks
+  //
+  {
+    u3_lord* god_u = pir_u->god_u;
+    god_u->cb_u.work_done_f = _pier_on_lord_work_done;
+    god_u->cb_u.work_bail_f = _pier_on_lord_work_bail;
+  }
+
+  //  initialize i/o drivers
+  //
+  _pier_work_init(pir_u);
+
+  //  plan %wyrd effects
+  //
+  _pier_gift_plan(pir_u->wok_u, gif_u);
+
+  //  free %wyrd driver and ovum
+  //
+  {
+    u3_auto* car_u = egg_u->car_u;
+    u3_auto_done(egg_u);
+    c3_free(car_u);
+  }
+}
+
+/* _pier_wyrd_fail(): %wyrd version negotation failed.
+*/
+static void
+_pier_wyrd_fail(u3_pier* pir_u, u3_ovum* egg_u, u3_noun lud)
+{
+  //  XX version negotiation failed, print upgrade message
+  //
+  u3l_log("pier: version negotation failed\n\n");
+
+  //  XX only print trace with -v ?
+  //
+  u3_auto_bail_slog(egg_u, lud);
+
+  //  free %wyrd driver and ovum
+  //
+  {
+    u3_auto* car_u = egg_u->car_u;
+    u3_auto_done(egg_u);
+    c3_free(car_u);
+  }
+
+  u3_pier_bail(pir_u);
+}
+
+//  XX organizing version constants
+//
+#define VERE_NAME   "vere"
+#define VERE_MAJOR  0
+#define VERE_MINOR  10
+#define VERE_PATCH  9
+#define VERE_ZUSE   309
+
+/* _pier_wyrd_aver(): check for %wend effect and version downgrade. RETAIN
+*/
+static c3_o
+_pier_wyrd_aver(u3_noun act)
+{
+  u3_noun fec, kel, ver;
+
+  //    XX review, %wend re: %wyrd optional?
+  //
+  while ( u3_nul != act ) {
+    u3x_cell(act, &fec, &act);
+
+    if ( c3__wend == u3h(fec) ) {
+      kel = u3t(fec);
+
+      //  traverse $wynn, check for downgrades
+      //
+      while ( u3_nul != kel ) {
+        u3x_cell(kel, &ver, &kel);
+
+        //  check for %zuse downgrade
+        //
+        if (  (c3__zuse == u3h(ver))
+           && (VERE_ZUSE != u3t(ver)) )
+        {
+          return c3n;
+        }
+
+        //  XX in the future, send %wend to serf
+        //  to also negotiate downgrade of nock/hoon/&c?
+        //  (we don't want to have to filter effects)
+        //
+      }
+    }
+  }
+
+  return c3y;
+}
+
+/* _pier_on_lord_wyrd_done(): callback for successful %wyrd event.
+*/
+static void
+_pier_on_lord_wyrd_done(void*    ptr_v,
+                        u3_ovum* egg_u,
+                        u3_fact* tac_u,
+                        u3_gift* gif_u)
+{
+  u3_pier* pir_u = ptr_v;
+
+  c3_assert( u3_psat_wyrd == pir_u->sat_e );
+
+  //  arvo's side of version negotiation succeeded
+  //  traverse [gif_y] and validate
+  //
+  if ( c3n == _pier_wyrd_aver(gif_u->act) ) {
+    u3_fact_free(tac_u);
+    u3_gift_free(gif_u);
+
+    //  XX messageing
+    //
+    u3l_log("pier: version negotiation failed; downgrade\n");
+    _pier_wyrd_fail(pir_u, egg_u, u3_nul);
+  }
+  else {
+    //  enqueue %wyrd event-log commit
+    //
+    u3_disk_plan(pir_u->log_u, tac_u);
+
+    //  finalize %wyrd success
+    //
+    _pier_wyrd_good(pir_u, egg_u, gif_u);
+  }
+}
+
+/* _pier_on_lord_wyrd_bail(): callback for failed %wyrd event.
+*/
+static void
+_pier_on_lord_wyrd_bail(void* ptr_v, u3_ovum* egg_u, u3_noun lud)
+{
+  u3_pier* pir_u = ptr_v;
+
+  c3_assert( u3_psat_wyrd == pir_u->sat_e );
+
+  //  print %wyrd failure and exit
+  //
+  //    XX check bail mote, retry on %intr, %meme, &c
+  //
+  _pier_wyrd_fail(pir_u, egg_u, lud);
+}
+
+/* _pier_wyrd_init(): send %wyrd.
+*/
+static void
+_pier_wyrd_init(u3_pier* pir_u)
+{
+  u3_lord* god_u = pir_u->god_u;
+
+  pir_u->sat_e = u3_psat_wyrd;
+
+  u3l_log("vere: checking version compatiblity\n");
+
+  _pier_work_time(pir_u);
+  u3v_numb();
+
+  {
+    u3_noun ver = u3nq(u3i_string(VERE_NAME), VERE_MAJOR, VERE_MINOR, VERE_PATCH);
+    u3_noun kel = u3nl(u3nc(c3__zuse, VERE_ZUSE),       //  XX god_u->zus_w
+                       // u3nc(c3__lull, PIER_LULL),    //  XX define
+                       // u3nc(c3__arvo, god_u->arv_y), //  XX from both king and serf?
+                       u3nc(c3__hoon, god_u->hon_y),
+                       u3nc(c3__nock, god_u->noc_y),
+                       u3_none);
+    u3_noun wir = u3nc(c3__arvo, u3_nul);
+    u3_noun cad = u3nt(c3__wyrd, u3nc(u3k(u3A->sen), ver), kel);
+
+    {
+      u3_auto* car_u = c3_calloc(sizeof(*car_u));
+      u3_ovum* egg_u = u3_ovum_init(0, u3_blip, wir, cad);
+      u3_noun    ovo;
+
+      car_u->pir_u = pir_u;
+      car_u->nam_m = c3__wyrd;
+
+      u3_auto_plan(car_u, egg_u);
+
+      //  instead of subscribing with u3_auto_peer(),
+      //  we swizzle the [god_u] callbacks for full control
+      //
+      god_u->cb_u.work_done_f = _pier_on_lord_wyrd_done;
+      god_u->cb_u.work_bail_f = _pier_on_lord_wyrd_bail;
+
+      c3_assert( u3_auto_next(car_u, &ovo) == egg_u );
+
+      u3_lord_work(god_u, egg_u, ovo);
+    }
+  }
+}
+
 /* _pier_play_plan(): enqueue events for replay.
 */
 static void
@@ -730,7 +932,7 @@ _pier_play(u3_play* pay_u)
     }
     else if ( pay_u->eve_d == log_u->dun_d ) {
       u3_lord_save(pir_u->god_u);
-      _pier_work_init(pir_u);
+      _pier_wyrd_init(pir_u);
     }
   }
   else {
@@ -1188,7 +1390,7 @@ _pier_on_lord_live(void* ptr_v)
       _pier_play_init(pir_u, eve_d);
     }
     else {
-      _pier_work_init(pir_u);
+      _pier_wyrd_init(pir_u);
     }
   }
 }