diff --git a/src/core/channel/census_filter.c b/src/core/channel/census_filter.c
index 3e0fc39..47461f7 100644
--- a/src/core/channel/census_filter.c
+++ b/src/core/channel/census_filter.c
@@ -82,15 +82,18 @@
   }
 }
 
-static void client_start_transport_op(grpc_call_element* elem, grpc_transport_op* op) {
+static void client_mutate_op(grpc_call_element *elem, grpc_transport_op *op) {
   call_data* calld = elem->call_data;
   channel_data* chand = elem->channel_data;
-  GPR_ASSERT(calld != NULL);
-  GPR_ASSERT(chand != NULL);
-  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0));
   if (op->send_ops) {
     extract_and_annotate_method_tag(op->send_ops, calld, chand);
   }
+}
+
+static void client_start_transport_op(grpc_call_element* elem, grpc_transport_op* op) {
+  call_data* calld = elem->call_data;
+  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0));
+  client_mutate_op(elem, op);
   grpc_call_next_op(elem, op);
 }
 
@@ -104,12 +107,8 @@
   calld->on_done_recv(calld->recv_user_data, success);
 }
 
-static void server_start_transport_op(grpc_call_element* elem, grpc_transport_op* op) {
+static void server_mutate_op(grpc_call_element *elem, grpc_transport_op *op) {
   call_data* calld = elem->call_data;
-  channel_data* chand = elem->channel_data;
-  GPR_ASSERT(calld != NULL);
-  GPR_ASSERT(chand != NULL);
-  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0));
   if (op->recv_ops) {
     /* substitute our callback for the op callback */
     calld->recv_ops = op->recv_ops;
@@ -118,7 +117,12 @@
     op->on_done_recv = server_on_done_recv;
     op->recv_user_data = elem;
   }
-  /* Always pass control up or down the stack depending on op->dir */
+}
+
+static void server_start_transport_op(grpc_call_element* elem, grpc_transport_op* op) {
+  call_data* calld = elem->call_data;
+  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0));
+  server_mutate_op(elem, op);
   grpc_call_next_op(elem, op);
 }
 
@@ -136,12 +140,13 @@
 }
 
 static void client_init_call_elem(grpc_call_element* elem,
-                                  const void* server_transport_data) {
+                                  const void* server_transport_data, grpc_transport_op *initial_op) {
   call_data* d = elem->call_data;
   GPR_ASSERT(d != NULL);
   init_rpc_stats(&d->stats);
   d->start_ts = gpr_now();
   d->op_id = census_tracing_start_op();
+  if (initial_op) client_mutate_op(elem, initial_op);
 }
 
 static void client_destroy_call_elem(grpc_call_element* elem) {
@@ -152,12 +157,13 @@
 }
 
 static void server_init_call_elem(grpc_call_element* elem,
-                                  const void* server_transport_data) {
+                                  const void* server_transport_data, grpc_transport_op *initial_op) {
   call_data* d = elem->call_data;
   GPR_ASSERT(d != NULL);
   init_rpc_stats(&d->stats);
   d->start_ts = gpr_now();
   d->op_id = census_tracing_start_op();
+  if (initial_op) server_mutate_op(elem, initial_op);
 }
 
 static void server_destroy_call_elem(grpc_call_element* elem) {
diff --git a/src/core/channel/channel_stack.c b/src/core/channel/channel_stack.c
index c121e27..022100e 100644
--- a/src/core/channel/channel_stack.c
+++ b/src/core/channel/channel_stack.c
@@ -148,6 +148,7 @@
 
 void grpc_call_stack_init(grpc_channel_stack *channel_stack,
                           const void *transport_server_data,
+                          grpc_transport_op *initial_op,
                           grpc_call_stack *call_stack) {
   grpc_channel_element *channel_elems = CHANNEL_ELEMS_FROM_STACK(channel_stack);
   size_t count = channel_stack->count;
@@ -165,7 +166,7 @@
     call_elems[i].filter = channel_elems[i].filter;
     call_elems[i].channel_data = channel_elems[i].channel_data;
     call_elems[i].call_data = user_data;
-    call_elems[i].filter->init_call_elem(&call_elems[i], transport_server_data);
+    call_elems[i].filter->init_call_elem(&call_elems[i], transport_server_data, initial_op);
     user_data +=
         ROUND_UP_TO_ALIGNMENT_SIZE(call_elems[i].filter->sizeof_call_data);
   }
diff --git a/src/core/channel/channel_stack.h b/src/core/channel/channel_stack.h
index 75897ff..94b1263 100644
--- a/src/core/channel/channel_stack.h
+++ b/src/core/channel/channel_stack.h
@@ -121,7 +121,8 @@
      transport and is on the server. Most filters want to ignore this
      argument.*/
   void (*init_call_elem)(grpc_call_element *elem,
-                         const void *server_transport_data);
+                         const void *server_transport_data,
+                         grpc_transport_op *initial_op);
   /* Destroy per call data.
      The filter does not need to do any chaining */
   void (*destroy_call_elem)(grpc_call_element *elem);
@@ -200,6 +201,7 @@
    server. */
 void grpc_call_stack_init(grpc_channel_stack *channel_stack,
                           const void *transport_server_data,
+                          grpc_transport_op *initial_op,
                           grpc_call_stack *call_stack);
 /* Destroy a call stack */
 void grpc_call_stack_destroy(grpc_call_stack *stack);
diff --git a/src/core/channel/child_channel.c b/src/core/channel/child_channel.c
index 2444173..817a2a8 100644
--- a/src/core/channel/child_channel.c
+++ b/src/core/channel/child_channel.c
@@ -121,7 +121,7 @@
 
 /* Constructor for call_data */
 static void lb_init_call_elem(grpc_call_element *elem,
-                              const void *server_transport_data) {}
+                              const void *server_transport_data, grpc_transport_op *initial_op) {}
 
 /* Destructor for call_data */
 static void lb_destroy_call_elem(grpc_call_element *elem) {}
@@ -261,13 +261,13 @@
 }
 
 grpc_child_call *grpc_child_channel_create_call(grpc_child_channel *channel,
-                                                grpc_call_element *parent) {
+                                                grpc_call_element *parent, grpc_transport_op *initial_op) {
   grpc_call_stack *stk = gpr_malloc((channel)->call_stack_size);
   grpc_call_element *lbelem;
   lb_call_data *lbcalld;
   lb_channel_data *lbchand;
 
-  grpc_call_stack_init(channel, NULL, stk);
+  grpc_call_stack_init(channel, NULL, initial_op, stk);
   lbelem = LINK_BACK_ELEM_FROM_CALL(stk);
   lbchand = lbelem->channel_data;
   lbcalld = lbelem->call_data;
diff --git a/src/core/channel/child_channel.h b/src/core/channel/child_channel.h
index 3869540..264a8bb 100644
--- a/src/core/channel/child_channel.h
+++ b/src/core/channel/child_channel.h
@@ -57,7 +57,7 @@
                                 int wait_for_callbacks);
 
 grpc_child_call *grpc_child_channel_create_call(grpc_child_channel *channel,
-                                                grpc_call_element *parent);
+                                                grpc_call_element *parent, grpc_transport_op *initial_op);
 grpc_call_element *grpc_child_call_get_top_element(grpc_child_call *call);
 void grpc_child_call_destroy(grpc_child_call *call);
 
diff --git a/src/core/channel/client_channel.c b/src/core/channel/client_channel.c
index 6ad50cb..e6b0f7b 100644
--- a/src/core/channel/client_channel.c
+++ b/src/core/channel/client_channel.c
@@ -105,7 +105,8 @@
   calld->state = CALL_ACTIVE;
 
   /* create a child call */
-  calld->s.active.child_call = grpc_child_channel_create_call(on_child, elem);
+  /* TODO(ctiller): pass the waiting op down here */
+  calld->s.active.child_call = grpc_child_channel_create_call(on_child, elem, NULL);
 
   return 1;
 }
diff --git a/src/core/channel/connected_channel.c b/src/core/channel/connected_channel.c
index 9e2d92f..5a5a849 100644
--- a/src/core/channel/connected_channel.c
+++ b/src/core/channel/connected_channel.c
@@ -95,15 +95,16 @@
 
 /* Constructor for call_data */
 static void init_call_elem(grpc_call_element *elem,
-                           const void *server_transport_data) {
+                           const void *server_transport_data,
+                           grpc_transport_op *initial_op) {
   call_data *calld = elem->call_data;
   channel_data *chand = elem->channel_data;
   int r;
 
   GPR_ASSERT(elem->filter == &grpc_connected_channel_filter);
-  r = grpc_transport_init_stream(chand->transport,
+  r = grpc_transport_1chand->transport,
                                  TRANSPORT_STREAM_FROM_CALL_DATA(calld),
-                                 server_transport_data);
+                                 server_transport_data, initial_op);
   GPR_ASSERT(r == 0);
 }
 
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 9c2af56..acdc98b 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -607,6 +607,7 @@
     lock(t);
     s->id = 0;
   } else {
+    /* already locked */
     s->id = (gpr_uint32)(gpr_uintptr)server_data;
     t->incoming_stream = s;
     grpc_chttp2_stream_map_add(&t->stream_map, s->id, s);
diff --git a/src/core/transport/transport.h b/src/core/transport/transport.h
index d000768..a51e01d 100644
--- a/src/core/transport/transport.h
+++ b/src/core/transport/transport.h
@@ -60,6 +60,23 @@
   GRPC_STREAM_CLOSED
 } grpc_stream_state;
 
+/* Transport op: a set of operations to perform on a transport */
+typedef struct grpc_transport_op {
+  grpc_stream_op_buffer *send_ops;
+  int is_last_send;
+  void (*on_done_send)(void *user_data, int success);
+  void *send_user_data;
+
+  grpc_stream_op_buffer *recv_ops;
+  grpc_stream_state *recv_state;
+  void (*on_done_recv)(void *user_data, int success);
+  void *recv_user_data;
+
+  grpc_pollset *bind_pollset;
+
+  grpc_status_code cancel_with_status;
+} grpc_transport_op;
+
 /* Callbacks made from the transport to the upper layers of grpc. */
 struct grpc_transport_callbacks {
   /* Initialize a new stream on behalf of the transport.
@@ -98,7 +115,7 @@
      server_data - either NULL for a client initiated stream, or a pointer
                    supplied from the accept_stream callback function */
 int grpc_transport_init_stream(grpc_transport *transport, grpc_stream *stream,
-                               const void *server_data);
+                               const void *server_data, grpc_transport_op *initial_op);
 
 /* Destroy transport data for a stream.
 
@@ -113,23 +130,6 @@
 void grpc_transport_destroy_stream(grpc_transport *transport,
                                    grpc_stream *stream);
 
-/* Transport op: a set of operations to perform on a transport */
-typedef struct grpc_transport_op {
-  grpc_stream_op_buffer *send_ops;
-  int is_last_send;
-  void (*on_done_send)(void *user_data, int success);
-  void *send_user_data;
-
-  grpc_stream_op_buffer *recv_ops;
-  grpc_stream_state *recv_state;
-  void (*on_done_recv)(void *user_data, int success);
-  void *recv_user_data;
-
-  grpc_pollset *bind_pollset;
-
-  grpc_status_code cancel_with_status;
-} grpc_transport_op;
-
 void grpc_transport_op_finish_with_failure(grpc_transport_op *op);
 
 /* TODO(ctiller): remove this */