diff --git a/source/cell.h b/source/cell.h
index bb3e24dc..55260316 100644
--- a/source/cell.h
+++ b/source/cell.h
@@ -1152,17 +1152,16 @@ JSValue CELL_USE_NAME(JSContext *js) { \
 JSValue CELL_USE_NAME(JSContext *js) { do { c ; } while(0); }
 
 /* ============================================================
-   WOTA Message Sending — C modules can send messages to actors
-   without needing a JSContext.
+   WOTA Message Sending — C modules can send messages to actors.
    ============================================================ */
 
 /* Check whether an actor with the given ID exists. */
 int JS_ActorExists(const char *actor_id);
 
-/* Send a WOTA-encoded message to an actor by ID.
+/* Send a WOTA-encoded message to the actor that owns ctx.
    Takes ownership of wb's data on success (caller must not free).
    On failure returns an error string; caller must free wb. */
-const char *JS_SendMessage(const char *actor_id, WotaBuffer *wb);
+const char *JS_SendMessage(JSContext *ctx, WotaBuffer *wb);
 
 #undef js_unlikely
 #undef inline
diff --git a/source/scheduler.c b/source/scheduler.c
index 49ddea5b..085db44e 100644
--- a/source/scheduler.c
+++ b/source/scheduler.c
@@ -1060,7 +1060,7 @@ int JS_ActorExists(const char *actor_id)
   return actor_exists(actor_id);
 }
 
-const char *JS_SendMessage(const char *actor_id, WotaBuffer *wb)
+const char *JS_SendMessage(JSContext *ctx, WotaBuffer *wb)
 {
   if (!wb || !wb->data || wb->size == 0)
     return "Empty WOTA buffer";
@@ -1072,7 +1072,7 @@ const char *JS_SendMessage(const char *actor_id, WotaBuffer *wb)
   blob_write_bytes(msg, wb->data, byte_len);
   blob_make_stone(msg);
 
-  const char *err = send_message(actor_id, msg);
+  const char *err = send_message(ctx->id, msg);
   if (!err) {
     /* Success — send_message took ownership of the blob.
        Free the WotaBuffer internals since we consumed them. */