diff --git a/esphome/components/web_server_idf/web_server_idf.cpp b/esphome/components/web_server_idf/web_server_idf.cpp
index 22a80944240..b43196ec481 100644
--- a/esphome/components/web_server_idf/web_server_idf.cpp
+++ b/esphome/components/web_server_idf/web_server_idf.cpp
@@ -532,10 +532,12 @@ void AsyncEventSource::adopt_pending_sessions_main_loop_() {
       continue;
     }
     this->sessions_.push_back(rsp);
+    // Prime first so on_connect_ observes a session that has already sent its
+    // initial ping/config/sorting_groups, matching the pre-refactor ordering.
+    rsp->start_session_main_loop_();
     if (this->on_connect_) {
       this->on_connect_(rsp);
     }
-    rsp->start_session_main_loop_();
   }
 }
 
diff --git a/esphome/components/web_server_idf/web_server_idf.h b/esphome/components/web_server_idf/web_server_idf.h
index 742a5446959..579383b50d2 100644
--- a/esphome/components/web_server_idf/web_server_idf.h
+++ b/esphome/components/web_server_idf/web_server_idf.h
@@ -339,6 +339,8 @@ class AsyncEventSource : public AsyncWebHandler {
   // NOLINTNEXTLINE(readability-identifier-naming)
   void handleRequest(AsyncWebServerRequest *request) override;
   // NOLINTNEXTLINE(readability-identifier-naming)
+  // Callback runs on the main loop (not the httpd task) after the session's
+  // initial ping/config/sorting_groups have been sent.
   void onConnect(connect_handler_t &&cb) { this->on_connect_ = std::move(cb); }
 
   void try_send_nodefer(const char *message, const char *event = nullptr, uint32_t id = 0, uint32_t reconnect = 0);