From b7d982e5ea3c4050a6c41e3b934ede3bc41fcce8 Mon Sep 17 00:00:00 2001
From: Demian Parkhomenko <95881717+DemianParkhomenko@users.noreply.github.com>
Date: Thu, 19 Feb 2026 00:52:23 +0100
Subject: [PATCH 1/2] feat: add diagnostics_channel support for app
 initialization

---
 lib/application.js          |  1 +
 lib/diagnostics.js          |  7 +++++++
 lib/express.js              |  6 ++++++
 test/diagnostics-channel.js | 26 ++++++++++++++++++++++++++
 4 files changed, 40 insertions(+)
 create mode 100644 lib/diagnostics.js
 create mode 100644 test/diagnostics-channel.js

diff --git a/lib/application.js b/lib/application.js
index 47be2a20c1a..927d093be57 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -24,6 +24,7 @@ var compileTrust = require('./utils').compileTrust;
 var resolve = require('node:path').resolve;
 var once = require('once')
 var Router = require('router');
+const channels = require('./diagnostics');
 
 /**
  * Module variables.
diff --git a/lib/diagnostics.js b/lib/diagnostics.js
new file mode 100644
index 00000000000..f11044a2dad
--- /dev/null
+++ b/lib/diagnostics.js
@@ -0,0 +1,7 @@
+'use strict';
+
+const dc = require('node:diagnostics_channel');
+
+const initialization = dc.channel('express.initialization');
+
+module.exports = { initialization };
diff --git a/lib/express.js b/lib/express.js
index 2d502eb54e4..33309fa8435 100644
--- a/lib/express.js
+++ b/lib/express.js
@@ -19,6 +19,7 @@ var proto = require('./application');
 var Router = require('router');
 var req = require('./request');
 var res = require('./response');
+const channels = require('./diagnostics');
 
 /**
  * Expose `createApplication()`.
@@ -52,6 +53,11 @@ function createApplication() {
   })
 
   app.init();
+
+  if (channels.initialization.hasSubscribers) {
+    channels.initialization.publish({ express: app });
+  }
+
   return app;
 }
 
diff --git a/test/diagnostics-channel.js b/test/diagnostics-channel.js
new file mode 100644
index 00000000000..92e212c1c73
--- /dev/null
+++ b/test/diagnostics-channel.js
@@ -0,0 +1,26 @@
+'use strict'
+
+const dc = require('node:diagnostics_channel')
+const express = require('../')
+const assert = require('node:assert')
+
+describe('diagnostics channels', function () {
+  describe('express.initialization', function () {
+    it('should publish when app is created', function () {
+      let msg
+
+      dc.subscribe('express.initialization', function handler (data) {
+        msg = data
+        dc.unsubscribe('express.initialization', handler)
+      })
+
+      const app = express()
+      assert.ok(msg, 'express.initialization was not published')
+      assert.strictEqual(msg.express, app)
+    })
+
+    it('should not throw when there are no subscribers', function () {
+      assert.ok(express())
+    })
+  })
+})

From 73207d493d23c160714d13685638e596119423d4 Mon Sep 17 00:00:00 2001
From: Demian Parkhomenko <95881717+DemianParkhomenko@users.noreply.github.com>
Date: Fri, 20 Feb 2026 11:16:08 +0100
Subject: [PATCH 2/2] Fix contract of diagnostics channel publish

---
 lib/application.js          | 1 -
 lib/express.js              | 2 +-
 test/diagnostics-channel.js | 2 +-
 3 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/application.js b/lib/application.js
index 927d093be57..47be2a20c1a 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -24,7 +24,6 @@ var compileTrust = require('./utils').compileTrust;
 var resolve = require('node:path').resolve;
 var once = require('once')
 var Router = require('router');
-const channels = require('./diagnostics');
 
 /**
  * Module variables.
diff --git a/lib/express.js b/lib/express.js
index 33309fa8435..c4b1173ec13 100644
--- a/lib/express.js
+++ b/lib/express.js
@@ -55,7 +55,7 @@ function createApplication() {
   app.init();
 
   if (channels.initialization.hasSubscribers) {
-    channels.initialization.publish({ express: app });
+    channels.initialization.publish({ app });
   }
 
   return app;
diff --git a/test/diagnostics-channel.js b/test/diagnostics-channel.js
index 92e212c1c73..c4ed76ea829 100644
--- a/test/diagnostics-channel.js
+++ b/test/diagnostics-channel.js
@@ -16,7 +16,7 @@ describe('diagnostics channels', function () {
 
       const app = express()
       assert.ok(msg, 'express.initialization was not published')
-      assert.strictEqual(msg.express, app)
+      assert.strictEqual(msg.app, app)
     })
 
     it('should not throw when there are no subscribers', function () {