fix(serve): allow server config with stop method to auto-start

The fix for #26142 incorrectly used `typeof def.stop !== 'function'`
to detect Server instances returned by Bun.serve(). This caused server
config objects with a custom `stop` method (e.g., Elysia apps) to not
auto-start.

Changed the detection to use `typeof def.reload !== 'function'` instead,
since `reload` is specific to Server instances and unlikely to be on
user config objects.

Fixes #26747

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/bundler/entry_points.zig

@@ -167,7 +167,7 @@ pub const ServerEntryPoint = struct {
                     \\var hmrSymbol = Symbol("BunServerHMR");
                     \\var entryNamespace = start;
                     \\function isServerConfig(def) {{
-                    \\   return def && def !== globalThis && (typeof def.fetch === 'function' || def.app != undefined) && typeof def.stop !== 'function';
+                    \\   return def && def !== globalThis && (typeof def.fetch === 'function' || def.app != undefined) && typeof def.reload !== 'function';
                     \\}}
                     \\if (typeof entryNamespace?.then === 'function') {{
                     \\   entryNamespace = entryNamespace.then((entryNamespace) => {{
@@ -206,7 +206,7 @@ pub const ServerEntryPoint = struct {
                 \\import * as start from "{f}";
                 \\var entryNamespace = start;
                 \\function isServerConfig(def) {{
-                \\   return def && def !== globalThis && (typeof def.fetch === 'function' || def.app != undefined) && typeof def.stop !== 'function';
+                \\   return def && def !== globalThis && (typeof def.fetch === 'function' || def.app != undefined) && typeof def.reload !== 'function';
                 \\}}
                 \\if (typeof entryNamespace?.then === 'function') {{
                 \\   entryNamespace = entryNamespace.then((entryNamespace) => {{

test/regression/issue/26747.test.ts

@@ -0,0 +1,77 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir } from "harness";
+
+// https://github.com/oven-sh/bun/issues/26747
+// Server config objects with a `stop` method should still auto-start.
+// The previous fix for #26142 incorrectly used the presence of a `stop` method
+// to detect Server instances, but user config objects (like Elysia apps) can
+// legitimately have a `stop` method.
+
+test("server config with stop method as default export should auto-start", async () => {
+  using dir = tempDir("issue-26747", {
+    "server.js": `
+// Export a config object with a stop method
+// This should still trigger auto-start
+export default {
+  port: 0,
+  fetch(req) {
+    return new Response("Hello from server with stop method");
+  },
+  stop() {
+    // Custom stop method - should not prevent auto-start
+  },
+};
+
+// Force the process to exit after 100ms so the test can verify the startup message
+// without the server blocking forever
+setTimeout(() => process.exit(0), 100);
+`,
+  });
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "server.js"],
+    env: bunEnv,
+    cwd: String(dir),
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  // Should have started the server (look for the debug message on stdout)
+  expect(stdout).toContain("Started");
+  expect(exitCode).toBe(0);
+});
+
+test("server config with both stop and reload methods should not auto-start", async () => {
+  // A config object with a `reload` method is likely a Server instance
+  // or something that manages itself, so we should not auto-start it
+  using dir = tempDir("issue-26747-reload", {
+    "server.js": `
+export default {
+  port: 0,
+  fetch(req) {
+    return new Response("Hello");
+  },
+  stop() {},
+  reload() {},
+};
+console.log("Script completed without auto-starting");
+`,
+  });
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "server.js"],
+    env: bunEnv,
+    cwd: String(dir),
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  // Should NOT have started the server because it has a reload method
+  expect(stdout).not.toContain("Started");
+  expect(stdout).toContain("Script completed without auto-starting");
+  expect(exitCode).toBe(0);
+});