Suppress Node DEP0040 punycode warning in CLI startup

src/cli/suppressNodeWarnings.ts

@@ -0,0 +1,47 @@
+/**
+ * Suppress known noisy runtime deprecations from transitive dependencies while
+ * keeping all other warnings visible.
+ */
+export function shouldSuppressNodeWarning(code: string | undefined, message: string): boolean {
+  if (code === 'DEP0040') {
+    return true;
+  }
+  return /`punycode` module is deprecated/i.test(message);
+}
+
+export function installNodeWarningFilter(): void {
+  const stateKey = Symbol.for('flynn.nodeWarningFilterInstalled');
+  const globalState = globalThis as Record<PropertyKey, unknown>;
+  if (globalState[stateKey]) {
+    return;
+  }
+  globalState[stateKey] = true;
+
+  const originalEmitWarning = process.emitWarning.bind(process);
+
+  process.emitWarning = ((warning: unknown, ...args: unknown[]) => {
+    const message = warning instanceof Error
+      ? warning.message
+      : typeof warning === 'string'
+        ? warning
+        : String(warning);
+
+    let code: string | undefined;
+    if (warning instanceof Error && typeof (warning as { code?: unknown }).code === 'string') {
+      code = (warning as { code?: string }).code;
+    }
+    if (typeof args[0] === 'string') {
+      code = args[0];
+    } else if (args[0] && typeof args[0] === 'object' && typeof (args[0] as { code?: unknown }).code === 'string') {
+      code = (args[0] as { code?: string }).code;
+    }
+
+    if (shouldSuppressNodeWarning(code, message)) {
+      return;
+    }
+
+    (originalEmitWarning as (...params: unknown[]) => void)(warning, ...args);
+  }) as typeof process.emitWarning;
+}
+
+installNodeWarningFilter();