From ae4e2b5dd0e02f45d75f68e8f0242f3e3ef28eb2 Mon Sep 17 00:00:00 2001
From: Abhay Yadav <abhay0005@Abhays-MacBook-Air.local>
Date: Thu, 19 Mar 2026 20:16:06 +0530
Subject: [PATCH] fix: detect Bun runtime automatically when not explicitly
 configured

---
 packages/cli-v3/src/config.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/cli-v3/src/config.ts b/packages/cli-v3/src/config.ts
index af5623e0176..9cfe2fe1063 100644
--- a/packages/cli-v3/src/config.ts
+++ b/packages/cli-v3/src/config.ts
@@ -191,7 +191,8 @@ async function resolveConfig(
     ["run_engine_v2" as const].concat(config.compatibilityFlags ?? [])
   );
 
-  const defaultRuntime: BuildRuntime = features.run_engine_v2 ? "node" : DEFAULT_RUNTIME;
+  const detectedRuntime: BuildRuntime = typeof process.versions.bun === "string" ? "bun" : "node";
+  const defaultRuntime: BuildRuntime = config.runtime ?? detectedRuntime;
 
   const mergedConfig = defu(
     {