fix: detect Bun runtime automatically when not explicitly configured

Abhay Yadav · Abhay Yadav · commit ae4e2b5dd0e0 · 2026-03-19T20:16:06.000+05:30
diff --git 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(
     {

Original file line number	Diff line number	Diff line change
`@@ -191,7 +191,8 @@ async function resolveConfig(`
`191`	`191`	`["run_engine_v2" as const].concat(config.compatibilityFlags ?? [])`
`192`	`192`	`);`
`193`	`193`
`194`		`- const defaultRuntime: BuildRuntime = features.run_engine_v2 ? "node" : DEFAULT_RUNTIME;`
	`194`	`+ const detectedRuntime: BuildRuntime = typeof process.versions.bun === "string" ? "bun" : "node";`
	`195`	`+ const defaultRuntime: BuildRuntime = config.runtime ?? detectedRuntime;`
`195`	`196`
`196`	`197`	`const mergedConfig = defu(`
`197`	`198`	`{`