From 438aaf9e956a47691b28898c098dea0eb4ccc932 Mon Sep 17 00:00:00 2001
From: Alistair Smith <hi@alistair.sh>
Date: Fri, 5 Dec 2025 11:14:45 -0800
Subject: [PATCH] use event.message when no event.error in HMR during event

---
 packages/bun-error/index.tsx   |  1 -
 src/bake/hmr-runtime-client.ts | 12 +++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/bun-error/index.tsx b/packages/bun-error/index.tsx
index 179c31cc5e..e31a9c440f 100644
--- a/packages/bun-error/index.tsx
+++ b/packages/bun-error/index.tsx
@@ -615,7 +615,6 @@ const NativeStackFrame = ({
       <div
         title={StackFrameScope[scope]}
         className="BunError-StackFrame-identifier"
-        // @ts-expect-error Custom CSS variables are not known by TypeScript
         style={{ "--max-length": `${maxLength}ch` }}
       >
         {getNativeStackFrameIdentifier(frame)}
diff --git a/src/bake/hmr-runtime-client.ts b/src/bake/hmr-runtime-client.ts
index bebe2dcc34..2de6b23f5b 100644
--- a/src/bake/hmr-runtime-client.ts
+++ b/src/bake/hmr-runtime-client.ts
@@ -237,8 +237,18 @@ function onHmrLoadError(event: Event | string, source?: string, lineno?: number,
 }
 
 window.addEventListener("error", event => {
-  onRuntimeError(event.error, true, false);
+  // In rare cases the error property might be null
+  // but it's unlikely that both error and message are gone
+  const value = event.error || event.message;
+  if (!value) {
+    console.log(
+      "[Bun] The HMR client detected a runtime error, but no useful value was found. Below is the full error event:",
+    );
+    console.log(event);
+  }
+  onRuntimeError(value, true, false);
 });
+
 window.addEventListener("unhandledrejection", event => {
   onRuntimeError(event.reason, true, true);
 });