fix: handle deferred loading promise rejections properly

packages/start-client-core/src/ssr-client.tsx

@@ -35,6 +35,15 @@ export interface StartSsrGlobal {
     id: number
     promiseState: DeferredPromiseState<any>
   }) => void
+  rejectPromise: (opts: {
+    matchId: string
+    id: number
+    error: {
+      message: string
+      stack?: string
+      name: string
+    }
+  }) => void
   injectChunk: (opts: { matchId: string; id: number; chunk: string }) => void
   closeStream: (opts: { matchId: string; id: number }) => void
 }

packages/start-server-core/src/ssr-server.ts

@@ -216,20 +216,40 @@ export function onMatchSettled(opts: {
 
   function injectPromise(entry: ServerExtractedPromise) {
     router.serverSsr!.injectScript(async () => {
-      await entry.promise
-
-      return `__TSR_SSR__.resolvePromise(${jsesc(
-        {
-          matchId: match.id,
-          id: entry.id,
-          promiseState: entry.promise[TSR_DEFERRED_PROMISE],
-        } satisfies ResolvePromiseState,
-        {
-          isScriptContext: true,
-          wrap: true,
-          json: true,
-        },
-      )})`
+      try {
+        await entry.promise
+
+        return `__TSR_SSR__.resolvePromise(${jsesc(
+          {
+            matchId: match.id,
+            id: entry.id,
+            promiseState: entry.promise[TSR_DEFERRED_PROMISE],
+          } satisfies ResolvePromiseState,
+          {
+            isScriptContext: true,
+            wrap: true,
+            json: true,
+          },
+        )})`
+      } catch (error) {
+        // Serialize and pass errors to the client
+        return `__TSR_SSR__.rejectPromise(${jsesc(
+          {
+            matchId: match.id,
+            id: entry.id,
+            error: {
+              message: error instanceof Error ? error.message : String(error),
+              stack: error instanceof Error ? error.stack : undefined,
+              name: error instanceof Error ? error.name : 'Unknown Error',
+            },
+          },
+          {
+            isScriptContext: true,
+            wrap: true,
+            json: true,
+          },
+        )})`
+      }
     })
   }
 

packages/start-server-core/src/tsrScript.ts

@@ -58,6 +58,23 @@ const __TSR_SSR__: StartSsrGlobal = {
     }
     return false
   },
+  rejectPromise: ({ matchId, id, error }) => {
+    const match = __TSR_SSR__.matches.find((m) => m.id === matchId)
+    if (match) {
+      const ex = match.extracted?.[id]
+      if (ex && ex.type === 'promise' && ex.value) {
+        // Rebuild the error object and pass it to the client
+        const reconstructedError = new Error(error.message)
+        reconstructedError.name = error.name
+        if (error.stack) {
+          reconstructedError.stack = error.stack
+        }
+        ex.value.reject(reconstructedError)
+        return true
+      }
+    }
+    return false
+  },
   injectChunk: ({ matchId, id, chunk }) => {
     const match = __TSR_SSR__.matches.find((m) => m.id === matchId)