From bd2ba0a6857ca5f807b75c603bec6e2c52cebdc5 Mon Sep 17 00:00:00 2001
From: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>
Date: Sat, 24 Oct 2026 18:13:42 -0500
Subject: [PATCH] fix(schema): validate base64 attachments in linear time
 (#58811)

---
 packages/schema/src/prompt.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/schema/src/prompt.ts b/packages/schema/src/prompt.ts
index ba8a7a73079..0086ca11356 100644
--- a/packages/schema/src/prompt.ts
+++ b/packages/schema/src/prompt.ts
@@ -18,8 +18,12 @@ export const FileSource = Schema.Union([
   .annotate({ identifier: "Prompt.FileSource" })
 export type FileSource = typeof FileSource.Type
 
+// The canonical pattern backtracks on large inputs, so it only supplies metadata (OpenAPI, errors) while an equivalent linear check runs.
 export const Base64 = Schema.String.check(
-  Schema.isPattern(/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$/u),
+  Schema.makeFilter(
+    (value: string) => value.length % 4 === 0 && /^[A-Za-z0-9+/]*={0,2}$/u.test(value),
+    Schema.isPattern(/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$/u).annotations,
+  ),
 ).annotate({ identifier: "Prompt.Base64" })
 export type Base64 = typeof Base64.Type