From e5b39b319ea324ae3fe9e8bf9f7d65787f9050be Mon Sep 17 00:00:00 2001
From: Adam Weidman <adamfweidman@google.com>
Date: Tue, 12 May 2026 15:03:17 -0400
Subject: [PATCH] fix(core): restore fallback serialization in content-utils to
 avoid throwing

---
 packages/core/src/agent/content-utils.ts | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/packages/core/src/agent/content-utils.ts b/packages/core/src/agent/content-utils.ts
index 50d054ff0e..42b0b7fec7 100644
--- a/packages/core/src/agent/content-utils.ts
+++ b/packages/core/src/agent/content-utils.ts
@@ -93,12 +93,13 @@ export function contentPartsToGeminiParts(content: ContentPart[]): Part[] {
         // References are converted to text for the model
         result.push({ text: part.text });
         break;
-      default: {
-        ((x: never) => {
-          throw new Error(`Unhandled ContentPart type: ${JSON.stringify(x)}`);
-        })(part);
+      default:
+        debugLogger.warn(
+          `Unhandled ContentPart type: ${JSON.stringify(part)} fallback to serialization`,
+        );
+        // Serialize unknown ContentPart variants instead of dropping them
+        result.push({ text: JSON.stringify(part) });
         break;
-      }
     }
   }
   return result;