From 798691779beebe21eb2bcdccedbfde537fc7e092 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Wed, 27 May 2026 07:38:15 +0200
Subject: [PATCH] fix(agents): preserve sessions fallback errors

---
 src/agents/tools/sessions-send-tool.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/agents/tools/sessions-send-tool.ts b/src/agents/tools/sessions-send-tool.ts
index d34a013fc1a..1b7ebbbfa9b 100644
--- a/src/agents/tools/sessions-send-tool.ts
+++ b/src/agents/tools/sessions-send-tool.ts
@@ -231,7 +231,9 @@ async function startAgentRun(params: {
       } catch (err) {
         const queueSummary =
           formatEmbeddedPiQueueFailureSummary(queueOutcome) ?? "active run queue rejected";
-        throw new Error(`${queueSummary}; fallback_failed error=${formatErrorMessage(err)}`);
+        throw new Error(`${queueSummary}; fallback_failed error=${formatErrorMessage(err)}`, {
+          cause: err,
+        });
       }
     }
     const response = await params.callGateway<{ runId: string }>({