diff --git a/src/auto-reply/reply/session.ts b/src/auto-reply/reply/session.ts
index 0a0594ddd9..4d08ddb061 100644
--- a/src/auto-reply/reply/session.ts
+++ b/src/auto-reply/reply/session.ts
@@ -126,7 +126,11 @@ export async function initSessionState(params: {
   const sessionScope = sessionCfg?.scope ?? "per-sender";
   const storePath = resolveStorePath(sessionCfg?.store, { agentId });
 
-  const sessionStore: Record<string, SessionEntry> = loadSessionStore(storePath);
+  // CRITICAL: Skip cache to ensure fresh data when resolving session identity.
+  // Stale cache (especially with multiple gateway processes or on Windows where
+  // mtime granularity may miss rapid writes) can cause incorrect sessionId
+  // generation, leading to orphaned transcript files. See #17971.
+  const sessionStore: Record<string, SessionEntry> = loadSessionStore(storePath, { skipCache: true });
   let sessionKey: string | undefined;
   let sessionEntry: SessionEntry;