diff --git a/packages/workflow-agent-hermes/src/hermes.ts b/packages/workflow-agent-hermes/src/hermes.ts
index 3311da8..a8e9ff2 100644
--- a/packages/workflow-agent-hermes/src/hermes.ts
+++ b/packages/workflow-agent-hermes/src/hermes.ts
@@ -107,6 +107,13 @@ async function runHermes(ctx: AgentContext): Promise<AgentRunResult> {
       const { detailHash, output } = await storeHermesSessionDetail(store, session);
       return { output, detailHash };
     }
+    process.stderr.write(`uwf-hermes: session file not found for ${sessionId}\n`);
+  } else {
+    const stderrPreview = stderr.slice(0, 200).replace(/\n/g, "\\n");
+    const stdoutPreview = stdout.slice(0, 200).replace(/\n/g, "\\n");
+    process.stderr.write(
+      `uwf-hermes: no session_id parsed. stderr=${stderrPreview} stdout=${stdoutPreview}\n`,
+    );
   }
 
   const detailHash = await storeHermesRawOutput(store, stdout);