diff --git a/agent.py b/agent.py
index dc0c5c7..7a3121c 100644
--- a/agent.py
+++ b/agent.py
@@ -972,7 +972,7 @@ async def _write_iter_manifest(ctx: RunContext[Any], manifest: dict[str, Any]) -
         out_dir = OUTPUT_DIR
         name = f"iter-plan-" + datetime.now(timezone.utc).strftime("%Y%m%dT%H%M%SZ") + ".json"
         path = f"{out_dir}/{name}"
-        await ctx.workspace.write(path, json.dumps(manifest, ensure_ascii=False, indent=2).encode("utf-8"))
+        ctx.workspace.write_bytes(path, json.dumps(manifest, ensure_ascii=False, indent=2).encode("utf-8"))
         return path
     except Exception:  # noqa: BLE001
         return ""