diff --git a/harbor_cookbook/gepa/optimize.py b/harbor_cookbook/gepa/optimize.py
index 30ba3ce..b6cd588 100644
--- a/harbor_cookbook/gepa/optimize.py
+++ b/harbor_cookbook/gepa/optimize.py
@@ -26,6 +26,7 @@
     DEFAULT_ENVIRONMENT,
     DEFAULT_MODEL,
     download_tasks,
+    init_queue,
     run_trial,
     split_tasks,
 )
@@ -173,6 +174,8 @@ def main():
     _model_name = args.model
     _environment = args.environment
 
+    init_queue(n_concurrent=args.max_workers)
+
     logging.basicConfig(
         level=logging.INFO,
         format="%(asctime)s  %(levelname)-8s  %(message)s",
diff --git a/harbor_cookbook/gepa/utils.py b/harbor_cookbook/gepa/utils.py
index fb17491..ae705bb 100644
--- a/harbor_cookbook/gepa/utils.py
+++ b/harbor_cookbook/gepa/utils.py
@@ -9,6 +9,7 @@
 from collections import defaultdict
 from pathlib import Path
 
+from harbor import TrialQueue
 from harbor.models.environment_type import EnvironmentType
 from harbor.models.trial.config import (
     AgentConfig,
@@ -18,7 +19,6 @@
     VerifierConfig,
 )
 from harbor.registry.client import RegistryClientFactory
-from harbor.trial.trial import Trial
 
 log = logging.getLogger(__name__)
 
@@ -26,9 +26,14 @@
 DEFAULT_MODEL = "openai/gpt-5-nano"
 DEFAULT_ENVIRONMENT = EnvironmentType.DOCKER
 
-# Single event loop shared across GEPA worker threads.
 _loop = asyncio.new_event_loop()
 threading.Thread(target=_loop.run_forever, daemon=True).start()
+_queue: TrialQueue | None = None
+
+
+def init_queue(n_concurrent: int) -> None:
+    global _queue
+    _queue = TrialQueue(n_concurrent=n_concurrent)
 
 
 def download_tasks():
@@ -106,7 +111,7 @@ def run_trial(
         )
 
         log.debug("Starting trial for %s", task_dir.name)
-        result = asyncio.run_coroutine_threadsafe(Trial(config).run(), _loop).result()
+        result = asyncio.run_coroutine_threadsafe(_queue.submit(config), _loop).result()
 
         rewards = result.verifier_result.rewards if result.verifier_result else {}
         exc = result.exception_info