diff --git a/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py b/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
index 6c07b89..17138ae 100644
--- a/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
+++ b/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
@@ -85,7 +85,7 @@ async def debug_agent(
         retrieval_log_id=rag_result.retrieval_log_id,
         tool_trace=rag_result.tool_trace,
     )
-    result = ModelClientService.debug_model(
+    result = await ModelClientService.debug_model_async(
         model,
         rag_result,
         {
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/model_service.py b/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
index aa2d463..5e88090 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import asyncio
 import json
 from dataclasses import dataclass
 from typing import Any
@@ -93,6 +94,11 @@ class ModelClientService:
             "knowledgeIds": rag_result.knowledge_ids,
         }
 
+    @staticmethod
+    async def debug_model_async(model: ModelConfig, rag_result: RagResult, overrides: dict[str, Any]) -> dict[str, Any]:
+        """Run the blocking provider client outside the ASGI event loop."""
+        return await asyncio.to_thread(ModelClientService.debug_model, model, rag_result, overrides)
+
 
 def _mock_answer(rag_result: RagResult) -> str:
     if not rag_result.is_hit:
diff --git a/ai_knowledge_base_v2/apps/backend/tests/test_production_readiness.py b/ai_knowledge_base_v2/apps/backend/tests/test_production_readiness.py
index 8d5f1de..12ed9f4 100644
--- a/ai_knowledge_base_v2/apps/backend/tests/test_production_readiness.py
+++ b/ai_knowledge_base_v2/apps/backend/tests/test_production_readiness.py
@@ -3,6 +3,7 @@ from __future__ import annotations
 from datetime import date
 import asyncio
 import json
+import time
 
 import pytest
 import httpx
@@ -22,6 +23,7 @@ from app.services.chat_service import ChatService
 from app.services.secret_service import ENCRYPTED_PREFIX, MASKED_SECRET, SecretService
 from app.services.security_state_service import SecurityStateService
 from app.services.auth_service import AuthService
+from app.services.model_service import ModelClientService
 from app.core.observability import RequestObservabilityMiddleware
 
 
@@ -138,6 +140,26 @@ def test_request_id_is_returned_without_breaking_response():
     assert response.json() == {"ok": True}
 
 
+def test_agent_debug_model_call_does_not_block_event_loop(monkeypatch):
+    def blocking_debug(*_args, **_kwargs):
+        time.sleep(0.15)
+        return {"ok": True}
+
+    monkeypatch.setattr(ModelClientService, "debug_model", blocking_debug)
+
+    async def verify_concurrency():
+        started = time.perf_counter()
+        task = asyncio.create_task(ModelClientService.debug_model_async(object(), object(), {}))
+        await asyncio.sleep(0.02)
+        event_loop_delay = time.perf_counter() - started
+        result = await task
+        return event_loop_delay, result
+
+    delay, result = asyncio.run(verify_concurrency())
+    assert delay < 0.10
+    assert result == {"ok": True}
+
+
 def test_readiness_reports_dependency_state(monkeypatch):
     from app.api import health
 
diff --git a/ai_knowledge_base_v2/apps/user-client/src/components/ChatComposer.vue b/ai_knowledge_base_v2/apps/user-client/src/components/ChatComposer.vue
index e819310..dd6cf69 100644
--- a/ai_knowledge_base_v2/apps/user-client/src/components/ChatComposer.vue
+++ b/ai_knowledge_base_v2/apps/user-client/src/components/ChatComposer.vue
@@ -23,14 +23,23 @@ function resize() {
   element.style.overflowY = element.scrollHeight > 108 ? "auto" : "hidden";
 }
 
-function send() {
+async function send() {
   const text = input.value.trim();
   if (!text) return;
+  // Sending has been accepted by the composer. Clear immediately instead of
+  // keeping the submitted text visible until the entire AI stream finishes.
+  input.value = "";
+  await nextTick();
+  resize();
   emit("send", text, async (success) => {
-    if (!success) return;
-    input.value = "";
-    await nextTick();
-    resize();
+    // Restore only when the parent rejected/failed the request and the user has
+    // not entered replacement text in the meantime.
+    if (!success && !input.value) {
+      input.value = text;
+      await nextTick();
+      resize();
+      textarea.value?.focus();
+    }
   });
 }