diff --git a/tests/tui_gateway/test_make_agent_provider.py b/tests/tui_gateway/test_make_agent_provider.py
new file mode 100644
index 0000000000..bdc7fecf4d
--- /dev/null
+++ b/tests/tui_gateway/test_make_agent_provider.py
@@ -0,0 +1,48 @@
+"""Regression test for #11884: _make_agent must resolve runtime provider.
+
+Without resolve_runtime_provider(), bare-slug models in config
+(e.g. ``claude-opus-4-6`` with ``model.provider: anthropic``) leave
+provider/base_url/api_key empty in AIAgent, causing HTTP 404.
+"""
+
+from unittest.mock import MagicMock, patch
+
+
+def test_make_agent_passes_resolved_provider():
+    """_make_agent forwards provider/base_url/api_key/api_mode from
+    resolve_runtime_provider to AIAgent."""
+
+    fake_runtime = {
+        "provider": "anthropic",
+        "base_url": "https://api.anthropic.com",
+        "api_key": "sk-test-key",
+        "api_mode": "anthropic_messages",
+        "command": None,
+        "args": None,
+        "credential_pool": None,
+    }
+
+    fake_cfg = {
+        "model": {"default": "claude-opus-4-6", "provider": "anthropic"},
+        "agent": {"system_prompt": "test"},
+    }
+
+    with patch("tui_gateway.server._load_cfg", return_value=fake_cfg), \
+         patch("tui_gateway.server._get_db", return_value=MagicMock()), \
+         patch("tui_gateway.server._load_tool_progress_mode", return_value="compact"), \
+         patch("tui_gateway.server._load_reasoning_config", return_value=None), \
+         patch("tui_gateway.server._load_service_tier", return_value=None), \
+         patch("tui_gateway.server._load_enabled_toolsets", return_value=None), \
+         patch("hermes_cli.runtime_provider.resolve_runtime_provider", return_value=fake_runtime) as mock_resolve, \
+         patch("run_agent.AIAgent") as mock_agent:
+
+        from tui_gateway.server import _make_agent
+        _make_agent("sid-1", "key-1")
+
+        mock_resolve.assert_called_once_with(requested=None)
+
+        call_kwargs = mock_agent.call_args
+        assert call_kwargs.kwargs["provider"] == "anthropic"
+        assert call_kwargs.kwargs["base_url"] == "https://api.anthropic.com"
+        assert call_kwargs.kwargs["api_key"] == "sk-test-key"
+        assert call_kwargs.kwargs["api_mode"] == "anthropic_messages"
diff --git a/tui_gateway/server.py b/tui_gateway/server.py
index d86db00066..536136e2d3 100644
--- a/tui_gateway/server.py
+++ b/tui_gateway/server.py
@@ -911,12 +911,21 @@ def _reset_session_agent(sid: str, session: dict) -> dict:
 
 def _make_agent(sid: str, key: str, session_id: str | None = None):
     from run_agent import AIAgent
+    from hermes_cli.runtime_provider import resolve_runtime_provider
     cfg = _load_cfg()
     system_prompt = cfg.get("agent", {}).get("system_prompt", "") or ""
     if not system_prompt:
         system_prompt = _resolve_personality_prompt(cfg)
+    runtime = resolve_runtime_provider(requested=None)
     return AIAgent(
         model=_resolve_model(),
+        provider=runtime.get("provider"),
+        base_url=runtime.get("base_url"),
+        api_key=runtime.get("api_key"),
+        api_mode=runtime.get("api_mode"),
+        acp_command=runtime.get("command"),
+        acp_args=runtime.get("args"),
+        credential_pool=runtime.get("credential_pool"),
         quiet_mode=True,
         verbose_logging=_load_tool_progress_mode() == "verbose",
         reasoning_config=_load_reasoning_config(),