diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index f470e142a..648c4acef 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -74,6 +74,12 @@ _PROVIDER_ALIASES = {
     "minimax_cn": "minimax-cn",
     "claude": "anthropic",
     "claude-code": "anthropic",
+    "github": "copilot",
+    "github-copilot": "copilot",
+    "github-model": "copilot",
+    "github-models": "copilot",
+    "github-copilot-acp": "copilot-acp",
+    "copilot-acp-agent": "copilot-acp",
 }
 
 
@@ -89,10 +95,11 @@ def _normalize_aux_provider(provider: Optional[str]) -> str:
     if normalized == "main":
         # Resolve to the user's actual main provider so named custom providers
         # and non-aggregator providers (DeepSeek, Alibaba, etc.) work correctly.
-        main_prov = _read_main_provider()
+        main_prov = (_read_main_provider() or "").strip().lower()
         if main_prov and main_prov not in ("auto", "main", ""):
-            return main_prov
-        return "custom"
+            normalized = main_prov
+        else:
+            return "custom"
     return _PROVIDER_ALIASES.get(normalized, normalized)
 
 
diff --git a/tests/agent/test_auxiliary_client.py b/tests/agent/test_auxiliary_client.py
index b5b74bd30..1134f8348 100644
--- a/tests/agent/test_auxiliary_client.py
+++ b/tests/agent/test_auxiliary_client.py
@@ -19,6 +19,7 @@ from agent.auxiliary_client import (
     _read_codex_access_token,
     _get_provider_chain,
     _is_payment_error,
+    _normalize_aux_provider,
     _try_payment_fallback,
     _resolve_auto,
 )
@@ -54,6 +55,17 @@ def codex_auth_dir(tmp_path, monkeypatch):
     return codex_dir
 
 
+class TestNormalizeAuxProvider:
+    def test_maps_github_copilot_aliases(self):
+        assert _normalize_aux_provider("github") == "copilot"
+        assert _normalize_aux_provider("github-copilot") == "copilot"
+        assert _normalize_aux_provider("github-models") == "copilot"
+
+    def test_maps_github_copilot_acp_aliases(self):
+        assert _normalize_aux_provider("github-copilot-acp") == "copilot-acp"
+        assert _normalize_aux_provider("copilot-acp-agent") == "copilot-acp"
+
+
 class TestReadCodexAccessToken:
     def test_valid_auth_store(self, tmp_path, monkeypatch):
         hermes_home = tmp_path / "hermes"
diff --git a/tests/agent/test_auxiliary_named_custom_providers.py b/tests/agent/test_auxiliary_named_custom_providers.py
index 0f307d57f..5152428b6 100644
--- a/tests/agent/test_auxiliary_named_custom_providers.py
+++ b/tests/agent/test_auxiliary_named_custom_providers.py
@@ -100,6 +100,26 @@ class TestResolveProviderClientMainAlias:
         assert client is not None
         assert "beans.local" in str(client.base_url)
 
+    def test_main_resolves_github_copilot_alias(self, tmp_path):
+        _write_config(tmp_path, {
+            "model": {"default": "gpt-5.4", "provider": "github-copilot"},
+        })
+        with (
+            patch("hermes_cli.auth.resolve_api_key_provider_credentials", return_value={
+                "api_key": "ghu_test_token",
+                "base_url": "https://api.githubcopilot.com",
+            }),
+            patch("agent.auxiliary_client.OpenAI") as mock_openai,
+        ):
+            mock_openai.return_value = MagicMock()
+            from agent.auxiliary_client import resolve_provider_client
+
+            client, model = resolve_provider_client("main", "gpt-5.4")
+
+        assert client is not None
+        assert model == "gpt-5.4"
+        assert mock_openai.called
+
 
 class TestResolveProviderClientNamedCustom:
     """resolve_provider_client should resolve named custom providers directly."""