test(cron): cover provider "custom" → providers.custom resolution

Add execution-time coverage that bare `provider="custom"` resolves a literal
providers.custom endpoint (and still falls through when none exists), plus
creation-time coverage that `_resolve_model_override` keeps a resolvable
"custom" and only pins the main provider when it is unresolvable.

tests/tools/test_cronjob_tools.py

@@ -452,3 +452,54 @@ class TestUnifiedCronjobTool:
         assert updated["success"] is True
         stored = get_job(created["job_id"])
         assert stored["deliver"] == "telegram"
+
+
+# =========================================================================
+# Per-job model/provider override resolution
+# =========================================================================
+
+from tools.cronjob_tools import _resolve_model_override  # noqa: E402
+
+
+class TestResolveModelOverride:
+    """`_resolve_model_override` must not silently hijack a job that meant to
+    use a configured custom endpoint (e.g. ``providers.custom`` → cliproxy).
+    Regression for cron jobs with ``provider: "custom"`` falling back to codex.
+    """
+
+    def test_keeps_bare_custom_when_a_named_entry_exists(self, monkeypatch):
+        import hermes_cli.runtime_provider as rp_mod
+
+        monkeypatch.setattr(rp_mod, "has_named_custom_provider", lambda name: True)
+        provider, model = _resolve_model_override(
+            {"provider": "custom", "model": "gpt-5.4"}
+        )
+        assert provider == "custom"
+        assert model == "gpt-5.4"
+
+    def test_pins_main_provider_when_bare_custom_unresolvable(self, monkeypatch):
+        import hermes_cli.config as cfg_mod
+        import hermes_cli.runtime_provider as rp_mod
+
+        monkeypatch.setattr(rp_mod, "has_named_custom_provider", lambda name: False)
+        monkeypatch.setattr(
+            cfg_mod, "load_config", lambda: {"model": {"provider": "openai-codex"}}
+        )
+        provider, model = _resolve_model_override(
+            {"provider": "custom", "model": "gpt-5.4"}
+        )
+        # No matching custom entry → fall back to pinning the main provider.
+        assert provider == "openai-codex"
+        assert model == "gpt-5.4"
+
+    def test_keeps_explicit_custom_name_unchanged(self, monkeypatch):
+        import hermes_cli.runtime_provider as rp_mod
+
+        # Even if the resolver claims no entry, the canonical "custom:<name>"
+        # form is never stripped or pinned.
+        monkeypatch.setattr(rp_mod, "has_named_custom_provider", lambda name: False)
+        provider, model = _resolve_model_override(
+            {"provider": "custom:cliproxy", "model": "gpt-5.4"}
+        )
+        assert provider == "custom:cliproxy"
+        assert model == "gpt-5.4"