diff --git a/tests/test_resolve_endpoint_fallbacks.py b/tests/test_resolve_endpoint_fallbacks.py
new file mode 100644
index 0000000..e77a83a
--- /dev/null
+++ b/tests/test_resolve_endpoint_fallbacks.py
@@ -0,0 +1,173 @@
+"""Regression tests for the real resolve_endpoint() fallback chain."""
+
+import json
+from types import SimpleNamespace
+
+import src.endpoint_resolver as endpoint_resolver
+from src.endpoint_resolver import resolve_endpoint
+
+
+class _FakeColumn:
+    def __init__(self, name):
+        self.name = name
+
+    def __eq__(self, value):
+        return ("eq", self.name, value)
+
+
+class _FakeModelEndpoint:
+    id = _FakeColumn("id")
+    is_enabled = _FakeColumn("is_enabled")
+
+
+class _FakeQuery:
+    def __init__(self, rows):
+        self.rows = list(rows)
+
+    def filter(self, *conditions):
+        for condition in conditions:
+            if isinstance(condition, tuple) and condition[0] == "eq":
+                _, field, value = condition
+                self.rows = [row for row in self.rows if getattr(row, field) == value]
+        return self
+
+    def first(self):
+        return self.rows[0] if self.rows else None
+
+
+class _FakeDb:
+    def __init__(self, rows):
+        self.rows = rows
+
+    def query(self, model):
+        return _FakeQuery(self.rows)
+
+    def close(self):
+        pass
+
+
+def _endpoint(ep_id, model, *, hidden=None):
+    return SimpleNamespace(
+        id=ep_id,
+        base_url=f"https://{ep_id}.example/v1",
+        api_key=f"key-{ep_id}",
+        cached_models=json.dumps([model]),
+        hidden_models=json.dumps(hidden or []),
+        is_enabled=True,
+    )
+
+
+def _install_resolver_fakes(monkeypatch, settings, endpoints):
+    import src.settings as settings_mod
+
+    monkeypatch.setattr(settings_mod, "load_settings", lambda: settings)
+    monkeypatch.setattr(
+        settings_mod,
+        "get_user_setting",
+        lambda key, owner="", default=None: settings.get(key, default),
+    )
+    monkeypatch.setattr(endpoint_resolver, "ModelEndpoint", _FakeModelEndpoint)
+    monkeypatch.setattr(endpoint_resolver, "SessionLocal", lambda: _FakeDb(endpoints))
+    monkeypatch.setattr(endpoint_resolver, "resolve_url", lambda url: url)
+
+
+def test_utility_uses_default_when_utility_endpoint_unset(monkeypatch):
+    settings = {
+        "utility_endpoint_id": "",
+        "utility_model": "",
+        "default_endpoint_id": "default",
+        "default_model": "default-chat",
+    }
+    _install_resolver_fakes(monkeypatch, settings, [_endpoint("default", "default-chat")])
+
+    url, model, headers = resolve_endpoint("utility")
+
+    assert url == "https://default.example/v1/chat/completions"
+    assert model == "default-chat"
+    assert headers == {"Authorization": "Bearer key-default"}
+
+
+def test_task_uses_utility_when_task_endpoint_unset(monkeypatch):
+    settings = {
+        "task_endpoint_id": "",
+        "task_model": "",
+        "utility_endpoint_id": "utility",
+        "utility_model": "utility-chat",
+        "default_endpoint_id": "default",
+        "default_model": "default-chat",
+    }
+    _install_resolver_fakes(
+        monkeypatch,
+        settings,
+        [_endpoint("utility", "utility-chat"), _endpoint("default", "default-chat")],
+    )
+
+    url, model, headers = resolve_endpoint("task")
+
+    assert url == "https://utility.example/v1/chat/completions"
+    assert model == "utility-chat"
+    assert headers == {"Authorization": "Bearer key-utility"}
+
+
+def test_research_uses_default_when_research_and_utility_unset(monkeypatch):
+    settings = {
+        "research_endpoint_id": "",
+        "research_model": "",
+        "utility_endpoint_id": "",
+        "utility_model": "",
+        "default_endpoint_id": "default",
+        "default_model": "default-chat",
+    }
+    _install_resolver_fakes(monkeypatch, settings, [_endpoint("default", "default-chat")])
+
+    url, model, headers = resolve_endpoint("research")
+
+    assert url == "https://default.example/v1/chat/completions"
+    assert model == "default-chat"
+    assert headers == {"Authorization": "Bearer key-default"}
+
+
+def test_returns_explicit_fallback_when_no_endpoint_id_configured(monkeypatch):
+    settings = {
+        "task_endpoint_id": "",
+        "task_model": "",
+        "utility_endpoint_id": "",
+        "utility_model": "",
+        "default_endpoint_id": "",
+        "default_model": "",
+    }
+    fallback = ("https://fallback.example/chat", "fallback-chat", {"X-Test": "fallback"})
+    _install_resolver_fakes(monkeypatch, settings, [])
+
+    assert resolve_endpoint(
+        "task",
+        fallback_url=fallback[0],
+        fallback_model=fallback[1],
+        fallback_headers=fallback[2],
+    ) == fallback
+
+
+def test_hidden_configured_model_selects_first_enabled_chat_model(monkeypatch):
+    settings = {
+        "default_endpoint_id": "default",
+        "default_model": "hidden-chat",
+    }
+    endpoint = SimpleNamespace(
+        id="default",
+        base_url="https://default.example/v1",
+        api_key="key-default",
+        cached_models=json.dumps([
+            "hidden-chat",
+            "text-embedding-3-small",
+            "enabled-chat",
+        ]),
+        hidden_models=json.dumps(["hidden-chat"]),
+        is_enabled=True,
+    )
+    _install_resolver_fakes(monkeypatch, settings, [endpoint])
+
+    url, model, headers = resolve_endpoint("default")
+
+    assert url == "https://default.example/v1/chat/completions"
+    assert model == "enabled-chat"
+    assert headers == {"Authorization": "Bearer key-default"}