Chat: route image sessions only to matching image endpoints

Co-authored-by: ghreprimand <203024559+ghreprimand@users.noreply.github.com>

tests/test_chat_image_routing.py

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+import json
+from types import SimpleNamespace
+
+from routes import chat_routes
+
+
+class _FakeQuery:
+    def __init__(self, rows):
+        self.rows = rows
+
+    def filter(self, *conditions):
+        return self
+
+    def all(self):
+        return list(self.rows)
+
+
+class _FakeDb:
+    def __init__(self, rows):
+        self.rows = rows
+        self.closed = False
+
+    def query(self, model):
+        return _FakeQuery(self.rows)
+
+    def close(self):
+        self.closed = True
+
+
+def _session(model="qwen3.5:latest", endpoint_url="http://localhost:11434/v1/chat/completions"):
+    return SimpleNamespace(model=model, endpoint_url=endpoint_url)
+
+
+def _endpoint(base_url, model_type="image", models=None):
+    cached_models = None if models is None else json.dumps(models)
+    return SimpleNamespace(
+        base_url=base_url,
+        model_type=model_type,
+        is_enabled=True,
+        cached_models=cached_models,
+    )
+
+
+def test_image_model_prefix_routes_to_image_generation_without_endpoint_lookup(monkeypatch):
+    def fail_if_called():
+        raise AssertionError("prefixed image models should not need a DB lookup")
+
+    monkeypatch.setattr(chat_routes, "SessionLocal", fail_if_called)
+
+    assert chat_routes._is_image_generation_session(_session(model="dall-e-3"))
+
+
+def test_image_endpoint_does_not_catch_text_model_on_different_path(monkeypatch):
+    db = _FakeDb([
+        _endpoint("http://localhost:11434/v1/images", models=["sdxl-local"]),
+    ])
+    monkeypatch.setattr(chat_routes, "SessionLocal", lambda: db)
+
+    assert not chat_routes._is_image_generation_session(_session())
+    assert db.closed
+
+
+def test_image_endpoint_cache_must_contain_selected_model(monkeypatch):
+    db = _FakeDb([
+        _endpoint("http://localhost:11434/v1", models=["sdxl-local"]),
+    ])
+    monkeypatch.setattr(chat_routes, "SessionLocal", lambda: db)
+
+    assert not chat_routes._is_image_generation_session(_session(model="qwen3.5:latest"))
+
+
+def test_matching_image_endpoint_routes_selected_image_model(monkeypatch):
+    db = _FakeDb([
+        _endpoint("http://localhost:11434/v1", models=["sdxl-local"]),
+    ])
+    monkeypatch.setattr(chat_routes, "SessionLocal", lambda: db)
+
+    assert chat_routes._is_image_generation_session(_session(model="sdxl-local"))