test: use sloth photo URL for vision test, add Anthropic remote URL support

studio/backend/core/inference/external_provider.py

@@ -187,6 +187,15 @@ class ExternalProviderClient:
                                     "data": b64data,
                                 },
                             })
+                        else:
+                            # Remote URL — Anthropic supports url source type natively
+                            anthropic_parts.append({
+                                "type": "image",
+                                "source": {
+                                    "type": "url",
+                                    "url": url,
+                                },
+                            })
                 filtered.append({"role": msg["role"], "content": anthropic_parts})
             else:
                 filtered.append(msg)

studio/backend/tests/test_providers_api.py

@@ -450,11 +450,8 @@ class TestProviderInference:
 
 # ── TestVisionInference ─────────────────────────────────────────────
 
-# 1×1 white PNG — minimal valid image to test vision routing
-_WHITE_PNG_B64 = (
-    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQ"
-    "DwADhQGAWjR9awAAAABJRU5ErkJggg=="
-)
+# Sloth photo — used to test vision routing across providers
+_VISION_IMAGE_URL = "https://www.travelexcellence.com/images/where-to-see-sloths-in-costa-rica.jpg"
 
 _VISION_PARAMS = [
     pytest.param(
@@ -487,14 +484,14 @@ class TestVisionInference:
         model: str,
         api_key: str,
     ):
-        """Image + text message → non-empty streamed reply."""
+        """Image URL + text message → non-empty streamed reply."""
         encrypted = encrypt_key(api_key)
         payload = {
             "messages": [{
                 "role": "user",
                 "content": [
-                    {"type": "text", "text": "What colour is this image? Reply in one word."},
-                    {"type": "image_url", "image_url": {"url": f"data:image/png;base64,{_WHITE_PNG_B64}"}},
+                    {"type": "text", "text": "Which animal is in this image? Reply in one word."},
+                    {"type": "image_url", "image_url": {"url": _VISION_IMAGE_URL}},
                 ],
             }],
             "stream": True,