fix: include both endpoint errors when chat.completions fallback also fails

When the responses endpoint fails and the chat.completions fallback also
fails (raises or returns empty), the original responses error was captured
in fallback_reason but never surfaced. Wrap the fallback call in its own
try/except and re-raise a RuntimeError that chains both errors with
context, so users see why both endpoints failed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

image_to_text_node.py

@@ -164,21 +164,27 @@ class LMStudioImageToText(io.ComfyNode):
             first_image = image[0] if is_batch else image
             image_data_url = comfy_image_to_base64_png_url(first_image)
 
-            completion = client.chat.completions.create(
-                model=connection.model,
-                messages=build_chat_messages_with_image(
-                    system_prompt=system_prompt,
-                    user_prompt=user_prompt,
-                    image_data_url=image_data_url,
-                ),
-                seed=resolved_seed,
-                temperature=connection.temperature,
-                max_tokens=connection.max_tokens,
-                n=1,
-            )
-            text = extract_chat_completion_text(completion).strip()
-            if not text:
-                raise ValueError("chat.completions fallback returned no text output")
+            try:
+                completion = client.chat.completions.create(
+                    model=connection.model,
+                    messages=build_chat_messages_with_image(
+                        system_prompt=system_prompt,
+                        user_prompt=user_prompt,
+                        image_data_url=image_data_url,
+                    ),
+                    seed=resolved_seed,
+                    temperature=connection.temperature,
+                    max_tokens=connection.max_tokens,
+                    n=1,
+                )
+                text = extract_chat_completion_text(completion).strip()
+                if not text:
+                    raise ValueError("chat.completions fallback returned no text output")
+            except Exception as chat_error:
+                raise RuntimeError(
+                    f"Both endpoints failed. responses error: {fallback_reason}. "
+                    f"chat.completions error: {chat_error}"
+                ) from chat_error
 
             if batch_size > 1:
                 fallback_reason += (

tests/test_image_to_text_node.py

@@ -158,3 +158,41 @@ def test_execute_chat_fallback_reports_dropped_frames(
     assert "via chat.completions" in output.ui.text
     assert "responses unavailable" in output.ui.text
     assert "additional frame(s) were dropped" in output.ui.text
+
+
+def test_execute_chains_both_errors_when_chat_completions_also_raises(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    image_node = _image_module()
+
+    def raise_responses(**kwargs):
+        raise RuntimeError("responses boom")
+
+    def raise_chat(**kwargs):
+        raise RuntimeError("chat boom")
+
+    fake_client = SimpleNamespace(
+        responses=SimpleNamespace(create=raise_responses),
+        chat=SimpleNamespace(completions=SimpleNamespace(create=raise_chat)),
+    )
+    monkeypatch.setattr(image_node, "resolve_request_seed", lambda _: 41)
+    monkeypatch.setattr(image_node, "create_openai_client", lambda **_: fake_client)
+    monkeypatch.setattr(
+        image_node, "comfy_image_to_base64_png_url", lambda _img: "data:image/png;base64,xxx"
+    )
+
+    with pytest.raises(RuntimeError) as exc_info:
+        image_node.LMStudioImageToText.execute(
+            connection=_connection_payload(),
+            image=_single_image(),
+            system_prompt="sys",
+            user_prompt="describe",
+            seed=0,
+        )
+
+    message = str(exc_info.value)
+    assert "Both endpoints failed" in message
+    assert "responses boom" in message
+    assert "chat boom" in message
+    assert isinstance(exc_info.value.__cause__, RuntimeError)
+    assert str(exc_info.value.__cause__) == "chat boom"

tests/test_text_gen_node.py

@@ -161,10 +161,50 @@ def test_execute_raises_if_both_endpoints_return_no_text(
     monkeypatch.setattr(text_gen_node, "create_openai_client", lambda **_: fake_client)
     monkeypatch.setattr(text_gen_node, "resolve_request_seed", lambda _: 55)
 
-    with pytest.raises(ValueError, match="chat\\.completions fallback returned no text output"):
+    with pytest.raises(RuntimeError) as exc_info:
         text_gen_node.LMStudioTextGen.execute(
             connection=_connection_payload(),
             system_prompt="sys",
             user_prompt="hello",
             seed=1,
         )
+
+    message = str(exc_info.value)
+    assert "Both endpoints failed" in message
+    assert "responses endpoint returned no text output" in message
+    assert "chat.completions fallback returned no text output" in message
+
+
+def test_execute_chains_both_errors_when_chat_completions_also_raises(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    text_gen_node = _text_module()
+
+    def raise_responses(**kwargs):
+        raise RuntimeError("responses boom")
+
+    def raise_chat(**kwargs):
+        raise RuntimeError("chat boom")
+
+    fake_client = SimpleNamespace(
+        responses=SimpleNamespace(create=raise_responses),
+        chat=SimpleNamespace(completions=SimpleNamespace(create=raise_chat)),
+    )
+
+    monkeypatch.setattr(text_gen_node, "create_openai_client", lambda **_: fake_client)
+    monkeypatch.setattr(text_gen_node, "resolve_request_seed", lambda _: 55)
+
+    with pytest.raises(RuntimeError) as exc_info:
+        text_gen_node.LMStudioTextGen.execute(
+            connection=_connection_payload(),
+            system_prompt="sys",
+            user_prompt="hello",
+            seed=1,
+        )
+
+    message = str(exc_info.value)
+    assert "Both endpoints failed" in message
+    assert "responses boom" in message
+    assert "chat boom" in message
+    assert isinstance(exc_info.value.__cause__, RuntimeError)
+    assert str(exc_info.value.__cause__) == "chat boom"

text_gen_node.py

@@ -136,17 +136,23 @@ class LMStudioTextGen(io.ComfyNode):
             via_endpoint = "chat.completions"
             fallback_reason = str(responses_error)
 
-            completion = client.chat.completions.create(
-                model=connection.model,
-                messages=build_chat_messages(system_prompt, user_prompt),
-                seed=resolved_seed,
-                temperature=connection.temperature,
-                max_tokens=connection.max_tokens,
-                n=1,
-            )
-            text = extract_chat_completion_text(completion).strip()
-            if not text:
-                raise ValueError("chat.completions fallback returned no text output")
+            try:
+                completion = client.chat.completions.create(
+                    model=connection.model,
+                    messages=build_chat_messages(system_prompt, user_prompt),
+                    seed=resolved_seed,
+                    temperature=connection.temperature,
+                    max_tokens=connection.max_tokens,
+                    n=1,
+                )
+                text = extract_chat_completion_text(completion).strip()
+                if not text:
+                    raise ValueError("chat.completions fallback returned no text output")
+            except Exception as chat_error:
+                raise RuntimeError(
+                    f"Both endpoints failed. responses error: {fallback_reason}. "
+                    f"chat.completions error: {chat_error}"
+                ) from chat_error
 
         text = strip_think_content(text)