fix(nodes): raise error when response is entirely think-block content

When a reasoning model returns a response consisting solely of
<think>...</think> content, the emptiness guard fired before
strip_think_content ran, so the node silently returned an empty
string rather than signalling an error. Add a post-strip check
in both LMStudioTextGen and LMStudioImageToText that raises
ValueError if strip_think_content reduces the text to nothing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

image_to_text_node.py

@@ -187,6 +187,10 @@ class LMStudioImageToText(io.ComfyNode):
                 )
 
         text = strip_think_content(text)
+        if not text:
+            raise ValueError(
+                "All content was inside <think> blocks; no visible text was produced."
+            )
 
         status = f"Model '{connection.model}' via {via_endpoint} (seed={resolved_seed})."
         if fallback_reason:

tests/test_image_to_text_node.py

@@ -158,3 +158,38 @@ 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_raises_when_all_text_is_think_blocks(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """
+    Regression: when the model returns only <think> content (no visible text),
+    strip_think_content reduces the response to "". The node must raise
+    ValueError rather than silently returning an empty string.
+    """
+    image_node = _image_module()
+
+    fake_client = SimpleNamespace(
+        responses=SimpleNamespace(
+            create=lambda **_: SimpleNamespace(output_text="<think>internal only</think>")
+        ),
+        chat=SimpleNamespace(
+            completions=SimpleNamespace(
+                create=lambda **_: (_ for _ in ()).throw(
+                    AssertionError("chat fallback should not run")
+                )
+            )
+        ),
+    )
+    monkeypatch.setattr(image_node, "resolve_request_seed", lambda _: 1)
+    monkeypatch.setattr(image_node, "create_openai_client", lambda **_: fake_client)
+
+    with pytest.raises(ValueError, match="All content was inside <think> blocks"):
+        image_node.LMStudioImageToText.execute(
+            connection=_connection_payload(),
+            image=_single_image(),
+            system_prompt="sys",
+            user_prompt="describe",
+            seed=1,
+        )

tests/test_text_gen_node.py

@@ -168,3 +168,38 @@ def test_execute_raises_if_both_endpoints_return_no_text(
             user_prompt="hello",
             seed=1,
         )
+
+
+def test_execute_raises_when_all_text_is_think_blocks(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """
+    Regression: when the model returns only <think> content (no visible text),
+    strip_think_content reduces the response to "". The node must raise
+    ValueError rather than silently returning an empty string.
+    """
+    text_gen_node = _text_module()
+
+    fake_client = SimpleNamespace(
+        responses=SimpleNamespace(
+            create=lambda **_: SimpleNamespace(output_text="<think>internal only</think>")
+        ),
+        chat=SimpleNamespace(
+            completions=SimpleNamespace(
+                create=lambda **_: (_ for _ in ()).throw(
+                    AssertionError("chat fallback should not run")
+                )
+            )
+        ),
+    )
+
+    monkeypatch.setattr(text_gen_node, "resolve_request_seed", lambda _: 1)
+    monkeypatch.setattr(text_gen_node, "create_openai_client", lambda **_: fake_client)
+
+    with pytest.raises(ValueError, match="All content was inside <think> blocks"):
+        text_gen_node.LMStudioTextGen.execute(
+            connection=_connection_payload(),
+            system_prompt="sys",
+            user_prompt="hello",
+            seed=1,
+        )

text_gen_node.py

@@ -149,6 +149,10 @@ class LMStudioTextGen(io.ComfyNode):
                 raise ValueError("chat.completions fallback returned no text output")
 
         text = strip_think_content(text)
+        if not text:
+            raise ValueError(
+                "All content was inside <think> blocks; no visible text was produced."
+            )
 
         status = f"Model '{connection.model}' via {via_endpoint} (seed={resolved_seed})."
         if fallback_reason: