diff --git a/CHANGELOG.md b/CHANGELOG.md
index 28e247ae..2f2bb3aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   * `.extract_data()` is now supported.
   *  `async` methods are now supported. (#81)
   * Fixed an issue with more than one session being active at once. (#83)
+* `ChatAnthropic()` no longer choke after receiving an output that consists only of whitespace. (#86)
 
 ### Changes
 
diff --git a/chatlas/_anthropic.py b/chatlas/_anthropic.py
index 1d09b7dd..3c21cfe9 100644
--- a/chatlas/_anthropic.py
+++ b/chatlas/_anthropic.py
@@ -451,7 +451,10 @@ def _as_message_params(self, turns: list[Turn]) -> list["MessageParam"]:
     @staticmethod
     def _as_content_block(content: Content) -> "ContentBlockParam":
         if isinstance(content, ContentText):
-            return {"text": content.text, "type": "text"}
+            text = content.text
+            if text == "" or text.isspace():
+                text = "[empty string]"
+            return {"type": "text", "text": text}
         elif isinstance(content, ContentJson):
             return {"text": "<structured data/>", "type": "text"}
         elif isinstance(content, ContentPDF):
diff --git a/chatlas/types/openai/_submit.py b/chatlas/types/openai/_submit.py
index 75efd761..a7137d48 100644
--- a/chatlas/types/openai/_submit.py
+++ b/chatlas/types/openai/_submit.py
@@ -44,6 +44,10 @@ class SubmitInputArgs(TypedDict, total=False):
             "gpt-4.1-2025-04-14",
             "gpt-4.1-mini-2025-04-14",
             "gpt-4.1-nano-2025-04-14",
+            "o4-mini",
+            "o4-mini-2025-04-16",
+            "o3",
+            "o3-2025-04-16",
             "o3-mini",
             "o3-mini-2025-01-31",
             "o1",
@@ -125,7 +129,7 @@ class SubmitInputArgs(TypedDict, total=False):
         openai.NotGiven,
     ]
     seed: Union[int, None, openai.NotGiven]
-    service_tier: Union[Literal["auto", "default"], None, openai.NotGiven]
+    service_tier: Union[Literal["auto", "default", "flex"], None, openai.NotGiven]
     stop: Union[str, None, list[str], openai.NotGiven]
     store: Union[bool, None, openai.NotGiven]
     stream: Union[Literal[False], None, Literal[True], openai.NotGiven]
diff --git a/tests/test_provider_anthropic.py b/tests/test_provider_anthropic.py
index f6862ce6..e4ae1b64 100644
--- a/tests/test_provider_anthropic.py
+++ b/tests/test_provider_anthropic.py
@@ -89,3 +89,10 @@ def test_anthropic_images():
 def test_anthropic_pdfs():
     chat_fun = ChatAnthropic
     assert_pdf_local(chat_fun)
+
+
+def test_anthropic_empty_response():
+    chat = ChatAnthropic()
+    chat.chat("Respond with only two blank lines")
+    resp = chat.chat("What's 1+1? Just give me the number")
+    assert "2" == str(resp).strip()