fix(anthropic): say what Anthropic documents in the sampling parameter deprecation warning

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Bug fixes
 
+* The deprecation warning for `temperature`, `top_p` and `top_k` on `ChatAnthropic()` no longer says these parameters have no effect on current models. Anthropic's deprecation page says Claude 4.7 and later models return a 400 error when they are set to a non-default value, and that API version 2026-10-21 removes them for every model; the warning now says so. What is forwarded is unchanged.
 * `ChatOllama()` can now be created without a `model`, so `ChatOllama().list_models()` works. Sending a message without a model still raises an error that lists the available models. (#166)
 * `ChatGoogle()` now reports `finish_reason == "content_filter"` for Gemini's `IMAGE_SAFETY`, `IMAGE_PROHIBITED_CONTENT`, `IMAGE_RECITATION` and `LANGUAGE` finish reasons, instead of passing the raw Gemini string through, and reports `"tool_use"` (rather than `"success"`) when a turn ends with a tool request, as `ChatOpenAI()` does. (#473)
 * The error raised for a tool request with invalid JSON arguments from `ChatOpenAI()` and `ChatOpenAICompletions()` (and the providers built on them) now shows the offending arguments, instead of the literal text `{args}`.

chatlas/_provider_anthropic.py

@@ -799,15 +799,20 @@ def translate_model_params(self, params: StandardModelParams) -> "SubmitInputArg
         res: "SubmitInputArgs" = {}
 
         # anthropic>=1.0 removed these sampling parameters from the request
-        # schema; current models ignore them. Forward them via `extra_body`
-        # so older models that still honor them keep working.
+        # schema; Claude 4.7 and later reject non-default values with a 400.
+        # Forward them via `extra_body` so older models that still honor them
+        # keep working.
         removed = [p for p in ("temperature", "top_p", "top_k") if p in params]
         if removed:
             warnings.warn(
-                f"The {', '.join(removed)} sampling parameter(s) no longer have "
-                "an effect on current Anthropic models. They are forwarded via "
-                "`extra_body` for older models that still honor them; this "
-                "forwarding is deprecated and will be removed in a future release.",
+                f"The {', '.join(removed)} sampling parameter(s) are deprecated by "
+                "Anthropic: Claude 4.7 and later models return a 400 error when they "
+                "are set to a non-default value, and API version 2026-10-21 removes "
+                "them for every model "
+                "(https://platform.claude.com/docs/en/about-claude/model-deprecations). "
+                "They are forwarded via `extra_body` for older models that still "
+                "honor them; this forwarding is deprecated and will be removed in a "
+                "future release.",
                 DeprecationWarning,
                 stacklevel=2,
             )

tests/test_set_model_params.py

@@ -169,7 +169,10 @@ def test_translate_model_params_anthropic():
         "stop_sequences": ["STOP"],
     }
 
-    with pytest.warns(DeprecationWarning, match="no longer have an effect"):
+    with pytest.warns(
+        DeprecationWarning,
+        match="return a 400 error when they are set to a non-default value",
+    ):
         result = provider.translate_model_params(params)
 
     expected = {
@@ -517,7 +520,10 @@ def test_anthropic_model_params_integration():
     )
 
     # Test that provider.translate_model_params converts them correctly
-    with pytest.warns(DeprecationWarning, match="no longer have an effect"):
+    with pytest.warns(
+        DeprecationWarning,
+        match="return a 400 error when they are set to a non-default value",
+    ):
         provider_args = chat.provider.translate_model_params(
             chat._standard_model_params
         )
@@ -564,3 +570,17 @@ def test_chat_kwargs_with_model_params():
     assert kwargs.get("max_tokens") == 100
     assert kwargs.get("frequency_penalty") == 0.1
     assert kwargs.get("presence_penalty") == 0.3  # Should override chat.chat_kwargs
+
+
+def test_anthropic_sampling_warning_cites_the_deprecation_page():
+    """The warning says what Anthropic documents: a 400 on Claude 4.7+, removal in 2026-10-21."""
+    provider = ChatAnthropic().provider
+
+    with pytest.warns(DeprecationWarning) as record:
+        provider.translate_model_params({"temperature": 0.7, "top_k": 50})
+
+    message = str(record[0].message)
+    assert message.startswith("The temperature, top_k sampling parameter(s)")
+    assert "Claude 4.7 and later" in message
+    assert "2026-10-21" in message
+    assert "no longer have an effect" not in message