fix(llm): skip Anthropic effort kwarg on non-supporting models (#831)

Haiku 4.5 rejects the effort parameter with 400. AnthropicClient.get_llm()
now drops effort when the model isn't in the supported set (Opus 4.5+,
Sonnet 4.5+, mythos-preview). Forward-compat regex catches future
claude-{opus,sonnet}-X-Y releases automatically; Haiku and unknown
models stay excluded conservatively.

14 tests cover Haiku exclusion, current Opus/Sonnet inclusion, future-
version inheritance via pattern, mythos-preview, unknown-default
exclusion, and other passthrough kwargs surviving the effort-skip path.

tests/test_anthropic_effort.py

@@ -0,0 +1,84 @@
+"""Tests for Anthropic effort-parameter gating (#831).
+
+Haiku 4.5 (and current Haiku versions) reject the ``effort`` parameter
+with a 400. Opus 4.5+ and Sonnet 4.5+ accept it. The gate uses a
+forward-compat regex so future ``claude-{opus,sonnet}-X-Y`` releases
+inherit support automatically.
+"""
+
+import pytest
+
+from tradingagents.llm_clients import anthropic_client as mod
+
+
+def _capture_kwargs(monkeypatch):
+    captured: dict = {}
+    monkeypatch.setattr(
+        mod, "NormalizedChatAnthropic",
+        lambda **kwargs: captured.setdefault("kwargs", kwargs),
+    )
+    return captured
+
+
+@pytest.mark.unit
+class TestEffortGate:
+    @pytest.mark.parametrize(
+        "model",
+        ["claude-haiku-4-5", "claude-haiku-5-0", "claude-haiku-4-7-preview"],
+    )
+    def test_haiku_does_not_receive_effort(self, monkeypatch, model):
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(model=model, effort="medium", api_key="x").get_llm()
+        assert "effort" not in captured["kwargs"]
+
+    @pytest.mark.parametrize(
+        "model",
+        [
+            "claude-opus-4-5", "claude-opus-4-6", "claude-opus-4-7",
+            "claude-sonnet-4-5", "claude-sonnet-4-6",
+        ],
+    )
+    def test_current_opus_and_sonnet_receive_effort(self, monkeypatch, model):
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(model=model, effort="high", api_key="x").get_llm()
+        assert captured["kwargs"]["effort"] == "high"
+
+    @pytest.mark.parametrize(
+        "model",
+        ["claude-opus-5-0", "claude-opus-4-8", "claude-sonnet-5-0"],
+    )
+    def test_future_opus_sonnet_inherit_effort_via_pattern(self, monkeypatch, model):
+        """Forward-compat: new Opus/Sonnet versions don't need a code change."""
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(model=model, effort="low", api_key="x").get_llm()
+        assert captured["kwargs"]["effort"] == "low"
+
+    def test_mythos_preview_receives_effort(self, monkeypatch):
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(
+            model="claude-mythos-preview", effort="medium", api_key="x"
+        ).get_llm()
+        assert captured["kwargs"]["effort"] == "medium"
+
+    def test_unknown_anthropic_model_does_not_receive_effort(self, monkeypatch):
+        """Default is conservative — unknown models don't get effort to avoid 400s."""
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(
+            model="claude-experimental-x", effort="medium", api_key="x"
+        ).get_llm()
+        assert "effort" not in captured["kwargs"]
+
+    def test_other_kwargs_still_forwarded_when_effort_skipped(self, monkeypatch):
+        """Skipping effort must not break other passthrough kwargs."""
+        captured = _capture_kwargs(monkeypatch)
+        mod.AnthropicClient(
+            model="claude-haiku-4-5",
+            effort="medium",
+            api_key="placeholder",
+            max_tokens=1024,
+            timeout=30,
+        ).get_llm()
+        assert captured["kwargs"]["api_key"] == "placeholder"
+        assert captured["kwargs"]["max_tokens"] == 1024
+        assert captured["kwargs"]["timeout"] == 30
+        assert "effort" not in captured["kwargs"]