fix(providers): widen omit_temperature to cover opus-4-8 and fable

The temperature suppression was hardcoded to only match opus-4-7. Newer
Anthropic models (opus-4-8, fable) also reject the parameter with a 400.

Normalize model_name to lowercase before matching so mixed-case configs
do not fall through.  Add tests for opus-4-8 and fable across adaptive,
enabled, and no-thinking paths, plus a negative test confirming ordinary
models still send temperature.

Fixes #4333

nanobot/providers/anthropic_provider.py

@@ -452,9 +452,10 @@ class AnthropicProvider(LLMProvider):
         max_tokens = max(1, max_tokens)
         thinking_enabled = bool(reasoning_effort) and reasoning_effort.lower() != "none"
 
-        # claude-opus-4-7 deprecated the `temperature` parameter entirely — the
-        # API returns 400 if it is present, on any code path.
-        omit_temperature = "opus-4-7" in model_name
+        # Several Anthropic models (opus-4-7, opus-4-8, fable) deprecated the
+        # `temperature` parameter — the API returns 400 if it is present.
+        _model_lower = model_name.lower()
+        omit_temperature = any(m in _model_lower for m in ("opus-4-7", "opus-4-8", "fable"))
 
         kwargs: dict[str, Any] = {
             "model": model_name,

tests/providers/test_anthropic_thinking.py

@@ -85,6 +85,41 @@ def test_opus_4_7_omits_temperature_none() -> None:
     assert "thinking" not in kw
 
 
+def test_opus_4_8_omits_temperature_adaptive() -> None:
+    kw = _build(_make_provider("claude-opus-4-8"), "adaptive")
+    assert "temperature" not in kw
+
+
+def test_opus_4_8_omits_temperature_enabled() -> None:
+    kw = _build(_make_provider("claude-opus-4-8"), "high", max_tokens=4096)
+    assert "temperature" not in kw
+
+
+def test_opus_4_8_omits_temperature_none() -> None:
+    kw = _build(_make_provider("claude-opus-4-8"), None)
+    assert "temperature" not in kw
+
+
+def test_fable_omits_temperature_adaptive() -> None:
+    kw = _build(_make_provider("claude-fable-1"), "adaptive")
+    assert "temperature" not in kw
+
+
+def test_fable_omits_temperature_enabled() -> None:
+    kw = _build(_make_provider("claude-fable-1"), "high", max_tokens=4096)
+    assert "temperature" not in kw
+
+
+def test_fable_omits_temperature_none() -> None:
+    kw = _build(_make_provider("claude-fable-1"), None)
+    assert "temperature" not in kw
+
+
+def test_ordinary_model_sends_temperature() -> None:
+    kw = _build(_make_provider("claude-sonnet-4-6"), None)
+    assert kw["temperature"] == 0.7
+
+
 def test_reasoning_effort_string_none_does_not_enable_thinking() -> None:
     """reasoning_effort='none' must not enable thinking — treated same as disabled."""
     kw = _build(_make_provider(), "none")