diff --git a/nanobot/providers/anthropic_provider.py b/nanobot/providers/anthropic_provider.py
index 2cd252846..082d1e408 100644
--- a/nanobot/providers/anthropic_provider.py
+++ b/nanobot/providers/anthropic_provider.py
@@ -41,12 +41,7 @@ _ADAPTIVE_ONLY_MIN_VERSIONS = {
     "fable": (5, 0),
     "mythos": (5, 0),
 }
-_SAMPLING_DEPRECATED_MIN_VERSIONS = {
-    "opus": (4, 7),
-    "sonnet": (5, 0),
-    "fable": (5, 0),
-    "mythos": (5, 0),
-}
+_SAMPLING_DEPRECATED_MODELS = {"claude-mythos-preview"}
 
 
 def _model_version_at_least(
@@ -596,8 +591,10 @@ class AnthropicProvider(LLMProvider):
         reasoning_effort_lower = reasoning_effort.lower() if reasoning_effort else None
         thinking_enabled = reasoning_effort_lower not in (None, "", "none")
         adaptive_only = _model_version_at_least(model_name, _ADAPTIVE_ONLY_MIN_VERSIONS)
-        omit_temperature = _model_version_at_least(
-            model_name, _SAMPLING_DEPRECATED_MIN_VERSIONS
+        # Mythos Preview rejects sampling parameters but still accepts manual
+        # thinking budgets, so it is not part of the adaptive-only capability.
+        omit_temperature = (
+            adaptive_only or model_name.lower() in _SAMPLING_DEPRECATED_MODELS
         )
 
         kwargs: dict[str, Any] = {
diff --git a/tests/providers/test_anthropic_thinking.py b/tests/providers/test_anthropic_thinking.py
index be36c20a9..cbc823930 100644
--- a/tests/providers/test_anthropic_thinking.py
+++ b/tests/providers/test_anthropic_thinking.py
@@ -147,6 +147,13 @@ def test_sonnet_5_omits_temperature_none() -> None:
     assert "thinking" not in kw
 
 
+def test_mythos_preview_omits_temperature_but_keeps_manual_budget() -> None:
+    kw = _build(_make_provider("claude-mythos-preview"), "high", max_tokens=4096)
+    assert "temperature" not in kw
+    assert kw["thinking"] == {"type": "enabled", "budget_tokens": 8192}
+    assert "extra_body" not in kw
+
+
 @pytest.mark.parametrize("reasoning_effort", [None, "adaptive", "low", "medium", "high", "xhigh", "max"])
 def test_opus_5_omits_temperature(reasoning_effort: str | None) -> None:
     kw = _build(_make_provider("claude-opus-5"), reasoning_effort)