fix(providers): guard chat_with_retry against explicit None max_tokens (#3102)

nanobot/providers/base.py

@@ -512,10 +512,14 @@ class LLMProvider(ABC):
         on_retry_wait: Callable[[str], Awaitable[None]] | None = None,
     ) -> LLMResponse:
         """Call chat_stream() with retry on transient provider failures."""
-        if max_tokens is self._SENTINEL:
+        if max_tokens is self._SENTINEL or max_tokens is None:
             max_tokens = self.generation.max_tokens
-        if temperature is self._SENTINEL:
+        if max_tokens is None:
+            max_tokens = GenerationSettings.max_tokens
+        if temperature is self._SENTINEL or temperature is None:
             temperature = self.generation.temperature
+        if temperature is None:
+            temperature = GenerationSettings.temperature
         if reasoning_effort is self._SENTINEL:
             reasoning_effort = self.generation.reasoning_effort
 
@@ -549,12 +553,20 @@ class LLMProvider(ABC):
 
         Parameters default to ``self.generation`` when not explicitly passed,
         so callers no longer need to thread temperature / max_tokens /
-        reasoning_effort through every layer.
+        reasoning_effort through every layer. Explicit ``None`` is also
+        normalized to the provider's generation defaults, with a final fallback
+        to :class:`GenerationSettings` class defaults so that downstream
+        ``_build_kwargs`` never sees ``None`` for ``max_tokens`` / ``temperature``
+        (which would crash ``max(1, max_tokens)``).
         """
-        if max_tokens is self._SENTINEL:
+        if max_tokens is self._SENTINEL or max_tokens is None:
             max_tokens = self.generation.max_tokens
-        if temperature is self._SENTINEL:
+        if max_tokens is None:
+            max_tokens = GenerationSettings.max_tokens
+        if temperature is self._SENTINEL or temperature is None:
             temperature = self.generation.temperature
+        if temperature is None:
+            temperature = GenerationSettings.temperature
         if reasoning_effort is self._SENTINEL:
             reasoning_effort = self.generation.reasoning_effort