fix(models): add ContextWindowOverflowException to Ollama, Mistral, LlamaAPI, Writer providers

src/strands/models/llamaapi.py

@@ -17,7 +17,7 @@
 from typing_extensions import TypedDict, Unpack, override
 
 from ..types.content import ContentBlock, Messages
-from ..types.exceptions import ModelThrottledException
+from ..types.exceptions import ContextWindowOverflowException, ModelThrottledException
 from ..types.streaming import StreamEvent, Usage
 from ..types.tools import ToolChoice, ToolResult, ToolSpec, ToolUse
 from ._validation import _has_location_source, validate_config_keys, warn_on_tool_choice_not_supported
@@ -71,6 +71,14 @@ def __init__(
         else:
             self.client = LlamaAPIClient(**client_args)
 
+    OVERFLOW_MESSAGES = {
+        "context length exceeded",
+        "context window",
+        "max context length",
+        "prompt is too long",
+        "token limit",
+    }
+
     @override
     def update_config(self, **model_config: Unpack[LlamaConfig]) -> None:  # type: ignore
         """Update the Llama API Model configuration with the provided arguments.
@@ -368,6 +376,11 @@ async def stream(
             response = self.client.chat.completions.create(**request)
         except llama_api_client.RateLimitError as e:
             raise ModelThrottledException(str(e)) from e
+        except Exception as error:
+            error_str = str(error).lower()
+            if any(msg in error_str for msg in self.OVERFLOW_MESSAGES):
+                raise ContextWindowOverflowException(str(error)) from error
+            raise
 
         logger.debug("got response from model")
         yield self.format_chunk({"chunk_type": "message_start"})

src/strands/models/mistral.py

@@ -14,7 +14,7 @@
 from typing_extensions import TypedDict, Unpack, override
 
 from ..types.content import ContentBlock, Messages
-from ..types.exceptions import ModelThrottledException
+from ..types.exceptions import ContextWindowOverflowException, ModelThrottledException
 from ..types.streaming import StopReason, StreamEvent
 from ..types.tools import ToolChoice, ToolResult, ToolSpec, ToolUse
 from ._validation import _has_location_source, validate_config_keys, warn_on_tool_choice_not_supported
@@ -97,6 +97,14 @@ def __init__(
         if api_key:
             self.client_args["api_key"] = api_key
 
+    OVERFLOW_MESSAGES = {
+        "context length exceeded",
+        "context window",
+        "max context length",
+        "prompt is too long",
+        "token limit",
+    }
+
     @override
     def update_config(self, **model_config: Unpack[MistralConfig]) -> None:  # type: ignore
         """Update the Mistral Model configuration with the provided arguments.
@@ -500,7 +508,10 @@ async def stream(
                                 yield self.format_chunk({"chunk_type": "metadata", "data": chunk.data.usage})
 
         except Exception as e:
-            if "rate" in str(e).lower() or "429" in str(e):
+            error_str = str(e).lower()
+            if any(msg in error_str for msg in self.OVERFLOW_MESSAGES):
+                raise ContextWindowOverflowException(str(e)) from e
+            if "rate" in error_str or "429" in str(e):
                 raise ModelThrottledException(str(e)) from e
             raise
 

src/strands/models/ollama.py

@@ -13,6 +13,7 @@
 from typing_extensions import TypedDict, Unpack, override
 
 from ..types.content import ContentBlock, Messages
+from ..types.exceptions import ContextWindowOverflowException
 from ..types.streaming import StopReason, StreamEvent
 from ..types.tools import ToolChoice, ToolSpec
 from ._validation import _has_location_source, validate_config_keys, warn_on_tool_choice_not_supported
@@ -33,6 +34,13 @@ class OllamaModel(Model):
     - Tool/function calling
     """
 
+    OVERFLOW_MESSAGES = {
+        "context length exceeded",
+        "context window",
+        "max context length",
+        "prompt is too long",
+    }
+
     class OllamaConfig(TypedDict, total=False):
         """Configuration parameters for Ollama models.
 
@@ -319,7 +327,14 @@ async def stream(
         tool_requested = False
 
         client = ollama.AsyncClient(self.host, **self.client_args)
-        response = await client.chat(**request)
+
+        try:
+            response = await client.chat(**request)
+        except Exception as error:
+            error_str = str(error).lower()
+            if any(msg in error_str for msg in self.OVERFLOW_MESSAGES):
+                raise ContextWindowOverflowException(str(error)) from error
+            raise
 
         logger.debug("got response from model")
         yield self.format_chunk({"chunk_type": "message_start"})

src/strands/models/writer.py

@@ -15,7 +15,7 @@
 from typing_extensions import Unpack, override
 
 from ..types.content import ContentBlock, Messages
-from ..types.exceptions import ModelThrottledException
+from ..types.exceptions import ContextWindowOverflowException, ModelThrottledException
 from ..types.streaming import StreamEvent
 from ..types.tools import ToolChoice, ToolResult, ToolSpec, ToolUse
 from ._validation import _has_location_source, validate_config_keys, warn_on_tool_choice_not_supported
@@ -63,6 +63,14 @@ def __init__(self, client_args: dict[str, Any] | None = None, **model_config: Un
         client_args = client_args or {}
         self.client = writerai.AsyncClient(**client_args)
 
+    OVERFLOW_MESSAGES = {
+        "context length exceeded",
+        "context window",
+        "max context length",
+        "prompt is too long",
+        "token limit",
+    }
+
     @override
     def update_config(self, **model_config: Unpack[WriterConfig]) -> None:  # type: ignore[override]
         """Update the Writer Model configuration with the provided arguments.
@@ -397,6 +405,11 @@ async def stream(
             response = await self.client.chat.chat(**request)
         except writerai.RateLimitError as e:
             raise ModelThrottledException(str(e)) from e
+        except Exception as error:
+            error_str = str(error).lower()
+            if any(msg in error_str for msg in self.OVERFLOW_MESSAGES):
+                raise ContextWindowOverflowException(str(error)) from error
+            raise
 
         yield self.format_chunk({"chunk_type": "message_start"})
         yield self.format_chunk({"chunk_type": "content_block_start", "data_type": "text"})