SDK: Add Responses API example to error handling guide

- Show try/except around LLM.responses()

Refs OpenHands/software-agent-sdk#980

Co-authored-by: openhands <[email protected]>

Author: enyst

sdk/guides/error-handling.mdx

@@ -68,6 +68,27 @@ except LLMError as e:
 
 The same exceptions are raised from both `LLM.completion()` and `LLM.responses()` paths.
 
+### Example: Using the Responses API
+
+```python icon="python"
+from pydantic import SecretStr
+from openhands.sdk import LLM
+from openhands.sdk.llm import Message, TextContent
+from openhands.sdk.llm.exceptions import LLMError, LLMContextWindowExceedError
+
+llm = LLM(model="claude-sonnet-4-20250514", api_key=SecretStr("your-key"))
+
+try:
+    resp = llm.responses([
+        Message.user([TextContent(text="Write a one-line haiku about code.")])
+    ])
+    print(resp.message)
+except LLMContextWindowExceedError:
+    print("Context window exceeded. Consider enabling a condenser.")
+except LLMError as e:
+    print(f"LLM error: {e}")
+```
+
 ## Using agents and conversations
 
 When you use `Agent` and `Conversation`, LLM exceptions propagate out of `conversation.run()` and `conversation.send_message(...)` if a condenser is not present.