502s and upstream connection errors (envoy proxy failures) from ChatGPT
were not being retried. This classifies them as LLMConnectionError (retryable)
in both the streaming and non-streaming paths, and adds retry handling in
the non-streaming HTTPStatusError handler so 502s get the same exponential
backoff treatment as transport-level connection drops.
🐾 Generated with [Letta Code](https://letta.com)
Co-authored-by: Letta <noreply@letta.com>
- Map httpx.ReadError/WriteError/ConnectError to LLMConnectionError in
handle_llm_error so Temporal correctly classifies them as retryable
(previously fell through to generic non-retryable LLMError)
- Add client-level retry with exponential backoff (up to 3 attempts) on
request_async and stream_async for transient transport errors
- Stream retry is guarded by has_yielded flag to avoid corrupting
partial responses already consumed by the caller
Multiple OpenAI-compatible LLM clients (Azure, Deepseek, Groq, Together, XAI, ZAI)
and Anthropic-compatible clients (Anthropic, MiniMax, Google Vertex) were overriding
request_async/stream_async without calling sanitize_unicode_surrogates, causing
UnicodeEncodeError when message content contained lone UTF-16 surrogates.
Root cause: Child classes override parent methods but omit the sanitization step that
the base OpenAIClient includes. This allows corrupted Unicode (unpaired surrogates
from malformed emoji) to reach the httpx layer, which rejects it during UTF-8 encoding.
Fix: Import and call sanitize_unicode_surrogates in all overridden request methods.
Also removed duplicate sanitize_unicode_surrogates definition from openai_client.py
that shadowed the canonical implementation in letta.helpers.json_helpers.
🐾 Generated with [Letta Code](https://letta.com)
Co-Authored-By: Letta <noreply@letta.com>
Issue-ID: 10c0f2e4-f87b-11f0-b91c-da7ad0900000
