`_moa_prepared_request` is a private handshake between the conversation
loop and MoAChatCompletions.create. It is attached whenever
agent.provider == "moa", on the assumption that agent.client is still the
in-process MoA facade.
Credential rotation, provider fallback and dead-connection cleanup all
rebuild agent.client from _client_kwargs between attempts, and
pending_moa_prepared_request deliberately carries a prepared request
across exactly that boundary. The rebuilt client is a native OpenAI
client while provider stays "moa", so the key reaches an SDK that has
never heard of it:
TypeError: Completions.create() got an unexpected keyword argument
'_moa_prepared_request'
That error is non-retryable, so every remaining turn on the session
fails. Both dispatch paths are affected: the non-streaming one calls
agent.client directly, and _create_request_openai_client returns
agent.client unchanged for provider "moa".
Re-check the live client at the point the key is attached, which covers
both paths at once. When the facade is gone, send the prepared prompt
without the handshake and log the downgrade.