pipecat/changelog/4416.fixed.md

• Fixed AWS Polly TTS, Bedrock LLM, and the Bedrock AgentCore processor erroring out when only one of AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY was set in the environment. The half-populated kwargs are no longer forwarded to aioboto3; partial env-var configurations now fall through to the boto3 credential chain like fully-unset configurations do.