Messages Api And Streaming Sse

Claude API streams a response to POST /v1/messages with stream=true. The client buffers events out of order because TCP delivered content_block_delta frames before content_block_start.

Parser must enforce SSE event ordering per docs: message_start → (content_block_start → content_block_delta* → content_block_stop)+ → message_delta → message_stop. Reject content_block_delta that arrives before the matching content_block_start with index N — do not emit synthetic blocks.

Mid-stream Claude emits a ping event (event: ping). The downstream client's JSON-only parser treats it as malformed and disconnects.

Treat ping as a keep-alive: ignore for content accumulation, reset read deadline, continue parsing. Do not surface to caller as content; do not abort the stream.

Agent calls /v1/messages with max_tokens=512 for a long generation task. Response has stop_reason=max_tokens and an obviously truncated final content block.

Detect stop_reason=max_tokens and either (a) raise to caller as a partial completion, or (b) issue a continuation request appending the truncated assistant message and a 'continue' user turn. Never present the partial as a complete answer.