Module sse 

Hand-rolled SSE framing (DW-075).

The locked M4 dependency decision is in-house framing: the text/event-stream wire format is small enough (a line grammar over a byte stream) that pulling an SSE crate — and the transitive futures-stack it would drag into the AI domain — buys nothing. This decoder implements the parts the provider dialects actually use:

• events are separated by a blank line (\n\n or \r\n\r\n),
• data: lines carry the payload (multiple data: lines in one event join with \n, per the WHATWG spec),
• event: names the event (Anthropic sends event: message_start alongside the data payload),
• id: and retry: lines are ignored, and :-prefixed comment lines are ignored,
• leading whitespace after the field name is stripped once.

What it deliberately does NOT do: charset negotiation, Last-Event-ID resumption (providers do not support it), or BOM sniffing — none of the shipped dialects use any of that.

Structs

SseDecoder

An incremental SSE decoder: feed it raw bytes as they arrive, take complete frames back. Call SseDecoder::finish at stream end to recover a final frame not terminated by a blank line (tolerant providers exist; a well-formed stream yields nothing there).

SseFrame

One decoded SSE event: its optional name and its data payload.