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loopctl

`src/stream.rs` — stream events and the accumulator

The neutral event vocabulary every provider speaks, and the folding machine that turns events into a finished message.

Key items

  • StreamEvent — MessageStart, PartStart { index, part }, IndexedDelta { index, delta }, PartStop { index }, MessageDelta { stop_reason, usage }, MessageStop, Ping.
  • DeltaPart — Text, InputJson (tool-argument fragments), ToolCall (legacy), Thinking (stream-only; empty = redacted reasoning).
  • StreamAccumulator — process(event), build() -> Message, usage(), peek_parts().
  • StreamStopReason — ToolCall, MaxTokens, StopSequence, EndTurn; from_api_str maps provider spellings; should_continue_tool_loop() is true only for ToolCall.
  • Usage { input_tokens, output_tokens } + total_tokens().
  • StreamError::InvalidToolInputJson — the accumulator’s only error.

Behavior notes

  • The lifecycle order is a contract: MessageStart → (PartStart → deltas → PartStop)* → MessageDelta → MessageStop. Never a synthetic MessageStop on failure — its absence is the truncation signal.
  • Routing is by the (index, lane-kind) pair — indices are reused across text/thinking/tool lanes on some wires.
  • Empty tool input becomes {}; still-open lanes at build() are dropped; thinking flushes nothing.

Deep dive: Stream events.