Streaming

Strem method

stream method output

Stream callback events (yielded per chunk)

Two event object families are used:

1. AssistantStreamMessageEvent

• :message_start
• :message_delta
• :message_end

Fields:

• type
• delta (hash; e.g. id/model/role/stop_reason updates)
• usage_increment (token deltas)

2. AssistantStreamEvent / subclasses

• Text:
  • :text_start
  • :text_delta
  • :text_end
• Tool call:
  • :tool_start (includes id, name)
  • :tool_delta
  • :tool_end
• Reasoning:
  • :reasoning_start
  • :reasoning_delta
  • :reasoning_end
• Thinking (enum-supported alias path):
  • :thinking_start
  • :thinking_delta
  • :thinking_end

Common fields:

• type
• content_index
• delta

Reasoning events also include:

• signature (on reasoning event struct)

• id

• model

• usage (input_tokens, output_tokens, reasoning_tokens, cache_creation_input_tokens, cache_read_input_tokens)

• role = "assistant"

• stop_reason ("stop" | "length" | "tool_use" | "toolUse" | "error" | "aborted")

• provider

• api

• error_message (optional)

• content array of typed blocks:

  • TextContent { type: "text", text: ... }
  • ReasoningContent { type: "reasoning", reasoning: ..., signature?: ... }
  • ToolCall { type: "tool_use", id:, name:, input: {...} }