llm_worker_rs/docs/research/openresponses_mapping.md

Open Responses mapping (llm_client -> Open Responses)

This document maps the current llm_client event model to Open Responses items and streaming events. It focuses on output streaming; input items are noted where they are the closest semantic match.

Legend

• OR item: Open Responses item types used in response.output.
• OR event: Open Responses streaming events (response.*).
• Note: Gaps or required adaptation decisions.

Response lifecycle / meta events

llm_client	Open Responses	Note
StatusEvent::Started	response.created, response.queued, response.in_progress	OR has finer-grained lifecycle states; pick a subset or map Started -> response.in_progress.
StatusEvent::Completed	response.completed
StatusEvent::Failed	response.failed
StatusEvent::Cancelled	(no direct event)	Could map to response.incomplete or response.failed depending on semantics.
UsageEvent	response.completed payload usage	OR reports usage on the response object, not as a dedicated streaming event.
ErrorEvent	error event	OR has a dedicated error streaming event.
PingEvent	(no direct event)	OR does not define a heartbeat event.

Output block lifecycle

Text block

llm_client	Open Responses	Note
BlockStart { block_type: Text, metadata: Text }	response.output_item.added with item type message (assistant)	OR output items are message/function_call/reasoning. This creates the message item.
BlockDelta { delta: Text(..) }	response.output_text.delta	Text deltas map 1:1 to output text deltas.
BlockStop { block_type: Text }	response.output_text.done + response.content_part.done + response.output_item.done	OR emits separate done events for content parts and items.

Tool use (function call)

llm_client	Open Responses	Note
BlockStart { block_type: ToolUse, metadata: ToolUse { id, name } }	response.output_item.added with item type function_call	OR uses call_id + name + arguments string. Map id -> call_id.
BlockDelta { delta: InputJson(..) }	response.function_call_arguments.delta	OR spec does not explicitly require argument deltas; treat as OpenAI-compatible extension if adopted.
BlockStop { block_type: ToolUse }	response.function_call_arguments.done + response.output_item.done	Item status can be set to completed or incomplete.

Tool result (function call output)

llm_client	Open Responses	Note
BlockStart { block_type: ToolResult, metadata: ToolResult { tool_use_id } }	Input item function_call_output	OR treats tool results as input items, not output items. This is a request-side mapping.
BlockDelta	(no direct output event)	OR does not stream tool output deltas as response events.
BlockStop	(no direct output event)	Tool output lives on the next request as an input item.

Thinking / reasoning

llm_client	Open Responses	Note
BlockStart { block_type: Thinking, metadata: Thinking }	response.output_item.added with item type reasoning	OR models reasoning as a separate item type.
BlockDelta { delta: Thinking(..) }	response.reasoning.delta	OR has dedicated reasoning delta events.
BlockStop { block_type: Thinking }	response.reasoning.done	OR separates reasoning summary events (response.reasoning_summary_*) from reasoning deltas. Decide whether Thinking maps to full reasoning or summary only.

Stop reasons

llm_client StopReason	Open Responses	Note
EndTurn	response.completed + item status completed
MaxTokens	response.incomplete + item status incomplete
StopSequence	response.completed
ToolUse	response.completed for message item, followed by function_call output item	OR models tool call as a separate output item.

Gaps / open decisions

• PingEvent has no OR equivalent. If needed, keep as internal only.
• Cancelled status needs a policy: map to response.incomplete or response.failed.
• OR has response.refusal.delta / response.refusal.done. llm_client has no refusal delta type; consider adding a new block or delta variant if needed.
• OR splits item and content part lifecycles. llm_client currently has a single block lifecycle, so mapping should decide whether to synthesize content_part.* events or ignore them.
• The OR specification does not state how function_call.arguments stream deltas; response.function_call_arguments.* should be treated as a compatible extension if required.