Event types

Completion and agent streams share model-generation events, but agent events add runtime turns, tool execution, and final run state.

Completion events

Event	Contains
text_delta	Incremental visible text.
reasoning_delta	Provider reasoning content when available.
tool_call_delta	Provisional tool name or argument fragments.
tool_call	A completed model tool request.
source	A provider-reported source.
provider_tool_call	A tool executed by the provider.
message_id	The provider message identifier.
final	The normalized completion response.
error	A provider or stream failure with optional usage.

Local tool calls in a direct completion stream are data only; they are not executed by the helper.

Agent events

Event	Contains
turn_start	Turn number, current prompt, and history.
generation_start	The provider-facing normalized request and model information.
text_delta	Incremental visible assistant text.
reasoning_delta	Provider reasoning content when available.
tool_call_delta	Provisional local tool-call data.
tool_call	A completed local tool request.
tool_result	Tool name, call IDs, arguments, and text result.
source	A provider-reported source.
provider_tool_call	A provider-executed tool record.
agent_tool_event	A nested event from an agent used as a tool.
turn_end	The completed provider response and optional first-delta timing.
final	Run ID, output, usage, messages, and optional trace or provider artifacts.
error	The failure and cumulative authoritative usage.

Choose what each surface receives

Internal operations tools may need full events. User-facing clients usually need only safe text, generic tool status, a final result, and a stable error message.