Group of 2 Under the hood
Assistant messages for tool results now include how long the tool call took (toolDuration)
What
After a tool call completes (including after PostToolUse hooks run), the resulting message now carries a toolDuration field with the tool's name and how long it took, in milliseconds. These per-call durations feed into a toolDurations array that gets aggregated elsewhere, such as in request payloads and session statistics.
Why This gives visibility into how long individual tool calls take, supporting reporting and aggregation of tool performance across a session.