Investigate: should TodoWrite allow marking multiple todos complete in one call?

Question to investigate

Should TodoWrite support marking multiple todos as complete in a single tool call, rather than requiring one call per status update?

Context

Today, when several adjacent steps finish together (e.g. during a setup phase, or when a task wraps up multiple sub-steps at once), the assistant has to issue separate TodoWrite calls to flip each todo from in_progress → completed. The work was conceptually one transition but is split across many tool invocations.

What to investigate

• How often do real sessions have batches of "complete several at once" transitions vs. one-at-a-time? (Telemetry would tell.)
• Trade-offs of batching: simpler/shorter tool traces, fewer round trips — vs. the discipline of "mark each one done as soon as it's done" that the current single-update pattern enforces (which the system prompt explicitly encourages).
• Whether allowing batches would lead the model to defer completion updates and lose the granularity that makes the todo list useful as a progress signal.
• Whether the right answer is API-level support, or just better prompting around the current one-at-a-time pattern.

This is an investigation, not a feature request — the right outcome might be "leave it as is."