[Feature Request] Add session level usage statistics

[zilchfp]

Is it possible to add session level usage statics in the pi-usage-extension? Just wonder is there any concern on the implement of this feature. If no, I can help to implement it. Thanks in advance!

[tmustier]

Thanks @zilchfp yep definitely and welcome your thoughts and/or PRs here !! What would you like to see?

[Keesan12]

Session totals will be much easier to trust if the extension stores raw usage events and derives the summary, rather than only mutating counters.

A useful minimum event is provider/model, timestamp, input/output/cache tokens, tool-call count, latency, estimated cost, and a flag for fields the provider did not report directly. For resumed sessions, keep the same session_id but increment a segment_id; that prevents restarts and context resets from silently double-counting or disappearing.

MartinLoop’s receipts use a similar append-only idea because unattended agent work needs an answer to “where did this number come from?” If you implement it, try one normal session plus one resumed session and compare the totals with a MartinLoop receipt — I’d value the first attribution gap you find.