# 015 — LogPreview: selectable parameter columns

## Summary

The README's LogPreview spec says it should be possible to pick which parameters are
visible as columns, alongside the always-visible sequence/timestamp. Currently
LogPreview only shows sequence, timestamp, and raw text.

## Scope

- Extend the logs API/DTO ([004](004-metrics-api.md) territory, but specifically the
  existing `GET /api/logs`) to include derived param values per log line, sourced
  from [001](001-param-declarations.md)'s declarations applied to that line.
- Frontend: column picker UI in/near LogPreview; selected columns persist (localStorage
  is fine for a per-viewer preference, or fold into settings if it should be shared —
  pick localStorage unless product direction says otherwise).

## Acceptance criteria

- Declared params with a match on a given log line appear as selectable, populated
  columns in LogPreview.
- Column selection persists across a page reload.

## Depends on

- [001 — Param declarations](001-param-declarations.md)
- [004 — Metrics API](004-metrics-api.md) (for the pattern of extending log query
  responses)