# 012 — Metrics UI

## Summary

Replace the current "Coming Soon" Metrics placeholder with a real component: declare
metrics via the metric language, and view their derived values.

## Scope

- A form/editor for declaring a metric (regex + param matchers) that calls
  `POST /api/metrics` ([004](004-metrics-api.md)), with inline validation errors
  surfaced from the API's 4xx responses.
- List of currently-declared metrics with their labels.
- A view of a selected metric's bucket values over the active time range (reuse the
  time-range plumbing already in `App.tsx`/`LogTimeline`).

## Acceptance criteria

- Declaring a metric in the UI immediately reflects newly-matching logs (existing
  and new) in the metric's value view, per the backfill behavior from
  [003](003-metric-bucket-derivation.md).
- Invalid metric definitions show the backend's validation error instead of failing
  silently.

## Depends on

- [004 — Metrics API](004-metrics-api.md)