Problem

When viewing an infinite time range (inf) without a valid smallest_time_grain, the derived activeTimeGrain can be set to TIME_GRAIN_SECOND. Since TIME_GRAIN_SECOND, TIME_GRAIN_MILLISECOND, and TIME_GRAIN_UNSPECIFIED were missing from the TIME_GRAIN record, this caused runtime failures in UI code that performed lookups (e.g., formatting, pivot chip labels).

Solution

Core fix: Add missing grain entries to TIME_GRAIN record.

Additional cleanup:

• Replace redundant FromURLParamTimeGrainMap / ToURLParamTimeGrainMapMap with existing DateTimeUnitToV1TimeGrain / V1TimeGrainToDateTimeUnit from new-grains.ts
• Use effectiveGrain (respects minTimeGrain) instead of raw activeTimeGrain in time series charts
• Refactor getAdjustedFetchTime to use Luxon directly instead of legacy helper functions
• Add formatDateTimeByGrain utility for grain-aware datetime formatting

Changes

Core fix

config.ts, types.ts

Add MILLISECOND, SECOND, UNSPECIFIED to TIME_GRAIN record and Period enum

Mapper consolidation

mappers.ts, time-state.ts, TDDHeader.svelte, selectors.ts, + 6 url-state files

Remove duplicate mappers, use V1TimeGrainToDateTimeUnit throughout

Time series

MetricsTimeSeriesCharts.svelte, timeseries-data-store.ts

Use effectiveGrain with isGrainAllowed guard

Utilities

formatter.ts, ranges/index.ts, new-grains.ts

Add formatDateTimeByGrain, simplify getAdjustedFetchTime

Tests

formatter.spec.ts

Add 12 tests for formatDateTimeByGrain

Technical debt

This is a targeted fix. The underlying issue is type fragmentation across TIME_GRAIN, V1TimeGrain, AvailableTimeGrain, Period, and TimeUnit—all of which duplicate Luxon's DateTimeUnit. A TODO comment documents the path forward: consolidate around Luxon utilities per the pattern in new-grains.ts.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!