Keep map theme state aligned

CHANGELOG.md

@@ -22,6 +22,8 @@
   coverage without changing migrations or enabling automatic refresh.
 - Fixed map theme ranking so a newer official observation always wins over an
   older snapshot with a marginally larger feature count.
+- Restored the active map theme from the selected dataset when returning to the
+  Map workspace, keeping viewport queries, legends and zoom guidance aligned.
 
 ## Sprint 222 Official source edition probes (2026-07-16)
 

backend/tests/test_sprint223_governed_grb_refresh.py

@@ -258,3 +258,12 @@ def test_map_theme_ranking_prefers_newer_observation_over_feature_count() -> Non
     assert observed_sort < feature_tiebreaker
     assert "new Date(right.observed_at ?? 0).getTime()" in workspace
     assert "if (observedAtDifference !== 0) return observedAtDifference" in workspace
+
+
+def test_map_workspace_restores_theme_from_selected_dataset() -> None:
+    root = Path(__file__).resolve().parents[2]
+    workspace = (root / "frontend" / "src" / "components" / "map" / "MapWorkspace.tsx").read_text(encoding="utf-8")
+    assert "function themeIdForDataset(" in workspace
+    assert "useState<DataThemeId>(() =>" in workspace
+    assert "return themeIdForDataset(selectedDataset) ?? 'buildings'" in workspace
+    assert "const matchingThemeId = themeIdForDataset(selectedMapDataset)" in workspace

docs/CODEX_EXECUTION_LOG.md

@@ -9365,7 +9365,7 @@ Boundaries:
 Validation so far:
 - Backend compile and frontend typecheck passed.
 - Source-catalog plus governed-refresh focused suite passed: 20 tests.
-- Full `scripts/run_readiness_check.sh` passed: 780 backend tests, 110
+- Full `scripts/run_readiness_check.sh` passed: 781 backend tests, 110
   documented route contracts, one Alembic head, frontend typecheck/build and
   all packaged smoke checks.
 - Live Tower staging completed all 112 municipality/theme partitions for
@@ -9379,6 +9379,10 @@ Validation so far:
 - Live browser validation exposed and fixed additive theme ranking where two
   extra old water features could outweigh a newer observation date. Ranking is
   now priority, observation date, import date, then feature-count tie-breaker.
+- Post-deploy browser validation also exposed a stale map-theme remount state:
+  returning from Status to Map could retain the Water legend while the viewport
+  query and zoom guidance reverted to Buildings. Map state now initializes from
+  the selected persisted dataset so all four signals remain aligned.
 
 Next:
 - Run the full release gate, deploy to Tower, execute a live read-only plan and

frontend/src/components/map/MapWorkspace.tsx

@@ -308,6 +308,12 @@ function pickThemeDataset(
   return candidates[0] ?? null
 }
 
+function themeIdForDataset(dataset: DatasetCreateResponse | null): DataThemeId | null {
+  return dataset
+    ? DATA_THEMES.find((theme) => datasetMatchesTheme(dataset, theme))?.id ?? null
+    : null
+}
+
 function temporalSeriesLabel(items: DatasetCreateResponse[]): string {
   const configuredLabel = items.find((item) => typeof item.source_metadata?.['temporal_series_label'] === 'string')
     ?.source_metadata?.['temporal_series_label']
@@ -774,7 +780,10 @@ export function MapWorkspace({
   onClearQualityEvidence,
 }: MapWorkspaceProps): JSX.Element {
   const [advancedMode, setAdvancedMode] = useState(false)
-  const [activeThemeId, setActiveThemeId] = useState<DataThemeId>('buildings')
+  const [activeThemeId, setActiveThemeId] = useState<DataThemeId>(() => {
+    const selectedDataset = availableMapDatasets.find((dataset) => dataset.id === selectedMapDatasetId) ?? null
+    return themeIdForDataset(selectedDataset) ?? 'buildings'
+  })
   const {
     themeInsights,
     themeInsightsLoading: themeResultsLoading,
@@ -1093,9 +1102,9 @@ export function MapWorkspace({
     if (!selectedMapDataset) {
       return
     }
-    const matchingTheme = DATA_THEMES.find((theme) => datasetMatchesTheme(selectedMapDataset, theme))
-    if (matchingTheme) {
-      setActiveThemeId(matchingTheme.id)
+    const matchingThemeId = themeIdForDataset(selectedMapDataset)
+    if (matchingThemeId) {
+      setActiveThemeId(matchingThemeId)
     }
   }, [selectedMapDataset])