fix(cyclones): distinguish deliberate clears from feed eviction

changelog.d/847-cyclone-shared-selection.md

@@ -1,4 +1,4 @@
 - Explicit cyclone selections publish only the currently selected NHC/CPHC
-  storm into shared context. Switching storms evicts the previous identity
+  storm into shared context. Switching storms removes the previous identity
-  instead of leaving stale coordinates active (kvnloo, #847; reviewed by
+  without a false eviction event. Deliberate clears remain distinct from feed
-  quanticsoul4772).
+  disappearance (kvnloo, #847; reviewed by quanticsoul4772).

docs/CURRENT-STATE.md

@@ -394,6 +394,8 @@ with official advisory provenance and source position. Switching storms removes
 the prior record; automatic row selection never claims global context, and
 refreshes do not re-announce selection. Clearing or losing an explicitly selected
 storm removes shared context rather than assigning a fallback.
+Deliberate clear/disable reports `deliberate`; feed disappearance reports
+`evicted`. Switching storms selects the replacement before pruning the old record.
 Consult the linked official advisory for safety decisions.
 
 Voice and HUD snapshots reuse the existing feedState classifier. Analyst follow-ups retain their original data provenance; current-view results append provenance without replacing legacy fields. HUD context and deterministic telemetry include non-nominal feed state.

src/layers/cyclones/index.js

@@ -89,7 +89,9 @@ export function createCyclonesLayer({
   const notify = () => listener?.();
   const selected = () =>
     snapshot?.storms.find((storm) => storm.id === selectedId) || null;
-  function clearSelectedContext() {
+  function clearSelectedContext({ evicted = false } = {}) {
+    if (!evicted)
+      context?.clearSelectedEntityContextForLayer?.('weather-cyclones');
     context?.removeEntityContextsForLayer?.('weather-cyclones');
     selectedContextStormId = null;
     selectedContextEntity = null;
@@ -98,14 +100,11 @@ export function createCyclonesLayer({
   function publishSelectedContext({ announce = false } = {}) {
     const storm = selected();
     if (!storm || !context) {
-      if (!storm) clearSelectedContext();
+      if (!storm) clearSelectedContext({ evicted: true });
       return null;
     }
     selectedContextEntity ||= { show: true };
     const contextId = `cyclone:${storm.id}`;
-    context.removeEntityContextsForLayer?.('weather-cyclones', {
-      retainIds: new Set([contextId]),
-    });
     const record = context.registerEntityContext?.(selectedContextEntity, {
       id: contextId,
       layerId: 'weather-cyclones',
@@ -131,6 +130,9 @@ export function createCyclonesLayer({
     if (!record) return null;
     selectedContextStormId = storm.id;
     if (announce) context.selectEntityContext?.(selectedContextEntity);
+    context.removeEntityContextsForLayer?.('weather-cyclones', {
+      retainIds: new Set([contextId]),
+    });
     return record;
   }
 
@@ -302,7 +304,7 @@ export function createCyclonesLayer({
           snapshot = next;
           selectedId = null;
           ++navigationGeneration;
-          clearSelectedContext();
+          clearSelectedContext({ evicted: true });
           error = next.reason || ADVISORIES_UNAVAILABLE;
           return true;
         }
@@ -327,7 +329,7 @@ export function createCyclonesLayer({
         else rendering.setSelection(selectedId);
         if (selectedContextStormId) {
           if (selectedId === selectedContextStormId) publishSelectedContext();
-          else clearSelectedContext();
+          else clearSelectedContext({ evicted: true });
         }
         return true;
       } catch (cause) {
@@ -338,7 +340,7 @@ export function createCyclonesLayer({
         snapshot = null;
         selectedId = null;
         ++navigationGeneration;
-        clearSelectedContext();
+        clearSelectedContext({ evicted: true });
         return true;
       } finally {
         signal?.removeEventListener('abort', abort);

src/layers/cyclones/index.test.mjs

@@ -7,6 +7,7 @@ import {
   isPointerFree,
 } from '../../data/inputOwnership.js';
 import { isOwnedByOtherLayer } from '../../data/pickRegistry.js';
+import * as contextStore from '../../data/contextStore.js';
 
 const time = '2026-09-16T03:00:00.000Z';
 const storm = (id = 'ep152026') => ({
@@ -481,6 +482,64 @@ test('explicit cyclone selection publishes shared context without auto-claiming
   h.layer.destroy();
 });
 
+test('shared cyclone context distinguishes switches, deliberate clears and feed eviction', async (t) => {
+  const previousWindow = Object.getOwnPropertyDescriptor(globalThis, 'window');
+  const host = new EventTarget();
+  Object.defineProperty(globalThis, 'window', {
+    configurable: true,
+    value: host,
+  });
+  let h;
+  t.after(() => {
+    try {
+      h?.layer.destroy();
+    } finally {
+      if (previousWindow)
+        Object.defineProperty(globalThis, 'window', previousWindow);
+      else delete globalThis.window;
+    }
+  });
+  const events = [];
+  host.addEventListener('gev:entity-selected', ({ detail }) =>
+    events.push(['selected', detail.id]),
+  );
+  host.addEventListener('gev:entity-selection-cleared', ({ detail }) =>
+    events.push(['cleared', detail.reason]),
+  );
+  let next = snapshot([storm(), storm('ep162026')]);
+  h = harness({ getSnapshot: async () => next }, { context: contextStore });
+  h.layer.enable();
+  await h.layer.update();
+  h.layer.setParams({ stormId: 'ep152026' });
+  h.layer.setParams({ stormId: 'ep162026' });
+  assert.deepEqual(events, [
+    ['selected', 'cyclone:ep152026'],
+    ['selected', 'cyclone:ep162026'],
+  ]);
+  assert.deepEqual(
+    [...contextStore.getContextStore().entities.keys()],
+    ['cyclone:ep162026'],
+  );
+  await h.layer.update();
+  assert.equal(events.length, 2, 'refresh must not announce selection');
+
+  h.layer.setParams({ clear: true });
+  assert.deepEqual(events.at(-1), ['cleared', 'deliberate']);
+  assert.equal(contextStore.getContextStore().entities.size, 0);
+
+  h.layer.setParams({ stormId: 'ep162026' });
+  next = snapshot([storm()]);
+  await h.layer.update();
+  assert.deepEqual(events.at(-1), ['cleared', 'evicted']);
+  assert.equal(contextStore.getContextStore().entities.size, 0);
+  assert.equal(contextStore.getContextStore().selectedEntityId, null);
+
+  h.layer.setParams({ stormId: 'ep152026' });
+  h.layer.disable();
+  assert.deepEqual(events.at(-1), ['cleared', 'deliberate']);
+  assert.equal(contextStore.getContextStore().entities.size, 0);
+});
+
 test('refresh preserves selection intent, including explicit clears and missing storms', async () => {
   let next = snapshot([storm(), storm('ep162026')]);
   const h = harness({ getSnapshot: async () => next });