Keep the analyst's last answer when the voice runner moves to another engine

A runner retired by an engine switch ends its in-flight writes but leaves the shared follow-up memory for the next engine's runner; ending the voice conversation still forgets it.

src/voice/gevActions.js

@@ -1554,10 +1554,15 @@ export function createGevActionRunner({
     conversation++;
     analystEngine?.reset();
   };
-  /** Voice was removed: nothing may run or write again. */
+  /**
-  runVoiceAction.dispose = () => {
+   * Voice was removed, or this runner's globe left (`keepMemory`: a host
+   * that shares the analyst's memory with the next runner keeps the last
+   * answer): nothing may run or write again.
+   */
+  runVoiceAction.dispose = ({ keepMemory = false } = {}) => {
     if (disposed) return;
-    runVoiceAction.resetConversation();
+    conversation++;
+    if (!keepMemory) analystEngine?.reset();
     disposed = true;
   };
   return runVoiceAction;

src/voice/integrationContract.test.mjs

@@ -352,3 +352,35 @@ test('the cloud prompt states precedence and caveat speech once', () => {
     /"approximately"\/"roughly" for a tool number/,
   );
 });
+
+test('an engine switch keeps the last answer for a follow-up on the next engine', async () => {
+  const { createSceneRunner } = await import('./sceneRunner.js');
+  const analystMemory = { lastResult: null };
+  const layerEnabledAt = new Map();
+  const run = createSceneRunner({
+    build: () =>
+      harness({ runnerOptions: { analystMemory, layerEnabledAt } }).runner,
+  });
+  run.attach({ engine: { kind: 'cesium' } });
+  const first = await run('analyst_query', {
+    layers: ['flights'],
+    scope: { kind: 'anywhere' },
+  });
+  assert.equal(first.ok, true);
+  // The real runner of the outgoing engine is disposed by the switch.
+  run.detach();
+  run.attach({ engine: { kind: 'navara' } });
+  const followUp = await run('analyst_query', {
+    layers: ['flights'],
+    followUp: true,
+  });
+  assert.equal(followUp.ok, true, JSON.stringify(followUp));
+  assert.equal(followUp.engine, 'navara');
+  // The session ending still forgets it.
+  run.resetConversation();
+  const afterReset = await run('analyst_query', {
+    layers: ['flights'],
+    followUp: true,
+  });
+  assert.equal(afterReset.code, 'NO_RESULT_CONTEXT');
+});

src/voice/sceneRunner.js

@@ -139,7 +139,9 @@ export function createSceneRunner({
     const previous = inner;
     inner = null;
     kind = null;
-    previous?.dispose?.();
+    // The conversation (the analyst's last answer) continues on the next
+    // engine: only this runner ends.
+    previous?.dispose?.({ keepMemory: true });
   };
   /** The page's switch settled: waiting calls look again. */
   run.wake = wake;

src/voice/voiceWorkflowHarness.mjs

@@ -40,6 +40,7 @@ export function harness({
   flights = null,
   pointer = null,
   on = ['flights'],
+  runnerOptions = {},
 } = {}) {
   const modules = {
     flights: flights || {
@@ -97,6 +98,7 @@ export function harness({
         return true;
       },
     },
+    ...runnerOptions,
   });
   return {
     runner,