fix(world-lab): start fresh runs after world setup

apps/world-lab/src/components/world-lab.test.tsx

@@ -1982,6 +1982,106 @@ describe('WorldLab', () => {
     }
   }, 15_000);
 
+  it('starts a fresh trail-hunter experiment after setup even when the prior experiment was at tick 50', async () => {
+    try {
+      const at50 = simulationSnapshotSchema.parse({
+        ...initial,
+        tickNumber: 50,
+        turnNumber: 400,
+        virtualTime: '2026-08-13T16:10:00.000Z',
+        lastTickIntervalMinutes: 5,
+        resolutionOrder: initial.world.agents.map(({ id }) => id),
+        experiment: { ...initial.experiment, totalCompletedTurns: 400 },
+      });
+      const fresh = simulationSnapshotSchema.parse({
+        ...initial,
+        scenario: {
+          ...initial.scenario,
+          objectiveVersion: 'durable-influence-v3',
+          capabilities: {
+            ...initial.scenario.capabilities,
+            simulatedPlayerPressure: true,
+          },
+          simulatedPlayer: {
+            enabled: true,
+            profile: 'trail-hunter-v1',
+            seed: 'reset-trail-hunter',
+          },
+        },
+        world: {
+          ...initial.world,
+          simulatedPlayer: {
+            profile: 'trail-hunter-v1',
+            currentCell: initial.world.hexes[0]!.cell,
+            metrics: {
+              movements: 0,
+              cellsDisinfected: 0,
+              blockedDisinfections: 0,
+            },
+          },
+        },
+      });
+      let tickRequests = 0;
+      let appliedProfile: string | undefined;
+      vi.stubGlobal(
+        'fetch',
+        vi.fn((input: RequestInfo | URL, init?: RequestInit) => {
+          const url = String(input);
+          if (url.endsWith('/setup/preview'))
+            return jsonResponse(
+              previewWorldSetup(JSON.parse(String(init?.body))),
+            );
+          if (url.endsWith('/experiment/setup')) {
+            appliedProfile = JSON.parse(String(init?.body)).simulatedPlayer
+              .profile;
+            return jsonResponse({ snapshot: fresh });
+          }
+          if (url.includes('/tick?mutationId=') && init?.method === 'POST') {
+            tickRequests += 1;
+            return jsonResponse(completeTickResponse(fresh, 1));
+          }
+          return jsonResponse(at50);
+        }),
+      );
+
+      const user = userEvent.setup();
+      render(<WorldLab />);
+      await act(async () => {
+        await Promise.resolve();
+        await Promise.resolve();
+      });
+      expect(screen.getByText('Tick 50')).toBeInTheDocument();
+      await openOverflow(user);
+      await user.click(screen.getByRole('button', { name: 'World setup' }));
+      await user.click(
+        screen.getByRole('checkbox', {
+          name: 'Enable simulated player pressure',
+        }),
+      );
+      await user.selectOptions(
+        screen.getByLabelText('Simulated player profile'),
+        'trail-hunter-v1',
+      );
+      await user.click(screen.getByRole('button', { name: 'Preview' }));
+      await user.click(
+        screen.getByRole('button', { name: 'Apply / Create Experiment' }),
+      );
+      expect(appliedProfile).toBe('trail-hunter-v1');
+      await act(async () => {
+        await Promise.resolve();
+        await Promise.resolve();
+      });
+      expect(screen.getByText('Tick 0')).toBeInTheDocument();
+      await user.selectOptions(screen.getByLabelText('Tick target'), '50');
+      await user.click(screen.getByRole('button', { name: 'Run to tick 50' }));
+      await waitFor(() => {
+        expect(tickRequests).toBe(1);
+      });
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it('keeps run targets absolute and makes current or past targets unavailable', async () => {
     window.sessionStorage.setItem('hexzero.world-lab.run-target', '25');
     const at50 = simulationSnapshotSchema.parse({

apps/world-lab/src/components/world-lab.tsx

@@ -1372,13 +1372,8 @@ export function WorldLab() {
           }
           onClose={() => setSetupOpen(false)}
           onApplied={(next) => {
-            setSnapshot(next);
+            applySnapshot(next);
             setSelectedCell(null);
-            setSelectedAgentId((selected) =>
-              next.world.agents.some(({ id }) => id === selected)
-                ? selected
-                : (next.world.agents[0]?.id ?? null),
-            );
             setExportAgentIds((selected) =>
               selected.filter((id) =>
                 next.world.agents.some((agent) => agent.id === id),

docs/TESTING.md

@@ -67,6 +67,9 @@ these safe worker failure reasons. Cost display tests separate provider-reported
 cost from admission exposure and show that TypeSafe Jev monetary cost remains
 unknown without provider billing data. The browser suite checks that a long
 swarm activity log scrolls inside the fixed-height bottom dock.
+World Lab component coverage also checks that applying a fresh Trail hunter
+scenario after a tick-50 experiment resets the run counter so the next Run to
+tick 50 command sends its first Game API tick request.
 
 Attempt-budget tests use deterministic providers and cover whole-roster tick
 admission, retry permits, cancellation finalization, and the distinction