Preserve loaded logs across same-server fleet updates

src/lib/ui/components/LogPanel.svelte

@@ -37,6 +37,7 @@
     let stickToBottom = $state(true);
 
     const refresh = createLogRefresh({
+        onReset: () => { data = {}; refreshError = ''; },
         onLoading: value => { loading = value; },
         onError: message => { refreshError = message; },
         onData: (key, body) => {
@@ -88,7 +89,6 @@
         }
         parts.push({ text: line.slice(start), match: false }); return parts;
     }
-    $effect(() => { server; data = {}; refreshError = ''; });
     $effect(() => {
         const target = { server, key: active, lines };
         const auto = autoRefresh;

src/lib/ui/log-refresh.ts

@@ -14,6 +14,7 @@ export interface LogResponse {
 
 interface Selection { server: string; key: string; lines: number }
 interface Options {
+    onReset: () => void;
     onData: (key: string, response: LogResponse) => void;
     onError: (message: string) => void;
     onLoading: (loading: boolean) => void;
@@ -73,6 +74,9 @@ export function createLogRefresh(options: Options) {
         automatic = enabled;
         interval = pollMs;
         if (changed || pausing) cancel();
+        // Fleet updates can replace the parent server object without changing
+        // this identity. Only navigation to a different server invalidates logs.
+        if (selection?.server !== target.server) options.onReset();
         if (changed) { selection = target; options.onError(''); }
         if (!selection?.key) return;
         if (automatic) stopPolling = pollVisible(refresh, interval);

tests/unit/log-refresh.test.ts

@@ -20,9 +20,10 @@ afterEach(() => { controller?.dispose(); vi.useRealTimers(); vi.unstubAllGlobals
 
 function setup() {
     const fetcher = vi.fn<typeof fetch>();
+    const onReset = vi.fn();
     const onData = vi.fn(); const onError = vi.fn(); const onLoading = vi.fn();
-    controller = createLogRefresh({ fetcher, onData, onError, onLoading });
+    controller = createLogRefresh({ fetcher, onReset, onData, onError, onLoading });
-    return { fetcher, onData, onError, onLoading };
+    return { fetcher, onReset, onData, onError, onLoading };
 }
 const visibility = (state: string) => {
     documentStub.visibilityState = state;
@@ -30,6 +31,36 @@ const visibility = (state: string) => {
 };
 
 describe('log refresh controls', () => {
+    it('retains a manually loaded log through same-server fleet updates and resets only on server navigation', async () => {
+        const fetcher = vi.fn<typeof fetch>().mockImplementation(async () => response('loaded log'));
+        let displayed: string[] = [];
+        const reset = vi.fn(() => { displayed = []; });
+        controller = createLogRefresh({ fetcher, onReset: reset,
+            onData: (_key, body) => { displayed = body.lines ?? []; }, onError: vi.fn(), onLoading: vi.fn() });
+        controller.configure(target, true, 5000);
+        await controller.refresh();
+        controller.configure(target, false, 5000);
+        await controller.refresh();
+        expect(displayed).toEqual(['loaded log']);
+        reset.mockClear();
+        // The parent supplies fresh props whenever Fleet publishes a snapshot.
+        for (let i = 0; i < 3; i++) {
+            controller.configure({ ...target }, false, 5000);
+            await vi.advanceTimersByTimeAsync(5000);
+            expect(displayed).toEqual(['loaded log']);
+        }
+        expect(reset).not.toHaveBeenCalled();
+        expect(fetcher).toHaveBeenCalledTimes(2);
+        controller.configure({ ...target, key: 'games_zm' }, false, 5000);
+        await controller.refresh();
+        expect(reset).not.toHaveBeenCalled();
+        controller.configure({ ...target, server: 'different-server' }, false, 5000);
+        expect(reset).toHaveBeenCalledTimes(1);
+        expect(displayed).toEqual([]);
+        await controller.refresh();
+        expect(displayed).toEqual(['loaded log']);
+    });
+
     it('pauses without fetching again and remains paused across intervals and visibility changes', async () => {
         const { fetcher, onData, onLoading } = setup();
         fetcher.mockResolvedValueOnce(response('saved log'));