fix(app): avoid false never-online claims in diagnostics (#9054)

A missing runtime timestamp does not establish connection history. Report it as unknown while preserving supplied timestamps.

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/app/src/diagnostics/app-diagnostic-report.test.ts

@@ -46,6 +46,31 @@ function makeHost(): HostProfile {
   };
 }
 
+function makeSnapshot(host: HostProfile): HostRuntimeSnapshot {
+  return {
+    serverId: host.serverId,
+    activeConnectionId: "relay:relay.secret.test:443",
+    activeConnection: {
+      type: "relay",
+      endpoint: "relay.secret.test:443",
+      display: "relay",
+    },
+    connectionStatus: "online",
+    client: null,
+    lastError: null,
+    lastOnlineAt: "2026-06-25T00:00:00.000Z",
+    agentDirectoryStatus: "ready",
+    agentDirectoryError: null,
+    hasEverLoadedAgentDirectory: true,
+    probeByConnectionId: new Map([
+      ["direct:secret.example.test:6767", { status: "available", latencyMs: 42 }],
+      ["relay:relay.secret.test:443", { status: "available", latencyMs: 8 }],
+    ]),
+    clientGeneration: 1,
+    connectionEpoch: 1,
+  };
+}
+
 describe("app diagnostics report", () => {
   test("reports whether the connected daemon is managed by Paseo Desktop", () => {
     const report = formatServerInfoSection({
@@ -61,31 +86,11 @@ describe("app diagnostics report", () => {
 
   test("formats connection rows without raw connection details", () => {
     const host = makeHost();
-    const snapshot: HostRuntimeSnapshot = {
-      serverId: host.serverId,
-      activeConnectionId: "relay:relay.secret.test:443",
-      activeConnection: {
-        type: "relay",
-        endpoint: "relay.secret.test:443",
-        display: "relay",
-      },
-      connectionStatus: "online",
-      client: null,
-      lastError: null,
-      lastOnlineAt: "2026-06-25T00:00:00.000Z",
-      agentDirectoryStatus: "ready",
-      agentDirectoryError: null,
-      hasEverLoadedAgentDirectory: true,
-      probeByConnectionId: new Map([
-        ["direct:secret.example.test:6767", { status: "available", latencyMs: 42 }],
-        ["relay:relay.secret.test:443", { status: "available", latencyMs: 8 }],
-      ]),
-      clientGeneration: 1,
-      connectionEpoch: 1,
-    };
+    const snapshot = makeSnapshot(host);
 
     const report = formatHostRuntimeSection({ host, snapshot });
 
+    expect(report).toContain("Last online: 2026-06-25T00:00:00.000Z");
     expect(report).toContain("direct TCP");
     expect(report).toContain("relay");
     expect(report).toContain("local socket");
@@ -97,6 +102,27 @@ describe("app diagnostics report", () => {
     expect(report).not.toContain("tcp-password");
   });
 
+  test.each(["connecting", "offline", "error"] as const)(
+    "does not claim a previously connected host was never online while %s",
+    (connectionStatus) => {
+      const host = makeHost();
+      const snapshot = makeSnapshot(host);
+      const report = formatHostRuntimeSection({
+        host,
+        snapshot: { ...snapshot, connectionStatus, lastOnlineAt: null },
+      });
+
+      expect(report).toContain("Last online: unknown");
+      expect(report).not.toContain("Last online: never");
+    },
+  );
+
+  test("does not infer connection history when the runtime has not started", () => {
+    const report = formatHostRuntimeSection({ host: makeHost(), snapshot: null });
+
+    expect(report).toContain("Last online: unknown");
+  });
+
   test("redacts saved connection secrets from collected daemon and desktop text", () => {
     const host = makeHost();
     const redacted = redactAppDiagnosticReport(

packages/app/src/diagnostics/app-diagnostic-report.ts

@@ -45,7 +45,7 @@ export function formatHostRuntimeSection(input: {
         ? describeConnectionKind(snapshot.activeConnection.type)
         : "none",
     },
-    { label: "Last online", value: snapshot?.lastOnlineAt ?? "never" },
+    { label: "Last online", value: snapshot?.lastOnlineAt ?? "unknown" },
     { label: "Last error", value: snapshot?.lastError ?? "none" },
     {
       label: "Agent directory",