fix(usage): preserve history through discovery failures

A failed account-store read does not confirm that an account was removed. Retain its existing host mapping until successful discovery replaces it, without carrying mappings across agent launch environments.

packages/server/src/server/plugins/usage-sources/index.test.ts

@@ -725,3 +725,39 @@ test("attempt ordering keeps its timestamp while retained freshness records succ
   expect(failure?.fetchedAt).toBe(new Date(3000).toISOString());
   expect(failure?.lastSuccessful?.fetchedAt).toBe(success?.successfulAt);
 });
+
+test("failed discovery preserves history until discovery confirms account removal", async () => {
+  let discoveryFails = false;
+  let present = true;
+  let available = true;
+  const registry = new UsageSourceRegistry(() => 1000, 300_000, { warn: () => {} });
+  registry.register(
+    source({
+      id: "source",
+      discover: async () => {
+        if (discoveryFails) throw new Error("Login store temporarily unavailable");
+        return present ? [{ key: "account", input: {} }] : [];
+      },
+      fetch: async () =>
+        available
+          ? { status: "available", windows: [{ id: "weekly", label: "Weekly", usedPct: 42 }] }
+          : { status: "error", error: "Rate limited" },
+    }),
+  );
+  const [success] = await registry.listReports();
+  available = false;
+  discoveryFails = true;
+  const [duringDiscoveryFailure] = await registry.listReports({ forceRefresh: true });
+  expect(duringDiscoveryFailure?.lastSuccessful).toEqual({
+    fetchedAt: success?.successfulAt,
+    report: success?.report,
+  });
+  discoveryFails = false;
+  const [afterDiscoveryRecovery] = await registry.listReports({ forceRefresh: true });
+  expect(afterDiscoveryRecovery?.lastSuccessful).toEqual(duringDiscoveryFailure?.lastSuccessful);
+  expect(afterDiscoveryRecovery?.report).toEqual({ status: "error", error: "Rate limited" });
+  present = false;
+  expect(await registry.listReports()).toEqual([]);
+  present = true;
+  expect((await registry.listReports())[0]?.lastSuccessful).toBeUndefined();
+});

packages/server/src/server/plugins/usage-sources/index.ts

@@ -99,7 +99,7 @@ export class UsageSourceRegistry {
     } else if (options.reportIds !== undefined) {
       ids = options.reportIds;
     } else {
-      this.defaults = await this.discover({ kind: "global" });
+      this.defaults = await this.discover({ kind: "global" }, this.defaults);
       this.mergeKnown();
       ids = [...this.known.keys()];
     }
@@ -191,7 +191,10 @@ export class UsageSourceRegistry {
     );
   }
 
-  private async discover(scope: UsageScope): Promise<Map<string, KnownReport>> {
+  private async discover(
+    scope: UsageScope,
+    previous: ReadonlyMap<string, KnownReport> = new Map(),
+  ): Promise<Map<string, KnownReport>> {
     const discovered = await Promise.all(
       [...this.sources.values()].map(async (source) => {
         const reports = new Map<string, KnownReport>();
@@ -218,6 +221,11 @@ export class UsageSourceRegistry {
           }
         } catch (error) {
           this.logger.warn({ sourceId: source.id, err: error }, "Usage source discovery failed");
+          // A failed store read does not confirm removal. Session discovery has no previous
+          // mapping because a resumed agent may use a different launch environment.
+          for (const [id, report] of previous) {
+            if (report.source === source) reports.set(id, report);
+          }
         }
         return reports;
       }),