Exclude stale pre-2000 threads from thread list API

src/api/threadsApi.ts

@@ -11,7 +11,7 @@ import { buildScheduleName } from "../scheduler/schedule-name.js";
 import { durationToSeconds } from "../retention.js";
 import { isCalendarEventSignal, isEmailSignal } from "../types/index.js";
 import type { EmailContentStore } from "./content-store.js";
-import type { Signal, AnySignal, InboundEmailSignalData, PageParams, ThreadStatus, Workflow } from "../types/index.js";
+import type { Signal, AnySignal, InboundEmailSignalData, PageParams, Thread, ThreadStatus, Workflow } from "../types/index.js";
 import type { CalendarResponseData, DomainMisconfigurationData, Pagination } from "../types/index.js";
 import type { UpdateThreadFields, ThreadDatabase } from "../database/thread-database.js";
 import type { AccountDatabase } from "../database/account-database.js";
@@ -51,6 +51,13 @@ function page<K extends string, T>(key: K, items: T[], nextCursor?: string): Rec
   return { [key]: items, pagination: { cursor: nextCursor ?? null } } as Record<K, T[]> & { pagination: Pagination };
 }
 
+// Threads with a stale/placeholder lastSignalAt (e.g. never-updated legacy records) are
+// excluded from list responses — they don't represent real activity.
+const MIN_LAST_SIGNAL_AT = "2000-01-01T00:00:00.000Z";
+function hasRecentSignal(thread: Thread): boolean {
+  return thread.lastSignalAt >= MIN_LAST_SIGNAL_AT;
+}
+
 export class ThreadsApi {
   constructor(
     private readonly threadDb: ThreadDatabase,
@@ -129,7 +136,7 @@ export class ThreadsApi {
           return err(c, 500, "Internal Server Error");
         }
 
-        return c.json(page("threads", threadsResult.value.map(toApiThread), undefined), 200);
+        return c.json(page("threads", threadsResult.value.filter(hasRecentSignal).map(toApiThread), undefined), 200);
       }
       const params: ListThreadsParams = {
         ...(query["workflow"] ? { workflow: query["workflow"] as Workflow } : {}),
@@ -143,7 +150,7 @@ export class ThreadsApi {
         logger.error(`Failed to list threads: ${result.error.message}`, { code: "api.threads.list_failed", error: result.error });
         return err(c, 500, "Internal Server Error");
       }
-      return c.json(page("threads", result.value.items.map(toApiThread), result.value.nextCursor), 200);
+      return c.json(page("threads", result.value.items.filter(hasRecentSignal).map(toApiThread), result.value.nextCursor), 200);
     });
 
     // -------------------------------------------------------------------------

tests/api/api.spec.ts

@@ -415,6 +415,18 @@ describe("API", () => {
       const body = await res.json() as { pagination: { cursor: string } };
       expect(body.pagination.cursor).toBe("cursor-abc");
     });
+
+    it("excludes threads whose last signal predates Jan 1 2000", async () => {
+      vi.mocked(threadDb.listThreads).mockResolvedValueOnce(ok({
+        items: [
+          makeThread({ id: "arc-stale", lastSignalAt: "1999-12-31T23:59:59.000Z" }),
+          makeThread({ id: "arc-fresh", lastSignalAt: "2024-01-01T00:00:00.000Z" }),
+        ],
+      }));
+      const res = await req(app, "GET", `${A}/threads`);
+      const body = await res.json() as { threads: { threadId: string }[] };
+      expect(body.threads.map(t => t.threadId)).toEqual(["arc-fresh"]);
+    });
   });
 
   describe("GET /accounts/:accountId/threads/:threadId", () => {