fix(gateway): align dedupe eviction with entry timestamp

src/gateway/server-maintenance.test.ts

@@ -1,6 +1,7 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
 import type { HealthSummary } from "../commands/health.js";
 import type { ChatAbortControllerEntry } from "./chat-abort.js";
+import { DEDUPE_MAX } from "./server-constants.js";
 
 const cleanOldMediaMock = vi.fn(async () => {});
 
@@ -222,4 +223,31 @@ describe("startGatewayMaintenanceTimers", () => {
 
     stopMaintenanceTimers(timers);
   });
+
+  it("evicts dedupe overflow by oldest timestamp even after reinsertion", async () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2026-03-22T00:00:00Z"));
+    const { startGatewayMaintenanceTimers } = await import("./server-maintenance.js");
+    const deps = createMaintenanceTimerDeps();
+    const now = Date.now();
+
+    for (let index = 0; index < DEDUPE_MAX; index += 1) {
+      deps.dedupe.set(`stable-${index}`, { ts: now - 1_000 + index, ok: true });
+    }
+
+    deps.dedupe.delete("stable-10");
+    deps.dedupe.set("stable-10", { ts: now - 2_000, ok: true });
+    deps.dedupe.set("overflow-newest", { ts: now - 100, ok: true });
+
+    const timers = startGatewayMaintenanceTimers(deps);
+
+    await vi.advanceTimersByTimeAsync(60_000);
+
+    expect(deps.dedupe.size).toBe(DEDUPE_MAX);
+    expect(deps.dedupe.has("stable-10")).toBe(false);
+    expect(deps.dedupe.has("stable-0")).toBe(true);
+    expect(deps.dedupe.has("overflow-newest")).toBe(true);
+
+    stopMaintenanceTimers(timers);
+  });
 });

src/gateway/server-maintenance.ts

@@ -90,9 +90,15 @@ export function startGatewayMaintenanceTimers(params: {
       }
     }
     if (params.dedupe.size > DEDUPE_MAX) {
-      const entries = [...params.dedupe.entries()].toSorted((a, b) => a[1].ts - b[1].ts);
-      for (let i = 0; i < params.dedupe.size - DEDUPE_MAX; i++) {
-        params.dedupe.delete(entries[i][0]);
+      const excess = params.dedupe.size - DEDUPE_MAX;
+      // Keep overflow eviction aligned with the entry timestamp, not Map
+      // insertion order, so refresh/reinsert paths still prune the oldest data.
+      const oldestKeys = [...params.dedupe.entries()]
+        .toSorted(([, left], [, right]) => left.ts - right.ts)
+        .slice(0, excess)
+        .map(([key]) => key);
+      for (const key of oldestKeys) {
+        params.dedupe.delete(key);
       }
     }