diff --git a/packages/server/src/server/agent/agent-archive.test.ts b/packages/server/src/server/agent/agent-archive.test.ts
new file mode 100644
index 000000000..c4dd34b7e
--- /dev/null
+++ b/packages/server/src/server/agent/agent-archive.test.ts
@@ -0,0 +1,70 @@
+import { expect, test } from "vitest";
+
+import { buildArchivedAgentRecord } from "./agent-archive.js";
+import type { StoredAgentRecord } from "./agent-storage.js";
+
+const BASE_RECORD: StoredAgentRecord = {
+  id: "agent-1",
+  provider: "codex",
+  cwd: "/workspace/project",
+  createdAt: "2025-01-01T00:00:00.000Z",
+  updatedAt: "2025-01-02T00:00:00.000Z",
+  labels: {},
+  lastStatus: "idle",
+  config: null,
+};
+
+test("archives a stored agent without changing terminal statuses", () => {
+  const statuses: Array<StoredAgentRecord["lastStatus"]> = ["idle", "error", "closed"];
+
+  for (const status of statuses) {
+    const archived = buildArchivedAgentRecord(
+      { ...BASE_RECORD, lastStatus: status },
+      { archivedAt: "2025-01-03T00:00:00.000Z" },
+    );
+
+    expect(archived.lastStatus).toBe(status);
+    expect(archived.archivedAt).toBe("2025-01-03T00:00:00.000Z");
+    expect(archived.updatedAt).toBe(BASE_RECORD.updatedAt);
+  }
+});
+
+test("archives busy stored agents as idle", () => {
+  const statuses: Array<StoredAgentRecord["lastStatus"]> = ["initializing", "running"];
+
+  for (const status of statuses) {
+    const archived = buildArchivedAgentRecord(
+      { ...BASE_RECORD, lastStatus: status },
+      { archivedAt: "2025-01-03T00:00:00.000Z" },
+    );
+
+    expect(archived.lastStatus).toBe("idle");
+  }
+});
+
+test("clears persisted attention when archiving", () => {
+  const archived = buildArchivedAgentRecord(
+    {
+      ...BASE_RECORD,
+      requiresAttention: true,
+      attentionReason: "finished",
+      attentionTimestamp: "2025-01-02T12:00:00.000Z",
+    },
+    { archivedAt: "2025-01-03T00:00:00.000Z" },
+  );
+
+  expect(archived).toMatchObject({
+    requiresAttention: false,
+    attentionReason: null,
+    attentionTimestamp: null,
+  });
+});
+
+test("can stamp updatedAt to the archive timestamp", () => {
+  const archived = buildArchivedAgentRecord(BASE_RECORD, {
+    archivedAt: "2025-01-03T00:00:00.000Z",
+    updatedAt: "2025-01-03T00:00:00.000Z",
+  });
+
+  expect(archived.updatedAt).toBe("2025-01-03T00:00:00.000Z");
+});
diff --git a/packages/server/src/server/agent/agent-archive.ts b/packages/server/src/server/agent/agent-archive.ts
new file mode 100644
index 000000000..7e35d98f8
--- /dev/null
+++ b/packages/server/src/server/agent/agent-archive.ts
@@ -0,0 +1,30 @@
+import type { StoredAgentRecord } from "./agent-storage.js";
+
+export type ArchivedStoredAgentRecord = StoredAgentRecord & { archivedAt: string };
+
+interface BuildArchivedAgentRecordOptions {
+  archivedAt?: string;
+  updatedAt?: string;
+}
+
+export function buildArchivedAgentRecord(
+  record: StoredAgentRecord,
+  options?: BuildArchivedAgentRecordOptions,
+): ArchivedStoredAgentRecord {
+  const archivedAt = options?.archivedAt ?? new Date().toISOString();
+  return {
+    ...record,
+    archivedAt,
+    updatedAt: options?.updatedAt ?? record.updatedAt,
+    lastStatus: normalizeArchivedStatus(record.lastStatus),
+    requiresAttention: false,
+    attentionReason: null,
+    attentionTimestamp: null,
+  };
+}
+
+function normalizeArchivedStatus(
+  status: StoredAgentRecord["lastStatus"],
+): StoredAgentRecord["lastStatus"] {
+  return status === "running" || status === "initializing" ? "idle" : status;
+}
diff --git a/packages/server/src/server/agent/agent-manager.ts b/packages/server/src/server/agent/agent-manager.ts
index 62afd20b7..5d047f0f4 100644
--- a/packages/server/src/server/agent/agent-manager.ts
+++ b/packages/server/src/server/agent/agent-manager.ts
@@ -35,6 +35,7 @@ import type {
   ListPersistedAgentsOptions,
   PersistedAgentDescriptor,
 } from "./agent-sdk-types.js";
+import { buildArchivedAgentRecord, type ArchivedStoredAgentRecord } from "./agent-archive.js";
 import type { StoredAgentRecord, AgentStorage } from "./agent-storage.js";
 import {
   InMemoryAgentTimelineStore,
@@ -66,7 +67,6 @@ const STORED_AGENT_CAPABILITIES: AgentCapabilityFlags = {
 };
 
 type TimeoutResult = "completed" | "timed_out";
-type ArchivedStoredAgentRecord = StoredAgentRecord & { archivedAt: string };
 
 interface TimeoutOptions {
   operation: Promise<void>;
@@ -1071,19 +1071,7 @@ export class AgentManager {
   private async markRecordArchived(record: StoredAgentRecord): Promise<ArchivedStoredAgentRecord> {
     const registry = this.requireRegistry();
     const archivedAt = new Date().toISOString();
-    const normalizedStatus =
-      record.lastStatus === "running" || record.lastStatus === "initializing"
-        ? "idle"
-        : record.lastStatus;
-    const archivedRecord: ArchivedStoredAgentRecord = {
-      ...record,
-      archivedAt,
-      updatedAt: archivedAt,
-      lastStatus: normalizedStatus,
-      requiresAttention: false,
-      attentionReason: null,
-      attentionTimestamp: null,
-    };
+    const archivedRecord = buildArchivedAgentRecord(record, { archivedAt, updatedAt: archivedAt });
 
     await registry.upsert(archivedRecord);
 
@@ -1259,19 +1247,7 @@ export class AgentManager {
       throw new Error(`Agent not found: ${agentId}`);
     }
 
-    const normalizedStatus =
-      record.lastStatus === "running" || record.lastStatus === "initializing"
-        ? "idle"
-        : record.lastStatus;
-
-    const nextRecord: StoredAgentRecord = {
-      ...record,
-      archivedAt,
-      lastStatus: normalizedStatus,
-      requiresAttention: false,
-      attentionReason: null,
-      attentionTimestamp: null,
-    };
+    const nextRecord = buildArchivedAgentRecord(record, { archivedAt });
     await registry.upsert(nextRecord);
 
     await this.archiveNativeSessionBestEffort(record.provider, record.persistence);