diff --git a/lib/auth/__tests__/getApiKeyAccountId.test.ts b/lib/auth/__tests__/getApiKeyAccountId.test.ts
new file mode 100644
index 000000000..e2a9aa7cc
--- /dev/null
+++ b/lib/auth/__tests__/getApiKeyAccountId.test.ts
@@ -0,0 +1,54 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+import { getApiKeyAccountId } from "@/lib/auth/getApiKeyAccountId";
+import { selectAccountApiKeys } from "@/lib/supabase/account_api_keys/selectAccountApiKeys";
+
+vi.mock("@/lib/networking/getCorsHeaders", () => ({ getCorsHeaders: () => ({}) }));
+vi.mock("@/lib/keys/hashApiKey", () => ({ hashApiKey: (k: string) => `hashed_${k}` }));
+vi.mock("@/lib/const", () => ({ PRIVY_PROJECT_SECRET: "test_secret" }));
+vi.mock("@/lib/supabase/account_api_keys/selectAccountApiKeys", () => ({
+  selectAccountApiKeys: vi.fn(),
+}));
+
+function req(apiKey?: string) {
+  const headers = new Headers();
+  if (apiKey) headers.set("x-api-key", apiKey);
+  return new NextRequest("https://x.test/api", { headers });
+}
+
+const baseRow = {
+  id: "k",
+  account: "acc-1",
+  key_hash: "hashed_recoup_sk_x",
+  name: "n",
+  last_used: null,
+  created_at: "2026-01-01T00:00:00Z",
+};
+
+describe("getApiKeyAccountId", () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it("returns accountId for a non-expiring key (expires_at null)", async () => {
+    vi.mocked(selectAccountApiKeys).mockResolvedValue([{ ...baseRow, expires_at: null }]);
+    expect(await getApiKeyAccountId(req("recoup_sk_x"))).toBe("acc-1");
+  });
+
+  it("returns accountId for a future expiry", async () => {
+    const future = new Date(Date.now() + 60_000).toISOString();
+    vi.mocked(selectAccountApiKeys).mockResolvedValue([{ ...baseRow, expires_at: future }]);
+    expect(await getApiKeyAccountId(req("recoup_sk_x"))).toBe("acc-1");
+  });
+
+  it("rejects an expired key with 401", async () => {
+    const past = new Date(Date.now() - 60_000).toISOString();
+    vi.mocked(selectAccountApiKeys).mockResolvedValue([{ ...baseRow, expires_at: past }]);
+    const res = await getApiKeyAccountId(req("recoup_sk_x"));
+    expect(res).toBeInstanceOf(Response);
+    expect((res as Response).status).toBe(401);
+  });
+
+  it("401 when no x-api-key header", async () => {
+    const res = await getApiKeyAccountId(req());
+    expect((res as Response).status).toBe(401);
+  });
+});
diff --git a/lib/auth/getApiKeyAccountId.ts b/lib/auth/getApiKeyAccountId.ts
index 49af4106a..a5dce9ed6 100644
--- a/lib/auth/getApiKeyAccountId.ts
+++ b/lib/auth/getApiKeyAccountId.ts
@@ -1,6 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { getCorsHeaders } from "@/lib/networking/getCorsHeaders";
 import { hashApiKey } from "@/lib/keys/hashApiKey";
+import { isApiKeyExpired } from "@/lib/keys/isApiKeyExpired";
 import { PRIVY_PROJECT_SECRET } from "@/lib/const";
 import { selectAccountApiKeys } from "@/lib/supabase/account_api_keys/selectAccountApiKeys";
 
@@ -45,9 +46,11 @@ export async function getApiKeyAccountId(request: NextRequest): Promise<string |
       );
     }
 
-    const accountId = apiKeys[0]?.account ?? null;
+    const matched = apiKeys[0];
+    const accountId = matched?.account ?? null;
 
-    if (!accountId) {
+    // Reject an unknown key, or an ephemeral key past its TTL (chat#1813).
+    if (!accountId || isApiKeyExpired(matched?.expires_at)) {
       return NextResponse.json(
         {
           status: "error",
diff --git a/lib/keys/__tests__/isApiKeyExpired.test.ts b/lib/keys/__tests__/isApiKeyExpired.test.ts
new file mode 100644
index 000000000..87ac88f3b
--- /dev/null
+++ b/lib/keys/__tests__/isApiKeyExpired.test.ts
@@ -0,0 +1,24 @@
+import { describe, it, expect } from "vitest";
+import { isApiKeyExpired } from "@/lib/keys/isApiKeyExpired";
+
+describe("isApiKeyExpired", () => {
+  const now = Date.parse("2026-06-23T00:00:00Z");
+
+  it("treats null/undefined expiry as never-expiring", () => {
+    expect(isApiKeyExpired(null, now)).toBe(false);
+    expect(isApiKeyExpired(undefined, now)).toBe(false);
+  });
+
+  it("is false for a future expiry", () => {
+    expect(isApiKeyExpired("2026-06-23T01:00:00Z", now)).toBe(false);
+  });
+
+  it("is true at or past the expiry", () => {
+    expect(isApiKeyExpired("2026-06-22T23:59:59Z", now)).toBe(true);
+    expect(isApiKeyExpired("2026-06-23T00:00:00Z", now)).toBe(true);
+  });
+
+  it("treats an unparseable expiry as non-expiring (never lock out)", () => {
+    expect(isApiKeyExpired("not-a-date", now)).toBe(false);
+  });
+});
diff --git a/lib/keys/isApiKeyExpired.ts b/lib/keys/isApiKeyExpired.ts
new file mode 100644
index 000000000..57e7632ec
--- /dev/null
+++ b/lib/keys/isApiKeyExpired.ts
@@ -0,0 +1,15 @@
+/**
+ * Whether an api key's `expires_at` has passed. NULL/undefined = never expires.
+ * An unparseable value is treated as non-expiring so a bad row can't lock a
+ * caller out. Used by api auth to reject ephemeral keys past their TTL
+ * (recoupable/chat#1813).
+ */
+export function isApiKeyExpired(
+  expiresAt: string | null | undefined,
+  now: number = Date.now(),
+): boolean {
+  if (!expiresAt) return false;
+  const exp = Date.parse(expiresAt);
+  if (Number.isNaN(exp)) return false;
+  return exp <= now;
+}
diff --git a/types/database.types.ts b/types/database.types.ts
index 1771da89f..872750b72 100644
--- a/types/database.types.ts
+++ b/types/database.types.ts
@@ -12,6 +12,7 @@ export type Database = {
         Row: {
           account: string | null;
           created_at: string;
+          expires_at: string | null;
           id: string;
           key_hash: string | null;
           last_used: string | null;
@@ -20,6 +21,7 @@ export type Database = {
         Insert: {
           account?: string | null;
           created_at?: string;
+          expires_at?: string | null;
           id?: string;
           key_hash?: string | null;
           last_used?: string | null;
@@ -28,6 +30,7 @@ export type Database = {
         Update: {
           account?: string | null;
           created_at?: string;
+          expires_at?: string | null;
           id?: string;
           key_hash?: string | null;
           last_used?: string | null;