diff --git a/api/package.json b/api/package.json
index de294d2d..add61ad4 100644
--- a/api/package.json
+++ b/api/package.json
@@ -16,7 +16,7 @@
     "db:cleanup": "node dist/cron/dbCleanup.js",
     "funnel-report": "node dist/scripts/funnelReport.js",
     "npm:audit": "npm audit --json > /tmp/audit.json && echo \"Audit complete\"",
-"test": "TS_NODE_TRANSPILE_ONLY=1 node --loader ts-node/esm tests/wallet-provisioning.test.js && node --loader ts-node/esm tests/ssrf.test.js && node tests/integration.test.js && node tests/pages.test.js && node tests/x402-v1-passthrough.test.mjs && node tests/model-cost.test.mjs && node tests/session-pricing.test.mjs && node tests/prompt-moderation.test.mjs && node tests/critical-regressions.test.mjs && node tests/unsubscribe.test.mjs && node tests/reactivation-render.test.mjs && node tests/outreach-active-devs.test.mjs && node tests/credit-alert-dedup.test.mjs && node tests/verify-activation.test.mjs && node tests/signup-firstcall.test.mjs && node tests/oauth-signup-cta.test.mjs && node tests/x402-sell-copy.test.mjs && node tests/verify-resend.test.mjs && node tests/intent-funnel.test.mjs && node tests/credit-email-buylinks.test.mjs",
+"test": "TS_NODE_TRANSPILE_ONLY=1 node --loader ts-node/esm tests/wallet-provisioning.test.js && node --loader ts-node/esm tests/ssrf.test.js && node tests/integration.test.js && node tests/pages.test.js && node tests/x402-v1-passthrough.test.mjs && node tests/model-cost.test.mjs && node tests/session-pricing.test.mjs && node tests/prompt-moderation.test.mjs && node tests/critical-regressions.test.mjs && node tests/unsubscribe.test.mjs && node tests/reactivation-render.test.mjs && node tests/outreach-active-devs.test.mjs && node tests/credit-alert-dedup.test.mjs && node tests/verify-activation.test.mjs && node tests/signup-firstcall.test.mjs && node tests/oauth-signup-cta.test.mjs && node tests/x402-sell-copy.test.mjs && node tests/verify-resend.test.mjs && node tests/deleted-account-session.test.mjs && node tests/intent-funnel.test.mjs && node tests/credit-email-buylinks.test.mjs",
     "test:integration": "node tests/integration.test.js",
     "test:verify-activation": "node tests/verify-activation.test.mjs",
     "test:verify-resend": "node tests/verify-resend.test.mjs",
diff --git a/api/src/index.ts b/api/src/index.ts
index 9814d7be..8ab0e9d8 100644
--- a/api/src/index.ts
+++ b/api/src/index.ts
@@ -31,7 +31,7 @@ import workflowsRouter from "./routes/workflows.js";
 import seoRouter from "./routes/seo.js";
 import legalRouter from "./routes/legal.js";
 import oauthRouter from "./routes/oauth.js";
-import authRouter, { verifySession } from "./routes/auth.js";
+import authRouter, { clearSessionCookie, verifySession } from "./routes/auth.js";
 import chatRouter from "./routes/chat.js";
 import directoryRouter from "./routes/directory.js";
 import walletRouter from "./routes/wallet.js";
@@ -47,6 +47,8 @@ import trialRouter from "./routes/trial.js";
 import affiliateRouter from "./routes/affiliate.js";
 import mcpRouter from "./routes/mcp.js";
 import unsubscribeRouter from "./routes/unsubscribe.js";
+import { prisma } from "./lib/prisma.js";
+import { isDeletedAgent } from "./lib/deletedAgent.js";
 
 // x402 SDK (official Coinbase @x402/express integration)
 import { initX402Sdk, x402SdkMiddleware, getX402SdkStatus, warmX402Sdk } from "./middleware/x402-sdk.js";
@@ -395,9 +397,15 @@ app.get("/signup", (req: Request, res: Response) => {
 });
 app.get("/register", (_req: Request, res: Response) => res.redirect(301, "/signup"));
 app.get("/login", (_req: Request, res: Response) => res.set("Cache-Control", "no-store, no-cache, must-revalidate, proxy-revalidate").set("Pragma", "no-cache").set("Expires", "0").type("text/html").send(LOGIN_HTML));
-app.get("/dashboard", (req: Request, res: Response) => {
+app.get("/dashboard", async (req: Request, res: Response) => {
   const token = req.cookies?.arch_session;
-  if (!token || !verifySession(token)) {
+  const payload = token ? verifySession(token) : null;
+  if (!payload) {
+    return res.redirect(302, "/login?next=/dashboard");
+  }
+  const agent = await prisma.agent.findUnique({ where: { id: payload.sub } }).catch(() => null);
+  if (!agent || isDeletedAgent(agent)) {
+    clearSessionCookie(res);
     return res.redirect(302, "/login?next=/dashboard");
   }
   return res.type("text/html").send(DASHBOARD_HTML);
diff --git a/api/src/lib/deletedAgent.ts b/api/src/lib/deletedAgent.ts
new file mode 100644
index 00000000..d523d976
--- /dev/null
+++ b/api/src/lib/deletedAgent.ts
@@ -0,0 +1,20 @@
+/**
+ * Deleted accounts are anonymized in-place so retained Purchase/X402 rows keep
+ * their foreign-key integrity. This predicate is the durable "disabled" marker
+ * for those anonymized Agent rows: deletion clears every credential and rewrites
+ * the email into the reserved deleted.invalid domain.
+ */
+export function isDeletedAgent(agent: {
+  email?: string | null;
+  apiKeyHash?: string | null;
+  apiKeyPrefix?: string | null;
+  passwordHash?: string | null;
+} | null | undefined): boolean {
+  if (!agent) return false;
+  return Boolean(
+    agent.email?.endsWith("@deleted.invalid") &&
+    !agent.apiKeyHash &&
+    !agent.apiKeyPrefix &&
+    !agent.passwordHash
+  );
+}
diff --git a/api/src/middleware/auth.ts b/api/src/middleware/auth.ts
index 87fe109b..aeb50dcb 100644
--- a/api/src/middleware/auth.ts
+++ b/api/src/middleware/auth.ts
@@ -3,6 +3,7 @@ import { prisma } from "../lib/prisma.js";
 import { timingSafeEqual } from "crypto";
 import bcrypt from "bcryptjs";
 import { DISCOVERY_LINKS } from "../utils/discoveryLinks.js";
+import { isDeletedAgent } from "../lib/deletedAgent.js";
 
 export interface AuthedRequest extends Request {
   agent?: {
@@ -83,11 +84,11 @@ export async function requireAuth(
       }
     }
 
-    if (!agent) {
+    if (!agent || isDeletedAgent(agent)) {
       res.status(401).json({
         ok: false,
-        error: "unauthorized",
-        message: "Invalid API key or OAuth token. Register at https://archtools.dev",
+        error: isDeletedAgent(agent) ? "account_deleted" : "unauthorized",
+        message: isDeletedAgent(agent) ? "This account has been deleted." : "Invalid API key or OAuth token. Register at https://archtools.dev",
         request_id: crypto.randomUUID(),
       });
       return;
diff --git a/api/src/routes/agent.ts b/api/src/routes/agent.ts
index 3fafb1d1..858dd459 100644
--- a/api/src/routes/agent.ts
+++ b/api/src/routes/agent.ts
@@ -9,6 +9,7 @@ import { stripe } from "../lib/stripe.js";
 import Stripe from "stripe";
 import crypto from "crypto";
 import bcrypt from "bcryptjs";
+import { clearSessionCookie } from "./auth.js";
 import { SIGNUP_FREE_CREDITS, isDisposableEmail, issueEmailVerification, verifyEmailToken, peekEmailVerifyToken, enforceSignupLimits, recordSignupIp, normalizeEmailIdentity, allowVerificationResend, reissueEmailVerification } from "../lib/verification.js";
 import { VERIFY_TOKEN_RE, renderVerifyConfirmPage, renderVerifyActivationPage, renderVerifyErrorPage, renderVerifyResendSentPage } from "../assets/verifyEmailHtml.js";
 import { REFERRAL_REWARD } from "../lib/referralReward.js";
@@ -582,6 +583,7 @@ router.delete("/", requireAuth, requireApiKeyAuth, async (req: AuthedRequest, re
 
     // Structured log mirrors the DataDeletionAudit row (no PII — counts + audit id).
     logger.info(`[gdpr] account deleted agent=${agent.id} erased=${JSON.stringify(result.counts)} audit=${result.auditId} at=${new Date().toISOString()}`);
+    clearSessionCookie(res);
 
     res.json({
       ok: true,
diff --git a/api/src/routes/auth.ts b/api/src/routes/auth.ts
index bf59d12f..ebf02f92 100644
--- a/api/src/routes/auth.ts
+++ b/api/src/routes/auth.ts
@@ -8,6 +8,7 @@ import { logAudit } from "../lib/audit.js";
 import { logger } from "../lib/logger.js";
 import { sendPasswordResetEmail } from "../services/email.js";
 import { captureEvent, identifyUser } from "../lib/posthog.js";
+import { isDeletedAgent } from "../lib/deletedAgent.js";
 
 const router = Router();
 
@@ -28,6 +29,11 @@ const COOKIE_OPTS = {
   path: "/",
 };
 
+export function clearSessionCookie(res: Response): void {
+  res.clearCookie(COOKIE_NAME, { path: "/", httpOnly: true, secure: process.env.NODE_ENV === "production", sameSite: "lax" as const });
+  res.cookie(COOKIE_NAME, "", { ...COOKIE_OPTS, maxAge: 0 });
+}
+
 const loginLimiter = rateLimit({
   windowMs: 15 * 60 * 1000,
   max: 5,
@@ -173,8 +179,7 @@ router.post("/set-password", sensitiveLimiter, async (req: Request, res: Respons
 });
 
 router.get("/logout", (_req: Request, res: Response): void => {
-  res.clearCookie(COOKIE_NAME, { path: "/", httpOnly: true, secure: process.env.NODE_ENV === "production", sameSite: "lax" as const });
-  res.cookie(COOKIE_NAME, "", { ...COOKIE_OPTS, maxAge: 0 });
+  clearSessionCookie(res);
   res.redirect("/login");
 });
 
@@ -191,9 +196,9 @@ router.get("/me", async (req: Request, res: Response): Promise<void> => {
     return;
   }
   const agent = await prisma.agent.findUnique({ where: { id: payload.sub } });
-  if (!agent) {
-    res.clearCookie(COOKIE_NAME, { path: "/" });
-    res.status(401).json({ ok: false, error: "agent_not_found" });
+  if (!agent || isDeletedAgent(agent)) {
+    clearSessionCookie(res);
+    res.status(401).json({ ok: false, error: isDeletedAgent(agent) ? "account_deleted" : "agent_not_found" });
     return;
   }
   res.json({
@@ -212,7 +217,11 @@ router.get("/api-key", async (req: Request, res: Response): Promise<void> => {
   const payload = verifySession(token);
   if (!payload) { res.status(401).json({ ok: false, error: "session_expired" }); return; }
   const agent = await prisma.agent.findUnique({ where: { id: payload.sub } });
-  if (!agent) { res.status(401).json({ ok: false, error: "agent_not_found" }); return; }
+  if (!agent || isDeletedAgent(agent)) {
+    clearSessionCookie(res);
+    res.status(401).json({ ok: false, error: isDeletedAgent(agent) ? "account_deleted" : "agent_not_found" });
+    return;
+  }
   // Plaintext keys are no longer stored — only the prefix can be shown.
   // Full keys are returned exactly once at registration/rotation.
   const masked = agent.apiKeyPrefix ? `${agent.apiKeyPrefix}…` : null;
diff --git a/api/src/routes/billing.ts b/api/src/routes/billing.ts
index 0d8fb48a..0c139308 100644
--- a/api/src/routes/billing.ts
+++ b/api/src/routes/billing.ts
@@ -2,13 +2,14 @@ import { Router, Request, Response, NextFunction } from "express";
 import { prisma } from "../lib/prisma.js";
 import { stripe } from "../lib/stripe.js";
 import { requireAuth, AuthedRequest } from "../middleware/auth.js";
-import { verifySession } from "./auth.js";
+import { clearSessionCookie, verifySession } from "./auth.js";
 import { reqId } from "../utils/credits.js";
 import { sendPurchaseConfirmation, sendAdminAlert } from "../services/email.js";
 import { fireWebhookEvent } from "../services/webhooks.js";
 import { safeErr } from "../utils/credits.js";
 import { tierFromSubscriptionPlanId } from "../lib/tiers.js";
 import { clawbackDelta, proratedClawbackTarget } from "../lib/clawback.js";
+import { isDeletedAgent } from "../lib/deletedAgent.js";
 
 const router = Router();
 
@@ -34,7 +35,8 @@ async function requireAuthOrSession(req: AuthedRequest, res: Response, next: Nex
     return;
   }
   const agent = await prisma.agent.findUnique({ where: { id: payload.sub } }).catch(() => null);
-  if (!agent) {
+  if (!agent || isDeletedAgent(agent)) {
+    if (isDeletedAgent(agent)) clearSessionCookie(res);
     res.status(401).json({ ok: false, error: "unauthorized", message: "Session invalid. Sign in again at /login", request_id: reqId() });
     return;
   }
diff --git a/api/tests/deleted-account-session.test.mjs b/api/tests/deleted-account-session.test.mjs
new file mode 100644
index 00000000..1d5b1e8d
--- /dev/null
+++ b/api/tests/deleted-account-session.test.mjs
@@ -0,0 +1,149 @@
+/**
+ * Deleted-account stale session regression.
+ *
+ * DELETE /v1/agent anonymizes the Agent row in-place for financial-record FK
+ * retention. A stateless arch_session JWT issued before deletion must not keep
+ * that anonymized row usable for browser auth or Stripe checkout.
+ *
+ * Run: cd api && npm run build && node tests/deleted-account-session.test.mjs
+ */
+import assert from "assert";
+
+process.env.JWT_SECRET = process.env.JWT_SECRET || "test-secret-do-not-use-in-prod";
+process.env.DATABASE_URL = process.env.DATABASE_URL || "postgresql://stub:stub@127.0.0.1:5432/stub";
+process.env.STRIPE_SECRET_KEY = "";
+
+const express = (await import("express")).default;
+const cookieParser = (await import("cookie-parser")).default;
+const { prisma } = await import("../dist/lib/prisma.js");
+const { isDeletedAgent } = await import("../dist/lib/deletedAgent.js");
+const authModule = await import("../dist/routes/auth.js");
+const billingRouter = (await import("../dist/routes/billing.js")).default;
+
+const { default: authRouter, signSession } = authModule;
+
+let failures = 0;
+async function test(name, fn) {
+  try {
+    await fn();
+    console.log(`  ok ${name}`);
+  } catch (e) {
+    failures++;
+    console.error(`  FAIL ${name}: ${e.message}`);
+  }
+}
+
+const deletedAgent = {
+  id: "agent_deleted_session",
+  email: "deleted-agent_deleted_session@deleted.invalid",
+  apiKeyPrefix: null,
+  apiKeyHash: null,
+  passwordHash: null,
+  credits: 0,
+  tier: "free",
+  totalCalls: 0,
+  createdAt: new Date("2026-08-06T00:00:00Z"),
+};
+
+const activeAgent = {
+  id: "agent_active_session",
+  email: "active@example.com",
+  apiKeyPrefix: "arch_abcdefg",
+  apiKeyHash: "$2b$10$aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+  passwordHash: null,
+  credits: 10,
+  tier: "free",
+  totalCalls: 0,
+  createdAt: new Date("2026-08-06T00:00:00Z"),
+};
+
+let currentAgent = deletedAgent;
+prisma.agent.findUnique = async ({ where }) => {
+  return where?.id === currentAgent.id ? currentAgent : null;
+};
+
+const app = express();
+app.use(express.json());
+app.use(cookieParser());
+app.use("/auth", authRouter);
+app.use("/v1/billing", billingRouter);
+
+const server = app.listen(0);
+const BASE = `http://127.0.0.1:${server.address().port}`;
+
+function cookieFor(agentId) {
+  return `arch_session=${signSession(agentId)}`;
+}
+
+async function postJson(path, body, cookie) {
+  const res = await fetch(`${BASE}${path}`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json", Cookie: cookie },
+    body: JSON.stringify(body),
+  });
+  const text = await res.text();
+  let json = {};
+  try { json = JSON.parse(text); } catch {}
+  return { res, json };
+}
+
+async function getJson(path, cookie) {
+  const res = await fetch(`${BASE}${path}`, { headers: { Cookie: cookie } });
+  const text = await res.text();
+  let json = {};
+  try { json = JSON.parse(text); } catch {}
+  return { res, json };
+}
+
+function assertClearsSession(res) {
+  const setCookie = res.headers.get("set-cookie") || "";
+  assert.ok(setCookie.includes("arch_session="), "must emit Set-Cookie for arch_session");
+  assert.ok(/Max-Age=0|Expires=Thu, 01 Jan 1970/i.test(setCookie), "must expire the stale session cookie");
+}
+
+console.log("deleted-account stale session:");
+
+await test("helper recognizes the anonymized deleted-row marker only", () => {
+  assert.strictEqual(isDeletedAgent(deletedAgent), true);
+  assert.strictEqual(isDeletedAgent(activeAgent), false);
+  assert.strictEqual(isDeletedAgent({ ...deletedAgent, apiKeyHash: "still-has-a-key" }), false);
+});
+
+await test("/auth/me rejects and clears a stale deleted-account session", async () => {
+  currentAgent = deletedAgent;
+  const { res, json } = await getJson("/auth/me", cookieFor(deletedAgent.id));
+  assert.strictEqual(res.status, 401);
+  assert.strictEqual(json.error, "account_deleted");
+  assertClearsSession(res);
+});
+
+await test("/auth/api-key rejects and clears a stale deleted-account session", async () => {
+  currentAgent = deletedAgent;
+  const { res, json } = await getJson("/auth/api-key", cookieFor(deletedAgent.id));
+  assert.strictEqual(res.status, 401);
+  assert.strictEqual(json.error, "account_deleted");
+  assertClearsSession(res);
+});
+
+await test("/v1/billing/checkout rejects a deleted-account session before Stripe", async () => {
+  currentAgent = deletedAgent;
+  const { res, json } = await postJson("/v1/billing/checkout", { pack: "starter" }, cookieFor(deletedAgent.id));
+  assert.strictEqual(res.status, 401);
+  assert.strictEqual(json.error, "unauthorized");
+  assertClearsSession(res);
+});
+
+await test("active session still reaches the normal billing path", async () => {
+  currentAgent = activeAgent;
+  const { res, json } = await postJson("/v1/billing/checkout", { pack: "starter" }, cookieFor(activeAgent.id));
+  assert.strictEqual(res.status, 503);
+  assert.strictEqual(json.error, "not_configured");
+});
+
+server.close();
+
+if (failures) {
+  console.error(`\n${failures} failure(s)`);
+  process.exit(1);
+}
+console.log("\nAll deleted-account stale-session tests passed.");
diff --git a/api/tests/verify-activation.test.mjs b/api/tests/verify-activation.test.mjs
index fcb94ef5..68aaff80 100644
--- a/api/tests/verify-activation.test.mjs
+++ b/api/tests/verify-activation.test.mjs
@@ -20,6 +20,7 @@
 import assert from "assert";
 
 process.env.DATABASE_URL ??= "postgresql://stub:stub@127.0.0.1:5432/stub";
+process.env.JWT_SECRET ??= "test-secret-do-not-use-in-prod";
 
 const { prisma } = await import("../dist/lib/prisma.js");
 const { peekEmailVerifyToken } = await import("../dist/lib/verification.js");
diff --git a/api/tests/verify-resend.test.mjs b/api/tests/verify-resend.test.mjs
index 924c1a1d..03394550 100644
--- a/api/tests/verify-resend.test.mjs
+++ b/api/tests/verify-resend.test.mjs
@@ -23,6 +23,7 @@
 import assert from "assert";
 
 process.env.DATABASE_URL ??= "postgresql://stub:stub@127.0.0.1:5432/stub";
+process.env.JWT_SECRET ??= "test-secret-do-not-use-in-prod";
 
 const { prisma } = await import("../dist/lib/prisma.js");
 const { renderVerifyErrorPage, renderVerifyResendSentPage } = await import("../dist/assets/verifyEmailHtml.js");