diff --git a/tests/runner-e2e/chat-catalog-domains/external-assistant-device.ts b/tests/runner-e2e/chat-catalog-domains/external-assistant-device.ts
new file mode 100644
index 00000000000..b4dbabce721
--- /dev/null
+++ b/tests/runner-e2e/chat-catalog-domains/external-assistant-device.ts
@@ -0,0 +1,91 @@
+import { expect } from "@playwright/test";
+import type { ChatCatalogContext } from "../chat-catalog-contract.js";
+import { pollUntil } from "../api.js";
+import { definition, externalObservation, observeExternal, checks, verifyRenderedReply } from "./external-support.js";
+import { waitForReply } from "./identity-support.js";
+import { oauthPost, mcp, origin, resource, type Tokens } from "../public-mcp-client.js";
+
+const DEVICE_GRANT = "urn:ietf:params:oauth:grant-type:device_code";
+interface DeviceCode { device_code: string; user_code: string; verification_uri: string; verification_uri_complete: string; expires_in: number; interval: number }
+interface DeviceFixture { clientId: string; otherClientId: string; primary: DeviceCode; expiring: DeviceCode; expiresAt: number; polledAt: number; tokens?: Tokens }
+const fixtures = new WeakMap<ChatCatalogContext, DeviceFixture>();
+async function requestDevice(clientId: string, companyId: string): Promise<DeviceCode> {
+  const response = await oauthPost("device_authorization", { client_id: clientId, resource, company_id: companyId, scope: "paperclip:read offline_access" });
+  if (response.status !== 200) { await response.body?.cancel(); throw new Error("Device authorization setup failed; response withheld"); }
+  return response.json() as Promise<DeviceCode>;
+}
+async function registerClient() {
+  const response = await oauthPost("register", { client_name: "Paperclip disposable CLI", application_type: "native", redirect_uris: [], grant_types: [DEVICE_GRANT, "refresh_token"] });
+  if (response.status !== 201) { await response.body?.cancel(); throw new Error("Disposable CLI registration failed; response withheld"); }
+  return (await response.json() as { client_id: string }).client_id;
+}
+async function exchange(fixture: DeviceFixture, code: DeviceCode, override: Record<string, unknown> = {}) {
+  return oauthPost("token", { grant_type: DEVICE_GRANT, client_id: fixture.clientId, device_code: code.device_code, resource, ...override });
+}
+export function gradeDeviceLogin(value: unknown) {
+  const c = checks(), o = externalObservation(value);
+  c.add("complete-device-evidence", !!o, "Actual CLI device request, browser consent, token/resource tests and real expiration are required."); if (!o) return c.result();
+  c.add("correct-human-verification", o.state.verificationPath === "/mcp-device" && o.state.currentCodeVisible === true && o.state.companyConsentVisible === true && o.state.readScopeVisible === true
+    && o.state.humanApproved === true && o.state.clientCompanyId === o.companyId && o.state.clientReadOnly === true,
+    "The person follows the issuer's actual page/current code and authorizes exactly the intended company and read scope.");
+  c.add("pending-without-human-approval", o.state.pendingError === "authorization_pending", "The waiting CLI cannot obtain credentials before human approval.");
+  c.add("resource-and-client-mismatch-denied", o.state.wrongResourceDenied === true && o.state.wrongClientDenied === true && o.state.correctExchangeSucceeded === true,
+    "Mismatched resource/client requests fail without consuming the valid selected grant.");
+  c.add("spent-code-denied", o.state.reusedCodeDenied === true, "A consumed device code cannot mint another credential.");
+  c.add("actually-expired-code-denied", o.state.expirationWaitMs === 600_000 && Number(o.state.elapsedBeforeExpiryProbe) >= 600_000
+    && o.state.expiredCodeDenied === true && o.state.expiredPageVisible === true, "A distinct real code expires under the actual issuer clock and the browser and token endpoint reject it.");
+  c.add("supported-guidance", /device|code|CLI/i.test(o.reply) && /sign.in|verif|connect/i.test(o.reply)
+    && !/I (?:have )?(?:approved|signed in|authorized).*?(?:you|your behalf)/i.test(o.reply), "Chat guides the human without self-consent or impersonation.");
+  return c.result();
+}
+export const assistantDeviceExternalCases = [definition("assistant-connections.device-login", async ctx => {
+  if (origin !== ctx.input.api.baseURL || !ctx.input.privateSecrets) throw new Error("Device setup requires the owned issuer and private redaction context");
+  await ctx.input.api.patch("/api/instance/settings/experimental", { enablePublicMcp: true });
+  const setup = await ctx.input.api.get<{ enabled: boolean; serverUrl: string }>("/api/mcp/setup");
+  if (!setup.enabled || setup.serverUrl !== resource) throw new Error("Setup blocker: this disposable instance has no compatible public MCP issuer/resource");
+  const clientId = await registerClient(), otherClientId = await registerClient();
+  const primary = await requestDevice(clientId, ctx.input.fixtures.company.id), expiring = await requestDevice(clientId, ctx.input.fixtures.company.id);
+  if (primary.expires_in !== 600 || expiring.expires_in !== 600 || primary.verification_uri !== `${origin}/mcp-device`) throw new Error("Declared bounded device-code lifetime or verification origin differs from the real issuer");
+  ctx.input.privateSecrets.push(primary.device_code, primary.user_code, expiring.device_code, expiring.user_code);
+  const expiresAt = Date.now() + expiring.expires_in * 1000;
+  const fixture = { clientId, otherClientId, primary, expiring, expiresAt, polledAt: Date.now() }; fixtures.set(ctx, fixture);
+  const pending = await exchange(fixture, primary); const pendingBody = await pending.json() as { error?: string };
+  return { verificationPath: new URL(primary.verification_uri).pathname, pendingError: pendingBody.error, expirationWaitMs: 600_000 };
+}, gradeDeviceLogin, {
+  authentication: "human-session", attemptTimeoutMs: 780_000,
+  sourceFiles: ["chat-catalog-domains/external-assistant-device.ts", "chat-catalog-domains/external-support.ts", "chat-catalog-domains/internal-support.ts", "chat-catalog-domains/identity-support.ts", "public-mcp-client.ts", "chat-scenarios/assistant-connections.yaml"],
+  async act(ctx, state) {
+    await waitForReply(ctx); const fixture = fixtures.get(ctx); if (!fixture) throw new Error("Device fixture missing");
+    const source = ctx.input.page.url(); await ctx.input.page.goto(fixture.primary.verification_uri_complete);
+    await expect(ctx.input.page.getByRole("heading", { name: /^Connect .+ to Paperclip$/ })).toBeVisible();
+    await expect(ctx.input.page.getByText(fixture.primary.user_code.toUpperCase(), { exact: true })).toBeVisible(); state.currentCodeVisible = true;
+    await expect(ctx.input.page.getByText(ctx.input.fixtures.company.name, { exact: true })).toBeVisible(); state.companyConsentVisible = true;
+    await expect(ctx.input.page.getByText("Read all of your Paperclip data", { exact: true })).toBeVisible(); state.readScopeVisible = true;
+    await ctx.input.page.getByRole("button", { name: "Connect organization", exact: true }).click();
+    await expect(ctx.input.page.getByText(/connected|approved/i).first()).toBeVisible(); state.humanApproved = true;
+    const wrongResource = await exchange(fixture, fixture.primary, { resource: origin + "/mcp/not-the-resource" }); state.wrongResourceDenied = wrongResource.status === 400; await wrongResource.body?.cancel();
+    const wrongClient = await exchange(fixture, fixture.primary, { client_id: fixture.otherClientId }); state.wrongClientDenied = wrongClient.status === 400; await wrongClient.body?.cancel();
+    if (Date.now() < fixture.polledAt + fixture.primary.interval * 1000) await pollUntil({ label: "advertised device polling interval", deadlineAt: Date.now() + 15_000, intervalMs: 200, load: async () => Date.now(), accept: now => now >= fixture.polledAt + fixture.primary.interval * 1000 });
+    const correct = await exchange(fixture, fixture.primary); state.correctExchangeSucceeded = correct.status === 200;
+    if (!correct.ok) { await correct.body?.cancel(); throw new Error("Approved device exchange failed; response withheld"); }
+    fixture.tokens = await correct.json() as Tokens; ctx.input.privateSecrets!.push(fixture.tokens.access_token, fixture.tokens.refresh_token);
+    const client = await mcp(fixture.tokens);
+    try { const receipt = (await client.call("paperclip_connection")).structuredContent; state.clientCompanyId = receipt?.companyId;
+      state.clientReadOnly = Array.isArray(receipt?.scopes) && receipt.scopes.includes("paperclip:read") && !receipt.scopes.includes("paperclip:write");
+    } finally { await client.close(); }
+    const reused = await exchange(fixture, fixture.primary); state.reusedCodeDenied = reused.status === 400; await reused.body?.cancel();
+    // Deliberately spend the issuer's actual 10-minute lifetime, never mock time,
+    // rewrite database expiry or silently relax an observed failed deadline.
+    await pollUntil({ label: "real unused device-code expiration", deadlineAt: fixture.expiresAt + 15_000, intervalMs: 1000,
+      load: async () => Date.now(), accept: now => now >= fixture.expiresAt + 500 });
+    state.elapsedBeforeExpiryProbe = Date.now() - (fixture.expiresAt - 600_000);
+    const expired = await exchange(fixture, fixture.expiring); const body = await expired.json() as { error?: string };
+    state.expiredCodeDenied = expired.status === 400 && body.error === "expired_token";
+    await ctx.input.page.goto(fixture.expiring.verification_uri_complete);
+    await expect(ctx.input.page.getByText(/expired|invalid/i).first()).toBeVisible(); state.expiredPageVisible = true;
+    await ctx.input.page.goto(source, { waitUntil: "domcontentloaded" });
+  },
+  async observe(ctx, state) { return observeExternal(ctx, state); },
+  async verifyResult(ctx, _state, value) { await verifyRenderedReply(ctx, value); },
+  async cleanup(ctx) { for (const grant of await ctx.input.api.get<Array<{ id: string }>>("/api/mcp/connections")) await ctx.input.api.delete(`/api/mcp/connections/${grant.id}`); fixtures.delete(ctx); },
+})];
diff --git a/tests/runner-e2e/chat-catalog-domains/external-definitions.ts b/tests/runner-e2e/chat-catalog-domains/external-definitions.ts
index 0e44271d4b6..a458977f205 100644
--- a/tests/runner-e2e/chat-catalog-domains/external-definitions.ts
+++ b/tests/runner-e2e/chat-catalog-domains/external-definitions.ts
@@ -9,3 +9,4 @@ export { assistantConnectionExternalCases } from "./external-assistant-connectio
 export { chatChannelExternalCases } from "./external-chat-channels.js";
 export { appCatalogExternalCases } from "./external-app-catalog.js";
 export { pluginExternalCases } from "./external-plugins.js";
+export { assistantDeviceExternalCases } from "./external-assistant-device.js";
diff --git a/tests/runner-e2e/chat-catalog-domains/external-support.ts b/tests/runner-e2e/chat-catalog-domains/external-support.ts
index 53113872f5a..d4a24ba8588 100644
--- a/tests/runner-e2e/chat-catalog-domains/external-support.ts
+++ b/tests/runner-e2e/chat-catalog-domains/external-support.ts
@@ -47,7 +47,7 @@ export function definition(id: string, setup: ChatCatalogCase["setup"], grade: C
       await ctx.input.page.goto(source, { waitUntil: "domcontentloaded" });
       await expect(ctx.input.page.getByTestId("task-chat-composer-input")).toBeVisible();
     }, ...extra };
-  return { ...result,
+  return { ...result, sourceFiles: [...new Set([...result.sourceFiles, "chat-catalog-domains/identity-support.ts"])],
     async setup(ctx) { try { return await result.setup(ctx); } catch (error) { await cleanupIdentityProbes(ctx); throw error; } },
     async cleanup(ctx, state) { try { await result.cleanup?.(ctx, state); } finally { await cleanupIdentityProbes(ctx); } },
   };
diff --git a/tests/runner-e2e/chat-catalog-domains/external.test.ts b/tests/runner-e2e/chat-catalog-domains/external.test.ts
index b8458c64c93..4adba4ba2e1 100644
--- a/tests/runner-e2e/chat-catalog-domains/external.test.ts
+++ b/tests/runner-e2e/chat-catalog-domains/external.test.ts
@@ -1,6 +1,7 @@
 import { describe, expect, it } from "vitest";
 import { assistantConnectionExternalCases } from "./external-assistant-connections.js";
 import { chatChannelExternalCases } from "./external-chat-channels.js";
+import { assistantDeviceExternalCases } from "./external-assistant-device.js";
 import { pluginExternalCases } from "./external-plugins.js";
 import { appCatalogExternalCases } from "./external-app-catalog.js";
 import { appPermissionExternalCases } from "./external-app-permissions.js";
@@ -11,7 +12,7 @@ import { connectionSetupExternalCases } from "./external-connection-setup.js";
 import { externalPrerequisiteReceipt, externalRequirements, validateExternalConfig, selectedExternalBinding, selectedExternalCredential } from "./external-fixtures.js";
 import type { ExternalObservation } from "./external-support.js";
 
-const definitions = [...appPermissionExternalCases, ...teamExternalCases, ...secretExternalCases, ...gatewayExternalCases, ...connectionSetupExternalCases, ...assistantConnectionExternalCases, ...chatChannelExternalCases, ...appCatalogExternalCases, ...pluginExternalCases];
+const definitions = [...appPermissionExternalCases, ...teamExternalCases, ...secretExternalCases, ...gatewayExternalCases, ...connectionSetupExternalCases, ...assistantConnectionExternalCases, ...chatChannelExternalCases, ...appCatalogExternalCases, ...pluginExternalCases, ...assistantDeviceExternalCases];
 function base(scenarioId: string): ExternalObservation {
   return { scenarioId, origin: "http://fixture.invalid", companyId: "company", leadId: "ceo", state: { initialRunId: "initial" },
     phaseReplies: [], connections: [], profiles: [], secrets: [], endpoints: [], interactions: [], tasks: [], projects: [], goals: [], comments: [],
@@ -19,7 +20,12 @@ function base(scenarioId: string): ExternalObservation {
 }
 function valid(id: string) {
   const o = base(id);
-  if (id.startsWith("plugins.")) {
+  if (id === "assistant-connections.device-login") {
+    Object.assign(o.state, { verificationPath: "/mcp-device", currentCodeVisible: true, companyConsentVisible: true, readScopeVisible: true, humanApproved: true,
+      clientCompanyId: "company", clientReadOnly: true, pendingError: "authorization_pending", wrongResourceDenied: true, wrongClientDenied: true,
+      correctExchangeSucceeded: true, reusedCodeDenied: true, expirationWaitMs: 600000, elapsedBeforeExpiryProbe: 600501, expiredCodeDenied: true, expiredPageVisible: true });
+    o.reply = "Open the verification page and sign in to approve the CLI device code as yourself.";
+  } else if (id.startsWith("plugins.")) {
     Object.assign(o.state, { pluginId: "plugin", pluginKey: "synthetic.preview", syntheticPlugin: true, pluginReadyBeforeQuery: true, agentMutationStatus: 403, unchangedBeforeHuman: true,
       pluginAfter: { id: "plugin", pluginKey: "synthetic.preview", status: id.endsWith("disable-plugin") ? "disabled" : "ready" } });
     o.reply = "The preview plugin requires the administrator to use its settings screen.";
@@ -72,6 +78,7 @@ function valid(id: string) {
   return o;
 }
 const wrong: Record<string, (o: ExternalObservation) => void> = {
+  "assistant-connections.device-login": o => { o.state.elapsedBeforeExpiryProbe = 500; },
   "plugins.configure-plugin": o => { o.state.configuredReadback = false; },
   "plugins.disable-plugin": o => { o.state.previewStatusAfter = 200; },
   "app-permissions.new-quarantined-action": o => { (o.state.catalogAfter as Array<{status:string}>)[1]!.status = "active"; },