diff --git a/docs/adr/0007-remote-device-leases.md b/docs/adr/0007-remote-device-leases.md
index b126b7e0c8..0dfbf82532 100644
--- a/docs/adr/0007-remote-device-leases.md
+++ b/docs/adr/0007-remote-device-leases.md
@@ -329,23 +329,29 @@ The host sets the tenant, session isolation, and lease of that client on every r
 
 ## Device spec
 
-A proxy lease can name a device spec beside platform, target, and device: `osVersion`, `imageTag`, and `physical` on `agent_device.lease.allocate`.
+A proxy lease can name a device spec beside platform, target, and device: `osVersion`, `imageTag`, `deviceMode`, and `physical` on `agent_device.lease.allocate`.
 Only a backend in front of the daemon, such as simlock, can pick a device by these keys.
 A daemon cannot pick by them.
 If a daemon ignored them, a request would run on a device that it did not ask for.
-Thus, a daemon refuses every request that names a non-blank `osVersion` or `imageTag`, or `physical: true`, before admission and before a lease is recorded.
+Thus, a daemon refuses every request that names a non-blank `osVersion`, `imageTag` or `deviceMode`, or `physical: true`, before admission and before a lease is recorded.
 The refusal is `UNSUPPORTED_OPERATION` with `details.reason: 'device-spec-unsupported'` and `details.keys`.
 This applies to a local daemon and to a daemon behind `agent-device proxy`.
-A blank `osVersion` or `imageTag` and `physical: false` name nothing, so a daemon accepts them.
+A blank `osVersion`, `imageTag` or `deviceMode` and `physical: false` name nothing, so a daemon accepts them.
+`deviceMode` (`slim` or `full`) chooses how much of an iOS simulator the backend keeps running; the backend validates the value.
 A named value is used as given, without trimming.
 A value of another type is refused with `INVALID_ARGS`, `details.reason: 'device-spec-invalid'`, and `details.keys`.
 `readLeaseDeviceSpec` is the one decision on these rules, for CLI flags, the SDK, MCP, and the daemon.
 A remote config file first applies the value rules of every config key: a string must be non-empty, and a boolean also accepts a boolean string such as `"true"`.
-The backend that honours the spec strips the keys before it forwards the allocation, and echoes the granted device on the lease as `lease.device` (`model`, `osVersion`, `imageTag?`, `physical`).
+The backend that honours the spec strips the keys before it forwards the allocation, and echoes the granted device on the lease as `lease.device` (`model`, `osVersion`, `imageTag?`, `deviceMode?`, `physical`).
 `deviceKey` stays the identity of the lease; `lease.device` is the proof that the spec was understood.
+A backend can report the granted mode as `lease.device.deviceMode`.
+The CLI proxy connection treats a new lease that reports `slim` for a `full` request like a lease without `lease.device`.
+Full is a guarantee and slim is best effort, so `full` granted for a `slim` request is served.
+A lease that reports no mode is accepted, so the proof does not confirm `deviceMode`: a backend that ignores the key and reports no mode grants its default without an error.
 A backend older than the spec returns a lease without `lease.device`.
 The CLI proxy connection then releases that lease and fails with `UNSUPPORTED_OPERATION` and `details.reason: 'device-spec-unsupported'`.
 `details.released` reports whether the release succeeded.
+An allocation that explicitly reports reuse (`created: false`) fails with the same reason, without a release and without `details.released`.
 A live lease serves a later command only when every spec key that the command names equals the one the lease was allocated by; otherwise the command fails with `CONNECTION_DEVICE_CONFLICT`.
 The client never picks a device by spec from the daemon inventory.
 `--target` stays the only class selector.
diff --git a/packages/client/src/__tests__/index-leases.test.ts b/packages/client/src/__tests__/index-leases.test.ts
index f93091e858..cb51273935 100644
--- a/packages/client/src/__tests__/index-leases.test.ts
+++ b/packages/client/src/__tests__/index-leases.test.ts
@@ -71,3 +71,33 @@ test('lease allocation sends the device spec and returns the device the backend
     physical: false,
   });
 });
+
+test('lease allocation sends the iOS simulator mode and returns the mode the backend granted', async () => {
+  const device = { model: 'iPhone 17 Pro', osVersion: '26.2', deviceMode: 'full', physical: false };
+  const setup = createClientTransport(async (req) => ({
+    ok: true,
+    data: {
+      lease: {
+        leaseId: 'lease-mode',
+        tenantId: req.meta?.tenantId,
+        runId: req.meta?.runId,
+        backend: req.meta?.leaseBackend,
+        deviceKey: 'ios:mobile:SIM-1',
+        device,
+      },
+    },
+  }));
+  const client = createAgentDeviceClient(setup.config, { transport: setup.transport });
+
+  const lease = await client.leases.allocate({
+    tenant: 'proxy',
+    runId: 'proxy-run',
+    leaseBackend: 'ios-instance',
+    leaseProvider: 'proxy',
+    platform: 'ios',
+    deviceMode: 'full',
+  });
+
+  assert.equal(setup.calls[0]?.flags?.deviceMode, 'full');
+  assert.deepEqual(lease.device, device);
+});
diff --git a/packages/command-registry/src/flag-definitions-target.ts b/packages/command-registry/src/flag-definitions-target.ts
index 22c6a9320f..744cb6fb12 100644
--- a/packages/command-registry/src/flag-definitions-target.ts
+++ b/packages/command-registry/src/flag-definitions-target.ts
@@ -76,6 +76,18 @@ export const TARGET_FLAG_DEFINITIONS: readonly FlagDefinition[] = [
     projectConfig: false,
     recorded: false,
   },
+  {
+    key: 'deviceMode',
+    names: ['--device-mode'],
+    type: 'string',
+    usageLabel: '--device-mode <slim|full>',
+    usageDescription:
+      'Proxy lease: iOS simulator mode (slim or full) the backend leases; refused without such a backend',
+    inputDescription:
+      'iOS simulator mode for the device a proxy backend leases, slim or full, sent as given; the backend validates it. A blank string names nothing; a non-string fails with INVALID_ARGS, reason device-spec-invalid. Only the CLI allocating a lease through connect proxy sends it to that backend; a daemon refuses every other request that names it, with reason device-spec-unsupported.',
+    projectConfig: false,
+    recorded: false,
+  },
   {
     key: 'physical',
     names: ['--physical'],
diff --git a/packages/command-registry/src/flag-groups.ts b/packages/command-registry/src/flag-groups.ts
index 8d193dd336..dfa837fd6c 100644
--- a/packages/command-registry/src/flag-groups.ts
+++ b/packages/command-registry/src/flag-groups.ts
@@ -38,6 +38,7 @@ export const METRO_RELOAD_FLAGS = flagKeys('metroHost', 'metroPort', 'bundleUrl'
 export const LEASE_DEVICE_SPEC_FLAGS = flagKeys(
   'osVersion',
   'imageTag',
+  'deviceMode',
   'physical',
 ) satisfies typeof LEASE_DEVICE_SPEC_KEYS;
 export const REPEATED_TOUCH_FLAGS = flagKeys(
diff --git a/packages/command-surface/src/cli-grammar/common.ts b/packages/command-surface/src/cli-grammar/common.ts
index aeedc120b1..707e205356 100644
--- a/packages/command-surface/src/cli-grammar/common.ts
+++ b/packages/command-surface/src/cli-grammar/common.ts
@@ -147,7 +147,7 @@ export function repeatedInputFromFlags(flags: CliFlags): Record<string, unknown>
 /** The spec keys the flags name, as `requireLeaseDeviceSpec` decides them; an invalid key throws. */
 export function leaseDeviceSpecInputFromFlags(
   flags: CliFlags,
-): Pick<CliFlags, 'osVersion' | 'imageTag' | 'physical'> {
+): Pick<CliFlags, 'osVersion' | 'imageTag' | 'deviceMode' | 'physical'> {
   return requireLeaseDeviceSpec(flags).spec;
 }
 
diff --git a/packages/command-surface/src/command-flags.ts b/packages/command-surface/src/command-flags.ts
index 080b61bbb5..f58a664506 100644
--- a/packages/command-surface/src/command-flags.ts
+++ b/packages/command-surface/src/command-flags.ts
@@ -61,6 +61,7 @@ function buildFlags(options: InternalRequestOptions): CommandFlags {
     androidDeviceAllowlist: options.androidDeviceAllowlist,
     osVersion: options.osVersion,
     imageTag: options.imageTag,
+    deviceMode: options.deviceMode,
     physical: options.physical,
     surface: options.surface,
     activity: options.activity,
diff --git a/packages/command-surface/src/command-input.ts b/packages/command-surface/src/command-input.ts
index dad83b0467..b8296f2508 100644
--- a/packages/command-surface/src/command-input.ts
+++ b/packages/command-surface/src/command-input.ts
@@ -432,11 +432,14 @@ export function leaseDeviceSpecFields() {
   return {
     osVersion: leaseDeviceSpecField('osVersion'),
     imageTag: leaseDeviceSpecField('imageTag'),
+    deviceMode: leaseDeviceSpecField('deviceMode'),
     physical: leaseDeviceSpecField('physical'),
   };
 }
 
-function leaseDeviceSpecField<TKey extends 'osVersion' | 'imageTag' | 'physical'>(key: TKey) {
+function leaseDeviceSpecField<TKey extends 'osVersion' | 'imageTag' | 'deviceMode' | 'physical'>(
+  key: TKey,
+) {
   return customField(
     optionField(key).schema,
     (record) => requireLeaseDeviceSpec({ [key]: record[key] }).spec[key],
diff --git a/packages/command-surface/src/schema/option-schema.ts b/packages/command-surface/src/schema/option-schema.ts
index 7930a5d201..3fb03a4d5b 100644
--- a/packages/command-surface/src/schema/option-schema.ts
+++ b/packages/command-surface/src/schema/option-schema.ts
@@ -33,6 +33,7 @@ const ENV_EXCLUDED_FLAG_KEYS = new Set<FlagKey>([
   // The proxy lease device spec comes from a flag or `connect proxy`, never ambient environment.
   'osVersion',
   'imageTag',
+  'deviceMode',
   'physical',
 ]);
 
diff --git a/packages/contracts/src/__tests__/lease-scope.test.ts b/packages/contracts/src/__tests__/lease-scope.test.ts
index c85de05c68..59b84c7cd7 100644
--- a/packages/contracts/src/__tests__/lease-scope.test.ts
+++ b/packages/contracts/src/__tests__/lease-scope.test.ts
@@ -271,10 +271,15 @@ test('readLeaseAllocateProviderFlags carries a named or invalid spec key as give
 
 test('readLeaseDeviceSpec decides each key is named, not named, or invalid', () => {
   assert.deepEqual(
-    readLeaseDeviceSpec({ osVersion: '>=26', imageTag: 'google_apis', physical: true }),
+    readLeaseDeviceSpec({
+      osVersion: '>=26',
+      imageTag: 'google_apis',
+      deviceMode: 'full',
+      physical: true,
+    }),
     {
-      spec: { osVersion: '>=26', imageTag: 'google_apis', physical: true },
-      keys: ['osVersion', 'imageTag', 'physical'],
+      spec: { osVersion: '>=26', imageTag: 'google_apis', deviceMode: 'full', physical: true },
+      keys: ['osVersion', 'imageTag', 'deviceMode', 'physical'],
       invalidKeys: [],
     },
   );
@@ -282,14 +287,17 @@ test('readLeaseDeviceSpec decides each key is named, not named, or invalid', ()
   assert.deepEqual(readLeaseDeviceSpec(undefined), notNamed);
   assert.deepEqual(readLeaseDeviceSpec({}), notNamed);
   assert.deepEqual(
-    readLeaseDeviceSpec({ osVersion: '', imageTag: '  ', physical: false }),
+    readLeaseDeviceSpec({ osVersion: '', imageTag: '  ', deviceMode: '', physical: false }),
     notNamed,
   );
-  assert.deepEqual(readLeaseDeviceSpec({ osVersion: 26, imageTag: null, physical: 'yes' }), {
-    spec: {},
-    keys: [],
-    invalidKeys: ['osVersion', 'imageTag', 'physical'],
-  });
+  assert.deepEqual(
+    readLeaseDeviceSpec({ osVersion: 26, imageTag: null, deviceMode: true, physical: 'yes' }),
+    {
+      spec: {},
+      keys: [],
+      invalidKeys: ['osVersion', 'imageTag', 'deviceMode', 'physical'],
+    },
+  );
   assert.deepEqual(readLeaseDeviceSpec({ osVersion: '18', physical: 1 }), {
     spec: { osVersion: '18' },
     keys: ['osVersion'],
diff --git a/packages/contracts/src/cli-flags.ts b/packages/contracts/src/cli-flags.ts
index ffb6ea69e0..8ff0d4b9a7 100644
--- a/packages/contracts/src/cli-flags.ts
+++ b/packages/contracts/src/cli-flags.ts
@@ -65,6 +65,7 @@ export type CliFlags = CloudProviderProfileFields &
     // that names any of them, as `readLeaseDeviceSpec` decides.
     osVersion?: string;
     imageTag?: string;
+    deviceMode?: string;
     physical?: boolean;
     stale?: boolean;
     iosSimulatorDeviceSet?: string;
diff --git a/packages/contracts/src/client-lease.ts b/packages/contracts/src/client-lease.ts
index 09ef626b60..49170a007c 100644
--- a/packages/contracts/src/client-lease.ts
+++ b/packages/contracts/src/client-lease.ts
@@ -43,6 +43,8 @@ export type LeaseDeviceSpec = {
   osVersion?: string;
   /** Android system image tag, for example `google_apis_playstore`. */
   imageTag?: string;
+  /** iOS simulator mode, `slim` or `full`; the backend validates it. */
+  deviceMode?: string;
   /** `true` asks for a physical device instead of a simulator or emulator. */
   physical?: boolean;
 };
@@ -53,6 +55,8 @@ export type LeaseDevice = {
   /** The exact OS version granted. */
   osVersion: string;
   imageTag?: string;
+  /** The iOS simulator mode granted, when the backend reports it. */
+  deviceMode?: string;
   physical: boolean;
 };
 
diff --git a/packages/contracts/src/lease-scope.ts b/packages/contracts/src/lease-scope.ts
index 3f6e2b9966..2e71dc5fca 100644
--- a/packages/contracts/src/lease-scope.ts
+++ b/packages/contracts/src/lease-scope.ts
@@ -276,6 +276,7 @@ type LeaseAllocateProviderFlagKey = (typeof LEASE_ALLOCATE_PROVIDER_FLAG_KEYS)[n
 export const LEASE_DEVICE_SPEC_KEYS = [
   'osVersion',
   'imageTag',
+  'deviceMode',
   'physical',
 ] as const satisfies readonly (keyof CommandFlags & keyof LeaseDeviceSpec)[];
 
@@ -330,12 +331,14 @@ export type LeaseDeviceSpecReading = {
 
 /**
  * The one decision on what a device spec names, for the CLI, the SDK, MCP and the daemon alike.
- * Each key is named, not named, or invalid: a non-blank `osVersion` or `imageTag` and
+ * Each key is named, not named, or invalid: a non-blank `osVersion`, `imageTag` or `deviceMode` and
  * `physical: true` are named, with the value as given; an absent key, a blank string and
  * `physical: false` name nothing; any other type is invalid.
  */
 export function readLeaseDeviceSpec(
-  source: { osVersion?: unknown; imageTag?: unknown; physical?: unknown } | undefined,
+  source:
+    | { osVersion?: unknown; imageTag?: unknown; deviceMode?: unknown; physical?: unknown }
+    | undefined,
 ): LeaseDeviceSpecReading {
   const spec: Record<string, string | boolean> = {};
   const invalidKeys: LeaseDeviceSpecKey[] = [];
@@ -367,10 +370,12 @@ export function readLeaseDevice(value: unknown): LeaseDevice | undefined {
   const osVersion = nonEmptyString(record.osVersion);
   if (!model || !osVersion || typeof record.physical !== 'boolean') return undefined;
   const imageTag = nonEmptyString(record.imageTag);
+  const deviceMode = nonEmptyString(record.deviceMode);
   return {
     model,
     osVersion,
     ...(imageTag ? { imageTag } : {}),
+    ...(deviceMode ? { deviceMode } : {}),
     physical: record.physical,
   };
 }
@@ -378,14 +383,14 @@ export function readLeaseDevice(value: unknown): LeaseDevice | undefined {
 /** The refusal for a request whose device spec nothing on its path can honour. */
 export function deviceSpecUnsupportedError(
   keys: readonly string[],
-  message = 'This daemon cannot pick a device by OS version, image tag, or physical/virtual class.',
+  message = 'This daemon cannot pick a device by OS version, image tag, device mode, or physical/virtual class.',
   details: Record<string, unknown> = {},
 ): AppError {
   return new AppError('UNSUPPORTED_OPERATION', message, {
     ...details,
     reason: DEVICE_SPEC_UNSUPPORTED_REASON,
     keys: [...keys],
-    hint: 'Drop --os, --image-tag and --physical, or connect through a proxy whose backend picks devices by spec.',
+    hint: 'Drop --os, --image-tag, --device-mode and --physical, or connect through a proxy whose backend picks devices by spec.',
   });
 }
 
@@ -393,7 +398,7 @@ export function deviceSpecUnsupportedError(
 export function deviceSpecInvalidError(keys: readonly string[]): AppError {
   return new AppError(
     'INVALID_ARGS',
-    'osVersion and imageTag take a string, and physical takes a boolean.',
+    'osVersion, imageTag and deviceMode take a string, and physical takes a boolean.',
     { reason: DEVICE_SPEC_INVALID_REASON, keys: [...keys] },
   );
 }
diff --git a/packages/contracts/src/remote-config-fields.ts b/packages/contracts/src/remote-config-fields.ts
index 8e0e0065ab..4b214d9839 100644
--- a/packages/contracts/src/remote-config-fields.ts
+++ b/packages/contracts/src/remote-config-fields.ts
@@ -151,6 +151,7 @@ export type RemoteConfigProfile = RemoteConfigMetroOptions &
     serial?: string;
     osVersion?: string;
     imageTag?: string;
+    deviceMode?: string;
     physical?: boolean;
     iosSimulatorDeviceSet?: string;
     androidDeviceAllowlist?: string;
diff --git a/packages/contracts/src/request-envelope.ts b/packages/contracts/src/request-envelope.ts
index 3f15542118..a2ff4ffbbd 100644
--- a/packages/contracts/src/request-envelope.ts
+++ b/packages/contracts/src/request-envelope.ts
@@ -70,6 +70,7 @@ export type InternalRequestOptions = AgentDeviceClientConfig &
     surface?: SessionSurface;
     osVersion?: string;
     imageTag?: string;
+    deviceMode?: string;
     physical?: boolean;
     activity?: string;
     launchConsole?: string;
diff --git a/packages/daemon/src/server/__tests__/request-router-device-spec-gate.test.ts b/packages/daemon/src/server/__tests__/request-router-device-spec-gate.test.ts
index 17f9d9f08f..28b4669b1f 100644
--- a/packages/daemon/src/server/__tests__/request-router-device-spec-gate.test.ts
+++ b/packages/daemon/src/server/__tests__/request-router-device-spec-gate.test.ts
@@ -76,6 +76,19 @@ test('a command naming a spec is refused with device-spec-unsupported before it
   expect(systemRuntimeSpies.appSwitcher).not.toHaveBeenCalled();
 });
 
+test('a command naming a device mode is refused with device-spec-unsupported before it runs', async () => {
+  const response = await sendAppSwitcher({ deviceMode: 'full' });
+
+  expect(response).toMatchObject({
+    ok: false,
+    error: {
+      code: 'UNSUPPORTED_OPERATION',
+      details: { reason: 'device-spec-unsupported', keys: ['deviceMode'] },
+    },
+  });
+  expect(systemRuntimeSpies.appSwitcher).not.toHaveBeenCalled();
+});
+
 test('a command giving a spec key the wrong type is refused with device-spec-invalid before it runs', async () => {
   // The named osVersion would be refused as unsupported; the invalid key is reported instead.
   const response = await sendAppSwitcher({
diff --git a/packages/remote/src/remote-config-schema.ts b/packages/remote/src/remote-config-schema.ts
index 7189b3a0a0..6f12cf86d5 100644
--- a/packages/remote/src/remote-config-schema.ts
+++ b/packages/remote/src/remote-config-schema.ts
@@ -50,6 +50,7 @@ export const REMOTE_CONFIG_FIELD_SPECS = [
   // The device spec only a proxy backend honours; no environment variable sets it.
   { key: 'osVersion', type: 'string', env: false },
   { key: 'imageTag', type: 'string', env: false },
+  { key: 'deviceMode', type: 'string', env: false },
   { key: 'physical', type: 'boolean', env: false },
   {
     key: 'iosSimulatorDeviceSet',
diff --git a/scripts/integration-progress-model.ts b/scripts/integration-progress-model.ts
index 7bc99ffd24..2cb9b2f827 100644
--- a/scripts/integration-progress-model.ts
+++ b/scripts/integration-progress-model.ts
@@ -255,7 +255,7 @@ function summarizeProviderScenarioFlagExclusions() {
       // The device spec is honoured by a backend in front of the daemon; the daemon only refuses it.
       name: 'proxy lease device spec',
       owner: 'proxy allocate-by-spec, request-router refusal, and lease-scope tests',
-      keys: ['osVersion', 'imageTag', 'physical'],
+      keys: ['osVersion', 'imageTag', 'deviceMode', 'physical'],
     },
     {
       name: 'cloud artifact provider lookup',
diff --git a/src/cli/commands/__tests__/proxy-lease-device-spec.test.ts b/src/cli/commands/__tests__/proxy-lease-device-spec.test.ts
index a9d3f7f6f7..0b120eca98 100644
--- a/src/cli/commands/__tests__/proxy-lease-device-spec.test.ts
+++ b/src/cli/commands/__tests__/proxy-lease-device-spec.test.ts
@@ -6,7 +6,8 @@ import {
 import { test, vi } from 'vitest';
 import assert from 'node:assert/strict';
 import fs from 'node:fs';
-import type { LeaseDevice } from '@agent-device/contracts/client';
+import type { LeaseDevice, LeaseDeviceSpec } from '@agent-device/contracts/client';
+import { LEASE_DEVICE_SPEC_KEYS } from '@agent-device/contracts/lease-scope';
 import { AppError } from '@agent-device/kernel/errors';
 import {
   connectionWorkspace,
@@ -63,16 +64,23 @@ function renewingClient(heartbeats: string[]) {
 test('proxy open by device spec sends the spec on allocate without listing devices and reports the granted device', async () => {
   const { tempRoot, stateDir, flags } = proxyWorkspace('agent-device-proxy-device-spec-');
   const requests: LeaseAllocateRequest[] = [];
+  const spec: Required<LeaseDeviceSpec> = {
+    osVersion: ' >=26 ',
+    imageTag: 'google_apis',
+    deviceMode: 'full',
+    physical: true,
+  };
+  const grantedDevice: LeaseDevice = { ...GRANTED_DEVICE, deviceMode: 'full' };
 
   const materialized = await materializeRemoteConnectionForCommand({
     host: createTestHostEnvironment(),
     command: 'open',
-    flags: { ...flags, device: 'iPhone 17 Pro', osVersion: ' >=26 ', physical: true },
+    flags: { ...flags, device: 'iPhone 17 Pro', ...spec },
     client: createTestClient({
       listDevices: unexpectedCommandCall,
       allocate: async (request) => {
         requests.push(request);
-        return grantedLease(request, { deviceKey: REMOTE_DEVICE_KEY, device: GRANTED_DEVICE });
+        return grantedLease(request, { deviceKey: REMOTE_DEVICE_KEY, device: grantedDevice });
       },
       release: unexpectedCommandCall,
     }),
@@ -82,21 +90,95 @@ test('proxy open by device spec sends the spec on allocate without listing devic
   assert.equal(requests[0]?.deviceKey, undefined);
   assert.equal(requests[0]?.platform, 'ios');
   assert.equal(requests[0]?.device, 'iPhone 17 Pro');
-  assert.equal(requests[0]?.osVersion, ' >=26 ');
-  assert.equal(requests[0]?.physical, true);
-  assert.equal(requests[0]?.imageTag, undefined);
-  assert.deepEqual(materialized.leaseDevice, GRANTED_DEVICE);
+  assert.deepEqual(materialized.leaseDevice, grantedDevice);
   // The leased device is named by its identity from here on; the spec does not reach the command.
   assert.equal(materialized.flags.udid, 'SIM-REMOTE');
-  assert.equal(materialized.flags.osVersion, undefined);
-  assert.equal(materialized.flags.physical, undefined);
+  for (const key of LEASE_DEVICE_SPEC_KEYS) {
+    assert.equal(requests[0]?.[key], spec[key]);
+    assert.equal(materialized.flags[key], undefined);
+  }
   const state = readRemoteConnectionState({ stateDir, session: 'adc-proxy' });
   assert.equal(state?.leaseId, 'lease-1');
   assert.deepEqual(state?.leaseDeviceSpec, {
     leaseId: 'lease-1',
-    spec: { osVersion: ' >=26 ', physical: true },
-    device: GRANTED_DEVICE,
+    spec,
+    device: grantedDevice,
+  });
+  fs.rmSync(tempRoot, { recursive: true, force: true });
+});
+
+test('a slim grant for a full request is released and refused', async () => {
+  const { tempRoot, stateDir, flags } = proxyWorkspace('agent-device-proxy-spec-wrong-mode-');
+  const releases: LeaseReleaseRequest[] = [];
+  await assert.rejects(
+    materializeRemoteConnectionForCommand({
+      host: createTestHostEnvironment(),
+      command: 'open',
+      flags: { ...flags, deviceMode: 'full' },
+      client: createTestClient({
+        listDevices: unexpectedCommandCall,
+        allocate: async (request) =>
+          grantedLease(request, {
+            created: true,
+            deviceKey: REMOTE_DEVICE_KEY,
+            device: { ...GRANTED_DEVICE, deviceMode: 'slim' },
+          }),
+        release: async (request) => {
+          releases.push(request);
+          return { released: true };
+        },
+      }),
+    }),
+    (error: AppError) =>
+      error.code === 'UNSUPPORTED_OPERATION' &&
+      error.details?.reason === 'device-spec-unsupported' &&
+      JSON.stringify(error.details?.keys) === '["deviceMode"]',
+  );
+  assert.deepEqual(
+    releases.map((request) => request.leaseId),
+    ['lease-1'],
+  );
+  assert.equal(readRemoteConnectionState({ stateDir, session: 'adc-proxy' })?.leaseId, undefined);
+  fs.rmSync(tempRoot, { recursive: true, force: true });
+});
+
+test('a full grant serves a slim request, because slim is best effort', async () => {
+  const { tempRoot, flags } = proxyWorkspace('agent-device-proxy-spec-slim-full-');
+  const device: LeaseDevice = { ...GRANTED_DEVICE, deviceMode: 'full' };
+
+  const materialized = await materializeRemoteConnectionForCommand({
+    host: createTestHostEnvironment(),
+    command: 'open',
+    flags: { ...flags, deviceMode: 'slim' },
+    client: createTestClient({
+      listDevices: unexpectedCommandCall,
+      allocate: async (request) => grantedLease(request, { deviceKey: REMOTE_DEVICE_KEY, device }),
+      release: unexpectedCommandCall,
+    }),
+  });
+
+  assert.equal(materialized.flags.udid, 'SIM-REMOTE');
+  assert.deepEqual(materialized.leaseDevice, device);
+  fs.rmSync(tempRoot, { recursive: true, force: true });
+});
+
+test('a grant that reports no device mode serves a request naming one', async () => {
+  const { tempRoot, flags } = proxyWorkspace('agent-device-proxy-spec-no-mode-echo-');
+
+  const materialized = await materializeRemoteConnectionForCommand({
+    host: createTestHostEnvironment(),
+    command: 'open',
+    flags: { ...flags, deviceMode: 'full' },
+    client: createTestClient({
+      listDevices: unexpectedCommandCall,
+      allocate: async (request) =>
+        grantedLease(request, { deviceKey: REMOTE_DEVICE_KEY, device: GRANTED_DEVICE }),
+      release: unexpectedCommandCall,
+    }),
   });
+
+  assert.equal(materialized.flags.udid, 'SIM-REMOTE');
+  assert.deepEqual(materialized.leaseDevice, GRANTED_DEVICE);
   fs.rmSync(tempRoot, { recursive: true, force: true });
 });
 
@@ -479,7 +561,13 @@ test('a lease re-allocated by its stored device for a non-allocating command doe
   await materializeRemoteConnectionForCommand({
     host: createTestHostEnvironment(),
     command: 'snapshot',
-    flags: { ...flags, osVersion: '>=26' },
+    flags: {
+      ...flags,
+      osVersion: '>=26',
+      imageTag: 'google_apis',
+      deviceMode: 'full',
+      physical: true,
+    },
     client: createTestClient({
       listDevices: unexpectedCommandCall,
       heartbeat: async () => {
@@ -494,7 +582,7 @@ test('a lease re-allocated by its stored device for a non-allocating command doe
 
   assert.equal(requests.length, 1);
   assert.equal(requests[0]?.deviceKey, 'ios:mobile:SIM-REMOTE');
-  assert.equal(requests[0]?.osVersion, undefined);
+  for (const key of LEASE_DEVICE_SPEC_KEYS) assert.equal(requests[0]?.[key], undefined);
   fs.rmSync(tempRoot, { recursive: true, force: true });
 });
 
@@ -542,6 +630,7 @@ test('connect proxy stores the device spec as profile defaults like platform and
         platform: 'android',
         osVersion: '34',
         imageTag: 'google_apis_playstore',
+        deviceMode: 'full',
         physical: true,
       },
       client: createTestClient(),
@@ -557,6 +646,7 @@ test('connect proxy stores the device spec as profile defaults like platform and
   assert.equal(generated.platform, 'android');
   assert.equal(generated.osVersion, '34');
   assert.equal(generated.imageTag, 'google_apis_playstore');
+  assert.equal(generated.deviceMode, 'full');
   assert.equal(generated.physical, true);
   fs.rmSync(tempRoot, { recursive: true, force: true });
 });
@@ -576,6 +666,7 @@ test('connect proxy stores no default for a spec key that names nothing', async
         platform: 'android',
         osVersion: '',
         imageTag: ' ',
+        deviceMode: '',
         physical: false,
       },
       client: createTestClient(),
@@ -589,8 +680,6 @@ test('connect proxy stores no default for a spec key that names nothing', async
     unknown
   >;
   assert.equal(generated.platform, 'android');
-  assert.equal('osVersion' in generated, false);
-  assert.equal('imageTag' in generated, false);
-  assert.equal('physical' in generated, false);
+  for (const key of LEASE_DEVICE_SPEC_KEYS) assert.equal(key in generated, false);
   fs.rmSync(tempRoot, { recursive: true, force: true });
 });
diff --git a/src/cli/commands/connection-lease-transaction.ts b/src/cli/commands/connection-lease-transaction.ts
index 9a43e09a05..322524aea9 100644
--- a/src/cli/commands/connection-lease-transaction.ts
+++ b/src/cli/commands/connection-lease-transaction.ts
@@ -1,6 +1,7 @@
 import { PUBLIC_COMMANDS } from '@agent-device/command-registry/catalog';
 import {
   isInactiveLeaseError,
+  LEASE_DEVICE_SPEC_KEYS,
   readLeaseAllocateProviderFlags,
   requireLeaseDeviceSpec,
 } from '@agent-device/contracts/lease-scope';
@@ -376,12 +377,8 @@ async function allocateOrReuseLease(
     });
   }
   // The spec rides only a by-spec allocate, so it is added below rather than taken from the flags.
-  const {
-    osVersion: _osVersion,
-    imageTag: _imageTag,
-    physical: _physical,
-    ...providerFlags
-  } = readLeaseAllocateProviderFlags(flags);
+  const providerFlags = readLeaseAllocateProviderFlags(flags);
+  for (const key of LEASE_DEVICE_SPEC_KEYS) delete providerFlags[key];
   const lease = await client.leases.allocate({
     tenant: state.tenant,
     runId: state.runId,
diff --git a/src/cli/commands/proxy-lease-device.ts b/src/cli/commands/proxy-lease-device.ts
index b677491509..a403945960 100644
--- a/src/cli/commands/proxy-lease-device.ts
+++ b/src/cli/commands/proxy-lease-device.ts
@@ -14,6 +14,7 @@ import {
 import { AppError } from '@agent-device/kernel/errors';
 import {
   deviceSpecUnsupportedError,
+  LEASE_DEVICE_SPEC_KEYS,
   requireLeaseDeviceSpec,
 } from '@agent-device/contracts/lease-scope';
 import type { Lease, LeaseDevice, LeaseDeviceSpec } from '@agent-device/contracts/client';
@@ -63,7 +64,7 @@ export async function resolveProxyLeaseState(options: {
     if (!options.leaseBackend) {
       throw new AppError(
         'INVALID_ARGS',
-        `${options.command} with --os, --image-tag or --physical requires --platform or --lease-backend so the proxy backend knows which device family to pick from.`,
+        `${options.command} with --os, --image-tag, --device-mode or --physical requires --platform or --lease-backend so the proxy backend knows which device family to pick from.`,
       );
     }
     return { state: options.state, allocateBySpec: true };
@@ -109,8 +110,9 @@ async function resolveProxyLeaseStateLocally(options: {
  * none was supplied from outside, so it is refused and never released.
  *
  * A request that names a device spec has no such fallback: a new lease that does not echo the
- * granted device in `lease.device` came from a backend that ignored the spec, so it is released and
- * the request fails with `device-spec-unsupported`. A renewed lease serves the request only when
+ * granted device in `lease.device`, or that reports a slim simulator for a `full` request,
+ * did not honour the spec, so it is released and the request fails with `device-spec-unsupported`.
+ * A lease that reports no mode is accepted: the mode is then unconfirmed. A renewed lease serves the request only when
  * every spec key the request names equals the one the lease was allocated by. Once a lease is bound,
  * the spec leaves the command flags: the device it chose is named by its identity instead.
  */
@@ -127,7 +129,7 @@ export async function bindLeaseNamedDevice(options: {
   const { lease, acquired } = materialized;
   const { spec, keys: specKeys } = requireLeaseDeviceSpec(flags);
   const leased = parseConnectionDeviceKey(lease.deviceKey);
-  if (acquired && specKeys.length > 0 && (!lease.device || !leased)) {
+  if (acquired && specKeys.length > 0 && (!leased || !leaseHonoursSpec(lease, spec))) {
     throw await refuseUnhonouredSpecLease(leaseLedger, options.state, lease, specKeys);
   }
   if (leased) {
@@ -138,9 +140,7 @@ export async function bindLeaseNamedDevice(options: {
       await assertLeasedDeviceMatchesRequest(client, options.state, flags, leased);
     }
     applyDeviceScopeSelector(flags, leased);
-    delete flags.osVersion;
-    delete flags.imageTag;
-    delete flags.physical;
+    for (const key of LEASE_DEVICE_SPEC_KEYS) delete flags[key];
     return {
       state: {
         ...options.state,
@@ -165,6 +165,12 @@ export async function bindLeaseNamedDevice(options: {
 }
 
 /** A refused allocation is discarded unless the daemon explicitly reported reuse. */
+function leaseHonoursSpec(lease: Lease, spec: LeaseDeviceSpec): boolean {
+  if (!lease.device) return false;
+  // Full is a guarantee and slim is best effort, so a full grant serves a slim request.
+  return !(spec.deviceMode === 'full' && lease.device.deviceMode === 'slim');
+}
+
 async function refuseUnhonouredSpecLease(
   leaseLedger: LeaseLedger,
   state: RemoteConnectionState,
diff --git a/src/commands/schema/cli-help.ts b/src/commands/schema/cli-help.ts
index 47b34af2b6..b4a8e203c7 100644
--- a/src/commands/schema/cli-help.ts
+++ b/src/commands/schema/cli-help.ts
@@ -570,10 +570,10 @@ Direct proxy flow for a remote Mac/simulator:
 Leased sessions: a connection from connect proxy, connect (cloud), another connect provider, or a remote config that sets leaseProvider leases its device for one agent. Every command on it, from connect to disconnect, names its session with --session <name>, AGENT_DEVICE_SESSION, or a config session. Without one, it fails with INVALID_ARGS, reason REMOTE_SESSION_REQUIRED, before anything is leased, and never falls back to the connection another agent on the machine saved last. Set AGENT_DEVICE_SESSION once per agent or CI job before connect.
 
 Proxy lease by device spec:
-  Without --udid or --serial, open, install, reinstall, and uninstall through connect proxy send --platform, --target, and --device on the lease allocate, and the backend in front of the daemon picks the device. --os <version|range>, --image-tag <tag>, and --physical add a device spec to that request. A non-blank osVersion or imageTag and physical: true name a spec key, sent as given; the backend validates its value (for example, Android --os is an API level). A blank string and physical: false name nothing, from the CLI, the SDK, or MCP. A value of another type fails with INVALID_ARGS, reason device-spec-invalid. connect proxy stores the spec keys it names as defaults like --platform and --device.
+  Without --udid or --serial, open, install, reinstall, and uninstall through connect proxy send --platform, --target, and --device on the lease allocate, and the backend in front of the daemon picks the device. --os <version|range>, --image-tag <tag>, --device-mode <slim|full>, and --physical add a device spec to that request. A non-blank osVersion, imageTag or deviceMode and physical: true name a spec key, sent as given; the backend validates its value (for example, Android --os is an API level, and --device-mode full asks for an unslimmed iOS simulator). A blank string and physical: false name nothing, from the CLI, the SDK, or MCP. A value of another type fails with INVALID_ARGS, reason device-spec-invalid. connect proxy stores the spec keys it names as defaults like --platform and --device.
     agent-device open MyApp --platform ios --device "iPhone 17 Pro" --os ">=26"
     agent-device open MyApp --platform android --os 34 --image-tag google_apis_playstore
-  A backend that honours the spec returns the granted device as lease.device (model, osVersion, imageTag, physical); open --json prints it. A daemon, local or behind agent-device proxy, refuses a request that names a spec key with UNSUPPORTED_OPERATION, reason device-spec-unsupported, and details.keys, and records no lease. When the backend returns a lease without lease.device, the CLI releases that lease. The command then fails with UNSUPPORTED_OPERATION, reason device-spec-unsupported, and details.released reports whether the release succeeded. A live lease serves a later command only when every spec key the command names equals the one the lease was allocated by; otherwise the command fails with reason CONNECTION_DEVICE_CONFLICT. Run connect --force to lease by another spec.
+  A backend that honours the spec returns the granted device as lease.device (model, osVersion, imageTag, physical, and deviceMode when it reports one); open --json prints it. A lease that reports no deviceMode is accepted without confirming the mode. A daemon, local or behind agent-device proxy, refuses a request that names a spec key with UNSUPPORTED_OPERATION, reason device-spec-unsupported, and details.keys, and records no lease. When the backend returns a lease without lease.device, or with deviceMode slim for a full request, the CLI releases that lease, unless the allocation explicitly reports reuse (created: false). The command then fails with UNSUPPORTED_OPERATION, reason device-spec-unsupported, and details.released reports whether a release it attempted succeeded. A live lease serves a later command only when every spec key the command names equals the one the lease was allocated by; otherwise the command fails with reason CONNECTION_DEVICE_CONFLICT. Run connect --force to lease by another spec.
 
 Human takeover of a leased remote device:
   Run agent-device takeover using the active remote connection and session. It pauses state-changing agent commands until Ctrl+C while snapshots and other read-only diagnostics remain available. Tenant requests can control only their admitted lease device. Local takeover without a remote device lease is not supported.
diff --git a/src/mcp/__tests__/command-tools-operator-inputs.test.ts b/src/mcp/__tests__/command-tools-operator-inputs.test.ts
index 233b544312..075c163d00 100644
--- a/src/mcp/__tests__/command-tools-operator-inputs.test.ts
+++ b/src/mcp/__tests__/command-tools-operator-inputs.test.ts
@@ -3,6 +3,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { test, vi } from 'vitest';
 import type { AgentDeviceClient } from '@agent-device/command-surface';
+import { LEASE_DEVICE_SPEC_KEYS } from '@agent-device/contracts/lease-scope';
 import { mkdtempForTestSync } from '@agent-device/test-kit';
 import { createCommandToolExecutor, listCommandTools } from '../command-tools.ts';
 
@@ -265,7 +266,7 @@ test('MCP open, install, reinstall and uninstall advertise the proxy lease devic
     const tool = listCommandTools().find((candidate) => candidate.name === name);
     assert.ok(tool, `expected an MCP tool named ${name}`);
     const properties = tool.inputSchema.properties ?? {};
-    for (const key of ['osVersion', 'imageTag', 'physical']) {
+    for (const key of LEASE_DEVICE_SPEC_KEYS) {
       assert.equal(key in properties, true, `${name} does not advertise ${key}`);
     }
   }
diff --git a/website/docs/docs/remote-proxy.md b/website/docs/docs/remote-proxy.md
index 4f7819c217..a6858286bb 100644
--- a/website/docs/docs/remote-proxy.md
+++ b/website/docs/docs/remote-proxy.md
@@ -60,25 +60,27 @@ config, an explicit `--config` file, or protected CI environment variables.
 
 ## Lease by device spec
 
-A service in front of the daemon, such as simlock, can also pick the device by OS version, Android image tag, and physical or virtual class. Pass `--os <version|range>`, `--image-tag <tag>`, or `--physical` to `open`, `install`, `reinstall`, or `uninstall`, and the CLI sends them with `--platform`, `--target`, and `--device` on the lease request. A non-blank `osVersion` or `imageTag` and `physical: true` name a spec key and are sent as given. An empty or blank string and `physical: false` name nothing, from the CLI, the SDK, or MCP. A value of another type (for example `physical: "yes"`) fails with `INVALID_ARGS` and `details.reason: "device-spec-invalid"`. The service validates the values themselves (for example, Android `--os` is an API level). `connect proxy` stores the spec keys it names as defaults like `--platform` and `--device`. `--target` stays the device class selector.
+A service in front of the daemon, such as simlock, can also pick the device by OS version, Android image tag, iOS simulator mode, and physical or virtual class. Pass `--os <version|range>`, `--image-tag <tag>`, `--device-mode <slim|full>`, or `--physical` to `open`, `install`, `reinstall`, or `uninstall`, and the CLI sends them with `--platform`, `--target`, and `--device` on the lease request. A non-blank `osVersion`, `imageTag` or `deviceMode` and `physical: true` name a spec key and are sent as given. An empty or blank string and `physical: false` name nothing, from the CLI, the SDK, or MCP. A value of another type (for example `physical: "yes"`) fails with `INVALID_ARGS` and `details.reason: "device-spec-invalid"`. The service validates the values themselves (for example, Android `--os` is an API level). `connect proxy` stores the spec keys it names as defaults like `--platform` and `--device`. `--target` stays the device class selector.
 
 ```bash
 agent-device open MyApp --platform ios --device "iPhone 17 Pro" --os ">=26"
 agent-device open MyApp --platform android --os 34 --image-tag google_apis_playstore
 agent-device open MyApp --platform ios --physical --os 18.6.2
+agent-device open MyApp --platform ios --device-mode full
 ```
 
 | Flag | Key on `agent_device.lease.allocate` | Type |
 | --- | --- | --- |
 | `--os <version\|range>` | `osVersion` | string |
 | `--image-tag <tag>` | `imageTag` | string |
+| `--device-mode <slim\|full>` | `deviceMode` | string |
 | `--physical` | `physical` | `true` |
 
 With `--physical`, the service leases one of the real phones enrolled with it instead of a simulator or emulator.
 
-A service that honours the spec returns the granted device on the lease as `lease.device`: `model`, `osVersion` (the exact OS granted), `imageTag` when one applies, and `physical`. `open --json` prints it under `lease.device`.
+A service that honours the spec returns the granted device on the lease as `lease.device`: `model`, `osVersion` (the exact OS granted), `imageTag` when one applies, and `physical`. `open --json` prints it under `lease.device`. A service can also report the granted simulator mode there as `deviceMode`. A lease that reports `slim` for `--device-mode full` fails the command with reason `device-spec-unsupported`, and is released unless the daemon explicitly reported `created:false` (reuse). `slim` is best effort, so a `full` simulator can serve `--device-mode slim`. A lease that reports no mode is accepted, so `--device-mode` needs a service that supports the key: one that ignores it and reports no mode leases its default mode without an error.
 
-The daemon itself cannot pick a device by these keys, so it refuses a named key instead of ignoring it. A local daemon, or one behind a plain `agent-device proxy`, fails such a request with `UNSUPPORTED_OPERATION`, `details.reason: "device-spec-unsupported"`, and `details.keys` naming the keys it got, and records no lease. When a service returns a lease without `lease.device`, the service did not understand the spec. The CLI discards that allocate response and fails with `UNSUPPORTED_OPERATION` and `details.reason: "device-spec-unsupported"`. It releases a discarded lease unless the daemon explicitly reported `created:false` (reuse). This also applies when a grant conflicts with `--udid` or `--serial`, or when a keyless lease is replaced by the locally selected device. `details.released`, when present, reports whether the lease was released. If release throws while discarding a refused or conflicting allocation and the daemon confirmed `created:true`, the command retries that release once. A retry that releases the lease records `released:true`. Keyless fallback stops if discarding the replaced lease throws, to avoid leaving an unnamed lease while allocating another. A failed discard or rollback uses one `details.leaseRollback` shape: it names the lease and carries `released: false`, reason `LEASE_RELEASE_FAILED`, and the release error alongside the original command error. An older daemon that omits creation evidence still has refused or replaced leases released. Once its grant is bound, a later preparation failure leaves that unrecorded lease until expiry because rollback requires `created:true`. While a lease is active, a later command that names a different value for any of the three keys fails with reason `CONNECTION_DEVICE_CONFLICT`; a key the command leaves out keeps the lease's value. Run `connect --force` to lease by another spec.
+The daemon itself cannot pick a device by these keys, so it refuses a named key instead of ignoring it. A local daemon, or one behind a plain `agent-device proxy`, fails such a request with `UNSUPPORTED_OPERATION`, `details.reason: "device-spec-unsupported"`, and `details.keys` naming the keys it got, and records no lease. When a service returns a lease without `lease.device`, the service did not understand the spec. The CLI discards that allocate response and fails with `UNSUPPORTED_OPERATION` and `details.reason: "device-spec-unsupported"`. It releases a discarded lease unless the daemon explicitly reported `created:false` (reuse). This also applies when a grant conflicts with `--udid` or `--serial`, or when a keyless lease is replaced by the locally selected device. `details.released`, when present, reports whether the lease was released. If release throws while discarding a refused or conflicting allocation and the daemon confirmed `created:true`, the command retries that release once. A retry that releases the lease records `released:true`. Keyless fallback stops if discarding the replaced lease throws, to avoid leaving an unnamed lease while allocating another. A failed discard or rollback uses one `details.leaseRollback` shape: it names the lease and carries `released: false`, reason `LEASE_RELEASE_FAILED`, and the release error alongside the original command error. An older daemon that omits creation evidence still has refused or replaced leases released. Once its grant is bound, a later preparation failure leaves that unrecorded lease until expiry because rollback requires `created:true`. While a lease is active, a later command that names a different value for any of the four keys fails with reason `CONNECTION_DEVICE_CONFLICT`; a key the command leaves out keeps the lease's value. Run `connect --force` to lease by another spec.
 
 ## Download captures