diff --git a/apps/api/src/application/identity/device-identity-service.test.ts b/apps/api/src/application/identity/device-identity-service.test.ts
new file mode 100644
index 0000000..8805402
--- /dev/null
+++ b/apps/api/src/application/identity/device-identity-service.test.ts
@@ -0,0 +1,245 @@
+import Database from 'better-sqlite3';
+import { describe, expect, it } from 'vitest';
+
+import { migrateDatabase } from '../../infrastructure/database/migrations.js';
+import { DeviceIdentityError, DeviceIdentityService } from './device-identity-service.js';
+
+interface Fixture {
+  readonly db: Database.Database;
+  readonly service: DeviceIdentityService;
+  readonly advance: (minutes: number) => void;
+}
+
+function fixture(): Fixture {
+  const db = new Database(':memory:');
+  db.pragma('foreign_keys=ON');
+  migrateDatabase(db);
+  let clock = new Date('2026-09-05T02:00:00.000Z');
+  const service = new DeviceIdentityService({ db, now: () => clock });
+  return {
+    db,
+    service,
+    advance: (minutes: number) => {
+      clock = new Date(clock.getTime() + minutes * 60_000);
+    },
+  };
+}
+
+function manualFixture() {
+  const db = new Database(':memory:');
+  db.pragma('foreign_keys=ON');
+  migrateDatabase(db);
+  let clock = new Date('2026-09-05T02:00:00.000Z');
+  const service = new DeviceIdentityService({
+    db,
+    now: () => clock,
+    authorizationMode: () => 'manual',
+  });
+  return {
+    db,
+    service,
+    advance: (minutes: number) => {
+      clock = new Date(clock.getTime() + minutes * 60_000);
+    },
+  };
+}
+
+function register(db: Database.Database, id: string): void {
+  db.prepare(
+    `INSERT INTO instances
+      (id,name,base_url,auth_mode,enabled,config_revision,created_at,updated_at)
+     VALUES (?,?,?,'password',1,1,?,?)`,
+  ).run(id, id, `http://${id}.lan:8080`, '2026-09-05T02:00:00.000Z', '2026-09-05T02:00:00.000Z');
+}
+
+const device = (overrides: Record<string, unknown> = {}) => ({
+  imei: '860000000000001',
+  manufacturer: 'Quectel',
+  model: 'RM500Q',
+  revision: 'RM500QEAAAR13',
+  ...overrides,
+});
+
+describe('DeviceIdentityService', () => {
+  it('baselines the first report instead of calling it a conflict', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+
+    const identity = service.observe('a', { ...device(), origin: 'http://a.lan:8080' });
+
+    expect(identity).toMatchObject({
+      instanceId: 'a',
+      status: 'confirmed',
+      reasons: [],
+      imei: '860000000000001',
+      model: 'RM500Q',
+      origin: 'http://a.lan:8080',
+    });
+    expect(service.isBlocked('a')).toBe(false);
+  });
+
+  it('keeps a device that reports no identity out of the guard', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+
+    expect(service.observe('a', { agent: 'simadmin-agent 1.9.6' })).toBeUndefined();
+    expect(service.observe('a', { imei: '   ' })).toBeUndefined();
+    expect(service.list()).toEqual([]);
+  });
+
+  it('holds a first report until an operator confirms it in manual authorization mode', () => {
+    const { db, service } = manualFixture();
+    register(db, 'a');
+
+    const identity = service.observe('a', device());
+
+    expect(identity).toMatchObject({
+      instanceId: 'a',
+      status: 'pending',
+      reasons: [],
+      imei: '860000000000001',
+    });
+    expect(service.isBlocked('a')).toBe(true);
+    expect(service.confirm('a')).toMatchObject({ status: 'confirmed', reasons: [] });
+    expect(service.isBlocked('a')).toBe(false);
+  });
+
+  it('holds a node whose hardware no longer matches the record', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    service.observe('a', device());
+
+    const swapped = service.observe('a', device({ model: 'RG500Q', imei: '860000000000009' }));
+
+    expect(swapped?.status).toBe('pending');
+    expect(swapped?.reasons).toEqual(['hardware_swapped']);
+    expect(swapped?.changes).toEqual([
+      { field: 'imei', from: '860000000000001', to: '860000000000009' },
+      { field: 'model', from: 'RM500Q', to: 'RG500Q' },
+    ]);
+    expect(service.isBlocked('a')).toBe(true);
+  });
+
+  it('compares only the fields a partial report actually carries', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    service.observe('a', device());
+
+    const partial = service.observe('a', { model: 'RM500Q' });
+
+    expect(partial?.status).toBe('confirmed');
+    expect(partial?.reasons).toEqual([]);
+    // The dropped fields stay on the row: a silent read must not erase what we already knew.
+    expect(partial?.imei).toBe('860000000000001');
+  });
+
+  it('asks both records when one identity is claimed twice', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    register(db, 'b');
+    service.observe('a', device());
+
+    const newcomer = service.observe('b', device());
+
+    expect(newcomer?.status).toBe('pending');
+    expect(newcomer?.reasons).toEqual(['imei_claimed']);
+    expect(newcomer?.conflicts).toEqual([{ reason: 'imei_claimed', instanceIds: ['a'] }]);
+    expect(service.get('a')?.status).toBe('pending');
+    expect(service.get('a')?.conflicts).toEqual([{ reason: 'imei_claimed', instanceIds: ['b'] }]);
+    expect(service.summarize()).toEqual({ tracked: 2, pending: ['a', 'b'] });
+  });
+
+  it('accepts the twins that were on screen when the operator confirmed', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    register(db, 'b');
+    service.observe('a', device());
+    service.observe('b', device());
+
+    expect(service.confirm('a')).toMatchObject({ status: 'confirmed', reasons: [] });
+    service.observe('a', device());
+    expect(service.get('a')?.status).toBe('confirmed');
+
+    // A third claimant is new information, so the guard comes back down.
+    register(db, 'c');
+    service.observe('c', device());
+    expect(service.get('a')?.status).toBe('pending');
+    // 'b' was on screen when the operator confirmed; only the newcomer is still a question.
+    expect(service.get('a')?.conflicts).toEqual([{ reason: 'imei_claimed', instanceIds: ['c'] }]);
+  });
+
+  it('re-baselines swapped hardware on confirmation', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    service.observe('a', device());
+    service.observe('a', device({ model: 'RG500Q' }));
+
+    const confirmed = service.confirm('a');
+
+    expect(confirmed).toMatchObject({ status: 'confirmed', reasons: [], changes: [] });
+    expect(service.isBlocked('a')).toBe(false);
+    service.observe('a', device({ model: 'RG500Q' }));
+    expect(service.get('a')?.status).toBe('confirmed');
+    service.observe('a', device({ model: 'EM120' }));
+    expect(service.get('a')?.reasons).toEqual(['hardware_swapped']);
+  });
+
+  it('sanitizes device-controlled evidence before it is stored', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+
+    const identity = service.observe('a', {
+      imei: '  860000000000001\u0000\u001b  ',
+      model: 'x'.repeat(200),
+      revision: 42,
+      manufacturer: null,
+    });
+
+    expect(identity?.imei).toBe('860000000000001');
+    expect(identity?.model).toHaveLength(64);
+    expect(identity?.revision).toBe('42');
+    expect(identity?.manufacturer).toBe('');
+  });
+
+  it('reports a missing identity rather than inventing one on confirm', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+
+    expect(() => service.confirm('a')).toThrow(DeviceIdentityError);
+    try {
+      service.confirm('a');
+    } catch (error) {
+      expect(error).toBeInstanceOf(DeviceIdentityError);
+      expect((error as DeviceIdentityError).code).toBe('NOT_FOUND');
+    }
+  });
+
+  it('forgets the identity with the node it belonged to', () => {
+    const { db, service } = fixture();
+    register(db, 'a');
+    register(db, 'b');
+    service.observe('a', device());
+    service.observe('b', device());
+
+    db.prepare('DELETE FROM instances WHERE id=?').run('b');
+
+    // The row goes with the node, and the survivor is released the next time anything reads it.
+    expect(service.list().map((identity) => identity.instanceId)).toEqual(['a']);
+    expect(service.get('a')).toMatchObject({ status: 'pending' });
+    expect(service.observe('a', device())).toMatchObject({ status: 'confirmed', reasons: [] });
+  });
+
+  it('advances the observation time without touching the confirmation time', () => {
+    const { db, service, advance } = fixture();
+    register(db, 'a');
+    const first = service.observe('a', device());
+    expect(first?.observedAt).toBe('2026-09-05T02:00:00.000Z');
+
+    advance(5);
+    const second = service.observe('a', device());
+
+    expect(second?.observedAt).toBe('2026-09-05T02:05:00.000Z');
+    expect(second?.confirmedAt).toBe('2026-09-05T02:00:00.000Z');
+    expect(second?.fingerprint).toBe(first?.fingerprint);
+  });
+});
diff --git a/apps/api/src/application/identity/device-identity-service.ts b/apps/api/src/application/identity/device-identity-service.ts
new file mode 100644
index 0000000..b66e338
--- /dev/null
+++ b/apps/api/src/application/identity/device-identity-service.ts
@@ -0,0 +1,461 @@
+import { createHash } from 'node:crypto';
+
+import type Database from 'better-sqlite3';
+
+export type IdentityStatus = 'confirmed' | 'pending';
+
+/**
+ * `hardware_swapped` is the record that used to answer at this address reporting different
+ * hardware now; `imei_claimed` is a second record answering with the same identity. Neither can
+ * be resolved from here, which is why both stop control traffic until an operator says which
+ * device is the real one.
+ */
+export type IdentityReason = 'hardware_swapped' | 'imei_claimed';
+
+const IDENTITY_FIELDS = ['imei', 'manufacturer', 'model', 'revision'] as const;
+type IdentityField = (typeof IDENTITY_FIELDS)[number];
+type IdentityValues = Partial<Record<IdentityField, string>>;
+
+const MAX_FIELD_LENGTH: Readonly<Record<IdentityField | 'agent' | 'origin', number>> = {
+  imei: 32,
+  manufacturer: 64,
+  model: 64,
+  revision: 64,
+  agent: 64,
+  origin: 256,
+};
+
+const CONTROL_CHARACTERS = /[\u0000-\u0008\u000b\u000c\u000e-\u001f\u007f]/gu;
+
+export interface DeviceIdentityEvidence {
+  readonly imei?: unknown;
+  readonly manufacturer?: unknown;
+  readonly model?: unknown;
+  readonly revision?: unknown;
+  readonly agent?: unknown;
+  readonly origin?: unknown;
+}
+
+export interface DeviceIdentityConflict {
+  readonly reason: IdentityReason;
+  readonly instanceIds: readonly string[];
+}
+
+export interface DeviceIdentityFieldChange {
+  readonly field: IdentityField;
+  readonly from: string;
+  readonly to: string;
+}
+
+export interface DeviceIdentity {
+  readonly instanceId: string;
+  readonly status: IdentityStatus;
+  readonly reasons: readonly IdentityReason[];
+  readonly conflicts: readonly DeviceIdentityConflict[];
+  readonly imei: string;
+  readonly manufacturer: string;
+  readonly model: string;
+  readonly revision: string;
+  readonly agent: string;
+  readonly origin: string;
+  readonly fingerprint: string;
+  readonly confirmedFingerprint: string;
+  readonly changes: readonly DeviceIdentityFieldChange[];
+  readonly observedAt: string;
+  readonly confirmedAt: string;
+}
+
+export type DeviceIdentityErrorCode = 'NOT_FOUND' | 'VALIDATION_FAILED';
+
+export class DeviceIdentityError extends Error {
+  constructor(
+    readonly code: DeviceIdentityErrorCode,
+    message: string,
+  ) {
+    super(message);
+    this.name = 'DeviceIdentityError';
+  }
+}
+
+export interface DeviceIdentityOptions {
+  readonly db: Database.Database;
+  readonly now?: () => Date;
+  /** Follows the connection setting: manual authorization makes a first report wait. */
+  readonly authorizationMode?: () => 'auto' | 'manual';
+}
+
+interface IdentityRow {
+  instance_id: string;
+  status: string;
+  reasons: string;
+  imei: string;
+  manufacturer: string;
+  model: string;
+  revision: string;
+  agent: string;
+  origin: string;
+  fingerprint: string;
+  confirmed_fingerprint: string;
+  confirmed_values_json: string;
+  confirmed_peers_json: string;
+  detail_json: string;
+  observed_at: string;
+  confirmed_at: string;
+}
+
+/** Device payloads are untrusted: only a trimmed, control-free, length-capped string is kept. */
+function text(value: unknown, limit: number): string {
+  if (typeof value !== 'string' && typeof value !== 'number') return '';
+  const raw = typeof value === 'number' ? String(value) : value;
+  return raw.replace(CONTROL_CHARACTERS, '').trim().slice(0, limit);
+}
+
+function identityValues(evidence: DeviceIdentityEvidence): IdentityValues {
+  const values: IdentityValues = {};
+  for (const field of IDENTITY_FIELDS) {
+    const value = text(evidence[field], MAX_FIELD_LENGTH[field]);
+    if (value) values[field] = value;
+  }
+  return values;
+}
+
+function digest(values: IdentityValues): string {
+  const canonical = IDENTITY_FIELDS.filter((field) => values[field] !== undefined)
+    .map((field) => `${field}=${values[field]}`)
+    .join('\n');
+  return createHash('sha256').update(canonical, 'utf8').digest('hex').slice(0, 16);
+}
+
+function stringArray(value: unknown): string[] {
+  return Array.isArray(value)
+    ? value.filter((item): item is string => typeof item === 'string')
+    : [];
+}
+
+function parseValues(value: string): IdentityValues {
+  try {
+    const parsed: unknown = JSON.parse(value);
+    if (parsed === null || typeof parsed !== 'object' || Array.isArray(parsed)) return {};
+    const record = parsed as Record<string, unknown>;
+    const values: IdentityValues = {};
+    for (const field of IDENTITY_FIELDS) {
+      const entry = text(record[field], MAX_FIELD_LENGTH[field]);
+      if (entry) values[field] = entry;
+    }
+    return values;
+  } catch {
+    return {};
+  }
+}
+
+/** The evidence the console shows: who else claims this identity and what changed. */
+interface IdentityDetail {
+  readonly peers: readonly string[];
+  readonly changes: readonly DeviceIdentityFieldChange[];
+}
+
+function parseDetail(value: string): IdentityDetail {
+  let parsed: unknown = {};
+  try {
+    parsed = JSON.parse(value);
+  } catch {
+    return { peers: [], changes: [] };
+  }
+  if (parsed === null || typeof parsed !== 'object' || Array.isArray(parsed))
+    return { peers: [], changes: [] };
+  const record = parsed as Record<string, unknown>;
+  const entries = Array.isArray(record.changes) ? record.changes : [];
+  const changes = entries.filter(
+    (entry): entry is DeviceIdentityFieldChange =>
+      entry !== null &&
+      typeof entry === 'object' &&
+      !Array.isArray(entry) &&
+      IDENTITY_FIELDS.includes((entry as Record<string, unknown>).field as IdentityField) &&
+      typeof (entry as Record<string, unknown>).from === 'string' &&
+      typeof (entry as Record<string, unknown>).to === 'string',
+  );
+  return { peers: stringArray(record.peers), changes };
+}
+
+function parseReasons(value: string): IdentityReason[] {
+  const allowed: IdentityReason[] = ['hardware_swapped', 'imei_claimed'];
+  try {
+    const parsed: unknown = JSON.parse(value);
+    if (!Array.isArray(parsed)) return [];
+    return parsed.filter((item): item is IdentityReason =>
+      allowed.includes(item as IdentityReason),
+    );
+  } catch {
+    return [];
+  }
+}
+
+/**
+ * Tracks the hardware behind each registered node and holds the control plane still when that
+ * hardware stops matching the record. Observations come from device reads the console is making
+ * anyway, so a node only gains an identity row once something has actually looked at it.
+ */
+export class DeviceIdentityService {
+  readonly #db: Database.Database;
+  readonly #clock: () => Date;
+  readonly #authorizationMode: () => 'auto' | 'manual';
+  readonly #select: Database.Statement;
+  readonly #selectPeers: Database.Statement;
+  readonly #insert: Database.Statement;
+  readonly #update: Database.Statement;
+
+  constructor(options: DeviceIdentityOptions) {
+    this.#db = options.db;
+    this.#clock = options.now ?? (() => new Date());
+    this.#authorizationMode = options.authorizationMode ?? (() => 'auto');
+    this.#select = options.db.prepare('SELECT * FROM device_identities WHERE instance_id=?');
+    this.#selectPeers = options.db.prepare(
+      "SELECT instance_id FROM device_identities WHERE imei=? AND instance_id<>? AND imei<>'' ORDER BY instance_id",
+    );
+    this.#insert = options.db.prepare(
+      `INSERT INTO device_identities (instance_id,status,reasons,imei,manufacturer,model,revision,
+        agent,origin,fingerprint,confirmed_fingerprint,confirmed_values_json,confirmed_peers_json,
+        detail_json,observed_at,confirmed_at,created_at,updated_at)
+       VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`,
+    );
+    this.#update = options.db.prepare(
+      `UPDATE device_identities SET status=?,reasons=?,imei=?,manufacturer=?,model=?,revision=?,
+        agent=?,origin=?,fingerprint=?,confirmed_fingerprint=?,confirmed_values_json=?,
+        confirmed_peers_json=?,detail_json=?,observed_at=?,confirmed_at=?,updated_at=?
+       WHERE instance_id=?`,
+    );
+  }
+
+  /**
+   * Records what a device just said about itself. Returns undefined when the payload carried no
+   * identity at all, which keeps a device that does not report its IMEI out of the guard rather
+   * than inventing a fingerprint from nothing.
+   */
+  observe(instanceId: string, evidence: DeviceIdentityEvidence): DeviceIdentity | undefined {
+    if (typeof instanceId !== 'string' || !instanceId) return undefined;
+    const values = identityValues(evidence);
+    const agent = text(evidence.agent, MAX_FIELD_LENGTH.agent);
+    const origin = text(evidence.origin, MAX_FIELD_LENGTH.origin);
+    if (Object.keys(values).length === 0) return undefined;
+    const now = this.#clock().toISOString();
+    const fingerprint = digest(values);
+    const manualFirstReport = this.#authorizationMode() === 'manual';
+    this.#db.transaction(() => {
+      const existing = this.#select.get(instanceId) as IdentityRow | undefined;
+      if (!existing) {
+        this.#insert.run(
+          instanceId,
+          manualFirstReport ? 'pending' : 'confirmed',
+          '[]',
+          values.imei ?? '',
+          values.manufacturer ?? '',
+          values.model ?? '',
+          values.revision ?? '',
+          agent,
+          origin,
+          fingerprint,
+          fingerprint,
+          JSON.stringify(values),
+          '[]',
+          '{"peers":[]}',
+          now,
+          now,
+          now,
+          now,
+        );
+        // A first report is a baseline, but it can still walk into a twin that is already
+        // registered, so the new row goes through the same evaluation as every other read.
+        const inserted = this.#select.get(instanceId) as IdentityRow;
+        this.#write(inserted, values, agent, origin, fingerprint, now, now, manualFirstReport);
+      } else {
+        this.#write(existing, values, agent, origin, fingerprint, now, now);
+      }
+      this.#syncClaims(instanceId, values.imei ?? '', now);
+    })();
+    return this.get(instanceId);
+  }
+
+  list(): readonly DeviceIdentity[] {
+    const rows = this.#db
+      .prepare('SELECT * FROM device_identities ORDER BY status DESC, instance_id')
+      .all() as IdentityRow[];
+    return rows.map((row) => this.#present(row));
+  }
+
+  get(instanceId: string): DeviceIdentity | undefined {
+    const row = this.#select.get(instanceId) as IdentityRow | undefined;
+    return row ? this.#present(row) : undefined;
+  }
+
+  /** Control operations only; reading a device is always allowed, unbinding is the way out. */
+  isBlocked(instanceId: string): boolean {
+    const row = this.#select.get(instanceId) as IdentityRow | undefined;
+    return row?.status === 'pending';
+  }
+
+  summarize(): { readonly tracked: number; readonly pending: readonly string[] } {
+    const rows = this.#db
+      .prepare('SELECT instance_id,status FROM device_identities ORDER BY instance_id')
+      .all() as Array<{ instance_id: string; status: string }>;
+    return {
+      tracked: rows.length,
+      pending: rows.filter((row) => row.status === 'pending').map((row) => row.instance_id),
+    };
+  }
+
+  /**
+   * The operator says "this is the device I mean". The current report becomes the baseline and
+   * the other claimants that were visible at that moment are accepted, so a known twin does not
+   * reopen the question on the next read while a third one still does.
+   */
+  confirm(instanceId: string): DeviceIdentity {
+    const row = this.#select.get(instanceId) as IdentityRow | undefined;
+    if (!row) throw new DeviceIdentityError('NOT_FOUND', 'Device identity was not found');
+    const now = this.#clock().toISOString();
+    const values = identityValues({
+      imei: row.imei,
+      manufacturer: row.manufacturer,
+      model: row.model,
+      revision: row.revision,
+    });
+    const fingerprint = row.fingerprint || digest(values);
+    this.#db.transaction(() => {
+      this.#update.run(
+        'confirmed',
+        '[]',
+        row.imei,
+        row.manufacturer,
+        row.model,
+        row.revision,
+        row.agent,
+        row.origin,
+        fingerprint,
+        fingerprint,
+        JSON.stringify(values),
+        JSON.stringify(this.#peers(instanceId, row.imei)),
+        '{"peers":[]}',
+        row.observed_at,
+        now,
+        now,
+        instanceId,
+      );
+      this.#syncClaims(instanceId, row.imei, now);
+    })();
+    const updated = this.#select.get(instanceId) as IdentityRow | undefined;
+    if (!updated) throw new DeviceIdentityError('NOT_FOUND', 'Device identity was not found');
+    return this.#present(updated);
+  }
+
+  #peers(instanceId: string, imei: string): string[] {
+    if (!imei) return [];
+    return (this.#selectPeers.all(imei, instanceId) as Array<{ instance_id: string }>).map(
+      (row) => row.instance_id,
+    );
+  }
+
+  /** Re-evaluated on every read, so a conflict that walks away stops holding the node. */
+  #write(
+    existing: IdentityRow,
+    values: IdentityValues,
+    agent: string,
+    origin: string,
+    fingerprint: string,
+    observedAt: string,
+    updatedAt: string,
+    forcePending = false,
+  ): void {
+    const confirmed = parseValues(existing.confirmed_values_json);
+    const accepted = parseStringArray(existing.confirmed_peers_json);
+    const changes: DeviceIdentityFieldChange[] = [];
+    for (const field of IDENTITY_FIELDS) {
+      const before = confirmed[field];
+      const after = values[field];
+      if (before !== undefined && after !== undefined && before !== after)
+        changes.push({ field, from: before, to: after });
+    }
+    const peers = this.#peers(existing.instance_id, values.imei ?? '');
+    const unaccepted = peers.filter((peer) => !accepted.includes(peer));
+    const reasons: IdentityReason[] = [];
+    if (changes.length > 0) reasons.push('hardware_swapped');
+    if (unaccepted.length > 0) reasons.push('imei_claimed');
+    this.#update.run(
+      reasons.length > 0 || forcePending ? 'pending' : 'confirmed',
+      JSON.stringify(reasons),
+      values.imei ?? existing.imei,
+      values.manufacturer ?? existing.manufacturer,
+      values.model ?? existing.model,
+      values.revision ?? existing.revision,
+      agent || existing.agent,
+      origin || existing.origin,
+      fingerprint,
+      existing.confirmed_fingerprint,
+      existing.confirmed_values_json,
+      existing.confirmed_peers_json,
+      JSON.stringify({ peers: unaccepted, changes }),
+      observedAt,
+      existing.confirmed_at,
+      updatedAt,
+      existing.instance_id,
+    );
+  }
+
+  /**
+   * A twin is told about itself: both records wait for the operator, not just the newcomer. Each
+   * peer is re-read from its own row, so a claim that walks away releases the peer it was holding
+   * and a peer that also drifted keeps its hardware_swapped reason.
+   */
+  #syncClaims(instanceId: string, imei: string, now: string): void {
+    if (!imei) return;
+    for (const { instance_id: peerId } of this.#selectPeers.all(imei, instanceId) as Array<{
+      instance_id: string;
+    }>) {
+      const peer = this.#select.get(peerId) as IdentityRow | undefined;
+      if (!peer) continue;
+      this.#write(
+        peer,
+        identityValues(peer),
+        peer.agent,
+        peer.origin,
+        peer.fingerprint || digest(identityValues(peer)),
+        peer.observed_at,
+        now,
+      );
+    }
+  }
+
+  #present(row: IdentityRow): DeviceIdentity {
+    const reasons = parseReasons(row.reasons);
+    const detail = parseDetail(row.detail_json);
+    const conflicts: DeviceIdentityConflict[] = [];
+    if (reasons.includes('hardware_swapped'))
+      conflicts.push({ reason: 'hardware_swapped', instanceIds: [] });
+    if (reasons.includes('imei_claimed'))
+      conflicts.push({ reason: 'imei_claimed', instanceIds: detail.peers });
+    return {
+      instanceId: row.instance_id,
+      status: row.status === 'pending' ? 'pending' : 'confirmed',
+      reasons,
+      conflicts,
+      imei: row.imei,
+      manufacturer: row.manufacturer,
+      model: row.model,
+      revision: row.revision,
+      agent: row.agent,
+      origin: row.origin,
+      fingerprint: row.fingerprint,
+      confirmedFingerprint: row.confirmed_fingerprint,
+      changes: detail.changes,
+      observedAt: row.observed_at,
+      confirmedAt: row.confirmed_at,
+    };
+  }
+}
+
+function parseStringArray(value: string): string[] {
+  try {
+    const parsed: unknown = JSON.parse(value);
+    return Array.isArray(parsed) ? stringArray(parsed) : [];
+  } catch {
+    return [];
+  }
+}
diff --git a/apps/api/src/application/instances/device-action-service.test.ts b/apps/api/src/application/instances/device-action-service.test.ts
index 54cc4e9..0b8bcf1 100644
--- a/apps/api/src/application/instances/device-action-service.test.ts
+++ b/apps/api/src/application/instances/device-action-service.test.ts
@@ -18,6 +18,7 @@ function fixture(
   replies: readonly Reply[] = [{ status: 200, body: { status: 'success' } }],
   extra: {
     readonly ensureSession?: (id: string, origin: string, force?: boolean) => Promise<void>;
+    readonly identities?: { isBlocked(instanceId: string): boolean };
   } = {},
 ) {
   const db = new Database(':memory:');
@@ -51,6 +52,7 @@ function fixture(
       };
     },
     ...(extra.ensureSession ? { ensureSession: extra.ensureSession } : {}),
+    ...(extra.identities ? { identities: extra.identities } : {}),
     now: () => new Date('2026-09-04T00:00:00.000Z'),
     id: () => 'audit-row-1',
   });
@@ -197,4 +199,23 @@ describe('DeviceActionService', () => {
     expect(JSON.stringify(summary)).not.toContain('office');
     expect(summary.every((item) => item.redacted === true)).toBe(true);
   });
+
+  it('holds every control while the device identity is disputed', async () => {
+    const { service, calls } = fixture(undefined, {
+      identities: { isBlocked: () => true },
+    });
+    await expect(
+      service.execute('node-a', 'cell-lock.unlock-all', {}, context),
+    ).rejects.toMatchObject({ code: 'IDENTITY_UNCONFIRMED' });
+    expect(calls).toHaveLength(0);
+  });
+
+  it('still lets an operator release the binding on a disputed device', async () => {
+    const { service, calls } = fixture(undefined, {
+      identities: { isBlocked: () => true },
+    });
+    const result = await service.execute('node-a', 'hub.unbind', {}, context);
+    expect(result.ok).toBe(true);
+    expect(calls).toHaveLength(1);
+  });
 });
diff --git a/apps/api/src/application/instances/device-action-service.ts b/apps/api/src/application/instances/device-action-service.ts
index 12d8fe2..2f20d84 100644
--- a/apps/api/src/application/instances/device-action-service.ts
+++ b/apps/api/src/application/instances/device-action-service.ts
@@ -20,7 +20,8 @@ export type DeviceActionErrorCode =
   | 'VALIDATION_FAILED'
   | 'SESSION_INVALID'
   | 'UPSTREAM_FAILED'
-  | 'NOT_DISPATCHED';
+  | 'NOT_DISPATCHED'
+  | 'IDENTITY_UNCONFIRMED';
 
 export class DeviceActionError extends Error {
   constructor(
@@ -192,6 +193,12 @@ export interface DeviceActionServiceOptions {
   readonly ensureSession?: (instanceId: string, origin: string, force?: boolean) => Promise<void>;
   readonly now?: () => Date;
   readonly id?: () => string;
+  /**
+   * The identity guard. A node whose reported hardware stopped matching its record, or whose
+   * identity is claimed by another record, is not safe to control: the command would land on a
+   * device the operator is not looking at. Unbinding stays available because it is the way out.
+   */
+  readonly identities?: { isBlocked(instanceId: string): boolean };
 }
 
 /**
@@ -239,6 +246,8 @@ export class DeviceActionService {
     const session = this.options.sessions.sessionFor(instanceId);
     if (session && session.origin !== instance.origin)
       throw new DeviceActionError('SESSION_INVALID');
+    if (action.id !== 'hub.unbind' && this.options.identities?.isBlocked(instanceId))
+      throw new DeviceActionError('IDENTITY_UNCONFIRMED');
 
     const values = this.#validate(action, params);
     const { path, query, body } = this.#assemble(action, values);
diff --git a/apps/api/src/application/observability/metrics-service.test.ts b/apps/api/src/application/observability/metrics-service.test.ts
new file mode 100644
index 0000000..9967b75
--- /dev/null
+++ b/apps/api/src/application/observability/metrics-service.test.ts
@@ -0,0 +1,138 @@
+import Database from 'better-sqlite3';
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { DeviceIdentityService } from '../identity/device-identity-service.js';
+import { migrateDatabase } from '../../infrastructure/database/migrations.js';
+import { MetricsService } from './metrics-service.js';
+
+let db: Database.Database | undefined;
+
+const NOW = '2026-09-05T02:00:00.000Z';
+
+function fixture() {
+  db = new Database(':memory:');
+  db.pragma('foreign_keys=ON');
+  migrateDatabase(db);
+  const identities = new DeviceIdentityService({ db });
+  const metrics = new MetricsService({
+    db,
+    version: '1.9.6',
+    sources: {
+      connections: {
+        summarize: () => [
+          {
+            instanceId: 'node-a',
+            total: 40,
+            success: 38,
+            failed: 2,
+            averageDurationMs: 12,
+            lastObservedAt: NOW,
+            lastErrorCode: null,
+            availabilityPercent: 95,
+          },
+        ],
+      },
+      identities,
+    },
+    now: () => new Date(NOW),
+  });
+  return { db, identities, metrics };
+}
+
+function seedNode(database: Database.Database, id: string, name: string, enabled = 1): void {
+  database
+    .prepare(
+      `INSERT INTO instances (id,name,base_url,auth_mode,enabled,config_revision,created_at,updated_at)
+       VALUES (?,?,'http://' || ? || ':8080','password',?,1,?,?)`,
+    )
+    .run(id, name, id, enabled, NOW, NOW);
+}
+
+afterEach(() => {
+  db?.close();
+  db = undefined;
+});
+
+describe('MetricsService', () => {
+  it('renders the fleet, queue and job gauges with every state present', () => {
+    const { db: database, metrics } = fixture();
+    seedNode(database, 'node-a', '机房 A');
+    seedNode(database, 'node-b', '机房 B', 0);
+    database
+      .prepare(
+        `INSERT INTO sms_outbox (id,instance_id,phone_number,content,status,available_at,created_at,updated_at)
+         VALUES ('s1','node-a','+8613800000000','hi','failed',?,?,?)`,
+      )
+      .run(NOW, NOW, NOW);
+    database
+      .prepare(
+        `INSERT INTO notification_queue (id,event_type,status,payload_json,available_at,created_at,updated_at)
+         VALUES ('q1','sms','pending','{}',?,?,?)`,
+      )
+      .run(NOW, NOW, NOW);
+    database
+      .prepare(
+        `INSERT INTO jobs (id,operation_id,risk_level,status,requested_by,request_id,parameters_digest,created_at,updated_at)
+         VALUES ('j1','node.reboot','R2','running','op','r1','digest',?,?)`,
+      )
+      .run(NOW, NOW);
+
+    const text = metrics.render();
+    expect(text).toContain('multi_simadmin_nodes_total 2');
+    expect(text).toContain('multi_simadmin_node_enabled{node="node-b"} 0');
+    expect(text).toContain('multi_simadmin_node_info{node="node-a",name="机房 A"} 1');
+    expect(text).toContain('multi_simadmin_node_probe_total{node="node-a",outcome="success"} 38');
+    expect(text).toContain('multi_simadmin_node_availability_ratio{node="node-a"} 0.950');
+    expect(text).toContain('multi_simadmin_sms_outbox{status="failed"} 1');
+    expect(text).toContain('multi_simadmin_sms_outbox{status="queued"} 0');
+    expect(text).toContain('multi_simadmin_notification_queue{status="pending"} 1');
+    expect(text).toContain('multi_simadmin_jobs{status="running"} 1');
+    expect(text).toContain('multi_simadmin_jobs{status="succeeded"} 0');
+    expect(text).toContain('multi_simadmin_scheduled_tasks{status="armed"} 0');
+    expect(text).toContain('multi_simadmin_build_info{version="1.9.6"} 1');
+    // A node with no probe history is counted rather than silently missing.
+    expect(text).toContain('multi_simadmin_node_unprobed 1');
+  });
+
+  it('reports the identity guard for each node it has seen', () => {
+    const { db: database, identities, metrics } = fixture();
+    seedNode(database, 'node-a', 'A');
+    seedNode(database, 'node-b', 'B');
+    const report = { imei: '860000000000009', model: 'RM500Q' };
+    identities.observe('node-a', report);
+    identities.observe('node-b', report);
+
+    const text = metrics.render();
+    expect(text).toContain('multi_simadmin_node_identity_pending{node="node-a"} 1');
+    expect(text).toContain('multi_simadmin_node_identity_pending{node="node-b"} 1');
+    expect(text).toContain('multi_simadmin_identity_pending_total 2');
+  });
+
+  it('escapes label values so a node name cannot forge a series', () => {
+    const { db: database, metrics } = fixture();
+    seedNode(database, 'node-a', 'evil" name\nwith break');
+
+    const text = metrics.render();
+    expect(text).toContain('name="evil\\" name\\nwith break"');
+    // The injected newline must not become its own sample line.
+    expect(text.split('\n').filter((line) => line.includes('with break'))).toHaveLength(1);
+  });
+
+  it('emits a valid exposition: help and type precede every series', () => {
+    const { db: database, metrics } = fixture();
+    seedNode(database, 'node-a', 'A');
+    const lines = metrics.render().trimEnd().split('\n');
+    const names = new Set<string>();
+    for (const line of lines) {
+      if (line.startsWith('# ')) {
+        const [, kind, name] = line.split(' ');
+        if (kind === 'TYPE') expect(names.has(name ?? ''), name).toBe(false);
+        continue;
+      }
+      const name = line.slice(0, line.search(/[{ ]/u));
+      expect(line, name).toMatch(/^[a-z_][a-z0-9_]*(\{[^{}]*\})? [-0-9.e+]+$/u);
+      names.add(name);
+    }
+    expect(names.size).toBeGreaterThan(10);
+  });
+});
diff --git a/apps/api/src/application/observability/metrics-service.ts b/apps/api/src/application/observability/metrics-service.ts
new file mode 100644
index 0000000..24442bf
--- /dev/null
+++ b/apps/api/src/application/observability/metrics-service.ts
@@ -0,0 +1,244 @@
+import type Database from 'better-sqlite3';
+
+import type { ConnectionSummary } from '../system/connection-log-service.js';
+import type { DeviceIdentity } from '../identity/device-identity-service.js';
+
+/**
+ * Prometheus exposition for the fused control plane.
+ *
+ * The scrape must never reach a device: every value here comes from rows the console already
+ * writes (instances, probes, queues, jobs, identity records). A monitoring system polling every
+ * 15 seconds should not be able to wake a modem.
+ */
+
+const PREFIX = 'multi_simadmin';
+
+export interface MetricsSource {
+  readonly connections: { summarize(): readonly ConnectionSummary[] };
+  readonly identities: { list(): readonly DeviceIdentity[] };
+}
+
+export interface MetricsOptions {
+  readonly db: Database.Database;
+  readonly version: string;
+  readonly sources: MetricsSource;
+  readonly now?: () => Date;
+}
+
+interface CountRow {
+  readonly status: string;
+  readonly count: number;
+}
+
+/** Label values are operator- or device-controlled, so they are escaped the Prometheus way. */
+function label(value: string): string {
+  return value.replace(/\\/gu, '\\\\').replace(/"/gu, '\\"').replace(/\n/gu, '\\n');
+}
+
+const number = (value: unknown): number => {
+  const parsed = typeof value === 'number' ? value : Number(value);
+  return Number.isFinite(parsed) ? parsed : 0;
+};
+
+function sample(name: string, help: string, type: 'gauge' | 'counter', lines: readonly string[]) {
+  return [`# HELP ${name} ${help}`, `# TYPE ${name} ${type}`, ...lines];
+}
+
+export class MetricsService {
+  readonly #db: Database.Database;
+  readonly #version: string;
+  readonly #sources: MetricsSource;
+  readonly #clock: () => Date;
+
+  constructor(options: MetricsOptions) {
+    this.#db = options.db;
+    this.#version = options.version;
+    this.#sources = options.sources;
+    this.#clock = options.now ?? (() => new Date());
+  }
+
+  render(): string {
+    const nodes = this.#db
+      .prepare('SELECT id,name,enabled FROM instances ORDER BY name, id')
+      .all() as Array<{
+      id: string;
+      name: string;
+      enabled: number;
+    }>;
+    const ids = new Set(nodes.map((node) => node.id));
+    const lines: string[] = [];
+
+    lines.push(
+      ...sample(`${PREFIX}_build_info`, 'Build identity of the control plane.', 'gauge', [
+        `${PREFIX}_build_info{version="${label(this.#version)}"} 1`,
+      ]),
+      ...sample(`${PREFIX}_scrape_timestamp_seconds`, 'Wall-clock time of this scrape.', 'gauge', [
+        `${PREFIX}_scrape_timestamp_seconds ${Math.floor(this.#clock().getTime() / 1000)}`,
+      ]),
+    );
+
+    const info = nodes.map(
+      (node) => `${PREFIX}_node_info{node="${label(node.id)}",name="${label(node.name)}"} 1`,
+    );
+    lines.push(
+      ...sample(`${PREFIX}_node_info`, 'Registered nodes and their addresses.', 'gauge', info),
+      ...sample(`${PREFIX}_nodes_total`, 'Number of registered nodes.', 'gauge', [
+        `${PREFIX}_nodes_total ${nodes.length}`,
+      ]),
+      ...sample(
+        `${PREFIX}_node_enabled`,
+        'Whether the node is enabled (1) or paused (0).',
+        'gauge',
+        nodes.map(
+          (node) => `${PREFIX}_node_enabled{node="${label(node.id)}"} ${node.enabled ? 1 : 0}`,
+        ),
+      ),
+    );
+
+    const probes = this.#sources.connections.summarize();
+    lines.push(
+      ...sample(
+        `${PREFIX}_node_probe_total`,
+        'Health probes recorded in the retained window, by outcome.',
+        'counter',
+        probes.flatMap((probe) => [
+          `${PREFIX}_node_probe_total{node="${label(probe.instanceId)}",outcome="success"} ${probe.success}`,
+          `${PREFIX}_node_probe_total{node="${label(probe.instanceId)}",outcome="failed"} ${probe.failed}`,
+        ]),
+      ),
+      ...sample(
+        `${PREFIX}_node_availability_ratio`,
+        'Share of successful probes in the retained window.',
+        'gauge',
+        probes.map(
+          (probe) =>
+            `${PREFIX}_node_availability_ratio{node="${label(probe.instanceId)}"} ${(probe.availabilityPercent / 100).toFixed(3)}`,
+        ),
+      ),
+      ...sample(
+        `${PREFIX}_node_probe_duration_ms`,
+        'Average probe latency in the retained window.',
+        'gauge',
+        probes.map(
+          (probe) =>
+            `${PREFIX}_node_probe_duration_ms{node="${label(probe.instanceId)}"} ${number(probe.averageDurationMs)}`,
+        ),
+      ),
+    );
+
+    const identities = this.#sources.identities.list();
+    const pending = identities.filter((identity) => identity.status === 'pending');
+    lines.push(
+      ...sample(
+        `${PREFIX}_node_identity_tracked`,
+        'Whether the node has ever reported its hardware identity.',
+        'gauge',
+        identities.map(
+          (identity) => `${PREFIX}_node_identity_tracked{node="${label(identity.instanceId)}"} 1`,
+        ),
+      ),
+      ...sample(
+        `${PREFIX}_node_identity_pending`,
+        '1 while the identity guard holds the node and control actions are refused.',
+        'gauge',
+        identities.map(
+          (identity) =>
+            `${PREFIX}_node_identity_pending{node="${label(identity.instanceId)}"} ${identity.status === 'pending' ? 1 : 0}`,
+        ),
+      ),
+      ...sample(
+        `${PREFIX}_identity_pending_total`,
+        'Nodes waiting for an operator to confirm the device behind them.',
+        'gauge',
+        [`${PREFIX}_identity_pending_total ${pending.length}`],
+      ),
+    );
+
+    lines.push(
+      ...this.#statusMetric(
+        `${PREFIX}_sms_outbox`,
+        'Queued cross-node SMS sends, by state.',
+        'SELECT status, COUNT(*) AS count FROM sms_outbox GROUP BY status',
+        ['queued', 'sending', 'sent', 'failed', 'cancelled'],
+      ),
+      ...this.#statusMetric(
+        `${PREFIX}_notification_queue`,
+        'Central notification queue, by state.',
+        'SELECT status, COUNT(*) AS count FROM notification_queue GROUP BY status',
+        ['pending', 'sending', 'succeeded', 'failed', 'cancelled'],
+      ),
+      ...this.#statusMetric(
+        `${PREFIX}_jobs`,
+        'Fleet operations, by state.',
+        'SELECT status, COUNT(*) AS count FROM jobs GROUP BY status',
+        [
+          'queued',
+          'running',
+          'cancelling',
+          'succeeded',
+          'partially-succeeded',
+          'failed',
+          'cancelled',
+          'unknown-result',
+        ],
+      ),
+      ...this.#statusMetric(
+        `${PREFIX}_scheduled_tasks`,
+        'Automation tasks, by state.',
+        `SELECT CASE WHEN enabled=1 THEN 'armed' ELSE 'paused' END AS status,
+                COUNT(*) AS count FROM scheduled_tasks GROUP BY enabled`,
+        ['armed', 'paused'],
+      ),
+    );
+
+    const groups = this.#count('SELECT COUNT(*) AS count FROM device_groups');
+    const tags = this.#count('SELECT COUNT(*) AS count FROM tag_registry');
+    const messages = this.#count('SELECT COUNT(*) AS count FROM sms_messages');
+    const probed = new Set(probes.map((probe) => probe.instanceId));
+    const unprobed = [...ids].filter((id) => !probed.has(id)).length;
+    lines.push(
+      ...sample(`${PREFIX}_device_groups`, 'Node groups.', 'gauge', [
+        `${PREFIX}_device_groups ${groups}`,
+      ]),
+      ...sample(`${PREFIX}_device_tags`, 'Labels in the tag registry.', 'gauge', [
+        `${PREFIX}_device_tags ${tags}`,
+      ]),
+      ...sample(
+        `${PREFIX}_sms_messages`,
+        'SMS rows synchronised into the central message centre.',
+        'gauge',
+        [`${PREFIX}_sms_messages ${messages}`],
+      ),
+      ...sample(
+        `${PREFIX}_node_unprobed`,
+        'Registered nodes without a health probe in the retained window.',
+        'gauge',
+        [`${PREFIX}_node_unprobed ${unprobed}`],
+      ),
+    );
+
+    return `${lines.join('\n')}\n`;
+  }
+
+  #count(sql: string): number {
+    const row = this.#db.prepare(sql).get() as { count?: number } | undefined;
+    return number(row?.count ?? 0);
+  }
+
+  /** Every state is emitted, including the empty ones, so a query never sees a series vanish. */
+  #statusMetric(
+    name: string,
+    help: string,
+    sql: string,
+    states: readonly string[],
+  ): readonly string[] {
+    const rows = this.#db.prepare(sql).all() as readonly CountRow[];
+    const counts = new Map(rows.map((row) => [String(row.status), number(row.count)]));
+    return sample(
+      name,
+      help,
+      'gauge',
+      states.map((state) => `${name}{status="${label(state)}"} ${counts.get(state) ?? 0}`),
+    );
+  }
+}
diff --git a/apps/api/src/infrastructure/database/database.test.ts b/apps/api/src/infrastructure/database/database.test.ts
index 8f9c085..0b6c2a9 100644
--- a/apps/api/src/infrastructure/database/database.test.ts
+++ b/apps/api/src/infrastructure/database/database.test.ts
@@ -66,6 +66,7 @@ describe('database migrations', () => {
       'console_auth_config',
       'console_auth_sessions',
       'device_groups',
+      'device_identities',
       'event_journal',
       'instance_tags',
       'instances',
diff --git a/apps/api/src/infrastructure/database/migrations.ts b/apps/api/src/infrastructure/database/migrations.ts
index b2ab1a5..5f27145 100644
--- a/apps/api/src/infrastructure/database/migrations.ts
+++ b/apps/api/src/infrastructure/database/migrations.ts
@@ -638,6 +638,38 @@ export const MIGRATIONS: readonly Migration[] = [
       "ALTER TABLE notification_channels ADD COLUMN secret_fields TEXT NOT NULL DEFAULT ''",
     ],
   },
+  {
+    id: 17,
+    name: 'device-identity-guard',
+    statements: [
+      // The Hub refuses to control a device whose identity drifted: the same IMEI claimed by
+      // two records, or hardware swapped behind an address that is still registered. Both are
+      // recorded here and only an operator can clear them, because the machine cannot tell
+      // which of two claimants is the real device.
+      `CREATE TABLE device_identities (
+          instance_id TEXT PRIMARY KEY REFERENCES instances(id) ON DELETE CASCADE,
+          status TEXT NOT NULL DEFAULT 'confirmed' CHECK (status IN ('confirmed','pending')),
+          reasons TEXT NOT NULL DEFAULT '[]',
+          imei TEXT NOT NULL DEFAULT '',
+          manufacturer TEXT NOT NULL DEFAULT '',
+          model TEXT NOT NULL DEFAULT '',
+          revision TEXT NOT NULL DEFAULT '',
+          agent TEXT NOT NULL DEFAULT '',
+          origin TEXT NOT NULL DEFAULT '',
+          fingerprint TEXT NOT NULL DEFAULT '',
+          confirmed_fingerprint TEXT NOT NULL DEFAULT '',
+          confirmed_values_json TEXT NOT NULL DEFAULT '{}',
+          confirmed_peers_json TEXT NOT NULL DEFAULT '[]',
+          detail_json TEXT NOT NULL DEFAULT '{}',
+          observed_at TEXT NOT NULL,
+          confirmed_at TEXT NOT NULL,
+          created_at TEXT NOT NULL,
+          updated_at TEXT NOT NULL
+        )`,
+      'CREATE INDEX idx_device_identities_status ON device_identities(status, instance_id)',
+      'CREATE INDEX idx_device_identities_imei ON device_identities(imei, instance_id)',
+    ],
+  },
 ];
 
 const createMigrationsTable = `CREATE TABLE schema_migrations (
diff --git a/apps/api/src/interface/http/device-action-routes.ts b/apps/api/src/interface/http/device-action-routes.ts
index a5ae5e4..e1a59be 100644
--- a/apps/api/src/interface/http/device-action-routes.ts
+++ b/apps/api/src/interface/http/device-action-routes.ts
@@ -7,6 +7,8 @@ import {
 
 export interface DeviceActionRoutesOptions {
   readonly actions: DeviceActionService;
+  /** The identity guard, so the console can grey controls out before the operator tries one. */
+  readonly identities?: { isBlocked(instanceId: string): boolean };
 }
 
 function problem(
@@ -21,7 +23,7 @@ function problem(
     .type('application/problem+json')
     .send({
       type: 'about:blank',
-      title: status === 404 ? 'Not Found' : 'Bad Request',
+      title: titleFor(status),
       status,
       code,
       detail,
@@ -35,6 +37,8 @@ const statusFor = (code: DeviceActionError['code']): number => {
       return 404;
     case 'SESSION_INVALID':
       return 401;
+    case 'IDENTITY_UNCONFIRMED':
+      return 409;
     case 'UPSTREAM_FAILED':
     case 'NOT_DISPATCHED':
       return 502;
@@ -43,6 +47,9 @@ const statusFor = (code: DeviceActionError['code']): number => {
   }
 };
 
+const titleFor = (status: number): string =>
+  status === 404 ? 'Not Found' : status === 409 ? 'Conflict' : 'Bad Request';
+
 export function registerDeviceActionRoutes(
   app: FastifyInstance,
   options: DeviceActionRoutesOptions,
@@ -51,7 +58,10 @@ export function registerDeviceActionRoutes(
     const instanceId = (request.params as { instanceId?: unknown }).instanceId;
     if (typeof instanceId !== 'string' || instanceId.length === 0)
       return problem(request, reply, 400, 'VALIDATION_FAILED', 'Instance id is required');
-    return { actions: options.actions.list() };
+    return {
+      actions: options.actions.list(),
+      identityBlocked: options.identities?.isBlocked(instanceId) === true,
+    };
   });
 
   app.post(
@@ -98,7 +108,9 @@ export function registerDeviceActionRoutes(
             reply,
             statusFor(error.code),
             error.code,
-            'The device action could not be completed.',
+            error.code === 'IDENTITY_UNCONFIRMED'
+              ? '设备身份待确认，请先核对 IMEI 与硬件信息后解除阻止。'
+              : 'The device action could not be completed.',
           );
         throw error;
       }
diff --git a/apps/api/src/interface/http/fleet-routes.ts b/apps/api/src/interface/http/fleet-routes.ts
index d3077ca..00f0e8e 100644
--- a/apps/api/src/interface/http/fleet-routes.ts
+++ b/apps/api/src/interface/http/fleet-routes.ts
@@ -20,6 +20,11 @@ import {
   NotificationServiceError,
   type InstanceNotificationService,
 } from '../../application/notifications/instance-notification-service.js';
+import type {
+  DeviceIdentity,
+  DeviceIdentityService,
+  IdentityReason,
+} from '../../application/identity/device-identity-service.js';
 export interface FleetMessageDevice {
   readonly id: string;
   readonly name: string;
@@ -68,6 +73,14 @@ export interface FleetRoutesOptions {
   readonly connections?: ConnectionProbe;
   /** Offline send queue; absent means sends fail fast instead of waiting for the device. */
   readonly outbox?: SmsOutboxService;
+  /** Identity guard; absent means the fleet list has no opinion about hardware drift. */
+  readonly identities?: DeviceIdentityService;
+}
+
+export interface FleetIdentitySummary {
+  readonly tracked: boolean;
+  readonly status: 'confirmed' | 'pending';
+  readonly reasons: readonly IdentityReason[];
 }
 
 /** One queued send, with the node label the queue table itself does not store. */
@@ -184,6 +197,11 @@ function connectionSummary(state: ConnectionState | undefined): FleetConnectionS
   };
 }
 
+function identitySummary(identity: DeviceIdentity | undefined): FleetIdentitySummary {
+  if (!identity) return { tracked: false, status: 'confirmed', reasons: [] };
+  return { tracked: true, status: identity.status, reasons: identity.reasons };
+}
+
 function record(value: unknown): Record<string, unknown> | undefined {
   if (!value || typeof value !== 'object' || Array.isArray(value)) return undefined;
   return value as Record<string, unknown>;
@@ -357,6 +375,7 @@ export function registerFleetRoutes(app: FastifyInstance, options: FleetRoutesOp
       ...instance,
       connection: connectionSummary(reachability?.get(instance.id)),
       resources: await options.resources.get(instance.id),
+      identity: identitySummary(options.identities?.get(instance.id)),
     }));
     return { items };
   });
diff --git a/apps/api/src/interface/http/identity-routes.test.ts b/apps/api/src/interface/http/identity-routes.test.ts
new file mode 100644
index 0000000..4a249bb
--- /dev/null
+++ b/apps/api/src/interface/http/identity-routes.test.ts
@@ -0,0 +1,173 @@
+import Database from 'better-sqlite3';
+import Fastify from 'fastify';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { DeviceIdentityService } from '../../application/identity/device-identity-service.js';
+import type { InstanceModuleService } from '../../application/instances/instance-module-service.js';
+import type { InstanceService } from '../../application/instances/instance-service.js';
+import { migrateDatabase } from '../../infrastructure/database/migrations.js';
+import { registerIdentityRoutes } from './identity-routes.js';
+
+let subject: { app: ReturnType<typeof Fastify>; db: Database.Database } | undefined;
+
+const nodes: Record<string, string> = {
+  'node-a': '机房 A',
+  'node-b': '机房 B',
+};
+
+function fixture(read?: (instanceId: string) => Promise<void>) {
+  const db = new Database(':memory:');
+  db.pragma('foreign_keys=ON');
+  migrateDatabase(db);
+  // Identity rows hang off instances, so the fixture nodes have to exist for real.
+  const seed = db.prepare(
+    `INSERT INTO instances (id,name,base_url,auth_mode,enabled,config_revision,created_at,updated_at)
+     VALUES (?,?,'http://' || ? || ':8080','password',1,1,'2026-09-05T02:00:00.000Z','2026-09-05T02:00:00.000Z')`,
+  );
+  for (const [id, name] of Object.entries(nodes)) seed.run(id, name, id);
+  const identities = new DeviceIdentityService({ db });
+  const app = Fastify();
+  registerIdentityRoutes(app, {
+    identities,
+    instances: {
+      list: async () => ({
+        items: Object.entries(nodes).map(([id, name]) => ({ id, name })),
+      }),
+    } as unknown as InstanceService,
+    ...(read
+      ? {
+          modules: {
+            read: async (instanceId: string) => {
+              await read(instanceId);
+            },
+          } as unknown as InstanceModuleService,
+        }
+      : {}),
+  });
+  subject = { app, db };
+  return { app, identities, db };
+}
+
+afterEach(async () => {
+  await subject?.app.close();
+  subject?.db.close();
+  subject = undefined;
+});
+
+const report = { imei: '860000000000001', model: 'RM500Q', manufacturer: 'Quectel' };
+
+describe('identity routes', () => {
+  it('serves the guard view with node labels for every claimant', async () => {
+    const { app, identities } = fixture();
+    identities.observe('node-a', report);
+    identities.observe('node-b', report);
+
+    const listed = await app.inject({ method: 'GET', url: '/api/v1/fleet/identities' });
+
+    expect(listed.statusCode).toBe(200);
+    const body = listed.json() as {
+      summary: { tracked: number; pending: number };
+      items: Array<Record<string, unknown>>;
+    };
+    expect(body.summary).toEqual({ tracked: 2, pending: 2 });
+    expect(body.items).toHaveLength(2);
+    expect(body.items[0]).toMatchObject({
+      instanceId: 'node-a',
+      instanceName: '机房 A',
+      status: 'pending',
+      reasons: ['imei_claimed'],
+      conflicts: [{ reason: 'imei_claimed', instanceIds: ['node-b'], instanceNames: ['机房 B'] }],
+      imei: '860000000000001',
+    });
+  });
+
+  it('puts held nodes first no matter which one reported last', async () => {
+    const { app, identities } = fixture();
+    // node-b registers first, so an insertion-order listing would lead with the wrong record.
+    identities.observe('node-b', report);
+    identities.observe('node-a', report);
+    await app.inject({ method: 'POST', url: '/api/v1/fleet/identities/node-b/confirm' });
+
+    const listed = await app.inject({ method: 'GET', url: '/api/v1/fleet/identities' });
+    const body = listed.json() as { items: Array<{ instanceId: string; status: string }> };
+
+    expect(body.items.map((item) => [item.instanceId, item.status])).toEqual([
+      ['node-a', 'pending'],
+      ['node-b', 'confirmed'],
+    ]);
+  });
+
+  it('clears the guard for the node the operator vouches for', async () => {
+    const { app, identities } = fixture();
+    identities.observe('node-a', report);
+    identities.observe('node-b', report);
+
+    const confirmed = await app.inject({
+      method: 'POST',
+      url: '/api/v1/fleet/identities/node-a/confirm',
+    });
+
+    expect(confirmed.statusCode).toBe(200);
+    expect(confirmed.json()).toMatchObject({
+      identity: { instanceId: 'node-a', status: 'confirmed', reasons: [] },
+    });
+    expect(identities.isBlocked('node-a')).toBe(false);
+    expect(identities.isBlocked('node-b')).toBe(true);
+  });
+
+  it('answers 404 when there is nothing to confirm', async () => {
+    const { app } = fixture();
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/v1/fleet/identities/ghost/confirm',
+    });
+    expect(response.statusCode).toBe(404);
+    expect(response.json()).toMatchObject({ code: 'NOT_FOUND', status: 404 });
+  });
+
+  it('refreshes by reading the device once', async () => {
+    const observed = vi.fn();
+    const { app, identities } = fixture(async (instanceId) => {
+      observed(instanceId);
+      identities.observe(instanceId, report);
+    });
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/v1/fleet/identities/node-a/refresh',
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(observed).toHaveBeenCalledTimes(1);
+    expect(observed).toHaveBeenCalledWith('node-a');
+    expect(response.json()).toMatchObject({
+      observed: true,
+      identity: { instanceId: 'node-a', status: 'confirmed', model: 'RM500Q' },
+    });
+  });
+
+  it('says so when a device answers without any identity at all', async () => {
+    const { app } = fixture(async () => {});
+
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/v1/fleet/identities/node-a/refresh',
+    });
+
+    expect(response.statusCode).toBe(200);
+    expect(response.json()).toEqual({ observed: false });
+  });
+
+  it('reports a device that could not be reached for a refresh', async () => {
+    const { app } = fixture(async () => {
+      throw new Error('ECONNREFUSED');
+    });
+
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/v1/fleet/identities/node-a/refresh',
+    });
+
+    expect(response.statusCode).toBe(502);
+    expect(response.json()).toMatchObject({ code: 'UPSTREAM_FAILED' });
+  });
+});
diff --git a/apps/api/src/interface/http/identity-routes.ts b/apps/api/src/interface/http/identity-routes.ts
new file mode 100644
index 0000000..ead20d6
--- /dev/null
+++ b/apps/api/src/interface/http/identity-routes.ts
@@ -0,0 +1,175 @@
+import type { FastifyInstance, FastifyReply, FastifyRequest } from 'fastify';
+
+import {
+  DeviceIdentityError,
+  type DeviceIdentity,
+  type DeviceIdentityService,
+} from '../../application/identity/device-identity-service.js';
+import type { InstanceService } from '../../application/instances/instance-service.js';
+import type { InstanceModuleService } from '../../application/instances/instance-module-service.js';
+
+export interface IdentityRoutesOptions {
+  readonly identities: DeviceIdentityService;
+  readonly instances: InstanceService;
+  /** Optional so a control plane without device reads can still show what it already knows. */
+  readonly modules?: InstanceModuleService;
+}
+
+interface IdentityView {
+  readonly instanceId: string;
+  readonly instanceName: string;
+  readonly status: DeviceIdentity['status'];
+  readonly reasons: DeviceIdentity['reasons'];
+  readonly conflicts: ReadonlyArray<{
+    readonly reason: string;
+    readonly instanceIds: readonly string[];
+    readonly instanceNames: readonly string[];
+  }>;
+  readonly imei: string;
+  readonly manufacturer: string;
+  readonly model: string;
+  readonly revision: string;
+  readonly agent: string;
+  readonly origin: string;
+  readonly fingerprint: string;
+  readonly confirmedFingerprint: string;
+  readonly changes: DeviceIdentity['changes'];
+  readonly observedAt: string;
+  readonly confirmedAt: string;
+}
+
+const PAGE_SIZE = 100;
+const MAX_PAGES = 100;
+
+/**
+ * Pending records lead, then the node label the operator actually reads. Instance ids are random
+ * uuids, so sorting by them alone would shuffle the panel between two opens.
+ */
+function compareViews(a: IdentityView, b: IdentityView): number {
+  if (a.status !== b.status) return a.status === 'pending' ? -1 : 1;
+  const byName = (a.instanceName || a.instanceId).localeCompare(
+    b.instanceName || b.instanceId,
+    'zh-Hans-CN',
+    { numeric: true },
+  );
+  return byName !== 0 ? byName : a.instanceId.localeCompare(b.instanceId);
+}
+
+async function namesById(instances: InstanceService): Promise<ReadonlyMap<string, string>> {
+  const names = new Map<string, string>();
+  for (let page = 1; page <= MAX_PAGES; page += 1) {
+    const current = await instances.list({ page, pageSize: PAGE_SIZE });
+    for (const instance of current.items) names.set(instance.id, instance.name);
+    if (current.items.length < PAGE_SIZE) break;
+  }
+  return names;
+}
+
+function view(
+  identity: DeviceIdentity,
+  names: ReadonlyMap<string, string>,
+  fallback: string,
+): IdentityView {
+  return {
+    instanceId: identity.instanceId,
+    instanceName: names.get(identity.instanceId) ?? fallback,
+    status: identity.status,
+    reasons: identity.reasons,
+    conflicts: identity.conflicts.map((conflict) => ({
+      reason: conflict.reason,
+      instanceIds: conflict.instanceIds,
+      instanceNames: conflict.instanceIds.map((id) => names.get(id) ?? id),
+    })),
+    imei: identity.imei,
+    manufacturer: identity.manufacturer,
+    model: identity.model,
+    revision: identity.revision,
+    agent: identity.agent,
+    origin: identity.origin,
+    fingerprint: identity.fingerprint,
+    confirmedFingerprint: identity.confirmedFingerprint,
+    changes: identity.changes,
+    observedAt: identity.observedAt,
+    confirmedAt: identity.confirmedAt,
+  };
+}
+
+function problem(
+  request: FastifyRequest,
+  reply: FastifyReply,
+  status: number,
+  code: string,
+  detail: string,
+): FastifyReply {
+  return reply
+    .code(status)
+    .type('application/problem+json')
+    .send({
+      type: 'about:blank',
+      title: status === 404 ? 'Not Found' : 'Bad Request',
+      status,
+      code,
+      detail,
+      requestId: request.id,
+    });
+}
+
+function instanceIdOf(request: FastifyRequest): string {
+  const params = request.params as { instanceId?: unknown };
+  return typeof params.instanceId === 'string' ? params.instanceId : '';
+}
+
+/**
+ * The identity guard's console surface: what each node claims to be, which claims disagree, and
+ * the one action that clears a disagreement once the operator has looked at the evidence.
+ */
+export function registerIdentityRoutes(app: FastifyInstance, options: IdentityRoutesOptions): void {
+  app.get('/api/v1/fleet/identities', async () => {
+    const names = await namesById(options.instances);
+    const items = options.identities
+      .list()
+      .map((identity) => view(identity, names, ''))
+      .sort(compareViews);
+    const summary = options.identities.summarize();
+    return {
+      items,
+      summary: { tracked: summary.tracked, pending: summary.pending.length },
+    };
+  });
+
+  app.post('/api/v1/fleet/identities/:instanceId/confirm', async (request, reply) => {
+    const instanceId = instanceIdOf(request);
+    if (!instanceId)
+      return problem(request, reply, 400, 'VALIDATION_FAILED', 'Instance id is required');
+    try {
+      const identity = options.identities.confirm(instanceId);
+      const names = await namesById(options.instances);
+      return { identity: view(identity, names, instanceId) };
+    } catch (error) {
+      if (error instanceof DeviceIdentityError)
+        return problem(request, reply, 404, error.code, '该节点还没有可确认的身份记录。');
+      throw error;
+    }
+  });
+
+  // A refresh is one overview read: the device answers with its own hardware report and the
+  // guard re-decides, which is also how a node first earns an identity row.
+  app.post('/api/v1/fleet/identities/:instanceId/refresh', async (request, reply) => {
+    const instanceId = instanceIdOf(request);
+    if (!instanceId)
+      return problem(request, reply, 400, 'VALIDATION_FAILED', 'Instance id is required');
+    if (!options.modules)
+      return problem(request, reply, 400, 'VALIDATION_FAILED', 'Device reads are not available');
+    try {
+      await options.modules.read(instanceId, 'overview');
+    } catch {
+      return problem(request, reply, 502, 'UPSTREAM_FAILED', '设备未能返回身份信息，请稍后重试。');
+    }
+    const identity = options.identities.get(instanceId);
+    const names = await namesById(options.instances);
+    return {
+      observed: identity !== undefined,
+      ...(identity ? { identity: view(identity, names, instanceId) } : {}),
+    };
+  });
+}
diff --git a/apps/api/src/interface/http/metrics-routes.test.ts b/apps/api/src/interface/http/metrics-routes.test.ts
new file mode 100644
index 0000000..07d793a
--- /dev/null
+++ b/apps/api/src/interface/http/metrics-routes.test.ts
@@ -0,0 +1,64 @@
+import Database from 'better-sqlite3';
+import Fastify from 'fastify';
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { ConsoleAuthService } from '../../application/auth/console-auth-service.js';
+import { DeviceIdentityService } from '../../application/identity/device-identity-service.js';
+import { MetricsService } from '../../application/observability/metrics-service.js';
+import { migrateDatabase } from '../../infrastructure/database/migrations.js';
+import { registerConsoleAuth } from './console-auth-routes.js';
+import { PROMETHEUS_CONTENT_TYPE, registerMetricsRoutes } from './metrics-routes.js';
+
+let subject: { app: ReturnType<typeof Fastify>; db: Database.Database } | undefined;
+
+function fixture() {
+  const db = new Database(':memory:');
+  db.pragma('foreign_keys=ON');
+  migrateDatabase(db);
+  db.prepare(
+    `INSERT INTO instances (id,name,base_url,auth_mode,enabled,config_revision,created_at,updated_at)
+     VALUES ('node-a','机房 A','http://10.0.0.9:8080','password',1,1,'2026-09-05T02:00:00.000Z','2026-09-05T02:00:00.000Z')`,
+  ).run();
+  const identities = new DeviceIdentityService({ db });
+  const metrics = new MetricsService({
+    db,
+    version: '0.1.0',
+    sources: { connections: { summarize: () => [] }, identities },
+  });
+  const app = Fastify();
+  // The real guard, so the test proves the exemption rather than asserting a predicate.
+  registerConsoleAuth(app, new ConsoleAuthService({ db }));
+  registerMetricsRoutes(app, { metrics });
+  subject = { app, db };
+  return { app, db, identities };
+}
+
+afterEach(async () => {
+  await subject?.app.close();
+  subject?.db.close();
+  subject = undefined;
+});
+
+describe('metrics routes', () => {
+  it('serves the exposition in the format Prometheus expects', async () => {
+    const { app } = fixture();
+    const response = await app.inject({ method: 'GET', url: '/api/v1/metrics' });
+
+    expect(response.statusCode).toBe(200);
+    expect(response.headers['content-type']).toContain(PROMETHEUS_CONTENT_TYPE);
+    expect(response.body).toContain('multi_simadmin_nodes_total 1');
+    expect(response.body.endsWith('\n')).toBe(true);
+  });
+
+  it('stays open to a scraper while the console itself demands a session', async () => {
+    const { app, db } = fixture();
+    const auth = new ConsoleAuthService({ db });
+    await auth.updateSettings({ enabled: true, newPassword: 'passw0rd-1' });
+
+    const guarded = await app.inject({ method: 'GET', url: '/api/v1/instances' });
+    expect(guarded.statusCode).toBe(401);
+
+    const scraped = await app.inject({ method: 'GET', url: '/api/v1/metrics' });
+    expect(scraped.statusCode).toBe(200);
+  });
+});
diff --git a/apps/api/src/interface/http/metrics-routes.ts b/apps/api/src/interface/http/metrics-routes.ts
new file mode 100644
index 0000000..b36bf84
--- /dev/null
+++ b/apps/api/src/interface/http/metrics-routes.ts
@@ -0,0 +1,21 @@
+import type { FastifyInstance } from 'fastify';
+
+import type { MetricsService } from '../../application/observability/metrics-service.js';
+
+/** The content type Prometheus expects; anything else makes the scrape fail silently. */
+export const PROMETHEUS_CONTENT_TYPE = 'text/plain; version=0.0.4; charset=utf-8';
+
+export interface MetricsRoutesOptions {
+  readonly metrics: MetricsService;
+}
+
+/**
+ * Monitoring surface, modelled on the Hub's `/metrics`: no browser session, no cookies, just
+ * text. It is deliberately read-only and built from rows the console already writes, so a
+ * scraper polling every few seconds cannot wake a device.
+ */
+export function registerMetricsRoutes(app: FastifyInstance, options: MetricsRoutesOptions): void {
+  app.get('/api/v1/metrics', async (_request, reply) => {
+    return reply.type(PROMETHEUS_CONTENT_TYPE).send(options.metrics.render());
+  });
+}