feat(printer): USB transport behind the ESC/POS render layer

The ESC/POS printer drivers were TCP-only — every path went through
sendRaw/probe to a raw socket on port 9100. Add a USB transport behind
the existing render layer without touching a single render*() function.

- printer-escpos.ts: sendRawUsb/probeUsb write the same ESC/POS bytes to a
  kernel usblp char device (/dev/usb/lp0) via a plain fs write — no
  libusb/CUPS/native dep (keeps MIT-only + minimal-deps appliance). A
  discriminated Transport + transportFromConfig/sendTo/probeTo dispatch the
  wire; anything not transport:"usb" is TCP, so existing host-only configs
  need no migration. Shared transportField/devicePathField config fields.
- cashino + rongta resolve a Transport once; both are reachability-only over
  USB, and the Rongta's HTTP status page degrades to the open-the-node probe
  over USB (no guessed paper/cover — the standing honesty rule). host/port
  made not-required so a USB printer needs neither.
- Tests: printer-escpos.test.ts (USB writes the exact rendered bytes; probe
  present/absent; transportFromConfig TCP back-compat) + printer-cashino.test.ts
  (USB-configured driver prints to the node, ready/offline).

USB itself is unverified on hardware (the on-site printers are networked);
the appliance-side usblp + udev provisioning is tracked as open-questions #14.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

packages/devices/src/drivers/printer-cashino.test.ts

@@ -0,0 +1,50 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { cashinoDriver } from "./printer-cashino.js";
+import { renderTicket } from "./printer-escpos.js";
+
+// End-to-end transport routing through the real driver: a USB-configured Cashino must
+// resolve to the char-device transport and write the SAME ESC/POS bytes the TCP path
+// would. (The TCP path is exercised by the routing/escpos suites and on hardware.)
+
+describe("cashinoDriver — USB transport", () => {
+  let dir: string;
+  let devicePath: string;
+
+  beforeEach(() => {
+    dir = mkdtempSync(join(tmpdir(), "cashino-usb-"));
+    devicePath = join(dir, "lp0");
+    // Stand in for an enumerated usblp node (the kernel creates it; we only open it).
+    writeFileSync(devicePath, "");
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("prints a ticket to the configured USB device path", async () => {
+    const printer = cashinoDriver.create({ transport: "usb", devicePath, timeoutMs: 1000 });
+    const data = { ticketId: "12345678901", issuedAt: "2026-06-21T10:00:00.000Z" };
+    await printer.printTicket(data);
+    const written = readFileSync(devicePath);
+    expect(written.equals(renderTicket(data))).toBe(true);
+  });
+
+  it("healthCheck reports ready when the node exists, offline when it doesn't", async () => {
+    const present = cashinoDriver.create({ transport: "usb", devicePath, timeoutMs: 1000 });
+    expect((await present.healthCheck()).status).toBe("ready");
+    // An absent device node (printer unplugged / not enumerated) → offline.
+    const absent = cashinoDriver.create({
+      transport: "usb",
+      devicePath: join(dir, "absent-lp0"),
+      timeoutMs: 1000,
+    });
+    expect((await absent.healthCheck()).status).toBe("offline");
+  });
+
+  it("advertises both transports", () => {
+    expect(cashinoDriver.transports).toContain("usb");
+    expect(cashinoDriver.transports).toContain("tcp-ip");
+  });
+});

packages/devices/src/drivers/printer-cashino.ts

@@ -10,20 +10,31 @@ import type {
 import type { ConfigField, DeviceConfig, PrinterDriver } from "../registry.js";
 import { hostField, portField, stubLog } from "./common.js";
 import {
-  probe,
+  devicePathField,
+  probeTo,
   renderReceipt,
   renderReport,
   renderSubscriptionCard,
   renderTicket,
   renderWindowChargeNotice,
-  sendRaw,
+  sendTo,
+  transportField,
+  transportFromConfig,
+  type Transport,
 } from "./printer-escpos.js";
 
-// Cashino 80mm network thermal printer driver. The Cashino is an ESC/POS clone:
-// it PRINTS identically to the Rongta (same byte stream — see ./printer-escpos.ts),
-// so tickets, reports and subscription cards render the same. What it does NOT
-// have is the Rongta board's decoded status web page (/prn_stat.htm). It cannot
-// report paper-out / cover-open / cutter faults in a form we trust.
+// Cashino 80mm thermal printer driver (network OR USB). The Cashino is an ESC/POS
+// clone: it PRINTS identically to the Rongta (same byte stream — see
+// ./printer-escpos.ts), so tickets, reports and subscription cards render the same,
+// over either transport. What it does NOT have is the Rongta board's decoded status
+// web page (/prn_stat.htm). It cannot report paper-out / cover-open / cutter faults
+// in a form we trust.
+//
+// TRANSPORT: a single `config.transport` ("tcp-ip" | "usb") picks the wire; the
+// driver resolves it ONCE into a Transport and every print/probe stays transport-
+// blind (see transportFromConfig/sendTo/probeTo). USB writes the same bytes to a
+// local usblp char device (/dev/usb/lp0); TCP writes to the raw print socket. This
+// clone is the natural USB candidate — reachability-only, no status page to lose.
 //
 // Therefore this driver deliberately does NOT implement MonitorableDevice
 // (no readStatus). The device monitor then falls back to the generic
@@ -40,13 +51,11 @@ import {
 
 class CashinoPrinter implements PrinterDevice {
   readonly driverId = "cashino";
-  readonly #host: string;
-  readonly #port: number;
+  readonly #transport: Transport;
   readonly #timeout: number;
 
   constructor(config: DeviceConfig) {
-    this.#host = String(config.host);
-    this.#port = config.port ? Number(config.port) : 9100;
+    this.#transport = transportFromConfig(config);
     this.#timeout = config.timeoutMs ? Number(config.timeoutMs) : 3000;
   }
 
@@ -59,15 +68,15 @@ class CashinoPrinter implements PrinterDevice {
   }
 
   /**
-   * Reachability only — a TCP connect probe of the raw print socket. The Cashino
-   * has no trustworthy status protocol, so this is the floor and the ceiling of
-   * what we report: reachable → ready, unreachable → offline. Deliberately NO
-   * readStatus(): the monitor uses this for the traffic-light, never a guessed
-   * paper/cover state.
+   * Reachability only — a connect probe (TCP) or char-device open probe (USB) of
+   * the print path. The Cashino has no trustworthy status protocol, so this is the
+   * floor and the ceiling of what we report: reachable → ready, unreachable →
+   * offline. Deliberately NO readStatus(): the monitor uses this for the
+   * traffic-light, never a guessed paper/cover state.
    */
   async healthCheck(): Promise<DeviceHealth> {
     try {
-      await probe(this.#host, this.#port, this.#timeout);
+      await probeTo(this.#transport, this.#timeout);
       return { status: "ready" };
     } catch (err) {
       return { status: "offline", detail: (err as Error).message };
@@ -75,12 +84,12 @@ class CashinoPrinter implements PrinterDevice {
   }
 
   async printTicket(data: TicketData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderTicket(data), this.#timeout);
+    await sendTo(this.#transport, renderTicket(data), this.#timeout);
     stubLog(this.driverId, `printed ticket ${data.ticketId}`);
   }
 
   async printReport(report: PrintReport): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderReport(report), this.#timeout);
+    await sendTo(this.#transport, renderReport(report), this.#timeout);
     stubLog(
       this.driverId,
       `printed report "${report.title}" (${report.lines.length} lines)`,
@@ -88,17 +97,12 @@ class CashinoPrinter implements PrinterDevice {
   }
 
   async printSubscriptionCard(data: SubscriptionCardData): Promise<void> {
-    await sendRaw(
-      this.#host,
-      this.#port,
-      renderSubscriptionCard(data),
-      this.#timeout,
-    );
+    await sendTo(this.#transport, renderSubscriptionCard(data), this.#timeout);
     stubLog(this.driverId, `printed subscription card ${data.code}`);
   }
 
   async printReceipt(data: ReceiptData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderReceipt(data), this.#timeout);
+    await sendTo(this.#transport, renderReceipt(data), this.#timeout);
     stubLog(
       this.driverId,
       `printed ${data.voucher ? "voucher" : "receipt"} ${data.ticketId}`,
@@ -106,7 +110,7 @@ class CashinoPrinter implements PrinterDevice {
   }
 
   async printWindowChargeNotice(data: WindowChargeNoticeData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderWindowChargeNotice(data), this.#timeout);
+    await sendTo(this.#transport, renderWindowChargeNotice(data), this.#timeout);
     stubLog(this.driverId, `printed out-of-window slip ${data.occurrenceId}`);
   }
 }
@@ -141,14 +145,17 @@ export const cashinoDriver: PrinterDriver = {
   category: "printer",
   label: "Cashino 80mm thermal printer",
   description:
-    "Cashino 80mm thermal printer (ESC/POS over raw TCP, port 9100). Prints like the Rongta but has no status page — monitored by reachability ping only (no paper/cover/cutter reporting). No auth on the print socket — isolate the VLAN.",
-  transports: ["tcp-ip"],
+    "Cashino 80mm thermal printer (ESC/POS over raw TCP port 9100, OR local USB /dev/usb/lp0). Prints like the Rongta but has no status page — monitored by reachability only (no paper/cover/cutter reporting). No auth on the print socket — isolate the VLAN.",
+  transports: ["tcp-ip", "usb"],
   configFields: [
-    hostField,
+    transportField,
+    devicePathField,
+    // host/port are TCP-only; not required because a USB printer needs neither.
+    { ...hostField, required: false, help: `${hostField.help} Leave blank for a USB printer.` },
     {
       ...portField(9100),
       required: false,
-      help: "Raw print socket (ESC/POS over JetDirect/RAW, default 9100).",
+      help: "Raw print socket (ESC/POS over JetDirect/RAW, default 9100). TCP only.",
     },
     roleField,
     rankField,

packages/devices/src/drivers/printer-escpos.test.ts

@@ -1,9 +1,15 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import {
   renderTicket,
   renderReceipt,
   renderWindowChargeNotice,
   renderSubscriptionCard,
+  probeUsb,
+  sendRawUsb,
+  transportFromConfig,
   stamp,
 } from "./printer-escpos.js";
 
@@ -103,6 +109,69 @@ describe("CP852 character mapping (the misprint fixes)", () => {
   });
 });
 
+describe("USB transport (sendRawUsb / probeUsb / transportFromConfig)", () => {
+  // A regular file stands in for the usblp character device: open(O_WRONLY) + write
+  // is the same syscall path. This proves the transport is byte-blind — the EXACT
+  // ESC/POS stream renderTicket produces lands at the device path, with no transport
+  // touching a rendered byte (the whole point of the seam).
+  let dir: string;
+  let devicePath: string;
+
+  beforeEach(() => {
+    dir = mkdtempSync(join(tmpdir(), "escpos-usb-"));
+    devicePath = join(dir, "lp0");
+    // A real usblp node already EXISTS (created by the kernel on enumeration); we open
+    // it O_WRONLY without O_CREAT, never create it. Pre-create the stand-in file so the
+    // test mirrors that — opening an ABSENT path means "printer not present" (offline).
+    writeFileSync(devicePath, "");
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("writes the exact rendered ESC/POS bytes to the device path", async () => {
+    const payload = renderTicket({ ticketId: "12345678901", issuedAt: "2026-06-21T10:00:00.000Z" });
+    await sendRawUsb(devicePath, payload, 1000);
+    const written = readFileSync(devicePath);
+    expect(written.equals(payload)).toBe(true);
+  });
+
+  it("rejects when the device path can't be opened (printer not present)", async () => {
+    await expect(
+      sendRawUsb(join(dir, "absent-lp0"), Buffer.from([0x1b, 0x40]), 1000),
+    ).rejects.toThrow();
+  });
+
+  it("probeUsb resolves for an existing node, rejects for a missing one", async () => {
+    await expect(probeUsb(devicePath, 1000)).resolves.toBeUndefined();
+    await expect(probeUsb(join(dir, "nope"), 1000)).rejects.toThrow();
+  });
+
+  it("transportFromConfig: transport=usb selects the char device (default /dev/usb/lp0)", () => {
+    expect(transportFromConfig({ transport: "usb", devicePath: "/dev/usb/lp1" })).toEqual({
+      kind: "usb",
+      devicePath: "/dev/usb/lp1",
+    });
+    expect(transportFromConfig({ transport: "usb" })).toEqual({
+      kind: "usb",
+      devicePath: "/dev/usb/lp0",
+    });
+  });
+
+  it("transportFromConfig: anything else is TCP (back-compat with host-only configs)", () => {
+    expect(transportFromConfig({ host: "10.0.0.9" })).toEqual({
+      kind: "tcp",
+      host: "10.0.0.9",
+      port: 9100,
+    });
+    expect(transportFromConfig({ host: "10.0.0.9", port: 9101 })).toEqual({
+      kind: "tcp",
+      host: "10.0.0.9",
+      port: 9101,
+    });
+  });
+});
+
 describe("stamp (Albanian date format)", () => {
   it("formats an ISO time as '<day> <Month> <year> HH:MM:SS'", () => {
     // Local-time dependent, so assert the structure + the Albanian month name.

packages/devices/src/drivers/printer-escpos.ts

@@ -1,4 +1,6 @@
 import { Socket } from "node:net";
+import { open } from "node:fs/promises";
+import { constants as FS } from "node:fs";
 import type {
   PrintReport,
   ReceiptData,
@@ -567,7 +569,150 @@ export function probe(
   });
 }
 
+// --- USB transport (kernel usblp character device) ----------------------------
+// An ESC/POS USB printer plugged into the appliance enumerates as a character
+// device (e.g. /dev/usb/lp0) via the in-box `usblp` kernel driver. We deliver the
+// SAME ESC/POS byte stream there as over TCP — only the transport differs, not a
+// single rendered byte. No libusb / CUPS / native addon: a plain file write keeps
+// the MIT-only + offline-first, minimal-deps appliance constraints, and the path is
+// a LOCAL char device the booth operator (the threat model's adversary) can't reach
+// over the network. Paper/cover is NOT sensed here — same honesty floor as the
+// Cashino TCP probe. usblp + a udev rule granting the server write access to the
+// node are a provisioning dependency. See wiki/concepts/printer-usb-transport.md.
+
+/** Bound a promise with a timeout — a wedged USB printer can block a write (or even
+ *  the open) indefinitely, and a stuck print must surface as a failure rather than
+ *  hang the entry flow. The underlying handle leaks on timeout, but the process is
+ *  the appliance server; a failed print is logged and retried/failed-over upstream. */
+function withTimeout<T>(p: Promise<T>, ms: number, msg: string): Promise<T> {
+  return new Promise((resolve, reject) => {
+    const t = setTimeout(() => reject(new Error(msg)), ms);
+    p.then(
+      (v) => {
+        clearTimeout(t);
+        resolve(v);
+      },
+      (e) => {
+        clearTimeout(t);
+        reject(e as Error);
+      },
+    );
+  });
+}
+
+/** Write an ESC/POS payload to a USB-lp character device (e.g. /dev/usb/lp0). usblp
+ *  is a RAW character device: a single open + write delivers the job — there is no
+ *  FIN/half-close dance (that was a TCP concern, where an early destroy() could
+ *  truncate the stream). We always close the handle (even on a failed write). */
+export async function sendRawUsb(
+  devicePath: string,
+  payload: Buffer,
+  timeoutMs: number,
+): Promise<void> {
+  const handle = await withTimeout(
+    open(devicePath, FS.O_WRONLY | FS.O_NONBLOCK),
+    timeoutMs,
+    "usb open timeout",
+  );
+  try {
+    await withTimeout(handle.write(payload), timeoutMs, "usb write timeout");
+  } finally {
+    await handle.close();
+  }
+}
+
+/** Reachability for a USB printer: the floor is "does the char device exist and
+ *  open writable". A present, openable /dev/usb/lp0 means usblp bound a powered,
+ *  enumerated printer — the USB analogue of the TCP connect probe. (Like the Cashino
+ *  TCP probe, this reports reachability only, never a guessed paper/cover state.) */
+export async function probeUsb(devicePath: string, timeoutMs: number): Promise<void> {
+  const handle = await withTimeout(
+    open(devicePath, FS.O_WRONLY | FS.O_NONBLOCK),
+    timeoutMs,
+    "usb open timeout",
+  );
+  await handle.close();
+}
+
+// --- transport dispatch -------------------------------------------------------
+// A discriminated transport so each driver resolves the wire ONCE (from config) and
+// every print/probe call site stays transport-blind. Adding a transport = one more
+// arm here + the render layer is untouched.
+
+/** Where a printer's bytes go: a TCP raw-print socket, or a local USB char device. */
+export type Transport =
+  | { kind: "tcp"; host: string; port: number }
+  | { kind: "usb"; devicePath: string };
+
+/** Build a Transport from a driver's flat config. `transport: "usb"` selects the
+ *  USB char device (`devicePath`, default /dev/usb/lp0); anything else is TCP
+ *  (host + port, default 9100) — so existing network configs with no `transport`
+ *  key keep working unchanged. */
+export function transportFromConfig(config: {
+  transport?: unknown;
+  host?: unknown;
+  port?: unknown;
+  devicePath?: unknown;
+}): Transport {
+  if (config.transport === "usb") {
+    return { kind: "usb", devicePath: String(config.devicePath ?? "/dev/usb/lp0") };
+  }
+  return {
+    kind: "tcp",
+    host: String(config.host),
+    port: config.port ? Number(config.port) : 9100,
+  };
+}
+
+/** Send an ESC/POS payload over whichever transport the printer is configured for. */
+export function sendTo(t: Transport, payload: Buffer, timeoutMs: number): Promise<void> {
+  return t.kind === "usb"
+    ? sendRawUsb(t.devicePath, payload, timeoutMs)
+    : sendRaw(t.host, t.port, payload, timeoutMs);
+}
+
+/** Reachability probe over whichever transport the printer is configured for. */
+export function probeTo(t: Transport, timeoutMs: number): Promise<void> {
+  return t.kind === "usb"
+    ? probeUsb(t.devicePath, timeoutMs)
+    : probe(t.host, t.port, timeoutMs);
+}
+
+/** Human label for a transport, for status detail / logs. */
+export function transportLabel(t: Transport): string {
+  return t.kind === "usb" ? t.devicePath : `${t.host}:${t.port}`;
+}
+
 // --- shared driver config fields ----------------------------------------------
 // Role + failover are identical across ESC/POS printers; defined here so each
 // driver shares them. See wiki/concepts/printer-roles-failover.md.
 export type PrinterRole = "entry-dispenser" | "booth-receipt";
+
+// --- shared printer config fields (transport) ---------------------------------
+// TCP-or-USB is offered identically across the ESC/POS drivers; defined here so each
+// shares the exact field set. The setup wizard renders these generically.
+import type { ConfigField } from "../registry.js";
+
+/** Connection-transport select: network (raw TCP 9100) or local USB char device. */
+export const transportField: ConfigField = {
+  key: "transport",
+  label: "Connection",
+  type: "select",
+  required: true,
+  default: "tcp-ip",
+  options: [
+    { value: "tcp-ip", label: "Network (raw TCP, port 9100)" },
+    { value: "usb", label: "USB (local /dev/usb/lp0)" },
+  ],
+  help: "USB drives a printer plugged into the appliance (usblp); Network drives one on the isolated device VLAN.",
+};
+
+/** USB character-device path; used only when transport=usb (ignored for TCP). */
+export const devicePathField: ConfigField = {
+  key: "devicePath",
+  label: "USB device",
+  type: "string",
+  required: false,
+  default: "/dev/usb/lp0",
+  help: "Character device for a USB printer (usblp), e.g. /dev/usb/lp0. Only used when Connection is USB.",
+};

packages/devices/src/drivers/printer-rongta.ts

@@ -13,22 +13,28 @@ import type {
 import type { ConfigField, DeviceConfig, PrinterDriver } from "../registry.js";
 import { hostField, portField, stubLog } from "./common.js";
 import {
-  probe,
+  devicePathField,
+  probeTo,
   renderReceipt,
   renderReport,
   renderSubscriptionCard,
   renderTicket,
   renderWindowChargeNotice,
-  sendRaw,
+  sendTo,
+  transportField,
+  transportFromConfig,
+  type Transport,
 } from "./printer-escpos.js";
 
-// Rongta 80mm network thermal printer driver. Rongta RP-series printers (and the
-// many OEM clones that share their firmware) speak ESC/POS over a raw TCP socket
-// on port 9100 — the JetDirect/RAW convention. The ESC/POS rendering + transport
-// are shared with the other ESC/POS clones in ./printer-escpos.ts; what is unique
-// to Rongta — and lives here — is LIVE STATUS via the board's own status web page.
-// There is no auth on the print socket; like the other field devices it lives on
-// the isolated device VLAN.
+// Rongta 80mm thermal printer driver (network OR USB). Rongta RP-series printers
+// (and the many OEM clones that share their firmware) speak ESC/POS over a raw TCP
+// socket on port 9100 — the JetDirect/RAW convention — or over a local USB usblp
+// char device. The ESC/POS rendering + transport are shared with the other ESC/POS
+// clones in ./printer-escpos.ts (config.transport picks the wire); what is unique to
+// Rongta — and lives here — is LIVE STATUS via the board's own status web page. That
+// page is a NETWORK feature: a USB Rongta degrades to reachability-only monitoring
+// (see readStatus). There is no auth on the print socket; like the other field
+// devices a networked unit lives on the isolated device VLAN.
 // See wiki/entities/rongta-printer.md and wiki/concepts/network-isolation.md.
 //
 // ROLES + FAILOVER: a lane has more than one printer. Each instance declares a
@@ -128,14 +134,15 @@ function parseStatusPage(html: string): StatusFlags {
 
 class RongtaPrinter implements PrinterDevice, MonitorableDevice {
   readonly driverId = "rongta";
+  readonly #transport: Transport;
   readonly #host: string;
-  readonly #port: number;
   readonly #httpPort: number;
   readonly #timeout: number;
 
   constructor(config: DeviceConfig) {
-    this.#host = String(config.host);
-    this.#port = config.port ? Number(config.port) : 9100;
+    this.#transport = transportFromConfig(config);
+    // Kept for the HTTP status page (TCP only); empty on a USB printer.
+    this.#host = config.host ? String(config.host) : "";
     this.#httpPort = config.httpPort ? Number(config.httpPort) : 80;
     this.#timeout = config.timeoutMs ? Number(config.timeoutMs) : 3000;
   }
@@ -150,7 +157,7 @@ class RongtaPrinter implements PrinterDevice, MonitorableDevice {
 
   async healthCheck(): Promise<DeviceHealth> {
     try {
-      await probe(this.#host, this.#port, this.#timeout);
+      await probeTo(this.#transport, this.#timeout);
       return { status: "ready" };
     } catch (err) {
       return { status: "offline", detail: (err as Error).message };
@@ -158,12 +165,12 @@ class RongtaPrinter implements PrinterDevice, MonitorableDevice {
   }
 
   async printTicket(data: TicketData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderTicket(data), this.#timeout);
+    await sendTo(this.#transport, renderTicket(data), this.#timeout);
     stubLog(this.driverId, `printed ticket ${data.ticketId}`);
   }
 
   async printReport(report: PrintReport): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderReport(report), this.#timeout);
+    await sendTo(this.#transport, renderReport(report), this.#timeout);
     stubLog(
       this.driverId,
       `printed report "${report.title}" (${report.lines.length} lines)`,
@@ -171,17 +178,12 @@ class RongtaPrinter implements PrinterDevice, MonitorableDevice {
   }
 
   async printSubscriptionCard(data: SubscriptionCardData): Promise<void> {
-    await sendRaw(
-      this.#host,
-      this.#port,
-      renderSubscriptionCard(data),
-      this.#timeout,
-    );
+    await sendTo(this.#transport, renderSubscriptionCard(data), this.#timeout);
     stubLog(this.driverId, `printed subscription card ${data.code}`);
   }
 
   async printReceipt(data: import("../interfaces.js").ReceiptData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderReceipt(data), this.#timeout);
+    await sendTo(this.#transport, renderReceipt(data), this.#timeout);
     stubLog(
       this.driverId,
       `printed ${data.voucher ? "voucher" : "receipt"} ${data.ticketId}`,
@@ -189,7 +191,7 @@ class RongtaPrinter implements PrinterDevice, MonitorableDevice {
   }
 
   async printWindowChargeNotice(data: WindowChargeNoticeData): Promise<void> {
-    await sendRaw(this.#host, this.#port, renderWindowChargeNotice(data), this.#timeout);
+    await sendTo(this.#transport, renderWindowChargeNotice(data), this.#timeout);
     stubLog(this.driverId, `printed out-of-window slip ${data.occurrenceId}`);
   }
 
@@ -206,6 +208,18 @@ class RongtaPrinter implements PrinterDevice, MonitorableDevice {
    */
   async readStatus(): Promise<PrinterStatus> {
     const checkedAt = new Date().toISOString();
+    // The status page is an HTTP feature of the network board; a USB printer has no
+    // such page. Degrade to the reachability floor (open the char device) and report
+    // ready/offline only — never a guessed paper/cover state, same honesty rule as
+    // the Cashino. (A USB Rongta is effectively a Cashino for monitoring purposes.)
+    if (this.#transport.kind === "usb") {
+      try {
+        await probeTo(this.#transport, this.#timeout);
+        return { status: "ready", checkedAt };
+      } catch (err) {
+        return { status: "offline", detail: (err as Error).message, checkedAt };
+      }
+    }
     let html: string;
     try {
       html = await fetchStatusPage(this.#host, this.#httpPort, this.#timeout);
@@ -281,14 +295,17 @@ export const rongtaDriver: PrinterDriver = {
   category: "printer",
   label: "Rongta 80mm thermal printer",
   description:
-    "Rongta RP-series 80mm thermal printer (and ESC/POS-compatible clones that serve the /prn_stat.htm status page) over raw TCP (port 9100). No auth on the print socket — isolate the VLAN.",
-  transports: ["tcp-ip"],
+    "Rongta RP-series 80mm thermal printer (and ESC/POS-compatible clones that serve the /prn_stat.htm status page) over raw TCP (port 9100), OR local USB /dev/usb/lp0. The decoded status page is a network feature — a USB Rongta is monitored by reachability only. No auth on the print socket — isolate the VLAN.",
+  transports: ["tcp-ip", "usb"],
   configFields: [
-    hostField,
+    transportField,
+    devicePathField,
+    // host/port/status-page are TCP-only; not required for a USB printer.
+    { ...hostField, required: false, help: `${hostField.help} Leave blank for a USB printer.` },
     {
       ...portField(9100),
       required: false,
-      help: "Raw print socket (ESC/POS over JetDirect/RAW, default 9100).",
+      help: "Raw print socket (ESC/POS over JetDirect/RAW, default 9100). TCP only.",
     },
     {
       key: "httpPort",
@@ -296,7 +313,7 @@ export const rongtaDriver: PrinterDriver = {
       type: "port",
       required: false,
       default: 80,
-      help: "Device status page (/prn_stat.htm) port for live monitoring (default 80).",
+      help: "Device status page (/prn_stat.htm) port for live monitoring (default 80). TCP only.",
     },
     roleField,
     rankField,