feat(relay): rendezvous-relay service — 7 packages + plans (contracts/transport/agent/control-plane/e2e/auth/web)

Multi-tenant reverse-tunnel service ("ngrok for Claude Code" with E2E): a
host-agent dials OUT to an operator-run relay; external devices reach the host
THROUGH the relay, routed by per-tenant subdomain, forwarding ciphertext only
(the relay never sees plaintext). Lets a customer reach their own self-hosted
web-terminal from anywhere with zero networking setup.

Packages — all tsc-strict + vitest green (656 tests), cross-package integration verified:
- relay-contracts: frozen shared contracts (mux frame codec, data model,
  capability token, E2E envelope, pairing) — the src/types.ts analog
- term-relay:   native WS mux + stateless data plane (subdomain routing, ciphertext forward)
- agent:        host-agent (pairing, per-host Ed25519 + mTLS dial-out, forwards to 127.0.0.1:3000)
- control-plane: accounts/hosts registry, pairing-code flow, routing table, provisioning
- relay-e2e:    browser<->agent E2E (X25519 ECDH through relay, AEAD, anti-replay, recoverable replay key)
- relay-auth:   Passkey/WebAuthn, capability tokens, per-host certs, deny-by-default tenant isolation
- relay-web:    browser login + Web Crypto E2E + client-side preview rendering

Security invariants INV1-15 enforced; cross-tenant isolation CI tripwire live
(.github/workflows/relay-tripwire.yml). Design + implementation-level plans in
docs/PLAN_RELAY_*.md and docs/EXPLORE_RELAY_SERVICE.md.

NOTE: generated autonomously per the reviewed plans. The security-critical
packages (relay-e2e, relay-auth) REQUIRE expert security audit before any real
deployment — passing tests prove self-consistency, not resistance to attackers.
Base app (src/, public/) unchanged; concurrent desktop work left uncommitted.

agent/src/service/install.ts

@@ -0,0 +1,78 @@
+/**
+ * Service install dispatcher — PLAN_RELAY_AGENT T17. Detects the platform, writes the unit, and
+ * loads it. REFUSES to install as root (EXPLORE §4d least privilege). All IO is injected so the
+ * logic is unit-testable without touching the real system.
+ */
+import type { AgentConfig } from '../config/agentConfig.js'
+import {
+  buildLaunchdPlist,
+  launchdLoadCommand,
+  launchdPlistPath,
+  launchdUnloadCommand,
+} from './launchd.js'
+import {
+  buildSystemdUnit,
+  systemdDisableCommand,
+  systemdEnableCommand,
+  systemdUnitPath,
+} from './systemd.js'
+
+export type ServicePlatform = 'launchd' | 'systemd'
+
+export class RootRefusedError extends Error {
+  constructor() {
+    super('refusing to install the agent service as root — run as the logged-in user (least privilege)')
+    this.name = 'RootRefusedError'
+  }
+}
+
+export interface InstallDeps {
+  writeFile(path: string, content: string): void
+  runCommand(cmd: string, args: readonly string[]): Promise<void>
+  getuid(): number
+  homedir(): string
+  username(): string
+  binPath(): string
+}
+
+/** Map a Node platform to its service manager, or null if unsupported. */
+export function detectPlatform(os: NodeJS.Platform): ServicePlatform | null {
+  if (os === 'darwin') return 'launchd'
+  if (os === 'linux') return 'systemd'
+  return null
+}
+
+/** Write + load the service unit for `platform`. Throws RootRefusedError if running as root. */
+export async function installService(
+  _cfg: AgentConfig,
+  platform: ServicePlatform,
+  deps: InstallDeps,
+): Promise<void> {
+  if (deps.getuid() === 0) throw new RootRefusedError()
+  const bin = deps.binPath()
+  if (platform === 'launchd') {
+    const path = launchdPlistPath(deps.homedir())
+    deps.writeFile(path, buildLaunchdPlist(bin))
+    const { cmd, args } = launchdLoadCommand(path)
+    await deps.runCommand(cmd, args)
+    return
+  }
+  const path = systemdUnitPath(deps.homedir())
+  deps.writeFile(path, buildSystemdUnit(bin, deps.username()))
+  const { cmd, args } = systemdEnableCommand()
+  await deps.runCommand(cmd, args)
+}
+
+/** Unload the service unit for `platform`. */
+export async function uninstallService(
+  platform: ServicePlatform,
+  deps: Pick<InstallDeps, 'runCommand' | 'homedir'>,
+): Promise<void> {
+  if (platform === 'launchd') {
+    const { cmd, args } = launchdUnloadCommand(launchdPlistPath(deps.homedir()))
+    await deps.runCommand(cmd, args)
+    return
+  }
+  const { cmd, args } = systemdDisableCommand()
+  await deps.runCommand(cmd, args)
+}

agent/src/service/launchd.ts

@@ -0,0 +1,44 @@
+/**
+ * macOS launchd plist writer — PLAN_RELAY_AGENT T17. The service runs as the LOGGED-IN USER, not
+ * root (EXPLORE §4d least privilege); no secrets in the plist (key/cert stay in the keystore).
+ */
+const LABEL = 'com.web-terminal.agent'
+
+export function launchdLabel(): string {
+  return LABEL
+}
+
+export function launchdPlistPath(homedir: string): string {
+  return `${homedir}/Library/LaunchAgents/${LABEL}.plist`
+}
+
+/** Build the plist. ExecStart = `<bin> run`; RunAtLoad + KeepAlive (restart on failure). */
+export function buildLaunchdPlist(binPath: string): string {
+  return [
+    '<?xml version="1.0" encoding="UTF-8"?>',
+    '<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">',
+    '<plist version="1.0">',
+    '<dict>',
+    '  <key>Label</key>',
+    `  <string>${LABEL}</string>`,
+    '  <key>ProgramArguments</key>',
+    '  <array>',
+    `    <string>${binPath}</string>`,
+    '    <string>run</string>',
+    '  </array>',
+    '  <key>RunAtLoad</key>',
+    '  <true/>',
+    '  <key>KeepAlive</key>',
+    '  <true/>',
+    '</dict>',
+    '</plist>',
+    '',
+  ].join('\n')
+}
+
+export function launchdLoadCommand(plistPath: string): { cmd: string; args: readonly string[] } {
+  return { cmd: 'launchctl', args: ['load', plistPath] }
+}
+export function launchdUnloadCommand(plistPath: string): { cmd: string; args: readonly string[] } {
+  return { cmd: 'launchctl', args: ['unload', plistPath] }
+}

agent/src/service/originConfig.ts

@@ -0,0 +1,57 @@
+/**
+ * The ONE base-app touch-point — PLAN_RELAY_AGENT T17 (INDEX §0, EXPLORE §3 "Zero code change").
+ * APPENDS `https://<subdomain>.term.<domain>` to the base app's ALLOWED_ORIGINS env (idempotent),
+ * as CONFIG — NO `src/` code edit. AUGMENTS, never weakens, the Origin/CSWSH check: existing
+ * origins are always preserved (EXPLORE §3 "do not weaken the check").
+ */
+import { existsSync, readFileSync, writeFileSync } from 'node:fs'
+
+export interface OriginFsDeps {
+  exists(path: string): boolean
+  read(path: string): string
+  write(path: string, content: string): void
+}
+
+const defaultFs: OriginFsDeps = {
+  exists: existsSync,
+  read: (p) => readFileSync(p, 'utf8'),
+  write: (p, c) => writeFileSync(p, c),
+}
+
+/** Compose the subdomain origin the base app must trust. */
+export function subdomainOrigin(subdomain: string, domain: string): string {
+  return `https://${subdomain}.term.${domain}`
+}
+
+const KEY = 'ALLOWED_ORIGINS'
+
+function upsertOriginLine(content: string, origin: string): string {
+  const lines = content.length === 0 ? [] : content.split('\n')
+  let found = false
+  const next = lines.map((line) => {
+    if (!line.startsWith(`${KEY}=`)) return line
+    found = true
+    const current = line.slice(KEY.length + 1)
+    const origins = current.split(',').map((s) => s.trim()).filter((s) => s.length > 0)
+    if (origins.includes(origin)) return line // idempotent — already trusted
+    return `${KEY}=${[...origins, origin].join(',')}`
+  })
+  if (!found) next.push(`${KEY}=${origin}`)
+  return next.join('\n')
+}
+
+/**
+ * Idempotently append the subdomain origin to ALLOWED_ORIGINS in `baseAppEnvPath`. Never removes an
+ * existing origin. Creates the file/line if absent.
+ */
+export function ensureAllowedOrigin(
+  baseAppEnvPath: string,
+  subdomain: string,
+  domain: string,
+  fs: OriginFsDeps = defaultFs,
+): void {
+  const origin = subdomainOrigin(subdomain, domain)
+  const existing = fs.exists(baseAppEnvPath) ? fs.read(baseAppEnvPath) : ''
+  const updated = upsertOriginLine(existing, origin)
+  fs.write(baseAppEnvPath, updated.endsWith('\n') ? updated : `${updated}\n`)
+}

agent/src/service/systemd.ts

@@ -0,0 +1,40 @@
+/**
+ * Linux systemd unit writer — PLAN_RELAY_AGENT T17. Runs as the LOGGED-IN USER (never root,
+ * EXPLORE §4d), restart-on-failure; no secrets in the unit (key/cert stay in the keystore).
+ */
+const UNIT_NAME = 'web-terminal-agent.service'
+
+export function systemdUnitName(): string {
+  return UNIT_NAME
+}
+
+export function systemdUnitPath(homedir: string): string {
+  return `${homedir}/.config/systemd/user/${UNIT_NAME}`
+}
+
+/** Build the unit. ExecStart = `<bin> run`; Restart=on-failure; User=<user> (never root). */
+export function buildSystemdUnit(binPath: string, user: string): string {
+  return [
+    '[Unit]',
+    'Description=web-terminal host agent (rendezvous relay)',
+    'After=network-online.target',
+    '',
+    '[Service]',
+    'Type=simple',
+    `ExecStart=${binPath} run`,
+    'Restart=on-failure',
+    'RestartSec=1',
+    `User=${user}`,
+    '',
+    '[Install]',
+    'WantedBy=default.target',
+    '',
+  ].join('\n')
+}
+
+export function systemdEnableCommand(): { cmd: string; args: readonly string[] } {
+  return { cmd: 'systemctl', args: ['--user', 'enable', '--now', UNIT_NAME] }
+}
+export function systemdDisableCommand(): { cmd: string; args: readonly string[] } {
+  return { cmd: 'systemctl', args: ['--user', 'disable', '--now', UNIT_NAME] }
+}