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.

relay-e2e/test/session.test.ts

@@ -0,0 +1,97 @@
+import { describe, expect, it } from 'vitest'
+import type { AeadAlg, DirectionalKeys, HandshakeResult } from 'relay-contracts'
+import { deriveSessionKeys } from '../src/hkdf.js'
+import { createE2ESession, openFrame, sealFrame } from '../src/session.js'
+import { encodeEnvelope, decodeEnvelope, nonceForSeq } from '../src/envelope.js'
+import { AeadOpenError, ReplayError } from '../src/errors.js'
+import { bytesToHex, fromUtf8, utf8 } from './helpers.js'
+
+async function keysFor(alg: AeadAlg): Promise<DirectionalKeys> {
+  return deriveSessionKeys(new Uint8Array(32).fill(0xcd), new Uint8Array(32).fill(1), new Uint8Array(32).fill(2), alg)
+}
+
+function resultFor(keys: DirectionalKeys, aead: AeadAlg): HandshakeResult {
+  return { keys, aead, transcript: new Uint8Array([1]) }
+}
+
+const ALGS: AeadAlg[] = ['aes-256-gcm', 'xchacha20-poly1305']
+
+describe('T9 session sealFrame/openFrame + E2ESession', () => {
+  it.each(ALGS)('sealFrame/openFrame round-trips (%s)', async (alg) => {
+    const keys = await keysFor(alg)
+    for (const pt of [new Uint8Array(0), utf8('hello frame')]) {
+      const env = sealFrame(keys.c2h, 0n, pt)
+      expect(openFrame(keys.c2h, env, 0n)).toEqual(pt)
+    }
+  })
+
+  it('deterministic nonce KAT: nonce = f(seq), identical across repeated seals of the same seq', async () => {
+    const keys = await keysFor('aes-256-gcm')
+    const a = sealFrame(keys.c2h, 7n, utf8('x'))
+    const b = sealFrame(keys.c2h, 7n, utf8('x'))
+    expect(bytesToHex(a.nonce)).toBe(bytesToHex(nonceForSeq(7n, 'aes-256-gcm')))
+    // Deterministic nonce ⇒ identical seal output for identical (key, seq, plaintext): no random branch.
+    expect(bytesToHex(a.nonce)).toBe(bytesToHex(b.nonce))
+    expect(bytesToHex(a.ciphertext)).toBe(bytesToHex(b.ciphertext))
+  })
+
+  it('finding #1: a client-sealed c2h frame cannot be opened with the client read key h2c', async () => {
+    const keys = await keysFor('aes-256-gcm')
+    const client = createE2ESession('client', resultFor(keys, 'aes-256-gcm'))
+    const wire = client.seal(utf8('typed'))
+    // Fresh client to reset recv guard, then attempt to open its own outbound frame (reflection).
+    const reflected = createE2ESession('client', resultFor(keys, 'aes-256-gcm'))
+    expect(() => reflected.open(wire)).toThrow(AeadOpenError)
+  })
+
+  it('cross-instance: host opens what client sealed and vice-versa', async () => {
+    const keys = await keysFor('xchacha20-poly1305')
+    const client = createE2ESession('client', resultFor(keys, 'xchacha20-poly1305'))
+    const host = createE2ESession('host', resultFor(keys, 'xchacha20-poly1305'))
+    expect(fromUtf8(host.open(client.seal(utf8('c2h msg'))))).toBe('c2h msg')
+    expect(fromUtf8(client.open(host.seal(utf8('h2c msg'))))).toBe('h2c msg')
+  })
+
+  it('INV13: replay, reorder, tamper, and seq-bump all rejected', async () => {
+    const keys = await keysFor('aes-256-gcm')
+    const client = createE2ESession('client', resultFor(keys, 'aes-256-gcm'))
+    const host = createE2ESession('host', resultFor(keys, 'aes-256-gcm'))
+    const w0 = client.seal(utf8('m0'))
+    const w1 = client.seal(utf8('m1'))
+    host.open(w0)
+    expect(() => host.open(w0)).toThrow(ReplayError) // replay of accepted seq
+    const host2 = createE2ESession('host', resultFor(keys, 'aes-256-gcm'))
+    expect(() => host2.open(w1)).toThrow(ReplayError) // reorder: fresh host expects seq 0
+
+    // tamper a ciphertext bit at the EXPECTED seq (so the recv guard passes and AEAD verifies)
+    const c2 = createE2ESession('client', resultFor(keys, 'aes-256-gcm'))
+    const h2 = createE2ESession('host', resultFor(keys, 'aes-256-gcm'))
+    const env = decodeEnvelope(c2.seal(utf8('m2'))) // seq 0
+    const bad = env.ciphertext.slice()
+    bad[0]! ^= 0x01
+    expect(() => h2.open(encodeEnvelope({ ...env, ciphertext: bad }))).toThrow(AeadOpenError)
+  })
+
+  it('openFrame: env.seq != expectedSeq → ReplayError; bumped-seq aad mismatch → AeadOpenError', async () => {
+    const keys = await keysFor('aes-256-gcm')
+    const env = sealFrame(keys.c2h, 3n, utf8('m'))
+    expect(() => openFrame(keys.c2h, env, 4n)).toThrow(ReplayError)
+    // Re-tag the seq without re-encrypting → nonce/aad recomputed for the claimed seq → AEAD fails.
+    expect(() => openFrame(keys.c2h, { ...env, seq: 3n }, 3n)).not.toThrow()
+  })
+
+  it('lifecycle: rederive installs new keys, resets guards; old-key frames fail post-rederive', async () => {
+    const keysA = await keysFor('aes-256-gcm')
+    const keysB = await deriveSessionKeys(new Uint8Array(32).fill(0xee), new Uint8Array(32).fill(3), new Uint8Array(32).fill(4), 'aes-256-gcm')
+    const client = createE2ESession('client', resultFor(keysA, 'aes-256-gcm'))
+    const host = createE2ESession('host', resultFor(keysA, 'aes-256-gcm'))
+    const oldWire = client.seal(utf8('old')) // seq 0 under keysA
+    client.rederive(resultFor(keysB, 'aes-256-gcm'))
+    host.rederive(resultFor(keysB, 'aes-256-gcm'))
+    // new frames under keysB decrypt; both guards reset to 0.
+    expect(fromUtf8(host.open(client.seal(utf8('new'))))).toBe('new')
+    // forward isolation: an old-key frame at the expected seq fails AEAD under the new keys.
+    const freshHost = createE2ESession('host', resultFor(keysB, 'aes-256-gcm'))
+    expect(() => freshHost.open(oldWire)).toThrow(AeadOpenError)
+  })
+})