diff --git a/smp-web/tests/agent-repl.ts b/smp-web/tests/agent-repl.ts
new file mode 100644
index 000000000..7d8cab320
--- /dev/null
+++ b/smp-web/tests/agent-repl.ts
@@ -0,0 +1,164 @@
+// Agent-level REPL for cross-language testing.
+// Uses AgentClient + smp-ops layer (not raw SMP client).
+// Reads commands from stdin, writes results to stdout.
+//
+// Commands:
+//   INIT <wsUrl> <keyHashHex> <userId>
+//   CREATE_QUEUE <connIdHex>
+//   SUBSCRIBE <connIdHex>
+//   RECV [timeoutMs]
+//   CB_ENCRYPT <dhSecretHex> <version> <bodyHex>
+//   CB_DECRYPT <dhSecretHex> <nonceHex> <ciphertextHex>
+//   CLOSE
+
+import "fake-indexeddb/auto"
+import {createInterface} from "readline"
+import {newAgentClient, defaultAgentConfig, type AgentClient as AC} from "../dist/agent/client.js"
+import {getSMPServerClient, agentCbEncrypt, agentCbDecrypt, newRcvQueue, subscribeQueues, type ServerMsg} from "../dist/agent/smp-ops.js"
+import {openAgentStore} from "../dist/agent/store-idb.js"
+import type {AgentStore} from "../dist/agent/store.js"
+import type {RcvQueueSub} from "../dist/agent/subscriptions.js"
+
+let agentClient: AC | null = null
+let store: AgentStore | null = null
+let serverUrl = ""
+let serverKeyHash: Uint8Array = new Uint8Array(0)
+let userId = 1
+
+function toHex(bytes: Uint8Array): string {
+  return Array.from(bytes, b => b.toString(16).padStart(2, "0")).join("")
+}
+
+function fromHex(hex: string): Uint8Array {
+  const bytes = new Uint8Array(hex.length / 2)
+  for (let i = 0; i < hex.length; i += 2)
+    bytes[i / 2] = parseInt(hex.substring(i, i + 2), 16)
+  return bytes
+}
+
+async function waitForMsg(c: AC, timeoutMs: number): Promise<ServerMsg> {
+  return new Promise((resolve, reject) => {
+    const timer = setTimeout(() => reject(new Error("timeout")), timeoutMs)
+    c.msgQ.dequeue().then(msg => {
+      clearTimeout(timer)
+      resolve(msg as ServerMsg)
+    }).catch(reject)
+  })
+}
+
+async function parseLine(line: string): Promise<string> {
+  const parts = line.trim().split(" ")
+  const cmd = parts[0]
+
+  try {
+    switch (cmd) {
+      case "INIT": {
+        serverUrl = parts[1]
+        serverKeyHash = fromHex(parts[2])
+        userId = parseInt(parts[3], 10)
+        store = await openAgentStore()
+        await store.createUserRecord()
+        agentClient = newAgentClient(defaultAgentConfig, store, new Map([[userId, {
+          storageSrvs: [[null, {server: parts[1], auth: null}]],
+          proxySrvs: [[null, {server: parts[1], auth: null}]],
+          knownHosts: new Set(),
+        }]]) as any)
+        const conn = await getSMPServerClient(agentClient, userId, parts[1], serverKeyHash, parts[1])
+        return "ok: " + toHex(conn.client.sessionId)
+      }
+
+      case "CREATE_QUEUE": {
+        if (!agentClient || !store) return "error: not initialized"
+        const connId = fromHex(parts[1])
+        await store.createNewConn({
+          connId, connMode: "INV", userId, smpAgentVersion: 8,
+          enableNtfs: true, duplexHandshake: true, deleted: false,
+          ratchetSyncState: "ok", pqSupport: false,
+          lastInternalMsgId: 0, lastInternalRcvMsgId: 0, lastInternalSndMsgId: 0,
+          lastExternalSndMsgId: 0, lastRcvMsgHash: new Uint8Array(0), lastSndMsgHash: new Uint8Array(0),
+        }, "INV")
+        const result = await newRcvQueue(agentClient, userId, connId, serverUrl, serverKeyHash, serverUrl, true)
+        await store.addConnRcvQueue(connId, {
+          host: result.rcvQueue.host, port: result.rcvQueue.port,
+          rcvId: result.rcvQueue.rcv_id, connId,
+          rcvPrivateKey: result.rcvQueue.rcv_private_key,
+          rcvDhSecret: result.rcvQueue.rcv_dh_secret,
+          e2ePrivKey: result.rcvQueue.e2e_priv_key,
+          e2eDhSecret: null,
+          sndId: result.rcvQueue.snd_id,
+          sndKey: null, status: "new",
+          smpClientVersion: result.rcvQueue.smp_client_version,
+          dbQueueId: 0, primary: true,
+          replaceRcvQueueId: null, queueMode: result.rcvQueue.queue_mode,
+          serverKeyHash, lastBrokerTs: null,
+        }, "SMSubscribe")
+        return "ok: " + toHex(result.rcvQueue.rcv_id) + " " + toHex(result.sndId) + " " + toHex(result.e2eDhKey)
+      }
+
+      case "SUBSCRIBE": {
+        if (!agentClient || !store) return "error: not initialized"
+        const connId = fromHex(parts[1])
+        const conn = await store.getConn(connId)
+        if (!conn) return "error: connection not found"
+        const rcvQueues = conn.rcvQueues as any[]
+        if (rcvQueues.length === 0) return "error: no rcv queues"
+        const subs: RcvQueueSub[] = rcvQueues.map((rq: any) => ({
+          userId, connId: rq.conn_id, server: serverUrl,
+          rcvId: rq.rcv_id, rcvPrivateKey: rq.rcv_private_key,
+          status: rq.status, enableNtfs: true, clientNoticeId: null,
+          dbQueueId: rq.rcv_queue_id, primary: !!rq.rcv_primary,
+          dbReplaceQueueId: null,
+        }))
+        await subscribeQueues(agentClient, userId, subs)
+        return "ok"
+      }
+
+      case "RECV": {
+        if (!agentClient) return "error: not initialized"
+        const timeoutMs = parts[1] ? parseInt(parts[1], 10) : 5000
+        const msg = await waitForMsg(agentClient, timeoutMs)
+        return "ok: " + toHex(msg.entityId) + " " + JSON.stringify(msg.msg)
+      }
+
+      case "CB_ENCRYPT": {
+        const dhSecret = fromHex(parts[1])
+        const version = parseInt(parts[2], 10)
+        const body = fromHex(parts[3])
+        const envelope = agentCbEncrypt(dhSecret, version, null, body)
+        return "ok: " + toHex(envelope)
+      }
+
+      case "CB_DECRYPT": {
+        const dhSecret = fromHex(parts[1])
+        const nonce = fromHex(parts[2])
+        const ct = fromHex(parts[3])
+        const pt = agentCbDecrypt(dhSecret, nonce, ct)
+        return "ok: " + toHex(pt)
+      }
+
+      case "CLOSE": {
+        if (agentClient) {
+          agentClient.active = false
+          for (const [, sv] of agentClient.smpClients as Map<string, any>) {
+            if (sv.value?.client) sv.value.client.close()
+          }
+        }
+        return "ok"
+      }
+
+      default:
+        return "error: unknown command: " + cmd
+    }
+  } catch (e: any) {
+    return "error: " + (e?.message || String(e))
+  }
+}
+
+const rl = createInterface({input: process.stdin, output: process.stdout, terminal: false})
+
+rl.on("line", async (line: string) => {
+  const result = await parseLine(line)
+  process.stdout.write(result + "\n")
+})
+
+rl.on("close", () => process.exit(0))
diff --git a/tests/SMPWebTests.hs b/tests/SMPWebTests.hs
index 8b93e8805..bf6566737 100644
--- a/tests/SMPWebTests.hs
+++ b/tests/SMPWebTests.hs
@@ -237,6 +237,14 @@ spawnJsClient = do
   hSetBuffering hOut LineBuffering
   pure (hIn, hOut, ph)
 
+spawnJsAgent :: IO (Handle, Handle, ProcessHandle)
+spawnJsAgent = do
+  let cp = (proc "node" ["dist-test/agent-repl.js"]) {cwd = Just "smp-web", std_in = CreatePipe, std_out = CreatePipe, std_err = Inherit}
+  (Just hIn, Just hOut, _, ph) <- createProcess cp
+  hSetBuffering hIn LineBuffering
+  hSetBuffering hOut LineBuffering
+  pure (hIn, hOut, ph)
+
 destroyJsRatchet :: TestPeer -> IO ()
 destroyJsRatchet (TestPeerJS _ _ ph) = terminateProcess ph
 destroyJsRatchet _ = pure ()
@@ -1883,3 +1891,55 @@ smpWebTests_ = do
           _ <- jsCmd rcvIn rcvOut "CLOSE"
           terminateProcess rcvPh
 
+  describe "agent-repl" $ do
+    it "agentCbEncrypt cross-language: TS encrypts, Haskell decrypts" $ do
+      g <- C.newRandom
+      -- Generate shared DH secret
+      (rcvPub, _rcvPriv) <- atomically $ C.generateKeyPair @'C.X25519 g
+      (_sndPub, sndPriv) <- atomically $ C.generateKeyPair @'C.X25519 g
+      let dhSecret = C.dh' rcvPub sndPriv
+          C.DhSecretX25519 dhSecretRaw = dhSecret
+          dhSecretBytes = BA.convert dhSecretRaw :: B.ByteString
+          plaintext = "hello from typescript"
+          versionInt = 18 :: Int
+      -- TS: encrypt
+      (hIn, hOut, ph) <- spawnJsAgent
+      tsResp <- jsCmd hIn hOut $ "CB_ENCRYPT " <> bsToHex dhSecretBytes <> " " <> show versionInt <> " " <> bsToHex plaintext
+      let tsParts = words tsResp
+      head tsParts `shouldBe` "ok:"
+      let envelopeHex = tsParts !! 1
+          envelopeBytes = hexToBS envelopeHex
+      -- Haskell: decode ClientMsgEnvelope and decrypt
+      ClientMsgEnvelope {cmHeader = PubHeader ver _, cmNonce = nonce, cmEncBody = encBody} <- either fail pure $ smpDecode envelopeBytes
+      show ver `shouldBe` "Version 18"
+      decrypted <- either (fail . show) pure $ C.cbDecrypt dhSecret nonce encBody
+      -- The plaintext is padded — first bytes should match
+      B.take (B.length plaintext) decrypted `shouldBe` plaintext
+      _ <- jsCmd hIn hOut "CLOSE"
+      terminateProcess ph
+
+    it "agentCbEncrypt cross-language: Haskell encrypts, TS decrypts" $ do
+      g <- C.newRandom
+      -- Generate shared DH secret
+      (rcvPub, _rcvPriv) <- atomically $ C.generateKeyPair @'C.X25519 g
+      (_sndPub, sndPriv) <- atomically $ C.generateKeyPair @'C.X25519 g
+      let dhSecret = C.dh' rcvPub sndPriv
+          C.DhSecretX25519 dhSecretRaw = dhSecret
+          dhSecretBytes = BA.convert dhSecretRaw :: B.ByteString
+          plaintext = "hello from haskell"
+      -- Haskell: encrypt
+      cbNonce <- atomically $ C.randomCbNonce g
+      encBody <- either (fail . show) pure $ C.cbEncrypt dhSecret cbNonce plaintext 16000
+      let C.CbNonce nonceBytes = cbNonce
+      -- TS: decrypt
+      (hIn, hOut, ph) <- spawnJsAgent
+      tsResp <- jsCmd hIn hOut $ "CB_DECRYPT " <> bsToHex dhSecretBytes <> " " <> bsToHex nonceBytes <> " " <> bsToHex encBody
+      let tsParts = words tsResp
+      head tsParts `shouldBe` "ok:"
+      let decryptedHex = tsParts !! 1
+          decrypted = hexToBS decryptedHex
+      -- Decrypted is padded — first bytes should match
+      B.take (B.length plaintext) decrypted `shouldBe` plaintext
+      _ <- jsCmd hIn hOut "CLOSE"
+      terminateProcess ph
+