diff --git a/.gitignore b/.gitignore
index df9289e..34c4488 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 node_modules
 sandbox.js
+sandbox.mjs
 sandbox
 coverage
diff --git a/index.js b/index.js
index fc9505f..55026d0 100644
--- a/index.js
+++ b/index.js
@@ -1,410 +1,626 @@
-const c = require('compact-encoding')
 const b4a = require('b4a')
+const c = require('compact-encoding')
+const queueTick = require('queue-tick')
 const safetyCatch = require('safety-catch')
-const { addProtocol } = require('./messages')
 
-const EMPTY = []
+const MAX_BUFFERED = 32768
+const MAX_BACKLOG = 256
 
-class Protocol {
-  constructor (mux) {
-    this.mux = mux
-
-    this.name = null
-    this.version = null
-    this.messages = EMPTY
-    this.context = null
-    this.offset = 0
-    this.length = 0
-    this.opened = false
-    this.corked = false
-
-    this.remoteVersion = null
-    this.remoteOffset = 0
-    this.remoteEnd = 0
-    this.remoteOpened = false
-    this.remoteClosed = false
-
-    this.onremoteopen = noop
-    this.onremoteclose = noop
-  }
-
-  _attach ({ name, version = { major: 0, minor: 0 }, messages = 0, context = null, onremoteopen = noop, onremoteclose = noop }) {
-    const opened = this.opened
-
-    this.name = name
-    this.version = version
-    this.messages = new Array(messages)
+class Session {
+  constructor (mux, info, protocol, id, context, messages, onopen, onclose, ondestroy) {
+    this.protocol = protocol
+    this.id = id
     this.context = context
-    this.offset = this.mux.offset
-    this.length = messages
-    this.opened = true
-    this.corked = false
+    this.messages = []
+    this.remoteMessages = this.messages
 
-    this.onremoteopen = onremoteopen
-    this.onremoteclose = onremoteclose
+    this.opened = false
+    this.closed = false
+    this.destroyed = false
 
-    return !opened
+    this.onopen = onopen
+    this.onclose = onclose
+    this.ondestroy = ondestroy
+
+    this._mux = mux
+    this._info = info
+    this._localId = 0
+    this._remoteId = 0
+    this._active = 0
+    this._extensions = null
+
+    this._decBound = this._dec.bind(this)
+    this._decAndDestroyBound = this._decAndDestroy.bind(this)
+
+    for (const m of messages) this.addMessage(m)
   }
 
-  _nextMessage () {
-    for (let i = this.messages.length - 1; i >= 0; i--) {
-      if (this.messages[i] === undefined && (i === 0 || this.messages[i - 1] !== undefined)) {
-        return i
+  _open () {
+    const id = this._mux._free.length > 0
+      ? this._mux._free.pop()
+      : this._mux._local.push(null) - 1
+
+    this._info.opened++
+    this._localId = id + 1
+    this._mux._local[id] = this
+
+    const state = { buffer: null, start: 2, end: 2 }
+
+    c.string.preencode(state, this.protocol)
+    c.buffer.preencode(state, this.id)
+    c.uint.preencode(state, this._localId)
+
+    state.buffer = this._mux._alloc(state.end)
+
+    state.buffer[0] = 0
+    state.buffer[1] = 1
+    c.string.encode(state, this.protocol)
+    c.buffer.encode(state, this.id)
+    c.uint.encode(state, this._localId)
+
+    this._mux._write0(state.buffer)
+  }
+
+  _dec () {
+    if (--this._active === 0 && this.closed === true) this._destroy()
+  }
+
+  _decAndDestroy (err) {
+    this._dec()
+    this._mux._safeDestroy(err)
+  }
+
+  _fullyOpenSoon () {
+    this._mux._remote[this._remoteId - 1].session = this
+    queueTick(this._fullyOpen.bind(this))
+  }
+
+  _fullyOpen () {
+    if (this.opened === true || this.closed === true) return
+
+    const remote = this._mux._remote[this._remoteId - 1]
+
+    this.opened = true
+    this._track(this.onopen())
+
+    remote.session = this
+    if (remote.pending !== null) this._drain(remote)
+  }
+
+  _drain (remote) {
+    for (let i = 0; i < remote.pending.length; i++) {
+      const p = remote.pending[i]
+      this._mux._buffered -= byteSize(p.state)
+      this._recv(p.type, p.state)
+    }
+
+    remote.pending = null
+    this._mux._resumeMaybe()
+  }
+
+  _track (p) {
+    if (isPromise(p) === true) {
+      this._active++
+      p.then(this._decBound, this._decAndDestroyBound)
+    }
+  }
+
+  _close (isRemote) {
+    if (this.closed === true) return
+    this.closed = true
+
+    this._info.opened--
+
+    if (this._remoteId > 0) {
+      this._mux._remote[this._remoteId - 1] = null
+      this._remoteId = 0
+      // If remote has acked, we can reuse the local id now
+      // otherwise, we need to wait for the "ack" to arrive
+      this._mux._free.push(this._localId - 1)
+    }
+
+    this._mux._local[this._localId - 1] = null
+    this._localId = 0
+
+    this._mux._gc(this._info)
+    this._track(this.onclose(isRemote))
+
+    if (this._active === 0) this._destroy()
+  }
+
+  _destroy () {
+    if (this.destroyed === true) return
+    this.destroyed = true
+    this._track(this.ondestroy())
+  }
+
+  _recv (type, state) {
+    if (type < this.remoteMessages.length) {
+      this.remoteMessages[type].recv(state, this)
+    }
+  }
+
+  cork () {
+    this._mux.cork()
+  }
+
+  uncork () {
+    this._mux.uncork()
+  }
+
+  close () {
+    if (this.closed === true) return
+
+    const state = { buffer: null, start: 2, end: 2 }
+
+    c.uint.preencode(state, this._localId)
+
+    state.buffer = this._mux._alloc(state.end)
+
+    state.buffer[0] = 0
+    state.buffer[1] = 3
+    c.uint.encode(state, this._localId)
+
+    this._close(false)
+    this._mux._write0(state.buffer)
+  }
+
+  addMessage (opts) {
+    if (!opts) return this._skipMessage()
+
+    const type = this.messages.length
+    const encoding = opts.encoding || c.raw
+    const onmessage = opts.onmessage || noop
+
+    const s = this
+    const typeLen = encodingLength(c.uint, type)
+
+    const m = {
+      type,
+      encoding,
+      onmessage,
+      recv (state, session) {
+        session._track(m.onmessage(encoding.decode(state), session))
+      },
+      send (m, session = s) {
+        if (session.closed === true) return false
+
+        const mux = session._mux
+        const state = { buffer: null, start: 0, end: typeLen }
+
+        if (mux._batch !== null) {
+          encoding.preencode(state, m)
+          state.buffer = mux._alloc(state.end)
+
+          c.uint.encode(state, type)
+          encoding.encode(state, m)
+
+          mux._pushBatch(session._localId, state.buffer)
+          return true
+        }
+
+        c.uint.preencode(state, session._localId)
+        encoding.preencode(state, m)
+
+        state.buffer = mux._alloc(state.end)
+
+        c.uint.encode(state, session._localId)
+        c.uint.encode(state, type)
+        encoding.encode(state, m)
+
+        return mux.stream.write(state.buffer)
       }
     }
-    return -1
-  }
 
-  addMessage ({ type = this._nextMessage(), encoding = c.binary, onmessage = noop } = {}) {
-    if (type < 0 || type >= this.messages.length) {
-      throw new Error('Invalid type, must be <= ' + this.messages.length)
-    }
-
-    const t = this.offset + type
-    const send = (message) => this.opened && this.mux._push(t, m.encoding, message)
-    const m = this.messages[type] = { encoding, onmessage, send }
+    this.messages.push(m)
 
     return m
   }
 
-  cork () {
-    if (this.corked) return
-    this.corked = true
-    this.mux.cork()
-  }
+  _skipMessage () {
+    const type = this.messages.length
+    const m = {
+      type,
+      encoding: c.raw,
+      onmessage: noop,
+      recv (state, session) {},
+      send (m, session) {}
+    }
 
-  uncork () {
-    if (!this.corked) return
-    this.corked = false
-    this.mux.uncork()
-  }
-
-  close () {
-    if (this.opened === false) return
-    this.opened = false
-    this.mux._unopened++
-
-    const offset = this.offset
-
-    this.version = null
-    this.messages = EMPTY
-    this.offset = 0
-    this.length = 0
-    this.onremoteopen = this.onremoteclose = noop
-    this.mux._push(2, c.uint, offset)
-    this._gc()
-
-    if (this.corked) this.uncork()
-  }
-
-  _gc () {
-    if (this.opened || this.remoteOpened) return
-    this.mux._removeProtocol(this)
-  }
-
-  _recv (type, state) {
-    if (type >= this.messages.length) return
-
-    const m = this.messages[type]
-    if (m !== undefined) this.mux._catch(m.onmessage(m.encoding.decode(state), this.context))
+    this.messages.push(m)
+    return m
   }
 }
 
 module.exports = class Protomux {
-  constructor (stream, { backlog = 128, alloc, onacceptprotocol } = {}) {
-    this.stream = stream
-    this.protocols = []
-    this.remoteProtocols = []
-    this.offset = 4 // 4 messages reserved
-    this.corked = 0
-    this.backlog = backlog
-    this.onacceptprotocol = onacceptprotocol || (() => this._unopened < this.backlog)
+  constructor (stream, { alloc } = {}) {
     this.isProtomux = true
+    this.stream = stream
+    this.corked = 0
 
-    this._unopened = 0
-    this._batch = null
     this._alloc = alloc || (typeof stream.alloc === 'function' ? stream.alloc.bind(stream) : b4a.allocUnsafe)
     this._safeDestroyBound = this._safeDestroy.bind(this)
 
+    this._remoteBacklog = 0
+    this._buffered = 0
+    this._paused = false
+    this._remote = []
+    this._local = []
+    this._free = []
+    this._batch = null
+    this._batchState = null
+
+    this._infos = new Map()
+    this._notify = new Map()
+
     this.stream.on('data', this._ondata.bind(this))
+    this.stream.on('error', noop) // we handle this in "close"
     this.stream.on('close', this._shutdown.bind(this))
   }
 
-  static from (other, opts) {
-    return other.isProtomux === true ? other : new Protomux(other, opts)
+  static from (stream, opts) {
+    if (stream.isProtomux) return stream
+    return new this(stream, opts)
   }
 
-  sendKeepAlive () {
-    this.stream.write(this._alloc(0))
+  * [Symbol.iterator] () {
+    for (const session of this._local) {
+      if (session !== null) yield session
+    }
   }
 
   cork () {
-    if (++this.corked === 1) this._batch = []
+    if (++this.corked === 1) {
+      this._batch = []
+      this._batchState = { buffer: null, start: 0, end: 1 }
+    }
   }
 
   uncork () {
-    if (--this.corked !== 0) return
-
-    const batch = this._batch
-    this._batch = null
-
-    const state = { start: 0, end: 1, buffer: null }
-    const lens = new Array(batch.length)
-
-    for (let i = 0; i < batch.length; i++) {
-      const b = batch[i]
-      const end = state.end
-
-      c.uint.preencode(state, b.type)
-      b.encoding.preencode(state, b.message)
-      c.uint.preencode(state, lens[i] = (state.end - end))
+    if (--this.corked === 0) {
+      this._sendBatch(this._batch, this._batchState)
+      this._batch = null
+      this._batchState = null
     }
+  }
+
+  pair ({ protocol, id = null }, notify) {
+    this._notify.set(toKey(protocol, id), notify)
+  }
+
+  unpair ({ protocol, id = null }) {
+    this._notify.delete(toKey(protocol, id))
+  }
+
+  opened ({ protocol, id = null }) {
+    const key = toKey(protocol, id)
+    const info = this._infos.get(key)
+    return info ? info.opened > 0 : false
+  }
+
+  open ({ protocol, id = null, context = null, unique = true, messages = [], onopen = noop, onclose = noop, ondestroy = noop }) {
+    if (this.stream.destroyed) return null
+
+    const info = this._get(protocol, id)
+    if (unique && info.opened > 0) return null
+
+    if (info.incoming.length === 0) {
+      const session = new Session(this, info, protocol, id, context, messages, onopen, onclose, ondestroy)
+      session._open()
+      info.outgoing.push(session._localId)
+      return session
+    }
+
+    this._remoteBacklog--
+
+    const remoteId = info.incoming.shift()
+    const r = this._remote[remoteId - 1]
+    if (r === null) return null
+
+    const session = new Session(this, info, protocol, id, context, messages, onopen, onclose, ondestroy)
+
+    session._remoteId = remoteId
+    session._open()
+    session._fullyOpenSoon()
+
+    return session
+  }
+
+  _pushBatch (localId, buffer) {
+    if (this._batch.length === 0 || this._batch[this._batch.length - 1].localId !== localId) {
+      this._batchState.end++
+      c.uint.preencode(this._batchState, localId)
+    }
+    c.buffer.preencode(this._batchState, buffer)
+    this._batch.push({ localId, buffer })
+  }
+
+  _sendBatch (batch, state) {
+    if (batch.length === 0) return
+
+    let prev = batch[0].localId
 
     state.buffer = this._alloc(state.end)
     state.buffer[state.start++] = 0
+    state.buffer[state.start++] = 0
+
+    c.uint.encode(state, prev)
 
     for (let i = 0; i < batch.length; i++) {
       const b = batch[i]
-
-      c.uint.encode(state, lens[i])
-      c.uint.encode(state, b.type)
-      b.encoding.encode(state, b.message)
+      if (prev !== b.localId) {
+        state.buffer[state.start++] = 0
+        c.uint.encode(state, (prev = b.localId))
+      }
+      c.buffer.encode(state, b.buffer)
     }
 
     this.stream.write(state.buffer)
   }
 
-  hasProtocol (opts) {
-    return !!this.getProtocol(opts)
+  _get (protocol, id) {
+    const key = toKey(protocol, id)
+
+    let info = this._infos.get(key)
+    if (info) return info
+
+    info = { key, protocol, id, pairing: 0, opened: 0, incoming: [], outgoing: [] }
+    this._infos.set(key, info)
+    return info
   }
 
-  getProtocol ({ name, version }) {
-    return this._getProtocol(name, version, false)
-  }
-
-  addProtocol (opts) {
-    const p = this._getProtocol(opts.name, (opts.version && opts.version.major) || 0, true)
-
-    if (opts.cork) p.cork()
-    if (!p._attach(opts)) return p
-
-    this._unopened--
-    this.offset += p.length
-    this._push(1, addProtocol, {
-      name: p.name,
-      version: p.version,
-      offset: p.offset,
-      length: p.length
-    })
-
-    return p
-  }
-
-  destroy (err) {
-    this.stream.destroy(err)
-  }
-
-  _shutdown () {
-    while (this.protocols.length) {
-      const p = this.protocols.pop()
-      if (!p.remoteOpened) continue
-      if (p.remoteClosed) continue
-      p.remoteOpened = false
-      p.remoteClosed = true
-      this._catch(p.onremoteclose())
-    }
-  }
-
-  _safeDestroy (err) {
-    safetyCatch(err)
-    this.destroy(err)
-  }
-
-  _catch (p) {
-    if (isPromise(p)) p.catch(this._safeDestroyBound)
-  }
-
-  async _acceptMaybe (added) {
-    let accept = false
-
-    try {
-      accept = await this.onacceptprotocol(added)
-    } catch (err) {
-      this._safeDestroy(err)
-      return
-    }
-
-    if (!accept) this._rejectProtocol(added)
-  }
-
-  _rejectProtocol (added) {
-    for (let i = 0; i < this.protocols.length; i++) {
-      const p = this.protocols[i]
-      if (p.opened || p.name !== added.name || !p.remoteOpened) continue
-      if (p.remoteVersion.major !== added.version.major) continue
-
-      this._unopened--
-      this.protocols.splice(i, 1)
-      this._push(3, c.uint, added.offset)
-      return
+  _gc (info) {
+    if (info.opened === 0 && info.outgoing.length === 0 && info.incoming.length === 0) {
+      this._infos.delete(info.key)
     }
   }
 
   _ondata (buffer) {
-    if (buffer.byteLength === 0) return // keep alive
-
-    const end = buffer.byteLength
-    const state = { start: 0, end, buffer }
-
     try {
-      const type = c.uint.decode(state)
-      if (type === 0) this._recvBatch(end, state)
-      else this._recv(type, state)
+      const state = { buffer, start: 0, end: buffer.byteLength }
+      this._decode(c.uint.decode(state), state)
     } catch (err) {
       this._safeDestroy(err)
     }
   }
 
-  _getProtocol (name, major, upsert) {
-    for (let i = 0; i < this.protocols.length; i++) {
-      const p = this.protocols[i]
-      const v = p.remoteVersion === null ? p.version : p.remoteVersion
-      if (p.name === name && (v !== null && v.major === major)) return p
+  _decode (remoteId, state) {
+    const type = c.uint.decode(state)
+
+    if (remoteId === 0) {
+      this._oncontrolsession(type, state)
+      return
     }
 
-    if (!upsert) return null
+    const r = remoteId <= this._remote.length ? this._remote[remoteId - 1] : null
 
-    const p = new Protocol(this)
-    this.protocols.push(p)
-    this._unopened++
-    return p
+    // if the channel is closed ignore - could just be a pipeline message...
+    if (r === null) return
+
+    if (r.pending !== null) {
+      this._bufferMessage(r, type, state)
+      return
+    }
+
+    r.session._recv(type, state)
   }
 
-  _removeProtocol (p) {
-    const i = this.protocols.indexOf(this)
-    if (i > -1) this.protocols.splice(i, 1)
-    if (!p.opened) this._unopened--
-  }
+  _oncontrolsession (type, state) {
+    switch (type) {
+      case 0:
+        this._onbatch(state)
+        break
 
-  _recvAddProtocol (state) {
-    const add = addProtocol.decode(state)
+      case 1:
+        this._onopensession(state)
+        break
 
-    const p = this._getProtocol(add.name, add.version.major, true)
-    if (p.remoteOpened) throw new Error('Duplicate protocol received')
+      case 2:
+        this._onrejectsession(state)
+        break
 
-    p.name = add.name
-    p.remoteVersion = add.version
-    p.remoteOffset = add.offset
-    p.remoteEnd = add.offset + add.length
-    p.remoteOpened = true
-    p.remoteClosed = false
-
-    if (p.opened) {
-      this._catch(p.onremoteopen())
-    } else {
-      this._acceptMaybe(add)
+      case 3:
+        this._onclosesession(state)
+        break
     }
   }
 
-  _recvRemoveProtocol (state) {
-    const offset = c.uint.decode(state)
-
-    for (let i = 0; i < this.protocols.length; i++) {
-      const p = this.protocols[i]
-
-      if (p.remoteOffset === offset && p.remoteOpened) {
-        p.remoteVersion = null
-        p.remoteOpened = false
-        p.remoteClosed = true
-        this._catch(p.onremoteclose())
-        p._gc()
-        return
-      }
-    }
+  _bufferMessage (r, type, { buffer, start, end }) {
+    const state = { buffer, start, end } // copy
+    r.pending.push({ type, state })
+    this._buffered += byteSize(state)
+    this._pauseMaybe()
   }
 
-  _recvRejectedProtocol (state) {
-    const offset = c.uint.decode(state)
-
-    for (let i = 0; i < this.protocols.length; i++) {
-      const p = this.protocols[i]
-
-      if (p.offset === offset && !p.remoteClosed) {
-        p.remoteClosed = true
-        this._catch(p.onremoteclose())
-        p._gc()
-      }
-    }
+  _pauseMaybe () {
+    if (this._paused === true || this._buffered <= MAX_BUFFERED) return
+    this._paused = true
+    this.stream.pause()
   }
 
-  _recvBatch (end, state) {
-    while (state.start < state.end) {
+  _resumeMaybe () {
+    if (this._paused === false || this._buffered > MAX_BUFFERED) return
+    this._paused = false
+    this.stream.resume()
+  }
+
+  _onbatch (state) {
+    const end = state.end
+    let remoteId = c.uint.decode(state)
+
+    while (state.end > state.start) {
       const len = c.uint.decode(state)
-      const type = c.uint.decode(state)
-      state.end = state.start + len
-      this._recv(type, state)
+      if (len === 0) {
+        remoteId = c.uint.decode(state)
+        continue
+      }
+      state.end = state.start + end
+      this._decode(remoteId, state)
       state.end = end
     }
   }
 
-  _recv (type, state) {
-    if (type < 4) {
-      if (type === 0) {
-        throw new Error('Invalid nested batch')
-      }
-
-      if (type === 1) {
-        this._recvAddProtocol(state)
-        return
-      }
-
-      if (type === 2) {
-        this._recvRemoveProtocol(state)
-        return
-      }
-
-      if (type === 3) {
-        this._recvRejectedProtocol(state)
-        return
-      }
+  _onopensession (state) {
+    const protocol = c.string.decode(state)
+    const id = c.buffer.decode(state)
+    const remoteId = c.uint.decode(state)
 
+    // remote tried to open the control session - auto reject for now
+    // as we can use as an explicit control protocol declaration if we need to
+    if (remoteId === 0) {
+      this._rejectSession(0)
       return
     }
 
-    // TODO: Consider make this array sorted by remoteOffset and use a bisect here.
-    // For now we use very few protocols in practice, so it might be overkill.
-    for (let i = 0; i < this.protocols.length; i++) {
-      const p = this.protocols[i]
+    const rid = remoteId - 1
+    const info = this._get(protocol, id)
 
-      if (p.remoteOffset <= type && type < p.remoteEnd) {
-        p._recv(type - p.remoteOffset, state)
-        break
-      }
+    // allow the remote to grow the ids by one
+    if (this._remote.length === rid) {
+      this._remote.push(null)
     }
+
+    if (rid >= this._remote.length || this._remote[rid] !== null) {
+      throw new Error('Invalid open message')
+    }
+
+    if (info.outgoing.length > 0) {
+      const localId = info.outgoing.shift()
+      const session = this._local[localId - 1]
+
+      if (session === null) { // we already closed the channel - ignore
+        this._free.push(localId - 1)
+        return
+      }
+
+      this._remote[rid] = { pending: null, session: null }
+
+      session._remoteId = remoteId
+      session._fullyOpen()
+      return
+    }
+
+    this._remote[rid] = { pending: [], session: null }
+
+    if (++this._remoteBacklog > MAX_BACKLOG) {
+      throw new Error('Remote exceeded backlog')
+    }
+
+    info.pairing++
+    info.incoming.push(remoteId)
+
+    this._requestSession(protocol, id, info).catch(this._safeDestroyBound)
   }
 
-  _push (type, enc, message) {
-    if (this.corked > 0) {
-      this._batch.push({ type, encoding: enc, message })
-      return false
+  _onrejectsession (state) {
+    const protocol = c.string.decode(state)
+    const id = c.buffer.decode(state)
+    const info = this._get(protocol, id)
+
+    if (info.outgoing.length === 0) {
+      throw new Error('Invalid reject message')
     }
 
-    const state = { start: 0, end: 0, buffer: null }
+    const localId = info.outgoing.shift()
+    const session = this._local[localId - 1]
 
-    c.uint.preencode(state, type)
-    enc.preencode(state, message)
+    this._free.push(localId - 1)
+    if (session !== null) session._close(true)
+  }
+
+  _onclosesession (state) {
+    const remoteId = c.uint.decode(state)
+
+    if (remoteId === 0) return // ignore
+
+    const rid = remoteId - 1
+    const r = rid < this._remote.length ? this._remote[rid] : null
+
+    if (r === null) return
+
+    if (r.session !== null) r.session._close(true)
+  }
+
+  async _requestSession (protocol, id, info) {
+    const notify = this._notify.get(toKey(protocol, id)) || this._notify.get(toKey(protocol, null))
+
+    if (notify) await notify(id)
+
+    if (--info.pairing > 0) return
+
+    while (info.incoming.length > 0) {
+      this._rejectSession(info, info.incoming.pop())
+    }
+
+    this._gc(info)
+  }
+
+  _rejectSession (info, remoteId) {
+    if (remoteId > 0) {
+      const r = this._remote[remoteId - 1]
+
+      if (r.pending !== null) {
+        for (let i = 0; i < r.pending.length; i++) {
+          this._buffered -= byteSize(r.pending[i].state)
+        }
+      }
+
+      this._remote[remoteId - 1] = null
+      this._resumeMaybe()
+    }
+
+    const state = { buffer: null, start: 2, end: 2 }
+
+    c.string.preencode(state, info.protocol)
+    c.buffer.preencode(state, info.id)
 
     state.buffer = this._alloc(state.end)
 
-    c.uint.encode(state, type)
-    enc.encode(state, message)
+    state.buffer[0] = 0
+    state.buffer[1] = 2
+    c.string.encode(state, info.protocol)
+    c.buffer.encode(state, info.id)
 
-    return this.stream.write(state.buffer)
+    this._write0(state.buffer)
+  }
+
+  _write0 (buffer) {
+    if (this._batch !== null) {
+      this._pushBatch(0, buffer.subarray(1))
+      return
+    }
+
+    this.stream.write(buffer)
+  }
+
+  _safeDestroy (err) {
+    safetyCatch(err)
+    this.stream.destroy(err)
+  }
+
+  _shutdown () {
+    for (const s of this._local) {
+      if (s !== null) s._close(true)
+    }
   }
 }
 
 function noop () {}
 
-function isPromise (p) {
-  return typeof p === 'object' && p !== null && !!p.catch
+function toKey (protocol, id) {
+  return protocol + '##' + (id ? b4a.toString(id, 'hex') : '')
+}
+
+function byteSize (state) {
+  return 512 + (state.end - state.start)
+}
+
+function isPromise (p) {
+  return !!(p && typeof p.then === 'function')
+}
+
+function encodingLength (enc, val) {
+  const state = { buffer: null, start: 0, end: 0 }
+  enc.preencode(state, val)
+  return state.end
 }
diff --git a/messages.js b/messages.js
deleted file mode 100644
index 4ea764c..0000000
--- a/messages.js
+++ /dev/null
@@ -1,41 +0,0 @@
-const c = require('compact-encoding')
-
-const version = {
-  preencode (state, v) {
-    c.uint.preencode(state, v.major)
-    c.uint.preencode(state, v.minor)
-  },
-  encode (state, v) {
-    c.uint.encode(state, v.major)
-    c.uint.encode(state, v.minor)
-  },
-  decode (state, v) {
-    return {
-      major: c.uint.decode(state),
-      minor: c.uint.decode(state)
-    }
-  }
-}
-
-exports.addProtocol = {
-  preencode (state, p) {
-    c.string.preencode(state, p.name)
-    version.preencode(state, p.version)
-    c.uint.preencode(state, p.offset)
-    c.uint.preencode(state, p.length)
-  },
-  encode (state, p) {
-    c.string.encode(state, p.name)
-    version.encode(state, p.version)
-    c.uint.encode(state, p.offset)
-    c.uint.encode(state, p.length)
-  },
-  decode (state, p) {
-    return {
-      name: c.string.decode(state),
-      version: version.decode(state),
-      offset: c.uint.decode(state),
-      length: c.uint.decode(state)
-    }
-  }
-}
diff --git a/test.js b/test.js
index 6ecc90f..a6d017c 100644
--- a/test.js
+++ b/test.js
@@ -9,10 +9,9 @@ test('basic', function (t) {
 
   replicate(a, b)
 
-  const p = a.addProtocol({
-    name: 'foo',
-    messages: 1,
-    onremoteopen () {
+  const p = a.open({
+    protocol: 'foo',
+    onopen () {
       t.pass('a remote opened')
     }
   })
@@ -24,9 +23,8 @@ test('basic', function (t) {
     }
   })
 
-  const bp = b.addProtocol({
-    name: 'foo',
-    messages: 1
+  const bp = b.open({
+    protocol: 'foo'
   })
 
   t.plan(2)
@@ -40,9 +38,8 @@ test('echo message', function (t) {
 
   replicate(a, b)
 
-  const ap = a.addProtocol({
-    name: 'foo',
-    messages: 1
+  const ap = a.open({
+    protocol: 'foo'
   })
 
   const aEcho = ap.addMessage({
@@ -52,15 +49,13 @@ test('echo message', function (t) {
     }
   })
 
-  b.addProtocol({
-    name: 'other',
-    messages: 2
+  b.open({
+    protocol: 'other'
   })
 
-  const bp = b.addProtocol({
-    name: 'foo',
-    messages: 1,
-    onremoteopen () {
+  const bp = b.open({
+    protocol: 'foo',
+    onopen () {
       t.pass('b remote opened')
     }
   })
@@ -80,14 +75,12 @@ test('echo message', function (t) {
 test('multi message', function (t) {
   const a = new Protomux(new SecretStream(true))
 
-  a.addProtocol({
-    name: 'other',
-    messages: 2
+  a.open({
+    protocol: 'other'
   })
 
-  const ap = a.addProtocol({
-    name: 'multi',
-    messages: 3
+  const ap = a.open({
+    protocol: 'multi'
   })
 
   const a1 = ap.addMessage({ encoding: c.int })
@@ -96,9 +89,8 @@ test('multi message', function (t) {
 
   const b = new Protomux(new SecretStream(false))
 
-  const bp = b.addProtocol({
-    name: 'multi',
-    messages: 2
+  const bp = b.open({
+    protocol: 'multi'
   })
 
   const b1 = bp.addMessage({ encoding: c.int })
@@ -131,14 +123,12 @@ test('corks', function (t) {
 
   a.cork()
 
-  a.addProtocol({
-    name: 'other',
-    messages: 2
+  a.open({
+    protocol: 'other'
   })
 
-  const ap = a.addProtocol({
-    name: 'multi',
-    messages: 2
+  const ap = a.open({
+    protocol: 'multi'
   })
 
   const a1 = ap.addMessage({ encoding: c.int })
@@ -146,9 +136,8 @@ test('corks', function (t) {
 
   const b = new Protomux(new SecretStream(false))
 
-  const bp = b.addProtocol({
-    name: 'multi',
-    messages: 2
+  const bp = b.open({
+    protocol: 'multi'
   })
 
   const b1 = bp.addMessage({ encoding: c.int })