diff --git a/lib/algorithm.js b/lib/algorithm.js
index a33b1a5..476ec9e 100644
--- a/lib/algorithm.js
+++ b/lib/algorithm.js
@@ -1,19 +1,21 @@
+// @ts-ignore
+const multicb = require('multicb')
+const p = require('promisify-4loc')
 const { BloomFilter } = require('bloom-filters')
 const MsgV3 = require('ppppp-db/msg-v3')
-const p = require('util').promisify
 const { EMPTY_RANGE, isEmptyRange, estimateMsgCount } = require('./range')
 
 /**
- * @typedef {import('./range').Range} Range
+ * @typedef {ReturnType<import('ppppp-db').init>} PPPPPDB
  * @typedef {import('ppppp-db/msg-v3').Msg} Msg
- *
- * @typedef {{
- *   type: 'all' | 'newest' | 'oldest',
- *   count: number,
- *   id: string
- * }} Goal
+ * @typedef {import('ppppp-goals').Goal} Goal
+ * @typedef {import('./range').Range} Range
+ * @typedef {string} MsgID
  */
 
+/**
+ * @param {Iterable<unknown>} iter
+ */
 function countIter(iter) {
   let count = 0
   for (const _ of iter) count++
@@ -21,12 +23,18 @@ function countIter(iter) {
 }
 
 class Algorithm {
+  /** @type {{ db: PPPPPDB }} */
   #peer
 
+  /** @param {{ db: PPPPPDB }} peer */
   constructor(peer) {
     this.#peer = peer
   }
 
+  /**
+   * @param {string} rootID
+   * @returns {Range}
+   */
   haveRange(rootID) {
     const rootMsg = this.#peer.db.get(rootID)
     if (!rootMsg) return EMPTY_RANGE
@@ -91,15 +99,23 @@ class Algorithm {
   wantRange(localHave, remoteHave, goal) {
     if (!goal) return EMPTY_RANGE
     if (isEmptyRange(remoteHave)) return EMPTY_RANGE
-    if (goal.type === 'all') {
+    if (goal.type === 'all' || goal.type === 'set' || goal.type === 'record') {
       return this.#wantAllRange(localHave, remoteHave)
     } else if (goal.type === 'newest') {
       return this.#wantNewestRange(localHave, remoteHave, goal.count)
     } else if (goal.type === 'oldest') {
       return this.#wantOldestRange(localHave, remoteHave, goal.count)
     }
+    return EMPTY_RANGE
   }
 
+  /**
+   * @param {string} rootID
+   * @param {number} round
+   * @param {Range} range
+   * @param {Iterable<string>} extraIds
+   * @returns {JSON}
+   */
   bloomFor(rootID, round, range, extraIds = []) {
     const filterSize =
       (isEmptyRange(range) ? 2 : estimateMsgCount(range)) + countIter(extraIds)
@@ -115,6 +131,13 @@ class Algorithm {
     return filter.saveAsJSON()
   }
 
+  /**
+   * @param {string} rootID
+   * @param {number} round
+   * @param {Range} range
+   * @param {JSON} remoteBloomJSON
+   * @returns
+   */
   msgsMissing(rootID, round, range, remoteBloomJSON) {
     if (isEmptyRange(range)) return []
     const remoteFilter = BloomFilter.fromJSON(remoteBloomJSON)
@@ -128,6 +151,10 @@ class Algorithm {
     return missing
   }
 
+  /**
+   * @param {string} rootID
+   * @param {Range} range
+   */
   *yieldMsgsIn(rootID, range) {
     const [minDepth, maxDepth] = range
     const rootMsg = this.#peer.db.get(rootID)
@@ -145,6 +172,10 @@ class Algorithm {
     }
   }
 
+  /**
+   * @param {string} rootID
+   * @param {number} count
+   */
   async pruneNewest(rootID, count) {
     const tangle = this.#peer.db.getTangle(rootID)
     const sorted = tangle.topoSort()
@@ -204,11 +235,15 @@ class Algorithm {
     // TODO: Simulate adding this whole tangle, and check if it's valid
 
     // Add new messages
-    // TODO: optimize perf, avoiding await / try / catch
+    const doneAdding = multicb({ pluck: 1 })
     for (const msg of validNewMsgs) {
-      try {
-        await p(this.#peer.db.add)(msg, rootID)
-      } catch {}
+      this.#peer.db.add(msg, rootID, doneAdding())
+    }
+    try {
+      await p(doneAdding)()
+    } catch (err) {
+      // TODO:
+      // debug('commit failed %o', err)
     }
 
     if (goal.type === 'newest') {
@@ -222,7 +257,7 @@ class Algorithm {
   /**
    * @param {string} rootID
    * @param {Set<string>} msgIDs
-   * @returns
+   * @returns {Array<Msg>}
    */
   getTangleSlice(rootID, msgIDs) {
     if (msgIDs.size === 0) return []
@@ -235,11 +270,14 @@ class Algorithm {
         break
       }
     }
+    if (oldestMsgID === null) {
+      throw new Error('No common msgID found in tangle given inputs')
+    }
     const { erasables } = tangle.getDeletablesAndErasables(oldestMsgID)
 
     const msgs = []
     for (const msgID of sorted) {
-      let isErasable = erasables.includes(msgID)
+      let isErasable = erasables.has(msgID)
       if (!msgIDs.has(msgID) && !isErasable) continue
       const msg = this.#peer.db.get(msgID)
       if (!msg) continue
diff --git a/lib/index.js b/lib/index.js
index 3791ccd..ee19016 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,16 +1,54 @@
-const toPull = require('push-stream-to-pull-stream')
+// @ts-ignore
+const toPull = require('push-stream-to-pull-stream') // @ts-ignore
+const getSeverity = require('ssb-network-errors')
 const pull = require('pull-stream')
 const makeDebug = require('debug')
-const getSeverity = require('ssb-network-errors')
 const Algorithm = require('./algorithm')
 const SyncStream = require('./stream')
 
+/**
+ * @typedef {ReturnType<import('ppppp-goals').init>} PPPPPGoal
+ * @typedef {ReturnType<import('ppppp-db').init>} PPPPPDB
+ * @typedef {import('node:events').EventEmitter} Emitter
+ * @typedef {(cb: (err: Error) => void) => import('pull-stream').Duplex<unknown, unknown>} GetDuplex
+ * @typedef {{ pubkey: string }} SHSE
+ */
+
+/**
+ * @param {Error} err
+ * @param {string} namespace
+ * @param {string} methodName
+ */
 function isMuxrpcMissingError(err, namespace, methodName) {
   const jsErrorMessage = `method:${namespace},${methodName} is not in list of allowed methods`
   const goErrorMessage = `muxrpc: no such command: ${namespace}.${methodName}`
   return err.message === jsErrorMessage || err.message === goErrorMessage
 }
 
+/**
+ * @param {{ db: PPPPPDB | null }} peer
+ * @returns {asserts peer is { db: PPPPPDB }}
+ */
+function assertDBExists(peer) {
+  if (!peer.db) throw new Error('tangleSync requires ppppp-db plugin')
+}
+
+/**
+ * @param {{ goals: PPPPPGoal | null }} peer
+ * @returns {asserts peer is { goals: PPPPPGoal }}
+ */
+function assertGoalsExists(peer) {
+  if (!peer.goals) throw new Error('tangleSync requires ppppp-goals plugin')
+}
+
+/**
+ * @param {{ shse: SHSE | null }} peer
+ * @returns {asserts peer is { shse: SHSE }}
+ */
+function assertSHSEExists(peer) {
+  if (!peer.shse) throw new Error('tangleSync requires secret-handshake-ext')
+}
+
 module.exports = {
   name: 'tangleSync',
   manifest: {
@@ -22,15 +60,31 @@ module.exports = {
       allow: ['connect'],
     },
   },
+
+  /**
+   * @param {Emitter & {
+   *   db: PPPPPDB | null,
+   *   goals: PPPPPGoal | null,
+   *   shse: SHSE | null
+   * }} peer
+   * @param {unknown} config
+   */
   init(peer, config) {
-    if (!peer.goals) {
-      throw new Error('tangleSync requires the goals plugin')
-    }
+    assertDBExists(peer)
+    assertGoalsExists(peer)
+    assertSHSEExists(peer)
     const debug = makeDebug(`ppppp:tangleSync`)
     const algo = new Algorithm(peer)
 
-    const streams = []
+    const streams = /** @type {Array<SyncStream>} */ ([])
+
+    /**
+     * @param {string} remoteId
+     * @param {boolean} iamClient
+     */
     function createStream(remoteId, iamClient) {
+      assertSHSEExists(peer)
+      assertGoalsExists(peer)
       // prettier-ignore
       debug('Opening a stream with remote %s %s', iamClient ? 'server' : 'client', remoteId)
       const stream = new SyncStream(peer.shse.pubkey, debug, peer.goals, algo)
@@ -38,12 +92,17 @@ module.exports = {
       return stream
     }
 
-    peer.on('rpc:connect', function onSyncRPCConnect(rpc, iamClient) {
-      if (rpc.shse.pubkey === peer.shse.pubkey) return // local client connecting to local server
+    /**
+     * @param {{ shse: SHSE, tangleSync: { connect: GetDuplex } }} rpc
+     * @param {boolean} iamClient
+     */
+    function onSyncRPCConnect(rpc, iamClient) {
+      assertSHSEExists(peer)
+      if (rpc.shse.pubkey === peer.shse.pubkey) return // connecting to myself
       if (!iamClient) return
-      const local = toPull.duplex(createStream(rpc.id, true))
+      const local = toPull.duplex(createStream(rpc.shse.pubkey, true))
 
-      let abort
+      let abort = /** @type {CallableFunction | null} */ (null)
       const remote = rpc.tangleSync.connect((networkError) => {
         if (networkError && getSeverity(networkError) >= 3) {
           if (isMuxrpcMissingError(networkError, 'tangleSync', 'connect')) {
@@ -57,11 +116,17 @@ module.exports = {
         }
       })
       abort = pull(local, remote, local)
-    })
+    }
+    peer.on('rpc:connect', onSyncRPCConnect)
 
+    /**
+     * @this {{id: string}}
+     */
     function connect() {
       // `this` refers to the remote peer who called this muxrpc API
       return toPull.duplex(createStream(this.id, false))
+      // TODO: fix muxrpc to replace this.id with this.shse.pubkey.
+      // this.id comes from muxrpc, not secret-stack
     }
 
     function initiate() {
diff --git a/lib/range.js b/lib/range.js
index 0f8aec8..2a6bc7d 100644
--- a/lib/range.js
+++ b/lib/range.js
@@ -23,7 +23,7 @@ function estimateMsgCount(range) {
   else return estimate
 }
 
-const EMPTY_RANGE = [1, 0]
+const EMPTY_RANGE = /** @type {Range} */ ([1, 0])
 
 module.exports = {
   isEmptyRange,
diff --git a/lib/stream.js b/lib/stream.js
index 0a2bdb6..08d643b 100644
--- a/lib/stream.js
+++ b/lib/stream.js
@@ -1,28 +1,45 @@
+// @ts-ignore
 const Pipeable = require('push-stream/pipeable')
 const { isEmptyRange } = require('./range')
 
 /**
+ * @typedef {ReturnType<import('ppppp-goals').init>} PPPPPGoals
+ * @typedef {import('ppppp-db/msg-v3').Msg} Msg
+ * @typedef {import('./range').Range} Range
+ * @typedef {import('./algorithm')} Algorithm
  * @typedef {{
  *   type: 'all' | 'newest' | 'oldest',
  *   count: number,
  *   id: string
  * }} Goal
+ * @typedef {string} MsgID
+ * @typedef {{id: string}} WithId
+ * @typedef {WithId & {phase: 0, payload?: undefined}} Data0
+ * @typedef {WithId & {phase: 1, payload: Range}} Data1
+ * @typedef {WithId & {phase: 2, payload: { haveRange: Range, wantRange: Range }}} Data2
+ * @typedef {WithId & {phase: 3, payload: { wantRange: Range, bloom: JSON }}} Data3
+ * @typedef {WithId & {phase: 4 | 5 | 6 | 7, payload: { msgIDs: Array<MsgID>, bloom: JSON }}} Data4567
+ * @typedef {WithId & {phase: 8, payload: { msgs: Array<Msg>, bloom: JSON }}} Data8
+ * @typedef {WithId & {phase: 9, payload: Array<Msg>}} Data9
+ * @typedef {Data0 | Data1 | Data2 | Data3 | Data4567 | Data8 | Data9} Data
  */
 
 class SyncStream extends Pipeable {
   #myId
-  #debug
+
+  /** @type {Algorithm} */
   #algo
 
+  /** @type {CallableFunction} */
+  #debug
+
   /** Set of tangleId
    * @type {Set<string>} */
   #requested
 
   /** tangleId => goal
-   * @type {{
-   *   getByID(id: string): Goal | null,
-   *   list(): IterableIterator<Goal>,
-   * }} */
+   * @type {PPPPPGoals}
+   */
   #goals
 
   /**
@@ -61,10 +78,18 @@ class SyncStream extends Pipeable {
    */
   #sendableMsgs
 
+  /**
+   *
+   * @param {string} localId
+   * @param {CallableFunction} debug
+   * @param {PPPPPGoals} goals
+   * @param {Algorithm} algo
+   */
   constructor(localId, debug, goals, algo) {
     super()
     this.paused = false // TODO: should we start as paused=true?
     this.ended = false
+    /** @type {any} */
     this.source = this.sink = null
     this.#myId = localId.slice(0, 6)
     this.#debug = debug
@@ -90,22 +115,33 @@ class SyncStream extends Pipeable {
     return this.sink && !this.sink.paused && !this.ended
   }
 
-  #updateSendableMsgs(id, msgs) {
+  /**
+   * @param {string} id
+   * @param {Array<MsgID>} msgIDs
+   */
+  #updateSendableMsgs(id, msgIDs) {
     const set = this.#sendableMsgs.get(id) ?? new Set()
-    for (const msg of msgs) {
-      set.add(msg)
+    for (const msgID of msgIDs) {
+      set.add(msgID)
     }
     this.#sendableMsgs.set(id, set)
   }
 
-  #updateReceivableMsgs(id, msgs) {
+  /**
+   * @param {string} id
+   * @param {Array<string>} msgIDs
+   */
+  #updateReceivableMsgs(id, msgIDs) {
     const set = this.#receivableMsgs.get(id) ?? new Set()
-    for (const msg of msgs) {
-      set.add(msg)
+    for (const msgID of msgIDs) {
+      set.add(msgID)
     }
     this.#receivableMsgs.set(id, set)
   }
 
+  /**
+   * @param {string} id
+   */
   #sendLocalHave(id) {
     const localHaveRange = this.#algo.haveRange(id)
     this.#localHave.set(id, localHaveRange)
@@ -114,11 +150,15 @@ class SyncStream extends Pipeable {
     this.sink.write({ id, phase: 1, payload: localHaveRange })
   }
 
+  /**
+   * @param {string} id
+   * @param {Range} remoteHaveRange
+   */
   #sendLocalHaveAndWant(id, remoteHaveRange) {
     // prettier-ignore
     this.#debug('%s Stream  IN1:  got remote have-range %o for %s', this.#myId, remoteHaveRange, id)
     this.#remoteHave.set(id, remoteHaveRange)
-    const goal = this.#goals.getByID(id)
+    const goal = this.#goals.get(id)
     const haveRange = this.#algo.haveRange(id)
     const wantRange = this.#algo.wantRange(haveRange, remoteHaveRange, goal)
     this.#localHave.set(id, haveRange)
@@ -128,13 +168,19 @@ class SyncStream extends Pipeable {
     this.sink.write({ id, phase: 2, payload: { haveRange, wantRange } })
   }
 
+  /**
+   * @param {string} id
+   * @param {Range} remoteHaveRange
+   * @param {Range} remoteWantRange
+   */
   #sendLocalWantAndInitBloom(id, remoteHaveRange, remoteWantRange) {
     // prettier-ignore
     this.#debug('%s Stream  IN2:  got remote have-range %o and want-range %o for %s', this.#myId, remoteHaveRange, remoteWantRange, id)
     this.#remoteHave.set(id, remoteHaveRange)
     this.#remoteWant.set(id, remoteWantRange)
-    const goal = this.#goals.getByID(id)
+    const goal = this.#goals.get(id)
     const haveRange = this.#localHave.get(id)
+    if (!haveRange) throw new Error('local have-range not set')
     const wantRange = this.#algo.wantRange(haveRange, remoteHaveRange, goal)
     this.#localWant.set(id, wantRange)
     const localBloom0 = this.#algo.bloomFor(id, 0, wantRange)
@@ -147,6 +193,11 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT3: send local want-range %o and bloom round 0 for %s', this.#myId, wantRange, id)
   }
 
+  /**
+   * @param {string} id
+   * @param {Range} remoteWantRange
+   * @param {JSON} remoteBloom
+   */
   #sendInitBloomRes(id, remoteWantRange, remoteBloom) {
     // prettier-ignore
     this.#debug('%s Stream  IN3:  got remote want-range %o and bloom round 0 for %s', this.#myId, remoteWantRange, id)
@@ -159,6 +210,7 @@ class SyncStream extends Pipeable {
     )
     this.#updateSendableMsgs(id, msgIDsForThem)
     const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     const localBloom = this.#algo.bloomFor(id, 0, localWantRange)
     this.sink.write({
       id,
@@ -169,10 +221,18 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT4: send bloom round 0 plus msgIDs in %s: %o', this.#myId, id, msgIDsForThem)
   }
 
+  /**
+   * @param {string} id
+   * @param {number} phase
+   * @param {number} round
+   * @param {JSON} remoteBloom
+   * @param {Array<MsgID>} msgIDsForMe
+   */
   #sendBloomReq(id, phase, round, remoteBloom, msgIDsForMe) {
     // prettier-ignore
     this.#debug('%s Stream  IN%s:  got bloom round %s plus msgIDs in %s: %o', this.#myId, phase-1, round-1, id, msgIDsForMe)
     const remoteWantRange = this.#remoteWant.get(id)
+    if (!remoteWantRange) throw new Error('remote want-range not set')
     this.#updateReceivableMsgs(id, msgIDsForMe)
     const msgIDsForThem = this.#algo.msgsMissing(
       id,
@@ -183,6 +243,7 @@ class SyncStream extends Pipeable {
     this.#updateSendableMsgs(id, msgIDsForThem)
     const extras = this.#receivableMsgs.get(id)
     const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     const localBloom = this.#algo.bloomFor(id, round, localWantRange, extras)
     this.sink.write({
       id,
@@ -193,10 +254,18 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT%s: send bloom round %s plus msgIDs in %s: %o', this.#myId, phase, round, id, msgIDsForThem)
   }
 
+  /**
+   * @param {string} id
+   * @param {number} phase
+   * @param {number} round
+   * @param {JSON} remoteBloom
+   * @param {Array<MsgID>} msgIDsForMe
+   */
   #sendBloomRes(id, phase, round, remoteBloom, msgIDsForMe) {
     // prettier-ignore
     this.#debug('%s Stream  IN%s:  got bloom round %s plus msgIDs in %s: %o', this.#myId, phase-1, round, id, msgIDsForMe)
     const remoteWantRange = this.#remoteWant.get(id)
+    if (!remoteWantRange) throw new Error('remote want-range not set')
     this.#updateReceivableMsgs(id, msgIDsForMe)
     const msgIDsForThem = this.#algo.msgsMissing(
       id,
@@ -207,6 +276,7 @@ class SyncStream extends Pipeable {
     this.#updateSendableMsgs(id, msgIDsForThem)
     const extras = this.#receivableMsgs.get(id)
     const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     const localBloom = this.#algo.bloomFor(id, round, localWantRange, extras)
     this.sink.write({
       id,
@@ -217,10 +287,17 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT%s: send bloom round %s plus msgIDs in %s: %o', this.#myId, phase, round, id, msgIDsForThem)
   }
 
+  /**
+   * @param {string} id
+   * @param {number} round
+   * @param {JSON} remoteBloom
+   * @param {Array<MsgID>} msgIDsForMe
+   */
   #sendMissingMsgsReq(id, round, remoteBloom, msgIDsForMe) {
     // prettier-ignore
     this.#debug('%s Stream  IN7:  got bloom round %s plus msgIDs in %s: %o', this.#myId, round, id, msgIDsForMe)
     const remoteWantRange = this.#remoteWant.get(id)
+    if (!remoteWantRange) throw new Error('remote want-range not set')
     this.#updateReceivableMsgs(id, msgIDsForMe)
     const msgIDsForThem = this.#algo.msgsMissing(
       id,
@@ -233,6 +310,7 @@ class SyncStream extends Pipeable {
     const msgs = this.#algo.getTangleSlice(id, msgIDs)
     const extras = this.#receivableMsgs.get(id)
     const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     const localBloom = this.#algo.bloomFor(id, round, localWantRange, extras)
     this.sink.write({
       id,
@@ -243,10 +321,17 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT8: send bloom round %s plus %s msgs in %s', this.#myId, round, msgs.length, id)
   }
 
+  /**
+   * @param {string} id
+   * @param {number} round
+   * @param {JSON} remoteBloom
+   * @param {Array<Msg>} msgsForMe
+   */
   #sendMissingMsgsRes(id, round, remoteBloom, msgsForMe) {
     // prettier-ignore
     this.#debug('%s Stream  IN8:  got bloom round %s plus %s msgs in %s', this.#myId, round, msgsForMe.length, id)
     const remoteWantRange = this.#remoteWant.get(id)
+    if (!remoteWantRange) throw new Error('remote want-range not set')
     const msgIDsForThem = this.#algo.msgsMissing(
       id,
       round,
@@ -260,8 +345,10 @@ class SyncStream extends Pipeable {
     this.#debug('%s Stream OUT9: send %s msgs in %s', this.#myId, msgs.length, id)
     this.sink.write({ id, phase: 9, payload: msgs })
 
-    const goal = this.#goals.getByID(id)
-    const localWant = this.#localWant.get(id)
+    const goal = this.#goals.get(id)
+    if (!goal) throw new Error(`No goal found for "${id}"`)
+    const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     this.#requested.delete(id)
     this.#localHave.delete(id)
     this.#localWant.delete(id)
@@ -271,19 +358,26 @@ class SyncStream extends Pipeable {
     this.#sendableMsgs.delete(id)
     if (msgsForMe.length === 0) return
     try {
-      this.#algo.commit(id, msgsForMe, goal, localWant)
+      this.#algo.commit(id, msgsForMe, goal, localWantRange)
     } catch (err) {
       // prettier-ignore
       this.#debug('%s Stream could not commit received messages, because: %s', this.#myId, err)
     }
   }
 
+  /**
+   * @param {string} id
+   * @param {Array<Msg>} msgsForMe
+   * @returns
+   */
   #consumeMissingMsgs(id, msgsForMe) {
     // prettier-ignore
     this.#debug('%s Stream  IN9:  got %s msgs in %s', this.#myId, msgsForMe.length, id)
 
-    const goal = this.#goals.getByID(id)
-    const localWant = this.#localWant.get(id)
+    const goal = this.#goals.get(id)
+    if (!goal) throw new Error(`No goal found for "${id}"`)
+    const localWantRange = this.#localWant.get(id)
+    if (!localWantRange) throw new Error('local want-range not set')
     this.#requested.delete(id)
     this.#localHave.delete(id)
     this.#localWant.delete(id)
@@ -293,13 +387,17 @@ class SyncStream extends Pipeable {
     this.#sendableMsgs.delete(id)
     if (msgsForMe.length === 0) return
     try {
-      this.#algo.commit(id, msgsForMe, goal, localWant)
+      this.#algo.commit(id, msgsForMe, goal, localWantRange)
     } catch (err) {
       // prettier-ignore
       this.#debug('%s Stream could not commit received messages, because: %s', this.#myId, err)
     }
   }
 
+  /**
+   * @param {string} id
+   * @param {Range} remoteWantRange
+   */
   #sendMsgsInRemoteWant(id, remoteWantRange) {
     const msgs = []
     for (const msg of this.#algo.yieldMsgsIn(id, remoteWantRange)) {
@@ -310,7 +408,7 @@ class SyncStream extends Pipeable {
     this.sink.write({ id, phase: 9, payload: msgs })
   }
 
-  // as a source
+  // source method
   resume() {
     if (!this.sink || this.sink.paused) return
 
@@ -320,7 +418,10 @@ class SyncStream extends Pipeable {
     }
   }
 
-  // as a sink
+  /**
+   * sink method
+   * @param {Data} data
+   */
   write(data) {
     const { id, phase, payload } = data
 
@@ -380,14 +481,20 @@ class SyncStream extends Pipeable {
     this.#debug('Stream IN: unknown %o', data)
   }
 
-  // as a source
+  /**
+   * source method
+   * @param {Error} err
+   */
   abort(err) {
     this.ended = true
     if (this.source && !this.source.ended) this.source.abort(err)
     if (this.sink && !this.sink.ended) this.sink.end(err)
   }
 
-  // as a sink
+  /**
+   * sink method
+   * @param {Error} err
+   */
   end(err) {
     this.ended = true
     if (this.source && !this.source.ended) this.source.abort(err)
diff --git a/package.json b/package.json
index da799fe..2110c65 100644
--- a/package.json
+++ b/package.json
@@ -26,12 +26,17 @@
   "dependencies": {
     "bloom-filters": "^3.0.0",
     "debug": "^4.3.4",
+    "multicb": "1.2.2",
+    "promisify-4loc": "^1.0.0",
     "pull-stream": "^3.7.0",
     "push-stream": "^11.2.0",
     "push-stream-to-pull-stream": "^1.0.5",
     "ssb-network-errors": "^1.0.1"
   },
   "devDependencies": {
+    "@types/debug": "^4.1.9",
+    "@types/pull-stream": "3.6.3",
+    "@types/node": "16.x",
     "bs58": "^5.0.0",
     "c8": "7",
     "ppppp-db": "github:staltz/ppppp-db",
@@ -43,10 +48,14 @@
     "rimraf": "^4.4.0",
     "secret-stack": "~7.1.0",
     "secret-handshake-ext": "^0.0.8",
-    "ssb-box": "^1.0.1"
+    "ssb-box": "^1.0.1",
+    "typescript": "^5.1.3"
   },
   "scripts": {
-    "test": "node --test",
+    "clean-check": "tsc --build --clean",
+    "prepublishOnly": "npm run clean-check && tsc --build",
+    "postpublish": "npm run clean-check",
+    "test": "npm run clean-check && node --test",
     "format-code": "prettier --write \"(lib|test)/**/*.js\"",
     "format-code-staged": "pretty-quick --staged --pattern \"(lib|test)/**/*.js\"",
     "coverage": "c8 --reporter=lcov npm run test"
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..bd2acd5
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,16 @@
+{
+  "include": ["lib/**/*.js"],
+  "exclude": ["coverage/", "node_modules/", "test/"],
+  "compilerOptions": {
+    "checkJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "exactOptionalPropertyTypes": true,
+    "forceConsistentCasingInFileNames": true,
+    "lib": ["es2022", "dom"],
+    "module": "node16",
+    "skipLibCheck": true,
+    "strict": true,
+    "target": "es2021"
+  }
+}
\ No newline at end of file