diff --git a/lib/index.js b/lib/index.js
index f2939e4..468ee2f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,8 +1,132 @@
-const makeDebug = require('debug')
+/**
+ * @typedef {ReturnType<import('ppppp-db').init>} PPPPPDB
+ * @typedef {ReturnType<import('ppppp-goals').init>} PPPPPGoal
+ * @typedef {ReturnType<import('ppppp-set').init>} PPPPPSet
+ * @typedef {ReturnType<import('ppppp-sync').init>} PPPPPSync
+ * @typedef {ReturnType<import('ppppp-gc').init>} PPPPPGC
+ * @typedef {[Array<string>, Array<string>]} Rules
+ * @typedef {{
+ *   db:PPPPPDB | null,
+ *   goals: PPPPPGoal | null,
+ *   set: PPPPPSet | null,
+ *   sync: PPPPPSync | null,
+ *   gc: PPPPPGC | null,
+ * }} UnknownPeer
+ */
 
+/**
+ * @param {{ db: PPPPPDB | null }} peer
+ * @returns {asserts peer is { db: PPPPPDB }}
+ */
+function assertDBPlugin(peer) {
+  if (!peer.db) throw new Error('conductor plugin needs ppppp-db plugin')
+}
+
+/**
+ * @param {{ goals: PPPPPGoal | null }} peer
+ * @returns {asserts peer is { goals: PPPPPGoal }}
+ */
+function assertGoalsPlugin(peer) {
+  if (!peer.goals) throw new Error('conductor plugin needs ppppp-goals plugin')
+}
+
+/**
+ * @param {{ set: PPPPPSet | null }} peer
+ * @returns {asserts peer is { set: PPPPPSet }}
+ */
+function assertSetPlugin(peer) {
+  if (!peer.set) throw new Error('conductor plugin needs ppppp-set plugin')
+}
+
+/**
+ * @param {{ gc: PPPPPGC | null }} peer
+ * @returns {asserts peer is { gc: PPPPPGC }}
+ */
+function assertGCPlugin(peer) {
+  if (!peer.gc) throw new Error('conductor plugin needs ppppp-gc plugin')
+}
+
+/**
+ * @param {{ sync: PPPPPSync | null }} peer
+ * @returns {asserts peer is { sync: PPPPPSync }}
+ */
+function assertSyncPlugin(peer) {
+  if (!peer.sync) throw new Error('conductor plugin needs ppppp-sync plugin')
+}
+
+/**
+ * @param {UnknownPeer} peer
+ * @param {unknown} config
+ */
 function initConductor(peer, config) {
+  assertDBPlugin(peer)
+  assertGoalsPlugin(peer)
+  assertSetPlugin(peer)
+  assertGCPlugin(peer)
+  assertSyncPlugin(peer)
+
+  /**
+   * Set replication goals for various tangles of an account:
+   * - Account tangle
+   * - Follow tangle (a Set)
+   * - Each tangle in the rule
+   *
+   * The "rule" is just a list of domains of feeds.
+   * @param {string} accountID
+   * @param {Array<string>} rule
+   */
+  function setupAccountGoals(accountID, rule) {
+    assertDBPlugin(peer)
+    assertSetPlugin(peer)
+    assertGoalsPlugin(peer)
+
+    peer.goals.set(accountID, 'all')
+
+    const followDomain = peer.set.getDomain('follow')
+    const followFeedID = peer.db.feed.getID(accountID, followDomain)
+    peer.goals.set(followFeedID, 'set')
+
+    for (const domain of rule) {
+      const feedID = peer.db.feed.getID(accountID, domain)
+      peer.goals.set(feedID, 'all') // TODO better goal?
+    }
+  }
+
+  /**
+   * Starts automatic sync and garbage collection.
+   * Assumes that PPPPP Set has been loaded with the same accountID.
+   *
+   * @param {string} myID
+   * @param {Rules} rules
+   * @param {number} maxBytes
+   */
+  function start(myID, rules, maxBytes) {
+    assertDBPlugin(peer)
+    assertSetPlugin(peer)
+    assertGoalsPlugin(peer)
+    assertGCPlugin(peer)
+    assertSyncPlugin(peer)
+
+    const [myRule, theirRule] = rules
+
+    // TODO: Figure out goals for each tangle, and sizes according to maxLogBytes
+    // TODO: Figure out ghost spans for dicts and sets
+
+    setupAccountGoals(myID, myRule)
+
+    // TODO: watch the set for live updates, on add, syncAccount()
+    // TODO: watch the set for live updates, on remove, forgetAccount()
+    const followedAccounts = peer.set.values('follow')
+    for (const theirID of followedAccounts) {
+      setupAccountGoals(theirID, theirRule)
+    }
+
+    peer.gc.start(maxBytes)
+    peer.sync.start()
+  }
 
   return {
+    start,
   }
 }
 
diff --git a/test/follow-feeds.test.js b/test/follow-feeds.test.js
new file mode 100644
index 0000000..4a6daac
--- /dev/null
+++ b/test/follow-feeds.test.js
@@ -0,0 +1,86 @@
+const test = require('node:test')
+const assert = require('node:assert')
+const p = require('node:util').promisify
+const { createPeer } = require('./util')
+
+function getTexts(msgs) {
+  return msgs.filter((msg) => msg.data?.text).map((msg) => msg.data.text)
+}
+
+test('Replicate selected feeds of followed accounts', async (t) => {
+  // Alice
+  const alice = createPeer({ name: 'alice' })
+  await alice.db.loaded()
+  // Alice creates her own account
+  const aliceID = await p(alice.db.account.create)({
+    subdomain: 'account',
+    _nonce: 'alice',
+  })
+  await p(alice.set.load)(aliceID)
+  // Alice creates a feed of posts
+  for (let i = 0; i < 5; i++) {
+    await p(alice.db.feed.publish)({
+      account: aliceID,
+      domain: 'post',
+      data: { text: 'A' + i },
+    })
+  }
+
+  // Bob
+  const bob = createPeer({ name: 'bob' })
+  await bob.db.loaded()
+  // Bob creates his own account
+  const bobID = await p(bob.db.account.create)({
+    subdomain: 'account',
+    _nonce: 'bob',
+  })
+  await p(bob.set.load)(bobID)
+  // Bob creates a feed of posts
+  for (let i = 0; i < 5; i++) {
+    await p(bob.db.feed.publish)({
+      account: bobID,
+      domain: 'post',
+      data: { text: 'B' + i },
+    })
+  }
+
+  // Carol
+  const carol = createPeer({ name: 'carol' })
+  await carol.db.loaded()
+  // Carol creates her own account
+  const carolID = await p(carol.db.account.create)({
+    subdomain: 'account',
+    _nonce: 'carol',
+  })
+  await p(carol.set.load)(bobID)
+  // Carol creates a feed of posts
+  for (let i = 0; i < 5; i++) {
+    await p(carol.db.feed.publish)({
+      account: carolID,
+      domain: 'post',
+      data: { text: 'C' + i },
+    })
+  }
+
+  // Alice follows Bob, but not Carol
+  assert(await p(alice.set.add)('follow', bobID), 'alice follows bob')
+
+  alice.conductor.start(aliceID, [['post'], ['post']], 64_000_000)
+  bob.conductor.start(bobID, [['post'], ['post']], 64_000_000)
+
+  const aliceDialingBob = await p(alice.connect)(bob.getAddress())
+  const aliceDialingCarol = await p(alice.connect)(carol.getAddress())
+  await p(setTimeout)(1000)
+
+  assert.deepEqual(
+    getTexts([...alice.db.msgs()]),
+    ['A0', 'A1', 'A2', 'A3', 'A4', /*    */ 'B0', 'B1', 'B2', 'B3', 'B4'],
+    'alice has alice and bob posts'
+  )
+
+  await p(aliceDialingBob.close)(true)
+  await p(aliceDialingCarol.close)(true)
+  await p(alice.close)(true)
+  await p(bob.close)(true)
+  await p(carol.close)(true)
+})
diff --git a/test/util.js b/test/util.js
new file mode 100644
index 0000000..4347934
--- /dev/null
+++ b/test/util.js
@@ -0,0 +1,43 @@
+const os = require('node:os')
+const path = require('node:path')
+const rimraf = require('rimraf')
+const caps = require('ppppp-caps')
+const Keypair = require('ppppp-keypair')
+
+function createPeer(opts) {
+  if (opts.name) {
+    const tmp = os.tmpdir()
+    const now = Date.now()
+    opts.db ??= {path: path.join(tmp, `ppppp-conductor-${opts.name}-${now}`)}
+    opts.keypair ??= Keypair.generate('ed25519', opts.name)
+    opts.name = undefined
+  }
+  if (!opts.db.path) throw new Error('need opts.db.path in createPeer()')
+  if (!opts.keypair) throw new Error('need opts.keypair in createPeer()')
+
+  rimraf.sync(opts.db.path)
+  return require('secret-stack/bare')()
+    .use(require('secret-stack/plugins/net'))
+    .use(require('secret-handshake-ext/secret-stack'))
+    .use(require('ppppp-db'))
+    .use(require('ssb-box'))
+    .use(require('ppppp-set'))
+    .use(require('ppppp-goals'))
+    .use(require('ppppp-sync'))
+    .use(require('ppppp-gc'))
+    .use(require('../lib'))
+    .call(null, {
+      caps,
+      connections: {
+        incoming: {
+          net: [{ scope: 'device', transform: 'shse', port: null }],
+        },
+        outgoing: {
+          net: [{ transform: 'shse' }],
+        },
+      },
+      ...opts,
+    })
+}
+
+module.exports = { createPeer }