diff --git a/brain/brain.go b/brain/brain.go
index 01ac2b1..634e28b 100644
--- a/brain/brain.go
+++ b/brain/brain.go
@@ -1,15 +1,51 @@
 package brain
 
 import (
+	"context"
+
 	"github.com/zephyrtronium/robot/message"
 	"github.com/zephyrtronium/robot/userhash"
 )
 
-// Brain is a combined [Learner] and [Speaker].
-type Brain interface {
-	Learner
-	Speaker
+// Interface is a store of learned messages which can reproduce them by parts.
+//
+// It must be safe to call all methods of a brain concurrently with each other.
+type Interface interface {
+	// Learn records a set of tuples.
+	//
+	// One tuple has an empty prefix to denote the start of the message, and
+	// a different tuple has the empty string as its suffix to denote the end
+	// of the message. The positions of each in the argument are not guaranteed.
+	//
+	// Each tuple's prefix has entropy reduction transformations applied.
+	//
+	// Tuples in the argument may share storage for prefixes.
+	Learn(ctx context.Context, tag string, msg *Message, tuples []Tuple) error
+
+	// Speak generates a full message and appends it to w.
+	//
+	// The prompt is in reverse order and has entropy reduction applied.
+	Speak(ctx context.Context, tag string, prompt []string, w *Builder) error
+
+	// Forget forgets everything learned from a single given message.
+	// If nothing has been learned from the message, it must prevent anything
+	// from being learned from a message with that ID.
+	Forget(ctx context.Context, tag, id string) error
+
+	// Recall reads out messages the brain knows.
+	// At minimum, the message ID and text of each message must be retrieved;
+	// other fields may be filled if they are available.
+	//
+	// Repeated calls using the pagination token returned from the previous
+	// must yield every message that the brain had recorded at the time of the
+	// first call exactly once. Messages learned after the first call of an
+	// enumeration are read at most once.
+	//
+	// The first call of an enumeration uses an empty pagination token as input.
+	// If the returned pagination token is empty, it is interpreted as the end
+	// of the enumeration.
+	Recall(ctx context.Context, tag, page string, out []Message) (n int, next string, err error)
 }
 
-// Message is the message type used by a [Brain].
+// Message is the message type used by a [Interface].
 type Message = message.Received[userhash.Hash]
diff --git a/brain/braintest/bench.go b/brain/braintest/bench.go
index ee0ba1f..ef704ab 100644
--- a/brain/braintest/bench.go
+++ b/brain/braintest/bench.go
@@ -20,7 +20,7 @@ func randid() string {
 
 // BenchLearn runs benchmarks on the brain's speed with recording new tuples.
 // The learner returned by new must be safe for concurrent use.
-func BenchLearn(ctx context.Context, b *testing.B, new func(ctx context.Context, b *testing.B) brain.Learner, cleanup func(brain.Learner)) {
+func BenchLearn(ctx context.Context, b *testing.B, new func(ctx context.Context, b *testing.B) brain.Interface, cleanup func(brain.Interface)) {
 	b.Run("similar", func(b *testing.B) {
 		l := new(ctx, b)
 		if cleanup != nil {
@@ -95,7 +95,7 @@ func BenchLearn(ctx context.Context, b *testing.B, new func(ctx context.Context,
 
 // BenchSpeak runs benchmarks on a brain's speed with generating messages
 // from tuples. The brain returned by new must be safe for concurrent use.
-func BenchSpeak(ctx context.Context, b *testing.B, new func(ctx context.Context, b *testing.B) brain.Brain, cleanup func(brain.Brain)) {
+func BenchSpeak(ctx context.Context, b *testing.B, new func(ctx context.Context, b *testing.B) brain.Interface, cleanup func(brain.Interface)) {
 	sizes := []int64{1e3, 1e4, 1e5}
 	for _, size := range sizes {
 		b.Run(fmt.Sprintf("similar-new-%d", size), func(b *testing.B) {
diff --git a/brain/braintest/braintest.go b/brain/braintest/braintest.go
index dce841e..65bb38c 100644
--- a/brain/braintest/braintest.go
+++ b/brain/braintest/braintest.go
@@ -16,7 +16,7 @@ import (
 // Test runs the integration test suite against brains produced by new.
 //
 // If a brain cannot be created without error, new should call t.Fatal.
-func Test(ctx context.Context, t *testing.T, new func(context.Context) brain.Brain) {
+func Test(ctx context.Context, t *testing.T, new func(context.Context) brain.Interface) {
 	t.Run("speak", testSpeak(ctx, new(ctx)))
 	t.Run("forgetMessage", testForget(ctx, new(ctx)))
 	t.Run("combinatoric", testCombinatoric(ctx, new(ctx)))
@@ -94,7 +94,7 @@ var messages = [...]struct {
 	},
 }
 
-func learn(ctx context.Context, t *testing.T, br brain.Learner) {
+func learn(ctx context.Context, t *testing.T, br brain.Interface) {
 	t.Helper()
 	for _, m := range messages {
 		msg := brain.Message{ID: m.ID, Sender: m.User, Timestamp: m.Time.UnixMilli(), Text: m.Text}
@@ -104,7 +104,7 @@ func learn(ctx context.Context, t *testing.T, br brain.Learner) {
 	}
 }
 
-func speak(ctx context.Context, t *testing.T, br brain.Speaker, tag, prompt string, iters int) map[string]struct{} {
+func speak(ctx context.Context, t *testing.T, br brain.Interface, tag, prompt string, iters int) map[string]struct{} {
 	t.Helper()
 	got := make(map[string]struct{}, 20)
 	for range iters {
@@ -118,7 +118,7 @@ func speak(ctx context.Context, t *testing.T, br brain.Speaker, tag, prompt stri
 }
 
 // testSpeak tests that a brain can speak what it has learned.
-func testSpeak(ctx context.Context, br brain.Brain) func(t *testing.T) {
+func testSpeak(ctx context.Context, br brain.Interface) func(t *testing.T) {
 	return func(t *testing.T) {
 		learn(ctx, t, br)
 		got := speak(ctx, t, br, "kessoku", "", 2048)
@@ -177,7 +177,7 @@ func testSpeak(ctx context.Context, br brain.Brain) func(t *testing.T) {
 }
 
 // testForget tests that a brain can forget messages by ID.
-func testForget(ctx context.Context, br brain.Brain) func(t *testing.T) {
+func testForget(ctx context.Context, br brain.Interface) func(t *testing.T) {
 	return func(t *testing.T) {
 		learn(ctx, t, br)
 		if err := br.Forget(ctx, "kessoku", messages[0].ID); err != nil {
@@ -229,7 +229,7 @@ func testForget(ctx context.Context, br brain.Brain) func(t *testing.T) {
 
 // testCombinatoric tests that chains can generate even with substantial
 // overlap in learned material.
-func testCombinatoric(ctx context.Context, br brain.Brain) func(t *testing.T) {
+func testCombinatoric(ctx context.Context, br brain.Interface) func(t *testing.T) {
 	return func(t *testing.T) {
 		u := userhash.Hash{2}
 		band := []string{"bocchi", "ryou", "nijika", "kita"}
diff --git a/brain/braintest/braintest_test.go b/brain/braintest/braintest_test.go
index 2c24bfa..156d0ff 100644
--- a/brain/braintest/braintest_test.go
+++ b/brain/braintest/braintest_test.go
@@ -22,7 +22,7 @@ type membrain struct {
 	tms   map[string]map[int64][]string     // map of tags to map of timestamps to ids
 }
 
-var _ brain.Brain = (*membrain)(nil)
+var _ brain.Interface = (*membrain)(nil)
 
 func (m *membrain) Learn(ctx context.Context, tag string, msg *brain.Message, tuples []brain.Tuple) error {
 	m.mu.Lock()
@@ -107,5 +107,5 @@ func (m *membrain) Speak(ctx context.Context, tag string, prompt []string, w *br
 }
 
 func TestTests(t *testing.T) {
-	braintest.Test(context.Background(), t, func(ctx context.Context) brain.Brain { return new(membrain) })
+	braintest.Test(context.Background(), t, func(ctx context.Context) brain.Interface { return new(membrain) })
 }
diff --git a/brain/kvbrain/kvbrain.go b/brain/kvbrain/kvbrain.go
index 1ce2d43..a451a60 100644
--- a/brain/kvbrain/kvbrain.go
+++ b/brain/kvbrain/kvbrain.go
@@ -40,7 +40,7 @@ type Brain struct {
 	past      sync2.Map[string, *past]
 }
 
-var _ brain.Learner = (*Brain)(nil)
+var _ brain.Interface = (*Brain)(nil)
 
 func New(knowledge *badger.DB) *Brain {
 	return &Brain{
diff --git a/brain/kvbrain/kvbrain_test.go b/brain/kvbrain/kvbrain_test.go
index b4e7ffd..fefdbe7 100644
--- a/brain/kvbrain/kvbrain_test.go
+++ b/brain/kvbrain/kvbrain_test.go
@@ -12,7 +12,7 @@ import (
 )
 
 func TestBrain(t *testing.T) {
-	braintest.Test(context.Background(), t, func(ctx context.Context) brain.Brain {
+	braintest.Test(context.Background(), t, func(ctx context.Context) brain.Interface {
 		db, err := badger.Open(badger.DefaultOptions("").WithInMemory(true).WithLogger(nil))
 		if err != nil {
 			t.Fatal(err)
diff --git a/brain/kvbrain/learn_test.go b/brain/kvbrain/learn_test.go
index 9b71d21..6612754 100644
--- a/brain/kvbrain/learn_test.go
+++ b/brain/kvbrain/learn_test.go
@@ -142,14 +142,14 @@ func TestLearn(t *testing.T) {
 }
 
 func BenchmarkLearn(b *testing.B) {
-	new := func(ctx context.Context, b *testing.B) brain.Learner {
+	new := func(ctx context.Context, b *testing.B) brain.Interface {
 		db, err := badger.Open(badger.DefaultOptions(b.TempDir()).WithLogger(nil))
 		if err != nil {
 			b.Fatal(err)
 		}
 		return New(db)
 	}
-	cleanup := func(l brain.Learner) {
+	cleanup := func(l brain.Interface) {
 		br := l.(*Brain)
 		if err := br.knowledge.DropAll(); err != nil {
 			b.Fatal(err)
diff --git a/brain/kvbrain/speak_test.go b/brain/kvbrain/speak_test.go
index 052800b..548c757 100644
--- a/brain/kvbrain/speak_test.go
+++ b/brain/kvbrain/speak_test.go
@@ -157,14 +157,14 @@ func TestSpeak(t *testing.T) {
 }
 
 func BenchmarkSpeak(b *testing.B) {
-	new := func(ctx context.Context, b *testing.B) brain.Brain {
+	new := func(ctx context.Context, b *testing.B) brain.Interface {
 		db, err := badger.Open(badger.DefaultOptions(b.TempDir()).WithLogger(nil).WithCompression(options.None).WithBloomFalsePositive(1.0 / 32).WithNumMemtables(16).WithLevelSizeMultiplier(4))
 		if err != nil {
 			b.Fatal(err)
 		}
 		return New(db)
 	}
-	cleanup := func(l brain.Brain) {
+	cleanup := func(l brain.Interface) {
 		br := l.(*Brain)
 		if err := br.knowledge.DropAll(); err != nil {
 			b.Fatal(err)
diff --git a/brain/learn.go b/brain/learn.go
index c0d4c5c..01f3ab2 100644
--- a/brain/learn.go
+++ b/brain/learn.go
@@ -17,38 +17,10 @@ type Tuple struct {
 	Suffix string
 }
 
-// Learner records Markov chain tuples.
-type Learner interface {
-	// Learn records a set of tuples.
-	// One tuple has an empty prefix to denote the start of the message, and
-	// a different tuple has the empty string as its suffix to denote the end
-	// of the message. The positions of each in the argument are not guaranteed.
-	// Each tuple's prefix has entropy reduction transformations applied.
-	// Tuples in the argument may share storage for prefixes.
-	Learn(ctx context.Context, tag string, msg *Message, tuples []Tuple) error
-	// Forget forgets everything learned from a single given message.
-	// If nothing has been learned from the message, it should prevent anything
-	// from being learned from a message with that ID.
-	Forget(ctx context.Context, tag, id string) error
-	// Recall reads out messages the brain knows.
-	// At minimum, the message ID and text of each message must be retrieved;
-	// other fields may be filled if they are available.
-	// It must be safe to call Recall concurrently with other methods of the
-	// implementation.
-	// Repeated calls using the pagination token returned from the previous
-	// must yield every message that the brain had recorded at the time of the
-	// first call exactly once. Messages learned after the first call of an
-	// enumeration are read at most once.
-	// The first call of an enumeration uses an empty pagination token.
-	// If the returned pagination token is empty, it is interpreted as the end
-	// of the enumeration.
-	Recall(ctx context.Context, tag, page string, out []Message) (n int, next string, err error)
-}
-
 var tuplesPool tpool.Pool[[]Tuple]
 
-// Learn records a message into a Learner.
-func Learn(ctx context.Context, l Learner, tag string, msg *Message) error {
+// Learn records a message into a brain.
+func Learn(ctx context.Context, l Interface, tag string, msg *Message) error {
 	toks := tokens(tokensPool.Get(), msg.Text)
 	defer func() { tokensPool.Put(toks[:0]) }()
 	if len(toks) == 0 {
@@ -77,7 +49,7 @@ func tupleToks(tt []Tuple, toks []string) []Tuple {
 }
 
 // Recall iterates over all messages a brain knows with a given tag.
-func Recall(ctx context.Context, br Learner, tag string) iter.Seq2[Message, error] {
+func Recall(ctx context.Context, br Interface, tag string) iter.Seq2[Message, error] {
 	return func(yield func(Message, error) bool) {
 		var (
 			page string
diff --git a/brain/learn_test.go b/brain/learn_test.go
index 20f4158..9a30a7d 100644
--- a/brain/learn_test.go
+++ b/brain/learn_test.go
@@ -27,6 +27,11 @@ func (t *testLearner) Forget(ctx context.Context, tag, id string) error {
 	return nil
 }
 
+// Speak implements brain.Brain.
+func (t *testLearner) Speak(ctx context.Context, tag string, prompt []string, w *brain.Builder) error {
+	panic("unimplemented")
+}
+
 func (t *testLearner) Recall(ctx context.Context, tag string, page string, out []brain.Message) (n int, next string, err error) {
 	var k int
 	if page != "" {
diff --git a/brain/speak.go b/brain/speak.go
index 97486e9..d973fe1 100644
--- a/brain/speak.go
+++ b/brain/speak.go
@@ -9,13 +9,6 @@ import (
 	"github.com/zephyrtronium/robot/tpool"
 )
 
-// Speaker produces random messages.
-type Speaker interface {
-	// Speak generates a full message and appends it to w.
-	// The prompt is in reverse order and has entropy reduction applied.
-	Speak(ctx context.Context, tag string, prompt []string, w *Builder) error
-}
-
 var (
 	tokensPool  tpool.Pool[[]string]
 	builderPool = tpool.Pool[*Builder]{New: func() any { return new(Builder) }}
@@ -23,9 +16,9 @@ var (
 
 // Speak produces a new message and the trace of messages used to form it
 // from the given prompt.
-// If the speaker does not produce any terms, the result is the empty string
+// If the brain does not produce any terms, the result is the empty string
 // regardless of the prompt, with no error.
-func Speak(ctx context.Context, s Speaker, tag, prompt string) (string, []string, error) {
+func Speak(ctx context.Context, s Interface, tag, prompt string) (string, []string, error) {
 	w := builderPool.Get()
 	toks := tokens(tokensPool.Get(), prompt)
 	defer func() {
diff --git a/brain/speak_test.go b/brain/speak_test.go
index dba28f5..25b0588 100644
--- a/brain/speak_test.go
+++ b/brain/speak_test.go
@@ -8,6 +8,8 @@ import (
 	"github.com/google/go-cmp/cmp/cmpopts"
 
 	"github.com/zephyrtronium/robot/brain"
+	"github.com/zephyrtronium/robot/message"
+	"github.com/zephyrtronium/robot/userhash"
 )
 
 type testSpeaker struct {
@@ -22,6 +24,21 @@ func (t *testSpeaker) Speak(ctx context.Context, tag string, prompt []string, w
 	return nil
 }
 
+// Forget implements brain.Brain.
+func (t *testSpeaker) Forget(ctx context.Context, tag string, id string) error {
+	panic("unimplemented")
+}
+
+// Learn implements brain.Brain.
+func (t *testSpeaker) Learn(ctx context.Context, tag string, msg *message.Received[userhash.Hash], tuples []brain.Tuple) error {
+	panic("unimplemented")
+}
+
+// Recall implements brain.Brain.
+func (t *testSpeaker) Recall(ctx context.Context, tag string, page string, out []message.Received[userhash.Hash]) (n int, next string, err error) {
+	panic("unimplemented")
+}
+
 func TestSpeak(t *testing.T) {
 	cases := []struct {
 		name   string
diff --git a/brain/sqlbrain/brain_test.go b/brain/sqlbrain/brain_test.go
index af4852d..dcdf3e0 100644
--- a/brain/sqlbrain/brain_test.go
+++ b/brain/sqlbrain/brain_test.go
@@ -30,13 +30,10 @@ func testDB(ctx context.Context) *sqlitex.Pool {
 	return pool
 }
 
-var _ brain.Learner = (*sqlbrain.Brain)(nil)
-var _ brain.Speaker = (*sqlbrain.Brain)(nil)
-
 func TestIntegrated(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
-	new := func(ctx context.Context) brain.Brain {
+	new := func(ctx context.Context) brain.Interface {
 		db := testDB(ctx)
 		br, err := sqlbrain.Open(ctx, db)
 		if err != nil {
diff --git a/brain/sqlbrain/learn_test.go b/brain/sqlbrain/learn_test.go
index 86f613e..a0d207b 100644
--- a/brain/sqlbrain/learn_test.go
+++ b/brain/sqlbrain/learn_test.go
@@ -570,7 +570,7 @@ func TestRecall(t *testing.T) {
 
 func BenchmarkLearn(b *testing.B) {
 	dir := filepath.ToSlash(b.TempDir())
-	new := func(ctx context.Context, b *testing.B) brain.Learner {
+	new := func(ctx context.Context, b *testing.B) brain.Interface {
 		dsn := fmt.Sprintf("file:%s/benchmark_learn.db?_journal=WAL", dir)
 		db, err := sqlitex.NewPool(dsn, sqlitex.PoolOptions{PrepareConn: sqlbrain.RecommendedPrep})
 		if err != nil {
@@ -589,5 +589,5 @@ func BenchmarkLearn(b *testing.B) {
 		}
 		return br
 	}
-	braintest.BenchLearn(context.Background(), b, new, func(l brain.Learner) { l.(*sqlbrain.Brain).Close() })
+	braintest.BenchLearn(context.Background(), b, new, func(l brain.Interface) { l.(*sqlbrain.Brain).Close() })
 }
diff --git a/brain/sqlbrain/speak_test.go b/brain/sqlbrain/speak_test.go
index 0c7dcdb..b168a20 100644
--- a/brain/sqlbrain/speak_test.go
+++ b/brain/sqlbrain/speak_test.go
@@ -518,7 +518,7 @@ func insert(t *testing.T, conn *sqlite.Conn, know []know, msgs []msg) {
 
 func BenchmarkSpeak(b *testing.B) {
 	var dbs atomic.Uint64
-	new := func(ctx context.Context, b *testing.B) brain.Brain {
+	new := func(ctx context.Context, b *testing.B) brain.Interface {
 		k := dbs.Add(1)
 		db, err := sqlitex.NewPool(fmt.Sprintf("file:%s/bench-%d.sql", b.TempDir(), k), sqlitex.PoolOptions{PrepareConn: sqlbrain.RecommendedPrep})
 		if err != nil {
@@ -530,7 +530,7 @@ func BenchmarkSpeak(b *testing.B) {
 		}
 		return br
 	}
-	cleanup := func(l brain.Brain) {
+	cleanup := func(l brain.Interface) {
 		br := l.(*sqlbrain.Brain)
 		br.Close()
 	}
diff --git a/command/command.go b/command/command.go
index 38bd0d3..8709848 100644
--- a/command/command.go
+++ b/command/command.go
@@ -17,7 +17,7 @@ import (
 type Robot struct {
 	Log      *slog.Logger
 	Channels *syncmap.Map[string, *channel.Channel]
-	Brain    brain.Brain
+	Brain    brain.Interface
 	Privacy  *privacy.List
 	Spoken   *spoken.History
 	Owner    string
diff --git a/main.go b/main.go
index a878742..647e83a 100644
--- a/main.go
+++ b/main.go
@@ -151,7 +151,7 @@ func cliSpeak(ctx context.Context, cmd *cli.Command) error {
 	if err != nil {
 		return err
 	}
-	var br brain.Brain
+	var br brain.Interface
 	if sql == nil {
 		if kv == nil {
 			panic("robot: no brain")
@@ -202,7 +202,7 @@ func cliAncient(ctx context.Context, cmd *cli.Command) error {
 	if err != nil {
 		return err
 	}
-	var br brain.Brain
+	var br brain.Interface
 	if sql == nil {
 		if kv == nil {
 			panic("robot: no brain")
diff --git a/robot.go b/robot.go
index 00785c8..6b1708d 100644
--- a/robot.go
+++ b/robot.go
@@ -28,7 +28,7 @@ import (
 // Robot is the overall configuration for the bot.
 type Robot struct {
 	// brain is the brain.
-	brain brain.Brain
+	brain brain.Interface
 	// privacy is the privacy.
 	privacy *privacy.List
 	// spoken is the history of generated messages.
diff --git a/tmi.go b/tmi.go
index 567cee4..2832443 100644
--- a/tmi.go
+++ b/tmi.go
@@ -195,7 +195,7 @@ func (robo *Robot) clearmsg(ctx context.Context, msg *tmi.Message) {
 	forget(ctx, log, robo.Metrics.ForgotCount, robo.brain, ch.Send, trace...)
 }
 
-func forget(ctx context.Context, log *slog.Logger, forgetCount metrics.Observer, brain brain.Brain, tag string, trace ...string) {
+func forget(ctx context.Context, log *slog.Logger, forgetCount metrics.Observer, brain brain.Interface, tag string, trace ...string) {
 	forgetCount.Observe(1)
 	for _, id := range trace {
 		err := brain.Forget(ctx, tag, id)