diff --git a/SESSION_PLAN.md b/SESSION_PLAN.md
index e5f663b..e62da7c 100644
--- a/SESSION_PLAN.md
+++ b/SESSION_PLAN.md
@@ -35,7 +35,7 @@ Rewriting Bellhop from a Python FastAPI web portal into a Go-based Matrix comman
   - All adds: monitored=true, search-on-add=true, quality profile + root folder from config
   - Unit tests with httptest
 
-- [ ] **Session 4 — Command dispatch + main** (`internal/bot/`, `main.go`)
+- [x] **Session 4 — Command dispatch + main** (`internal/bot/`, `main.go`)
   - Parse `<prefix><cmd> <query>` (default prefix `!`)
   - Commands: `movie`, `tv`, `music`, `help`
   - On match: search → take `[0]` → add → reply with title/year (or error)
diff --git a/internal/bot/bot.go b/internal/bot/bot.go
new file mode 100644
index 0000000..9d5a797
--- /dev/null
+++ b/internal/bot/bot.go
@@ -0,0 +1,162 @@
+// Package bot wires Matrix command messages to the *arr clients.
+//
+// Commands take the form "<prefix><cmd> <query>" (e.g. "!movie dune"). The
+// dispatcher parses the message, picks the *arr client by command name,
+// performs a lookup, and adds the top hit. The reply is posted back into a
+// thread rooted at the request event so a busy room stays readable.
+package bot
+
+import (
+	"context"
+	"fmt"
+	"html"
+	"log/slog"
+	"strings"
+	"time"
+
+	"bellhop/internal/arr"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// Replier sends a threaded reply into roomID under rootEventID.
+type Replier interface {
+	PostThreadedReply(roomID id.RoomID, rootEventID id.EventID, plain, htmlBody string) error
+}
+
+// Services holds the configured *arr clients. Any field may be nil; commands
+// that target an unconfigured service reply with "not configured".
+type Services struct {
+	Radarr arr.Client
+	Sonarr arr.Client
+	Lidarr arr.Client
+}
+
+// Dispatcher routes parsed commands to services and posts replies.
+type Dispatcher struct {
+	prefix   string
+	services Services
+	replier  Replier
+	timeout  time.Duration
+}
+
+// New builds a Dispatcher. prefix is the leading character(s) on a command
+// (e.g. "!"); a zero value defaults to "!".
+func New(prefix string, services Services, replier Replier) *Dispatcher {
+	if prefix == "" {
+		prefix = "!"
+	}
+	return &Dispatcher{
+		prefix:   prefix,
+		services: services,
+		replier:  replier,
+		timeout:  60 * time.Second,
+	}
+}
+
+// Handle is the matrix.MessageHandler entry point. It parses body, dispatches
+// the command, and posts a reply. Non-command messages are ignored silently.
+func (d *Dispatcher) Handle(roomID id.RoomID, eventID id.EventID, sender id.UserID, body string) {
+	cmd, query, ok := parseCommand(d.prefix, body)
+	if !ok {
+		return
+	}
+
+	slog.Info("bot: command received", "room", roomID, "sender", sender, "cmd", cmd, "query", query)
+
+	ctx, cancel := context.WithTimeout(context.Background(), d.timeout)
+	defer cancel()
+
+	plain, htmlBody := d.dispatch(ctx, cmd, query)
+	if err := d.replier.PostThreadedReply(roomID, eventID, plain, htmlBody); err != nil {
+		slog.Error("bot: reply failed", "room", roomID, "err", err)
+	}
+}
+
+// parseCommand pulls (cmd, query) out of a body like "!movie dune". Returns
+// ok=false when the message is not a command for us.
+func parseCommand(prefix, body string) (cmd, query string, ok bool) {
+	body = strings.TrimSpace(body)
+	if !strings.HasPrefix(body, prefix) {
+		return "", "", false
+	}
+	rest := strings.TrimSpace(body[len(prefix):])
+	if rest == "" {
+		return "", "", false
+	}
+	parts := strings.SplitN(rest, " ", 2)
+	cmd = strings.ToLower(parts[0])
+	if len(parts) == 2 {
+		query = strings.TrimSpace(parts[1])
+	}
+	return cmd, query, true
+}
+
+func (d *Dispatcher) dispatch(ctx context.Context, cmd, query string) (plain, htmlBody string) {
+	switch cmd {
+	case "help":
+		return d.help()
+	case "movie":
+		return d.run(ctx, "movie", "Radarr", d.services.Radarr, query)
+	case "tv":
+		return d.run(ctx, "tv", "Sonarr", d.services.Sonarr, query)
+	case "music":
+		return d.run(ctx, "music", "Lidarr", d.services.Lidarr, query)
+	default:
+		msg := fmt.Sprintf("Unknown command %q. Try %shelp.", cmd, d.prefix)
+		return msg, html.EscapeString(msg)
+	}
+}
+
+func (d *Dispatcher) run(ctx context.Context, cmd, service string, client arr.Client, query string) (plain, htmlBody string) {
+	if client == nil {
+		msg := fmt.Sprintf("%s is not configured.", service)
+		return msg, html.EscapeString(msg)
+	}
+	if query == "" {
+		msg := fmt.Sprintf("Usage: %s%s <query>", d.prefix, cmd)
+		return msg, html.EscapeString(msg)
+	}
+
+	results, err := client.Search(ctx, query)
+	if err != nil {
+		slog.Error("bot: search failed", "service", service, "query", query, "err", err)
+		msg := fmt.Sprintf("%s search failed: %v", service, err)
+		return msg, html.EscapeString(msg)
+	}
+	if len(results) == 0 {
+		msg := fmt.Sprintf("No %s results for %q.", service, query)
+		return msg, html.EscapeString(msg)
+	}
+
+	top := results[0]
+	if err := client.Add(ctx, top); err != nil {
+		slog.Error("bot: add failed", "service", service, "title", top.Title, "err", err)
+		msg := fmt.Sprintf("%s: failed to add %s: %v", service, formatTitle(top), err)
+		return msg, html.EscapeString(msg)
+	}
+
+	plain = fmt.Sprintf("Added to %s: %s", service, formatTitle(top))
+	htmlBody = fmt.Sprintf("Added to <b>%s</b>: %s", html.EscapeString(service), html.EscapeString(formatTitle(top)))
+	return plain, htmlBody
+}
+
+func (d *Dispatcher) help() (string, string) {
+	lines := []string{
+		"Bellhop commands:",
+		fmt.Sprintf("  %smovie <query>  — add the top Radarr hit", d.prefix),
+		fmt.Sprintf("  %stv <query>     — add the top Sonarr hit", d.prefix),
+		fmt.Sprintf("  %smusic <query>  — add the top Lidarr hit", d.prefix),
+		fmt.Sprintf("  %shelp           — show this message", d.prefix),
+	}
+	plain := strings.Join(lines, "\n")
+	htmlBody := "<pre>" + html.EscapeString(plain) + "</pre>"
+	return plain, htmlBody
+}
+
+func formatTitle(r arr.Result) string {
+	if r.Year > 0 {
+		return fmt.Sprintf("%s (%d)", r.Title, r.Year)
+	}
+	return r.Title
+}
diff --git a/internal/bot/bot_test.go b/internal/bot/bot_test.go
new file mode 100644
index 0000000..5168c91
--- /dev/null
+++ b/internal/bot/bot_test.go
@@ -0,0 +1,218 @@
+package bot
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+
+	"bellhop/internal/arr"
+
+	"maunium.net/go/mautrix/id"
+)
+
+type stubClient struct {
+	results []arr.Result
+	addErr  error
+	srchErr error
+
+	searched string
+	added    []arr.Result
+}
+
+func (s *stubClient) Search(_ context.Context, term string) ([]arr.Result, error) {
+	s.searched = term
+	if s.srchErr != nil {
+		return nil, s.srchErr
+	}
+	return s.results, nil
+}
+
+func (s *stubClient) Add(_ context.Context, r arr.Result) error {
+	if s.addErr != nil {
+		return s.addErr
+	}
+	s.added = append(s.added, r)
+	return nil
+}
+
+type stubReplier struct {
+	mu       sync.Mutex
+	plain    string
+	htmlBody string
+	calls    int
+}
+
+func (r *stubReplier) PostThreadedReply(_ id.RoomID, _ id.EventID, plain, htmlBody string) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.calls++
+	r.plain = plain
+	r.htmlBody = htmlBody
+	return nil
+}
+
+const (
+	room   = id.RoomID("!room:example.org")
+	event  = id.EventID("$evt")
+	sender = id.UserID("@alice:example.org")
+)
+
+func TestParseCommand(t *testing.T) {
+	cases := []struct {
+		body            string
+		wantCmd, wantQ  string
+		wantOk          bool
+	}{
+		{"!movie dune", "movie", "dune", true},
+		{"  !movie  dune part two  ", "movie", "dune part two", true},
+		{"!HELP", "help", "", true},
+		{"hello world", "", "", false},
+		{"!", "", "", false},
+		{"!  ", "", "", false},
+	}
+	for _, c := range cases {
+		cmd, q, ok := parseCommand("!", c.body)
+		if cmd != c.wantCmd || q != c.wantQ || ok != c.wantOk {
+			t.Errorf("parseCommand(%q) = (%q,%q,%v); want (%q,%q,%v)",
+				c.body, cmd, q, ok, c.wantCmd, c.wantQ, c.wantOk)
+		}
+	}
+}
+
+func TestDispatchMovieTopHit(t *testing.T) {
+	radarr := &stubClient{results: []arr.Result{
+		{Title: "Dune", Year: 2021},
+		{Title: "Dune", Year: 1984},
+	}}
+	rep := &stubReplier{}
+	d := New("!", Services{Radarr: radarr}, rep)
+
+	d.Handle(room, event, sender, "!movie dune")
+
+	if radarr.searched != "dune" {
+		t.Fatalf("search term = %q", radarr.searched)
+	}
+	if len(radarr.added) != 1 || radarr.added[0].Year != 2021 {
+		t.Fatalf("expected top hit added, got %+v", radarr.added)
+	}
+	if !strings.Contains(rep.plain, "Dune (2021)") || !strings.Contains(rep.plain, "Radarr") {
+		t.Fatalf("reply missing expected content: %q", rep.plain)
+	}
+}
+
+func TestDispatchNoResults(t *testing.T) {
+	sonarr := &stubClient{}
+	rep := &stubReplier{}
+	d := New("!", Services{Sonarr: sonarr}, rep)
+
+	d.Handle(room, event, sender, "!tv obscure show")
+
+	if len(sonarr.added) != 0 {
+		t.Fatal("should not add when no results")
+	}
+	if !strings.Contains(rep.plain, "No Sonarr results") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestDispatchUnconfigured(t *testing.T) {
+	rep := &stubReplier{}
+	d := New("!", Services{}, rep)
+
+	d.Handle(room, event, sender, "!music radiohead")
+
+	if !strings.Contains(rep.plain, "Lidarr is not configured") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestDispatchEmptyQuery(t *testing.T) {
+	radarr := &stubClient{}
+	rep := &stubReplier{}
+	d := New("!", Services{Radarr: radarr}, rep)
+
+	d.Handle(room, event, sender, "!movie")
+
+	if radarr.searched != "" {
+		t.Fatal("should not search with empty query")
+	}
+	if !strings.Contains(rep.plain, "Usage:") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestDispatchAddError(t *testing.T) {
+	radarr := &stubClient{
+		results: []arr.Result{{Title: "Dune", Year: 2021}},
+		addErr:  errors.New("boom"),
+	}
+	rep := &stubReplier{}
+	d := New("!", Services{Radarr: radarr}, rep)
+
+	d.Handle(room, event, sender, "!movie dune")
+
+	if !strings.Contains(rep.plain, "failed to add") || !strings.Contains(rep.plain, "boom") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestDispatchSearchError(t *testing.T) {
+	radarr := &stubClient{srchErr: errors.New("network down")}
+	rep := &stubReplier{}
+	d := New("!", Services{Radarr: radarr}, rep)
+
+	d.Handle(room, event, sender, "!movie dune")
+
+	if !strings.Contains(rep.plain, "search failed") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestDispatchHelp(t *testing.T) {
+	rep := &stubReplier{}
+	d := New("!", Services{}, rep)
+
+	d.Handle(room, event, sender, "!help")
+
+	for _, want := range []string{"!movie", "!tv", "!music", "!help"} {
+		if !strings.Contains(rep.plain, want) {
+			t.Errorf("help missing %q: %q", want, rep.plain)
+		}
+	}
+}
+
+func TestDispatchUnknown(t *testing.T) {
+	rep := &stubReplier{}
+	d := New("!", Services{}, rep)
+
+	d.Handle(room, event, sender, "!frobnicate stuff")
+
+	if !strings.Contains(rep.plain, "Unknown command") {
+		t.Fatalf("unexpected reply: %q", rep.plain)
+	}
+}
+
+func TestNonCommandIgnored(t *testing.T) {
+	rep := &stubReplier{}
+	d := New("!", Services{}, rep)
+
+	d.Handle(room, event, sender, "just chatting")
+
+	if rep.calls != 0 {
+		t.Fatalf("expected no reply, got %d", rep.calls)
+	}
+}
+
+func TestCustomPrefix(t *testing.T) {
+	radarr := &stubClient{results: []arr.Result{{Title: "Dune", Year: 2021}}}
+	rep := &stubReplier{}
+	d := New(".bh ", Services{Radarr: radarr}, rep)
+
+	d.Handle(room, event, sender, ".bh movie dune")
+
+	if len(radarr.added) != 1 {
+		t.Fatalf("expected add, got %d", len(radarr.added))
+	}
+}
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..b27817a
--- /dev/null
+++ b/main.go
@@ -0,0 +1,62 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"log/slog"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"bellhop/internal/arr"
+	"bellhop/internal/bot"
+	"bellhop/internal/config"
+	"bellhop/internal/matrix"
+)
+
+func main() {
+	configPath := flag.String("config", "config.yaml", "path to config file")
+	flag.Parse()
+
+	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelInfo})))
+
+	cfg, err := config.Load(*configPath)
+	if err != nil {
+		slog.Error("config load failed", "err", err)
+		os.Exit(1)
+	}
+
+	services := bot.Services{}
+	if cfg.Services.Radarr != nil {
+		services.Radarr = arr.NewRadarr(cfg.Services.Radarr)
+	}
+	if cfg.Services.Sonarr != nil {
+		services.Sonarr = arr.NewSonarr(cfg.Services.Sonarr)
+	}
+	if cfg.Services.Lidarr != nil {
+		services.Lidarr = arr.NewLidarr(cfg.Services.Lidarr)
+	}
+
+	mx, err := matrix.New(cfg.Matrix)
+	if err != nil {
+		slog.Error("matrix init failed", "err", err)
+		os.Exit(1)
+	}
+
+	dispatcher := bot.New(cfg.Matrix.CommandPrefix, services, mx)
+	mx.SetMessageHandler(dispatcher.Handle)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	mx.Start(ctx)
+	slog.Info("bellhop started", "allowed_rooms", len(cfg.Matrix.AllowedRooms))
+
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	<-sig
+
+	slog.Info("shutting down")
+	cancel()
+	mx.Stop()
+}