diff --git a/internal/labels/labeler.go b/internal/labels/labeler.go
index 45e7d5c..6fbb9cc 100644
--- a/internal/labels/labeler.go
+++ b/internal/labels/labeler.go
@@ -13,8 +13,10 @@ import (
 
 	"golang.org/x/oscar/internal/actions"
 	"golang.org/x/oscar/internal/github"
+	"golang.org/x/oscar/internal/llm"
 	"golang.org/x/oscar/internal/storage"
 	"golang.org/x/oscar/internal/storage/timed"
+	"rsc.io/ordered"
 )
 
 // A Labeler labels GitHub issues.
@@ -22,6 +24,7 @@ type Labeler struct {
 	slog        *slog.Logger
 	db          storage.DB
 	github      *github.Client
+	cgen        llm.ContentGenerator
 	projects    map[string]bool
 	watcher     *timed.Watcher[*github.Event]
 	name        string
@@ -35,8 +38,7 @@ type Labeler struct {
 }
 
 // New creates and returns a new Labeler. It logs to lg, stores state in db,
-//
-//	and watches for new GitHub issues using gh.
+// manipulates GitHub issues using gh, and classifies issues using cgen.
 //
 // For the purposes of storing its own state, it uses the given name.
 // Future calls to New with the same name will use the same state.
@@ -44,11 +46,12 @@ type Labeler struct {
 // Use the [Labeler] methods to configure the posting parameters
 // (especially [Labeler.EnableProject] and [Labeler.EnableLabels])
 // before calling [Labeler.Run].
-func New(lg *slog.Logger, db storage.DB, gh *github.Client, name string) *Labeler {
+func New(lg *slog.Logger, db storage.DB, gh *github.Client, cgen llm.ContentGenerator, name string) *Labeler {
 	l := &Labeler{
 		slog:      lg,
 		db:        db,
 		github:    gh,
+		cgen:      cgen,
 		projects:  make(map[string]bool),
 		watcher:   gh.EventWatcher("labels.Labeler:" + name),
 		name:      name,
@@ -159,7 +162,36 @@ func (l *Labeler) logLabelIssue(ctx context.Context, e *github.Event) (advance b
 			e.Project, "issue", e.Issue, "reason", reason, "event", e)
 		return false, nil
 	}
-	return false, errors.New("unimplemented")
+	// If an action has already been logged for this event, do nothing.
+	// we don't need a lock. [actions.before] will lock to avoid multiple log entries.
+	if _, ok := actions.Get(l.db, l.actionKind, logKey(e)); ok {
+		l.slog.Info("labels.Labeler already logged", "name", l.name, "project", e.Project, "issue", e.Issue, "event", e)
+		// If labeling is enabled, we can advance the watcher because
+		// a comment has already been logged for this issue.
+		return l.label, nil
+	}
+	// If we didn't skip, it's definitely an issue.
+	issue := e.Typed.(*github.Issue)
+	l.slog.Debug("labels.Labeler consider", "url", issue.HTMLURL)
+
+	cat, explanation, err := IssueCategory(ctx, l.cgen, issue)
+	if err != nil {
+		return false, fmt.Errorf("IssueCategory(%s): %w", issue.HTMLURL, err)
+	}
+	l.slog.Info("labels.Labeler chose label", "name", l.name, "project", e.Project, "issue", e.Issue,
+		"label", cat.Label, "explanation", explanation)
+
+	if !l.label {
+		// Labeling is disabled so we did not handle this issue.
+		return false, nil
+	}
+
+	act := &action{
+		Issue:     issue,
+		NewLabels: []string{cat.Label},
+	}
+	l.logAction(l.db, logKey(e), storage.JSON(act), l.requireApproval)
+	return true, nil
 }
 
 func (l *Labeler) skip(e *github.Event) (bool, string) {
@@ -206,7 +238,7 @@ func (l *Labeler) syncLabels(ctx context.Context, project string, cats []Categor
 	for _, cat := range cats {
 		lab, ok := tlabs[cat.Label]
 		if !ok {
-			l.slog.Info("creating label", "label", lab.Name)
+			l.slog.Info("creating label", "label", cat.Label)
 			if err := l.github.CreateLabel(ctx, project, github.Label{
 				Name:        cat.Label,
 				Description: cat.Description,
@@ -242,3 +274,9 @@ func (ar *actioner) ForDisplay(data []byte) string {
 	// TODO: implement
 	return ""
 }
+
+// logKey returns the key for the event in the action log. This is only a portion
+// of the database key; it is prefixed by the Labelers's action kind.
+func logKey(e *github.Event) []byte {
+	return ordered.Encode(e.Project, e.Issue)
+}
diff --git a/internal/labels/labeler_test.go b/internal/labels/labeler_test.go
index a6b0735..cc35677 100644
--- a/internal/labels/labeler_test.go
+++ b/internal/labels/labeler_test.go
@@ -6,11 +6,15 @@ package labels
 
 import (
 	"context"
+	"encoding/json"
 	"maps"
+	"slices"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"golang.org/x/oscar/internal/actions"
 	"golang.org/x/oscar/internal/github"
+	"golang.org/x/oscar/internal/llm"
 	"golang.org/x/oscar/internal/storage"
 	"golang.org/x/oscar/internal/testutil"
 )
@@ -20,7 +24,7 @@ func TestSyncLabels(t *testing.T) {
 	lg := testutil.Slogger(t)
 	db := storage.MemDB()
 	gh := github.New(lg, db, nil, nil)
-	labeler := New(lg, nil, gh, "")
+	labeler := New(lg, nil, gh, nil, "")
 	m := map[string]github.Label{
 		"A": {Name: "A", Description: "a", Color: "a"},
 		"B": {Name: "B", Description: "", Color: "b"},
@@ -60,3 +64,47 @@ func TestSyncLabels(t *testing.T) {
 		t.Errorf("mismatch (-want, got):\n%s", diff)
 	}
 }
+
+func TestRun(t *testing.T) {
+	const project = "golang/go"
+	ctx := context.Background()
+	check := testutil.Checker(t)
+	lg := testutil.Slogger(t)
+	db := storage.MemDB()
+	gh := github.New(lg, db, nil, nil)
+	gh.Testing().AddLabel(project, github.Label{Name: "bug"})
+	gh.Testing().AddIssue(project, &github.Issue{
+		Number: 1,
+		Title:  "title",
+		Body:   "body",
+	})
+	gh.Testing().AddIssue("other/project", &github.Issue{
+		Number: 2,
+		Title:  "title",
+		Body:   "body",
+	})
+	cgen := llm.TestContentGenerator("test", func(context.Context, *llm.Schema, []llm.Part) (string, error) {
+		return `{"CategoryName": "bug", "Explanation": "exp"}`, nil
+	})
+	l := New(lg, db, gh, cgen, "test")
+	l.EnableProject(project)
+	l.EnableLabels()
+
+	check(l.Run(ctx))
+	entries := slices.Collect(actions.ScanAfterDBTime(lg, db, 0, nil))
+	if g := len(entries); g != 1 {
+		t.Fatalf("got %d actions, want 1", g)
+	}
+	var got action
+	check(json.Unmarshal(entries[0].Action, &got))
+	if got.Issue.Number != 1 || !slices.Equal(got.NewLabels, []string{"Bug"}) {
+		t.Errorf("got (%d, %v), want (1, [Bug])", got.Issue.Number, got.NewLabels)
+	}
+
+	// Second time, nothing should happen.
+	check(l.Run(ctx))
+	entries = slices.Collect(actions.ScanAfterDBTime(lg, db, entries[0].ModTime, nil))
+	if g := len(entries); g != 0 {
+		t.Fatalf("got %d actions, want 0", g)
+	}
+}