fix(ws): raise bounded agent message limit

internal/server/ws/handler.go

@@ -77,6 +77,7 @@ func AgentHandler(deps HandlerDeps) stdhttp.Handler {
 			slog.Warn("ws accept failed", "err", err, "host_id", host.ID)
 			return
 		}
+		conn.SetReadLimit(api.MaxWebSocketMessageBytes)
 
 		c := NewConn(host.ID, conn)
 		// Keep agents alive across NAT boxes; coder/websocket

internal/server/ws/hub_test.go

@@ -123,6 +123,68 @@ func TestWSHelloAndHeartbeat(t *testing.T) {
 	t.Error("heartbeat did not update last_seen_at")
 }
 
+func TestWSAcceptsSnapshotReportLargerThanDefaultReadLimit(t *testing.T) {
+	t.Parallel()
+	url, token, hostID, st, hub := setupTestHub(t)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	c, _, err := websocket.Dial(ctx, url, &websocket.DialOptions{
+		HTTPHeader: stdhttp.Header{"Authorization": []string{"Bearer " + token}},
+	})
+	if err != nil {
+		t.Fatalf("dial: %v", err)
+	}
+	defer c.CloseNow() //nolint:errcheck
+
+	hello, _ := api.Marshal(api.MsgHello, "", api.HelloPayload{
+		ProtocolVersion: api.CurrentProtocolVersion,
+		AgentVersion:    "0.1.0",
+		ResticVersion:   "0.17.1",
+		Hostname:        "h1",
+		OS:              api.OSLinux,
+		Arch:            api.ArchAmd64,
+	})
+	helloRaw, _ := json.Marshal(hello)
+	if err := c.Write(ctx, websocket.MessageText, helloRaw); err != nil {
+		t.Fatalf("write hello: %v", err)
+	}
+	deadline := time.Now().Add(time.Second)
+	for !hub.Connected(hostID) && time.Now().Before(deadline) {
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	report, _ := api.Marshal(api.MsgSnapshotsRpt, "", api.SnapshotsReportPayload{
+		Snapshots: []api.Snapshot{{
+			ID:       strings.Repeat("a", 64),
+			ShortID:  "aaaaaaaa",
+			Time:     time.Now().UTC(),
+			Hostname: "h1",
+			Paths:    []string{"/" + strings.Repeat("long-path/", 5000)},
+		}},
+	})
+	reportRaw, _ := json.Marshal(report)
+	if len(reportRaw) <= 32*1024 {
+		t.Fatalf("test payload is only %d bytes; must exceed old limit", len(reportRaw))
+	}
+	if int64(len(reportRaw)) >= api.MaxWebSocketMessageBytes {
+		t.Fatalf("test payload %d exceeds protocol limit", len(reportRaw))
+	}
+	if err := c.Write(ctx, websocket.MessageText, reportRaw); err != nil {
+		t.Fatalf("write snapshots.report: %v", err)
+	}
+
+	deadline = time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		host, err := st.GetHost(context.Background(), hostID)
+		if err == nil && host.SnapshotCount == 1 {
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatal("oversized snapshots.report was not projected")
+}
+
 func TestWSRejectsOldProtocol(t *testing.T) {
 	t.Parallel()
 	url, token, _, _, _ := setupTestHub(t)