diff --git a/mcp/client.go b/mcp/client.go
index 7349ba9..b862c79 100644
--- a/mcp/client.go
+++ b/mcp/client.go
@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"iter"
+	"log/slog"
 	"slices"
 	"strings"
 	"sync"
@@ -26,6 +27,7 @@ import (
 type Client struct {
 	impl                    *Implementation
 	opts                    ClientOptions
+	logger                  *slog.Logger // TODO: file proposal to export this
 	mu                      sync.Mutex
 	roots                   *featureSet[*Root]
 	sessions                []*ClientSession
@@ -46,6 +48,7 @@ func NewClient(impl *Implementation, opts *ClientOptions) *Client {
 	}
 	c := &Client{
 		impl:                    impl,
+		logger:                  ensureLogger(nil), // ensure we have a logger
 		roots:                   newFeatureSet(func(r *Root) string { return r.URI }),
 		sendingMethodHandler_:   defaultSendingMethodHandler,
 		receivingMethodHandler_: defaultReceivingMethodHandler[*ClientSession],
@@ -341,7 +344,7 @@ func changeAndNotify[P Params](c *Client, notification string, params P, change
 		sessions = slices.Clone(c.sessions)
 	}
 	c.mu.Unlock()
-	notifySessions(sessions, notification, params)
+	notifySessions(sessions, notification, params, c.logger)
 }
 
 func (c *Client) listRoots(_ context.Context, req *ListRootsRequest) (*ListRootsResult, error) {
diff --git a/mcp/server.go b/mcp/server.go
index d431722..5f5a4a5 100644
--- a/mcp/server.go
+++ b/mcp/server.go
@@ -508,7 +508,7 @@ func (s *Server) changeAndNotify(notification string, params Params, change func
 		sessions = slices.Clone(s.sessions)
 	}
 	s.mu.Unlock()
-	notifySessions(sessions, notification, params)
+	notifySessions(sessions, notification, params, s.opts.Logger)
 }
 
 // Sessions returns an iterator that yields the current set of server sessions.
@@ -708,7 +708,7 @@ func (s *Server) ResourceUpdated(ctx context.Context, params *ResourceUpdatedNot
 	subscribedSessions := s.resourceSubscriptions[params.URI]
 	sessions := slices.Collect(maps.Keys(subscribedSessions))
 	s.mu.Unlock()
-	notifySessions(sessions, notificationResourceUpdated, params)
+	notifySessions(sessions, notificationResourceUpdated, params, s.opts.Logger)
 	s.opts.Logger.Info("resource updated notification sent", "uri", params.URI, "subscriber_count", len(sessions))
 	return nil
 }
diff --git a/mcp/shared.go b/mcp/shared.go
index f19236f..c2e50d9 100644
--- a/mcp/shared.go
+++ b/mcp/shared.go
@@ -15,7 +15,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"log"
+	"log/slog"
 	"net/http"
 	"reflect"
 	"slices"
@@ -381,7 +381,8 @@ const (
 
 // notifySessions calls Notify on all the sessions.
 // Should be called on a copy of the peer sessions.
-func notifySessions[S Session, P Params](sessions []S, method string, params P) {
+// The logger must be non-nil.
+func notifySessions[S Session, P Params](sessions []S, method string, params P, logger *slog.Logger) {
 	if sessions == nil {
 		return
 	}
@@ -394,8 +395,7 @@ func notifySessions[S Session, P Params](sessions []S, method string, params P)
 	for _, s := range sessions {
 		req := newRequest(s, params)
 		if err := handleNotify(ctx, method, req); err != nil {
-			// TODO(#218): surface this error better
-			log.Printf("calling %s: %v", method, err)
+			logger.Warn(fmt.Sprintf("calling %s: %v", method, err))
 		}
 	}
 }
diff --git a/mcp/streamable.go b/mcp/streamable.go
index a24d96e..d6452b2 100644
--- a/mcp/streamable.go
+++ b/mcp/streamable.go
@@ -1453,7 +1453,7 @@ func (t *StreamableClientTransport) Connect(ctx context.Context) (Connection, er
 		done:       make(chan struct{}),
 		maxRetries: maxRetries,
 		strict:     t.strict,
-		logger:     t.logger,
+		logger:     ensureLogger(t.logger), // must be non-nil for safe logging
 		ctx:        connCtx,
 		cancel:     cancel,
 		failed:     make(chan struct{}),
@@ -1555,9 +1555,7 @@ func (c *streamableClientConn) connectStandaloneSSE() {
 		// stream.
 		//
 		// Treat this like MethodNotAllowed in non-strict mode.
-		if c.logger != nil {
-			c.logger.Warn(fmt.Sprintf("got %d instead of 405 for standalone SSE stream", resp.StatusCode))
-		}
+		c.logger.Warn(fmt.Sprintf("got %d instead of 405 for standalone SSE stream", resp.StatusCode))
 		resp.Body.Close()
 		return
 	}
@@ -1686,9 +1684,7 @@ func (c *streamableClientConn) Write(ctx context.Context, msg jsonrpc.Message) e
 			// Some servers return 200, even with an empty json body.
 			//
 			// In strict mode, return an error to the caller.
-			if c.logger != nil {
-				c.logger.Warn(errMsg)
-			}
+			c.logger.Warn(errMsg)
 			if c.strict {
 				return errors.New(errMsg)
 			}