diff --git a/pkg/engine/datasource/graphql_datasource/graphql_datasource.go b/pkg/engine/datasource/graphql_datasource/graphql_datasource.go
index 95dfa2316..e05c88ecc 100644
--- a/pkg/engine/datasource/graphql_datasource/graphql_datasource.go
+++ b/pkg/engine/datasource/graphql_datasource/graphql_datasource.go
@@ -1163,16 +1163,24 @@ func (p *Planner) addField(ref int) {
 	p.nodes = append(p.nodes, field)
 }
 
+type OnWsConnectionInitCallback func(ctx context.Context, url string, header http.Header) (json.RawMessage, error)
+
 type Factory struct {
-	BatchFactory       resolve.DataSourceBatchFactory
-	HTTPClient         *http.Client
-	StreamingClient    *http.Client
-	subscriptionClient *SubscriptionClient
+	BatchFactory               resolve.DataSourceBatchFactory
+	HTTPClient                 *http.Client
+	StreamingClient            *http.Client
+	OnWsConnectionInitCallback *OnWsConnectionInitCallback
+	subscriptionClient         *SubscriptionClient
 }
 
 func (f *Factory) Planner(ctx context.Context) plan.DataSourcePlanner {
 	if f.subscriptionClient == nil {
-		f.subscriptionClient = NewGraphQLSubscriptionClient(f.HTTPClient, f.StreamingClient, ctx)
+		opts := make([]Options, 0)
+		if f.OnWsConnectionInitCallback != nil {
+			opts = append(opts, WithOnWsConnectionInitCallback(f.OnWsConnectionInitCallback))
+		}
+
+		f.subscriptionClient = NewGraphQLSubscriptionClient(f.HTTPClient, f.StreamingClient, ctx, opts...)
 	}
 	return &Planner{
 		batchFactory:       f.BatchFactory,
diff --git a/pkg/engine/datasource/graphql_datasource/graphql_subscription_client.go b/pkg/engine/datasource/graphql_datasource/graphql_subscription_client.go
index 11622c562..81c064f29 100644
--- a/pkg/engine/datasource/graphql_datasource/graphql_subscription_client.go
+++ b/pkg/engine/datasource/graphql_datasource/graphql_subscription_client.go
@@ -7,9 +7,8 @@ import (
 	"sync"
 	"time"
 
-	"github.com/cespare/xxhash/v2"
-
 	"github.com/buger/jsonparser"
+	"github.com/cespare/xxhash/v2"
 	"github.com/jensneuse/abstractlogger"
 	"nhooyr.io/websocket"
 )
@@ -20,14 +19,15 @@ const ackWaitTimeout = 30 * time.Second
 // It takes care of de-duplicating connections to the same origin under certain circumstances
 // If Hash(URL,Body,Headers) result in the same result, an existing connection is re-used
 type SubscriptionClient struct {
-	streamingClient *http.Client
-	httpClient      *http.Client
-	engineCtx       context.Context
-	log             abstractlogger.Logger
-	hashPool        sync.Pool
-	handlers        map[uint64]ConnectionHandler
-	handlersMu      sync.Mutex
-	wsSubProtocol   string
+	streamingClient            *http.Client
+	httpClient                 *http.Client
+	engineCtx                  context.Context
+	log                        abstractlogger.Logger
+	hashPool                   sync.Pool
+	handlers                   map[uint64]ConnectionHandler
+	handlersMu                 sync.Mutex
+	wsSubProtocol              string
+	onWsConnectionInitCallback *OnWsConnectionInitCallback
 
 	readTimeout time.Duration
 }
@@ -52,10 +52,17 @@ func WithWSSubProtocol(protocol string) Options {
 	}
 }
 
+func WithOnWsConnectionInitCallback(callback *OnWsConnectionInitCallback) Options {
+	return func(options *opts) {
+		options.onWsConnectionInitCallback = callback
+	}
+}
+
 type opts struct {
-	readTimeout   time.Duration
-	log           abstractlogger.Logger
-	wsSubProtocol string
+	readTimeout                time.Duration
+	log                        abstractlogger.Logger
+	wsSubProtocol              string
+	onWsConnectionInitCallback *OnWsConnectionInitCallback
 }
 
 func NewGraphQLSubscriptionClient(httpClient, streamingClient *http.Client, engineCtx context.Context, options ...Options) *SubscriptionClient {
@@ -78,7 +85,8 @@ func NewGraphQLSubscriptionClient(httpClient, streamingClient *http.Client, engi
 				return xxhash.New()
 			},
 		},
-		wsSubProtocol: op.wsSubProtocol,
+		wsSubProtocol:              op.wsSubProtocol,
+		onWsConnectionInitCallback: op.onWsConnectionInitCallback,
 	}
 }
 
@@ -199,6 +207,11 @@ func (c *SubscriptionClient) newWSConnectionHandler(reqCtx context.Context, opti
 		return nil, fmt.Errorf("upgrade unsuccessful")
 	}
 
+	connectionInitMessage, err := c.getConnectionInitMessage(reqCtx, options.URL, options.Header)
+	if err != nil {
+		return nil, err
+	}
+
 	// init + ack
 	err = conn.Write(reqCtx, websocket.MessageText, connectionInitMessage)
 	if err != nil {
@@ -223,6 +236,30 @@ func (c *SubscriptionClient) newWSConnectionHandler(reqCtx context.Context, opti
 	}
 }
 
+func (c *SubscriptionClient) getConnectionInitMessage(ctx context.Context, url string, header http.Header) ([]byte, error) {
+	if c.onWsConnectionInitCallback == nil {
+		return connectionInitMessage, nil
+	}
+
+	callback := *c.onWsConnectionInitCallback
+
+	payload, err := callback(ctx, url, header)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(payload) == 0 {
+		return connectionInitMessage, nil
+	}
+
+	msg, err := jsonparser.Set(connectionInitMessage, payload, "payload")
+	if err != nil {
+		return nil, err
+	}
+
+	return msg, nil
+}
+
 type ConnectionHandler interface {
 	StartBlocking(sub Subscription)
 	SubscribeCH() chan<- Subscription
diff --git a/pkg/engine/datasource/graphql_datasource/graphql_subscription_client_test.go b/pkg/engine/datasource/graphql_datasource/graphql_subscription_client_test.go
index 53de7c564..372596624 100644
--- a/pkg/engine/datasource/graphql_datasource/graphql_subscription_client_test.go
+++ b/pkg/engine/datasource/graphql_datasource/graphql_subscription_client_test.go
@@ -2,6 +2,7 @@ package graphql_datasource
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -10,6 +11,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/buger/jsonparser"
 	ll "github.com/jensneuse/abstractlogger"
 	"github.com/stretchr/testify/assert"
@@ -27,6 +30,40 @@ func logger() ll.Logger {
 	return ll.NewZapLogger(logger, ll.DebugLevel)
 }
 
+func TestGetConnectionInitMessageHelper(t *testing.T) {
+	var callback OnWsConnectionInitCallback = func(ctx context.Context, url string, header http.Header) (json.RawMessage, error) {
+		return json.RawMessage(`{"authorization":"secret"}`), nil
+	}
+
+	tests := []struct {
+		name     string
+		callback *OnWsConnectionInitCallback
+		want     string
+	}{
+		{
+			name:     "without payload",
+			callback: nil,
+			want:     `{"type":"connection_init"}`,
+		},
+		{
+			name:     "with payload",
+			callback: &callback,
+			want:     `{"type":"connection_init","payload":{"authorization":"secret"}}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			client := SubscriptionClient{onWsConnectionInitCallback: tt.callback}
+			got, err := client.getConnectionInitMessage(context.Background(), "", nil)
+			require.NoError(t, err)
+			require.NotEmpty(t, got)
+
+			assert.Equal(t, tt.want, string(got))
+		})
+	}
+}
+
 func TestWebsocketSubscriptionClientDeDuplication(t *testing.T) {
 	serverDone := &sync.WaitGroup{}
 	connectedClients := atomic.NewInt64(0)