diff --git a/internal/runtime/executor/xai_executor.go b/internal/runtime/executor/xai_executor.go
index ff9acd08b..c6795ef98 100644
--- a/internal/runtime/executor/xai_executor.go
+++ b/internal/runtime/executor/xai_executor.go
@@ -13,6 +13,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/google/uuid"
 	xaiauth "github.com/router-for-me/CLIProxyAPI/v7/internal/auth/xai"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/runtime/executor/helps"
@@ -49,6 +50,7 @@ const (
 	xaiVideosExtensionsPath     = "/videos/extensions"
 	xaiVideosPath               = "/videos"
 	xaiIdempotencyKeyMetaKey    = "idempotency_key"
+	xaiComposerModelPrefix      = "grok-composer-"
 )
 
 // XAIExecutor is a stateless executor for xAI Grok's Responses API.
@@ -837,6 +839,9 @@ func (e *XAIExecutor) prepareResponsesRequestTo(ctx context.Context, req cliprox
 	body = sanitizeXAIResponsesBody(body, baseModel)
 
 	sessionID := xaiExecutionSessionID(req, opts)
+	if sessionID == "" && xaiRequiresIsolatedConversation(baseModel) {
+		sessionID = uuid.NewString()
+	}
 	if sessionID != "" {
 		body, _ = sjson.SetBytes(body, "prompt_cache_key", sessionID)
 	}
@@ -925,6 +930,10 @@ func xaiExecutionSessionID(req cliproxyexecutor.Request, opts cliproxyexecutor.O
 	return ""
 }
 
+func xaiRequiresIsolatedConversation(model string) bool {
+	return strings.HasPrefix(strings.ToLower(strings.TrimSpace(model)), xaiComposerModelPrefix)
+}
+
 func xaiImageEndpointPath(opts cliproxyexecutor.Options) string {
 	if opts.SourceFormat.String() != xaiImageHandlerType {
 		return ""
diff --git a/internal/runtime/executor/xai_executor_test.go b/internal/runtime/executor/xai_executor_test.go
index 8ed24fe9c..5e7b371a2 100644
--- a/internal/runtime/executor/xai_executor_test.go
+++ b/internal/runtime/executor/xai_executor_test.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/uuid"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
 	_ "github.com/router-for-me/CLIProxyAPI/v7/internal/translator"
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v7/sdk/cliproxy/auth"
@@ -159,6 +160,100 @@ func TestXAIExecutorExecuteShapesResponsesRequest(t *testing.T) {
 	}
 }
 
+func TestXAIExecutorComposerSessionIsolation(t *testing.T) {
+	exec := NewXAIExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{
+		Provider: "xai",
+		Metadata: map[string]any{"access_token": "xai-token"},
+	}
+
+	tests := []struct {
+		name          string
+		model         string
+		payload       []byte
+		wantGenerated bool
+		wantSession   string
+	}{
+		{
+			name:          "composer_generates_fresh_session",
+			model:         "grok-composer-2.5-fast",
+			payload:       []byte(`{"model":"grok-composer-2.5-fast","input":"hello"}`),
+			wantGenerated: true,
+		},
+		{
+			name:    "grok_build_stays_stateless_without_session",
+			model:   "grok-build-0.1",
+			payload: []byte(`{"model":"grok-build-0.1","input":"hello"}`),
+		},
+		{
+			name:        "explicit_prompt_cache_key_is_preserved",
+			model:       "grok-composer-2.5-fast",
+			payload:     []byte(`{"model":"grok-composer-2.5-fast","prompt_cache_key":"client-session","input":"hello"}`),
+			wantSession: "client-session",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			prepared, err := exec.prepareResponsesRequest(context.Background(), cliproxyexecutor.Request{
+				Model:   tt.model,
+				Payload: tt.payload,
+			}, cliproxyexecutor.Options{
+				SourceFormat: sdktranslator.FormatOpenAIResponse,
+				Stream:       true,
+			}, true)
+			if err != nil {
+				t.Fatalf("prepareResponsesRequest() error = %v", err)
+			}
+
+			gotSession := prepared.sessionID
+			gotPromptCacheKey := gjson.GetBytes(prepared.body, "prompt_cache_key").String()
+			httpReq, errRequest := http.NewRequest(http.MethodPost, "https://example.test/responses", bytes.NewReader(prepared.body))
+			if errRequest != nil {
+				t.Fatalf("NewRequest() error = %v", errRequest)
+			}
+			applyXAIHeaders(httpReq, auth, "xai-token", true, gotSession)
+			gotGrokConvID := httpReq.Header.Get("x-grok-conv-id")
+
+			if tt.wantGenerated {
+				if _, errParse := uuid.Parse(gotSession); errParse != nil {
+					t.Fatalf("generated sessionID = %q, want UUID; body=%s", gotSession, string(prepared.body))
+				}
+				if gotPromptCacheKey != gotSession {
+					t.Fatalf("prompt_cache_key = %q, want sessionID %q; body=%s", gotPromptCacheKey, gotSession, string(prepared.body))
+				}
+				if gotGrokConvID != gotSession {
+					t.Fatalf("x-grok-conv-id = %q, want sessionID %q", gotGrokConvID, gotSession)
+				}
+				return
+			}
+
+			if tt.wantSession != "" {
+				if gotSession != tt.wantSession {
+					t.Fatalf("sessionID = %q, want %q", gotSession, tt.wantSession)
+				}
+				if gotPromptCacheKey != tt.wantSession {
+					t.Fatalf("prompt_cache_key = %q, want %q; body=%s", gotPromptCacheKey, tt.wantSession, string(prepared.body))
+				}
+				if gotGrokConvID != tt.wantSession {
+					t.Fatalf("x-grok-conv-id = %q, want %q", gotGrokConvID, tt.wantSession)
+				}
+				return
+			}
+
+			if gotSession != "" {
+				t.Fatalf("sessionID = %q, want empty", gotSession)
+			}
+			if gotPromptCacheKey != "" {
+				t.Fatalf("prompt_cache_key = %q, want empty; body=%s", gotPromptCacheKey, string(prepared.body))
+			}
+			if gotGrokConvID != "" {
+				t.Fatalf("x-grok-conv-id = %q, want empty", gotGrokConvID)
+			}
+		})
+	}
+}
+
 func TestXAIExecutorCompactUsesCompactEndpoint(t *testing.T) {
 	var gotPath string
 	var gotAuth string