diff --git a/apps/backend/internal/agent/runtime/lifecycle/container.go b/apps/backend/internal/agent/runtime/lifecycle/container.go
index a0a983b859..551da4beb8 100644
--- a/apps/backend/internal/agent/runtime/lifecycle/container.go
+++ b/apps/backend/internal/agent/runtime/lifecycle/container.go
@@ -97,6 +97,8 @@ func namespacesMCPToolsByServerFromAgent(agent agents.Agent) bool {
 	return rt != nil && rt.NamespacesMCPToolsByServer
 }
 
+// buildContainerCreateInstanceRequest builds the agentctl request for a fresh
+// Docker instance, including the task and session identity used by MCP tools.
 func buildContainerCreateInstanceRequest(
 	config ContainerConfig,
 	agentType string,
@@ -116,6 +118,7 @@ func buildContainerCreateInstanceRequest(
 		AutoStart:                  false,
 		McpServers:                 config.McpServers,
 		SessionID:                  config.SessionID,
+		TaskID:                     config.TaskID,
 		DisableAskQuestion:         disableAskQuestion,
 		AssumeMcpSse:               assumeMcpSse,
 		AssumeMcpHttp:              assumeMcpHttp,
diff --git a/apps/backend/internal/agent/runtime/lifecycle/container_create_instance_test.go b/apps/backend/internal/agent/runtime/lifecycle/container_create_instance_test.go
new file mode 100644
index 0000000000..43df9e1246
--- /dev/null
+++ b/apps/backend/internal/agent/runtime/lifecycle/container_create_instance_test.go
@@ -0,0 +1,18 @@
+package lifecycle
+
+import "testing"
+
+// TestBuildContainerCreateInstanceRequestForwardsTaskAndSession verifies that a
+// fresh Docker request preserves the identity required by task-bound MCP tools.
+func TestBuildContainerCreateInstanceRequestForwardsTaskAndSession(t *testing.T) {
+	config := ContainerConfig{TaskID: "task-123", SessionID: "session-456"}
+
+	req := buildContainerCreateInstanceRequest(config, "claude-acp", false, false, false, false, nil)
+
+	if req.TaskID != "task-123" {
+		t.Fatalf("TaskID = %q, want %q", req.TaskID, "task-123")
+	}
+	if req.SessionID != "session-456" {
+		t.Fatalf("SessionID = %q, want %q", req.SessionID, "session-456")
+	}
+}