The administration’s decision to end the contract with CGI reflects lingering unease over the performance of HealthCare.gov, even as officials have touted recent improvements and the rising numbers of Americans who have used the marketplace to sign up for health coverage that took effect Jan. 1.

The government is able to sever its relationship with CGI readily because the company’s contract period is set to run out at the end of February. Federal officials had the option of renewing it for another year and possibly extending it two more times, or not renewing it.

At the start of December, administration officials announced that the Web site was largely working for consumers who wanted to enroll in health plans. But the site continues to malfunction in other ways. For instance, it is not yet able to automatically enroll people eligible for Medicaid in states’ programs, compute exact amounts to be sent to insurers for their customers’ federal subsidies, and tabulate precisely how many consumers have paid for their insurance premiums and are therefore actually covered.