Fully Closed Loop at Home (FCL@Home)

Inclusion Criteria: Age either 14-17, 18-25, or 26-60 years at time of consent. Clinical diagnosis of T1D, based on investigator assessment, of at least 1 year duration. HbA1c either <8.0 or 8.0-12.0% at time of consent. Currently using insulin for at least 6 months. Willingness to follow the protocol and sign the informed consent (and assent as applicable). Living with one or more parent/guardian or supportive companions knowledgeable about emergency procedures for severe hypoglycemia and able to contact emergency services and study staff. For females, not currently known to be pregnant or breastfeeding. If female and sexually active, must agree to use a form of contraception to prevent pregnancy while a participant in the study. A negative serum or urine pregnancy test will be required for all females of childbearing potential. Participants who become pregnant will be discontinued from the study. Also, participants who during the study develop and express the intention to become pregnant within the timespan of the study will be discontinued. Willingness to switch to use a commercially approved personal insulin (e.g., lispro or aspart, or biosimilar approved products) within the study pump as directed by the study team. Currently using an insulin pump for at least the prior 6 months. Any commercially approved pump, either open loop or hybrid closed loop may be used. Willingness to suspend use of any personal CGM other than Dexcom G6 once the DiAs system is in use. Participants may use their own Dexcom G6 during the study period. Willingness to use the study FCL system (CGM, pump, and phone) during the relevant study period. Willingness not to start any new non-insulin glucose-lowering agent during the course of the trial. Willingness to participate in all study procedures including the house/hotel session, exercise challenges (e.g., one hour per day during hotel), and to consume approximately 3 unannounced meals per day during the relevant portion of the supervised hotel session. Access to internet at home and willingness to upload data during the study as needed. Investigator has confidence that the participant can successfully operate all study devices and is capable of adhering to the protocol. Participant is proficient in reading and writing English. Exclusion Criteria: Plans to start a new non-insulin glucose-lowering agent (e.g., GLP-1 receptor agonists, Symlin, DPP-4 inhibitors, sulfonylureas). Participants may be on a stable dose of such an agent for at least the past month. Current use of an SGLT-2 or SGLT-1/2 inhibitor due to risk of euglycemic DKA. Hemophilia or any other bleeding disorder. History of severe hypoglycemic event with seizure or loss of consciousness in the last 12 months. History of DKA event in the last 12 months. History of chronic renal disease (CKD3b or 4) or currently on peritoneal or hemodialysis. History of adrenal insufficiency. Currently being treated for a seizure disorder. Hypothyroidism or hyperthyroidism that is not adequately treated. Coronary artery disease or other heart condition that would prevent participation in moderate intensity exercise. Use of oral or injectable steroids at the time of enrollment or within the last 4 weeks. Planned surgery during the study period. Known ongoing adhesive intolerance that is not well managed. A condition, which in the opinion of the investigator or designee, would put the participant or study at risk. Participation in another interventional trial at the time of enrollment. Participant does not have a direct supervisor involved in the conduct of the trial.