In addition to receiving enhanced usual care as described below, a series of 25 standardized outgoing Caring Contacts text messages will be sent to participants randomized to the CC2 intervention arm through our online texting platform. To remind participants that they can respond, the outgoing texts will periodically invite replies in a non-demanding way, e.g., "Hope you're doing well this week, Anna. Feel free to text me back if you feel like it, I'm here for you." Responses to CC2 participant replies will be unscripted and individually tailored.

In addition to receiving enhanced usual care as described below, CC1 participants will be sent 25 caring texts, such as "Even though know we do not personally know each other, we truly value your wellbeing and are thinking of you. If you'd like to connect with someone, feel free to call or text 988 anytime - their team would be happy to hear from you." CC1 participants will not be able to reply to the texts and the online texting platform will block incoming messages. This will be clearly communicated to CC1 participants during the informed consent process and they will be asked to sign off on understanding this and other key points before enrolling in the study.

Participants randomized to the UC arm will receive best available usual care from the health system, such as standardized clinical assessments, the safety planning intervention or other intervention(s), appropriate referrals and/or medication management through a system wide electronic health record system-assisted suicide care clinical workflow. Usual care will vary based on patient clinical needs, availability of providers/staff, and provider clinical judgment. Following study enrollment, all participants will be given a list of resources, offered a warm hand-off to 988, and encouragement to call or text 988 as needed. During the baseline survey, participants will have the opportunity to opt into a call from the follow-up team to develop or revise a safety plan.

Text message version of Motto's Caring Contacts intervention. The study will compare two versions of text-based Caring Contacts: two-way messages, to which participants can respond to receive text-based support from follow-up specialists, and one-way text messages, to which participants cannot respond.

Measured using the Harkavy-Asnis Suicide Scale (HASS) Active Suicidal Behavior Sub-Scale. The HASS has been validated for self-report, with strong psychometric properties in adolescents and adults. This measure asks about the frequency of suicide attempt planning, and actual and aborted/interrupted suicide attempts. Participants respond using the Likert scale response options used by Asarnow et al.'s validation study, modified to fit the survey time period (past six months at baseline/12-month outcome surveys, and past 3 months for 3- and 6-month outcome surveys). Each HASS sub-scale is scored separately by summing the response values. Scores on the Active Suicidal Behavior Sub-Scale range from 0 - 20, with higher scores corresponding to higher suicide risk. The primary outcome will be the cumulative risk of suicidal behavior assessed using area under the curve of the HASS scores over the 12-month study period.

Suicide attempts will be measured using the Columbia Suicide Severity Rating Scale (C-SSRS), which is valid for adolescents and adults.

Thwarted belongingness will be measured using the 15-item version of the Interpersonal Needs Questionnaire.

The 15-item version of the Interpersonal Needs Questionnaire (INQ15) is a validated tool to measure both perceived burdensomeness (PB) (6 items, scores range from 6 to 42) and thwarted belongingness (TB) (9 items; scores range from 9 to 63), which are related to desire for suicide. Individuals provide a self-report response to each of 15 items using a Likert scale ranging from 1 (Not at all true for me) to 7 (Very true for me). The appropriate items are reverse coded, and items are summed to calculate the TB and PB subscale scores with higher scores indicating greater TB and PB. Clinical Cutoff scores predicting desire for death are 35 or greater for TB and 19 or greater for PB. Clinical cutoff scores predicting desire for suicide are 50 or greater for TB and 30 or greater for PB.