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Case study · Health tech · 2026 – Present

Coco.

A privacy-first mental-wellness app whose guardrails are the product — local-first data, one-tap erase, and an AI companion that is structurally incapable of the failures making headlines.

LiveIndependent build · Mental Wellness

Local-first

data stays on-device

Multi-layer

crisis + harm guardrails

One-tap

erase all data

Wellness

not therapy — by design

The problem

Demand for mental-health support is staggering and mostly unmet: over 1.1 billion people live with a mental disorder[5], and in the US alone, of 61.5M adults with a mental-health condition, nearly half received no treatment. Apps rushed into that gap — and then became the problem. Mozilla's review labelled mental-health apps the worst product category it has ever tested for privacy, with most top apps failing its bar[4]; the FTC fined BetterHelp for sharing mental-health data with advertisers; and a wave of AI "therapy" chatbots began drawing wrongful-death lawsuits and regulatory bans.

Coco was built for the world afterthat reckoning — where "just trust our cloud" and "our chatbot is basically a therapist" are no longer viable, legally or ethically.

Market & opportunity

$17.5B1

mental health apps market by 2030 (~14.6% CAGR)

1.1B+5

people living with a mental disorder globally

worst-in-class4

mental-health apps' privacy rating across the category

2 states6

banned AI therapy in 2025 (Nevada, Illinois)

The mental-health apps market is projected to roughly double from ~$7.5B in 2024 to ~$17.5B by 2030 (14.6% CAGR)[1]. But the more important 2026 story is the regulatory vise closing on AI-as-therapist: Nevada and then Illinois passed laws in 2025 prohibiting AI from independently providing therapy (Illinois' WOPR Act, fines to $10,000)[6]; the FTC opened a formal inquiry into AI companion chatbots in September 2025[7]; the APA issued a health advisory warning that generative-AI wellness chatbots lack validation and safety protocols[8]; and a Character.AI teen-suicide case reached a landmark settlement in early 2026[9].

Mental health apps market — 2024 vs 2030 projection (USD billions)[1]
2024
$7.5B
2030 (proj.)
$17.5B

The most instructive data point is a tombstone: Woebot — the most clinically rigorous, FDA-engaged consumer therapy chatbot — shut down its app in mid-2025 after ~$124M raised, because there is no regulatory pathway for an LLM that acts as a therapist[2]. Meanwhile the apps that thriveare wellness-positioned (Calm, Headspace) or privacy-credible (Wysa was one of only two apps to pass Mozilla's bar)[3][4]. Coco sits deliberately in that surviving quadrant.

Who it's for

People who want daily, low-stakes emotional support — a place to journal, breathe, track mood, and talk something through at 2am — but who are (rightly) unwilling to trust a cloud with their darkest entries. The wedge is the privacy- and safety-conscious user the category's scandals created.

Constraints

  • It must never position as therapy.That's now a legal third rail. Coco is explicitly a wellness companion: no diagnosis, no treatment claims, no clinician impersonation.
  • Sensitive data cannot sit in a breachable cloud. Mood, journal, and chat are the most exfiltration-damaging data a person can give an app. Default storage is on-device.
  • Crisis cannot wait on a network round-trip. If a user signals self-harm, the SOS path has to fire instantly, even offline.
  • The AI must refuse harm and resist jailbreaks— method questions, "ignore previous instructions," roleplay-as-clinician — without breaking character or leaking its prompt.

Architecture & what I built

Local-first by default

Mood logs, daily check-ins, journal entries (including voice journaling transcribed via Groq Whisper), and chat history all live in AsyncStorage on-device. Nothing syncs to a backend unless the user explicitly exports. A single "Erase all my data" action clears every key. Firebase is used for auth only — its ID token authenticates the Groq proxy; no user content is stored there.

The guardrail stack (the actual product)

The AI companion runs on Groq (Llama 3.3 70B) behind a Vercel Edge Function, wrapped in layers that are the real engineering:

  • A constraining system prompt — warm, reflective, plain language; explicitly not a therapist; refuses diagnosis, medication advice, self-harm and eating-disorder methods; never claims to remember past sessions.
  • Two-tier crisis detection — a server-side regex bank plus a smaller client-side bank so the SOS banner appears before the server even responds. Crisis replies acknowledge, validate, steer toward a human or hotline, and avoid probing method/intent questions; minors are nudged to a trusted adult too.
  • A hard-refusal layer— harmful-intent and prompt-injection patterns (method-of-harm questions, "developer mode," jailbreak attempts) return a safe standard reply plus SOS resources, while staying in character.
  • Cost & abuse controls — history trimmed to the last 16 turns, each message clamped to 4 KB, soft per-identity rate limiting, and provider errors never leaked to the client.

The supporting toolkit

Around the companion: a 5-point mood tracker with trends, daily gratitude/feeling check-ins with streaks, free-form and voice journaling, Reanimated-4 breathing visualisations, a 5-4-3-2-1 grounding guide, sleep and meditation audio, a curated SOS/hotline directory (988, Crisis Text Line, Childline, Befrienders), a therapist/places directory, and peer-support community circles that run posts through a moderation endpoint before publishing.

Trade-offs

  • Local-first over cloud sync.No effortless cross-device history or server-side analytics — but no breach surface for the most sensitive data a user owns. For this category, that's the right side of the trade.
  • Refusal over helpfulness at the edges.The hard-refusal layer will sometimes decline a borderline-but-benign request. In mental-health AI, a false "no" is vastly cheaper than a false "here's how."
  • Wellness positioning over clinical claims.Coco gives up the credibility (and reimbursement) of a clinical product to stay off the regulatory third rail that just killed Woebot's consumer app.

Goals & what's next

Outcome

Coco is live on the App Store and Play Store, shipping a wellness companion whose design choices read like a direct response to the 2025–2026 headlines: data on-device, AI that refuses to be a therapist, crisis detection that fires before the network does. In a category where the growth-at-all-costs model is now a liability, Coco bets that trust is the product — and builds the architecture to back the claim.

Sources & references

  1. 1.Mental Health Apps Market To Reach $17.52 Billion By 2030 Grand View Research, 2025.
  2. 2.Woebot Health shuts down pioneering therapy chatbot, founder says AI moving faster than regulators STAT News, 2025.
  3. 3.Calm & Headspace Revenue and Usage Statistics Business of Apps, 2026.
  4. 4.Shady Mental Health Apps Inch Toward Privacy — But Many Still Siphon Personal Data Mozilla Foundation, 2023.
  5. 5.Over a billion people living with mental health conditions World Health Organization, 2025.
  6. 6.Gov. Pritzker signs legislation prohibiting AI therapy in Illinois (HB1806 / WOPR Act) Illinois IDFPR / Marketplace, 2025.
  7. 7.FTC Launches Inquiry into AI Chatbots Acting as Companions U.S. Federal Trade Commission, 2025.
  8. 8.Artificial intelligence, wellness apps alone cannot solve mental health crisis (Health Advisory) American Psychological Association, 2025.
  9. 9.Google and Character.AI agree to settle lawsuit linked to teen suicide JURIST, 2026.

Stack

Expo SDK 54
React Native
Expo Router
TypeScript
AsyncStorage
Vercel Edge Functions
Groq (Llama 3.3 70B)
Firebase Auth
Reanimated 4

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