Sehaty

A personal health agent: training, nutrition and weight, reachable from an AI assistant over MCP (Telegram planned). Multi-person, and built so that one person's health data is never reachable from another's session.

Status: early. The MCP server, encrypted storage and exercise catalog work and are tested. Voice notes, meal photos, Telegram, the dashboard and AI-assisted planning are not built yet. See Status.

Why it exists

Health data is about as personal as data gets, and most fitness apps answer "where does this live?" with "our servers". Sehaty answers "a machine you control, encrypted at rest, with the key somewhere the backup can't reach."

Design

Deterministic tools, not a chatbot. Sets, reps, rest and prescriptions come from code, not from a model deciding each time. An assistant is a good interface; it is not a good place to keep the number of reps you did.

Isolation before encryption. Every query is filtered by profile_id in a single data access layer nothing bypasses. Encryption protects a stolen disk; isolation protects you from a bug.

Encrypted at rest, in layers that do different jobs:

layer	cipher	protects	authenticated
database file (incl. WAL)	Adiantum, via ncruces/go-sqlite3	every table	no — length preserving
document bodies	AES-256-GCM, AAD-bound to profile/key/version	clinical + prescriptive text	yes
media blobs	AES-256-GCM, AAD-bound to profile/kind/hash	photos, voice notes	yes

SEHATY_KEY is a master; each layer gets an independent HKDF-SHA256 subkey, so no two ciphers ever run under the same bytes.

What this does not defend against. The key is in the server's environment, so a running server can always decrypt. This protects backups, a stolen disk and a copied image. It does not protect against someone who has compromised the running process. That limit is the price of Sehaty being able to answer you without you typing a passphrase.

Quick start

The exercise dataset is a submodule, so clone recursively:

git clone --recurse-submodules https://github.com/rakasatria/sehaty.git
cd sehaty
go build -o sehaty ./cmd/sehaty

Generate a key and keep a copy somewhere that is not the server:

openssl rand -base64 32 | tr -d '\n' > /etc/sehaty/key
chmod 0440 /etc/sehaty/key

Losing this key means losing every encrypted record. There is no recovery path, and that is the point.

SEHATY_KEY_FILE=/etc/sehaty/key \
SEHATY_DATA=/var/lib/sehaty \
SEHATY_EXERCISES=third_party/exercises-dataset/data/exercises.json \
./sehaty

Then point an MCP client at http://127.0.0.1:8765/mcp.

Configuration

variable	default	notes
SEHATY_KEY_FILE	—	path to the base64 master key. Preferred over SEHATY_KEY
SEHATY_KEY	—	the key itself. Visible in docker inspect and ps — use the file
SEHATY_DATA	/var/lib/sehaty	root of all mutable state
SEHATY_DB	$SEHATY_DATA/sehaty.db	encrypted SQLite
SEHATY_MEDIA	$SEHATY_DATA/media	blobs, <profile>/<kind>/<ab>/<sha256>
SEHATY_EXERCISES	/opt/sehaty/exercises.json	read-only dataset
SEHATY_PASSPHRASE	—	gates registration. Unset means registration closed
SEHATY_MCP_HOST	127.0.0.1	MCP is a tool-execution surface — do not publish it
SEHATY_MCP_PORT	8765

The key must live outside SEHATY_DATA. Sehaty refuses to start otherwise: a key inside the directory you back up travels in the same archive as the ciphertext it unlocks. Note that this check cannot see your backup tool — if you image the whole machine, put the key somewhere that image does not reach.

Tools

register · list_profiles · get_profile · plan_session · find_exercises · log_set · log_cardio · log_weight · progress · cardio_protocol

Status

Works: MCP server, encrypted storage, profile isolation, training/cardio/weight/food logging, versioned encrypted documents, exercise catalog with equipment filtering, media store.

Not built: AI-assisted planning, difficulty ratings for the full dataset (only a handful are rated, so difficulty filtering is effectively inert), voice notes, meal photos, Bahasa Indonesia, Telegram, dashboard.

Safety

Sehaty is not a doctor and does not diagnose. It will not set a calorie target below a safe floor, and prescriptions from a real clinician are stored as documents rather than second-guessed.

Credits

Exercise data from hasaneyldrm/exercises-dataset (MIT, © Hasan Emir Yıldırım) — 1,324 exercises.

Licence

MIT — see LICENSE.