backend/app/api/deps.py

@@ -0,0 +1,33 @@
+"""Shared API dependencies."""
+
+import uuid
+from typing import Annotated
+
+from fastapi import Depends, Header, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.db import get_session
+from app.models.user import User
+from app.services.user_service import get_user
+
+SessionDep = Annotated[AsyncSession, Depends(get_session)]
+
+
+async def get_current_user(
+    session: SessionDep,
+    x_user_id: Annotated[uuid.UUID | None, Header()] = None,
+) -> User:
+    """TEMPORARY pre-auth shim: identifies the caller via the ``X-User-Id``
+    header. Replaced by the AuthProvider (sessions/tokens) in the auth slice.
+    The assistant principal will also be minted here, scoped to its user."""
+    if x_user_id is None:
+        raise HTTPException(
+            status.HTTP_401_UNAUTHORIZED, "X-User-Id header required (pre-auth)"
+        )
+    user = await get_user(session, x_user_id)
+    if user is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "unknown user")
+    return user
+
+
+CurrentUser = Annotated[User, Depends(get_current_user)]

backend/app/api/v1/__init__.py

@@ -0,0 +1,10 @@
+"""Versioned API surface. Mounts under /api/v1."""
+
+from fastapi import APIRouter
+
+from app.api.v1 import persons, trees, users
+
+api_router = APIRouter(prefix="/api/v1")
+api_router.include_router(users.router)
+api_router.include_router(trees.router)
+api_router.include_router(persons.router)

backend/app/api/v1/persons.py

@@ -0,0 +1,43 @@
+import uuid
+
+from fastapi import APIRouter, status
+
+from app.api.deps import CurrentUser, SessionDep
+from app.schemas.person import PersonCreate, PersonRead
+from app.services import person_service, tree_service
+
+# Persons are nested under their tree (the tenant boundary).
+router = APIRouter(prefix="/trees", tags=["persons"])
+
+
+@router.post(
+    "/{tree_id}/persons",
+    response_model=PersonRead,
+    status_code=status.HTTP_201_CREATED,
+)
+async def create_person(
+    tree_id: uuid.UUID, data: PersonCreate, session: SessionDep, current: CurrentUser
+) -> PersonRead:
+    # get_tree enforces existence + view access; create_person enforces edit rights.
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    person = await person_service.create_person(
+        session,
+        actor=current,
+        tree=tree,
+        given=data.given,
+        surname=data.surname,
+        gender=data.gender,
+        is_living=data.is_living,
+        privacy_setting=data.privacy,
+        notes=data.notes,
+    )
+    return PersonRead.model_validate(person)
+
+
+@router.get("/{tree_id}/persons", response_model=list[PersonRead])
+async def list_persons(
+    tree_id: uuid.UUID, session: SessionDep, current: CurrentUser
+) -> list[PersonRead]:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    persons = await person_service.list_persons(session, viewer_id=current.id, tree=tree)
+    return [PersonRead.model_validate(p) for p in persons]

backend/app/api/v1/trees.py

@@ -0,0 +1,33 @@
+import uuid
+
+from fastapi import APIRouter, status
+
+from app.api.deps import CurrentUser, SessionDep
+from app.schemas.tree import TreeCreate, TreeRead
+from app.services import tree_service
+
+router = APIRouter(prefix="/trees", tags=["trees"])
+
+
+@router.post("", response_model=TreeRead, status_code=status.HTTP_201_CREATED)
+async def create_tree(data: TreeCreate, session: SessionDep, current: CurrentUser) -> TreeRead:
+    tree = await tree_service.create_tree(
+        session,
+        owner=current,
+        name=data.name,
+        description=data.description,
+        visibility=data.visibility,
+    )
+    return TreeRead.model_validate(tree)
+
+
+@router.get("", response_model=list[TreeRead])
+async def list_my_trees(session: SessionDep, current: CurrentUser) -> list[TreeRead]:
+    trees = await tree_service.list_trees_for_user(session, user=current)
+    return [TreeRead.model_validate(t) for t in trees]
+
+
+@router.get("/{tree_id}", response_model=TreeRead)
+async def get_tree(tree_id: uuid.UUID, session: SessionDep, current: CurrentUser) -> TreeRead:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    return TreeRead.model_validate(tree)

backend/app/api/v1/users.py

@@ -0,0 +1,21 @@
+from fastapi import APIRouter, status
+
+from app.api.deps import CurrentUser, SessionDep
+from app.schemas.user import UserCreate, UserRead
+from app.services import user_service
+
+router = APIRouter(prefix="/users", tags=["users"])
+
+
+@router.post("", response_model=UserRead, status_code=status.HTTP_201_CREATED)
+async def create_user(data: UserCreate, session: SessionDep) -> UserRead:
+    # Open dev bootstrap until the auth slice; lets us create tree owners.
+    user = await user_service.create_user(
+        session, email=data.email, display_name=data.display_name
+    )
+    return UserRead.model_validate(user)
+
+
+@router.get("/me", response_model=UserRead)
+async def read_me(current: CurrentUser) -> UserRead:
+    return UserRead.model_validate(current)

backend/app/core/db.py

@@ -1,22 +1,43 @@
-"""Async database engine.
+"""Async database engine, session factory, and the FastAPI session dependency.
 
-A single lazily-created async engine for the process. The repository layer
-(coming with the data model) will build sessions on top of this; for now it
-backs the readiness probe.
+The repository layer builds on ``get_session``; ``get_engine`` also backs the
+readiness probe. Everything is lazy so importing the app never opens a
+connection (important for tests and for ``--help``-style invocations).
 """
 
-from sqlalchemy.ext.asyncio import AsyncEngine, create_async_engine
+from collections.abc import AsyncIterator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncEngine,
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
 
 from app.core.config import get_settings
 
 _engine: AsyncEngine | None = None
+_sessionmaker: async_sessionmaker[AsyncSession] | None = None
 
 
 def get_engine() -> AsyncEngine:
     global _engine
     if _engine is None:
-        _engine = create_async_engine(
-            get_settings().database_url,
-            pool_pre_ping=True,
-        )
+        _engine = create_async_engine(get_settings().database_url, pool_pre_ping=True)
     return _engine
+
+
+def get_sessionmaker() -> async_sessionmaker[AsyncSession]:
+    global _sessionmaker
+    if _sessionmaker is None:
+        _sessionmaker = async_sessionmaker(
+            get_engine(), expire_on_commit=False, class_=AsyncSession
+        )
+    return _sessionmaker
+
+
+async def get_session() -> AsyncIterator[AsyncSession]:
+    """FastAPI dependency. One session per request; commits are explicit in the
+    service layer."""
+    async with get_sessionmaker()() as session:
+        yield session

backend/app/main.py

@@ -1,14 +1,31 @@
 """FastAPI application entrypoint.
 
-Thin by design: wire settings and routers, expose the OpenAPI contract. All
-domain logic lives in the service layer (added with the data model). The
-versioned API will mount under ``/api/v1``; health probes stay at the root.
+Thin by design: wire settings, routers, and error handling, and expose the
+OpenAPI contract. All domain logic lives in the service layer; the privacy
+engine is the single enforcement point for reads.
 """
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
+from fastapi.responses import JSONResponse
 
 from app.api.health import router as health_router
+from app.api.v1 import api_router
 from app.core.config import get_settings
+from app.services.exceptions import Conflict, Forbidden, NotFound
+
+
+def _register_error_handlers(app: FastAPI) -> None:
+    @app.exception_handler(NotFound)
+    async def _not_found(request: Request, exc: NotFound) -> JSONResponse:
+        return JSONResponse(status_code=404, content={"detail": str(exc) or "not found"})
+
+    @app.exception_handler(Forbidden)
+    async def _forbidden(request: Request, exc: Forbidden) -> JSONResponse:
+        return JSONResponse(status_code=403, content={"detail": str(exc) or "forbidden"})
+
+    @app.exception_handler(Conflict)
+    async def _conflict(request: Request, exc: Conflict) -> JSONResponse:
+        return JSONResponse(status_code=409, content={"detail": str(exc) or "conflict"})
 
 
 def create_app() -> FastAPI:
@@ -19,6 +36,8 @@ def create_app() -> FastAPI:
         description="Provenance API — family and land provenance.",
     )
     app.include_router(health_router)
+    app.include_router(api_router)
+    _register_error_handlers(app)
     return app
 
 

backend/app/repositories/base.py

@@ -0,0 +1,40 @@
+"""Thin data-access layer over SQLAlchemy. No business rules live here — the
+service layer owns those (and the privacy engine). The repository only knows how
+to fetch and stage rows, transparently excluding soft-deleted ones.
+"""
+
+from typing import Any
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+
+class BaseRepository:
+    def __init__(self, session: AsyncSession, model: type) -> None:
+        self.session = session
+        self.model = model
+
+    def _exclude_deleted(self, stmt):
+        if hasattr(self.model, "deleted_at"):
+            stmt = stmt.where(self.model.deleted_at.is_(None))
+        return stmt
+
+    async def get(self, id_: Any, *, include_deleted: bool = False):
+        stmt = select(self.model).where(self.model.id == id_)
+        if not include_deleted:
+            stmt = self._exclude_deleted(stmt)
+        return (await self.session.execute(stmt)).scalar_one_or_none()
+
+    async def list(self, *conditions, include_deleted: bool = False, order_by=None):
+        stmt = select(self.model)
+        for condition in conditions:
+            stmt = stmt.where(condition)
+        if not include_deleted:
+            stmt = self._exclude_deleted(stmt)
+        if order_by is not None:
+            stmt = stmt.order_by(order_by)
+        return list((await self.session.execute(stmt)).scalars().all())
+
+    def add(self, obj):
+        self.session.add(obj)
+        return obj

backend/app/schemas/person.py

@@ -0,0 +1,27 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+from app.models.enums import PersonPrivacy
+
+
+class PersonCreate(BaseModel):
+    given: str | None = None
+    surname: str | None = None
+    gender: str | None = None
+    is_living: bool | None = None
+    privacy: PersonPrivacy = PersonPrivacy.inherit
+    notes: str | None = None
+
+
+class PersonRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    tree_id: uuid.UUID
+    primary_name: str | None = None
+    gender: str | None
+    is_living: bool | None
+    privacy: PersonPrivacy
+    created_at: datetime

backend/app/schemas/tree.py

@@ -0,0 +1,23 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+from app.models.enums import TreeVisibility
+
+
+class TreeCreate(BaseModel):
+    name: str
+    description: str | None = None
+    visibility: TreeVisibility = TreeVisibility.private
+
+
+class TreeRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    name: str
+    description: str | None
+    visibility: TreeVisibility
+    owner_id: uuid.UUID
+    created_at: datetime

backend/app/schemas/user.py

@@ -0,0 +1,22 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+# Note: email is a plain str for now (no email-validator dependency yet); the
+# auth slice can tighten this to EmailStr.
+
+
+class UserCreate(BaseModel):
+    email: str
+    display_name: str | None = None
+
+
+class UserRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    email: str
+    display_name: str | None
+    email_verified_at: datetime | None
+    created_at: datetime

backend/app/services/audit.py

@@ -0,0 +1,37 @@
+"""Audit logging. Every mutation records an append-only AuditEntry attributing
+the change to a User (or the assistant principal acting for a User). Staged on
+the session; the caller commits as part of its unit of work.
+"""
+
+import uuid
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.audit import AuditEntry
+from app.models.enums import AuditActorType
+
+
+def record_audit(
+    session: AsyncSession,
+    *,
+    action: str,
+    entity_type: str,
+    entity_id: uuid.UUID | None = None,
+    tree_id: uuid.UUID | None = None,
+    actor_user_id: uuid.UUID | None = None,
+    actor_type: AuditActorType = AuditActorType.user,
+    before: dict | None = None,
+    after: dict | None = None,
+) -> AuditEntry:
+    entry = AuditEntry(
+        action=action,
+        entity_type=entity_type,
+        entity_id=entity_id,
+        tree_id=tree_id,
+        actor_user_id=actor_user_id,
+        actor_type=actor_type,
+        before=before,
+        after=after,
+    )
+    session.add(entry)
+    return entry

backend/app/services/exceptions.py

@@ -0,0 +1,18 @@
+"""Domain errors. The API layer maps these to HTTP status codes so services
+stay transport-agnostic."""
+
+
+class DomainError(Exception):
+    """Base for domain-level errors."""
+
+
+class NotFound(DomainError):
+    """Requested entity does not exist (or is soft-deleted / not visible)."""
+
+
+class Forbidden(DomainError):
+    """Caller lacks the required role for this action."""
+
+
+class Conflict(DomainError):
+    """Operation conflicts with current state (e.g. duplicate email)."""

backend/app/services/person_service.py

@@ -0,0 +1,113 @@
+"""Person service. Writes require editor rights on the tree; reads run every
+person through the privacy engine. Each returned Person gets a transient
+``primary_name`` for display (not persisted).
+"""
+
+import uuid
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.enums import PersonPrivacy
+from app.models.person import Name, Person
+from app.models.tree import Tree
+from app.models.user import User
+from app.services import privacy
+from app.services.audit import record_audit
+from app.services.exceptions import Forbidden
+from app.services.privacy import Visibility
+
+
+def _format_name(name: Name) -> str | None:
+    parts = [name.given, name.surname]
+    joined = " ".join(p for p in parts if p)
+    return joined or name.display_name
+
+
+async def _attach_primary_name(session: AsyncSession, person: Person) -> None:
+    stmt = (
+        select(Name)
+        .where(Name.person_id == person.id, Name.deleted_at.is_(None))
+        .order_by(Name.is_primary.desc(), Name.sort_order)
+    )
+    name = (await session.execute(stmt)).scalars().first()
+    # Transient display attribute consumed by the PersonRead schema.
+    person.primary_name = _format_name(name) if name is not None else None
+
+
+async def create_person(
+    session: AsyncSession,
+    *,
+    actor: User,
+    tree: Tree,
+    given: str | None = None,
+    surname: str | None = None,
+    gender: str | None = None,
+    is_living: bool | None = None,
+    privacy_setting: PersonPrivacy = PersonPrivacy.inherit,
+    notes: str | None = None,
+) -> Person:
+    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
+        raise Forbidden("not an editor of this tree")
+
+    person = Person(
+        tree_id=tree.id,
+        gender=gender,
+        is_living=is_living,
+        privacy=privacy_setting,
+        notes=notes,
+    )
+    session.add(person)
+    await session.flush()  # assign person.id
+
+    if given or surname:
+        session.add(
+            Name(
+                tree_id=tree.id,
+                person_id=person.id,
+                name_type="birth",
+                given=given,
+                surname=surname,
+                is_primary=True,
+            )
+        )
+    record_audit(
+        session,
+        action="create",
+        entity_type="Person",
+        entity_id=person.id,
+        tree_id=tree.id,
+        actor_user_id=actor.id,
+        after={"given": given, "surname": surname},
+    )
+    await session.commit()
+    await session.refresh(person)
+    await _attach_primary_name(session, person)
+    return person
+
+
+async def list_persons(
+    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree
+) -> list[Person]:
+    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
+        raise Forbidden("not permitted to view this tree")
+
+    stmt = (
+        select(Person)
+        .where(Person.tree_id == tree.id, Person.deleted_at.is_(None))
+        .order_by(Person.created_at)
+    )
+    persons = list((await session.execute(stmt)).scalars().all())
+
+    visible: list[Person] = []
+    for person in persons:
+        if (
+            await privacy.person_visibility(
+                session, user_id=viewer_id, tree=tree, person=person
+            )
+            == Visibility.hidden
+        ):
+            continue
+        await _attach_primary_name(session, person)
+        visible.append(person)
+    return visible

backend/app/services/privacy.py

@@ -0,0 +1,62 @@
+"""The privacy engine — the single enforcement point for visibility.
+
+INVARIANT (CLAUDE.md #2): every read path resolves visibility here. Do not add a
+query path that returns rows to a caller without first passing through this
+module. Effective visibility is a function of the viewer's role on the tree, the
+tree's visibility, the per-person override, and (Phase 2) living-person status.
+"""
+
+import enum
+import uuid
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.enums import MembershipRole, PersonPrivacy, TreeVisibility
+from app.models.person import Person
+from app.models.tree import Tree, TreeMembership
+
+
+class Visibility(enum.StrEnum):
+    full = "full"
+    redacted = "redacted"
+    hidden = "hidden"
+
+
+async def get_membership_role(
+    session: AsyncSession, user_id: uuid.UUID | None, tree_id: uuid.UUID
+) -> MembershipRole | None:
+    if user_id is None:
+        return None
+    stmt = select(TreeMembership.role).where(
+        TreeMembership.tree_id == tree_id,
+        TreeMembership.user_id == user_id,
+    )
+    return (await session.execute(stmt)).scalar_one_or_none()
+
+
+async def can_view_tree(session: AsyncSession, *, user_id: uuid.UUID | None, tree: Tree) -> bool:
+    if tree.deleted_at is not None:
+        return False
+    if await get_membership_role(session, user_id, tree.id) is not None:
+        return True
+    return tree.visibility in (TreeVisibility.public, TreeVisibility.unlisted)
+
+
+async def can_edit_tree(session: AsyncSession, *, user_id: uuid.UUID | None, tree: Tree) -> bool:
+    role = await get_membership_role(session, user_id, tree.id)
+    return role in (MembershipRole.owner, MembershipRole.editor)
+
+
+async def person_visibility(
+    session: AsyncSession, *, user_id: uuid.UUID | None, tree: Tree, person: Person
+) -> Visibility:
+    if not await can_view_tree(session, user_id=user_id, tree=tree):
+        return Visibility.hidden
+    if await get_membership_role(session, user_id, tree.id) is not None:
+        return Visibility.full
+    # Non-member viewing a public/unlisted tree:
+    if person.privacy == PersonPrivacy.private:
+        return Visibility.hidden
+    # TODO(Phase 2): redact living people for non-members (ARCHITECTURE §6).
+    return Visibility.full

backend/app/services/tree_service.py

@@ -0,0 +1,61 @@
+"""Tree service. Creating a tree also creates the owner's TreeMembership (the
+authorization basis) and an audit entry. Reads go through the privacy engine.
+"""
+
+import uuid
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.enums import MembershipRole, TreeVisibility
+from app.models.tree import Tree, TreeMembership
+from app.models.user import User
+from app.repositories.base import BaseRepository
+from app.services import privacy
+from app.services.audit import record_audit
+from app.services.exceptions import Forbidden, NotFound
+
+
+async def create_tree(
+    session: AsyncSession,
+    *,
+    owner: User,
+    name: str,
+    description: str | None = None,
+    visibility: TreeVisibility = TreeVisibility.private,
+) -> Tree:
+    tree = Tree(owner_id=owner.id, name=name, description=description, visibility=visibility)
+    session.add(tree)
+    await session.flush()  # assign tree.id
+    session.add(TreeMembership(tree_id=tree.id, user_id=owner.id, role=MembershipRole.owner))
+    record_audit(
+        session,
+        action="create",
+        entity_type="Tree",
+        entity_id=tree.id,
+        tree_id=tree.id,
+        actor_user_id=owner.id,
+        after={"name": name, "visibility": visibility.value},
+    )
+    await session.commit()
+    await session.refresh(tree)
+    return tree
+
+
+async def list_trees_for_user(session: AsyncSession, *, user: User) -> list[Tree]:
+    stmt = (
+        select(Tree)
+        .join(TreeMembership, TreeMembership.tree_id == Tree.id)
+        .where(TreeMembership.user_id == user.id, Tree.deleted_at.is_(None))
+        .order_by(Tree.created_at)
+    )
+    return list((await session.execute(stmt)).scalars().all())
+
+
+async def get_tree(session: AsyncSession, *, viewer_id: uuid.UUID, tree_id: uuid.UUID) -> Tree:
+    tree = await BaseRepository(session, Tree).get(tree_id)
+    if tree is None:
+        raise NotFound("tree not found")
+    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
+        raise Forbidden("not permitted to view this tree")
+    return tree

backend/app/services/user_service.py

@@ -0,0 +1,44 @@
+"""User service. Account creation here is a temporary, open dev bootstrap so we
+can create tree owners before the auth slice exists; the auth slice replaces it
+with the AuthProvider (password/OIDC/social) and proper verification.
+"""
+
+import uuid
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.user import User
+from app.repositories.base import BaseRepository
+from app.services.audit import record_audit
+from app.services.exceptions import Conflict
+
+
+async def create_user(
+    session: AsyncSession, *, email: str, display_name: str | None = None
+) -> User:
+    email = email.strip().lower()
+    existing = (
+        await session.execute(select(User).where(User.email == email))
+    ).scalar_one_or_none()
+    if existing is not None:
+        raise Conflict("email already registered")
+
+    user = User(email=email, display_name=display_name)
+    session.add(user)
+    await session.flush()  # assign user.id
+    record_audit(
+        session,
+        action="create",
+        entity_type="User",
+        entity_id=user.id,
+        actor_user_id=user.id,
+        after={"email": email},
+    )
+    await session.commit()
+    await session.refresh(user)
+    return user
+
+
+async def get_user(session: AsyncSession, user_id: uuid.UUID) -> User | None:
+    return await BaseRepository(session, User).get(user_id)