# Phase 16: Multi-User Data Model - Discussion Log

> **Audit trail only.** Do not use as input to planning, research, or execution agents.
> Decisions are captured in CONTEXT.md — this log preserves the alternatives considered.

**Date:** 2026-04-05
**Phase:** 16-multi-user-data-model
**Areas discussed:** User ID Representation, Existing Data Migration, Category Uniqueness, Settings Scope, API Key Ownership
**Mode:** --auto --batch (all decisions auto-selected)

---

## User ID Representation

| Option | Description | Selected |
|--------|-------------|----------|
| Local users table with integer ID | Thin table mapping Logto sub to auto-increment integer, all FKs use integer | ✓ |
| Logto sub string directly | Store Logto sub (string UUID) as FK on every entity table | |
| Mapping table without FK | Store logtoSub on entities, join manually | |

**User's choice:** Local users table with integer ID (auto-selected)
**Notes:** Integer FKs are more efficient for joins. Thin table auto-creates on first OIDC login.

---

## Existing Data Migration

| Option | Description | Selected |
|--------|-------------|----------|
| Migration assigns all rows to user ID 1 | Add userId column, set all existing data to first user | ✓ |
| Prompt for Logto sub during migration | Interactive script asks for the Logto user ID | |
| Leave data unassigned until claimed | Nullable userId, user claims data on first login | |

**User's choice:** Migration assigns all rows to user ID 1 (auto-selected)
**Notes:** Single existing user, simplest approach.

---

## Category Uniqueness

| Option | Description | Selected |
|--------|-------------|----------|
| Composite unique (userId, name) | Each user has independent category namespace | ✓ |
| Global unique (current) | All users share one category namespace | |

**User's choice:** Composite unique (userId, name) (auto-selected)
**Notes:** Required by MULTI-03.

---

## Settings Scope

| Option | Description | Selected |
|--------|-------------|----------|
| Composite PK (userId, key) | Each user has own settings | ✓ |
| Separate user_settings table | New table for per-user settings | |

**User's choice:** Composite PK (userId, key) (auto-selected)
**Notes:** Required by MULTI-06. Minimal schema change.

---

## API Key Ownership

| Option | Description | Selected |
|--------|-------------|----------|
| userId column on apiKeys | API keys belong to creating user, middleware resolves user scope | ✓ |
| Shared API keys (no user scope) | API keys grant access to all data | |

**User's choice:** userId column on apiKeys (auto-selected)
**Notes:** Required by MULTI-05 for MCP tool scoping.

---

## Claude's Discretion

- Migration SQL approach
- userId scoping helper vs inline where clauses
- Default category creation strategy
- Thread resolution cross-user checks
- Service change ordering

## Deferred Ideas

None — discussion stayed within phase scope