# ADR-0007: `project_id` in the data model from day one

**Status:** Accepted (2026-08-08)

## Context

The design doc placed multi-project support in the final build phase. But `get_rules(project_id,
agent_type)` already carries a project identifier in its phase-1 signature, and retrofitting
multi-tenancy after five subsystems exist means migrating rules, audit, memory collections,
permissions, and the panel simultaneously.

## Decision

Every table and every tool signature carries **`project_id` from phase 1**. Memory collections are
namespaced per project (`<project>_sessions`). The Web Panel and CLI default to a single project so
the v1 user experience is unchanged.

## Consequences

- Near-zero upfront cost — the identifier was already in the API design.
- Phase 9 becomes exposing a project switcher rather than performing a cross-subsystem migration.
- Every query must be project-scoped from the start; a missing `WHERE project_id = ?` is a
  correctness bug, so this belongs in the review checklist.