# ADR-0002: Monorepo with Bun workspaces

• Status: accepted
• Date: 2026-04-23

# Context

Three services share a protocol (@bdi/contracts), a signing profile (@bdi/crypto), a policy engine (@bdi/policy), and observability primitives. Independent repositories would make protocol changes expensive (multi-repo PRs) and encourage drift.

# Decision

Use a single repository with Bun workspaces. Each service and each shared package is its own workspace with @bdi/<name>. The root tsconfig.base.json declares path mappings so services resolve @bdi/kernel directly to the source — no build step needed in dev.

# Consequences

• Protocol changes are a single PR; incompatibilities caught at compile.
• Shared CI pipeline amortises setup cost.
• Deploying one service is independent (each has its own Dockerfile target and own versioning); co-location does not imply coupled deploy.
• Drawback: repo size grows; partial clones are required for large contributor deployments (not an issue at the current scale).

# Alternatives considered

• Polyrepo with git submodules: high friction, easy to fall out of sync. Rejected.
• Polyrepo with private registry: forces contract changes to flow through a release cycle. Rejected for MVP; revisit after 1.0.