# Phase 03 – Rigid Frontend API & PBS Leak Containment (Junie PR Templates)

> Goal: **finish Phase 03 with JVM-like discipline** by making the **Backend (BE) the source of truth** and forcing the PBS Frontend (FE) to implement a **strict, minimal, canonical** contract (`frontend-api`).
>
> Strategy: **surgical PRs** that (1) stop PBS types from leaking, (2) replace stringy protocols with canonical models, and (3) make imports/exports/overloads deterministic across deps.

# Notes / Operating Rules (for Junie)

1. **BE is the source of truth**: `frontend-api` defines canonical models; FE conforms.
2. **No string protocols** across layers. Strings may exist only as *display/debug*.
3. **No FE implementation imports from other FE implementations**.
4. **No BE imports PBS modules** (hard boundary).
5. **Overload resolution is signature-based** (arity alone is not valid).

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## PR-03.07 — Phase 03 cleanup: remove legacy compatibility branches and document boundary

### Title

Remove legacy string protocol branches and document FE/BE boundary rules

### Briefing / Context

After canonical models are in place, we must delete compatibility code paths (`alias/module`, `svc:` prefixes, prefix matching, etc.) to prevent regressions.

### Target

* No legacy synthetic module path support.
* No string prefix matching for overloads.
* Documentation: “BE owns the contract; FE implements it.”

### Scope

* Delete dead code.
* Add `docs/phase-03-frontend-api.md` (or in-crate docs) summarizing invariants.
* Add CI/lints to prevent BE from importing PBS modules.

### Checklist

* [ ] Remove legacy branches.
* [ ] Add boundary docs.
* [ ] Add lint/CI guard.

### Tests

* Full workspace tests.
* Golden tests.

### Risk

Low/Medium. Mostly deletion + docs, but could expose hidden dependencies.