prometeu-studio/docs/pbs/agendas/13.4. IR and Lowering Workshop 4 - Builtins, Host Bindings, and Artifact Invariants.md

PBS Frontend IR and Lowering Workshop 4

Status: Active

Purpose

Run the fourth focused discussion for 13. Lowering IRBackend Specification.md to close frontend-specific pending points:

• builtin-facing source semantics at frontend lowering boundary,
• diagnostics stability for lowering-related failures,
• and test-gate evidence needed to close v1 frontend slice.

Why This Slice Last

This workshop should close only after Workshops 1 to 3 define the base lowering contract and callable status map.

Proposed Meeting Order

1. Reconfirm frontend-only scope and deferred backend concerns.
2. Close builtin-shell obligations at frontend lowering boundary.
3. Close diagnostics identity/attribution obligations for lowering-related failures.
4. Close minimum gate evidence package (Gate U).
5. Produce closure checklist for spec 13 frontend slice.

Decisions To Produce

1. Frontend-lowering obligations for builtin-facing constructs in v1.
2. Stable diagnostics contract for frontend-lowering rejections.
3. Mandatory fixture families to prove 13 frontend obligations.
4. Explicit list of deferred topics that belong to future backend-focused agenda.

Candidate Decisions

1. Builtin Surfaces Are Frontend-Validated Before Any Backend Contract

Candidate direction:

• builtin names and metadata usage are validated at frontend scope per existing specs,
• and lowering emits deterministic outcomes or deterministic rejection.

2. Diagnostics Contract Is Mandatory For Frontend-Lowering Failures

Candidate direction:

• code/severity/primary attribution are fixed and test-backed for required rejection classes,
• enabling reliable regression protection.

3. Gate Evidence Is Small But Mandatory

Candidate direction:

• each required obligation has at least one positive and one negative fixture where applicable,
• with assertions for lexer/parser/AST/IRBackend/diagnostics.

4. Backend Topics Are Explicitly Deferred

Candidate direction:

• VM lowering, bytecode mapping, runtime, verifier, and loader remain out of this agenda,
• and are listed as deferred backlog topics.

Questions To Resolve In The Room

1. Which builtin scenarios are mandatory in v1 fixture corpus?
2. Which lowering-related diagnostics are mandatory to freeze now?
3. What is the minimum evidence bar to declare 13 frontend slice closed?
4. Which open points are explicitly deferred without blocking frontend progress?

Expected Outputs

1. a decision note on builtin frontend-lowering obligations,
2. a decision note on diagnostics/test evidence obligations,
3. and a closure checklist for 13 frontend scope.

Explicit Deferrals

• VM lowering design,
• bytecode/PBX mapping,
• runtime execution contracts,
• verifier and loader internals.

Inputs

• docs/pbs/specs/6.1. Intrinsics and Builtin Types Specification.md
• docs/pbs/specs/12. Diagnostics Specification.md
• docs/pbs/specs/13. Lowering IRBackend Specification.md
• docs/general/specs/13. Conformance Test Specification.md
• docs/general/specs/19. Verification and Safety Checks Specification.md
• docs/pbs/agendas/13.3. IR and Lowering Workshop 3 - Callables, Services, Contracts, and Callbacks.md