prometeu-studio/docs/pbs/agendas/11.4. Diagnostics Workshop 4 - Backend-Originated Diagnostic Mapping.md

PBS Diagnostics Workshop 4

Status: Active

Purpose

Run the fourth focused discussion for 11. Diagnostics Specification.md on backend-originated failures:

• lowering failures,
• verifier failures,
• load-facing failures,
• and how or whether they map back into the PBS-facing diagnostics contract.

Why This Slice Last

This slice should come last because it depends on:

• the phase vocabulary,
• the attribution baseline,
• and the lowering boundary being clearer.

It should be the point where 11 explicitly interfaces with 12, 15, and 19.

Proposed Meeting Order

1. Reconfirm the frontend diagnostics baseline already closed.
2. Sort backend-originated failure classes.
3. Decide which backend failures remain PBS-facing diagnostics.
4. Decide which failures belong only to artifact-facing tooling.
5. Decide the minimum source-mapping obligations, if any.

Failure Classes To Sort

• lowering rejection due to unsupported semantic state,
• host-binding emission mismatch,
• verifier rejection of malformed artifact invariants,
• loader rejection directly attributable to malformed or unauthorized PBS-facing artifact usage,
• and artifact-only corruption not attributable to valid PBS source.

Decisions To Produce

1. The boundary between PBS-facing and artifact-facing diagnostics.
2. The minimum source-mapping obligation for backend failures.
3. Whether verifier/load failures participate in 11 directly.
4. The input contract 13 may assert for these classes.

Candidate Decisions

1. Only Source-Attributable Backend Failures Enter The PBS Diagnostics Contract

Candidate direction:

• if a backend failure is directly attributable to validly analyzed PBS source plus normative lowering rules, it remains part of the PBS-facing diagnostics contract,
• otherwise it is artifact-tool or implementation failure surface.

Rationale:

• This keeps PBS diagnostics user-facing rather than compiler-internal.

2. Verifier And Loader Failures Enter 11 Only When Userland Actionability Exists

Candidate direction:

• malformed or unauthorized host-facing artifact usage attributable to source remains in scope,
• purely artifact-internal corruption or implementation bugs remain out of scope.

Rationale:

• This matches the current draft's narrow load-facing baseline.

3. Source Mapping Is Useful But Minimal In v1

Candidate direction:

• v1 requires a source-facing location when the failure is source-attributable,
• but does not yet require one standardized artifact offset map or source-map format.

Rationale:

• This keeps the contract implementable while leaving room for richer tooling later.

4. Conformance Should Assert Only The Stable External Surface

Candidate direction:

• 13 may assert rejection phase, source attribution, and rejection class for backend-originated PBS diagnostics,
• but not one exact verifier or loader message format.

Rationale:

• This keeps conformance aligned with the rest of 11.

Questions To Resolve In The Room

1. Which lowering failures are legitimate user-facing diagnostics versus compiler bugs?
2. Do verifier failures need their own normative phase label, or map into linking/load-facing rejection?
3. Is one source location enough for backend-originated failures?
4. How much of artifact-facing tooling belongs in the PBS language contract at all?
5. What exactly must 13 be able to test once 12 and 15 are closed?

Expected Outputs

This workshop should produce:

1. a decision record for backend diagnostics boundaries,
2. a source-mapping obligations note,
3. and explicit integration tasks for 11, 12, 13, and 15.

Explicit Deferrals

• exact source-map file formats,
• artifact UI presentation,
• implementation bug reporting policy,
• and internal compiler exception handling.

Inputs

• docs/pbs/specs/11. Diagnostics Specification.md
• docs/pbs/specs/12. IR and Lowering Specification.md
• docs/pbs/specs/15. Bytecode and PBX Mapping Specification.md
• docs/pbs/specs/19. Verification and Safety Checks Specification.md
• docs/pbs/agendas/11. Diagnostics Agenda.md
• docs/pbs/agendas/11.1. Diagnostics Workshop 1 - Diagnostic Identity and Attribution.md
• docs/pbs/agendas/11.3. Diagnostics Workshop 3 - Cost Diagnostics and Warning Policy.md