feat(metamodel): origin.passthrough is type-preserving unless @convert

[dmealing]

Intent

Implement GitHub issue #185: make origin.passthrough type-preserving across all five language ports. A projection/view field forwarding another field's value via origin.passthrough @from must declare the same field. and array-ness as its resolved source field; a divergence fails load with a new ERR_PASSTHROUGH_TYPE_MISMATCH. Catches the mismodeling where a field.uuid source is surfaced as field.string on a view (leaving it String-typed end-to-end, forcing hand-written String<->UUID coercion) — verify --db can't see it (the column really is uuid); only the metadata knows both ends.

KEY DELIBERATE DECISIONS (not mistakes — treat as intended):

1. Compare subType + array-ness ONLY, NOT nullability. An outer-join view legitimately widens NOT NULL -> nullable, so a nullability check would false-positive (repo has a >15% FP kill bar). The check builds a 'field.[]' label and compares labels.
2. GENERALIZE + RETIRE the pre-existing narrow ERR_PARAMETER_REF_PASSTHROUGH_TYPE_MISMATCH (FR-015 stored-proc @parameterRef only) into ONE host-agnostic ERR_PASSTHROUGH_TYPE_MISMATCH in the origin-paths pass (runs over every object incl. parameter-ref values). Repointed fixture + removed narrow-check blocks + retirement comments are intentional.
3. Escape hatch is a NEW boolean attr @convert on origin.passthrough — ACKNOWLEDGEMENT ONLY, suppresses the error, does NOT generate a cast (consumer owns coercion). Deliberately NOT tied to origin.expression: computed projection columns (post-1.0, additive) #159/origin.expression (unbuilt/post-1.0). Registered as a first-class provider attr in all 5 ports (ADR-0023) and byte-matches the shared registry-conformance manifest.
4. Reads @convert via own-accessor (origin.* never inherits, ADR-0029), compares subType/isArray via RESOLVING/effective accessors (ADR-0039). Deliberate + commented.
5. Also fixed a pre-existing generator gap: 'index' concept missing from generate-embedded-metamodel.ts CONCEPT_DIRS; adding it normalized the index embedded file header comment (body byte-identical).

Fixtures-first TDD: 3 new conformance fixtures as the cross-port oracle. Ported to Python/C#/Java (Kotlin shares Java's loader) — all green (TS 459, Python 340, Java 438, C# 718). 4-angle code-simplifier pass applied and re-verified. BREAKING metamodel change: adopter metadata with a divergent passthrough now fails load — intended. CHANGELOG breaking note + agent-context authoring skill + regenerated goldens/registry/metamodel-docs all included.

What Changed

• origin.passthrough is now type-preserving across all five ports (TS/C#/Java/Python; Kotlin shares Java's loader): a projection/view field forwarding another field's value via @from must declare the same field.<subType> and array-ness as its resolved source. A divergence (e.g. a field.uuid source surfaced as field.string on a view) now fails load with the new generalized ERR_PASSTHROUGH_TYPE_MISMATCH, raised in the origin-paths validation pass that runs over every object. SubType + array-ness are compared only — nullability is deliberately excluded so a legitimate NOT NULL → nullable outer-join widening does not false-positive.
• Generalizes and retires the narrow FR-015 ERR_PARAMETER_REF_PASSTHROUGH_TYPE_MISMATCH (stored-proc @parameterRef only) into the single host-agnostic ERR_PASSTHROUGH_TYPE_MISMATCH; the old narrow-check blocks are removed and the parameter-ref fixture is repointed to the generalized code. Adds a new boolean @convert attr on origin.passthrough as an acknowledgement-only escape hatch that suppresses the error (consumer owns coercion; no cast is generated), registered as a first-class provider attr in all five ports and byte-matched to the shared registry-conformance manifest.
• Ships 3 new cross-port conformance fixtures as the oracle, regenerated goldens/metamodel-docs/ERROR-CODES, a CHANGELOG breaking note, and synced authoring-skill + migration/porting docs. Also fixes a pre-existing generator gap (index concept missing from generate-embedded-metamodel.ts CONCEPT_DIRS). This is a breaking metamodel change: adopter metadata with a divergent passthrough now fails to load.

Risk Assessment

✅ Low: A well-bounded, cross-port-conformance-gated loader change with consistent TS/C#/Java/Python implementations, correct ADR-0039 own-vs-resolving accessor usage, full coverage preservation of the retired narrow check, and a documented @convert escape hatch; the breaking metamodel behavior is intentional and well-justified.

Testing

Installed TS deps (bun install), Python dev extras (uv sync), and built the C#/Java ports; ran the cross-port conformance oracles which are the test of record for the #185 fixtures, plus the touched TS unit tests (fr015, origin-completeness, registry). All green across TS, C#, Java (Kotlin shares its loader), and Python. To produce reviewer-visible end-to-end evidence, I drove the real TS loader directly against the three #185 conformance fixture inputs (same provider composition the conformance runner uses) and captured the actual user-facing behavior: a field.uuid source surfaced as field.string on a projection view fires ERR_PASSTHROUGH_TYPE_MISMATCH with the message telling the author to either declare field.uuid or set @convert:true; a string[]→string array-ness divergence fires the same code; and @convert:true loads clean with zero errors. The transient evidence script was removed from the working tree after capturing the transcript; the tree is clean and evidence lives only in the dedicated evidence dir. No setup issues, flakiness, or failures encountered.

Evidence: TS loader transcript — #185 type-preservation end-to-end (ERR_PASSTHROUGH_TYPE_MISMATCH on subType + array-ness divergence; @convert loads clean; full human-facing error message)

=== error-origin-passthrough-type-mismatch === errorCodes: ["ERR_PASSTHROUGH_TYPE_MISMATCH"] - code=ERR_PASSTHROUGH_TYPE_MISMATCH referrer=CharacterView::currentLocationId target=demo::GameCharacter.currentLocationId === error-origin-passthrough-array-mismatch === errorCodes: ["ERR_PASSTHROUGH_TYPE_MISMATCH"] - code=ERR_PASSTHROUGH_TYPE_MISMATCH referrer=ProductView::tags target=demo::Product.tags === origin-passthrough-convert-optout === errorCodes: [] (loaded clean) === Human-facing loader message (subType mismatch) === origin.passthrough on CharacterView.currentLocationId: field is field.string but its @from source "demo::GameCharacter.currentLocationId" is field.uuid — a passthrough forwards the value unchanged, so the types must match. Declare field.uuid, or set @convert: true to acknowledge a deliberate type change.

=== error-origin-passthrough-type-mismatch ===
providers: ["metaobjects-core-types","metaobjects-db"]
errorCodes: ["ERR_PASSTHROUGH_TYPE_MISMATCH"]
errors:
  - code=ERR_PASSTHROUGH_TYPE_MISMATCH referrer=CharacterView::currentLocationId target=demo::GameCharacter.currentLocationId
warnings: 0

=== error-origin-passthrough-array-mismatch ===
providers: ["metaobjects-core-types","metaobjects-db"]
errorCodes: ["ERR_PASSTHROUGH_TYPE_MISMATCH"]
errors:
  - code=ERR_PASSTHROUGH_TYPE_MISMATCH referrer=ProductView::tags target=demo::Product.tags
warnings: 0

=== origin-passthrough-convert-optout ===
providers: ["metaobjects-core-types","metaobjects-db"]
errorCodes: []
errors:
warnings: 0

=== SUMMARY (#185 type-preservation) ===
subType mismatch  -> ERR_PASSTHROUGH_TYPE_MISMATCH  [expect ERR_PASSTHROUGH_TYPE_MISMATCH]
array-ness mismatch-> ERR_PASSTHROUGH_TYPE_MISMATCH  [expect ERR_PASSTHROUGH_TYPE_MISMATCH]
@convert opt-out   -> (loaded clean)  [expect loaded clean]

All #185 assertions passed.

=== Human-facing loader messages (subType mismatch) ===
  origin.passthrough on CharacterView.currentLocationId: field is field.string but its @from source "demo::GameCharacter.currentLocationId" is field.uuid — a passthrough forwards the value unchanged, so the types must match. Declare field.uuid, or set @convert: true to acknowledge a deliberate type change.

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

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✅ **Review** - passed

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✅ **Test** - passed

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• bun test packages/metadata (TS metadata package — 2119 pass, includes origin/validation-passes)
• bun test packages/metadata/test/conformance.test.ts -t passthrough (16 passthrough conformance scenarios — the 3 new #185 fixtures + repointed parameter-ref fixture + existing passthrough fixtures)
• bun test packages/metadata/test/fr015-source-parameter-ref.test.ts packages/metadata/test/origin-definition-completeness.test.ts packages/metadata/test/registry-conformance.test.ts (31 pass — touched by the diff)
• dotnet test MetaObjects.Conformance.Tests (C# — 718 pass, includes new passthrough fixtures)
• mvn -o test -Dtest=ConformanceTest (Java metadata — 428 pass) + -Dtest=RegistryManifestConformanceTest (3 pass — @convert registration)
• uv run pytest tests/conformance/test_conformance.py tests/conformance/test_registry_conformance.py (Python — 221 pass)
• bun run transient evidence script driving the real TS loader against the 3 #185 fixtures — captured ERR_PASSTHROUGH_TYPE_MISMATCH firing on subType + array-ness mismatch and clean load with @convert, plus the full human-facing ParseError message

⚠️ **Document** - 1 info

• ℹ️ docs/superpowers/specs/2026-05-28-fr-015-source-parameter-ref-design.md:106 - The historical FR-015 design spec (and two sibling plan/spec docs) still name the retired ERR_PARAMETER_REF_PASSTHROUGH_TYPE_MISMATCH error code and describe the pre-generalization parameter-ref-only type-match check. The living reference docs (ERROR-CODES.json, metamodel-docs, migration guide, cross-language porting guide) now all reflect the generalized ERR_PASSTHROUGH_TYPE_MISMATCH, but these design journals were left as-is.

⚠️ **Lint** - 1 info

• ℹ️ server/python/src/metaobjects/loader/validation_passes.py:1522 - New _check_passthrough_type calls resolved_source(origin_source, ...) where origin_source: object but resolved_source expects ErrorSource — mypy strict reports Argument 1 ... incompatible type 'object'; expected 'ErrorSource'. This is one new mypy error vs. the 53-error baseline; it copies the identical pre-existing pattern already present 5× in this file (e.g. line 1475 in _check_extends_origin_agreement), originating from MetaOrigin.source being typed object. mypy is configured (strict) but NOT a CI gate (Python CI runs pytest only), so the codebase tolerates these. Fixing properly requires a cross-cutting MetaOrigin.source typing change, out of scope for this change.

✅ **Push** - passed

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