# Phase 0 GC2 Format Contract Completeness Evidence

**Gate:** GC2 / Format contract completeness  
**Result:** Passed for shared format contracts, schema validation, semantic validation, and diagnostic error generation.  
**Date:** 2026-09-05T18:33:45Z  
**Tooling:** Zero-dependency Node.js validator (`tools/validate-exhibit.mjs`), JSON Schema Draft-07 (`schema/xzbt-0.1.schema.json`), and automated test suite (`test/gc2-runner.test.mjs`).

## Specification & Implementation Summary

1. **Normative Specification:** Updated [XZBT_0-1_Format_Specification.md](../../XZBT_0-1_Format_Specification.md) (Revision 0.2) defining document structure, metadata, primitive type system with strict coercion ban, `ValueSpec` 5-form grammar and operator arity table, `ConditionSpec` comparisons and logical composition with edge-trigger re-arming, `DurationSpec` literals, and standard error codes.
2. **Structural JSON Schema:** Authoritative schema authored at [schema/xzbt-0.1.schema.json](../../../schema/xzbt-0.1.schema.json).
3. **Semantic Validator:** Standalone CLI engine authored at [tools/validate-exhibit.mjs](../../../tools/validate-exhibit.mjs).

## Automated Conformance Test Matrix Results

The automated test runner executed 12 tests covering valid exhibits and deliberate fault injections:

| Fixture | Classification | Expected Outcome | Actual Result | Status |
| :--- | :--- | :--- | :--- | :---: |
| `test/fixtures/gc2/valid-minimal.xzbt` | Minimal Exhibit | Valid (0 errors) | Valid (0 errors) | **PASS** |
| `test/fixtures/gc2/valid-full-feature.xzbt` | Full Feature Exhibit | Valid (0 errors) | Valid (0 errors) | **PASS** |
| `prototypes/phase0/fixtures/amber-study.xzbt` | Prototype Baseline | Valid (0 errors) | Valid (0 errors) | **PASS** |
| `prototypes/phase0/fixtures/blue-study.xzbt` | Prototype Baseline | Valid (0 errors) | Valid (0 errors) | **PASS** |
| `test/fixtures/gc2/invalid-unknown-field.xzbt` | Fault Injection | `ERR_UNKNOWN_FIELD` | `ERR_UNKNOWN_FIELD` | **PASS** |
| `test/fixtures/gc2/invalid-unsupported-version.xzbt` | Fault Injection | `ERR_UNSUPPORTED_VERSION` | `ERR_UNSUPPORTED_VERSION` | **PASS** |
| `test/fixtures/gc2/invalid-id-syntax.xzbt` | Fault Injection | `ERR_INVALID_ID` | `ERR_INVALID_ID` | **PASS** |
| `test/fixtures/gc2/invalid-reference-missing.xzbt` | Fault Injection | `ERR_INVALID_REFERENCE` | `ERR_INVALID_REFERENCE` | **PASS** |
| `test/fixtures/gc2/invalid-type-mismatch.xzbt` | Fault Injection | `ERR_TYPE_MISMATCH` | `ERR_TYPE_MISMATCH` | **PASS** |
| `test/fixtures/gc2/invalid-cyclic-bindings.xzbt` | Fault Injection | `ERR_CYCLIC_DEPENDENCY` | `ERR_CYCLIC_DEPENDENCY` | **PASS** |
| `test/fixtures/gc2/invalid-out-of-bounds.xzbt` | Fault Injection | `ERR_OUT_OF_BOUNDS` | `ERR_OUT_OF_BOUNDS` | **PASS** |
| `test/fixtures/gc2/invalid-operator-arity.xzbt` | Fault Injection | `ERR_INVALID_ARITY` | `ERR_INVALID_ARITY` | **PASS** |

## Gate Conclusion

The shared contracts portion of **GC2: Format Contract Completeness** is satisfied. The schema, validator, and test suite provide a deterministic foundation for Phase 1 runtime loading and validation.
Subsystem-specific schemas and contracts (audio graphs, visual systems, scenarios) will be filled in dependency order alongside their respective phases.

## Revision 0.3 reconciliation addendum

GC3 review found that the draft BindingSpec used `from`/`to`/`transform`, conflicting with the PRD's canonical `source`/`target`/`scale`/`offset`/`clamp` fields. Revision 0.3 corrected the schema, validator, and affected fixtures to the PRD vocabulary and added `when` plus exact smoothing semantics. The same 12-case GC2 matrix was rerun as part of the 27-test combined Phase 0 suite and still passed with zero failures. See the [GC3–GC5 evidence](2026-09-05-gc3-gc5-contracts.md) for the reconciliation rationale and combined command.