---
id: w2-code-proof
name: "Wave 2: the code-shape proof (posture-A/C, ordering and determinism invariants)"
status: pending
depends_on: []
scope: narrow
risk: low
impact: component
level: implementation
---

## Description

The generality claim re-proven on shipped code for the posture-A/C
shapes (emit.md): a code-shaped fixture set exercising the codec/JIT
context shape on the shipped core. This is the shape generated
artifact hygiene rests on: document-ordered contexts, no-op
escaping, and determinism that makes regeneration diff-quiet
(posture A) and output compilable (posture C).

The proof lives in its own test binary (`tests/code_proof.rs`) with
its own fixture assets under `tests/fixtures/code_proof/`, per the
wave-1 per-binary fixture module convention. It grows beyond the
wave-1 double where the deep invariants live (the wave-1 double
pinned insertion-order arrays and the active `preserve_order`
feature; this proof pins the cross-registry determinism rows).

- **Typed context with document-ordered arrays** (convention 5,
  ADR-004): a typed context built by a Rust builder from a
  document-shaped fixture, arrays in document order, kind mapping in
  builder code, templates as dumb conditionals. The
  `preserve_order` load-bearing expectation is exercised again on
  the new set: document order drives rendered order.
- **No-op escaping** (ADR-005): the code posture renders without
  entity mangling; source-escaped literals pass through verbatim.
- **The determinism invariant** (ADR-003, the row generated-artifact
  hygiene depends on): byte-identical output across repeated renders
  within one registry, and across independent registry rebuilds from
  the same assets, including a rebuild registering in a different
  order (registration-order independence over the code-shaped set,
  the posture-A regeneration posture).
- **Both sinks in the determinism rows**: the streamed
  `render_to_write` output is byte-identical to the `render` String
  output on the same set and context.
- **The banner gap, stated honestly** (convention 8, emit.md posture
  A): the DO-NOT-EDIT banner is an emit-layer obligation and no
  engine-owned set ships in v0.1.0 to exercise it. The proof's
  templates model artifact shape without asserting any banner; the
  gap is recorded in Notes, never implied as coverage.

The stop-and-book rule applies as in the ssr proof: a needed core
exception is booked for the gate with written rationale, never
silently absorbed.

## Acceptance Criteria

- [ ] the code-shaped fixture set registers and renders through the
      public API with no-op escaping over a typed context with
      document-ordered arrays built by a Rust builder
- [ ] byte-identical output across repeated renders within one
      registry
- [ ] byte-identical output across independent registry rebuilds
      from the same assets, including a differing registration order
- [ ] `render` and `render_to_write` produce byte-identical output
      for the same set and context
- [ ] document order (not sort or hash order) drives rendered order
      on the new proof set
- [ ] the DO-NOT-EDIT banner gap recorded honestly in Notes; tests
      assert nothing banner-related
- [ ] `cargo test`, `cargo clippy --all-targets -- -D warnings`,
      `cargo fmt --check` pass
- [ ] no core changes required; any gap found is booked for the gate
      in Notes per the stop-and-book rule

## References

- docs/plans/implementation.md (wave 2, the code-shape proof bullet)
- docs/architecture/core.md (context conventions, render entry point)
- docs/architecture/emit.md (postures A and C)
- docs/architecture/decisions/001-one-core-template-set-targets.md
- docs/architecture/decisions/003-core-posture-sync-wasm-deterministic.md
  (the determinism invariant)
- docs/architecture/decisions/004-typed-contexts-builders-not-templates.md
- docs/research/reader-poc-summary.md (the POC findings informing
  the code-context shape this proof models)
- tests/code_fixtures.rs (the wave-1 double this proof grows beyond)

## Notes

> To be filled by implementation agent

## Summary

> To be filled on completion