alkgen/tasks/implementation/w2-code-proof.md

id, name, status, depends_on, scope, risk, impact, level

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