Risk register and impossibility boundaries

Fundamental boundaries

1. Rendered output is underdetermined. Pixels/boxes cannot uniquely reveal whether layout came from flex, grid, constraints, absolute positioning or runtime code. Imported foreign content must mark inferred intent.
2. Arbitrary program behavior is not serializable as UI structure. NUIF does not promise to recover arbitrary JavaScript/Swift/Dart application logic.
3. Text is environment-sensitive. Font files, shaping versions, fallback and rasterization can differ. Exact conformance requires pinned inputs; portability must classify substitution separately.
4. Platform-native controls differ. Semantic equivalence may be possible while exact visuals/behavior are platform-specific.
5. Effects/shaders can exceed a portable core. Extensions may be preserved without being renderable.
6. Standard complexity can kill adoption. IFC/STEP demonstrate the cost of excessive semantic scope.
7. A single reference implementation can accidentally become the spec. Independent implementation is a standards gate.
8. Resource bytes carry legal and security constraints. Exact font/image preservation does not imply permission to redistribute or safe decoding.
9. Visual metrics are gameable. A flat screenshot can look exact while discarding editability, semantics, accessibility and responsive behavior.
10. Model confidence can be misleading. Raw probability is not calibrated correctness and cannot upgrade inferred evidence into source truth.
11. Capture can leak secrets. Browser/network/accessibility observations may expose credentials, personal data or proprietary content unless collection, export, retention and training are separately bounded.

Containment strategies

• explicit fidelity reports and inference confidence;
• authored + resolved snapshots instead of pretending either alone is canonical truth;
• opaque extension preservation;
• deterministic capability/evaluation contexts;
• small core + profiles;
• reference implementation backed by normative conformance fixtures;
• fuzzing/resource budgets for all untrusted inputs;
• early independent implementation and adapter experiments.
• stable asset IDs separated from resource digests, locators and provenance;
• verify resource size/digest before decoding and never fetch implicitly;
• typed operation output for models, atomic validation and finite correction loops;
• structural/text/resource/edit-task metrics alongside visual diagnostics;
• calibrated decision-level confidence, alternatives and abstention;
• private captures default to local processing, no retention and no training.

Current implementation risks

• The macOS graphics fork is a maintenance boundary. The editor pins refpath/xilem commit 1b96eb8; its parent eabfe0a moves the active renderer from wgpu 28 and metal-rs to wgpu 29 and the objc2 Metal bindings. The fork changes public API call sites and does not patch the Objective-C blocks ABI. Each fork update requires the editor tests, reverse dependency trace, and macOS Metal window smoke test recorded in nuif:research:macos-metal-block-future-incompatibility. A separate refpath/metal-rs move-to-block2 branch exists only for review; NUIF does not depend on the deprecated binding or that experimental patch.
• Release signing is credential-bound. The editor packaging gate builds, archives and smoke-tests an unsigned host package. Platform signing and notarisation require release credentials and remain separate from source conformance.
• Portable resources are only narrowly implemented. The deterministic package, RGBA8 PNG and static single-face TrueType subsets have executable gates, while CPU profile 0 remains unchanged. RFC 0010 cannot be accepted until broad media/font matrices, the configured Linux/Windows/macOS jobs produce passing hosted evidence, external reproduction, calibrated aggregate budgets and interoperability review pass.
• Capture and reconstruction accuracy remains unestablished. RFC 0011 and specification 14 now have bounded fixed-input contracts, a local pinned browser fixture and a typed synthetic evaluation report. They establish interfaces, refusal rules and metric consistency, not portable browser-capture or screenshot-reconstruction accuracy. No current release makes those accuracy claims.

Thesis falsifiers

The project should rethink its architecture if ordinary source round trips require broad regeneration, if unknown extension preservation cannot survive routine edits, if the layout vocabulary becomes a vendor-property dump, or if a second implementation cannot reproduce v0 behavior from specification + fixtures alone. The resource/reconstruction path should additionally narrow if package bytes cannot reproduce across writers, correction loops improve pixels by deleting semantics, confidence cannot support useful risk/coverage, or tuned models do not beat the untuned tool-assisted baseline.

Canonical source.