Feature-flag conventions

Shared concerns use the same flag name with the same semantics in every library. A consumer that learns otel or mcp once should get identical behavior across every library and its bindings. Repo-specific flags stay local — this contract governs only shared concerns.

Standard flags

Rules

• Names are the contract. Never invent a synonym for a shared concern (opentelemetry, observability, otlp for what is otel; model-context-protocol for mcp). Rename divergent flags to match.
• Semantics travel with the name. otel must mean the OTLP export layer everywhere, not "enable tracing" (tracing is always-on) and not a metrics-only subset.
• Always-on tracing, opt-in export. Do not force the opentelemetry dependency tree on library consumers — keep it behind otel so a plain dependency stays lean.
• Implication edges are fixed: mcp-http ⇒ mcp; otel ⇒ (always-on) tracing.
• Mutually-exclusive allocators carry a both-enabled compile_error! guard by default. Exception: a crate that must build with --all-features (a coverage gate, cargo doc --all-features) resolves by precedence instead, jemalloc winning via cfg(all(feature = "mimalloc", not(feature = "jemalloc"))), and states why in a ~keep comment at the #[global_allocator].
• Adding a shared flag to a new library? Copy the name, default, and implication edges from this table rather than redefining them. Coordinate a change to this contract across all libraries before landing it — no repo diverges unilaterally.

Xberg features

All Xberg features are in crates/xberg/Cargo.toml.

ORT-Incompatible Targets (WASM, Android x86_64 emulator)

Only ORT-dependent paths are incompatible. The same paths block both WASM (no native ORT linkage at all) and the x86_64-linux-android emulator triple (no pyke prebuilt; aarch64-linux-android does ship a prebuilt and gets full ORT):

• paddle-ocr — ONNX Runtime + native C++ deps: not WASM-safe; no Android x86_64 prebuilt
• layout-detection — depends on ONNX Runtime layout models: not WASM-safe; no Android x86_64 prebuilt (RT-DETR + table classifier are available off-ORT via the layout-tract sibling, below)
• embeddings — depends on ONNX Runtime sentence-transformer models: not WASM-safe; no Android x86_64 prebuilt
• auto-rotate — depends on ONNX Runtime orientation classifier: not WASM-safe; no Android x86_64 prebuilt (available off-ORT via the auto-rotate-tract sibling, below)
• formula-recognition — LaTeX recognition for layout formula regions (RapidLaTeXOCR ONNX): ORT-dependent, opt-in, excluded from full/formats

Pure-Rust type-only companion features expose the public config/result types for the above without pulling in ORT:

• layout-types — LayoutDetectionConfig, TableModel, BBox, DetectionResult, LayoutClass, LayoutDetection, RecognizedTable. layout-detection implies layout-types.
• auto-rotate-types — OrientationResult. auto-rotate implies auto-rotate-types.
• embedding-presets — EmbeddingPreset (already existed; pure-Rust preset metadata).

Pure-Rust tract inference variants run select ONNX models where native ORT cannot link, loading the same .onnx artifacts through the tract engine (CPU-only, no native library):

• layout-detection (ORT) → layout-tract (tract): RT-DETR layout detection + the PP-LCNet wired/wireless table classifier run on WASM and the Android x86_64 emulator. TATR, SLANeXT, PP-DocLayout-V3, and YOLO stay ONNX Runtime-only (tract 0.23.4 op-coverage gaps).
• auto-rotate (ORT) → auto-rotate-tract (tract): PP-LCNet document-orientation on WASM and the Android x86_64 emulator.

WASM/Android-safe variants:

• ocr (native) → ocr-wasm (uses tesseract-wasm + safe image deps) — Android keeps native ocr
• excel (native) → excel-wasm (drops tokio-runtime) — Android keeps native excel
• tree-sitter (native dlopen) → tree-sitter-wasm (statically-linked grammar pack). NOT in wasm-target: the 371-language grammar pack pushes the browser .wasm past jsDelivr's 50 MB per-file cap, breaking the CDN-hosted demo. WASM has no code intelligence; Android keeps native tree-sitter.
• liter-llm — NOT in no-ort-target: tokenizers → hf-hub → ureq → rustls + socks are wasm-incompatible. Enabled explicitly by android-target and full; WASM has no LLM path
• stopwords — pure-Rust, included in no-ort-target
• keywords — pure-Rust YAKE/RAKE, included in no-ort-target

The no-ort-target aggregate is the shared no-ORT base used by both wasm-target and android-target. wasm-target = no-ort-target + excel-wasm + ocr-wasm + layout-tract + auto-rotate-tract + ner-candle-wasm (NO tree-sitter — see above). android-target adds to no-ort-target: excel, tree-sitter, ocr, sceptre-ocr-tract, paddle-ocr-tract, layout-tract, auto-rotate-tract, api, mcp, liter-llm, structured, hwpx, diff, classification, captioning, ner-llm, url-ingestion. Read the manifest before assuming a member — both lists are edited often.

PDF Backend

• pdf — the canonical PDF feature. It is a pure alias: pdf = ["pdf-native"], and pdf-native carries the dependency set (dep:xberg-native-pdf, lopdf, image, flate2, html, image-encode). There is no feature literally named xberg-native-pdf. Included in formats, full, no-ort-target, and wasm-target.
• pdf-pdfium — the pdfium FFI comparison backend (crates/xberg-pdfium-render). Implies tokio-runtime because the pdfium calls are synchronous and must run under spawn_blocking. Opt-in; in no aggregate. Without it, selecting the pdfium backend fails loudly rather than falling back.

Config value, not feature: PdfConfig.backend (core/config/pdf.rs) parses exactly "native" and "pdfium". The pre-1.1.0 spelling "pdf_oxide" is rejected, not aliased — deliberately, so it cannot survive in configs. Omitting the field defaults to Native.

ORT Variants (Mutually Exclusive)

• ort-bundled — downloads official Microsoft ORT binaries; default when OCR/ML features active
• ort-dynamic — load ORT from system; only when system ORT is guaranteed present

Platform-Conditional

• xberg-paddle-ocr, hf-hub, pprof — excluded on wasm32
• ureq: rustls on non-Windows; native-tls on Windows
• xberg-ffi and xberg-dart cargo dependencies are target-conditional: cfg(target_os = "android") (both ABIs — aarch64 and x86_64) and cfg(target_os = "ios") select android-target, the pure-Rust tract ML surface with no ONNX Runtime; cfg(target_os = "windows") selects windows-target (full ORT ML via ort-bundled); cfg(all(target_os = "macos", target_arch = "x86_64")) selects macos-intel-target. All other targets (Linux, macOS arm64) get the full ORT-enabled feature set. Android and iOS run inference through tract, not ORT, on every ABI — there is no arch split that gives arm64 Android phones a native ORT build.

Aggregate Sets

Member lists change often. Read crates/xberg/Cargo.toml before relying on any of these descriptions for a specific feature.

CI parity guard (GH#1443)

mise run verify:feature-parity runs python3 scripts/ci/check-feature-parity.py crates/xberg/Cargo.toml.

It compares only code-bearing features — those whose definition pulls a dep:, or whose name appears in a #[cfg(feature = "…")] under crates/xberg/src. Pure aliases drop out while their members are still compared, so the rule cannot manufacture a false pass.

Guarded pairs, with the deltas each subset is allowed:

android-target and no-ort-target are deliberately unguarded (UNGUARDED in the script): they substitute the tract stack or drop ORT outright, so encoding their deltas would turn the check into a change-detector that fires on every legitimate edit.

Consequence: adding a feature to full without adding it to windows-target fails CI.

Build Profiles

• release — LTO thin, codegen-units=1, strip
• profiling — inherits release, retains debug info
• xberg-wasm override: opt-level="z" (size-optimized)
• sevenz-rust2 override: opt-level=1 — not 2. The manifest comment is explicit: "opt-level=2 still SIGBUS'd in go:e2e". Raising it reintroduces the crash
• zip override: opt-level=2 (prevents SIGBUS on macOS ARM64)