Limitations and Alpha Status

XY is early alpha. The declarative API, implemented 2D chart families, notebook display, standalone HTML, native PNG, and SVG are usable today, but pre-1.0 releases can make breaking changes with migration notes.

• Ingestion, canonical memory, initial scans, binning, and decimation still depend on source row count.
• Large-scatter overview rendering is screen-bounded when density mode is used; it does not draw one exact marker per source row.
• Long lines use screen-derived decimation. A narrow live view can request a new visible-window representation.
• Density is native-binned and GPU-rendered. It is not an all-GPU ingest and aggregation pipeline.
• Arrow ingest is zero-copy only for compatible, null-free primitive layouts. Chunking, nulls, dtype conversion, and datetime conversion can copy.
• Disk-backed/out-of-core residency is not a shipped public tier.

See Large data and performance and Benchmarks for scoped evidence.

• Python callbacks require a live widget or framework adapter. Standalone HTML cannot call a Python process.
• append() supports scatter and line traces, not arbitrary chart structure. Line x values must continue monotonically, and encoded channel tails have validation constraints.
• Already-exported HTML is a snapshot and does not follow later appends.
• Linked views synchronize viewport axes, not selections or cross-filtering.
• Facets support display/export and shared domains but not Chart append, pick, or Python-side range-selection methods.
• Browser context limits matter on large dashboards. XY's context governor defaults to 12 live contexts and reacquires off-screen charts as they return; more than that many simultaneously visible charts is not an unbounded guarantee.

• Browser chrome accepts CSS and Tailwind classes through stable DOM slots. WebGL/native marks accept a validated CSS subset through style=; arbitrary selectors do not paint mark geometry.
• “Your styles win” applies to themeable browser chrome defaults, not every structural layout rule, mark renderer, annotation shape, or native export.
• Native PNG cannot apply author custom_css. Use renderable chart/mark styles or Engine.chromium for browser CSS fidelity.
• Declarative colorbar() derives built-in chrome from supported continuous marks. It intentionally omits constant/categorical color, truecolor grids, and density scatter after that tier drops per-row color values.
• Self-contained HTML blocks network access but requires inline script/style and a blob: worker under its emitted CSP. A nonce/hash-only host must serve the bundle and data through its own wrapper.

The browser client ships a semantic chart region, generated trace/axis summary, a polite live region, direct-point Arrow/Home/End navigation, named toolbar controls, visible focus styling, reduced-motion behavior, and forced-colors affordances.

That is not yet full accessibility parity. Current conformance does not cover aggregated-bin keyboard navigation, a view-as-table escape hatch, every screen-reader/OS combination, every chart family, or pixel-identical cross-browser output. Test the actual chart and assistive-technology matrix required by your application.

XY requires Python 3.11 or newer. Published native wheels include the Rust core and bundled browser client; source builds require a Rust toolchain. There is no silent NumPy compute fallback when the native core is unavailable.

Review Installation, Serving, CSP, and offline use, and the Changelog before shipping an alpha upgrade.