Implementation status

Implemented in 0.1 alpha

• Ordered async writes, resize, reset, clear, scrolling and user-input events.
• Configurable pending-input backpressure with cancellation before admission.
• Streaming UTF-8 and UTF-16 input across write boundaries.
• Normal and alternate buffers, scrollback, delayed wrap and complex-cell resize reflow verified against the pinned xterm.js oracle across shrink/grow, cursor-line and scrollback scenarios.
• C0 controls and common ESC/CSI commands for cursor movement, insertion, deletion, erase, scrolling, tabs and scroll regions.
• SGR flags, 16/256-color palette values, true color and underline color.
• DEC private modes for cursor, origin, wrapping, alternate screen, mouse tracking, focus, bracketed paste and synchronized output.
• OSC title handling plus snapshot-scoped immutable OSC 8 URI, explicit ID and parameter metadata.
• DSR status/cursor responses through the Data event.
• Immutable viewport/full-buffer snapshots with cell attributes.
• Custom CSI, ESC, OSC, DCS and APC handlers, including asynchronous handlers.
• A single production VT500 parser with SOS/PM, C1-anywhere transitions, bounded OSC/DCS/APC payloads and strict handler failure recovery.
• Effective two-column minimum sizing with a safe low-level fallback for unsupported one-column buffers containing wide cells.
• Addon lifecycle, Unicode 6, exact generated Unicode 11, exact generated Unicode 15 width and UAX #29 extended-grapheme providers, plus the compatibility .NET grapheme-oriented provider.
• Stable link-provider contracts plus the optional XtermSharp.Addons.WebLinks port, including strict URL validation, wrapped/wide/combined-cell range mapping, custom activation/hover/leave callbacks and Avalonia hover/click interaction.
• Platform-neutral core selection and decoration-provider contracts plus the optional XtermSharp.Addons.Search port, including forward/reverse literal and regex search, case/whole-word/incremental options, wrapped/wide/UTF-16 coordinate mapping, capped result highlighting, active-result tracking and debounced updates after writes or resize. Overview-ruler colors are exposed as decoration metadata; the current Avalonia adapter has no overview-ruler surface.
• The optional XtermSharp.Addons.Progress port tracks ConEmu OSC 9;4 remove, percentage, error, indeterminate and pause states through the public production parser. It strictly validates decimal payloads, clamps percentages, preserves prior values where upstream does, exposes programmatic reset/restore and unregisters cleanly on disposal.
• The optional XtermSharp.Addons.Clipboard port handles OSC 52 query, set and explicit clear operations through a platform-neutral provider. Read and write permissions default to denied, decoded UTF-8 payloads are bounded, malformed input is rejected without changing clipboard state, and the Avalonia, MAUI, Windows Forms, WPF and WinUI packages supply UI-dispatched system clipboard adapters.
• The pinned xterm.js 6.0.0 inventory contains 1,361 concrete upstream cases: 54 front-end renderer cases are explicitly excluded, while all 1,307 headless-applicable cases are covered by C# tests (1,306 direct ports and one documented architecture-equivalent streaming test).
• All 76 upstream escape-sequence fixtures run in xUnit and are differentially checked against the pinned xterm.js headless build.
• Fourteen permanent complex-cell resize/reflow scenarios differentially verify ASCII, wide, combined, grapheme, styled, protected and hyperlink cells, including cursor-line suppression, delayed wrap, orphan continuations and viewport/scrollback positioning.
• Seven permanent marker and metadata scenarios differentially verify physical-row mapping during shrink/grow, discarded-row disposal, scrollback trimming, line insertion/deletion, cursor-line suppression and OSC 8 lifetime. Search decorations are recomputed against the reflowed layout.
• A built-in OSC 8 link provider maps contiguous and wrapped cell ranges. TerminalView uses the normal cancellable link pipeline for hover, leave and activation; activation only raises an application event and never launches an untrusted terminal-provided URI automatically.
• Manifest generation and auditing enforce unique upstream-to-C# bindings with no pending applicable cases.
• Ordered PasteAsync and focus reporting APIs keep UI protocol decisions on the terminal processor queue; runtime option changes carry committed revisions.
• Public construction and runtime-update models cover cursor-line reflow, Windows PTY backend/build compatibility, stdin suppression and Kitty SGR 221/222 control with upstream defaults. Nested option objects are cloned before publication, and each update raises one committed event.
• Unchanged buffer lines reuse immutable line snapshots, avoiding repeated cell materialization for full-buffer publication.
• XtermSharp.Rendering provides backend-neutral frame coordination, themes, selection extraction, layered addon decorations, synchronized-output throttling, damage tracking and batched text/background display-list runs.
• XtermSharp.Rendering.Skia provides SkiaSharp 3.119.4 and HarfBuzz shaping, font fallback, cached fonts/paints, worker-prepared retained row pictures and the shared rendering telemetry overlay and Auto/Software/Gpu request model used by every platform adapter.
• XtermSharp.Avalonia provides an externally bound TerminalView with DPI-aware resizing, worker-side frame preparation, change-only binding notifications, keyboard/mouse protocols, local selection, clipboard, focus, IME preedit and registered-link interaction.
• XtermSharp.Maui provides an externally bound TerminalView that reuses the SkiaSharp/HarfBuzz backend through SKGLView with SKCanvasView fallback. It supports device-pixel scaling, resize, touch scrollback, pointer selection, tracked mouse input, link activation, soft-keyboard text/backspace/enter input, scrolling and clipboard integration.
• XtermSharp.WinForms provides an externally bound, DPI-aware OpenTK GPU/Software-Skia TerminalView with worker-side frame preparation, browser-compatible keyboard coordinates, committed text/IME input, terminal mouse protocols, local selection, clipboard and registered-link interaction.
• XtermSharp.Wpf provides a dependency-property-based, DPI-aware OpenTK GPU/Software-Skia TerminalView with worker-side frame preparation, committed text/IME input, browser-compatible key coordinates, terminal mouse protocols, local selection, clipboard and registered-link interaction.
• XtermSharp.WinUI provides a dependency-property-based, DPI-aware SKSwapChainPanel/bitmap TerminalView with worker-side frame preparation, CoreText IME input, browser-compatible key coordinates, terminal mouse protocols, local selection, clipboard and registered-link interaction.
• Every UI adapter supports live RequestedRenderMode changes without replacing the assigned terminal and reports the actual most recently presented mode separately through ActiveRenderMode and IsGpuAccelerated.
• The Avalonia, Windows Forms, WPF and WinUI SSH samples integrate SSH.NET without changing the transport-neutral library boundary and demonstrate password/private-key authentication, SHA-256 host-key verification and remote PTY resize updates.
• The no-PTY Avalonia demo loads both optional addons and exposes interactive link activation plus case-sensitive, whole-word and regex search controls with previous/next result navigation.
• The MAUI SSH demo targets Android, iOS, Mac Catalyst and Windows and compiles the same transport source as the Avalonia SSH demo for identical authentication, host-key verification and PTY behavior.

Still required before 1.0

The prioritized implementation and test acceptance criteria are maintained in the upstream parity acceptance checklist.

• Keep the manifest and differential oracle synchronized when the pinned xterm.js baseline is upgraded.
• Extend differential coverage beyond the current reference scenarios and complex-cell reflow, marker/metadata and escape-sequence fixture corpora.
• Add fuzzing for parser chunk boundaries and benchmark-driven packed-cell storage.
• Add native Windows rendering backends, accessibility, mutable link-decoration notifications and renderer-specific differential fixtures.

Any intentional behavioral difference from xterm.js must be recorded here before a stable release.

Current intentional difference: after grow-reflow removes the only physical row marker for an OSC 8 link but moves linked cells into a retained row, XtermSharp rebuilds the marker from the surviving cell references. The pinned xterm.js baseline drops the metadata while leaving cells with the link ID; XtermSharp preserves it to maintain resolvable buffer state.

The pinned addon-clipboard has no addon-level permissions or decoded payload limit, forwards arbitrary selection strings, replaces malformed UTF-8 and clears the clipboard when an OSC 52 payload contains arbitrary invalid Base64. XtermSharp requires explicit permissions, limits decoded payloads, validates selections and rejects malformed UTF-8 or Base64 without invoking the provider because malformed terminal input should not mutate host clipboard state. Empty payloads and ! remain explicit clear operations.