WaveCrux — Waveform Analysis for RTL

The waveform is not the hard part. Working out what the waveform means is.

WaveCrux puts a full debug-analysis layer in a VSCode tab: nine protocol decoders with a transaction table, X-trace to find where an unknown came from, waveform diff across two runs, FSM state views, and switching-activity analysis. Then it connects that tab to the rest of your toolchain — including the tools that are not running inside your editor.

Open a .vcd, .fst, .ghw, .lxt or .lxt2 and it opens here, in an editor tab, beside the RTL that produced it.

• Registries: Marketplace · Open VSX (Cursor, Windsurf, VSCodium, Theia)
• Licence: Apache-2.0 · Home: wavecrux.app

The analysis layer

Everything below ships in the extension. No account, no key, no separate download — it is the WaveCrux open-core build, embedded.

Rendering, navigation, formatting and netlist search are table stakes and are built on wellen compiled to WebAssembly — the same parsing engine several other open-source viewers use. We are not claiming to draw a nicer square wave. The claim is everything above.

Built for the editor, not merely hosted in it

• Real editor integration. A CustomReadonlyEditorProvider, so waveforms are tabs: they split, they go to a second editor group, they restore with the window, and workbench.editorAssociations works on them.
• Live theme bridge. The viewer follows your VSCode theme — light, dark and high-contrast — with a WCAG contrast floor enforced on signal colours, so a high-contrast theme does not produce an unreadable trace.
• Large files stream. Bytes reach the viewer in 4 MiB chunks rather than as one allocation, with a 256 MiB ceiling. Cold start measured at 246–406 ms.
• RTL value annotation — the feature that is better here than on the desktop. Turn it on and signal values from the waveform render as inline decorations in your own Verilog/VHDL, following the waveform cursor. The desktop app needs a second pane for this; in an editor, your source is already open at the line you are reading. Only stems-exact name matches are annotated and an ambiguous name is shown as ambiguous rather than guessed. Off until you opt in (edacrux.rtlAnnotation.enabled).

Connected to tools that are not in your editor

WaveCrux, LintCrux, SimCrux and NetCrux speak CXP, a cross-process peer protocol. That is the part an in-editor extension API cannot do: CXP reaches the desktop applications, on the same machine, over loopback — so a running NetCrux or LintCrux desktop session is a peer of this window.

Your VSCode window is one CXP peer no matter how many of the four extensions you install: one identity, one manifest, one heartbeat, capabilities composed from whatever is installed. A peer that asks this window to open a source location gets the file opened at the right line.

Install the EDACrux Suite pack to get all four at once.

Getting started

1. Open any .vcd, .fst, .ghw, .lxt or .lxt2 file in the explorer.
2. It opens in a WaveCrux tab. Add signals from the hierarchy and navigate. (If your editor opens a .vcd as plain text instead, see Default editor for .vcd.)
3. Optional: run EDACrux: Toggle RTL Value Annotation with a Verilog or VHDL file open to see cursor values inline in your source.

Default editor for .vcd

WaveCrux claims .vcd with default priority, which VSCode honours. Some VSCode forks that install from Open VSX open .vcd in the plain text editor anyway and list WaveCrux only under Reopen Editor With.... When that happens WaveCrux asks once whether to make it the default for *.vcd. Say yes and it writes workbench.editorAssociations in your user settings and reopens the tab; say no or dismiss the message and it never asks again. Where the default already works the question never appears, and an existing association for .vcd is left alone. You can always change it later in workbench.editorAssociations.

Language ids

RTL annotation needs the editor to know a file is Verilog, SystemVerilog or VHDL. A fresh editor with no HDL language extension calls .v and .sv Plain Text, so this extension registers those three language ids for .v .vh .sv .svh .vhd .vhdl, and nothing else (no grammar, no highlighting). An HDL language extension you install keeps providing the highlighting; VSCode merges the registrations by id. If another extension also claims .v, choose with files.associations.

Selecting a signal, inside one window

Selecting a signal in a waveform tab reveals its declaration in the editor when edacrux.crossProbe.followWaveformSelection is on. It is off by default, so nothing happens in the editor when you click. The other EDACrux extensions in the same window do not receive waveform selections: the window is one CXP peer, and a selection goes to a peer in another application only when you send it, from the Cross-Probe panel or with EDACrux: Send Selection to Crux App. The WaveCrux output channel says this once per session when a selection is not followed.

Settings

Colours

The annotations take their colour from your theme and stay muted by default. Each has its own colour id, so a theme can style it, and you can raise the contrast (for a projector or a screen recording, say) in workbench.colorCustomizations without recolouring CodeLenses:

"workbench.colorCustomizations": {
  "edacrux.rtlAnnotationForeground": "#4fc1ff"
}

Commands

Send and Highlight take the identifier under your cursor to a running Crux app: one connected app is sent to directly, several are offered in a quick pick.

What this extension does not do — stated plainly

• FSDB is refused, with an explanation. .fsdb requires Synopsys libraries that cannot be redistributed. The extension tells you that instead of failing obscurely.
• NetCrux → waveform highlight is not wired yet. WaveCrux's surface advertises no highlight capability rather than accepting the request and dropping it. When the webview command lands, the capability is advertised in the same change.
• Restricted workspaces. It runs with limited support in a folder you have not trusted. Waveforms open, decode and cross-probe normally: the extension only reads the files you open and never runs a program. One setting is held back: a workspace value for edacrux.rtlAnnotation.enabled is ignored, because an untrusted folder should not put text into your source. Switch it on in your own user settings, or trust the folder.
• Pro and Enterprise features are not bundled. No AI debug advisor, no SV assertion visualization, no collaborative viewing, no Stage Pro custom widget SDK. Those live in WaveCrux Desktop and are linked, never quietly disabled here.
• The desktop app is still the deeper tool for multi-tab workspaces, the Stage instrument panel, interactive VCD over a pipe, and the WCP remote control API.

Telemetry

Off unless you have VSCode telemetry on. The extension checks vscode.env.isTelemetryEnabled at send time, not once at startup, so turning telemetry off in VSCode turns it off here immediately.

Localization

English, 简体中文, 日本語 and 한국어 — hand-translated, commands and settings included.

The rest of the suite

Built by Ferrite Engineering. Apache-2.0. edacrux.app