sv0 for VS Code and Cursor

Status: Preview (F0). This extension currently provides lexical editing support only. It does not provide semantic diagnostics, IntelliSense, debugging, or verification — those arrive with the R0.1 release once a compiler-backed sv0-lsp language server exists upstream. See Maturity below before filing an issue about "no autocomplete" or "no error checking."

Editor support for sv0, a systems programming language with static contract verification.

Supported editors

• Visual Studio Code (desktop), engine >=1.85.0
• Cursor (desktop), current stable — verified independently of VS Code
• vscode.dev / github.dev — lexical features only, no remote extension host required

What works today (F0)

• Syntax highlighting for .sv0 files
• Comments, bracket matching, auto-closing/surrounding pairs, folding
• Snippets for fn, main, struct, enum, match, if, while, for, requires, ensures, loop_invariant
• Phase-0 document formatting: strips trailing whitespace, strips trailing blank lines, ensures exactly one final newline — identical to the toolchain's scripts/fmt_sv0.py. Does not re-indent, reorder, or reflow code.
• sv0: Show Language Server Status — always explains that no semantic server is configured yet in F0

Syntax highlighting is not a correctness signal. The highlighter (a TextMate grammar) classifies tokens by shape alone — it has no parser, no type checker, and no knowledge of sv0's semantics. A file with mismatched braces, an unterminated string, or an outright type error will still be colored as if it were valid sv0; the grammar's job is only to make real code legible, not to validate it. Highlighting looking "normal" tells you nothing about whether the file compiles. Real error detection arrives with the compiler-backed diagnostics in R0.1.

What does not work yet

• Diagnostics (errors/warnings from the compiler)
• Go to definition, find references, rename, hover, completion, signature help
• AST-aware ("real") formatting
• Build, run, verify, or debug commands
• Any network request or telemetry — the extension makes none, ever, in F0 or R0.1

Maturity

This extension follows a two-layer delivery strategy (see the governing specification): F0 ships safe declarative language support with zero semantic pretense. R0.1 adds semantic intelligence only through a compiler-backed, versioned language-server protocol contract — never by scraping compiler stderr or embedding a second parser. Until sv0-lsp ships upstream, this extension will not claim IntelliSense.

Trust and security

• Opening, previewing, or highlighting a file never executes code, starts a process, or makes a network request — in F0, and in every untrusted workspace regardless of release.
• This extension collects no telemetry.
• Source text, diagnostics, and project metadata never leave the workspace host.

See SECURITY.md for the vulnerability-reporting process (once published) and SUPPORT.md for the compatibility matrix and known gaps.

Setup

Install from the Visual Studio Marketplace once published (sv0-toolchain.sv0-lang). No configuration is required for F0 — open any .sv0 file.

Source authority

This extension is independently versioned and consumes the following upstream repositories as read-only authorities; it never forks grammar or type rules:

License

MIT — see LICENSE.