zed-industries/zed · error

Failed to create Wasmtime engine

Error message

Failed to create Wasmtime engine

What it means

One-time LazyLock panic while constructing the process-wide Wasmtime engine for tree-sitter WASM grammars. wasmtime::Engine::new with the default Config only fails on environmental problems — e.g., inability to map memory, incompatible CPU feature detection, or compilation backend initialization failure. Once it panics, every subsequent grammar load through this LazyLock re-poisons it.

Source

Thrown at crates/language/src/language.rs:167

    });
    // Tree-sitter auto-resets the parser at the end of a successful parse,
    // but the cancellation paths (progress callback returning `Break`,
    // cancelled balancing) leave outstanding state on the parser. The next
    // call to `parse_with_options` would then *resume* that cancelled parse
    // instead of starting fresh.
    parser.reset();
    parser.set_included_ranges(&[]).unwrap();
    let result = func(&mut parser);
    PARSERS.lock().push(parser);
    result
}

pub fn with_query_cursor<F, R>(func: F) -> R
where
    F: FnOnce(&mut QueryCursor) -> R,
{
    let mut cursor = QueryCursorHandle::new();
    func(cursor.deref_mut())
}

static WASM_ENGINE: LazyLock<wasmtime::Engine> = LazyLock::new(|| {
    wasmtime::Engine::new(&wasmtime::Config::new()).expect("Failed to create Wasmtime engine")
});

/// A shared grammar for plain text, exposed for reuse by downstream crates.
pub static PLAIN_TEXT: LazyLock<Arc<Language>> = LazyLock::new(|| {
    Arc::new(Language::new(
        LanguageConfig {
            name: "Plain Text".into(),
            soft_wrap: Some(SoftWrap::EditorWidth),
            autoclose_before: ")]}".into(),
            matcher: (LanguageMatcher {
                path_suffixes: vec!["txt".to_owned()],
                first_line_pattern: None,
                modeline_aliases: vec!["text".to_owned(), "txt".to_owned()],
            })

View on GitHub (pinned to 9d272b0363)

Solutions

1. Log the wasmtime::Error to identify the environmental cause (memory limits, target features)
2. Retry engine construction with a reduced/wasm engine config (e.g., disable parallel compilation or tune memory settings)
3. If WASM grammars are unsupported in the environment, skip registering them instead of poisoning the global

When it happens

Trigger: Thrown at crates/language/src/language.rs:165 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@9d272b0363 (2026-08-20). Data as JSON: /api/errors/c8c036aac136458e. Report an issue: GitHub.