biomejs/biome · error

failed to spawn scanner thread

Error message

failed to spawn scanner thread

What it means

Error "failed to spawn scanner thread" thrown in biomejs/biome.

Solutions

1. Check system thread limits (ulimit, cgroup constraints) if spawning the scanner thread fails.
2. Reduce configured scanner parallelism before starting the workspace server.

Example fix

// Inspect the attached io::Error source for OS-level spawn failure details

When it happens

Trigger: Thrown at crates/biome_service/src/scanner.rs:252 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of biomejs/biome@0fca643d22 (2026-08-20). Data as JSON: /api/errors/f06e8e1c3b6e6c0d. Report an issue: GitHub.

Appendix: source

Thrown at crates/biome_service/src/scanner.rs:276

        project_key: ProjectKey,
        project_path: &Utf8Path,
        dependencies: ModuleDependencies,
        trigger: IndexTrigger,
    ) -> Result<Vec<Diagnostic>, WorkspaceError> {
        let scan_kind = self
            .get_scan_kind_for_project(project_key)
            .ok_or_else(WorkspaceError::no_project)?;

        let (interner, _path_receiver) = PathInterner::new();

        let (diagnostics_sender, diagnostics_receiver) = unbounded();
        let collector = DiagnosticsCollector::new(false);

        let diagnostics = thread::scope(|scope| {
            let handler = thread::Builder::new()
                .name("biome::scanner".to_string())
                .spawn_scoped(scope, || collector.run(diagnostics_receiver))
                .expect("failed to spawn scanner thread");

            // The traversal context is scoped to ensure all the channels it
            // contains are properly closed once scanning finishes.
            let mut ctx = ScanContext {
                workspace,
                project_key,
                interner,
                diagnostics_sender,
                evaluated_paths: Default::default(),
                scan_kind,
                trigger,
                watch: true,
                dependencies: Default::default(),
            };

            let (_duration, folders_to_watch) =
                scan_dependencies(project_path, dependencies, &mut ctx);

View on GitHub (pinned to 0fca643d22)