zed-industries/zed · error

Failed to initialize Tokio

Error message

Failed to initialize Tokio

What it means

gpui_tokio::init builds a multi-thread Tokio runtime and expects the runtime builder to succeed; failure means Tokio could not start its worker threads or I/O drivers (thread spawn/resource failure), so the Tokio bridge cannot be registered as a GPUI global.

Source

Thrown at crates/gpui_tokio/src/gpui_tokio.rs:18

use std::future::Future;

use gpui::{App, AppContext, Global, ReadGlobal, Task};
use gpui_util::defer;

pub use tokio::task::JoinError;

/// Initializes the Tokio wrapper using a new Tokio runtime with 2 worker threads.
///
/// If you need more threads (or access to the runtime outside of GPUI), you can create the runtime
/// yourself and pass a Handle to `init_from_handle`.
pub fn init(cx: &mut App) {
    let runtime = tokio::runtime::Builder::new_multi_thread()
        // Since we now have two executors, let's try to keep our footprint small
        .worker_threads(2)
        .enable_all()
        .build()
        .expect("Failed to initialize Tokio");

    let handle = runtime.handle().clone();
    cx.set_global(GlobalTokio {
        owned_runtime: Some(runtime),
        handle,
    });
}

/// Initializes the Tokio wrapper using a Tokio runtime handle.
pub fn init_from_handle(cx: &mut App, handle: tokio::runtime::Handle) {
    cx.set_global(GlobalTokio {
        owned_runtime: None,
        handle,
    });
}

struct GlobalTokio {
    owned_runtime: Option<tokio::runtime::Runtime>,

View on GitHub (pinned to f4178619ac)

Solutions

1. Check thread/fd limits that prevent Tokio worker or driver startup
2. Verify init is called once; double init of the global would also be invalid
3. Create the runtime yourself and use init_from_handle for custom configurations

When it happens

Trigger: Thrown at crates/gpui_tokio/src/gpui_tokio.rs:18 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@f4178619ac (2026-08-20). Data as JSON: /api/errors/0b5f9199e2e70450. Report an issue: GitHub.