parcel-bundler/parcel · error · Error

Supplied WorkerFarm is ending

Error message

Supplied WorkerFarm is ending

What it means

Parcel can accept an externally-supplied WorkerFarm via `options.workerFarm` (e.g. to share workers across multiple Parcel instances). Before adopting it, Parcel checks the farm's `ending` flag: a farm that is already shutting down cannot accept new work and would deadlock the build. The check fails fast to surface the lifecycle misuse.

Source

Thrown at packages/core/core/src/Parcel.js:117

      return;
    }

    await initSourcemaps;
    await initRust?.();

    let resolvedOptions: ParcelOptions = await resolveOptions(
      this.#initialOptions,
    );
    this.#resolvedOptions = resolvedOptions;

    let {config} = await loadParcelConfig(resolvedOptions);
    this.#config = new ParcelConfig(config, resolvedOptions);

    setFeatureFlags(resolvedOptions.featureFlags);

    if (this.#initialOptions.workerFarm) {
      if (this.#initialOptions.workerFarm.ending) {
        throw new Error('Supplied WorkerFarm is ending');
      }
      this.#farm = this.#initialOptions.workerFarm;
    } else {
      this.#farm = createWorkerFarm({
        shouldPatchConsole: resolvedOptions.shouldPatchConsole,
        shouldTrace: resolvedOptions.shouldTrace,
      });
    }

    await resolvedOptions.cache.ensure();

    let {dispose: disposeOptions, ref: optionsRef} =
      await this.#farm.createSharedReference(resolvedOptions, false);
    this.#optionsRef = optionsRef;

    this.#disposable = new Disposable();
    if (this.#initialOptions.workerFarm) {
      // If we don't own the farm, dispose of only these references when

View on GitHub (pinned to 59484858a1)

Solutions

1. Do not call `workerFarm.end()` before passing it to a new Parcel instance.
2. Create a fresh WorkerFarm via `createWorkerFarm()` for each independent Parcel, or omit `workerFarm` so Parcel manages its own.
3. If sharing, end the farm only after all Parcel instances are disposed.

Example fix

// before
farm.end();
const p = new Parcel({workerFarm: farm});

// after
// drop the end() call, or create a new farm:
const p = new Parcel({workerFarm: createWorkerFarm()});

// Reject an ending farm before handing it to Parcel.
if (options.workerFarm && options.workerFarm.ending) {
  throw new Error('workerFarm is ending; create a new one');
}

function isActiveWorkerFarm(f: ?{ending?: boolean}): boolean {
  return f != null && f.ending !== true;
}

When it happens

Trigger: Constructing `new Parcel({...workerFarm})` where `workerFarm.end()` was already called (or is mid-shutdown).

Common situations: Sharing one WorkerFarm across several Parcel instances and ending it after the first finishes; reusing a farm from a disposed Parcel.

Related errors

• Cannot add a worker call if workerfarm is ending.
• Parcel is already profiling
• Parcel is not profiling
• Please provide a worker path!
• No dynamic require possible: ${workerPath}

AI-assisted analysis of parcel-bundler/parcel@59484858a1 (2026-08-13). Data as JSON: /api/errors/591677a82965197c. Report an issue: GitHub.