What causes "Failed to load benchmark provider from "${provider}"." in vitest-dev/vitest?

Inspect `error.cause` for the real import failure (resolution error, syntax error, runtime throw) and fix that root cause.

vitest-dev/vitest · error · Error

Failed to load benchmark provider from

Error message

Failed to load benchmark provider from "${provider}".

What it means

Vitest's benchmark system can load a custom `BenchmarkProvider` from a module path configured under `benchmark.provider`. This error wraps any failure thrown while importing that module via the module runner — the underlying import error is attached as `cause`. It means the module specifier itself could not be resolved, fetched, or evaluated.

Solutions

Inspect `error.cause` for the real import failure (resolution error, syntax error, runtime throw) and fix that root cause.
Confirm the path resolves from the project root — use a relative path or package name that the module runner can resolve.
Run the provider file standalone (`node --import tsx ./my-provider.ts`) to reproduce the top-level error outside Vitest.
If you did not intend to set a custom provider, remove `benchmark.provider` from config to fall back to the default tinybench-based provider.

Example fix

// before: benchmark.provider = './benchProvder' (typo)
// after: benchmark.provider = './benchProvider'

Defensive patterns

Strategy: try-catch

Validate before calling

try { await import.meta.resolve!(providerPath) } catch { throw new Error(`provider path '${providerPath}' does not resolve`) }

Type guard

null

Try / catch

try { bench = createBench(test, config, runner) } catch (e) { if (e.cause) console.error('underlying import error:', e.cause); throw e }

Prevention

Resolve the provider path from the project root before configuring it.
Run the provider file standalone with `node --import tsx path.ts` to surface top-level throws.
Lock the provider module's dependencies so an install miss does not break imports in CI.

When it happens

Trigger: Setting `benchmark.provider: './my-provider'` where the path is wrong, the file has a syntax error, throws during top-level execution, or the module runner transport fails to fetch it. The try/catch at benchmark.ts:104-112 catches anything rejected by `moduleRunner.import(provider)` and re-throws with this message plus the original as `cause`.

Common situations: Typo in the provider path; provider module imports a dependency that is not installed; provider is ESM but loaded in a CJS context that throws; network/filesystem error in a custom transport; provider module throws at the top level (e.g. reads `process.env.SOMETHING` that is undefined and dereferences it).

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/9df9f1c7aff6b389. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/runtime/benchmark.ts:108

 *
 * @experimental
 */
export interface BenchmarkProvider {
  run: (group: BenchmarkGroup) => Promise<BenchResult[]>
}

let cachedProvider: Promise<BenchmarkProvider> | undefined

async function loadProviderModule(
  provider: string,
  moduleRunner: TestModuleRunner,
): Promise<BenchmarkProvider> {
  let mod: Record<string, any>
  try {
    mod = await moduleRunner.import(provider)
  }
  catch (error) {
    throw new Error(
      `Failed to load benchmark provider from "${provider}".`,
      { cause: error },
    )
  }
  if (mod.default == null) {
    throw new Error(
      `Benchmark provider loaded from "${provider}" did not have a default export.`,
    )
  }
  return mod.default
}

/**
 * Resolves the benchmark provider for the current worker, importing a custom
 * provider module on first use. The result is cached for the lifetime of the
 * worker so a custom provider is imported at most once.
 */
function resolveBenchmarkProvider(

View on GitHub (pinned to 1fa9837ec2)