deepseek-ai/deepseek-harness · error · PresetMountError

agent-presets: preset "${presetId}" failed to mount: ${mount

Error message

agent-presets: preset "${presetId}" failed to mount: ${mountDetail(error)} (${preset.path})

What it means

Error "agent-presets: preset "${presetId}" failed to mount: ${mountDetail(error)} (${preset.path})" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/preset/agent-presets/src/mount.ts:379

    const leaked = leakedServices(agentCtx, fiber)
    if (leaked.length > 0) {
      throw new Error(
        `row(s) published process-global service(s) [${leaked.join(', ')}]; `
        + 'a preset service must sit behind an `isolate` realm or move to the host composition',
      )
    }
    mounts.add({ presetId: preset.id, fiber, key: scopeOf(agentCtx) })
  } catch (error) {
    try {
      await handle.dispose()
    /* v8 ignore next 5 -- teardown of a subtree nothing else references has no
       observed failure mode; the guard exists so a teardown error cannot
       replace the mount diagnostic the caller needs. */
    } catch {
      // Swallows only this subtree's teardown failure. The mount error below is
      // the actionable one, and the discarded fiber is unreachable either way.
    }
    throw new PresetMountError(preset.id, `${mountDetail(error)} (${preset.path})`, { cause: error })
  }
}

View on GitHub (pinned to b150a551b8)

Solutions

1. Fix the preset per the included mount detail, then mount again.

When it happens

Trigger: Thrown at packages/preset/agent-presets/src/mount.ts:379 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/6839cdac1ac0842a. Report an issue: GitHub.