deepseek-ai/deepseek-harness · error · LlmError

UNSUPPORTED_REASONING_EFFORT

UNSUPPORTED_REASONING_EFFORT

Error message

DeepSeek does not support reasoning effort "${effort}"

What it means

Error "DeepSeek does not support reasoning effort "${effort}"" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/llm/llm-deepseek/src/serialize.ts:74

  byteQuantum?: number
  /** Image-count removal step applied after the request exceeds its count bound. */
  countQuantum?: number
}

/** Durable message and image ordinal used in provider diagnostics. */
export interface ImageWireLocation {
  message: number
  image: number
}

const TOOL_RESULT_IMAGE_TEXT = 'Attached image(s) from tool result:'

/** Validate the adapter-owned effort before resolving its DeepSeek wire fields. */
function reasoningEffort(effort: NonNullable<GenerateOptions['reasoningEffort']>): 'off' | 'low' | 'high' | 'max' {
  if (effort === 'off' || effort === 'low' || effort === 'high' || effort === 'max') {
    return effort as 'off' | 'low' | 'high' | 'max'
  }
  throw new LlmError(
    `DeepSeek does not support reasoning effort "${effort}"`,
    'UNSUPPORTED_REASONING_EFFORT',
  )
}

/** Resolve one legal thinking/effort pair without exposing `off` as a wire effort. */
function resolveThinking(options: GenerateOptions, defaults: RequestDefaults): ResolvedThinking {
  if (options.purpose === 'session-title') return { thinking: 'disabled' }
  const effort = options.reasoningEffort === undefined
    ? defaults.reasoningEffort
    : reasoningEffort(options.reasoningEffort)
  if (defaults.thinking === 'disabled' && effort !== undefined && effort !== 'off') {
    throw new LlmError(
      `DeepSeek deployment does not support reasoning effort "${effort}"`,
      'UNSUPPORTED_REASONING_EFFORT',
    )
  }
  if (effort === 'off') return { thinking: 'disabled' }

View on GitHub (pinned to b150a551b8)

Solutions

1. Use a reasoning effort the DeepSeek model supports, or omit the effort.

When it happens

Trigger: Thrown at packages/llm/llm-deepseek/src/serialize.ts:74 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/10abcfeb17cfa141. Report an issue: GitHub.