langgenius/dify · error · ValidationError

Parameter '${key}' exceeds maximum size of ${MAX_DICT_LENGTH

Error message

Parameter '${key}' exceeds maximum size of ${MAX_DICT_LENGTH} items

What it means

Thrown by validateParams() in validation.ts:107 as a ValidationError. Any record/object-valued query or body param with more than 100 keys (MAX_DICT_LENGTH) is rejected. The key name is interpolated.

Source

Thrown at sdks/nodejs-client/src/client/validation.ts:107

    // Only check max length for strings; empty strings are allowed for optional params
    // Required fields are validated at method level via ensureNonEmptyString
    if (typeof value === 'string') {
      if (value.length > MAX_STRING_LENGTH) {
        throw new ValidationError(
          `Parameter '${key}' exceeds maximum length of ${MAX_STRING_LENGTH} characters`,
        )
      }
    } else if (Array.isArray(value)) {
      if (value.length > MAX_LIST_LENGTH) {
        throw new ValidationError(
          `Parameter '${key}' exceeds maximum size of ${MAX_LIST_LENGTH} items`,
        )
      }
    } else if (isRecord(value)) {
      if (Object.keys(value).length > MAX_DICT_LENGTH) {
        throw new ValidationError(
          `Parameter '${key}' exceeds maximum size of ${MAX_DICT_LENGTH} items`,
        )
      }
    }

    if (key === 'user' && typeof value !== 'string') {
      throw new ValidationError(`Parameter '${key}' must be a string`)
    }
    if ((key === 'page' || key === 'limit' || key === 'page_size') && !Number.isInteger(value)) {
      throw new ValidationError(`Parameter '${key}' must be an integer`)
    }
    if (key === 'files' && !Array.isArray(value) && typeof value !== 'object') {
      throw new ValidationError(`Parameter '${key}' must be a list or dict`)
    }
    if (key === 'rating' && value !== 'like' && value !== 'dislike') {
      throw new ValidationError(`Parameter '${key}' must be 'like' or 'dislike'`)
    }
  })
}

View on GitHub (pinned to ef8544b173)

Solutions

  1. Reduce the dict to only the keys the server consumes; prune unknown or unused fields.
  2. Move large structured data to a dedicated storage endpoint and reference it by id.
  3. Validate Object.keys(value).length upstream and warn the caller.

Example fix

// before
await client.chat('fx', { query, user, inputs: entireFeatureFlagMap })

// after
const inputs = Object.fromEntries(
  Object.entries(entireFeatureFlagMap).slice(0, 100)
)
await client.chat('fx', { query, user, inputs })
Defensive patterns

Strategy: validation

Validate before calling

const MAX_DICT_LENGTH = 100
function assertBoundedDicts(params: Record<string, unknown>) {
  for (const [k, v] of Object.entries(params)) {
    if (v !== null && typeof v === 'object' && !Array.isArray(v) && Object.keys(v).length > MAX_DICT_LENGTH) {
      throw new Error(`Parameter '${k}' exceeds ${MAX_DICT_LENGTH} keys`)
    }
  }
}

Type guard

function isBoundedDictParams(params: Record<string, unknown>, max = 100): boolean {
  return Object.values(params).every((v) => {
    if (v === null || typeof v !== 'object' || Array.isArray(v)) return true
    return Object.keys(v).length <= max
  })
}

Try / catch

try {
  await client.chat('fx', payload)
} catch (err) {
  if (err instanceof Error && /exceeds maximum size/.test(err.message) && /items/.test(err.message)) {
    // reduce inputs dict and retry
  } else throw err
}

Prevention

When it happens

Trigger: Calling an endpoint with an inputs object, metadata object, or config object containing > 100 keys. Triggered from the HTTP-layer validateParams via isRecord() at validation.ts:104.

Common situations: Passing a large dynamic metadata dict; UI-generated configs with many optional keys; serializing feature flags into inputs.

Related errors

AI-assisted analysis of langgenius/dify@ef8544b173 (2026-08-12). Data as JSON: /api/errors/f4b1748a2de9f01d. Report an issue: GitHub.