linshenkx/prompt-optimizer · error · VariableError

VALUE_TOO_LONG

VALUE_TOO_LONG

Error message

Variable value too long: ${value.length} > ${VARIABLE_VALIDATION.MAX_VALUE_LENGTH}

What it means

VariableManager.setVariable throws VariableError with code VALUE_TOO_LONG when the value string exceeds VARIABLE_VALIDATION.MAX_VALUE_LENGTH. This is a guard against unbounded storage growth (values are persisted via saveToStorage, e.g. to localStorage). The error message reports both the actual length and the limit.

Solutions

1. Truncate or reject long values client-side before calling setVariable
2. Store large payloads out-of-band (e.g. an asset/image storage service) and keep only a reference ID in the variable
3. Check VARIABLE_VALIDATION.MAX_VALUE_LENGTH and surface a form validation message instead of relying on the throw

Example fix

// before
variableManager.setVariable('doc', hugeString)

// after
if (hugeString.length > VARIABLE_VALIDATION.MAX_VALUE_LENGTH) {
  throw new Error(`Value exceeds ${VARIABLE_VALIDATION.MAX_VALUE_LENGTH} chars`)
}
variableManager.setVariable('doc', hugeString)

const MAX = VARIABLE_VALIDATION.MAX_VALUE_LENGTH
if (value.length > MAX) {
  throw new RangeError(`Value too long: ${value.length} > ${MAX}`)
}

const fitsVariableLimit = (value: string): boolean =>
  value.length <= VARIABLE_VALIDATION.MAX_VALUE_LENGTH

try {
  vm.setVariable(name, value)
} catch (e) {
  if (e instanceof VariableError && e.code === 'VALUE_TOO_LONG') {
    value = value.slice(0, VARIABLE_VALIDATION.MAX_VALUE_LENGTH)
    vm.setVariable(name, value)
  } else throw e
}

When it happens

Trigger: Calling setVariable(name, value) with value.length > VARIABLE_VALIDATION.MAX_VALUE_LENGTH. Typical with base64-encoded images, large JSON blobs, or pasted text stored as a variable.

Common situations: Storing base64 image data or long documents in a variable; importing variables from a file created under different limits; localStorage quota issues that surface as oversized payloads.

Understand the failure class

Background: payload too large / request exceeds maximum size: why libraries cap bytes and how to fix oversize payloads — this error's family across 50 libraries.

Related errors

• Favorite entry exceeds hard limit of
• favorites payload exceeds hard limit of
• Missing variables
• PREDEFINED_VARIABLE_OVERRIDE
• variables[ ] is missing a valid "name" field.

AI-assisted analysis of linshenkx/prompt-optimizer@3e677b1d9f (2026-08-27). Data as JSON: /api/errors/6a8aee93f0f3dc13. Report an issue: GitHub.

Appendix: source

Thrown at packages/ui/src/services/VariableManager.ts:130

      throw new VariableError(
        `Invalid variable name: ${name}. ${reasonText}`,
        name,
        undefined,
        'INVALID_VARIABLE_NAME'
      );
    }

    if (this.isPredefinedVariable(name)) {
      throw new VariableError(
        `Cannot override predefined variable: ${name}`,
        name,
        undefined,
        'PREDEFINED_VARIABLE_OVERRIDE'
      );
    }

    if (value.length > VARIABLE_VALIDATION.MAX_VALUE_LENGTH) {
      throw new VariableError(
        `Variable value too long: ${value.length} > ${VARIABLE_VALIDATION.MAX_VALUE_LENGTH}`,
        name,
        undefined,
        'VALUE_TOO_LONG'
      );
    }

    this.customVariables[name] = value;
    this.saveToStorage();
  }

  getVariable(name: string): string | undefined {
    return this.customVariables[name];
  }

  deleteVariable(name: string): void {
    if (this.isPredefinedVariable(name)) {
      throw new VariableError(

View on GitHub (pinned to 3e677b1d9f)