danny-avila/LibreChat · error · AgentRunEnvelopeError

${path}.${key} must not be an accessor property

Error message

${path}.${key} must not be an accessor property

What it means

Thrown by cloneJsonValue when a plain object's own enumerable property is an accessor (defined with get/set) rather than a data value. The descriptor lacks an own 'value' key. Getters can throw or have side effects, so the clone refuses to invoke them and demands a concrete value.

Source

Thrown at packages/api/src/agents/envelope.ts:177

        throw new AgentRunEnvelopeError(`${path} contains sparse array entries`);
      }
      return cloned;
    }

    const prototype = Object.getPrototypeOf(value);
    if (prototype !== Object.prototype && prototype !== null) {
      const typeName = value.constructor?.name ?? 'object';
      throw new AgentRunEnvelopeError(`${path} contains a non-plain ${typeName} value`);
    }

    const cloned: { [key: string]: unknown } = {};
    for (const key of Object.getOwnPropertyNames(value)) {
      const descriptor = Object.getOwnPropertyDescriptor(value, key);
      if (descriptor?.enumerable !== true) {
        throw new AgentRunEnvelopeError(`${path}.${key} must be an enumerable property`);
      }
      if (!Object.prototype.hasOwnProperty.call(descriptor, 'value')) {
        throw new AgentRunEnvelopeError(`${path}.${key} must not be an accessor property`);
      }
      const propertyValue: unknown = descriptor.value;
      Object.defineProperty(cloned, key, {
        configurable: true,
        enumerable: true,
        writable: true,
        value: cloneJsonValue(propertyValue, `${path}.${key}`, ancestors, depth + 1),
      });
    }
    return cloned;
  } finally {
    ancestors.delete(value);
  }
}

function createPrincipal(input: AgentRunPrincipalInput | null | undefined): AgentRunPrincipal {
  const userId = assertNonEmptyString(input?.id, 'principal.id');
  const principal: AgentRunPrincipal = { userId };

View on GitHub (pinned to 5ff282f900)

Solutions

  1. Evaluate getters into plain values: build { k: obj.k } by reading each field explicitly.
  2. Replace accessor descriptors with data descriptors (defineProperty with value).
  3. Use Object.entries(obj) to harvest concrete values into a fresh literal.

Example fix

// before
Object.defineProperty(meta, 'summary', { get() { return title + ' - ' + body; }, enumerable: true });
createAgentRunEnvelope({ protocol, requestId, receivedAt, principal, payload: { meta } });

// after
const meta = { summary: title + ' - ' + body };
createAgentRunEnvelope({ protocol, requestId, receivedAt, principal, payload: { meta } });
Defensive patterns

Strategy: validation

Validate before calling

function objectHasOnlyDataValues(obj: Record<string, unknown>): boolean {
  return Object.getOwnPropertyNames(obj).every((k) => {
    const d = Object.getOwnPropertyDescriptor(obj, k);
    return !!d && Object.prototype.hasOwnProperty.call(d, 'value');
  });
}
function materializeGetters<T extends Record<string, unknown>>(obj: T): Record<string, unknown> {
  const out: Record<string, unknown> = {};
  for (const k of Object.keys(obj)) out[k] = obj[k]; // invoke getter, store value
  return out;
}

Type guard

function isDataPropsOnly(obj: Record<PropertyKey, unknown>): boolean {
  return Object.getOwnPropertyNames(obj).every((k) => {
    const d = Object.getOwnPropertyDescriptor(obj, k);
    return !!d && Object.prototype.hasOwnProperty.call(d, 'value');
  });
}

Try / catch

try {
  const env = createAgentRunEnvelope(input);
} catch (e) {
  if (e instanceof AgentRunEnvelopeError && /accessor property/.test(e.message)) {
    input.payload = JSON.parse(JSON.stringify(input.payload)) as typeof input.payload;
    // getters are invoked and results stored as plain values
  } else throw e;
}

Prevention

When it happens

Trigger: Object.defineProperty(obj, 'k', { get() {...}, enumerable: true }), a class instance turned plain-ish via assignment but still carrying getters, or a Proxy whose trap surfaces as an accessor descriptor.

Common situations: Computed/derived fields exposed as getters on a config object; interop with libraries that expose lazy properties; spreading a class instance into a plain object while getters survive.

Related errors

AI-assisted analysis of danny-avila/LibreChat@5ff282f900 (2026-08-12). Data as JSON: /api/errors/1a60a5d037684188. Report an issue: GitHub.