RocketChat/Rocket.Chat · error · Meteor.Error

The required "mid" body param is missing.

Error message

The required "mid" body param is missing.

What it means

Thrown by POST chat.followMessage (apps/meteor/server/api/v1/chat.ts:481) when this.bodyParams.mid is falsy before calling followMessage. Note it is a Meteor.Error with no error code - only the message text. On current servers the body schema (isChatFollowMessageLocalProps, requires mid with minLength 1) rejects a missing/empty mid first with a schema 400, so this throw is a legacy/defense-in-depth guard that mainly surfaces on older builds or when validation is bypassed.

Solutions

1. Always send { "mid": "<message id>" } in the body - mid is required and must be non-empty.
2. Upgrade the server so missing params fail fast in schema validation with a clear 400 instead of reaching the handler.
3. If you maintain a client, validate the payload against the published ChatFollowMessage schema (mid: string, minLength 1) before sending.
4. On the client, treat both this message and 'Body does not match schema' as the same class: caller forgot mid.

Example fix

// before
await rc.post('/api/v1/chat.followMessage', { }); // 400: mid required

// after
await rc.post('/api/v1/chat.followMessage', { mid: messageId });

const isFollowPayload = (p: { mid?: unknown }): p is { mid: string } =>
  typeof p.mid === 'string' && p.mid.length > 0;
if (!isFollowPayload(payload)) throw new Error('mid is required');
await rc.post('/api/v1/chat.followMessage', payload);

const isFollowPayload = (p: { mid?: unknown }): p is { mid: string } =>
  typeof p.mid === 'string' && p.mid.length > 0;

try {
  await rc.post('/api/v1/chat.followMessage', { mid });
} catch (e) {
  if (/"mid" body param is missing/i.test(e?.error ?? '') || e?.errorType === 'error-invalid-params') fixPayload();
  else throw e;
}

When it happens

Trigger: POST /api/v1/chat.followMessage with body lacking mid, with mid: "" or mid: null. On modern servers you usually get 'Body does not match schema' (400) instead; this exact message appears on servers predating body validation on this endpoint or when mid is explicitly undefined in crafted payloads.

Common situations: Integrations written against old Rocket.Chat versions (pre-schema-validation) re-surfacing after upgrades in reverse; JSON bodies built dynamically where mid is conditionally omitted; tests sending {} to probe validation behavior.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• error-emoji-param-not-provided
• error-invalid-message
• error-not-allowed
• error-param-required
• error-room-does-not-exist

AI-assisted analysis of RocketChat/Rocket.Chat@e4b8178b20 (2026-08-18). Data as JSON: /api/errors/a2dcba76572c2b2b. Report an issue: GitHub.

Appendix: source

Thrown at apps/meteor/server/api/v1/chat.ts:485

				401: validateUnauthorizedErrorResponse,
				200: ajv.compile<void>({
					type: 'object',
					properties: {
						success: {
							type: 'boolean',
							enum: [true],
						},
					},
					required: ['success'],
					additionalProperties: false,
				}),
			},
		},
		async function action() {
			const { mid } = this.bodyParams;

			if (!mid) {
				throw new Meteor.Error('The required "mid" body param is missing.');
			}

			await followMessage(this.user, { mid });

			return API.v1.success();
		},
	)
	.post(
		'chat.unfollowMessage',
		{
			authRequired: true,
			body: isChatUnfollowMessageLocalProps,
			response: {
				400: validateBadRequestErrorResponse,
				401: validateUnauthorizedErrorResponse,
				200: ajv.compile<void>({
					type: 'object',
					properties: {

View on GitHub (pinned to e4b8178b20)