thread/reply

Reply to a Gmail thread by thread ID, adding a new message to the existing conversation.

vs. message/reply: Use thread/reply when you have a threadId and want to reply to the thread (optionally targeting a specific message with messageId). Use message/reply when you have a specific messageId and want to reply to that exact message in its thread.

When to Use

AI-generated thread responses: After fetching the full thread with thread/get and generating a context-aware reply with an AI agent, post the reply back to the thread.
Automated support responses: A support workflow identifies the thread via a trigger, processes the inquiry, and replies to the thread with the answer or acknowledgment.
Thread-level workflow notifications: Send status update messages to an existing email conversation thread when a related workflow task is completed.
Follow-up scheduling: A CRM trigger fires when a lead has been inactive for 7 days — reply to the existing email thread with a follow-up message.
Approval outcome notification: After a Human-in-the-Loop approves or rejects a request, reply to the original email thread with the decision and next steps.

Configuration

Connection

Field	Type	Description
`credentialId`	Guid required	OAuth2 credential ID from BizFirst Credentials Manager. Requires `gmail.send` scope.

Operation Fields

Field	Type	Default	Description
`threadId`	string required	—	Gmail thread ID to reply to. The reply is added as a new message in this thread.
`message`	string required	—	Reply body content. HTML or plain text depending on `emailType`.
`messageId`	string optional	—	Specific message within the thread to reply to. When omitted, replies to the most recent message in the thread.
`emailType`	enum optional	`html`	Content type: `html` or `text`.
`senderName`	string optional	—	Display name for the replying sender.
`ccList`	string optional	—	Comma-separated CC addresses for the reply.
`bccList`	string optional	—	Comma-separated BCC addresses for the reply.
`attachmentBinaryFields`	string[] optional	—	Binary field names from upstream node outputs to attach to the reply.
`replyToSenderOnly`	bool optional	`false`	When `true`, replies only to the original sender. When `false`, replies to all participants (Reply-All).

Sample Configuration

{
  "nodeType": "Gmail",
  "operation": "thread/reply",
  "credentialId": "a3f9d12b-44e1-4c89-b7d2-9f0a1e2b3c4d",
  "threadId": "{{support.gmailThreadId}}",
  "message": "<p>Dear {{customer.name}},</p><p>Your request has been processed. Here is the outcome: {{resolution.summary}}</p>",
  "emailType": "html",
  "senderName": "BizFirst Support",
  "replyToSenderOnly": true
}

Validation Errors

Error	Cause	Resolution
`MISSING_FIELD: threadId`	`threadId` is empty	Provide a valid Gmail thread ID
`MISSING_FIELD: message`	Reply body is empty	Provide non-empty message content
`THREAD_NOT_FOUND`	Thread does not exist or is inaccessible	Verify thread ID comes from the authenticated account
`MESSAGE_NOT_FOUND`	Optional `messageId` not found in the thread	Verify the message ID belongs to the specified thread
`INVALID_CREDENTIAL`	OAuth token expired or credential not found	Re-authenticate in BizFirst Credentials Manager
`QUOTA_EXCEEDED`	Daily send limit reached	Wait for quota reset or switch to Google Workspace account

Output

Success Port

Field	Type	Description
`messageId`	string	Gmail message ID of the new reply
`threadId`	string	Thread ID the reply was added to (same as input `threadId`)
`labelIds`	string[]	Labels applied to the reply (e.g. `["SENT"]`)
`status`	string	`success`
`errorCode`	string	Empty on success

Error Port

On failure, routes to the error port with status: "error", errorCode, and errorMessage.

Sample Output

{
  "messageId": "18e4d5e6f7a8b9c0",
  "threadId": "18e4a2f9d3c0b1a7",
  "labelIds": ["SENT"],
  "status": "success",
  "errorCode": ""
}

Expression Reference

Expression	Resolves To	Example Use
`{{support.gmailThreadId}}`	Thread ID from support system event	`threadId` field
`{{aiAgent.generatedReplyHtml}}`	AI-generated reply HTML from upstream node	`message` body
`{{resolution.summary}}`	Resolution text from workflow processing	Reply body content
`{{approval.outcome}}`	Approval decision text (Approved/Rejected)	Outcome notification in reply
`{{$now \| dateFormat:'YYYY-MM-DD HH:mm'}}`	Current timestamp	Timestamp in reply body

Node Policies & GuardRails

Policy	Rule
Reply-All Risk	Default `replyToSenderOnly: false` is Reply-All — set `replyToSenderOnly: true` for automated workflows to prevent unintended broadcast replies to all participants
Credential Storage	Store OAuth credentials in BizFirst Credentials Manager — never hardcode tokens in workflow configuration
Daily Send Limit	Personal Gmail: 500 messages/day; Workspace: 2,000/day — throttle high-volume thread reply workflows
PII Protection	Do not log reply body content in workflow execution history — replies may contain sensitive customer information
Quota Management	Thread reply costs 100 quota units per send — same as message/send — monitor usage against daily limits
Test Isolation	Test thread reply workflows against a dedicated Gmail test account to prevent accidental replies to real customers

Examples

Example 1: AI-Generated Support Reply

After fetching the thread and generating a response with an AI node, post the reply to the conversation.

{
  "nodeType": "Gmail",
  "operation": "thread/reply",
  "credentialId": "a3f9d12b-44e1-4c89-b7d2-9f0a1e2b3c4d",
  "threadId": "{{thread.threadId}}",
  "message": "{{aiAgent.replyHtml}}",
  "emailType": "html",
  "senderName": "BizFirst Support",
  "replyToSenderOnly": true
}

Example 2: Approval Outcome Notification

After a HIL approval node processes a request, reply to the original email thread with the approval decision.

{
  "nodeType": "Gmail",
  "operation": "thread/reply",
  "credentialId": "a3f9d12b-44e1-4c89-b7d2-9f0a1e2b3c4d",
  "threadId": "{{approvalRequest.threadId}}",
  "message": "<p>Dear {{requester.name}},</p><p>Your request has been <strong>{{approval.decision}}</strong>.</p><p>{{approval.notes}}</p>",
  "emailType": "html",
  "replyToSenderOnly": true
}

Example 3: CRM Follow-Up Thread Reply

A scheduled CRM workflow fires when a lead has been idle 7 days — reply to the existing email thread with a follow-up.

{
  "nodeType": "Gmail",
  "operation": "thread/reply",
  "credentialId": "a3f9d12b-44e1-4c89-b7d2-9f0a1e2b3c4d",
  "threadId": "{{crm.lead.lastEmailThreadId}}",
  "message": "<p>Hi {{crm.lead.firstName}},</p><p>Just following up on our previous conversation. Are you still interested in learning more about BizFirst? I'd love to schedule a quick call.</p>",
  "emailType": "html",
  "senderName": "{{crm.assignedRep.name}}",
  "replyToSenderOnly": true
}