improvement(reply-gmail): added reply to gmail (#1809)

aadamgough · web-flow · commit b0fa3e8a26c1 · 2025-11-04T20:23:10.000-08:00
* added reply to thread/message

* cleanup, extract header helper for threaded replies

* more helpers
diff --git a/apps/sim/app/api/tools/gmail/draft/route.ts b/apps/sim/app/api/tools/gmail/draft/route.ts
@@ -5,7 +5,12 @@ import { createLogger } from '@/lib/logs/console/logger'
 import { processFilesToUserFiles } from '@/lib/uploads/utils/file-utils'
 import { downloadFileFromStorage } from '@/lib/uploads/utils/file-utils.server'
 import { generateRequestId } from '@/lib/utils'
-import { base64UrlEncode, buildMimeMessage } from '@/tools/gmail/utils'
+import {
+  base64UrlEncode,
+  buildMimeMessage,
+  buildSimpleEmailMessage,
+  fetchThreadingHeaders,
+} from '@/tools/gmail/utils'
 
 export const dynamic = 'force-dynamic'
 
@@ -16,8 +21,10 @@ const GMAIL_API_BASE = 'https://gmail.googleapis.com/gmail/v1/users/me'
 const GmailDraftSchema = z.object({
   accessToken: z.string().min(1, 'Access token is required'),
   to: z.string().min(1, 'Recipient email is required'),
-  subject: z.string().min(1, 'Subject is required'),
+  subject: z.string().optional().nullable(),
   body: z.string().min(1, 'Email body is required'),
+  threadId: z.string().optional().nullable(),
+  replyToMessageId: z.string().optional().nullable(),
   cc: z.string().optional().nullable(),
   bcc: z.string().optional().nullable(),
   attachments: z.array(z.any()).optional().nullable(),
@@ -49,11 +56,19 @@ export async function POST(request: NextRequest) {
 
     logger.info(`[${requestId}] Creating Gmail draft`, {
       to: validatedData.to,
-      subject: validatedData.subject,
+      subject: validatedData.subject || '',
       hasAttachments: !!(validatedData.attachments && validatedData.attachments.length > 0),
       attachmentCount: validatedData.attachments?.length || 0,
     })
 
+    const threadingHeaders = validatedData.replyToMessageId
+      ? await fetchThreadingHeaders(validatedData.replyToMessageId, validatedData.accessToken)
+      : {}
+
+    const originalMessageId = threadingHeaders.messageId
+    const originalReferences = threadingHeaders.references
+    const originalSubject = threadingHeaders.subject
+
     let rawMessage: string | undefined
 
     if (validatedData.attachments && validatedData.attachments.length > 0) {
@@ -106,8 +121,10 @@ export async function POST(request: NextRequest) {
           to: validatedData.to,
           cc: validatedData.cc ?? undefined,
           bcc: validatedData.bcc ?? undefined,
-          subject: validatedData.subject,
+          subject: validatedData.subject || originalSubject || '',
           body: validatedData.body,
+          inReplyTo: originalMessageId,
+          references: originalReferences,
           attachments: attachmentBuffers,
         })
 
@@ -117,22 +134,21 @@ export async function POST(request: NextRequest) {
     }
 
     if (!rawMessage) {
-      const emailHeaders = [
-        'Content-Type: text/plain; charset="UTF-8"',
-        'MIME-Version: 1.0',
-        `To: ${validatedData.to}`,
-      ]
-
-      if (validatedData.cc) {
-        emailHeaders.push(`Cc: ${validatedData.cc}`)
-      }
-      if (validatedData.bcc) {
-        emailHeaders.push(`Bcc: ${validatedData.bcc}`)
-      }
+      rawMessage = buildSimpleEmailMessage({
+        to: validatedData.to,
+        cc: validatedData.cc,
+        bcc: validatedData.bcc,
+        subject: validatedData.subject || originalSubject,
+        body: validatedData.body,
+        inReplyTo: originalMessageId,
+        references: originalReferences,
+      })
+    }
+
+    const draftMessage: { raw: string; threadId?: string } = { raw: rawMessage }
 
-      emailHeaders.push(`Subject: ${validatedData.subject}`, '', validatedData.body)
-      const email = emailHeaders.join('\n')
-      rawMessage = Buffer.from(email).toString('base64url')
+    if (validatedData.threadId) {
+      draftMessage.threadId = validatedData.threadId
     }
 
     const gmailResponse = await fetch(`${GMAIL_API_BASE}/drafts`, {
@@ -142,7 +158,7 @@ export async function POST(request: NextRequest) {
         'Content-Type': 'application/json',
       },
       body: JSON.stringify({
-        message: { raw: rawMessage },
+        message: draftMessage,
       }),
     })
 
diff --git a/apps/sim/app/api/tools/gmail/send/route.ts b/apps/sim/app/api/tools/gmail/send/route.ts
@@ -5,7 +5,12 @@ import { createLogger } from '@/lib/logs/console/logger'
 import { processFilesToUserFiles } from '@/lib/uploads/utils/file-utils'
 import { downloadFileFromStorage } from '@/lib/uploads/utils/file-utils.server'
 import { generateRequestId } from '@/lib/utils'
-import { base64UrlEncode, buildMimeMessage } from '@/tools/gmail/utils'
+import {
+  base64UrlEncode,
+  buildMimeMessage,
+  buildSimpleEmailMessage,
+  fetchThreadingHeaders,
+} from '@/tools/gmail/utils'
 
 export const dynamic = 'force-dynamic'
 
@@ -16,8 +21,10 @@ const GMAIL_API_BASE = 'https://gmail.googleapis.com/gmail/v1/users/me'
 const GmailSendSchema = z.object({
   accessToken: z.string().min(1, 'Access token is required'),
   to: z.string().min(1, 'Recipient email is required'),
-  subject: z.string().min(1, 'Subject is required'),
+  subject: z.string().optional().nullable(),
   body: z.string().min(1, 'Email body is required'),
+  threadId: z.string().optional().nullable(),
+  replyToMessageId: z.string().optional().nullable(),
   cc: z.string().optional().nullable(),
   bcc: z.string().optional().nullable(),
   attachments: z.array(z.any()).optional().nullable(),
@@ -49,11 +56,19 @@ export async function POST(request: NextRequest) {
 
     logger.info(`[${requestId}] Sending Gmail email`, {
       to: validatedData.to,
-      subject: validatedData.subject,
+      subject: validatedData.subject || '',
       hasAttachments: !!(validatedData.attachments && validatedData.attachments.length > 0),
       attachmentCount: validatedData.attachments?.length || 0,
     })
 
+    const threadingHeaders = validatedData.replyToMessageId
+      ? await fetchThreadingHeaders(validatedData.replyToMessageId, validatedData.accessToken)
+      : {}
+
+    const originalMessageId = threadingHeaders.messageId
+    const originalReferences = threadingHeaders.references
+    const originalSubject = threadingHeaders.subject
+
     let rawMessage: string | undefined
 
     if (validatedData.attachments && validatedData.attachments.length > 0) {
@@ -106,8 +121,10 @@ export async function POST(request: NextRequest) {
           to: validatedData.to,
           cc: validatedData.cc ?? undefined,
           bcc: validatedData.bcc ?? undefined,
-          subject: validatedData.subject,
+          subject: validatedData.subject || originalSubject || '',
           body: validatedData.body,
+          inReplyTo: originalMessageId,
+          references: originalReferences,
           attachments: attachmentBuffers,
         })
 
@@ -117,22 +134,21 @@ export async function POST(request: NextRequest) {
     }
 
     if (!rawMessage) {
-      const emailHeaders = [
-        'Content-Type: text/plain; charset="UTF-8"',
-        'MIME-Version: 1.0',
-        `To: ${validatedData.to}`,
-      ]
-
-      if (validatedData.cc) {
-        emailHeaders.push(`Cc: ${validatedData.cc}`)
-      }
-      if (validatedData.bcc) {
-        emailHeaders.push(`Bcc: ${validatedData.bcc}`)
-      }
+      rawMessage = buildSimpleEmailMessage({
+        to: validatedData.to,
+        cc: validatedData.cc,
+        bcc: validatedData.bcc,
+        subject: validatedData.subject || originalSubject,
+        body: validatedData.body,
+        inReplyTo: originalMessageId,
+        references: originalReferences,
+      })
+    }
+
+    const requestBody: { raw: string; threadId?: string } = { raw: rawMessage }
 
-      emailHeaders.push(`Subject: ${validatedData.subject}`, '', validatedData.body)
-      const email = emailHeaders.join('\n')
-      rawMessage = Buffer.from(email).toString('base64url')
+    if (validatedData.threadId) {
+      requestBody.threadId = validatedData.threadId
     }
 
     const gmailResponse = await fetch(`${GMAIL_API_BASE}/messages/send`, {
@@ -141,7 +157,7 @@ export async function POST(request: NextRequest) {
         Authorization: `Bearer ${validatedData.accessToken}`,
         'Content-Type': 'application/json',
       },
-      body: JSON.stringify({ raw: rawMessage }),
+      body: JSON.stringify(requestBody),
     })
 
     if (!gmailResponse.ok) {
diff --git a/apps/sim/blocks/blocks/gmail.ts b/apps/sim/blocks/blocks/gmail.ts
@@ -65,7 +65,7 @@ export const GmailBlock: BlockConfig<GmailToolResponse> = {
       layout: 'full',
       placeholder: 'Email subject',
       condition: { field: 'operation', value: ['send_gmail', 'draft_gmail'] },
-      required: true,
+      required: false,
     },
     {
       id: 'body',
@@ -101,6 +101,27 @@ export const GmailBlock: BlockConfig<GmailToolResponse> = {
       mode: 'advanced',
       required: false,
     },
+    // Advanced Settings - Threading
+    {
+      id: 'threadId',
+      title: 'Thread ID',
+      type: 'short-input',
+      layout: 'full',
+      placeholder: 'Thread ID to reply to (for threading)',
+      condition: { field: 'operation', value: ['send_gmail', 'draft_gmail'] },
+      mode: 'advanced',
+      required: false,
+    },
+    {
+      id: 'replyToMessageId',
+      title: 'Reply to Message ID',
+      type: 'short-input',
+      layout: 'full',
+      placeholder: 'Gmail message ID (not RFC Message-ID) - use the "id" field from results',
+      condition: { field: 'operation', value: ['send_gmail', 'draft_gmail'] },
+      mode: 'advanced',
+      required: false,
+    },
     // Advanced Settings - Additional Recipients
     {
       id: 'cc',
@@ -241,13 +262,18 @@ export const GmailBlock: BlockConfig<GmailToolResponse> = {
     to: { type: 'string', description: 'Recipient email address' },
     subject: { type: 'string', description: 'Email subject' },
     body: { type: 'string', description: 'Email content' },
+    threadId: { type: 'string', description: 'Thread ID to reply to (for threading)' },
+    replyToMessageId: {
+      type: 'string',
+      description: 'Gmail message ID to reply to (use "id" field from results, not "messageId")',
+    },
     cc: { type: 'string', description: 'CC recipients (comma-separated)' },
     bcc: { type: 'string', description: 'BCC recipients (comma-separated)' },
     attachments: { type: 'json', description: 'Files to attach (UserFile array)' },
     // Read operation inputs
     folder: { type: 'string', description: 'Gmail folder' },
     manualFolder: { type: 'string', description: 'Manual folder name' },
-    messageId: { type: 'string', description: 'Message identifier' },
+    readMessageId: { type: 'string', description: 'Message identifier for reading specific email' },
     unreadOnly: { type: 'boolean', description: 'Unread messages only' },
     includeAttachments: { type: 'boolean', description: 'Include email attachments' },
     // Search operation inputs
diff --git a/apps/sim/lib/webhooks/outlook-polling-service.ts b/apps/sim/lib/webhooks/outlook-polling-service.ts
@@ -368,7 +368,7 @@ async function processOutlookEmails(
           const simplifiedEmail: SimplifiedOutlookEmail = {
             id: email.id,
             conversationId: email.conversationId,
-            subject: email.subject || '(No Subject)',
+            subject: email.subject || '',
             from: email.from?.emailAddress?.address || '',
             to: email.toRecipients?.map((r) => r.emailAddress.address).join(', ') || '',
             cc: email.ccRecipients?.map((r) => r.emailAddress.address).join(', ') || '',
diff --git a/apps/sim/tools/gmail/draft.ts b/apps/sim/tools/gmail/draft.ts
@@ -28,7 +28,7 @@ export const gmailDraftTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
     },
     subject: {
       type: 'string',
-      required: true,
+      required: false,
       visibility: 'user-or-llm',
       description: 'Email subject',
     },
@@ -38,6 +38,19 @@ export const gmailDraftTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
       visibility: 'user-or-llm',
       description: 'Email body content',
     },
+    threadId: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description: 'Thread ID to reply to (for threading)',
+    },
+    replyToMessageId: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description:
+        'Gmail message ID to reply to - use the "id" field from Gmail Read results (not the RFC "messageId")',
+    },
     cc: {
       type: 'string',
       required: false,
@@ -69,6 +82,8 @@ export const gmailDraftTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
       to: params.to,
       subject: params.subject,
       body: params.body,
+      threadId: params.threadId,
+      replyToMessageId: params.replyToMessageId,
       cc: params.cc,
       bcc: params.bcc,
       attachments: params.attachments,
diff --git a/apps/sim/tools/gmail/read.ts b/apps/sim/tools/gmail/read.ts
@@ -225,6 +225,7 @@ export const gmailReadTool: ToolConfig<GmailReadParams, GmailToolResponse> = {
                   threadId: msg.threadId,
                   subject: msg.subject,
                   from: msg.from,
+                  to: msg.to,
                   date: msg.date,
                 })),
               },
diff --git a/apps/sim/tools/gmail/send.ts b/apps/sim/tools/gmail/send.ts
@@ -28,7 +28,7 @@ export const gmailSendTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
     },
     subject: {
       type: 'string',
-      required: true,
+      required: false,
       visibility: 'user-or-llm',
       description: 'Email subject',
     },
@@ -38,6 +38,19 @@ export const gmailSendTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
       visibility: 'user-or-llm',
       description: 'Email body content',
     },
+    threadId: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description: 'Thread ID to reply to (for threading)',
+    },
+    replyToMessageId: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description:
+        'Gmail message ID to reply to - use the "id" field from Gmail Read results (not the RFC "messageId")',
+    },
     cc: {
       type: 'string',
       required: false,
@@ -69,6 +82,8 @@ export const gmailSendTool: ToolConfig<GmailSendParams, GmailToolResponse> = {
       to: params.to,
       subject: params.subject,
       body: params.body,
+      threadId: params.threadId,
+      replyToMessageId: params.replyToMessageId,
       cc: params.cc,
       bcc: params.bcc,
       attachments: params.attachments,
diff --git a/apps/sim/tools/gmail/types.ts b/apps/sim/tools/gmail/types.ts
@@ -11,8 +11,10 @@ export interface GmailSendParams extends BaseGmailParams {
   to: string
   cc?: string
   bcc?: string
-  subject: string
+  subject?: string
   body: string
+  threadId?: string
+  replyToMessageId?: string
   attachments?: UserFile[]
 }
 
diff --git a/apps/sim/tools/gmail/utils.ts b/apps/sim/tools/gmail/utils.ts
