From acc00df6a5010a971e7d920b45d52bf56020d2dd Mon Sep 17 00:00:00 2001
From: Siddharth Ganesan <siddharthganesan@gmail.com>
Date: Sat, 4 Apr 2026 12:31:23 -0700
Subject: [PATCH] feat(mothership): append

---
 .../api/files/serve/[...path]/route.test.ts   | 10 +++
 .../tools/server/files/workspace-file.ts      | 79 +++++++++++++++++++
 apps/sim/lib/copilot/tools/shared/schemas.ts  |  2 +-
 3 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/apps/sim/app/api/files/serve/[...path]/route.test.ts b/apps/sim/app/api/files/serve/[...path]/route.test.ts
index bc5b35647c..3c0c1fa7f6 100644
--- a/apps/sim/app/api/files/serve/[...path]/route.test.ts
+++ b/apps/sim/app/api/files/serve/[...path]/route.test.ts
@@ -75,6 +75,16 @@ vi.mock('@/lib/uploads/utils/file-utils', () => ({
 
 vi.mock('@/lib/uploads/setup.server', () => ({}))
 
+vi.mock('@/lib/execution/doc-vm', () => ({
+  generatePdfFromCode: vi.fn().mockResolvedValue(Buffer.from('%PDF-compiled')),
+  generateDocxFromCode: vi.fn().mockResolvedValue(Buffer.from('PK\x03\x04compiled')),
+  generatePptxFromCode: vi.fn().mockResolvedValue(Buffer.from('PK\x03\x04compiled')),
+}))
+
+vi.mock('@/lib/uploads/contexts/workspace/workspace-file-manager', () => ({
+  parseWorkspaceFileKey: vi.fn().mockReturnValue(undefined),
+}))
+
 vi.mock('@/app/api/files/utils', () => ({
   FileNotFoundError,
   createFileResponse: mockCreateFileResponse,
diff --git a/apps/sim/lib/copilot/tools/server/files/workspace-file.ts b/apps/sim/lib/copilot/tools/server/files/workspace-file.ts
index b258180cfe..94f4ec0a3a 100644
--- a/apps/sim/lib/copilot/tools/server/files/workspace-file.ts
+++ b/apps/sim/lib/copilot/tools/server/files/workspace-file.ts
@@ -301,6 +301,85 @@ export const workspaceFileServerTool: BaseServerTool<WorkspaceFileArgs, Workspac
           }
         }
 
+        case 'append': {
+          const fileId = (args as Record<string, unknown>).fileId as string | undefined
+          const content = (args as Record<string, unknown>).content as string | undefined
+
+          if (!fileId) {
+            return { success: false, message: 'fileId is required for append operation' }
+          }
+          if (!content) {
+            return { success: false, message: 'content is required for append operation' }
+          }
+
+          const fileRecord = await getWorkspaceFile(workspaceId, fileId)
+          if (!fileRecord) {
+            return { success: false, message: `File with ID "${fileId}" not found` }
+          }
+
+          const currentBuffer = await downloadWsFile(fileRecord)
+          const combined = `${currentBuffer.toString('utf-8')}\n${content}`
+
+          const appendLowerName = fileRecord.name?.toLowerCase() ?? ''
+          const isPptxAppend = appendLowerName.endsWith('.pptx')
+          const isDocxAppend = appendLowerName.endsWith('.docx')
+          const isPdfAppend = appendLowerName.endsWith('.pdf')
+          const isDocAppend = isPptxAppend || isDocxAppend || isPdfAppend
+
+          if (isDocAppend) {
+            const formatName = isPptxAppend ? 'PPTX' : isDocxAppend ? 'DOCX' : 'PDF'
+            const generator = isPptxAppend
+              ? generatePptxFromCode
+              : isDocxAppend
+                ? generateDocxFromCode
+                : generatePdfFromCode
+            try {
+              await generator(combined, workspaceId)
+            } catch (err) {
+              const msg = err instanceof Error ? err.message : String(err)
+              return {
+                success: false,
+                message: `Appended ${formatName} code failed to compile: ${msg}. Fix the content and retry.`,
+              }
+            }
+          }
+
+          const appendSourceMime = isPptxAppend
+            ? PPTX_SOURCE_MIME
+            : isDocxAppend
+              ? DOCX_SOURCE_MIME
+              : isPdfAppend
+                ? PDF_SOURCE_MIME
+                : undefined
+          const appendBuffer = Buffer.from(combined, 'utf-8')
+          assertServerToolNotAborted(context)
+          await updateWorkspaceFileContent(
+            workspaceId,
+            fileId,
+            context.userId,
+            appendBuffer,
+            appendSourceMime
+          )
+
+          logger.info('Workspace file appended via copilot', {
+            fileId,
+            name: fileRecord.name,
+            appendedSize: content.length,
+            totalSize: appendBuffer.length,
+            userId: context.userId,
+          })
+
+          return {
+            success: true,
+            message: `Content appended to "${fileRecord.name}" (${content.length} bytes added, ${appendBuffer.length} bytes total)`,
+            data: {
+              id: fileId,
+              name: fileRecord.name,
+              size: appendBuffer.length,
+            },
+          }
+        }
+
         case 'patch': {
           const fileId = (args as Record<string, unknown>).fileId as string | undefined
           const edits = (args as Record<string, unknown>).edits as
diff --git a/apps/sim/lib/copilot/tools/shared/schemas.ts b/apps/sim/lib/copilot/tools/shared/schemas.ts
index c59200e846..579a4b6b85 100644
--- a/apps/sim/lib/copilot/tools/shared/schemas.ts
+++ b/apps/sim/lib/copilot/tools/shared/schemas.ts
@@ -176,7 +176,7 @@ export type UserTableResult = z.infer<typeof UserTableResultSchema>
 
 // workspace_file - shared schema used by server tool and Go catalog
 export const WorkspaceFileArgsSchema = z.object({
-  operation: z.enum(['write', 'update', 'delete', 'rename', 'patch']),
+  operation: z.enum(['write', 'update', 'append', 'delete', 'rename', 'patch']),
   args: z
     .object({
       fileId: z.string().optional(),