diff --git a/apps/sim/app/workspace/[workspaceId]/files/[fileId]/view/file-viewer.tsx b/apps/sim/app/workspace/[workspaceId]/files/[fileId]/view/file-viewer.tsx
index a450bd374d..cbed424d13 100644
--- a/apps/sim/app/workspace/[workspaceId]/files/[fileId]/view/file-viewer.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/files/[fileId]/view/file-viewer.tsx
@@ -17,7 +17,7 @@ export function FileViewer() {
     return null
   }
 
-  const serveUrl = `/api/files/serve/${encodeURIComponent(file.key)}?context=workspace`
+  const serveUrl = `/api/files/serve/${encodeURIComponent(file.key)}?context=workspace&t=${file.size}`
 
   return (
     <div className='fixed inset-0 z-50 bg-[var(--bg)]'>
diff --git a/apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/file-viewer.tsx b/apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/file-viewer.tsx
index 6a90ebacbb..7c59dbbe83 100644
--- a/apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/file-viewer.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/file-viewer.tsx
@@ -502,7 +502,7 @@ const ZOOM_BUTTON_FACTOR = 1.2
 const clampZoom = (z: number) => Math.min(Math.max(z, ZOOM_MIN), ZOOM_MAX)
 
 const ImagePreview = memo(function ImagePreview({ file }: { file: WorkspaceFileRecord }) {
-  const serveUrl = `/api/files/serve/${encodeURIComponent(file.key)}?context=workspace`
+  const serveUrl = `/api/files/serve/${encodeURIComponent(file.key)}?context=workspace&t=${file.size}`
   const [zoom, setZoom] = useState(1)
   const [offset, setOffset] = useState({ x: 0, y: 0 })
   const isDragging = useRef(false)
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 94f4ec0a3a..afa3b3ff7a 100644
--- a/apps/sim/lib/copilot/tools/server/files/workspace-file.ts
+++ b/apps/sim/lib/copilot/tools/server/files/workspace-file.ts
@@ -15,6 +15,7 @@ import {
   deleteWorkspaceFile,
   downloadWorkspaceFile as downloadWsFile,
   getWorkspaceFile,
+  getWorkspaceFileByName,
   renameWorkspaceFile,
   updateWorkspaceFileContent,
   uploadWorkspaceFile,
@@ -99,20 +100,76 @@ export const workspaceFileServerTool: BaseServerTool<WorkspaceFileArgs, Workspac
           const isPptx = lowerName.endsWith('.pptx')
           const isDocx = lowerName.endsWith('.docx')
           const isPdf = lowerName.endsWith('.pdf')
-          let contentType: string
+          const isDoc = isPptx || isDocx || isPdf
+          const sourceMime = isPptx
+            ? PPTX_SOURCE_MIME
+            : isDocx
+              ? DOCX_SOURCE_MIME
+              : isPdf
+                ? PDF_SOURCE_MIME
+                : undefined
 
-          if (isPptx || isDocx || isPdf) {
+          const existingFile = await getWorkspaceFileByName(workspaceId, fileName)
+
+          if (existingFile) {
+            const currentBuffer = await downloadWsFile(existingFile)
+            const combined = `${currentBuffer.toString('utf-8')}\n${content}`
+
+            if (isDoc) {
+              const formatName = isPptx ? 'PPTX' : isDocx ? 'DOCX' : 'PDF'
+              const generator = isPptx
+                ? generatePptxFromCode
+                : isDocx
+                  ? generateDocxFromCode
+                  : generatePdfFromCode
+              try {
+                await generator(combined, workspaceId)
+              } catch (err) {
+                const msg = err instanceof Error ? err.message : String(err)
+                return {
+                  success: false,
+                  message: `${formatName} generation failed after append: ${msg}. Fix the content and retry.`,
+                }
+              }
+            }
+
+            const combinedBuffer = Buffer.from(combined, 'utf-8')
+            assertServerToolNotAborted(context)
+            await updateWorkspaceFileContent(
+              workspaceId,
+              existingFile.id,
+              context.userId,
+              combinedBuffer,
+              sourceMime
+            )
+
+            logger.info('Workspace file appended via write', {
+              fileId: existingFile.id,
+              name: fileName,
+              appendedSize: content.length,
+              totalSize: combinedBuffer.length,
+              userId: context.userId,
+            })
+
+            return {
+              success: true,
+              message: `Content appended to "${fileName}" (${content.length} bytes added, ${combinedBuffer.length} bytes total)`,
+              data: {
+                id: existingFile.id,
+                name: fileName,
+                size: combinedBuffer.length,
+              },
+            }
+          }
+
+          let contentType: string
+          if (isDoc) {
             const formatName = isPptx ? 'PPTX' : isDocx ? 'DOCX' : 'PDF'
             const generator = isPptx
               ? generatePptxFromCode
               : isDocx
                 ? generateDocxFromCode
                 : generatePdfFromCode
-            const sourceMime = isPptx
-              ? PPTX_SOURCE_MIME
-              : isDocx
-                ? DOCX_SOURCE_MIME
-                : PDF_SOURCE_MIME
             try {
               await generator(content, workspaceId)
             } catch (err) {
@@ -123,7 +180,7 @@ export const workspaceFileServerTool: BaseServerTool<WorkspaceFileArgs, Workspac
                 message: `${formatName} generation failed: ${msg}. Fix the code and retry.`,
               }
             }
-            contentType = sourceMime
+            contentType = sourceMime!
           } else {
             contentType = inferContentType(fileName, explicitType)
           }
@@ -301,85 +358,6 @@ 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 579a4b6b85..c59200e846 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', 'append', 'delete', 'rename', 'patch']),
+  operation: z.enum(['write', 'update', 'delete', 'rename', 'patch']),
   args: z
     .object({
       fileId: z.string().optional(),