fix(ui): defer exact Monaco paste admission

Author: waleedlatif1

apps/sim/app/_shell/paste-admission-guard.test.tsx

@@ -100,6 +100,19 @@ describe('PasteAdmissionGuard', () => {
     expect(dispatchPaste(editable, 'a').defaultPrevented).toBe(false)
   })
 
+  it('defers text admission to an editor that projects its exact paste result', () => {
+    const editor = document.createElement('div')
+    editor.setAttribute('contenteditable', 'true')
+    editor.dataset.pasteMaxBytes = '4'
+    editor.dataset.pasteProjectsTextResult = 'true'
+    host.appendChild(editor)
+
+    const targetHandler = vi.fn()
+    editor.addEventListener('paste', targetHandler)
+    expect(dispatchPaste(editor, '12345').defaultPrevented).toBe(false)
+    expect(targetHandler).toHaveBeenCalledOnce()
+  })
+
   it('lets a prompt consume a compact Sim selection reference before its large plain text', () => {
     const input = document.createElement('textarea')
     input.dataset.pasteMaxBytes = '4'

apps/sim/app/_shell/paste-admission-guard.tsx

@@ -49,20 +49,22 @@ export function PasteAdmissionGuard() {
       if (handlesImageFiles && clipboardHasImageFile(event.clipboardData)) return
 
       const text = event.clipboardData?.getData('text/plain') ?? ''
+      const projectsTextResult = event.target.closest('[data-paste-projects-text-result="true"]')
       const policyElement = event.target.closest('[data-paste-max-bytes]')
       const maxPastedBytes =
         finitePositiveAttribute(policyElement, 'data-paste-max-bytes') ?? PASTE_LIMITS.DEFAULT_BYTES
       const maxPastedCharacters = finitePositiveAttribute(
         policyElement,
         'data-paste-max-characters'
       )
-      const textAdmission = text
-        ? assessTextPaste({
-            pastedText: text,
-            maxPastedBytes,
-            maxPastedCharacters,
-          })
-        : null
+      const textAdmission =
+        text && !projectsTextResult
+          ? assessTextPaste({
+              pastedText: text,
+              maxPastedBytes,
+              maxPastedCharacters,
+            })
+          : null
       const htmlPolicyElement = event.target.closest('[data-paste-max-html-bytes]')
       const maxPastedHtmlBytes = finitePositiveAttribute(
         htmlPolicyElement,

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/text-editor-paste.test.ts

@@ -60,6 +60,26 @@ describe('assessTextEditorPaste', () => {
     ).toMatchObject({ accepted: true, resultBytes: 10 })
   })
 
+  it('admits a distributed result when only removed line separators exceed the boundary', () => {
+    expect(
+      assessTextEditorPaste(
+        {
+          pastedText: 'a\nb\nc\nd\ne\nf',
+          currentText: '1234',
+          selections: [
+            { start: 0, end: 0 },
+            { start: 1, end: 1 },
+            { start: 2, end: 2 },
+            { start: 3, end: 3 },
+            { start: 4, end: 4 },
+            { start: 4, end: 4 },
+          ],
+        },
+        10
+      )
+    ).toMatchObject({ accepted: true, resultBytes: 10 })
+  })
+
   it('projects the full clipboard at every cursor when Monaco spread mode is disabled', () => {
     expect(
       assessTextEditorPaste(

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/text-editor-paste.ts

@@ -90,7 +90,7 @@ export function assessTextEditorPaste(
     : input.pastedText.length * selections.length
   const resultCharacters = input.currentText.length - replacedCharacters + insertedCharacters
 
-  if (input.pastedText.length > maxBytes) {
+  if (!distributedRanges && input.pastedText.length > maxBytes) {
     return {
       accepted: false,
       reason: 'pasted-bytes',
@@ -103,8 +103,8 @@ export function assessTextEditorPaste(
     return { accepted: true, resultCharacters }
   }
 
-  const pastedBytes = utf8ByteLength(input.pastedText, maxBytes)
-  if (pastedBytes > maxBytes) {
+  const pastedBytes = distributedRanges ? undefined : utf8ByteLength(input.pastedText, maxBytes)
+  if (pastedBytes !== undefined && pastedBytes > maxBytes) {
     return { accepted: false, reason: 'pasted-bytes', actual: pastedBytes, limit: maxBytes }
   }
 
@@ -114,7 +114,7 @@ export function assessTextEditorPaste(
           total + utf8ByteLengthRange(input.pastedText, range.start, range.end, maxBytes - total),
         0
       )
-    : pastedBytes * selections.length
+    : (pastedBytes ?? 0) * selections.length
   if (insertedBytes > maxBytes) {
     return { accepted: false, reason: 'result-bytes', actual: insertedBytes, limit: maxBytes }
   }

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/text-editor.tsx

@@ -683,6 +683,7 @@ export const TextEditor = memo(function TextEditor({
       {showEditor && (
         <div
           data-paste-max-bytes={PASTE_LIMITS.TEXT_EDITOR_BYTES}
+          data-paste-projects-text-result='true'
           onPasteCapture={handleEditorPasteCapture}
           style={showPreviewPane ? { width: `${splitPct}%`, flexShrink: 0 } : undefined}
           className={cn(