fix(collab-doc): derive streaming baseVersion as contentUpdatedAt ?? updatedAt

Match the version line the seed/persist use so a legacy file with no content
version still ships an ordered streaming snapshot instead of an unordered one.

Author: waleedlatif1

apps/sim/lib/copilot/request/go/file-preview-adapter.test.ts

@@ -162,6 +162,23 @@ describe('processFilePreviewStreamEvent — live-doc streaming merge', () => {
     expect(second[2]?.baseVersion).toBe(BASE_VERSION_MS)
   })
 
+  it('falls back to updatedAt for baseVersion when the file has no content version', async () => {
+    // A legacy file with no `contentUpdatedAt` — the base version must fall back to `updatedAt`, the SAME
+    // line the relay's synced version is on, so the snapshot is still ordered (not shipped unordered).
+    const UPDATED_AT_MS = 850_000
+    peekFileIntentMock.mockResolvedValue({
+      existingContent: 'Base.',
+      fileRecord: { contentUpdatedAt: null, updatedAt: new Date(UPDATED_AT_MS) },
+    })
+    const intent = makeIntent({ operation: 'append', fileId: 'file-legacy', fileName: 'notes.md' })
+
+    await drive(editContentDelta('{"content":"Hello'), intent)
+    await flushMicrotasks()
+
+    expect(mergeEditIntoLiveFileDocMock).toHaveBeenCalledTimes(1)
+    expect(mergeEditIntoLiveFileDocMock.mock.calls[0][2]?.baseVersion).toBe(UPDATED_AT_MS)
+  })
+
   it('throttles merges: two deltas within LIVE_DOC_MERGE_THROTTLE_MS yield one merge', async () => {
     const intent = makeIntent({
       operation: 'append',

apps/sim/lib/copilot/request/go/file-preview-adapter.ts

@@ -619,7 +619,11 @@ export async function processFilePreviewStreamEvent(input: {
             }
           )
           if (typeof intentBase?.existingContent === 'string') {
-            const baseVersion = intentBase.fileRecord?.contentUpdatedAt?.getTime()
+            // Same version line as the seed/persist (`contentUpdatedAt ?? updatedAt`), so the stream's
+            // base is comparable to the relay's synced version even when the file has no content version.
+            const baseVersion = (
+              intentBase.fileRecord?.contentUpdatedAt ?? intentBase.fileRecord?.updatedAt
+            )?.getTime()
             const seededSession: FilePreviewSession = {
               ...currentPreview.session,
               baseContent: intentBase.existingContent,

apps/sim/lib/copilot/tools/server/files/file-preview.ts

@@ -142,14 +142,15 @@ function buildAppendPreview(existingContent: string, incomingContent: string): s
  * full-file replacement until the intent landed.
  */
 /**
- * The base content a copilot edit is computed against, plus the durable version (`contentUpdatedAt`,
- * epoch ms) that content is at. The version is the stream's causal base: the relay drops a streaming
- * snapshot if a NEWER durable write landed than this, so a concurrent human edit is never clobbered.
- * `baseVersion` is undefined only for a legacy file with no recorded `contentUpdatedAt`.
+ * The base content a copilot edit is computed against, plus the durable version (epoch ms) that content
+ * is at. The version is the stream's causal base: the relay drops a streaming snapshot if a NEWER durable
+ * write landed than this, so a concurrent human edit is never clobbered. Derived as
+ * `contentUpdatedAt ?? updatedAt` — the SAME version line the seed/persist use — so it is directly
+ * comparable to the relay's recorded synced version.
  */
 export interface WorkspaceFilePreviewBase {
   text: string
-  baseVersion: number | undefined
+  baseVersion: number
 }
 
 export async function loadWorkspaceFileTextForPreview(
@@ -160,7 +161,10 @@ export async function loadWorkspaceFileTextForPreview(
     const record = await getWorkspaceFile(workspaceId, fileId)
     if (!record) return undefined
     const buffer = await fetchWorkspaceFileBuffer(record)
-    return { text: buffer.toString('utf-8'), baseVersion: record.contentUpdatedAt?.getTime() }
+    return {
+      text: buffer.toString('utf-8'),
+      baseVersion: (record.contentUpdatedAt ?? record.updatedAt).getTime(),
+    }
   } catch (error) {
     logger.warn('Failed to load workspace file text for preview', {
       workspaceId,