fix(mothership): bound preview metadata frames and settle stopped rows on every save

- Compact every preview phase except content and completion, which the preview
  adapter already bounds; a model-written patch search string could otherwise
  exceed one replay write in an edit_meta frame
- Settle unfinished tool rows as stopped in buildPersistedAssistantMessage for a
  cancelled turn, so background and API callers that persist the result
  directly never save pending, executing, or awaiting-approval rows

Author: waleedlatif1

apps/sim/lib/mothership/chat/persisted-message.test.ts

@@ -802,3 +802,25 @@ describe('buildPersistedAssistantMessage on a completed turn', () => {
     }
   )
 })
+
+describe('buildPersistedAssistantMessage on a cancelled turn', () => {
+  it.each(['pending', 'executing', 'awaiting_approval'] as const)(
+    'settles a %s tool row as stopped for a caller that persists the result directly',
+    (status) => {
+      const persisted = buildPersistedAssistantMessage({
+        success: false,
+        cancelled: true,
+        content: 'Partial answer',
+        toolCalls: [],
+        contentBlocks: [
+          { type: 'tool_call', timestamp: 1, toolCall: { id: 'call-1', name: 'read', status } },
+        ],
+      })
+
+      expect(persisted.contentBlocks?.[0].toolCall).toMatchObject({
+        state: 'cancelled',
+        display: { title: 'Stopped by user' },
+      })
+    }
+  )
+})

apps/sim/lib/mothership/chat/persisted-message.ts

@@ -359,13 +359,18 @@ export function buildPersistedAssistantMessage(
     return normalized
   }
 
-  // A completed turn settles its stragglers as the live view did at `complete`.
-  if (result.success && message.contentBlocks) {
-    message.contentBlocks = settleUnfinishedToolCalls(message.contentBlocks, 'success')
+  // A finished turn settles its stragglers as the live view did at its terminal;
+  // background and API callers persist a stopped turn without withStoppedContentBlock.
+  if (message.contentBlocks) {
+    message.contentBlocks = result.success
+      ? settleUnfinishedToolCalls(message.contentBlocks, 'success')
+      : settleUnfinishedToolCalls(message.contentBlocks, 'cancelled', STOPPED_TOOL_DISPLAY)
   }
   return message
 }
 
+const STOPPED_TOOL_DISPLAY = { title: 'Stopped by user' } as const
+
 const UNSETTLED_TOOL_STATES: ReadonlySet<LocalToolCallStatus> = new Set<LocalToolCallStatus>([
   'pending',
   'executing',
@@ -392,9 +397,11 @@ function settleUnfinishedToolCalls(
 }
 
 export function withStoppedContentBlock(message: PersistedMessage): PersistedMessage {
-  const contentBlocks = settleUnfinishedToolCalls(message.contentBlocks ?? [], 'cancelled', {
-    title: 'Stopped by user',
-  })
+  const contentBlocks = settleUnfinishedToolCalls(
+    message.contentBlocks ?? [],
+    'cancelled',
+    STOPPED_TOOL_DISPLAY
+  )
   const hasAssistantText = contentBlocks.some(
     (block) =>
       block.type === MothershipStreamV1EventType.text &&

apps/sim/lib/mothership/request/session/replay-compaction.test.ts

@@ -147,7 +147,7 @@ describe('compactStreamEvent', () => {
     expect(args.stdin).toBe(`${'x'.repeat(STREAM_STRING_PREVIEW_UNITS)}…[truncated, 1 MB total]`)
   })
 
-  it('never compacts a file preview', () => {
+  it('never compacts preview content, which the client applies as exact deltas', () => {
     const preview: StreamEvent = {
       type: 'tool',
       payload: {
@@ -164,6 +164,27 @@ describe('compactStreamEvent', () => {
     expect(compactStreamEvent(preview)).toBe(preview)
   })
 
+  it('bounds a preview edit whose model-written search text is past one replay write', () => {
+    const meta: StreamEvent = {
+      type: 'tool',
+      payload: {
+        toolCallId: 'c',
+        toolName: 'prepare_file_edit',
+        previewPhase: 'file_preview_edit_meta',
+        edit: { strategy: 'search_replace', search: 's'.repeat(2 * MB), replaceAll: false },
+      },
+    }
+
+    const payload = payloadOf(compactStreamEvent(meta))
+    const edit = toRecord(payload.edit)
+
+    expect(serializedBytes(payload)).toBeLessThanOrEqual(STREAM_EVENT_MAX_PAYLOAD_BYTES)
+    expect(payload.previewPhase).toBe('file_preview_edit_meta')
+    expect(edit.strategy).toBe('search_replace')
+    expect(edit.replaceAll).toBe(false)
+    expect(edit.search).toBe(`${'s'.repeat(STREAM_STRING_PREVIEW_UNITS)}…[truncated, 2 MB total]`)
+  })
+
   it('compacts a copy and leaves the caller’s event whole for dispatch', () => {
     const stdout = 's'.repeat(MB)
     const event: StreamEvent = {

apps/sim/lib/mothership/request/session/replay-compaction.ts

@@ -225,14 +225,21 @@ function shed(
  * event for dispatch. Long strings are cut to their head in place, so every
  * object keeps its shape; if that is not enough, long arrays keep their head,
  * and past one replay write the smallest sufficient bulk is replaced by a size
- * note, keeping the fields beside it. Assistant text, file previews, and the
- * arguments of calls the browser executes are never cut; an event still too
- * large is refused by the buffer, which ends the turn with an error.
+ * note, keeping the fields beside it. Assistant text, the arguments of calls the
+ * browser executes, and preview content and completions are never cut: the
+ * client applies preview content as exact deltas, and the preview adapter
+ * bounds both itself. An event still too large is refused by the buffer, which
+ * ends the turn with an error.
  */
 export function compactStreamEvent(event: StreamEvent): StreamEvent {
   const payload = toRecordOrNull(event.payload)
   // Text length is part of the receipt the worker and a replacement check.
-  if (!payload || event.type === MothershipStreamV1EventType.text || 'previewPhase' in payload) {
+  if (
+    !payload ||
+    event.type === MothershipStreamV1EventType.text ||
+    payload.previewPhase === 'file_preview_content' ||
+    payload.previewPhase === 'file_preview_complete'
+  ) {
     return event
   }
   if (estimateBytes(payload) <= STREAM_EVENT_COMPACTION_THRESHOLD_BYTES) return event