fix(desktop): keep the attachment-tolerance dedupe inside the identity gate (#122079)

The tolerant sameAttachmentTurn arm was an unparenthesised || operand, so a
rowId-bearing optimistic row could be swallowed by a committed row it provably
is not — pasting the same captioned screenshot twice dropped the second,
genuine turn. Gate both arms on !conflictingTranscriptIdentity, matching the
comment's invariant; the rowId-less paste keeps matching tolerantly.

apps/desktop/src/app/session/hooks/use-session-actions/utils.test.ts

@@ -2205,4 +2205,35 @@ describe('preserveLocalPendingTurnMessages attachment rewrites (#120978)', () =>
       'user-plain-repeat'
     ])
   })
+
+  it('never tolerance-matches a rowId-bearing optimistic row it provably is not (#122079)', () => {
+    // The submit receipt binds user_row_id onto the optimistic row while the
+    // stored page still ends at the earlier paste, so the row reaches the
+    // dedupe compare carrying a rowId none of the committed candidates hold.
+    // The tolerant arm must stay inside the identity gate: pasting the same
+    // captioned screenshot twice is a genuine new turn, not a duplicate.
+    const previous = [
+      msg('1-user', 'user', 'first'),
+      msg('2-assistant', 'assistant', 'first answer'),
+      msg('user-1790168309-ab12cd', 'user', 'unable to publish', {
+        rowId: 901,
+        attachmentRefs: ['data:image/png;base64,AAAA']
+      })
+    ]
+
+    const next = [
+      msg('1-user-stored', 'user', 'first', { rowId: 1 }),
+      msg('2-assistant-stored', 'assistant', 'first answer', { rowId: 2 }),
+      msg('3-user-stored', 'user', 'unable to publish\n\n[Image attached at: C:\\img\\shot.png]\n[screenshot]', {
+        rowId: 3
+      })
+    ]
+
+    expect(preserveLocalPendingTurnMessages(next, previous).map(message => message.id)).toEqual([
+      '1-user-stored',
+      '2-assistant-stored',
+      '3-user-stored',
+      'user-1790168309-ab12cd'
+    ])
+  })
 })

apps/desktop/src/app/session/hooks/use-session-actions/utils.ts

@@ -795,12 +795,14 @@ export function preserveLocalPendingTurnMessages(
   // unacknowledged repeat whose committed twin predates the acknowledged
   // boundary (and never enters this window) still survives.
   const newestAuthoritativeUser = [...remainingNext].reverse().find(message => message.role === 'user')
+
   const acknowledgedUserCandidates = remainingNext.filter(
     message =>
       message.role === 'user' &&
       !isGatewaySystemMarker(message) &&
       (message.rowId !== undefined || message === newestAuthoritativeUser)
   )
+
   const preserved: ChatMessage[] = []
   // Authoritative id → richer local pending row. Replacing (not appending)
   // avoids painting both the empty inflight shell and the full stream bubble.
@@ -886,9 +888,14 @@ export function preserveLocalPendingTurnMessages(
       isOptimisticUser &&
       acknowledgedUserCandidates.some(
         candidate =>
-          (!conflictingTranscriptIdentity(message, candidate) &&
-            textWithoutReferenceLines(chatMessageText(candidate)) === textWithoutReferenceLines(chatMessageText(message))) ||
-          sameAttachmentTurn(candidate, message)
+          // #122079: the tolerant arm widens the TEXT compare only — it stays
+          // inside the identity gate, so a rowId-bearing optimistic row is
+          // never swallowed by a committed row it provably is not (a genuine
+          // repeat of the same captioned paste). The rowId-less paste from
+          // #120978 carries no identity and keeps matching tolerantly.
+          !conflictingTranscriptIdentity(message, candidate) &&
+          (textWithoutReferenceLines(chatMessageText(candidate)) === textWithoutReferenceLines(chatMessageText(message)) ||
+            sameAttachmentTurn(candidate, message))
       )
     ) {
       continue