fix(desktop): preserve in-flight attachment replacements

apps/desktop/src/app/chat/session-tile-actions.ts

@@ -250,7 +250,7 @@ export function useSessionTileActions({ runtimeId, scope, storedSessionId }: Ses
     syncAttachmentsForSubmit,
     updateSessionState: (sessionId, updater) => sessionTileDelegate()!.updateSession(sessionId, updater),
     scope: {
-      clearAttachments: scope.attachments.clear,
+      removeAttachments: attachments => scope.attachments.removeOccurrences(attachments),
       readAttachments: () => scope.attachments.$attachments.get(),
       // Busy/messages flow through updateSession -> the tile's state slice;
       // the primary view atoms must never see a tile turn.

apps/desktop/src/app/chat/session-tile-attachments.test.tsx

@@ -206,4 +206,41 @@ describe('session tile attachment occurrence ownership', () => {
 
     expect(scope.attachments.$attachments.get()).toEqual([replacement])
   })
+
+  it('preserves a same-path replacement added while a successful tile submit is in flight', async () => {
+    const scope = createScope()
+    const original = makeAttachment()
+    const replacement = makeAttachment()
+    const attach = deferred<{ attached: boolean; path: string }>()
+
+    requestGateway.mockImplementation(async (method: string) => {
+      if (method === 'image.attach_bytes') {
+        return attach.promise
+      }
+
+      return {}
+    })
+
+    scope.attachments.add(original)
+
+    const { result } = renderHook(() =>
+      useSessionTileActions({ runtimeId: RUNTIME_ID, scope, storedSessionId: STORED_ID })
+    )
+
+    let submitted!: Promise<boolean>
+    act(() => {
+      submitted = result.current.submitText('describe this')
+    })
+
+    await waitFor(() => expect(requestGateway).toHaveBeenCalledWith('image.attach_bytes', expect.anything()))
+    scope.attachments.remove(original.id)
+    scope.attachments.add(replacement)
+    attach.resolve({ attached: true, path: STAGED_PATH })
+
+    await act(async () => {
+      await expect(submitted).resolves.toBe(true)
+    })
+
+    expect(scope.attachments.$attachments.get()).toEqual([replacement])
+  })
 })

apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx

@@ -2517,6 +2517,7 @@ describe('usePromptActions restoreToMessage', () => {
 describe('usePromptActions file attachment sync', () => {
   afterEach(() => {
     cleanup()
+    $composerAttachments.set([])
     $connection.set(null)
     $currentCwd.set('')
     vi.restoreAllMocks()
@@ -2725,6 +2726,68 @@ describe('usePromptActions file attachment sync', () => {
     })
   })
 
+  it('preserves a same-path replacement added while a successful main submit is in flight', async () => {
+    $connection.set({ mode: 'local' } as never)
+    $currentCwd.set('/root')
+
+    const hostPath = 'C:\\Users\\alice\\Pictures\\photo.jpg'
+
+    const original: ComposerAttachment = {
+      detail: hostPath,
+      id: 'image:photo.jpg',
+      kind: 'image',
+      label: 'photo.jpg',
+      occurrenceId: 'occurrence-original',
+      path: hostPath
+    }
+
+    const replacement: ComposerAttachment = {
+      ...original,
+      occurrenceId: 'occurrence-replacement'
+    }
+
+    let resolveAttach!: (value: { attached: boolean; path: string }) => void
+
+    const attachResult = new Promise<{ attached: boolean; path: string }>(resolve => {
+      resolveAttach = resolve
+    })
+
+    Object.defineProperty(window, 'hermesDesktop', {
+      configurable: true,
+      value: { readFileDataUrl: vi.fn(async () => 'data:image/jpeg;base64,aGVsbG8=') }
+    })
+
+    const requestGateway = vi.fn(async (method: string) => {
+      if (method === 'image.attach_bytes') {
+        return (await attachResult) as never
+      }
+
+      return {} as never
+    })
+
+    $composerAttachments.set([original])
+
+    let handle: HarnessHandle | null = null
+    await actRender(
+      <Harness onReady={h => (handle = h)} refreshSessions={async () => undefined} requestGateway={requestGateway} />
+    )
+
+    let submitted!: Promise<boolean>
+    act(() => {
+      submitted = handle!.submitTextRaw('describe this')
+    })
+
+    await waitFor(() => expect(requestGateway).toHaveBeenCalledWith('image.attach_bytes', expect.anything()))
+    $composerAttachments.set([replacement])
+    resolveAttach({ attached: true, path: '/root/tmp/photo.jpg' })
+
+    await act(async () => {
+      await expect(submitted).resolves.toBe(true)
+    })
+
+    expect($composerAttachments.get()).toEqual([replacement])
+  })
+
   it('uploads file bytes when the terminal backend is a container (docker)', async () => {
     // Container backends have their own filesystem: the host drop path would
     // dangle inside the sandbox, so the bytes must cross via file.attach's

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

@@ -14,8 +14,8 @@ import {
 } from '@/lib/voice-playback'
 import {
   $composerAttachments,
-  clearComposerAttachments,
   type ComposerAttachment,
+  mainComposerScope,
   terminalContextBlocksFromDraft
 } from '@/store/composer'
 import { $hudMode } from '@/store/hud'
@@ -77,7 +77,7 @@ interface SubmitPromptDeps {
    *  (defaults); a session tile injects its own so a tile submit never writes
    *  the primary view's $busy/$messages or clears the main attachment chips. */
   scope?: {
-    clearAttachments: () => void
+    removeAttachments: (attachments: readonly ComposerAttachment[]) => void
     readAttachments: () => ComposerAttachment[]
     setAwaitingResponse: (awaiting: boolean) => void
     setBusy: (busy: boolean) => void
@@ -88,7 +88,7 @@ interface SubmitPromptDeps {
 // Stable identity — a fresh default object per render would churn the
 // useCallback below on every render.
 const MAIN_SUBMIT_SCOPE: NonNullable<SubmitPromptDeps['scope']> = {
-  clearAttachments: clearComposerAttachments,
+  removeAttachments: attachments => mainComposerScope.removeOccurrences(attachments),
   readAttachments: () => $composerAttachments.get(),
   setAwaitingResponse,
   setBusy,
@@ -714,7 +714,10 @@ export function useSubmitPrompt(deps: SubmitPromptDeps) {
         }
 
         if (usingComposerAttachments) {
-          scope.clearAttachments()
+          // A submit owns only the occurrences captured before its first await.
+          // Preserve chips added or replaced while staging / prompt.submit was
+          // in flight instead of clearing the composer's newer draft state.
+          scope.removeAttachments(attachments)
         }
 
         // Submit landed — the turn now runs (busy stays true), but the submit

apps/desktop/src/store/composer.test.ts

@@ -137,6 +137,44 @@ describe('updateComposerAttachment', () => {
       thumbnailUrl: 'data:image/png;base64,current'
     })
   })
+
+  it('removes submitted occurrences while preserving unrelated attachments', () => {
+    const scope = createComposerAttachmentScope()
+
+    const submitted = attachment({
+      id: 'image:submitted',
+      kind: 'image',
+      occurrenceId: 'occurrence-submitted'
+    })
+
+    const other = attachment({ id: 'file:other', occurrenceId: 'occurrence-other' })
+
+    scope.add(submitted)
+    scope.add(other)
+    scope.removeOccurrences([submitted])
+
+    expect(scope.$attachments.get()).toEqual([other])
+  })
+
+  it('preserves a same-id replacement of a submitted occurrence', () => {
+    const scope = createComposerAttachmentScope()
+
+    const submitted = attachment({
+      id: 'image:submitted',
+      kind: 'image',
+      occurrenceId: 'occurrence-submitted'
+    })
+
+    const replacement = attachment({
+      ...submitted,
+      occurrenceId: 'occurrence-replacement'
+    })
+
+    scope.add(replacement)
+    scope.removeOccurrences([submitted])
+
+    expect(scope.$attachments.get()).toEqual([replacement])
+  })
 })
 
 describe('session drafts', () => {

apps/desktop/src/store/composer.ts

@@ -64,6 +64,7 @@ export interface ComposerAttachmentScope {
   add(attachment: ComposerAttachment): void
   clear(): void
   remove(id: string): ComposerAttachment | null
+  removeOccurrences(attachments: readonly ComposerAttachment[]): void
   setUploadState(id: string, uploadState?: ComposerAttachment['uploadState']): void
   update(attachment: ComposerAttachment): boolean
   updateIfCurrent(expected: ComposerAttachment, patch: ComposerAttachmentPatch): boolean
@@ -99,6 +100,20 @@ export function createComposerAttachmentScope($attachments = atom<ComposerAttach
 
       return removed
     },
+    removeOccurrences(attachments) {
+      const current = $attachments.get()
+
+      const submitted = new Set(attachments.map(attachment => `${attachment.id}\u0000${attachment.occurrenceId ?? ''}`))
+
+      const next = current.filter(
+        attachment => !submitted.has(`${attachment.id}\u0000${attachment.occurrenceId ?? ''}`)
+      )
+
+      // Preserve clear()'s notification semantics even when no captured
+      // occurrence remains. Some composer consumers settle local state on the
+      // successful-submit store emission.
+      $attachments.set(next)
+    },
     setUploadState(id, uploadState) {
       const current = $attachments.get()
       const index = current.findIndex(attachment => attachment.id === id)