diff --git a/frontend/taskdeck-web/src/composables/useProposalRevisions.ts b/frontend/taskdeck-web/src/composables/useProposalRevisions.ts
index 055af8cb1..1e3448df7 100644
--- a/frontend/taskdeck-web/src/composables/useProposalRevisions.ts
+++ b/frontend/taskdeck-web/src/composables/useProposalRevisions.ts
@@ -14,12 +14,27 @@ import {
 
 export type SaveRevisionResult = {
   proposalId: string
-  /** Whether the API response confirmed persistence or left it unknown. */
-  outcome: 'persisted' | 'indeterminate'
+  /** Whether the API response confirmed persistence, rejection, or left it unknown. */
+  outcome: 'persisted' | 'rejected' | 'indeterminate'
   /** The active proposal/save generation still owns this continuation. */
   current: boolean
 }
 
+/**
+ * These statuses are emitted before the revision write can commit. Other
+ * statuses remain indeterminate because the server may have committed before
+ * the client received an error (notably 404/409 from a concurrent or deleted
+ * proposal, and 5xx responses after the write path was reached).
+ */
+function isDefiniteRevisionSaveRejection(error: unknown): boolean {
+  if (typeof error !== 'object' || error === null) return false
+  const status = (error as { response?: { status?: unknown } }).response?.status
+  return (
+    typeof status === 'number' &&
+    [400, 401, 403, 413, 422, 429].includes(status)
+  )
+}
+
 export function useProposalRevisions(
   activeProposal: Ref<ApiProposal | null>,
   /**
@@ -194,6 +209,15 @@ export function useProposalRevisions(
       return { proposalId, outcome: 'persisted', current: true }
     } catch (e: unknown) {
       const current = gen === saveGeneration && activeProposal.value?.id === proposalId
+      if (isDefiniteRevisionSaveRejection(e)) {
+        // The API rejected this request before reporting persistence. Keep the
+        // authoritative metadata and retryable draft intact; unlike an
+        // indeterminate response, no queue read can have become stale.
+        if (current) {
+          toast.error(getErrorDisplay(e, 'Failed to save revision').message)
+        }
+        return { proposalId, outcome: 'rejected', current }
+      }
       // A rejected POST can have committed before a timeout, network break, or
       // 5xx reached the client. Invalidate queue reads synchronously even for a
       // stale continuation: a pre-write answer can restore old operations after
diff --git a/frontend/taskdeck-web/src/tests/composables/useProposalRevisions.spec.ts b/frontend/taskdeck-web/src/tests/composables/useProposalRevisions.spec.ts
index 0bb04ef50..fda559428 100644
--- a/frontend/taskdeck-web/src/tests/composables/useProposalRevisions.spec.ts
+++ b/frontend/taskdeck-web/src/tests/composables/useProposalRevisions.spec.ts
@@ -166,6 +166,84 @@ describe('useProposalRevisions', () => {
     expect(revisionsLoaded.value).toBe(false)
   })
 
+  it('preserves known revision metadata for a definite 4xx rejection', async () => {
+    const knownRevision = makeRevision({
+      revisedPayload: '{"title":"Existing revision"}',
+    })
+    vi.mocked(proposalRevisionsApi.getRevisions).mockResolvedValueOnce([knownRevision])
+    vi.mocked(proposalRevisionsApi.createRevision).mockRejectedValueOnce({
+      response: {
+        status: 400,
+        data: {
+          errorCode: 'ValidationError',
+          message: 'Revision payload is invalid',
+        },
+      },
+    })
+    const onRevisionSaved = vi.fn()
+    const onRevisionStateUncertain = vi.fn()
+    const proposal = ref<ApiProposal | null>(makeProposal())
+    const {
+      editing,
+      revisionCount,
+      latestRevision,
+      revisionsLoaded,
+      startEditing,
+      saveRevision,
+    } = useProposalRevisions(proposal, { onRevisionSaved, onRevisionStateUncertain })
+
+    await vi.waitFor(() => expect(revisionsLoaded.value).toBe(true))
+    startEditing()
+
+    await expect(
+      saveRevision({ revisedPayload: '{"title":"Invalid"}', reason: 'Try invalid payload' }),
+    ).resolves.toEqual({ proposalId: 'p-1', outcome: 'rejected', current: true })
+
+    expect(onRevisionSaved).not.toHaveBeenCalled()
+    expect(onRevisionStateUncertain).not.toHaveBeenCalled()
+    expect(editing.value).toBe(true)
+    expect(revisionCount.value).toBe(1)
+    expect(latestRevision.value).toEqual(knownRevision)
+    expect(revisionsLoaded.value).toBe(true)
+    expect(toastMocks.error).toHaveBeenCalledWith('Revision payload is invalid')
+  })
+
+  it.each([404, 409, 500])(
+    'treats HTTP %s as indeterminate because revision persistence is unknown',
+    async (status) => {
+      const knownRevision = makeRevision()
+      vi.mocked(proposalRevisionsApi.getRevisions).mockResolvedValueOnce([knownRevision])
+      vi.mocked(proposalRevisionsApi.createRevision).mockRejectedValueOnce({
+        response: { status },
+      })
+      const onRevisionSaved = vi.fn()
+      const onRevisionStateUncertain = vi.fn()
+      const proposal = ref<ApiProposal | null>(makeProposal())
+      const {
+        editing,
+        revisionCount,
+        latestRevision,
+        revisionsLoaded,
+        startEditing,
+        saveRevision,
+      } = useProposalRevisions(proposal, { onRevisionSaved, onRevisionStateUncertain })
+
+      await vi.waitFor(() => expect(revisionsLoaded.value).toBe(true))
+      startEditing()
+
+      await expect(
+        saveRevision({ revisedPayload: '{"title":"Uncertain"}', reason: 'Check boundary' }),
+      ).resolves.toEqual({ proposalId: 'p-1', outcome: 'indeterminate', current: true })
+
+      expect(onRevisionSaved).not.toHaveBeenCalled()
+      expect(onRevisionStateUncertain).toHaveBeenCalledOnce()
+      expect(editing.value).toBe(true)
+      expect(revisionCount.value).toBe(0)
+      expect(latestRevision.value).toBeNull()
+      expect(revisionsLoaded.value).toBe(false)
+    },
+  )
+
   it('ignores a pre-save revision load that resolves after the save (no stale overwrite)', async () => {
     // Codex review: a getRevisions request in flight when a save lands must not
     // overwrite the save's state when it resolves with the pre-save (empty) list.
diff --git a/frontend/taskdeck-web/src/tests/views/paper/review/PaperReviewView.spec.ts b/frontend/taskdeck-web/src/tests/views/paper/review/PaperReviewView.spec.ts
index a37bc4eb1..293cd77bd 100644
--- a/frontend/taskdeck-web/src/tests/views/paper/review/PaperReviewView.spec.ts
+++ b/frontend/taskdeck-web/src/tests/views/paper/review/PaperReviewView.spec.ts
@@ -4590,6 +4590,64 @@ describe('PaperReviewView', () => {
       wrapper.unmount()
     })
 
+    it('keeps known revision metadata and the draft after a definite 4xx rejection', async () => {
+      const now = new Date().toISOString()
+      mocks.getRevisions.mockResolvedValueOnce([
+        {
+          id: 'rev-known-1',
+          proposalId: 'proposal-001',
+          revisionNumber: 1,
+          editorUserId: 'u-1',
+          revisedPayload: '{"headline":"Existing revision","notes":"Original notes"}',
+          revisedAt: now,
+          reason: 'First revision',
+          createdAt: now,
+        },
+      ])
+      mocks.createRevision.mockRejectedValueOnce({
+        response: {
+          status: 400,
+          data: {
+            errorCode: 'ValidationError',
+            message: 'Revision payload is invalid',
+          },
+        },
+      })
+      const wrapper = await mountView([makeProposal()], '/workspace/review', [], [], {
+        attachTo: true,
+      })
+      await vi.waitFor(() => expect(mocks.getRevisions).toHaveBeenCalledTimes(1))
+
+      const proposalFetchesBeforeSave = mocks.getProposals.mock.calls.length
+      await wrapper.get('[data-testid="decision-edit"]').trigger('click')
+      await flushPromises()
+      const editor = wrapper.get('[data-testid="revision-editor"]')
+      await editor.get('[data-testid="revision-field-headline"]').setValue('Reviewer headline')
+      await editor.get('[data-testid="revision-field-notes"]').setValue('Reviewer notes')
+      await editor.get('[data-testid="revision-reason"]').setValue('Second revision')
+      await editor.get('[data-testid="revision-save"]').trigger('click')
+      await flushPromises()
+
+      const stillOpen = wrapper.get('[data-testid="revision-editor"]')
+      expect(
+        (stillOpen.get('[data-testid="revision-field-headline"]').element as HTMLTextAreaElement).value,
+      ).toBe('Reviewer headline')
+      expect(
+        (stillOpen.get('[data-testid="revision-field-notes"]').element as HTMLTextAreaElement).value,
+      ).toBe('Reviewer notes')
+      expect(
+        (stillOpen.get('[data-testid="revision-reason"]').element as HTMLInputElement).value,
+      ).toBe('Second revision')
+      expect(wrapper.get('[data-testid="revision-badge"]').text()).toContain('1 revision')
+      expect(mocks.errorToast).toHaveBeenCalledWith('Revision payload is invalid')
+      expect(mocks.getProposals.mock.calls.length).toBe(proposalFetchesBeforeSave)
+      expect(
+        stillOpen.element.contains(document.activeElement),
+      ).toBe(true)
+
+      wrapper.unmount()
+    })
+
     it('does not let a stale A1 save clear a newer A2 editor seed', async () => {
       let resolveA1Save!: (value: unknown) => void
       mocks.createRevision.mockImplementationOnce(
@@ -4775,7 +4833,11 @@ describe('PaperReviewView', () => {
 
     it('consumes one Approve after an indeterminate save even when the revision key is unchanged', async () => {
       const original = makeProposal({ id: 'uncertain-truth' })
-      mocks.createRevision.mockRejectedValueOnce(new Error('Request timed out after commit'))
+      // A 409 can be raised after a competing writer has committed the next
+      // revision. It must take the same refresh barrier as a timeout.
+      mocks.createRevision.mockRejectedValueOnce({
+        response: { status: 409 },
+      })
       mocks.approveProposal.mockResolvedValueOnce(
         makeProposal({ id: 'uncertain-truth', status: 'Approved' }),
       )
diff --git a/frontend/taskdeck-web/src/views/paper/PaperReviewView.vue b/frontend/taskdeck-web/src/views/paper/PaperReviewView.vue
index 9d4620e90..74051cbc7 100644
--- a/frontend/taskdeck-web/src/views/paper/PaperReviewView.vue
+++ b/frontend/taskdeck-web/src/views/paper/PaperReviewView.vue
@@ -1921,10 +1921,23 @@ async function onSaveRevision(payload: Parameters<typeof saveRevision>[0]) {
   const saveEpoch = revisionEditEpoch
   const saveResult = await saveRevision(payload)
   if (!saveResult) return
+  if (saveResult.outcome === 'rejected') {
+    // A definite 4xx cannot have committed, so the known revision metadata and
+    // any open preview remain authoritative. Keep the retryable draft visible
+    // and return focus inside the editor after the error toast.
+    if (
+      saveResult.current &&
+      proposalIdsEqual(activeProposal.value?.id, saveResult.proposalId) &&
+      revisionEditorPayloadEpoch === saveEpoch
+    ) {
+      retainRevisionEditorFocus()
+    }
+    return
+  }
   // A rejected response may still have committed, so both confirmed and
   // indeterminate saves require the same later read barrier. Record it before
-  // branching on the editor outcome, including for stale A continuations that
-  // finish while another proposal is active.
+  // branching on the indeterminate outcome, including for stale A continuations
+  // that finish while another proposal is active.
   requireRevisionReviewRefresh(saveResult.proposalId)
   if (saveResult.outcome === 'indeterminate') {
     // A rejected POST may still have committed. Clear only a preview of the