diff --git a/frontend/src/components/job/JobActualTab.vue b/frontend/src/components/job/JobActualTab.vue
index 18878e805..4cd115560 100644
--- a/frontend/src/components/job/JobActualTab.vue
+++ b/frontend/src/components/job/JobActualTab.vue
@@ -81,6 +81,7 @@
               :jobId="jobId"
               :tabKind="'actual'"
               :lines="costLines"
+              :draftSession="costLineDraftSession"
               :readOnly="false"
               :showItemColumn="true"
               :showSourceColumn="true"
@@ -93,7 +94,6 @@
               @delete-line="handleSmartDelete"
               @duplicate-line="() => {}"
               @move-line="() => {}"
-              @create-line="handleCreateLine"
             />
           </div>
         </div>
@@ -454,6 +454,7 @@ import { costlineService } from '../../services/costline.service'
 import { schemas } from '../../api/generated/api'
 import { useSmartCostLineDelete } from '../../composables/useSmartCostLineDelete'
 import { useCostSummary } from '../../composables/useCostSummary'
+import { useCostLineDrafts } from '@/composables/useCostLineDrafts'
 import { useXeroConnection } from '../../composables/useXeroConnection'
 import { api } from '../../api/client'
 import { z } from 'zod'
@@ -860,47 +861,41 @@ async function consumeStockForNewLine(payload: {
   }
 }
 
-// Handler for table's @create-line (for adjustments, since material is handled in table)
-async function handleCreateLine(line: CostLine) {
-  if (line.kind === 'adjust') {
-    // For adjustments, create via service as in EstimateTab
-    isLoading.value = true
-    jobActualSaveFeedback.saving()
-    try {
-      const createPayload = {
-        kind: 'adjust' as const,
-        desc: line.desc,
-        quantity: line.quantity,
-        unit_cost: line.unit_cost,
-        unit_rev: line.unit_rev,
-        accounting_date: toLocalDateString(),
-        ext_refs: (line.ext_refs as Record<string, unknown>) || {},
-        meta: { source: 'manual_adjustment' },
-        created_at: new Date().toISOString(),
-        updated_at: new Date().toISOString(),
-      }
+// Adjustment persistence callback; material creation remains in consumeStockForNewLine.
+async function handleCreateLine(line: CostLine): Promise<CostLine> {
+  if (line.kind !== 'adjust') {
+    throw new Error(`Cannot persist ${line.kind} through the adjustment creation path.`)
+  }
 
-      const created = await costlineService.createCostLine(props.jobId, 'actual', createPayload)
-      // Replace if the source line exists in parent's array, otherwise append (phantom row case)
-      const idx = costLines.value.findIndex((l) => l === line || l.id === line.id)
-      if (idx >= 0) {
-        costLines.value[idx] = created
-      } else {
-        costLines.value.push(created)
-      }
-      jobActualSaveFeedback.saved()
-      emit('cost-line-changed')
-    } catch (error) {
-      jobActualSaveFeedback.error('Failed to create adjustment.')
-      toast.error('Failed to create adjustment.')
-      console.error('Failed to create adjustment:', error)
-    } finally {
-      isLoading.value = false
+  jobActualSaveFeedback.saving()
+  try {
+    const createPayload = {
+      kind: 'adjust' as const,
+      desc: line.desc,
+      quantity: line.quantity,
+      unit_cost: line.unit_cost,
+      unit_rev: line.unit_rev,
+      accounting_date: toLocalDateString(),
+      ext_refs: (line.ext_refs as Record<string, unknown>) || {},
+      meta: { source: 'manual_adjustment' },
+      created_at: new Date().toISOString(),
+      updated_at: new Date().toISOString(),
     }
+
+    const created = await costlineService.createCostLine(props.jobId, 'actual', createPayload)
+    jobActualSaveFeedback.saved()
+    emit('cost-line-changed')
+    return created
+  } catch (error) {
+    jobActualSaveFeedback.error('Failed to create adjustment.')
+    toast.error('Failed to create adjustment.')
+    console.error('Failed to create adjustment:', error)
+    throw error
   }
-  // For material, table already handled consumption, so no-op or reload
 }
 
+const costLineDraftSession = useCostLineDrafts({ costLines, createLine: handleCreateLine })
+
 onMounted(async () => {
   await Promise.all([loadStaff(), loadActualCosts(), loadCostsSummary(), loadInvoices()])
 })
diff --git a/frontend/src/components/job/JobEstimateTab.vue b/frontend/src/components/job/JobEstimateTab.vue
index 190f3b01e..66585dc8d 100644
--- a/frontend/src/components/job/JobEstimateTab.vue
+++ b/frontend/src/components/job/JobEstimateTab.vue
@@ -39,13 +39,13 @@
             :jobId="jobId"
             :tabKind="'estimate'"
             :lines="costLines"
+            :draftSession="costLineDraftSession"
             :readOnly="false"
             :showItemColumn="true"
             :showSourceColumn="false"
             @delete-line="handleSmartDelete"
             @duplicate-line="(line) => handleAddMaterial(line as any)"
             @move-line="(index, direction) => {}"
-            @create-line="handleCreateFromEmpty"
           />
         </div>
       </main>
@@ -103,6 +103,7 @@ import CompactSummaryCard from '../shared/CompactSummaryCard.vue'
 import { fetchCostSet } from '../../services/costing.service'
 import { useCostSummary } from '../../composables/useCostSummary'
 import { useCostLinesActions } from '../../composables/useCostLinesActions'
+import { useCostLineDrafts } from '@/composables/useCostLineDrafts'
 import { schemas } from '../../api/generated/api'
 import type { z } from 'zod'
 import {
@@ -212,11 +213,15 @@ async function handleAddMaterial(line: CostLine) {
 async function handleCreateFromEmpty(line: CostLine) {
   if (!isCompanyDefaultsReady.value) {
     toast.error('Company defaults not loaded yet.')
-    return
+    throw new Error('Company defaults not loaded yet.')
   }
 
-  await createFromEmptyInternal(line)
+  const created = await createFromEmptyInternal(line)
+  if (!created) throw new Error('Cost line creation was prevented.')
+  return created
 }
+
+const costLineDraftSession = useCostLineDrafts({ costLines, createLine: handleCreateFromEmpty })
 </script>
 
 <style scoped>
diff --git a/frontend/src/components/job/JobQuoteTab.vue b/frontend/src/components/job/JobQuoteTab.vue
index cefe9425e..2b6041e65 100644
--- a/frontend/src/components/job/JobQuoteTab.vue
+++ b/frontend/src/components/job/JobQuoteTab.vue
@@ -42,12 +42,12 @@
               :jobId="jobId"
               :tabKind="'quote'"
               :lines="costLines"
+              :draftSession="costLineDraftSession"
               :readOnly="isLoading || areEditsBlocked"
               :showItemColumn="true"
               :showSourceColumn="false"
               @delete-line="handleSmartDelete"
               @duplicate-line="(line) => handleAddMaterial(line as any)"
-              @create-line="handleCreateFromEmpty"
             />
             <div v-else class="text-center py-8 text-gray-500">No quote data available</div>
           </template>
@@ -503,6 +503,7 @@ import { z } from 'zod'
 import { costlineService } from '../../services/costline.service'
 import { fetchCostSet } from '../../services/costing.service'
 import { useCostLinesActions } from '../../composables/useCostLinesActions'
+import { useCostLineDrafts } from '@/composables/useCostLineDrafts'
 import { useXeroConnection } from '../../composables/useXeroConnection'
 import CompactSummaryCard from '../shared/CompactSummaryCard.vue'
 import {
@@ -586,6 +587,7 @@ const currentQuote = computed(() => {
 })
 
 const isLoading = ref(false)
+let quoteRefreshVersion = 0
 const showQuoteRevisionsModal = ref(false)
 const quoteRevisionsData = ref<QuoteRevisionsListResponse | null>(null)
 const isCreatingRevision = ref(false)
@@ -694,9 +696,10 @@ watch(
   { immediate: true },
 )
 
-async function refreshQuoteData() {
+async function refreshQuoteData(showLoading = true) {
   if (!props.jobId) return
-  isLoading.value = true
+  const refreshVersion = ++quoteRefreshVersion
+  if (showLoading) isLoading.value = true
 
   // DEBUG: Log before refresh
   debugLog('REFRESH QUOTE - BEFORE:')
@@ -705,6 +708,7 @@ async function refreshQuoteData() {
 
   try {
     const response = await fetchCostSet(props.jobId, 'quote')
+    if (refreshVersion !== quoteRefreshVersion) return
 
     // Update our local quote cost set
     quoteCostSet.value = response
@@ -720,17 +724,18 @@ async function refreshQuoteData() {
       const xeroQuoteResponse: Quote = await api.job_jobs_quote_retrieve({
         params: { job_id: props.jobId },
       })
-      xeroQuote.value = xeroQuoteResponse
+      if (refreshVersion === quoteRefreshVersion) xeroQuote.value = xeroQuoteResponse
     } catch {
       // Xero quote not available, that's ok
-      xeroQuote.value = null
+      if (refreshVersion === quoteRefreshVersion) xeroQuote.value = null
     }
   } catch (error) {
+    if (refreshVersion !== quoteRefreshVersion) return
     toast.error('Failed to refresh quote data')
     console.error('Failed to refresh quote data:', error)
     console.error('🔍 REFRESH QUOTE DEBUG - ERROR:', error)
   } finally {
-    isLoading.value = false
+    if (refreshVersion === quoteRefreshVersion) isLoading.value = false
   }
 }
 
@@ -797,10 +802,18 @@ const { handleAddMaterial, handleSmartDelete, handleCreateFromEmpty } = useCostL
   onCostLinesChanged: async () => {
     // Refresh quote data to update summary from API
     emit('cost-line-changed')
-    await refreshQuoteData()
+    await refreshQuoteData(false)
   },
 })
 
+async function persistNewLine(line: CostLine): Promise<CostLine> {
+  const created = await handleCreateFromEmpty(line)
+  if (!created) throw new Error('Cost line creation was prevented.')
+  return created
+}
+
+const costLineDraftSession = useCostLineDrafts({ costLines, createLine: persistNewLine })
+
 // --- QUOTE METHODS ---
 const createQuote = () => {
   // Show modal to ask user if they want breakdown or total
diff --git a/frontend/src/components/shared/SmartCostLinesTable.vue b/frontend/src/components/shared/SmartCostLinesTable.vue
index 3f5bb4b40..1136f9609 100644
--- a/frontend/src/components/shared/SmartCostLinesTable.vue
+++ b/frontend/src/components/shared/SmartCostLinesTable.vue
@@ -44,6 +44,11 @@ import { dataFreshness } from '../../composables/useDataFreshness'
 import { useCostLineCalculations } from '../../composables/useCostLineCalculations'
 import { useCostLineAutosave } from '../../composables/useCostLineAutosave'
 import { usePhantomRow } from '../../composables/usePhantomRow'
+import {
+  createCostLineDraftId,
+  type CostLineDraft,
+  type CostLineDraftSession,
+} from '@/composables/useCostLineDrafts'
 import {
   gridCellAttrs,
   handleGridCellKeydown,
@@ -104,6 +109,7 @@ const props = withDefaults(
     // Job ID for consumption context
     jobId?: string
     negativeStockIds?: string[]
+    draftSession: CostLineDraftSession
   }>(),
   {
     readOnly: false,
@@ -119,7 +125,6 @@ const emit = defineEmits<{
   'delete-line': [idOrIndex: string | number]
   'duplicate-line': [line: CostLine]
   'move-line': [index: number, direction: 'up' | 'down']
-  'create-line': [line: CostLine]
 }>()
 
 // Add logging to track emit calls
@@ -142,13 +147,14 @@ const selectedItemMap = new WeakMap<
   { id: string; description: string; item_code?: string } | null
 >()
 
-const createdOnce = new WeakSet<CostLine>()
-
 /**
  * Ensure there's always at least one empty line for editing
  */
-function makeEmptyLine(kind: KindOption = 'material'): CostLine {
+function makeEmptyLine(kind: KindOption = 'material'): CostLineDraft {
   return {
+    __localId: createCostLineDraftId(),
+    __status: 'idle',
+    __error: null,
     id: '',
     kind,
     desc: '',
@@ -169,32 +175,83 @@ function makeEmptyLine(kind: KindOption = 'material'): CostLine {
 const {
   phantomRow: emptyLine,
   displayRows: displayLines,
+  promotePhantom,
   resetPhantom,
   selectPhantom,
 } = usePhantomRow<CostLine>({
   rows: () => props.lines,
   makePhantom: makeEmptyLine,
+  extraRows: () => props.draftSession.drafts.value,
 })
 
 function selectEmptyLine(): void {
   selectPhantom((index) => (selectedRowIndex.value = index))
 }
 
-const negativeIdsSig = computed(() => props.negativeStockIds?.slice().sort().join('|') || '')
-
 function resetEmptyLine(kind: KindOption = 'material') {
   debugLog('resetEmptyLine called with kind:', kind)
   resetPhantom(makeEmptyLine(kind))
 }
 
-function maybeEmitCreate(line: CostLine) {
-  if (createdOnce.has(line)) return
-  createdOnce.add(line)
+function isDraft(line: CostLine): line is CostLineDraft {
+  return '__localId' in line
+}
+
+function isOwnedDraft(line: CostLine): line is CostLineDraft {
+  return (
+    isDraft(line) &&
+    props.draftSession.drafts.value.some((draft) => draft.__localId === line.__localId)
+  )
+}
+
+function isDraftLocked(line: CostLine): boolean {
+  return isOwnedDraft(line) && line.__status === 'saving'
+}
+
+function currentLine(line: CostLine): CostLine {
+  if (!isDraft(line)) return line
+  return props.draftSession.drafts.value.find((draft) => draft.__localId === line.__localId) ?? line
+}
+
+function focusLeftRow(event: FocusEvent, rowIndex: number): boolean {
+  const next = event.relatedTarget
+  if (!(next instanceof HTMLElement)) return true
+  if (next.getAttribute('data-grid-row') === String(rowIndex)) return false
+  return !next.closest(`[data-automation-id="DataTable-row-${rowIndex}"]`)
+}
+
+const deferredDraftBlurIds = new Set<string>()
+
+function persistReadyDraftOnRowExit(line: CostLine, event: FocusEvent, rowIndex: number): void {
+  if (isDraft(line) && deferredDraftBlurIds.delete(line.__localId)) return
+  if (!focusLeftRow(event, rowIndex)) return
+  const latest = currentLine(line)
+  if (!latest.id && isLineReadyForSave(latest)) maybePersistNewLine(latest)
+}
+
+function updateLine(line: CostLine, patch: Partial<CostLineDraft>): CostLine {
+  if (isOwnedDraft(line)) {
+    props.draftSession.updateDraft(line.__localId, patch)
+    const updated = props.draftSession.drafts.value.find(
+      (draft) => draft.__localId === line.__localId,
+    )
+    if (!updated) throw new Error(`Cost line draft not found after update: ${line.__localId}`)
+    transferUnitRevOverride(line, updated)
+    if (selectedItemMap.has(line)) selectedItemMap.set(updated, selectedItemMap.get(line) ?? null)
+    return updated
+  }
+  Object.assign(line, patch)
+  return line
+}
 
-  const payload = line
-  loggedEmit('create-line', payload)
+function maybePersistNewLine(line: CostLine): void {
+  if (props.tabKind === 'actual' && line.kind === 'material') {
+    if (line === emptyLine.value) resetEmptyLine()
+    return
+  }
 
-  if (line === emptyLine.value) resetEmptyLine()
+  const draft = isOwnedDraft(line) ? line : props.draftSession.addDraft(promotePhantom())
+  void props.draftSession.persistDraft(draft).catch(() => undefined)
 }
 
 function updateLineKind(line: CostLine, newKind: KindOption) {
@@ -207,7 +264,7 @@ function updateLineKind(line: CostLine, newKind: KindOption) {
     const wage = tryCompanyWageRate()
     if (wage === null) return
 
-    Object.assign(line, { kind: newKind })
+    const updatedLine = updateLine(line, { kind: newKind })
 
     // Time lines require a labour subtype; default to the workshop subtype.
     // unit_cost from company wage rate, unit_rev from the job's subtype rate.
@@ -217,18 +274,17 @@ function updateLineKind(line: CostLine, newKind: KindOption) {
     // silently disable time lines.
     const subtypeId =
       line.labour_subtype ?? workshopRateEntry(jobLabourRates.value)?.labour_subtype ?? null
-    Object.assign(line, {
+    updateLine(updatedLine, {
       labour_subtype: subtypeId,
       unit_cost: wage,
       unit_rev: rateForSubtype(jobLabourRates.value, subtypeId),
     })
   } else {
-    Object.assign(line, { kind: newKind })
-    Object.assign(line, { labour_subtype: null })
+    let updatedLine = updateLine(line, { kind: newKind, labour_subtype: null })
     if (line.unit_cost !== undefined && line.unit_cost !== null) {
       // Recalculate unit_rev with markup for material/adjust
-      const derived = apply(line).derived
-      Object.assign(line, { unit_rev: derived.unit_rev })
+      const derived = apply(updatedLine).derived
+      updatedLine = updateLine(updatedLine, { unit_rev: derived.unit_rev })
     } else {
       // Mid-entry row (e.g. phantom row where the user typed a description
       // first): no unit_cost yet, so unit_rev cannot be derived. It is
@@ -279,7 +335,7 @@ async function handleLabourPicked(line: CostLine, subtypeId: string) {
   const extRefs = { ...((line.ext_refs as Record<string, unknown>) || {}) }
   delete extRefs.stock_id
 
-  Object.assign(line, {
+  const updatedLine = updateLine(line, {
     kind: 'time' as const,
     labour_subtype: subtypeId,
     desc: nextLabourDesc(line.desc || '', rate, jobLabourRates.value),
@@ -288,10 +344,10 @@ async function handleLabourPicked(line: CostLine, subtypeId: string) {
     ext_refs: extRefs,
     quantity: line.quantity ?? 1,
   })
-  selectedItemMap.set(line, null)
+  selectedItemMap.set(updatedLine, null)
 
-  if (!line.id) {
-    maybeEmitCreate(line)
+  if (!updatedLine.id) {
+    maybePersistNewLine(updatedLine)
     return
   }
 
@@ -305,7 +361,7 @@ async function handleLabourPicked(line: CostLine, subtypeId: string) {
     ext_refs: extRefs,
   }
   const optimistic: Partial<CostLine> = { ...patch } as Partial<CostLine>
-  await autosave.saveNow(line, patch, optimistic)
+  await autosave.saveNow(updatedLine, patch, optimistic)
 }
 
 // Company Defaults and calculations
@@ -370,6 +426,7 @@ const {
   onUnitRevenueManuallyEdited,
   onItemSelected,
   resetUnitRevOverride,
+  transferUnitRevOverride,
 } = useCostLineCalculations({
   getCompanyDefaults: () => companyDefaultsStore.companyDefaults,
   getTimeChargeOutRate: (line) => rateForSubtype(jobLabourRates.value, line.labour_subtype),
@@ -582,6 +639,19 @@ const { onKeydown } = useGridKeyboardNav({
 })
 
 function handleCellNav(e: KeyboardEvent, rowIndex: number, columnId: string): boolean {
+  const line = displayLines.value[rowIndex]
+  if (e.key === 'Tab' && isOwnedDraft(line) && e.currentTarget instanceof HTMLElement) {
+    const cells = Array.from(
+      containerRef.value?.querySelectorAll<HTMLElement>(
+        '[data-grid-nav-cell="true"]:not([disabled]):not([aria-disabled="true"])',
+      ) ?? [],
+    )
+    const currentIndex = cells.indexOf(e.currentTarget)
+    const destination = cells[currentIndex + (e.shiftKey ? -1 : 1)]
+    if (destination?.dataset.gridRow === String(rowIndex)) {
+      deferredDraftBlurIds.add(line.__localId)
+    }
+  }
   return handleGridCellKeydown(e, {
     container: containerRef.value,
     rowIndex,
@@ -621,7 +691,6 @@ const shortcutsTitle = computed(
  * Build the column defs for DataTable
  */
 const columns = computed(() => {
-  void negativeIdsSig.value
   return [
     // Type / Kind - Now readonly badge only
     {
@@ -684,6 +753,7 @@ const columns = computed(() => {
             const enabled =
               !(isTime && isActualTab) &&
               !props.readOnly &&
+              !isDraftLocked(line) &&
               !lockedByDeliveryReceipt &&
               !lockedStockExisting
 
@@ -901,10 +971,10 @@ const columns = computed(() => {
                         found.unit_revenue === null || found.unit_revenue === undefined
                           ? null
                           : requiredNumber(found.unit_revenue, `unit_revenue for stock ${found.id}`)
-                      Object.assign(line, { desc: found.description || '' })
-                      Object.assign(line, { unit_cost: stockUnitCost })
+                      updateLine(line, { desc: found.description || '' })
+                      updateLine(line, { unit_cost: stockUnitCost })
                       // Update ext_refs.stock_id to reference the selected item
-                      Object.assign(line, {
+                      updateLine(line, {
                         ext_refs: { ...((line.ext_refs as object) || {}), stock_id: val },
                       })
                       // Update selectedItemMap with full data
@@ -919,25 +989,25 @@ const columns = computed(() => {
                         item_code: found.item_code || '',
                       })
                       // Ensure quantity is set for new lines
-                      if (line.quantity == null) Object.assign(line, { quantity: 1 })
+                      if (line.quantity == null) updateLine(line, { quantity: 1 })
                       if (kind !== 'time') {
                         if (stockUnitRevenue !== null) {
-                          Object.assign(line, { unit_rev: stockUnitRevenue })
-                          onUnitRevenueManuallyEdited(line)
+                          const updatedLine = updateLine(line, { unit_rev: stockUnitRevenue })
+                          onUnitRevenueManuallyEdited(updatedLine)
                         } else {
-                          Object.assign(line, { unit_rev: apply(line).derived.unit_rev })
+                          const updatedLine = updateLine(line, { unit_cost: stockUnitCost })
+                          updateLine(updatedLine, { unit_rev: apply(updatedLine).derived.unit_rev })
                         }
                       }
 
-                      // For phantom rows (no ID), emit create-line if ready after fetch
+                      // Persist phantom rows once item selection supplies a complete line.
                       if (!line.id && isLineReadyForSave(line)) {
-                        // Use guarded emitter so the phantom row resets and does not duplicate
-                        maybeEmitCreate(line)
+                        // Use guarded persistence so the phantom row resets and does not duplicate.
+                        maybePersistNewLine(line)
                       }
                     } else if (val) {
                       debugLog('Stock item not found in store for id:', val)
-                      Object.assign(line, { desc: '' })
-                      Object.assign(line, { unit_cost: 0 })
+                      updateLine(line, { desc: '', unit_cost: 0 })
                       selectedItemMap.set(line, null)
                     }
 
@@ -956,20 +1026,22 @@ const columns = computed(() => {
                   // Labour picks manage desc in handleLabourPicked (which can
                   // preserve user-authored text); this assign is stock-only.
                   'onUpdate:description': (desc: string) =>
-                    enabled && String(line.kind) !== 'time' && Object.assign(line, { desc }),
+                    enabled && String(line.kind) !== 'time' && updateLine(line, { desc }),
                   'onUpdate:unit_cost': (cost: number | null) => {
                     if (!enabled) return
                     if (cost === null) {
-                      Object.assign(line, { unit_cost: null })
+                      updateLine(line, { unit_cost: undefined })
                       return
                     }
-                    Object.assign(line, {
+                    updateLine(line, {
                       unit_cost: requiredNumber(cost, 'cost line unit_cost'),
                     })
                     if (kind !== 'time')
-                      Object.assign(line, { unit_rev: apply(line).derived.unit_rev })
+                      updateLine(line, {
+                        unit_rev: apply({ ...line, unit_cost: cost }).derived.unit_rev,
+                      })
                     nextTick(() => {
-                      if (!line.id && isLineReadyForSave(line)) maybeEmitCreate(line)
+                      if (!line.id && isLineReadyForSave(line)) maybePersistNewLine(line)
                     })
                   },
                   'onUpdate:kind': (newKind: string | null) => {
@@ -998,7 +1070,7 @@ const columns = computed(() => {
         const hasStockSelected = !!selectedItemMap.get(line)
         const isBlocked =
           isActualTab && isNewLine && kind === 'material' && isFieldBlocked && !hasStockSelected
-        const canEdit = canEditField(line, 'desc') && !isBlocked
+        const canEdit = canEditField(line, 'desc') && !isBlocked && !isDraftLocked(line)
 
         return h('div', { class: 'desc-cell w-full flex items-start gap-2' }, [
           h(Textarea, {
@@ -1025,7 +1097,8 @@ const columns = computed(() => {
             },
             'onUpdate:modelValue': (v: string | number) => {
               const val = typeof v === 'string' ? v : String(v)
-              Object.assign(line, { desc: val })
+              const isPhantom = line === emptyLine.value
+              updateLine(line, { desc: val })
               // Infer "adjust" when user starts typing without a selected item
               const hasSelectedItemLocal = !!selectedItemMap.get(line)
               const isLabour = line.kind === 'time'
@@ -1033,12 +1106,15 @@ const columns = computed(() => {
               if (!hasSelectedItemLocal && val.trim() && !isAdjust && !isLabour) {
                 updateLineKind(line, 'adjust')
               }
+              if (isPhantom && val.trim() && String(line.kind) === 'adjust') {
+                const promotedLine = promotePhantom()
+                props.draftSession.addDraft(promotedLine)
+              }
             },
-            onBlur: () => {
+            onBlur: (event: FocusEvent) => {
               if (!canEdit) return
-              // Create from phantom row if baseline is satisfied
-              if (!line.id && isLineReadyForSave(line)) {
-                maybeEmitCreate(line)
+              if (!line.id) {
+                persistReadyDraftOnRowExit(line, event, row.index)
                 return
               }
               // Save inline for existing lines
@@ -1083,7 +1159,7 @@ const columns = computed(() => {
               step: String(kind === 'time' ? 0.25 : 1),
               ...(kind === 'adjust' ? {} : { min: '0.0000001' }),
               modelValue: line.quantity,
-              disabled: !canEditField(line, 'quantity') || isBlocked,
+              disabled: !canEditField(line, 'quantity') || isBlocked || isDraftLocked(line),
               class: 'w-full text-right numeric-input',
               inputmode: 'decimal',
               'data-automation-id': `SmartCostLinesTable-quantity-${row.index}`,
@@ -1092,18 +1168,18 @@ const columns = computed(() => {
               onKeydown: (e: KeyboardEvent) => handleCellNav(e, row.index, 'quantity'),
               'onUpdate:modelValue': (val: string | number) => {
                 const num = Number(val)
-                if (!Number.isNaN(num)) Object.assign(line, { quantity: num })
+                if (!Number.isNaN(num)) updateLine(line, { quantity: num })
               },
-              onBlur: () => {
+              onBlur: (event: FocusEvent) => {
+                if (!line.id) {
+                  persistReadyDraftOnRowExit(line, event, row.index)
+                  return
+                }
                 const validation = validateLine(line)
                 if (!validation.isValid) {
                   toast.error(validation.issues[0]?.message || 'Invalid quantity')
                   return
                 }
-                if (!line.id && isLineReadyForSave(line)) {
-                  maybeEmitCreate(line)
-                  return
-                }
                 if (!line.id || !isLineReadyForSave(line)) return
                 const qtyNum = requiredNumber(line.quantity, 'cost line quantity')
                 const patch: PatchedCostLineCreateUpdate = { quantity: qtyNum }
@@ -1139,7 +1215,7 @@ const columns = computed(() => {
         const hasStockSelected = !!selectedItemMap.get(line)
         const isBlocked =
           isActualTab && isNewLine && kind === 'material' && isFieldBlocked && !hasStockSelected
-        const editable = canEditField(line, 'unit_cost') && !isBlocked
+        const editable = canEditField(line, 'unit_cost') && !isBlocked && !isDraftLocked(line)
         const isTime = kind === 'time'
         const resolved = canRenderDerivedValues(line) ? apply(line).derived : null
         return [
@@ -1161,28 +1237,26 @@ const columns = computed(() => {
               'onUpdate:modelValue': (val: string | number) => {
                 if (!editable) return
                 if (val === '') {
-                  Object.assign(line, { unit_cost: null })
+                  updateLine(line, { unit_cost: undefined })
                   return
                 } else {
                   const num = Number(val)
                   if (!Number.isNaN(num)) {
-                    Object.assign(line, { unit_cost: num })
-
                     // Auto-recalculate unit_rev for material/adjust unless overridden
                     if (kind !== 'time') {
-                      const derived = apply(line).derived
-                      Object.assign(line, { unit_rev: derived.unit_rev })
+                      const updatedLine = updateLine(line, { unit_cost: num })
+                      updateLine(updatedLine, { unit_rev: apply(updatedLine).derived.unit_rev })
+                    } else {
+                      updateLine(line, { unit_cost: num })
                     }
                   }
                 }
               },
-              onBlur: () => {
+              onBlur: (event: FocusEvent) => {
                 if (!editable) return
 
-                // Create new line if it doesn't have an ID yet and meets baseline criteria
-                if (!line.id && isLineReadyForSave(line)) {
-                  debugLog('Creating new line from unit_cost edit:', line)
-                  maybeEmitCreate(line)
+                if (!line.id) {
+                  persistReadyDraftOnRowExit(line, event, row.index)
                   return
                 }
 
@@ -1236,7 +1310,7 @@ const columns = computed(() => {
         const hasStockSelected = !!selectedItemMap.get(line)
         const isBlocked =
           isActualTab && isNewLine && kind === 'material' && isFieldBlocked && !hasStockSelected
-        const editable = canEditField(line, 'unit_rev') && !isBlocked
+        const editable = canEditField(line, 'unit_rev') && !isBlocked && !isDraftLocked(line)
         const isTime = kind === 'time'
         const resolved = canRenderDerivedValues(line) ? apply(line).derived : null
         return [
@@ -1257,35 +1331,23 @@ const columns = computed(() => {
               'onUpdate:modelValue': (val: string | number) => {
                 if (!editable) return
                 if (val === '') {
-                  Object.assign(line, { unit_rev: 0 })
+                  updateLine(line, { unit_rev: 0 })
                 } else {
                   const num = Number(val)
                   if (!Number.isNaN(num)) {
-                    Object.assign(line, { unit_rev: num })
+                    const updatedLine = updateLine(line, { unit_rev: num })
+                    onUnitRevenueManuallyEdited(updatedLine)
                   }
                 }
-                // Mark override when user types in unit_rev
-                onUnitRevenueManuallyEdited(line)
               },
               onKeydown: (e: KeyboardEvent) => {
-                if (handleCellNav(e, row.index, 'unit_rev')) return
-                if (
-                  (e.key === 'Tab' || e.key === 'Enter') &&
-                  row.index === displayLines.value.length - 1
-                ) {
-                  e.preventDefault()
-                  if (isLineReadyForSave(line)) {
-                    maybeEmitCreate(line)
-                  }
-                }
+                handleCellNav(e, row.index, 'unit_rev')
               },
-              onBlur: () => {
+              onBlur: (event: FocusEvent) => {
                 if (!editable) return
 
-                // Create new line if it doesn't have an ID yet and meets baseline criteria
-                if (!line.id && isLineReadyForSave(line)) {
-                  debugLog('Creating new line from unit_rev edit:', line)
-                  maybeEmitCreate(line)
+                if (!line.id) {
+                  persistReadyDraftOnRowExit(line, event, row.index)
                   return
                 }
 
@@ -1476,11 +1538,25 @@ const columns = computed(() => {
       cell: ({ row }: RowCtx) => {
         const line = displayLines.value[row.index]
         const approving = approvingId.value === line.id
-        const disabled = !!props.readOnly || approving
+        const disabled = !!props.readOnly || approving || isDraftLocked(line)
+        const draftStatus = isOwnedDraft(line) ? line.__status : undefined
+        const draftError = isOwnedDraft(line) ? line.__error : undefined
         const canApprove =
           props.tabKind === 'actual' && !props.readOnly && !!line.id && isUnapproved(line)
 
         return h('div', { class: 'flex items-center justify-center w-full gap-2' }, [
+          ...(draftStatus === 'error'
+            ? [
+                h(
+                  Badge,
+                  { variant: 'destructive', title: draftError ?? undefined },
+                  () => 'Save failed',
+                ),
+              ]
+            : []),
+          ...(draftStatus === 'saving'
+            ? [h(Badge, { variant: 'secondary' }, () => 'Saving…')]
+            : []),
           ...(canApprove
             ? [
                 h(
@@ -1545,6 +1621,11 @@ const columns = computed(() => {
 
                 // For local lines (no ID), delete immediately without confirmation
                 if (!line.id) {
+                  if (isDraft(line)) {
+                    autosave.cancel(line)
+                    props.draftSession.deleteDraft(line)
+                    return
+                  }
                   // Find the actual index in the original props.lines array
                   const actualIndex = props.lines.findIndex((l) => l === line)
                   debugLog('Looking for local line in props.lines:', {
diff --git a/frontend/src/components/shared/__tests__/SmartCostLinesTable.kindInference.test.ts b/frontend/src/components/shared/__tests__/SmartCostLinesTable.kindInference.test.ts
index 3dc016e5a..68c0fe095 100644
--- a/frontend/src/components/shared/__tests__/SmartCostLinesTable.kindInference.test.ts
+++ b/frontend/src/components/shared/__tests__/SmartCostLinesTable.kindInference.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest'
-import { mount } from '@vue/test-utils'
-import { defineComponent, h } from 'vue'
+import { flushPromises, mount } from '@vue/test-utils'
+import { defineComponent, h, ref } from 'vue'
 import type { z } from 'zod'
 import { schemas } from '@/api/generated/api'
 
@@ -49,8 +49,7 @@ vi.mock('@/services/costline.service', () => ({
 }))
 
 // Capture the rows the table passes to DataTable so tests can inspect the
-// phantom (empty) row, and render only the desc column for row 0 — the cell
-// whose typing handler infers kind 'adjust'.
+// phantom (empty) row, and render the fields used by these focused tests for row 0.
 const { capturedRows } = vi.hoisted(() => ({
   capturedRows: [] as unknown[],
 }))
@@ -70,8 +69,13 @@ vi.mock('@/components/DataTable.vue', () => ({
           id: string
           cell: (ctx: { row: { index: number } }) => unknown
         }>
-        const descColumn = columns.find((column) => column.id === 'desc')
-        return h('div', descColumn ? [descColumn.cell({ row: { index: 0 } })] : [])
+        const testedColumns = columns.filter((column) =>
+          ['desc', 'unit_cost', 'unit_rev'].includes(column.id),
+        )
+        return h(
+          'div',
+          testedColumns.map((column) => column.cell({ row: { index: 0 } })),
+        )
       }
     },
   }),
@@ -89,6 +93,7 @@ vi.mock('vue-sonner', () => ({
 }))
 
 import SmartCostLinesTable from '../SmartCostLinesTable.vue'
+import type { CostLineDraft } from '@/composables/useCostLineDrafts'
 
 type CostLine = z.infer<typeof schemas.CostLine> & {
   created_at?: string
@@ -112,7 +117,22 @@ const stubs = {
 
 function mountTable(lines: CostLine[], onError: (err: unknown) => void) {
   return mount(SmartCostLinesTable, {
-    props: { lines, tabKind: 'estimate' },
+    props: {
+      lines,
+      tabKind: 'estimate',
+      draftSession: {
+        drafts: ref<CostLineDraft[]>([]),
+        addDraft: (line) => ({
+          ...line,
+          __localId: 'test-draft',
+          __status: 'idle',
+          __error: null,
+        }),
+        updateDraft: (_localId, patch) => ({ ...lines[0], ...patch }) as CostLineDraft,
+        persistDraft: vi.fn(),
+        deleteDraft: vi.fn(),
+      },
+    },
     global: {
       config: { errorHandler: onError },
       stubs,
@@ -142,6 +162,139 @@ describe('SmartCostLinesTable kind inference from description typing', () => {
     expect(scheduleSaveMock).not.toHaveBeenCalled()
   })
 
+  it('promotes a typed adjustment, leaves a new phantom, and creates only when ready', async () => {
+    const draftLines = ref<CostLineDraft[]>([])
+    const persistDraft = vi.fn(async (draft: CostLineDraft) => {
+      draftLines.value = draftLines.value.filter(
+        (candidate) => candidate.__localId !== draft.__localId,
+      )
+      return { ...draft, id: 'created-line' }
+    })
+    const Host = defineComponent({
+      setup() {
+        return () =>
+          h(SmartCostLinesTable, {
+            lines: [],
+            tabKind: 'estimate',
+            draftSession: {
+              drafts: draftLines,
+              addDraft: (line: CostLine) => {
+                const draft = {
+                  ...line,
+                  __localId: '__localId' in line ? String(line.__localId) : 'test-draft',
+                  __status: 'idle' as const,
+                  __error: null,
+                }
+                draftLines.value = [...draftLines.value, draft]
+                return draft
+              },
+              updateDraft: (localId: string, patch: Partial<CostLineDraft>) => {
+                const current = draftLines.value.find((draft) => draft.__localId === localId)!
+                const updated = { ...current, ...patch }
+                draftLines.value = draftLines.value.map((draft) =>
+                  draft.__localId === localId ? updated : draft,
+                )
+                return updated
+              },
+              persistDraft,
+              deleteDraft: vi.fn(),
+            },
+          })
+      },
+    })
+    const wrapper = mount(Host, { attachTo: document.body, global: { stubs } })
+
+    await wrapper.get('textarea').setValue('Site adjustment')
+
+    expect(capturedRows).toHaveLength(2)
+    expect(capturedRows).toEqual([
+      expect.objectContaining({ desc: 'Site adjustment', kind: 'adjust' }),
+      expect.objectContaining({ desc: '' }),
+    ])
+    expect(persistDraft).not.toHaveBeenCalled()
+
+    const unitCost = wrapper.get('[data-automation-id="SmartCostLinesTable-unit-cost-0"]')
+    await unitCost.setValue('10')
+
+    // Grid Tab navigation calls blur() before its deferred focus, producing a null
+    // relatedTarget. That programmatic blur must not submit a ready draft while
+    // the destination is another cell in the same row.
+    const description = wrapper.get('textarea')
+    description.element.focus()
+    await description.trigger('keydown', { key: 'Tab' })
+    await new Promise((resolve) => window.setTimeout(resolve, 0))
+
+    expect(persistDraft).not.toHaveBeenCalled()
+    expect(document.activeElement).toBe(unitCost.element)
+
+    await unitCost.trigger('blur', { relatedTarget: null })
+    await flushPromises()
+
+    expect(persistDraft).toHaveBeenCalledOnce()
+    expect(persistDraft).toHaveBeenCalledWith(
+      expect.objectContaining({ desc: 'Site adjustment', kind: 'adjust', unit_cost: 10 }),
+    )
+    expect(capturedRows).toHaveLength(1)
+    wrapper.unmount()
+  })
+
+  it('keeps description focus and the stable row identity after the first character', async () => {
+    const draftLines = ref<CostLineDraft[]>([])
+    const Host = defineComponent({
+      setup() {
+        return () =>
+          h(SmartCostLinesTable, {
+            lines: [],
+            tabKind: 'estimate',
+            draftSession: {
+              drafts: draftLines,
+              addDraft: (line: CostLine) => {
+                const draft = {
+                  ...line,
+                  __localId: String((line as CostLineDraft).__localId),
+                  __status: 'idle' as const,
+                  __error: null,
+                }
+                draftLines.value = [draft]
+                return draft
+              },
+              updateDraft: (localId: string, patch: Partial<CostLineDraft>) => {
+                const updated = { ...draftLines.value[0], ...patch, __localId: localId }
+                draftLines.value = [updated]
+                return updated
+              },
+              persistDraft: vi.fn(),
+              deleteDraft: vi.fn(),
+            },
+          })
+      },
+    })
+    const wrapper = mount(Host, { attachTo: document.body, global: { stubs } })
+    const textarea = wrapper.get<HTMLTextAreaElement>('textarea')
+    textarea.element.focus()
+    const initialId = (capturedRows[0] as CostLineDraft).__localId
+
+    await textarea.setValue('S')
+    await wrapper.get('textarea').setValue('Site adjustment')
+
+    expect(document.activeElement).toBe(wrapper.get('textarea').element)
+    expect(wrapper.get<HTMLTextAreaElement>('textarea').element.value).toBe('Site adjustment')
+    expect((capturedRows[0] as CostLineDraft).__localId).toBe(initialId)
+
+    const unitCost = wrapper.get('[data-automation-id="SmartCostLinesTable-unit-cost-0"]')
+    const unitRevenue = wrapper.get('[data-automation-id="SmartCostLinesTable-unit-rev-0"]')
+    await unitCost.setValue('10')
+    await unitRevenue.setValue('77')
+    await wrapper.get('textarea').setValue('Updated adjustment')
+    await unitCost.setValue('20')
+
+    expect(
+      wrapper.get<HTMLInputElement>('[data-automation-id="SmartCostLinesTable-unit-rev-0"]').element
+        .value,
+    ).toBe('77')
+    wrapper.unmount()
+  })
+
   it('still derives unit_rev with markup when the converted line has a unit_cost', async () => {
     const line = {
       id: 'line-1',
diff --git a/frontend/src/components/shared/__tests__/SmartCostLinesTable.test.ts b/frontend/src/components/shared/__tests__/SmartCostLinesTable.test.ts
index ccbd53294..19e0d7c35 100644
--- a/frontend/src/components/shared/__tests__/SmartCostLinesTable.test.ts
+++ b/frontend/src/components/shared/__tests__/SmartCostLinesTable.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest'
 import { mount } from '@vue/test-utils'
-import { defineComponent, h } from 'vue'
+import { defineComponent, h, ref } from 'vue'
 import type { z } from 'zod'
 import { schemas } from '@/api/generated/api'
 
@@ -118,6 +118,13 @@ describe('SmartCostLinesTable draft inputs', () => {
       props: {
         lines: [line],
         tabKind: 'estimate',
+        draftSession: {
+          drafts: ref([]),
+          addDraft: vi.fn(),
+          updateDraft: vi.fn(),
+          persistDraft: vi.fn(),
+          deleteDraft: vi.fn(),
+        },
       },
       global: {
         stubs: {
@@ -148,6 +155,13 @@ describe('SmartCostLinesTable draft inputs', () => {
       props: {
         lines: [makeLine()],
         tabKind: 'estimate',
+        draftSession: {
+          drafts: ref([]),
+          addDraft: vi.fn(),
+          updateDraft: vi.fn(),
+          persistDraft: vi.fn(),
+          deleteDraft: vi.fn(),
+        },
       },
       global: {
         stubs: {
diff --git a/frontend/src/components/shared/__tests__/SmartCostLinesTable.timeGuard.test.ts b/frontend/src/components/shared/__tests__/SmartCostLinesTable.timeGuard.test.ts
index cfcc56660..751c3698a 100644
--- a/frontend/src/components/shared/__tests__/SmartCostLinesTable.timeGuard.test.ts
+++ b/frontend/src/components/shared/__tests__/SmartCostLinesTable.timeGuard.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest'
 import { mount } from '@vue/test-utils'
-import { defineComponent, h } from 'vue'
+import { defineComponent, h, ref } from 'vue'
 import type { z } from 'zod'
 import { schemas } from '@/api/generated/api'
 
@@ -167,7 +167,17 @@ describe('SmartCostLinesTable time-conversion guard before company defaults load
   it('aborts converting a line to time when wage_rate is unset, toasting instead of throwing', async () => {
     const line = makeLine()
     const wrapper = mount(SmartCostLinesTable, {
-      props: { lines: [line], tabKind: 'estimate' },
+      props: {
+        lines: [line],
+        tabKind: 'estimate',
+        draftSession: {
+          drafts: ref([]),
+          addDraft: vi.fn(),
+          updateDraft: vi.fn(),
+          persistDraft: vi.fn(),
+          deleteDraft: vi.fn(),
+        },
+      },
       global: { stubs },
     })
 
diff --git a/frontend/src/composables/__tests__/useCostLineDrafts.test.ts b/frontend/src/composables/__tests__/useCostLineDrafts.test.ts
new file mode 100644
index 000000000..17b9fd9ef
--- /dev/null
+++ b/frontend/src/composables/__tests__/useCostLineDrafts.test.ts
@@ -0,0 +1,93 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { ref } from 'vue'
+import type { z } from 'zod'
+import { schemas } from '@/api/generated/api'
+import { useCostLineDrafts } from '@/composables/useCostLineDrafts'
+
+type CostLine = z.infer<typeof schemas.CostLine>
+
+function line(desc: string): CostLine {
+  return {
+    id: '',
+    kind: 'adjust',
+    desc,
+    quantity: 1,
+    unit_cost: 10,
+    unit_rev: 12,
+    total_cost: 10,
+    total_rev: 12,
+    accounting_date: '2026-07-20',
+    ext_refs: {},
+    meta: {},
+    labour_subtype: null,
+  }
+}
+
+function deferred<T>() {
+  let resolve!: (value: T) => void
+  let reject!: (reason: unknown) => void
+  const promise = new Promise<T>((res, rej) => {
+    resolve = res
+    reject = rej
+  })
+  return { promise, resolve, reject }
+}
+
+describe('useCostLineDrafts', () => {
+  beforeEach(() => vi.clearAllMocks())
+
+  it('preserves a phantom local ID and completes drafts out of order', async () => {
+    const firstCreate = deferred<CostLine>()
+    const secondCreate = deferred<CostLine>()
+    const createLine = vi
+      .fn()
+      .mockReturnValueOnce(firstCreate.promise)
+      .mockReturnValueOnce(secondCreate.promise)
+    const costLines = ref<CostLine[]>([])
+    const controller = useCostLineDrafts({ costLines, createLine })
+    const first = controller.addDraft({ ...line('First'), __localId: 'phantom-first' } as CostLine)
+    const second = controller.addDraft(line('Second'))
+
+    expect(first.__localId).toBe('phantom-first')
+    expect(first.__localId).not.toBe(second.__localId)
+    const firstSave = controller.persistDraft(first)
+    const secondSave = controller.persistDraft(second)
+    secondCreate.resolve({ ...second, id: 'server-second' })
+    await secondSave
+    expect(controller.drafts.value.map((draft) => draft.__localId)).toEqual(['phantom-first'])
+    firstCreate.resolve({ ...first, id: 'server-first' })
+    await firstSave
+    expect(costLines.value.map((saved) => saved.id)).toEqual(['server-second', 'server-first'])
+  })
+
+  it('locks and deduplicates one POST, then unlocks a failed draft for retry', async () => {
+    const firstCreate = deferred<CostLine>()
+    const createLine = vi
+      .fn()
+      .mockReturnValueOnce(firstCreate.promise)
+      .mockResolvedValueOnce({ ...line('Retry'), id: 'server-retry' })
+    const controller = useCostLineDrafts({ costLines: ref([]), createLine })
+    const draft = controller.addDraft(line('Retry'))
+
+    const firstAttempt = controller.persistDraft(draft)
+    const duplicateAttempt = controller.persistDraft(draft)
+    expect(controller.drafts.value[0].__status).toBe('saving')
+    expect(controller.updateDraft(draft.__localId, { unit_rev: 99 }).unit_rev).toBe(12)
+    expect(createLine).toHaveBeenCalledOnce()
+    firstCreate.reject(new Error('POST failed'))
+    await expect(firstAttempt).rejects.toThrow('POST failed')
+    await expect(duplicateAttempt).rejects.toThrow('POST failed')
+    expect(controller.drafts.value[0].__status).toBe('error')
+
+    await controller.persistDraft(controller.drafts.value[0])
+    expect(createLine).toHaveBeenCalledTimes(2)
+    expect(controller.drafts.value).toEqual([])
+  })
+
+  it('deletes an unlocked local draft', () => {
+    const controller = useCostLineDrafts({ costLines: ref([]), createLine: vi.fn() })
+    const draft = controller.addDraft(line('Discard me'))
+    controller.deleteDraft(draft)
+    expect(controller.drafts.value).toEqual([])
+  })
+})
diff --git a/frontend/src/composables/useCostLineCalculations.ts b/frontend/src/composables/useCostLineCalculations.ts
index 9c91a6378..ac215a20e 100644
--- a/frontend/src/composables/useCostLineCalculations.ts
+++ b/frontend/src/composables/useCostLineCalculations.ts
@@ -114,6 +114,11 @@ export function useCostLineCalculations(options: {
     unitRevOverride.delete(line)
   }
 
+  function transferUnitRevOverride(from: CostLine, to: CostLine) {
+    if (unitRevOverride.has(from)) unitRevOverride.add(to)
+    else unitRevOverride.delete(to)
+  }
+
   /**
    * Format helpers (rounding with fixed decimals)
    */
@@ -297,6 +302,7 @@ export function useCostLineCalculations(options: {
     markUnitRevOverridden,
     isUnitRevOverridden,
     resetUnitRevOverride,
+    transferUnitRevOverride,
 
     // Calculations
     apply,
diff --git a/frontend/src/composables/useCostLineDrafts.ts b/frontend/src/composables/useCostLineDrafts.ts
new file mode 100644
index 000000000..73d46bee5
--- /dev/null
+++ b/frontend/src/composables/useCostLineDrafts.ts
@@ -0,0 +1,111 @@
+import { ref, type Ref } from 'vue'
+import type { z } from 'zod'
+import { schemas } from '@/api/generated/api'
+
+type CostLine = z.infer<typeof schemas.CostLine>
+
+export type CostLineDraftStatus = 'idle' | 'saving' | 'error'
+export type CostLineDraft = CostLine & {
+  __localId: string
+  __status: CostLineDraftStatus
+  __error: string | null
+}
+
+type Options = {
+  costLines: Ref<CostLine[]>
+  createLine: (draft: CostLineDraft) => Promise<CostLine>
+}
+
+let nextDraftId = 1
+
+export function createCostLineDraftId(): string {
+  return `cost-line-draft-${nextDraftId++}`
+}
+
+function withoutDraftState(line: CostLine): CostLine {
+  const {
+    __localId: _localId,
+    __status: _status,
+    __error: _error,
+    ...serverLine
+  } = line as CostLineDraft
+  void _localId
+  void _status
+  void _error
+  return serverLine as CostLine
+}
+
+export function useCostLineDrafts({ costLines, createLine }: Options) {
+  const drafts = ref<CostLineDraft[]>([])
+  const inFlight = new Map<string, Promise<CostLine>>()
+
+  function addDraft(line: CostLine): CostLineDraft {
+    const localId = '__localId' in line ? String(line.__localId) : createCostLineDraftId()
+    const draft = {
+      ...line,
+      __localId: localId,
+      __status: 'idle' as const,
+      __error: null,
+    }
+    drafts.value = [...drafts.value, draft]
+    return draft
+  }
+
+  function updateDraft(localId: string, patch: Partial<CostLineDraft>): CostLineDraft {
+    const existing = drafts.value.find((draft) => draft.__localId === localId)
+    if (!existing) throw new Error(`Cost line draft not found: ${localId}`)
+    if (existing.__status === 'saving') return existing
+    const updated = { ...existing, ...patch, __localId: localId }
+    drafts.value = drafts.value.map((draft) => (draft.__localId === localId ? updated : draft))
+    return updated
+  }
+
+  function setDraftState(
+    localId: string,
+    status: CostLineDraftStatus,
+    error: string | null = null,
+  ): CostLineDraft {
+    const existing = drafts.value.find((draft) => draft.__localId === localId)
+    if (!existing) throw new Error(`Cost line draft not found: ${localId}`)
+    const updated = { ...existing, __status: status, __error: error }
+    drafts.value = drafts.value.map((draft) => (draft.__localId === localId ? updated : draft))
+    return updated
+  }
+
+  function persistDraft(draft: CostLineDraft): Promise<CostLine> {
+    const localId = draft.__localId
+    const existingRequest = inFlight.get(localId)
+    if (existingRequest) return existingRequest
+
+    const submitted = setDraftState(localId, 'saving')
+    const request = createLine(submitted)
+      .then((created) => {
+        const serverLine = withoutDraftState(created)
+        const exists = costLines.value.some((line) => line.id === serverLine.id)
+        costLines.value = exists
+          ? costLines.value.map((line) => (line.id === serverLine.id ? serverLine : line))
+          : [...costLines.value, serverLine]
+        drafts.value = drafts.value.filter((candidate) => candidate.__localId !== localId)
+        return serverLine
+      })
+      .catch((error: unknown) => {
+        const message = error instanceof Error ? error.message : 'Failed to save cost line'
+        setDraftState(localId, 'error', message)
+        throw error
+      })
+      .finally(() => {
+        inFlight.delete(localId)
+      })
+    inFlight.set(localId, request)
+    return request
+  }
+
+  function deleteDraft(draft: CostLineDraft): void {
+    if (draft.__status === 'saving') return
+    drafts.value = drafts.value.filter((candidate) => candidate.__localId !== draft.__localId)
+  }
+
+  return { drafts, addDraft, updateDraft, persistDraft, deleteDraft }
+}
+
+export type CostLineDraftSession = ReturnType<typeof useCostLineDrafts>
diff --git a/frontend/src/composables/useCostLinesActions.ts b/frontend/src/composables/useCostLinesActions.ts
index 1edbb115a..36cad7f8b 100644
--- a/frontend/src/composables/useCostLinesActions.ts
+++ b/frontend/src/composables/useCostLinesActions.ts
@@ -42,7 +42,6 @@ export function useCostLinesActions(options: UseCostLinesActionsOptions) {
   })
 
   const { handleCreateFromEmpty } = useCreateCostLineFromEmpty({
-    costLines,
     jobId,
     costSetKind,
     onSuccess: async () => {
diff --git a/frontend/src/composables/useCreateCostLineFromEmpty.ts b/frontend/src/composables/useCreateCostLineFromEmpty.ts
index 28dbc6d0b..207947a8a 100644
--- a/frontend/src/composables/useCreateCostLineFromEmpty.ts
+++ b/frontend/src/composables/useCreateCostLineFromEmpty.ts
@@ -1,4 +1,3 @@
-import type { Ref } from 'vue'
 import { toast } from 'vue-sonner'
 import { costlineService } from '../services/costline.service'
 import { schemas } from '../api/generated/api'
@@ -18,7 +17,6 @@ type CostLineInput = Pick<
 >
 
 export interface UseCreateCostLineFromEmptyOptions {
-  costLines: Ref<CostLine[]>
   jobId: string
   costSetKind: CostSetKind
   onSuccess?: (created: CostLine) => void | Promise<void>
@@ -26,7 +24,7 @@ export interface UseCreateCostLineFromEmptyOptions {
 }
 
 export function useCreateCostLineFromEmpty(options: UseCreateCostLineFromEmptyOptions) {
-  const { costLines, jobId, costSetKind, onSuccess, beforeCreate } = options
+  const { jobId, costSetKind, onSuccess, beforeCreate } = options
   const jobsStore = useJobsStore()
   const saveFeedback = useSaveFeedback(`job-cost-line-create:${costSetKind}:${jobId}`, {
     toastErrors: false,
@@ -64,15 +62,6 @@ export function useCreateCostLineFromEmpty(options: UseCreateCostLineFromEmptyOp
 
       const created = await costlineService.createCostLine(jobId, costSetKind, createPayload)
 
-      // Insert created line into costLines; replace if the source line exists, otherwise push (phantom row case)
-      const index = costLines.value.findIndex((l) => l === line)
-      if (index !== -1) {
-        costLines.value[index] = created as CostLine
-      } else {
-        // When creating from the table's phantom row (not present in costLines), append it
-        costLines.value.push(created as CostLine)
-      }
-
       saveFeedback.saved()
       debugLog('Successfully created cost line:', created)
 
diff --git a/frontend/tests/job/create-estimate-entry.spec.ts b/frontend/tests/job/create-estimate-entry.spec.ts
index 2fe399822..158681a81 100644
--- a/frontend/tests/job/create-estimate-entry.spec.ts
+++ b/frontend/tests/job/create-estimate-entry.spec.ts
@@ -84,6 +84,7 @@ async function addAdjustmentEntry(
   const descInput = newRow.locator('textarea').first()
   const quantityInput = newRow.locator('[data-automation-id^="SmartCostLinesTable-quantity-"]')
   const unitCostInput = newRow.locator('[data-automation-id^="SmartCostLinesTable-unit-cost-"]')
+  const unitRevenueInput = newRow.locator('[data-automation-id^="SmartCostLinesTable-unit-rev-"]')
 
   await descInput.click()
   await descInput.fill(description)
@@ -95,10 +96,13 @@ async function addAdjustmentEntry(
   await expect(unitCostInput).toBeFocused()
 
   await unitCostInput.fill(unitCost)
+  await page.keyboard.press('Tab')
+  await expect(unitRevenueInput).toBeFocused()
+
   const savePromise = waitForAutosave(page)
   await page.keyboard.press('Tab')
-  // unit_cost onBlur fires maybeEmitCreate — catch the POST before calling
-  // waitForAutosave too late (as the original code did at the bottom).
+  // Creation happens only when focus leaves the complete row, so rapid edits
+  // to Unit Revenue cannot be overwritten by an earlier POST response.
   await savePromise
 }
 
diff --git a/frontend/tests/job/job-cost-entry-data.spec.ts b/frontend/tests/job/job-cost-entry-data.spec.ts
index 366a9401c..2ef634383 100644
--- a/frontend/tests/job/job-cost-entry-data.spec.ts
+++ b/frontend/tests/job/job-cost-entry-data.spec.ts
@@ -60,7 +60,7 @@ const getJobIdFromUrl = (url: string): string => {
 async function navigateToCostTab(
   page: Page,
   jobUrl: string,
-  tab: 'estimate' | 'actual',
+  tab: 'estimate' | 'quote' | 'actual',
 ): Promise<void> {
   await page.goto(`${jobUrl.split('?')[0]}?tab=${tab}`)
   await page.waitForLoadState('networkidle')
@@ -69,7 +69,7 @@ async function navigateToCostTab(
   await page.locator('[data-row-id]').last().waitFor({ timeout: 10000 })
 }
 
-async function fetchCostSet(page: Page, jobId: string, kind: 'estimate' | 'actual') {
+async function fetchCostSet(page: Page, jobId: string, kind: 'estimate' | 'quote' | 'actual') {
   const response = await page.request.get(`/api/job/jobs/${jobId}/cost_sets/${kind}/`)
   expect(response.ok()).toBe(true)
   return (await response.json()) as CostSet
@@ -176,6 +176,12 @@ function waitForCostLineCreate(page: Page): Promise<Response> {
   )
 }
 
+function waitForAnyCostLineCreate(page: Page): Promise<Response> {
+  return page.waitForResponse(
+    (res) => res.url().includes('/cost_lines') && res.request().method() === 'POST',
+  )
+}
+
 function waitForCostLinePatch(page: Page): Promise<Response> {
   return page.waitForResponse(
     (res) =>
@@ -245,6 +251,57 @@ async function editNumberCell(
   await patch
 }
 
+async function createAdjustmentFromNewRow(
+  page: Page,
+  description: string,
+  quantity: string,
+  unitCost: string,
+  unitRevenue: string,
+  expectedStatus = 201,
+): Promise<string> {
+  const rows = page.locator('[data-automation-id^="DataTable-row-"]')
+  const initialRowCount = await rows.count()
+  const trailingRow = rows.last()
+  const draftRowId = await trailingRow.getAttribute('data-row-id')
+  if (!draftRowId) throw new Error('Trailing cost row has no stable row ID')
+  const trailingDescription = trailingRow.locator('[data-grid-col="desc"]')
+
+  await trailingDescription.click()
+  await page.keyboard.type(description)
+  // Business risk: promoting the phantom with a different row identity replaces the textarea
+  // after its first character, moving focus and truncating normal keyboard input.
+  const promotedRow = page.locator(`[data-row-id="${draftRowId}"]`)
+  const promotedDescription = promotedRow.locator('[data-grid-col="desc"]')
+  await expect(promotedDescription).toBeFocused()
+  await expect(promotedDescription).toHaveValue(description)
+  await promotedDescription.press('Tab')
+
+  // Business risk: API-seeded adjustments bypass the phantom-row promotion that keeps entry
+  // continuous, so they allowed this user-visible regression to pass unnoticed.
+  await expect(rows).toHaveCount(initialRowCount + 1)
+  await expect(rows.last().locator('[data-grid-col="desc"]')).toHaveValue('')
+
+  const quantityInput = promotedRow.locator('[data-grid-col="quantity"]')
+  await quantityInput.fill(quantity)
+  await quantityInput.press('Tab')
+
+  const createResponse = waitForAnyCostLineCreate(page)
+  const unitCostInput = promotedRow.locator('[data-grid-col="unit_cost"]')
+  await unitCostInput.fill(unitCost)
+  await unitCostInput.press('Tab')
+
+  // Business risk: a fast keyboard user reaches Unit Revenue before the create response.
+  // Waiting for POST here would hide stale-response data loss in the draft lifecycle.
+  const unitRevenueInput = promotedRow.locator('[data-grid-col="unit_rev"]')
+  await unitRevenueInput.fill(unitRevenue)
+  await unitRevenueInput.press('Tab')
+
+  const response = await createResponse
+  const responseBody = await response.text()
+  expect(response.status(), responseBody).toBe(expectedStatus)
+  return draftRowId
+}
+
 async function deleteRow(page: Page, rowIndex: number): Promise<void> {
   page.once('dialog', (dialog) => dialog.accept())
   const deleteResponse = waitForCostLineDelete(page)
@@ -281,6 +338,78 @@ function sumRevenue(lines: CostLine[]): number {
 }
 
 test.describe('job cost entry data-first scenarios', () => {
+  test.describe('quote draft failure', () => {
+    test.use({
+      expectedConsoleErrors: [
+        'Failed to load resource: the server responded with a status of 503',
+        'Failed to create cost line: AxiosError: Request failed with status code 503',
+      ],
+    })
+
+    test('retains local drafts through delete, failed save, and retry', async ({
+      authenticatedPage: page,
+      sharedEditJobUrl,
+    }) => {
+      const jobId = getJobIdFromUrl(sharedEditJobUrl)
+      const discardedDesc = `E2E quote discarded ${Date.now()}`
+      const adjustmentDesc = `E2E quote adjustment ${Date.now()}`
+
+      await navigateToCostTab(page, sharedEditJobUrl, 'quote')
+
+      const rows = page.locator('[data-automation-id^="DataTable-row-"]')
+      const initialRowCount = await rows.count()
+      const discardedRow = rows.last()
+      const discardedRowId = await discardedRow.getAttribute('data-row-id')
+      if (!discardedRowId) throw new Error('Trailing quote row has no stable row ID')
+      await discardedRow.locator('[data-grid-col="desc"]').fill(discardedDesc)
+      await expect(rows).toHaveCount(initialRowCount + 1)
+      await autoId(page, `SmartCostLinesTable-delete-${initialRowCount - 1}`).click()
+      await expect(page.locator(`[data-row-id="${discardedRowId}"]`)).toHaveCount(0)
+      await expect(rows).toHaveCount(initialRowCount)
+
+      const createUrl = `**/api/job/jobs/${jobId}/cost_sets/quote/cost_lines/`
+      let failNextCreate = true
+      await page.route(createUrl, async (route) => {
+        if (route.request().method() === 'POST' && failNextCreate) {
+          failNextCreate = false
+          await route.fulfill({
+            status: 503,
+            contentType: 'application/json',
+            body: JSON.stringify({ detail: 'E2E forced create failure' }),
+          })
+          return
+        }
+        await route.continue()
+      })
+
+      const failedDraftId = await createAdjustmentFromNewRow(
+        page,
+        adjustmentDesc,
+        '4',
+        '-11',
+        '-17',
+        503,
+      )
+      await page.unroute(createUrl)
+
+      const failedRow = page.locator(`[data-row-id="${failedDraftId}"]`)
+      await expect(failedRow).toContainText('Save failed')
+      const retryResponse = waitForAnyCostLineCreate(page)
+      await failedRow.locator('[data-grid-col="unit_rev"]').focus()
+      await failedRow.locator('[data-grid-col="unit_rev"]').press('Tab')
+      const response = await retryResponse
+      const responseBody = await response.text()
+      expect(response.status(), responseBody).toBe(201)
+
+      const quote = await fetchCostSet(page, jobId, 'quote')
+      const adjustment = findLine(quote.cost_lines, adjustmentDesc, 'adjust')
+      expect(money(adjustment.quantity)).toBeCloseTo(4, 2)
+      expect(money(adjustment.unit_cost)).toBeCloseTo(-11, 2)
+      expect(money(adjustment.unit_rev)).toBeCloseTo(-17, 2)
+      expect(quote.cost_lines.some((line) => line.desc === discardedDesc)).toBe(false)
+    })
+  })
+
   test('estimate create edit replace delete reconciles persisted costs', async ({
     authenticatedPage: page,
   }) => {
@@ -345,16 +474,7 @@ test.describe('job cost entry data-first scenarios', () => {
       .click()
     await replacePatch
 
-    await createCostLineByApi(page, jobId, 'estimate', {
-      kind: 'adjust',
-      desc: adjustmentDesc,
-      quantity: 1,
-      unit_cost: -20,
-      unit_rev: -30,
-      accounting_date: accountingDate,
-      ext_refs: {},
-      meta: { source: 'e2e_adjustment' },
-    })
+    await createAdjustmentFromNewRow(page, adjustmentDesc, '2', '-15', '-25')
     await createCostLineByApi(page, jobId, 'estimate', {
       kind: 'adjust',
       desc: deletedDesc,
@@ -369,11 +489,6 @@ test.describe('job cost entry data-first scenarios', () => {
     await navigateToCostTab(page, jobUrl, 'estimate')
     let adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
     expect(adjustmentIndex).toBeGreaterThanOrEqual(0)
-    await editNumberCell(page, adjustmentIndex, 'quantity', '2')
-    adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
-    await editNumberCell(page, adjustmentIndex, 'unit-cost', '-15')
-    adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
-    await editNumberCell(page, adjustmentIndex, 'unit-rev', '-25')
 
     const deletedIndex = await findRowIndexByDescription(page, deletedDesc)
     expect(deletedIndex).toBeGreaterThanOrEqual(0)
@@ -467,16 +582,7 @@ test.describe('job cost entry data-first scenarios', () => {
     expect(materialIndex).toBeGreaterThanOrEqual(0)
     await editNumberCell(page, materialIndex, 'quantity', '2')
 
-    await createCostLineByApi(page, jobId, 'actual', {
-      kind: 'adjust',
-      desc: adjustmentDesc,
-      quantity: 1,
-      unit_cost: -10,
-      unit_rev: -15,
-      accounting_date: accountingDate,
-      ext_refs: {},
-      meta: { source: 'e2e_adjustment' },
-    })
+    await createAdjustmentFromNewRow(page, adjustmentDesc, '3', '-12', '-18')
     await createCostLineByApi(page, jobId, 'actual', {
       kind: 'adjust',
       desc: deletedDesc,
@@ -491,11 +597,6 @@ test.describe('job cost entry data-first scenarios', () => {
     await navigateToCostTab(page, jobUrl, 'actual')
     let adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
     expect(adjustmentIndex).toBeGreaterThanOrEqual(0)
-    await editNumberCell(page, adjustmentIndex, 'quantity', '3')
-    adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
-    await editNumberCell(page, adjustmentIndex, 'unit-cost', '-12')
-    adjustmentIndex = await findRowIndexByDescription(page, adjustmentDesc)
-    await editNumberCell(page, adjustmentIndex, 'unit-rev', '-18')
 
     const deletedIndex = await findRowIndexByDescription(page, deletedDesc)
     expect(deletedIndex).toBeGreaterThanOrEqual(0)