web/src/components/plants/DeleteSeedLotModal.tsx

@@ -3,8 +3,7 @@ import { Alert } from '@/components/ui/Alert'
 import { Button } from '@/components/ui/Button'
 import { Modal } from '@/components/ui/Modal'
 import { errorMessage } from '@/lib/api'
-import { useDeleteSeedLot, type SeedLot } from '@/lib/seedLots'
-import { formatQuantity } from './SeedLotList'
+import { formatQuantity, useDeleteSeedLot, type SeedLot } from '@/lib/seedLots'
 
 /**
  * Retire a lot. Worth confirming because it's the one place cost and germination

web/src/components/plants/PlantCard.tsx

@@ -1,9 +1,10 @@
 import { useState } from 'react'
 import { PlantIcon } from './PlantIcon'
-import { LotStateChip, SeedLotList, formatQuantity } from './SeedLotList'
+import { LotStateChip, SeedLotList } from './SeedLotList'
+import { SourceLink } from './SourceLink'
 import { cardActionClass, cardDangerClass } from '@/components/ui/cardActions'
 import { CATEGORY_LABELS, isBuiltin, type Plant } from '@/lib/plants'
-import { safeExternalUrl, summarizeLots, type SeedLot } from '@/lib/seedLots'
+import { formatQuantity, summarizeLots, type SeedLot } from '@/lib/seedLots'
 import { formatSpacing, type UnitPref } from '@/lib/units'
 
 /**
@@ -37,7 +38,7 @@ export function PlantCard({
   const builtin = isBuiltin(plant)
   const [showLots, setShowLots] = useState(false)
   const summary = summarizeLots(lots)
-  const sourceUrl = safeExternalUrl(plant.sourceUrl)
+
   return (
     <div className="flex flex-col rounded-xl border border-border bg-surface">
       <div className="flex items-start gap-3 p-4">
@@ -54,21 +55,10 @@ export function PlantCard({
           <p className="mt-0.5 text-sm text-muted">
             {CATEGORY_LABELS[plant.category]} · {formatSpacing(plant.spacingCm, unit)} spacing
           </p>
-          {(plant.vendor || sourceUrl) && (
+          {(plant.vendor || plant.sourceUrl) && (
             <p className="mt-0.5 flex flex-wrap items-center gap-1.5 text-xs text-muted">
               {plant.vendor && <span>{plant.vendor}</span>}
-              {sourceUrl && (
-                <a
-                  href={sourceUrl}
-                  target="_blank"
-                  // The href is a URL somebody pasted; noopener keeps it from
-                  // getting a handle back to this window.
-                  rel="noopener noreferrer"
-                  className="underline decoration-dotted underline-offset-2 hover:text-fg"
-                >
-                  source ↗
-                </a>
-              )}
+              <SourceLink url={plant.sourceUrl} />
             </p>
           )}
           {plant.notes && <p className="mt-1 line-clamp-2 text-xs text-muted">{plant.notes}</p>}

web/src/components/plants/SeedLotList.tsx

@@ -1,10 +1,11 @@
 import { Button } from '@/components/ui/Button'
 import { cn } from '@/lib/cn'
+import { SourceLink } from './SourceLink'
 import {
   formatCost,
+  formatQuantity,
   formatUnitCost,
   lotState,
-  safeExternalUrl,
   type LotState,
   type SeedLot,
 } from '@/lib/seedLots'
@@ -20,7 +21,9 @@ const STATE_LABEL: Record<LotState, string> = {
 // Encoded in colour AND words, because this is the thing you skim down a list of
 // twenty packets deciding what to order — a bare number doesn't survive that.
 const STATE_CLASS: Record<LotState, string> = {
-  over: 'bg-amber-500/20 text-amber-800 dark:text-amber-300',
+  // "over" is a discrepancy to look at rather than a shortage to act on, so it
+  // reads as a distinct warning rather than sharing "low"'s styling.
+  over: 'bg-orange-500/25 text-orange-900 dark:text-orange-200',
   empty: 'bg-red-500/15 text-red-800 dark:text-red-300',
   low: 'bg-amber-500/20 text-amber-800 dark:text-amber-300',
   ok: 'bg-accent/20 text-accent-strong',
@@ -110,7 +113,6 @@ function LotRow({
   onEdit: () => void
   onDelete: () => void
 }) {
-  const url = safeExternalUrl(lot.sourceUrl)
   const cost = formatCost(lot.costCents)
   const unitCost = formatUnitCost(lot)
 
@@ -130,18 +132,7 @@ function LotRow({
             {lot.purchasedAt && <span>bought {lot.purchasedAt}</span>}
             {lot.germinationPct != null && <span>{lot.germinationPct}% germ.</span>}
             {cost && <span>{unitCost ? `${cost} (${unitCost})` : cost}</span>}
-            {url && (
-              <a
-                href={url}
-                target="_blank"
-                // noopener/noreferrer on every outbound link: the target is a URL
-                // someone pasted, and window.opener would hand it a handle back.
-                rel="noopener noreferrer"
-                className="underline decoration-dotted underline-offset-2 hover:text-fg"
-              >
-                source ↗
-              </a>
-            )}
+            <SourceLink url={lot.sourceUrl} />
           </p>
           <RemainingBar lot={lot} />
         </div>
@@ -168,9 +159,3 @@ function LotRow({
     </div>
   )
 }
-
-/** Quantities are stored as REAL because grams and ounces are fractional, but a
- *  whole number of seeds shouldn't render as "100.0". */
-export function formatQuantity(n: number): string {
-  return Number.isInteger(n) ? String(n) : n.toFixed(1)
-}

web/src/components/plants/SeedLotModal.tsx

@@ -7,6 +7,7 @@ import { TextArea } from '@/components/ui/TextArea'
 import { TextField } from '@/components/ui/TextField'
 import { errorMessage } from '@/lib/api'
 import {
+  conflictSeedLot,
   LOT_UNITS,
   safeExternalUrl,
   useCreateSeedLot,
@@ -49,11 +50,14 @@ export function SeedLotModal({
   const [sku, setSku] = useState(lot?.sku ?? '')
   const [lotCode, setLotCode] = useState(lot?.lotCode ?? '')
   const [notes, setNotes] = useState(lot?.notes ?? '')
+  const [version, setVersion] = useState(lot?.version ?? 0)
+  const [conflict, setConflict] = useState<string | null>(null)
   const [error, setError] = useState<string | null>(null)
 
   async function onSubmit(e: FormEvent) {
     e.preventDefault()
     setError(null)
+    setConflict(null)
 
     const qty = quantity.trim() === '' ? 0 : Number(quantity)
     if (!Number.isFinite(qty) || qty < 0) {
@@ -109,12 +113,32 @@ export function SeedLotModal({
 
     try {
       if (isEdit) {
-        await update.mutateAsync({ id: lot.id, version: lot.version, ...input })
+        await update.mutateAsync({ id: lot.id, version, ...input })
       } else {
         await create.mutateAsync(input)
       }
       onClose()
     } catch (err) {
+      const current = conflictSeedLot(err)
+      if (current) {
+        // Someone edited this lot elsewhere. Rebase onto the fresh row so a
+        // re-save applies, rather than making them retype everything — the same
+        // contract every other version-guarded form here honours.
+        setVersion(current.version)
+        setVendor(current.vendor)
+        setSourceUrl(current.sourceUrl)
+        setQuantity(String(current.quantity))
+        setUnit(current.unit)
+        setPurchasedAt(current.purchasedAt ?? '')
+        setPackedForYear(current.packedForYear != null ? String(current.packedForYear) : '')
+        setCost(current.costCents != null ? (current.costCents / 100).toFixed(2) : '')
+        setGermination(current.germinationPct != null ? String(current.germinationPct) : '')
+        setSku(current.sku)
+        setLotCode(current.lotCode)
+        setNotes(current.notes)
+        setConflict('This lot changed elsewhere. The latest values are shown — review and save again.')
+        return
+      }
       setError(errorMessage(err, isEdit ? 'Could not save the lot.' : 'Could not record the lot.'))
     }
   }
@@ -122,6 +146,8 @@ export function SeedLotModal({
   return (
     <Modal title={isEdit ? 'Edit seed lot' : `Seed lot — ${plant.name}`} onClose={onClose} busy={pending}>
       <form onSubmit={onSubmit} className="flex flex-col gap-3">
+        {conflict && <Alert tone="info">{conflict}</Alert>}
+
         <div className="grid grid-cols-2 gap-3">
           <TextField
             label="Quantity"

web/src/components/plants/SourceLink.tsx

@@ -0,0 +1,27 @@
+import { safeExternalUrl } from '@/lib/seedLots'
+
+/**
+ * A link out to where seed came from.
+ *
+ * The href is a URL somebody pasted, so it is re-checked here before rendering
+ * and carries rel="noopener noreferrer" — the server scheme-checks it too (#50),
+ * but a link is rendered from whatever the client was handed, and "the backend
+ * validated it" is not a reason to hand javascript: to an anchor tag.
+ *
+ * Renders nothing at all when the URL is absent or unsafe, so callers don't each
+ * have to remember to guard.
+ */
+export function SourceLink({ url, label = 'source' }: { url: string; label?: string }) {
+  const safe = safeExternalUrl(url)
+  if (!safe) return null
+  return (
+    <a
+      href={safe}
+      target="_blank"
+      rel="noopener noreferrer"
+      className="underline decoration-dotted underline-offset-2 hover:text-fg"
+    >
+      {label} ↗
+    </a>
+  )
+}

web/src/editor/PlantPicker.tsx

@@ -4,8 +4,16 @@ import { fieldControlClass } from '@/components/ui/field'
 import { CategoryChips } from '@/components/plants/CategoryChips'
 import { PlantIcon } from '@/components/plants/PlantIcon'
 import { CATEGORY_LABELS, filterPlants, usePlants, type CategoryFilter, type Plant } from '@/lib/plants'
-import { lotsByPlant, lotState, useSeedLots, type SeedLot } from '@/lib/seedLots'
-import { LotStateChip, formatQuantity } from '@/components/plants/SeedLotList'
+import {
+  attributableLots,
+  formatQuantity,
+  lotsByPlant,
+  lotState,
+  summarizeLots,
+  useSeedLots,
+  type SeedLot,
+} from '@/lib/seedLots'
+import { LotStateChip } from '@/components/plants/SeedLotList'
 import { formatSpacing, type UnitPref } from '@/lib/units'
 
 const RECENT_KEY = 'pansy:recent-plants'
@@ -85,12 +93,15 @@ export function PlantPicker({
   }, [all, recent, query])
 
   function choose(p: Plant) {
-    const lots = (lotsFor.get(p.id) ?? []).filter((l) => l.remaining > 0)
+    const lots = attributableLots(lotsFor.get(p.id) ?? [])
     if (lots.length > 1) {
       setChoosingLotFor(p)
       return
     }
     setRecent(recordRecent(p.id))
+    // A single lot attributes even when its count says empty. The count records
+    // what was written down, not a fact about the packet — dropping attribution
+    // there would make a wrong number harder to correct rather than easier.
     onSelect(p, lots[0])
   }
 
@@ -121,12 +132,12 @@ export function PlantPicker({
 
   // What's left, shown where you're deciding what to plant. Silent when there
   // are no lots — most plants won't have any, and "0 left" on all of them would
-  // be noise that trains you to ignore the number.
+  // be noise that trains you to ignore the number. summarizeLots owns the
+  // unit-agreement rule; a second copy of it here would drift.
   function remainingLabel(lots: SeedLot[]): string {
     if (lots.length === 0) return ''
-    const unitName = lots.every((l) => l.unit === lots[0].unit) ? ` ${lots[0].unit}` : ''
-    const total = lots.reduce((sum, l) => sum + l.remaining, 0)
-    return ` · ${formatQuantity(total)}${unitName} left`
+    const { remaining, unit } = summarizeLots(lots)
+    return ` · ${formatQuantity(remaining)}${unit ? ` ${unit}` : ''} left`
   }
 
   return (
@@ -169,9 +180,7 @@ export function PlantPicker({
             <p className="px-3 pb-1 pt-2 text-xs font-semibold uppercase tracking-wide text-muted">
               Which lot of {choosingLotFor.name}?
             </p>
-            {(lotsFor.get(choosingLotFor.id) ?? [])
-              .filter((l) => l.remaining > 0)
-              .map((lot) => (
+            {attributableLots(lotsFor.get(choosingLotFor.id) ?? []).map((lot) => (
                 <button
                   key={lot.id}
                   type="button"

web/src/lib/seedLots.test.ts

@@ -1,6 +1,8 @@
 import { describe, expect, it } from 'vitest'
 import {
+  attributableLots,
   formatCost,
+  formatQuantity,
   formatUnitCost,
   lotState,
   lotsByPlant,
@@ -119,3 +121,29 @@ describe('lotsByPlant', () => {
     expect(lotsByPlant(undefined).size).toBe(0)
   })
 })
+
+describe('attributableLots', () => {
+  // An exhausted lot is still offered: the count records what was written down,
+  // not a fact about the packet, so refusing to attribute a planting because the
+  // number says zero would make a wrong number harder to correct, not easier.
+  it('offers exhausted lots, just not first', () => {
+    const empty = lot({ id: 1, remaining: 0 })
+    const full = lot({ id: 2, remaining: 100 })
+    expect(attributableLots([empty, full]).map((l) => l.id)).toEqual([2, 1])
+    expect(attributableLots([empty]).length).toBe(1)
+  })
+
+  it("doesn't mutate its input", () => {
+    const lots = [lot({ id: 1, remaining: 0 }), lot({ id: 2, remaining: 100 })]
+    attributableLots(lots)
+    expect(lots.map((l) => l.id)).toEqual([1, 2])
+  })
+})
+
+describe('formatQuantity', () => {
+  it('keeps whole counts whole and fractional ones readable', () => {
+    expect(formatQuantity(100)).toBe('100')
+    expect(formatQuantity(12.5)).toBe('12.5')
+    expect(formatQuantity(-15)).toBe('-15') // over-planted lots go negative
+  })
+})

web/src/lib/seedLots.ts

@@ -6,7 +6,7 @@
 
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { z } from 'zod'
-import { api } from './api'
+import { ApiError, api } from './api'
 
 export const lotUnitSchema = z.enum(['seeds', 'grams', 'ounces', 'packets', 'bulbs', 'plants'])
 export type LotUnit = z.infer<typeof lotUnitSchema>
@@ -104,6 +104,27 @@ export function useDeleteSeedLot() {
   })
 }
 
+/**
+ * The lots a placement could be attributed to, best first.
+ *
+ * Lots with seed left come first, but an exhausted one is still offered: the
+ * count is a record of what you wrote down, not a fact about the packet, and
+ * refusing to attribute a planting because the number says zero would make the
+ * number harder to correct rather than easier.
+ */
+export function attributableLots(lots: SeedLot[]): SeedLot[] {
+  return [...lots].sort((a, b) => Number(b.remaining > 0) - Number(a.remaining > 0))
+}
+
+/** The current server row carried by a 409, so an edit form can rebase onto it
+ *  and the user can re-save rather than losing what they typed. Every other
+ *  entity's form does this; a lot is no different. */
+export function conflictSeedLot(err: unknown): SeedLot | null {
+  if (!(err instanceof ApiError) || !err.isConflict) return null
+  const parsed = seedLotSchema.safeParse((err.body as { current?: unknown })?.current)
+  return parsed.success ? parsed.data : null
+}
+
 /** Group lots by the plant they belong to. */
 export function lotsByPlant(lots: SeedLot[] | undefined): Map<number, SeedLot[]> {
   const map = new Map<number, SeedLot[]>()
@@ -149,6 +170,12 @@ export function summarizeLots(lots: SeedLot[]): { remaining: number; unit: LotUn
   return { remaining, unit, state }
 }
 
+/** Quantities are stored as REAL because grams and ounces are fractional, but a
+ *  whole number of seeds shouldn't render as "100.0". */
+export function formatQuantity(n: number): string {
+  return Number.isInteger(n) ? String(n) : n.toFixed(1)
+}
+
 /** Whole currency from cents, e.g. 499 → "$4.99". */
 export function formatCost(cents: number | undefined): string | null {
   if (cents == null) return null

web/src/pages/GardenEditorPage.tsx

@@ -31,7 +31,7 @@ import {
 import { toEditorPlanting } from '@/lib/plantings'
 import type { Plant } from '@/lib/plants'
 import { useJournalCounts } from '@/lib/journal'
-import type { SeedLot } from '@/lib/seedLots'
+import { attributableLots, lotsByPlant, useSeedLots, type SeedLot } from '@/lib/seedLots'
 import { useSeedTray } from '@/lib/seedTray'
 import { usePageTitle } from '@/lib/usePageTitle'
 
@@ -75,6 +75,8 @@ export function GardenEditorPage() {
   const updateObject = useUpdateObject(gid)
   const ensurePlant = useEnsurePlantInFull(gid)
   const { trayPlants, add: addToTray, remove: removeFromTray } = useSeedTray(gid)
+  const seedLots = useSeedLots()
+  const lotsByPlantId = useMemo(() => lotsByPlant(seedLots.data), [seedLots.data])
 
   // Which plant-picker flow is open: 'place' arms a plant for repeat placement;
   // 'change' swaps the selected plop's plant.
@@ -278,8 +280,17 @@ export function GardenEditorPage() {
   // Arm a plant for tap-to-place. The full catalog carries plants not yet in this
   // garden's /full payload, so make sure the chosen one is in the cache first —
   // otherwise its placed plops render without an icon/color until a refetch.
+  // The Seed Tray arms a plant directly, without going through the picker, so it
+  // has to do the picker's single-lot auto-attribution itself — otherwise the
+  // quickest way to place a plant is the one path that silently loses which
+  // packet it came from. Several lots is genuinely ambiguous, so that case stays
+  // unattributed rather than guessing; the picker is where you choose.
   function armPlant(plant: Plant, lot?: SeedLot) {
     ensurePlant(plant)
+    if (lot === undefined) {
+      const lots = attributableLots(lotsByPlantId.get(plant.id) ?? [])
+      lot = lots.length === 1 ? lots[0] : undefined
+    }
     setArmedPlant(plant, lot?.id ?? null)
   }