diff --git a/actions/sprints.ts b/actions/sprints.ts
index 78fe7ce..499a87e 100644
--- a/actions/sprints.ts
+++ b/actions/sprints.ts
@@ -54,6 +54,65 @@ export type CreateSprintWithSelectionResult =
     }
   | { error: string; code: number }
 
+const updateSprintSchema = z.object({
+  sprintId: z.string().min(1),
+  fields: z
+    .object({
+      goal: z.string().min(1).max(2000).optional(),
+      startAt: z.string().date().nullable().optional(),
+      endAt: z.string().date().nullable().optional(),
+    })
+    .refine(
+      (data) => Object.keys(data).length > 0,
+      'Minstens één veld vereist',
+    ),
+})
+
+export type UpdateSprintInput = z.infer<typeof updateSprintSchema>
+
+export type UpdateSprintResult =
+  | { success: true; sprintId: string }
+  | { error: string; code: number }
+
+export async function updateSprintAction(
+  input: UpdateSprintInput,
+): Promise<UpdateSprintResult> {
+  const session = await getSession()
+  if (!session.userId) return { error: 'Niet ingelogd', code: 403 }
+  if (session.isDemo) return { error: 'Niet beschikbaar in demo-modus', code: 403 }
+
+  const parsed = updateSprintSchema.safeParse(input)
+  if (!parsed.success) return { error: 'Validatie mislukt', code: 422 }
+
+  const sprint = await prisma.sprint.findFirst({
+    where: {
+      id: parsed.data.sprintId,
+      product: productAccessFilter(session.userId),
+    },
+    select: { id: true, product_id: true },
+  })
+  if (!sprint) return { error: 'Sprint niet gevonden', code: 403 }
+
+  const data: { sprint_goal?: string; start_date?: Date | null; end_date?: Date | null } = {}
+  if (parsed.data.fields.goal !== undefined) {
+    data.sprint_goal = parsed.data.fields.goal
+  }
+  if (parsed.data.fields.startAt !== undefined) {
+    data.start_date = parseDate(parsed.data.fields.startAt)
+  }
+  if (parsed.data.fields.endAt !== undefined) {
+    data.end_date = parseDate(parsed.data.fields.endAt)
+  }
+
+  await prisma.sprint.update({
+    where: { id: parsed.data.sprintId },
+    data,
+  })
+  revalidatePath(`/products/${sprint.product_id}`, 'layout')
+
+  return { success: true, sprintId: parsed.data.sprintId }
+}
+
 const commitSprintMembershipSchema = z.object({
   activeSprintId: z.string().min(1),
   adds: z.array(z.string()),
@@ -344,10 +403,10 @@ export async function createSprintAction(_prevState: unknown, formData: FormData
   const product = await getAccessibleProduct(parsed.data.productId, session.userId)
   if (!product) return { error: 'Product niet gevonden', code: 403 }
 
-  const existing = await prisma.sprint.findFirst({
-    where: { product_id: parsed.data.productId, status: 'OPEN' },
-  })
-  if (existing) return { error: 'Er is al een actieve Sprint voor dit product', sprintId: existing.id, code: 422 }
+  // PBI-79 / ST-1342: multi-OPEN sprints toegestaan. Bestaande OPEN sprints
+  // op hetzelfde product zijn geen reden meer om aanmaak te blokkeren —
+  // cross-sprint-conflicts worden per-story afgevangen in de membership-
+  // commit-flow.
 
   const sprint = await createWithCodeRetry(
     () => generateNextSprintCode(parsed.data.productId),
diff --git a/components/backlog/sprint-edit-dialog.tsx b/components/backlog/sprint-edit-dialog.tsx
new file mode 100644
index 0000000..4842a8a
--- /dev/null
+++ b/components/backlog/sprint-edit-dialog.tsx
@@ -0,0 +1,217 @@
+'use client'
+
+import { useRef, useState, useTransition } from 'react'
+import { useRouter } from 'next/navigation'
+import Link from 'next/link'
+import { toast } from 'sonner'
+import { Button } from '@/components/ui/button'
+import { Textarea } from '@/components/ui/textarea'
+import { Dialog, DialogContent, DialogTitle } from '@/components/ui/dialog'
+import {
+  useDirtyCloseGuard,
+  DirtyCloseGuardDialog,
+} from '@/components/shared/use-dirty-close-guard'
+import { useDialogSubmitShortcut } from '@/components/shared/use-dialog-submit-shortcut'
+import {
+  entityDialogContentClasses,
+  entityDialogFooterClasses,
+  entityDialogHeaderClasses,
+} from '@/components/shared/entity-dialog-layout'
+import { updateSprintAction } from '@/actions/sprints'
+import { debugProps } from '@/lib/debug'
+
+interface SprintEditDialogProps {
+  open: boolean
+  productId: string
+  sprint: {
+    id: string
+    code: string
+    sprint_goal: string
+    start_date?: string | null
+    end_date?: string | null
+  }
+  onOpenChange: (open: boolean) => void
+}
+
+function toDateInput(value: string | null | undefined): string {
+  if (!value) return ''
+  // Accept ISO datetime or YYYY-MM-DD; output YYYY-MM-DD.
+  const d = new Date(value)
+  if (Number.isNaN(d.getTime())) return ''
+  return d.toLocaleDateString('en-CA')
+}
+
+export function SprintEditDialog({
+  open,
+  productId,
+  sprint,
+  onOpenChange,
+}: SprintEditDialogProps) {
+  const [goal, setGoal] = useState(sprint.sprint_goal)
+  const [startDate, setStartDate] = useState(toDateInput(sprint.start_date))
+  const [endDate, setEndDate] = useState(toDateInput(sprint.end_date))
+  const [error, setError] = useState<string | null>(null)
+  const [dirty, setDirty] = useState(false)
+  const [isPending, startTransition] = useTransition()
+  const formRef = useRef<HTMLFormElement>(null)
+  const router = useRouter()
+
+  function reset() {
+    setGoal(sprint.sprint_goal)
+    setStartDate(toDateInput(sprint.start_date))
+    setEndDate(toDateInput(sprint.end_date))
+    setError(null)
+    setDirty(false)
+  }
+
+  const closeGuard = useDirtyCloseGuard(dirty, () => {
+    onOpenChange(false)
+    reset()
+  })
+
+  function handleSubmit(e: React.FormEvent) {
+    e.preventDefault()
+    const trimmed = goal.trim()
+    if (!trimmed) return
+    setError(null)
+    startTransition(async () => {
+      const result = await updateSprintAction({
+        sprintId: sprint.id,
+        fields: {
+          goal: trimmed,
+          startAt: startDate || null,
+          endAt: endDate || null,
+        },
+      })
+      if ('error' in result) {
+        setError(result.error)
+        toast.error(result.error)
+        return
+      }
+      toast.success('Sprint bijgewerkt')
+      onOpenChange(false)
+      router.refresh()
+    })
+  }
+
+  const handleKeyDown = useDialogSubmitShortcut(() =>
+    formRef.current?.requestSubmit(),
+  )
+
+  return (
+    <>
+      <Dialog
+        open={open}
+        onOpenChange={(o) => {
+          if (!o) closeGuard.attemptClose()
+          else onOpenChange(o)
+        }}
+      >
+        <DialogContent
+          showCloseButton={false}
+          onKeyDown={handleKeyDown}
+          className={entityDialogContentClasses}
+          {...debugProps(
+            'sprint-edit-dialog',
+            'SprintEditDialog',
+            'components/backlog/sprint-edit-dialog.tsx',
+          )}
+        >
+          <div className={entityDialogHeaderClasses}>
+            <DialogTitle className="text-xl font-semibold">
+              Sprint {sprint.code} bewerken
+            </DialogTitle>
+            <p className="text-xs text-muted-foreground mt-1">
+              Wijzig sprint-doel en datums. Voor afronding (per-story DONE/OPEN
+              beslissing) ga naar de sprint-pagina.
+            </p>
+          </div>
+
+          <form
+            ref={formRef}
+            id="sprint-edit-form"
+            onSubmit={handleSubmit}
+            onChange={() => setDirty(true)}
+            className="flex-1 overflow-y-auto px-6 py-6 space-y-6"
+          >
+            <div className="space-y-1.5">
+              <label className="text-sm font-medium text-foreground">
+                Sprint Goal <span className="text-error">*</span>
+              </label>
+              <Textarea
+                value={goal}
+                onChange={(e) => setGoal(e.target.value)}
+                required
+                rows={3}
+                autoFocus
+              />
+            </div>
+
+            <div className="grid grid-cols-2 gap-3">
+              <div className="space-y-1.5">
+                <label className="text-sm font-medium text-foreground">
+                  Startdatum
+                </label>
+                <input
+                  type="date"
+                  value={startDate}
+                  onChange={(e) => setStartDate(e.target.value)}
+                  className="w-full rounded-md border border-border bg-surface-container px-3 py-2 text-sm focus:outline-none focus:ring-1 focus:ring-primary"
+                />
+              </div>
+              <div className="space-y-1.5">
+                <label className="text-sm font-medium text-foreground">
+                  Einddatum
+                </label>
+                <input
+                  type="date"
+                  value={endDate}
+                  onChange={(e) => setEndDate(e.target.value)}
+                  className="w-full rounded-md border border-border bg-surface-container px-3 py-2 text-sm focus:outline-none focus:ring-1 focus:ring-primary"
+                />
+              </div>
+            </div>
+
+            <div className="pt-2 border-t border-border">
+              <Link
+                href={`/products/${productId}/sprint/${sprint.id}`}
+                className="text-sm text-primary hover:underline"
+              >
+                Sprint afronden… →
+              </Link>
+            </div>
+
+            {error && (
+              <div className="bg-error-container text-error-container-foreground rounded-lg px-3 py-2 text-sm border-l-4 border-error">
+                {error}
+              </div>
+            )}
+          </form>
+
+          <div className={entityDialogFooterClasses}>
+            <div className="flex justify-end gap-2">
+              <Button
+                type="button"
+                variant="ghost"
+                onClick={closeGuard.attemptClose}
+                disabled={isPending}
+              >
+                Annuleren
+              </Button>
+              <Button
+                type="submit"
+                form="sprint-edit-form"
+                disabled={isPending || !goal.trim()}
+                data-debug-id="sprint-edit-dialog__submit"
+              >
+                {isPending ? 'Opslaan…' : 'Opslaan'}
+              </Button>
+            </div>
+          </div>
+        </DialogContent>
+      </Dialog>
+
+      <DirtyCloseGuardDialog guard={closeGuard} />
+    </>
+  )
+}