diff --git a/app/src/lib/period-lock/lock-periods.test.js b/app/src/lib/period-lock/lock-periods.test.js
index 39ebddd3..89d32ac8 100644
--- a/app/src/lib/period-lock/lock-periods.test.js
+++ b/app/src/lib/period-lock/lock-periods.test.js
@@ -5,6 +5,8 @@ import {
   listCheckpoints,
   lockLevel,
   rangesWithStatus,
+  weekParts,
+  workweekRange,
 } from "./lock-periods.ts";
 
 function workdays(from, to, today, lockedThrough) {
@@ -99,3 +101,26 @@ test("unlocking skips certified days instead of spanning them", () => {
     { from: "2026-10-22", to: "2026-10-23" },
   ]);
 });
+
+describe("locking Monday to Friday", () => {
+  test("a Sunday belongs to the week that started six days before", () => {
+    expect(workweekRange("2026-11-08")).toEqual({
+      from: "2026-11-02",
+      to: "2026-11-06",
+    });
+  });
+
+  test("a week crossing a month end keeps its Friday", () => {
+    expect(workweekRange("2026-07-01")).toEqual({
+      from: "2026-06-29",
+      to: "2026-07-03",
+    });
+  });
+
+  test("a month ending on a Friday offers Mon–Fri once", () => {
+    expect(weekParts("2026-07-29")).toEqual([
+      { from: "2026-07-27", to: "2026-07-31" },
+      { from: "2026-08-01", to: "2026-08-02" },
+    ]);
+  });
+});
diff --git a/app/src/lib/period-lock/lock-periods.ts b/app/src/lib/period-lock/lock-periods.ts
index 41f61f66..acd29254 100644
--- a/app/src/lib/period-lock/lock-periods.ts
+++ b/app/src/lib/period-lock/lock-periods.ts
@@ -47,6 +47,12 @@ export function weekRange(date: string): LockRange {
   };
 }
 
+/** Monday through Friday, leaving the weekend open. */
+export function workweekRange(date: string): LockRange {
+  const { from } = weekRange(date);
+  return { from, to: toIsoDate(addDays(parseISO(from), 4)) };
+}
+
 export function monthRange(date: string): LockRange {
   const day = parseISO(date);
   return {
@@ -80,6 +86,19 @@ export function splitAtMonthEnd(range: LockRange): Array<LockRange> | null {
   ];
 }
 
+export const isSameRange = (a: LockRange | null, b: LockRange) =>
+  a?.from === b.from && a?.to === b.to;
+
+/** What a week can be locked as: Mon–Fri, then any split at a month end. */
+export function weekParts(date: string): Array<LockRange> {
+  const workweek = workweekRange(date);
+  // A month ending on a Friday would offer Mon–Fri twice.
+  const monthParts = (splitAtMonthEnd(weekRange(date)) ?? []).filter(
+    (part) => !isSameRange(part, workweek),
+  );
+  return [workweek, ...monthParts];
+}
+
 export const isLocked = (day: LockDay) => day.status !== "open";
 
 /** Every calendar day counts: an empty weekend left open keeps its week open in Kleer. */
diff --git a/app/src/routes/_layout/time-tracking/-components/period-lock/sign-off.tsx b/app/src/routes/_layout/time-tracking/-components/period-lock/sign-off.tsx
index 2ad6e9a8..1d60c102 100644
--- a/app/src/routes/_layout/time-tracking/-components/period-lock/sign-off.tsx
+++ b/app/src/routes/_layout/time-tracking/-components/period-lock/sign-off.tsx
@@ -19,6 +19,7 @@ import {
   formatRange,
   hoursShort,
   isLocked,
+  isSameRange,
   isoWeekOf,
   lockedThrough,
   lockLevel,
@@ -26,10 +27,11 @@ import {
   needsLock,
   rangesWithStatus,
   scopeAction,
-  splitAtMonthEnd,
   summarize,
   toIsoDate,
+  weekParts,
   weekRange,
+  workweekRange,
   type LockDay,
   type LockRange,
 } from "@/lib/period-lock/lock-periods";
@@ -42,6 +44,7 @@ import { cn, formatHoursMinutes } from "@/lib/utils";
 import { LockGlyph } from "./lock-glyph";
 
 const SETTLE_MS = 1700;
+const WORKWEEK_LABEL = "Mon–Fri";
 
 type Kind = "due" | "week" | "month";
 type Selection = {
@@ -90,6 +93,9 @@ function step({ kind, anchor }: Selection, direction: 1 | -1): string {
 
 function titleOf(selection: Selection) {
   if (selection.name) return selection.name;
+  if (isSameRange(selection.part, workweekRange(selection.anchor))) {
+    return `Week ${isoWeekOf(selection.anchor)}, ${WORKWEEK_LABEL}`;
+  }
   if (selection.part) return formatRange(selection.part);
   if (selection.kind === "month") {
     return format(parseISO(selection.anchor), "MMMM yyyy");
@@ -136,7 +142,12 @@ function useSignOff() {
 
   const coversOneWeek = weekRange(range.from).from === weekRange(range.to).from;
   const parts =
-    selection.kind === "week" ? splitAtMonthEnd(weekRange(selection.anchor)) : null;
+    selection.kind === "week"
+      ? weekParts(selection.anchor).map((part, index) => ({
+          range: part,
+          label: index === 0 ? WORKWEEK_LABEL : formatRange(part),
+        }))
+      : [];
 
   return {
     today,
@@ -176,8 +187,9 @@ function useSignOff() {
       try {
         await lock(range, rangesWithStatus(days, "open"));
       } catch {
-        // The failure has its toast, and the period stays as it was.
-        setPicked(null);
+        // The failure has its toast. Keep what was picked so a retry locks
+        // the same days, even after part of a range crossing months locked.
+        setPicked(picked);
         return;
       }
       setIsJustLocked(true);
@@ -449,27 +461,31 @@ function PeriodControls({ review }: { review: Review }) {
           <ChevronRight className="h-4 w-4" />
         </Button>
       </span>
-      {review.parts?.map((part) => {
-        const isActive =
-          review.selection.part?.from === part.from &&
-          review.selection.part.to === part.to;
-        return (
-          <button
-            key={part.from}
-            type="button"
-            aria-pressed={isActive}
-            onClick={() => review.pickPart(isActive ? null : part)}
-            className={cn(
-              "rounded-md px-2 py-0.5 text-xs transition-colors",
-              isActive
-                ? "bg-primary/15 text-foreground"
-                : "text-muted-foreground hover:bg-muted hover:text-foreground",
-            )}
-          >
-            {formatRange(part)}
-          </button>
-        );
-      })}
+      {review.parts.length > 0 && (
+        // The chips wrap as one group, never one stray chip on its own line.
+        <span className="flex gap-1">
+          {review.parts.map(({ range, label }) => {
+            const isActive = isSameRange(review.selection.part, range);
+            return (
+              <button
+                key={`${range.from}-${range.to}`}
+                type="button"
+                aria-pressed={isActive}
+                title={formatRange(range)}
+                onClick={() => review.pickPart(isActive ? null : range)}
+                className={cn(
+                  "rounded-md px-2 py-0.5 text-xs transition-colors",
+                  isActive
+                    ? "bg-primary/15 text-foreground"
+                    : "text-muted-foreground hover:bg-muted hover:text-foreground",
+                )}
+              >
+                {label}
+              </button>
+            );
+          })}
+        </span>
+      )}
     </div>
   );
 }