Apply selected-fg attrs on current line when item is selected

When an item is both current and selected, the current-line rendering
ignored selected-fg attrs entirely. e.g.

  echo foo | fzf --color fg:dim,nth:regular,current-fg:underline,selected-fg:italic --bind result:select --multi

The italic from selected-fg was lost. Merge NthSelectedAttr into the
overlay and rebuild colBase attr with the correct precedence chain:
fg < selected-fg < current-fg.

CHANGELOG.md

@@ -1,6 +1,14 @@
 CHANGELOG
 =========
 
+0.69.0
+------
+- Added `change-with-nth` action for dynamically changing the `--with-nth` option
+  ```sh
+  echo -e "a b c\nd e f\ng h i" | fzf --with-nth .. \
+    --bind 'space:change-with-nth(1|2|3|1,3|2,3|)'
+  ```
+
 0.68.0
 ------
 - Implemented word wrapping in the list section

man/man1/fzf.1

@@ -134,6 +134,14 @@ e.g.
      # Use template to rearrange fields
      echo foo,bar,baz | fzf --delimiter , --with-nth '{n},{1},{3},{2},{1..2}'
 .RE
+.RS
+
+\fBchange\-with\-nth\fR action is only available when \fB\-\-with\-nth\fR is set.
+When \fB\-\-with\-nth\fR is used, fzf retains the original input lines in memory
+so they can be re\-transformed on the fly (e.g. \fB\-\-with\-nth ..\fR to keep
+the original presentation). This increases memory usage, so only use
+\fB\-\-with\-nth\fR when you actually need field transformation.
+.RE
 .TP
 .BI "\-\-accept\-nth=" "N[,..] or TEMPLATE"
 Define which fields to print on accept. The last delimiter is stripped from the
@@ -1398,6 +1406,8 @@ fzf exports the following environment variables to its child processes.
 .br
 .BR FZF_NTH "             Current \-\-nth option"
 .br
+.BR FZF_WITH_NTH "        Current \-\-with\-nth option"
+.br
 .BR FZF_PROMPT "          Prompt string"
 .br
 .BR FZF_GHOST "           Ghost string"
@@ -1888,6 +1898,7 @@ A key or an event can be bound to one or more of the following actions.
     \fBchange\-multi\fR                 (enable multi-select mode with no limit)
     \fBchange\-multi(...)\fR            (enable multi-select mode with a limit or disable it with 0)
     \fBchange\-nth(...)\fR              (change \fB\-\-nth\fR option; rotate through the multiple options separated by '|')
+    \fBchange\-with\-nth(...)\fR         (change \fB\-\-with\-nth\fR option; rotate through the multiple options separated by '|')
     \fBchange\-pointer(...)\fR          (change \fB\-\-pointer\fR option)
     \fBchange\-preview(...)\fR          (change \fB\-\-preview\fR option)
     \fBchange\-preview\-label(...)\fR    (change \fB\-\-preview\-label\fR to the given string)
@@ -1993,6 +2004,7 @@ A key or an event can be bound to one or more of the following actions.
     \fBtransform\-input\-label(...)\fR   (transform input label using an external command)
     \fBtransform\-list\-label(...)\fR    (transform list label using an external command)
     \fBtransform\-nth(...)\fR           (transform nth using an external command)
+    \fBtransform\-with\-nth(...)\fR      (transform with-nth using an external command)
     \fBtransform\-pointer(...)\fR       (transform pointer using an external command)
     \fBtransform\-preview\-label(...)\fR (transform preview label using an external command)
     \fBtransform\-prompt(...)\fR        (transform prompt string using an external command)

src/actiontype_string.go

@@ -38,156 +38,159 @@ func _() {
 	_ = x[actChangeListLabel-27]
 	_ = x[actChangeMulti-28]
 	_ = x[actChangeNth-29]
-	_ = x[actChangePointer-30]
-	_ = x[actChangePreview-31]
-	_ = x[actChangePreviewLabel-32]
-	_ = x[actChangePreviewWindow-33]
-	_ = x[actChangePrompt-34]
-	_ = x[actChangeQuery-35]
-	_ = x[actClearScreen-36]
-	_ = x[actClearQuery-37]
-	_ = x[actClearSelection-38]
-	_ = x[actClose-39]
-	_ = x[actDeleteChar-40]
-	_ = x[actDeleteCharEof-41]
-	_ = x[actEndOfLine-42]
-	_ = x[actFatal-43]
-	_ = x[actForwardChar-44]
-	_ = x[actForwardWord-45]
-	_ = x[actForwardSubWord-46]
-	_ = x[actKillLine-47]
-	_ = x[actKillWord-48]
-	_ = x[actKillSubWord-49]
-	_ = x[actUnixLineDiscard-50]
-	_ = x[actUnixWordRubout-51]
-	_ = x[actYank-52]
-	_ = x[actBackwardKillWord-53]
-	_ = x[actBackwardKillSubWord-54]
-	_ = x[actSelectAll-55]
-	_ = x[actDeselectAll-56]
-	_ = x[actToggle-57]
-	_ = x[actToggleSearch-58]
-	_ = x[actToggleAll-59]
-	_ = x[actToggleDown-60]
-	_ = x[actToggleUp-61]
-	_ = x[actToggleIn-62]
-	_ = x[actToggleOut-63]
-	_ = x[actToggleTrack-64]
-	_ = x[actToggleTrackCurrent-65]
-	_ = x[actToggleHeader-66]
-	_ = x[actToggleWrap-67]
-	_ = x[actToggleWrapWord-68]
-	_ = x[actToggleMultiLine-69]
-	_ = x[actToggleHscroll-70]
-	_ = x[actToggleRaw-71]
-	_ = x[actEnableRaw-72]
-	_ = x[actDisableRaw-73]
-	_ = x[actTrackCurrent-74]
-	_ = x[actToggleInput-75]
-	_ = x[actHideInput-76]
-	_ = x[actShowInput-77]
-	_ = x[actUntrackCurrent-78]
-	_ = x[actDown-79]
-	_ = x[actDownMatch-80]
-	_ = x[actUp-81]
-	_ = x[actUpMatch-82]
-	_ = x[actPageUp-83]
-	_ = x[actPageDown-84]
-	_ = x[actPosition-85]
-	_ = x[actHalfPageUp-86]
-	_ = x[actHalfPageDown-87]
-	_ = x[actOffsetUp-88]
-	_ = x[actOffsetDown-89]
-	_ = x[actOffsetMiddle-90]
-	_ = x[actJump-91]
-	_ = x[actJumpAccept-92]
-	_ = x[actPrintQuery-93]
-	_ = x[actRefreshPreview-94]
-	_ = x[actReplaceQuery-95]
-	_ = x[actToggleSort-96]
-	_ = x[actShowPreview-97]
-	_ = x[actHidePreview-98]
-	_ = x[actTogglePreview-99]
-	_ = x[actTogglePreviewWrap-100]
-	_ = x[actTogglePreviewWrapWord-101]
-	_ = x[actTransform-102]
-	_ = x[actTransformBorderLabel-103]
-	_ = x[actTransformGhost-104]
-	_ = x[actTransformHeader-105]
-	_ = x[actTransformHeaderLines-106]
-	_ = x[actTransformFooter-107]
-	_ = x[actTransformHeaderLabel-108]
-	_ = x[actTransformFooterLabel-109]
-	_ = x[actTransformInputLabel-110]
-	_ = x[actTransformListLabel-111]
-	_ = x[actTransformNth-112]
-	_ = x[actTransformPointer-113]
-	_ = x[actTransformPreviewLabel-114]
-	_ = x[actTransformPrompt-115]
-	_ = x[actTransformQuery-116]
-	_ = x[actTransformSearch-117]
-	_ = x[actTrigger-118]
-	_ = x[actBgTransform-119]
-	_ = x[actBgTransformBorderLabel-120]
-	_ = x[actBgTransformGhost-121]
-	_ = x[actBgTransformHeader-122]
-	_ = x[actBgTransformHeaderLines-123]
-	_ = x[actBgTransformFooter-124]
-	_ = x[actBgTransformHeaderLabel-125]
-	_ = x[actBgTransformFooterLabel-126]
-	_ = x[actBgTransformInputLabel-127]
-	_ = x[actBgTransformListLabel-128]
-	_ = x[actBgTransformNth-129]
-	_ = x[actBgTransformPointer-130]
-	_ = x[actBgTransformPreviewLabel-131]
-	_ = x[actBgTransformPrompt-132]
-	_ = x[actBgTransformQuery-133]
-	_ = x[actBgTransformSearch-134]
-	_ = x[actBgCancel-135]
-	_ = x[actSearch-136]
-	_ = x[actPreview-137]
-	_ = x[actPreviewTop-138]
-	_ = x[actPreviewBottom-139]
-	_ = x[actPreviewUp-140]
-	_ = x[actPreviewDown-141]
-	_ = x[actPreviewPageUp-142]
-	_ = x[actPreviewPageDown-143]
-	_ = x[actPreviewHalfPageUp-144]
-	_ = x[actPreviewHalfPageDown-145]
-	_ = x[actPrevHistory-146]
-	_ = x[actPrevSelected-147]
-	_ = x[actPrint-148]
-	_ = x[actPut-149]
-	_ = x[actNextHistory-150]
-	_ = x[actNextSelected-151]
-	_ = x[actExecute-152]
-	_ = x[actExecuteSilent-153]
-	_ = x[actExecuteMulti-154]
-	_ = x[actSigStop-155]
-	_ = x[actBest-156]
-	_ = x[actFirst-157]
-	_ = x[actLast-158]
-	_ = x[actReload-159]
-	_ = x[actReloadSync-160]
-	_ = x[actDisableSearch-161]
-	_ = x[actEnableSearch-162]
-	_ = x[actSelect-163]
-	_ = x[actDeselect-164]
-	_ = x[actUnbind-165]
-	_ = x[actRebind-166]
-	_ = x[actToggleBind-167]
-	_ = x[actBecome-168]
-	_ = x[actShowHeader-169]
-	_ = x[actHideHeader-170]
-	_ = x[actBell-171]
-	_ = x[actExclude-172]
-	_ = x[actExcludeMulti-173]
-	_ = x[actAsync-174]
+	_ = x[actChangeWithNth-30]
+	_ = x[actChangePointer-31]
+	_ = x[actChangePreview-32]
+	_ = x[actChangePreviewLabel-33]
+	_ = x[actChangePreviewWindow-34]
+	_ = x[actChangePrompt-35]
+	_ = x[actChangeQuery-36]
+	_ = x[actClearScreen-37]
+	_ = x[actClearQuery-38]
+	_ = x[actClearSelection-39]
+	_ = x[actClose-40]
+	_ = x[actDeleteChar-41]
+	_ = x[actDeleteCharEof-42]
+	_ = x[actEndOfLine-43]
+	_ = x[actFatal-44]
+	_ = x[actForwardChar-45]
+	_ = x[actForwardWord-46]
+	_ = x[actForwardSubWord-47]
+	_ = x[actKillLine-48]
+	_ = x[actKillWord-49]
+	_ = x[actKillSubWord-50]
+	_ = x[actUnixLineDiscard-51]
+	_ = x[actUnixWordRubout-52]
+	_ = x[actYank-53]
+	_ = x[actBackwardKillWord-54]
+	_ = x[actBackwardKillSubWord-55]
+	_ = x[actSelectAll-56]
+	_ = x[actDeselectAll-57]
+	_ = x[actToggle-58]
+	_ = x[actToggleSearch-59]
+	_ = x[actToggleAll-60]
+	_ = x[actToggleDown-61]
+	_ = x[actToggleUp-62]
+	_ = x[actToggleIn-63]
+	_ = x[actToggleOut-64]
+	_ = x[actToggleTrack-65]
+	_ = x[actToggleTrackCurrent-66]
+	_ = x[actToggleHeader-67]
+	_ = x[actToggleWrap-68]
+	_ = x[actToggleWrapWord-69]
+	_ = x[actToggleMultiLine-70]
+	_ = x[actToggleHscroll-71]
+	_ = x[actToggleRaw-72]
+	_ = x[actEnableRaw-73]
+	_ = x[actDisableRaw-74]
+	_ = x[actTrackCurrent-75]
+	_ = x[actToggleInput-76]
+	_ = x[actHideInput-77]
+	_ = x[actShowInput-78]
+	_ = x[actUntrackCurrent-79]
+	_ = x[actDown-80]
+	_ = x[actDownMatch-81]
+	_ = x[actUp-82]
+	_ = x[actUpMatch-83]
+	_ = x[actPageUp-84]
+	_ = x[actPageDown-85]
+	_ = x[actPosition-86]
+	_ = x[actHalfPageUp-87]
+	_ = x[actHalfPageDown-88]
+	_ = x[actOffsetUp-89]
+	_ = x[actOffsetDown-90]
+	_ = x[actOffsetMiddle-91]
+	_ = x[actJump-92]
+	_ = x[actJumpAccept-93]
+	_ = x[actPrintQuery-94]
+	_ = x[actRefreshPreview-95]
+	_ = x[actReplaceQuery-96]
+	_ = x[actToggleSort-97]
+	_ = x[actShowPreview-98]
+	_ = x[actHidePreview-99]
+	_ = x[actTogglePreview-100]
+	_ = x[actTogglePreviewWrap-101]
+	_ = x[actTogglePreviewWrapWord-102]
+	_ = x[actTransform-103]
+	_ = x[actTransformBorderLabel-104]
+	_ = x[actTransformGhost-105]
+	_ = x[actTransformHeader-106]
+	_ = x[actTransformHeaderLines-107]
+	_ = x[actTransformFooter-108]
+	_ = x[actTransformHeaderLabel-109]
+	_ = x[actTransformFooterLabel-110]
+	_ = x[actTransformInputLabel-111]
+	_ = x[actTransformListLabel-112]
+	_ = x[actTransformNth-113]
+	_ = x[actTransformWithNth-114]
+	_ = x[actTransformPointer-115]
+	_ = x[actTransformPreviewLabel-116]
+	_ = x[actTransformPrompt-117]
+	_ = x[actTransformQuery-118]
+	_ = x[actTransformSearch-119]
+	_ = x[actTrigger-120]
+	_ = x[actBgTransform-121]
+	_ = x[actBgTransformBorderLabel-122]
+	_ = x[actBgTransformGhost-123]
+	_ = x[actBgTransformHeader-124]
+	_ = x[actBgTransformHeaderLines-125]
+	_ = x[actBgTransformFooter-126]
+	_ = x[actBgTransformHeaderLabel-127]
+	_ = x[actBgTransformFooterLabel-128]
+	_ = x[actBgTransformInputLabel-129]
+	_ = x[actBgTransformListLabel-130]
+	_ = x[actBgTransformNth-131]
+	_ = x[actBgTransformWithNth-132]
+	_ = x[actBgTransformPointer-133]
+	_ = x[actBgTransformPreviewLabel-134]
+	_ = x[actBgTransformPrompt-135]
+	_ = x[actBgTransformQuery-136]
+	_ = x[actBgTransformSearch-137]
+	_ = x[actBgCancel-138]
+	_ = x[actSearch-139]
+	_ = x[actPreview-140]
+	_ = x[actPreviewTop-141]
+	_ = x[actPreviewBottom-142]
+	_ = x[actPreviewUp-143]
+	_ = x[actPreviewDown-144]
+	_ = x[actPreviewPageUp-145]
+	_ = x[actPreviewPageDown-146]
+	_ = x[actPreviewHalfPageUp-147]
+	_ = x[actPreviewHalfPageDown-148]
+	_ = x[actPrevHistory-149]
+	_ = x[actPrevSelected-150]
+	_ = x[actPrint-151]
+	_ = x[actPut-152]
+	_ = x[actNextHistory-153]
+	_ = x[actNextSelected-154]
+	_ = x[actExecute-155]
+	_ = x[actExecuteSilent-156]
+	_ = x[actExecuteMulti-157]
+	_ = x[actSigStop-158]
+	_ = x[actBest-159]
+	_ = x[actFirst-160]
+	_ = x[actLast-161]
+	_ = x[actReload-162]
+	_ = x[actReloadSync-163]
+	_ = x[actDisableSearch-164]
+	_ = x[actEnableSearch-165]
+	_ = x[actSelect-166]
+	_ = x[actDeselect-167]
+	_ = x[actUnbind-168]
+	_ = x[actRebind-169]
+	_ = x[actToggleBind-170]
+	_ = x[actBecome-171]
+	_ = x[actShowHeader-172]
+	_ = x[actHideHeader-173]
+	_ = x[actBell-174]
+	_ = x[actExclude-175]
+	_ = x[actExcludeMulti-176]
+	_ = x[actAsync-177]
 }
 
-const _actionType_name = "actIgnoreactStartactClickactInvalidactBracketedPasteBeginactBracketedPasteEndactCharactMouseactBeginningOfLineactAbortactAcceptactAcceptNonEmptyactAcceptOrPrintQueryactBackwardCharactBackwardDeleteCharactBackwardDeleteCharEofactBackwardWordactBackwardSubWordactCancelactChangeBorderLabelactChangeGhostactChangeHeaderactChangeHeaderLinesactChangeFooteractChangeHeaderLabelactChangeFooterLabelactChangeInputLabelactChangeListLabelactChangeMultiactChangeNthactChangePointeractChangePreviewactChangePreviewLabelactChangePreviewWindowactChangePromptactChangeQueryactClearScreenactClearQueryactClearSelectionactCloseactDeleteCharactDeleteCharEofactEndOfLineactFatalactForwardCharactForwardWordactForwardSubWordactKillLineactKillWordactKillSubWordactUnixLineDiscardactUnixWordRuboutactYankactBackwardKillWordactBackwardKillSubWordactSelectAllactDeselectAllactToggleactToggleSearchactToggleAllactToggleDownactToggleUpactToggleInactToggleOutactToggleTrackactToggleTrackCurrentactToggleHeaderactToggleWrapactToggleWrapWordactToggleMultiLineactToggleHscrollactToggleRawactEnableRawactDisableRawactTrackCurrentactToggleInputactHideInputactShowInputactUntrackCurrentactDownactDownMatchactUpactUpMatchactPageUpactPageDownactPositionactHalfPageUpactHalfPageDownactOffsetUpactOffsetDownactOffsetMiddleactJumpactJumpAcceptactPrintQueryactRefreshPreviewactReplaceQueryactToggleSortactShowPreviewactHidePreviewactTogglePreviewactTogglePreviewWrapactTogglePreviewWrapWordactTransformactTransformBorderLabelactTransformGhostactTransformHeaderactTransformHeaderLinesactTransformFooteractTransformHeaderLabelactTransformFooterLabelactTransformInputLabelactTransformListLabelactTransformNthactTransformPointeractTransformPreviewLabelactTransformPromptactTransformQueryactTransformSearchactTriggeractBgTransformactBgTransformBorderLabelactBgTransformGhostactBgTransformHeaderactBgTransformHeaderLinesactBgTransformFooteractBgTransformHeaderLabelactBgTransformFooterLabelactBgTransformInputLabelactBgTransformListLabelactBgTransformNthactBgTransformPointeractBgTransformPreviewLabelactBgTransformPromptactBgTransformQueryactBgTransformSearchactBgCancelactSearchactPreviewactPreviewTopactPreviewBottomactPreviewUpactPreviewDownactPreviewPageUpactPreviewPageDownactPreviewHalfPageUpactPreviewHalfPageDownactPrevHistoryactPrevSelectedactPrintactPutactNextHistoryactNextSelectedactExecuteactExecuteSilentactExecuteMultiactSigStopactBestactFirstactLastactReloadactReloadSyncactDisableSearchactEnableSearchactSelectactDeselectactUnbindactRebindactToggleBindactBecomeactShowHeaderactHideHeaderactBellactExcludeactExcludeMultiactAsync"
+const _actionType_name = "actIgnoreactStartactClickactInvalidactBracketedPasteBeginactBracketedPasteEndactCharactMouseactBeginningOfLineactAbortactAcceptactAcceptNonEmptyactAcceptOrPrintQueryactBackwardCharactBackwardDeleteCharactBackwardDeleteCharEofactBackwardWordactBackwardSubWordactCancelactChangeBorderLabelactChangeGhostactChangeHeaderactChangeHeaderLinesactChangeFooteractChangeHeaderLabelactChangeFooterLabelactChangeInputLabelactChangeListLabelactChangeMultiactChangeNthactChangeWithNthactChangePointeractChangePreviewactChangePreviewLabelactChangePreviewWindowactChangePromptactChangeQueryactClearScreenactClearQueryactClearSelectionactCloseactDeleteCharactDeleteCharEofactEndOfLineactFatalactForwardCharactForwardWordactForwardSubWordactKillLineactKillWordactKillSubWordactUnixLineDiscardactUnixWordRuboutactYankactBackwardKillWordactBackwardKillSubWordactSelectAllactDeselectAllactToggleactToggleSearchactToggleAllactToggleDownactToggleUpactToggleInactToggleOutactToggleTrackactToggleTrackCurrentactToggleHeaderactToggleWrapactToggleWrapWordactToggleMultiLineactToggleHscrollactToggleRawactEnableRawactDisableRawactTrackCurrentactToggleInputactHideInputactShowInputactUntrackCurrentactDownactDownMatchactUpactUpMatchactPageUpactPageDownactPositionactHalfPageUpactHalfPageDownactOffsetUpactOffsetDownactOffsetMiddleactJumpactJumpAcceptactPrintQueryactRefreshPreviewactReplaceQueryactToggleSortactShowPreviewactHidePreviewactTogglePreviewactTogglePreviewWrapactTogglePreviewWrapWordactTransformactTransformBorderLabelactTransformGhostactTransformHeaderactTransformHeaderLinesactTransformFooteractTransformHeaderLabelactTransformFooterLabelactTransformInputLabelactTransformListLabelactTransformNthactTransformWithNthactTransformPointeractTransformPreviewLabelactTransformPromptactTransformQueryactTransformSearchactTriggeractBgTransformactBgTransformBorderLabelactBgTransformGhostactBgTransformHeaderactBgTransformHeaderLinesactBgTransformFooteractBgTransformHeaderLabelactBgTransformFooterLabelactBgTransformInputLabelactBgTransformListLabelactBgTransformNthactBgTransformWithNthactBgTransformPointeractBgTransformPreviewLabelactBgTransformPromptactBgTransformQueryactBgTransformSearchactBgCancelactSearchactPreviewactPreviewTopactPreviewBottomactPreviewUpactPreviewDownactPreviewPageUpactPreviewPageDownactPreviewHalfPageUpactPreviewHalfPageDownactPrevHistoryactPrevSelectedactPrintactPutactNextHistoryactNextSelectedactExecuteactExecuteSilentactExecuteMultiactSigStopactBestactFirstactLastactReloadactReloadSyncactDisableSearchactEnableSearchactSelectactDeselectactUnbindactRebindactToggleBindactBecomeactShowHeaderactHideHeaderactBellactExcludeactExcludeMultiactAsync"
 
-var _actionType_index = [...]uint16{0, 9, 17, 25, 35, 57, 77, 84, 92, 110, 118, 127, 144, 165, 180, 201, 225, 240, 258, 267, 287, 301, 316, 336, 351, 371, 391, 410, 428, 442, 454, 470, 486, 507, 529, 544, 558, 572, 585, 602, 610, 623, 639, 651, 659, 673, 687, 704, 715, 726, 740, 758, 775, 782, 801, 823, 835, 849, 858, 873, 885, 898, 909, 920, 932, 946, 967, 982, 995, 1012, 1030, 1046, 1058, 1070, 1083, 1098, 1112, 1124, 1136, 1153, 1160, 1172, 1177, 1187, 1196, 1207, 1218, 1231, 1246, 1257, 1270, 1285, 1292, 1305, 1318, 1335, 1350, 1363, 1377, 1391, 1407, 1427, 1451, 1463, 1486, 1503, 1521, 1544, 1562, 1585, 1608, 1630, 1651, 1666, 1685, 1709, 1727, 1744, 1762, 1772, 1786, 1811, 1830, 1850, 1875, 1895, 1920, 1945, 1969, 1992, 2009, 2030, 2056, 2076, 2095, 2115, 2126, 2135, 2145, 2158, 2174, 2186, 2200, 2216, 2234, 2254, 2276, 2290, 2305, 2313, 2319, 2333, 2348, 2358, 2374, 2389, 2399, 2406, 2414, 2421, 2430, 2443, 2459, 2474, 2483, 2494, 2503, 2512, 2525, 2534, 2547, 2560, 2567, 2577, 2592, 2600}
+var _actionType_index = [...]uint16{0, 9, 17, 25, 35, 57, 77, 84, 92, 110, 118, 127, 144, 165, 180, 201, 225, 240, 258, 267, 287, 301, 316, 336, 351, 371, 391, 410, 428, 442, 454, 470, 486, 502, 523, 545, 560, 574, 588, 601, 618, 626, 639, 655, 667, 675, 689, 703, 720, 731, 742, 756, 774, 791, 798, 817, 839, 851, 865, 874, 889, 901, 914, 925, 936, 948, 962, 983, 998, 1011, 1028, 1046, 1062, 1074, 1086, 1099, 1114, 1128, 1140, 1152, 1169, 1176, 1188, 1193, 1203, 1212, 1223, 1234, 1247, 1262, 1273, 1286, 1301, 1308, 1321, 1334, 1351, 1366, 1379, 1393, 1407, 1423, 1443, 1467, 1479, 1502, 1519, 1537, 1560, 1578, 1601, 1624, 1646, 1667, 1682, 1701, 1720, 1744, 1762, 1779, 1797, 1807, 1821, 1846, 1865, 1885, 1910, 1930, 1955, 1980, 2004, 2027, 2044, 2065, 2086, 2112, 2132, 2151, 2171, 2182, 2191, 2201, 2214, 2230, 2242, 2256, 2272, 2290, 2310, 2332, 2346, 2361, 2369, 2375, 2389, 2404, 2414, 2430, 2445, 2455, 2462, 2470, 2477, 2486, 2499, 2515, 2530, 2539, 2550, 2559, 2568, 2581, 2590, 2603, 2616, 2623, 2633, 2648, 2656}
 
 func (i actionType) String() string {
 	if i < 0 || i >= actionType(len(_actionType_index)-1) {

src/chunklist.go

@@ -99,6 +99,21 @@ func (cl *ChunkList) Clear() {
 	cl.mutex.Unlock()
 }
 
+// ForEachItem iterates all items and applies fn to each one.
+// The done callback runs under the lock to safely update shared state.
+func (cl *ChunkList) ForEachItem(fn func(*Item), done func()) {
+	cl.mutex.Lock()
+	for _, chunk := range cl.chunks {
+		for i := 0; i < chunk.count; i++ {
+			fn(&chunk.items[i])
+		}
+	}
+	if done != nil {
+		done()
+	}
+	cl.mutex.Unlock()
+}
+
 // Snapshot returns immutable snapshot of the ChunkList
 func (cl *ChunkList) Snapshot(tail int) ([]*Chunk, int, bool) {
 	cl.mutex.Lock()

src/core.go

@@ -113,16 +113,9 @@ func Run(opts *Options) (int, error) {
 	cache := NewChunkCache()
 	var chunkList *ChunkList
 	var itemIndex int32
-	if opts.WithNth == nil {
-		chunkList = NewChunkList(cache, func(item *Item, data []byte) bool {
-			item.text, item.colors = ansiProcessor(data)
-			item.text.Index = itemIndex
-			itemIndex++
-			return true
-		})
-	} else {
-		nthTransformer := opts.WithNth(opts.Delimiter)
-		chunkList = NewChunkList(cache, func(item *Item, data []byte) bool {
+	// transformItem applies with-nth transformation to an item's raw data.
+	// It handles ANSI token propagation using prevLineAnsiState for cross-line continuity.
+	transformItem := func(item *Item, data []byte, transformer func([]Token, int32) string, index int32) {
 		tokens := Tokenize(byteString(data), opts.Delimiter)
 		if opts.Ansi && len(tokens) > 1 {
 			var ansiState *ansiState
@@ -140,7 +133,7 @@ func Run(opts *Options) (int, error) {
 				}
 			}
 		}
-			transformed := nthTransformer(tokens, itemIndex)
+		transformed := transformer(tokens, index)
 		item.text, item.colors = ansiProcessor(stringBytes(transformed))
 
 		// We should not trim trailing whitespaces with background colors
@@ -153,6 +146,24 @@ func Run(opts *Options) (int, error) {
 			}
 		}
 		item.text.TrimTrailingWhitespaces(int(maxColorOffset))
+	}
+
+	var nthTransformer func([]Token, int32) string
+	if opts.WithNth == nil {
+		chunkList = NewChunkList(cache, func(item *Item, data []byte) bool {
+			item.text, item.colors = ansiProcessor(data)
+			item.text.Index = itemIndex
+			itemIndex++
+			return true
+		})
+	} else {
+		nthTransformer = opts.WithNth(opts.Delimiter)
+		chunkList = NewChunkList(cache, func(item *Item, data []byte) bool {
+			if nthTransformer == nil {
+				item.text, item.colors = ansiProcessor(data)
+			} else {
+				transformItem(item, data, nthTransformer, itemIndex)
+			}
 			item.text.Index = itemIndex
 			item.origText = &data
 			itemIndex++
@@ -260,7 +271,7 @@ func Run(opts *Options) (int, error) {
 							return false
 						}
 						mutex.Lock()
-						if result, _, _ := pattern.MatchItem(&item, false, slab); result != nil {
+						if result, _, _ := pattern.MatchItem(&item, false, slab); result.item != nil {
 							opts.Printer(transformer(&item))
 							found = true
 						}
@@ -461,6 +472,7 @@ func Run(opts *Options) (int, error) {
 					var environ []string
 					var changed bool
 					headerLinesChanged := false
+					withNthChanged := false
 					switch val := value.(type) {
 					case searchRequest:
 						sort = val.sort
@@ -487,6 +499,34 @@ func Run(opts *Options) (int, error) {
 							headerLinesChanged = true
 							bump = true
 						}
+						if val.withNth != nil {
+							newTransformer := val.withNth.fn
+							// Cancel any in-flight scan and block the terminal from reading
+							// items before mutating them in-place. Snapshot shares middle
+							// chunk pointers, so the matcher and terminal can race with us.
+							matcher.CancelScan()
+							terminal.PauseRendering()
+							// Reset cross-line ANSI state before re-processing all items
+							lineAnsiState = nil
+							prevLineAnsiState = nil
+							chunkList.ForEachItem(func(item *Item) {
+								origBytes := *item.origText
+								savedIndex := item.Index()
+								if newTransformer != nil {
+									transformItem(item, origBytes, newTransformer, savedIndex)
+								} else {
+									item.text, item.colors = ansiProcessor(origBytes)
+								}
+								item.text.Index = savedIndex
+								item.transformed = nil
+							}, func() {
+								nthTransformer = newTransformer
+							})
+							terminal.ResumeRendering()
+							matcher.ResumeScan()
+							withNthChanged = true
+							bump = true
+						}
 						if bump {
 							patternCache = make(map[string]*Pattern)
 							cache.Clear()
@@ -530,6 +570,8 @@ func Run(opts *Options) (int, error) {
 						} else {
 							terminal.UpdateHeader(nil)
 						}
+					} else if withNthChanged && headerLines > 0 {
+						terminal.UpdateHeader(GetItems(snapshot, int(headerLines)))
 					}
 					matcher.Reset(snapshot, input(), true, !reading, sort, snapshotRevision)
 					delay = false

src/matcher.go

@@ -3,7 +3,6 @@ package fzf
 import (
 	"fmt"
 	"runtime"
-	"sort"
 	"sync"
 	"time"
 
@@ -43,8 +42,11 @@ type Matcher struct {
 	reqBox         *util.EventBox
 	partitions     int
 	slab           []*util.Slab
+	sortBuf        [][]Result
 	mergerCache    map[string]MatchResult
 	revision       revision
+	scanMutex      sync.Mutex
+	cancelScan     *util.AtomicBool
 }
 
 const (
@@ -68,8 +70,10 @@ func NewMatcher(cache *ChunkCache, patternBuilder func([]rune) *Pattern,
 		reqBox:         util.NewEventBox(),
 		partitions:     partitions,
 		slab:           make([]*util.Slab, partitions),
+		sortBuf:        make([][]Result, partitions),
 		mergerCache:    make(map[string]MatchResult),
-		revision:       revision}
+		revision:       revision,
+		cancelScan:     util.NewAtomicBool(false)}
 }
 
 // Loop puts Matcher in action
@@ -129,7 +133,9 @@ func (m *Matcher) Loop() {
 		}
 
 		if result.merger == nil {
+			m.scanMutex.Lock()
 			result = m.scan(request)
+			m.scanMutex.Unlock()
 		}
 
 		if !result.cancelled {
@@ -215,11 +221,7 @@ func (m *Matcher) scan(request MatchRequest) MatchResult {
 				sliceMatches = append(sliceMatches, matches...)
 			}
 			if m.sort && request.pattern.sortable {
-				if m.tac {
-					sort.Sort(ByRelevanceTac(sliceMatches))
-				} else {
-					sort.Sort(ByRelevance(sliceMatches))
-				}
+				m.sortBuf[idx] = radixSortResults(sliceMatches, m.tac, m.sortBuf[idx])
 			}
 			resultChan <- partialResult{idx, sliceMatches}
 		}(idx, m.slab[idx], chunks)
@@ -241,7 +243,7 @@ func (m *Matcher) scan(request MatchRequest) MatchResult {
 			break
 		}
 
-		if m.reqBox.Peek(reqReset) {
+		if m.cancelScan.Get() || m.reqBox.Peek(reqReset) {
 			return MatchResult{nil, nil, wait()}
 		}
 
@@ -272,6 +274,20 @@ func (m *Matcher) Reset(chunks []*Chunk, patternRunes []rune, cancel bool, final
 	m.reqBox.Set(event, MatchRequest{chunks, pattern, final, sort, revision})
 }
 
+// CancelScan cancels any in-flight scan, waits for it to finish,
+// and prevents new scans from starting until ResumeScan is called.
+// This is used to safely mutate shared items (e.g., during with-nth changes).
+func (m *Matcher) CancelScan() {
+	m.cancelScan.Set(true)
+	m.scanMutex.Lock()
+	m.cancelScan.Set(false)
+}
+
+// ResumeScan allows scans to proceed again after CancelScan.
+func (m *Matcher) ResumeScan() {
+	m.scanMutex.Unlock()
+}
+
 func (m *Matcher) Stop() {
 	m.reqBox.Set(reqQuit, nil)
 }

src/options.go

@@ -588,6 +588,7 @@ type Options struct {
 	FreezeLeft        int
 	FreezeRight       int
 	WithNth           func(Delimiter) func([]Token, int32) string
+	WithNthExpr       string
 	AcceptNth         func(Delimiter) func([]Token, int32) string
 	Delimiter         Delimiter
 	Sort              int
@@ -1629,7 +1630,7 @@ const (
 
 func init() {
 	executeRegexp = regexp.MustCompile(
-		`(?si)[:+](become|execute(?:-multi|-silent)?|reload(?:-sync)?|preview|(?:change|bg-transform|transform)-(?:query|prompt|(?:border|list|preview|input|header|footer)-label|header-lines|header|footer|search|nth|pointer|ghost)|bg-transform|transform|change-(?:preview-window|preview|multi)|(?:re|un|toggle-)bind|pos|put|print|search|trigger)`)
+		`(?si)[:+](become|execute(?:-multi|-silent)?|reload(?:-sync)?|preview|(?:change|bg-transform|transform)-(?:query|prompt|(?:border|list|preview|input|header|footer)-label|header-lines|header|footer|search|with-nth|nth|pointer|ghost)|bg-transform|transform|change-(?:preview-window|preview|multi)|(?:re|un|toggle-)bind|pos|put|print|search|trigger)`)
 	splitRegexp = regexp.MustCompile("[,:]+")
 	actionNameRegexp = regexp.MustCompile("(?i)^[a-z-]+")
 }
@@ -2072,6 +2073,8 @@ func isExecuteAction(str string) actionType {
 		return actChangeMulti
 	case "change-nth":
 		return actChangeNth
+	case "change-with-nth":
+		return actChangeWithNth
 	case "pos":
 		return actPosition
 	case "execute":
@@ -2108,6 +2111,8 @@ func isExecuteAction(str string) actionType {
 		return actTransformGhost
 	case "transform-nth":
 		return actTransformNth
+	case "transform-with-nth":
+		return actTransformWithNth
 	case "transform-pointer":
 		return actTransformPointer
 	case "transform-prompt":
@@ -2140,6 +2145,8 @@ func isExecuteAction(str string) actionType {
 		return actBgTransformGhost
 	case "bg-transform-nth":
 		return actBgTransformNth
+	case "bg-transform-with-nth":
+		return actBgTransformWithNth
 	case "bg-transform-pointer":
 		return actBgTransformPointer
 	case "bg-transform-prompt":
@@ -2781,6 +2788,7 @@ func parseOptions(index *int, opts *Options, allArgs []string) error {
 			if opts.WithNth, err = nthTransformer(str); err != nil {
 				return err
 			}
+			opts.WithNthExpr = str
 		case "--accept-nth":
 			str, err := nextString("nth expression required")
 			if err != nil {

src/pattern.go

@@ -65,6 +65,8 @@ type Pattern struct {
 	cache         *ChunkCache
 	denylist      map[int32]struct{}
 	startIndex    int32
+	directAlgo    algo.Algo
+	directTerm    *term
 }
 
 var _splitRegex *regexp.Regexp
@@ -151,6 +153,7 @@ func BuildPattern(cache *ChunkCache, patternCache map[string]*Pattern, fuzzy boo
 		procFun:       make(map[termType]algo.Algo)}
 
 	ptr.cacheKey = ptr.buildCacheKey()
+	ptr.directAlgo, ptr.directTerm = ptr.buildDirectAlgo(fuzzyAlgo)
 	ptr.procFun[termFuzzy] = fuzzyAlgo
 	ptr.procFun[termEqual] = algo.EqualMatch
 	ptr.procFun[termExact] = algo.ExactMatchNaive
@@ -274,6 +277,22 @@ func (p *Pattern) buildCacheKey() string {
 	return strings.Join(cacheableTerms, "\t")
 }
 
+// buildDirectAlgo returns the algo function and term for the direct fast path
+// in matchChunk. Returns (nil, nil) if the pattern is not suitable.
+// Requirements: extended mode, single term set with single non-inverse fuzzy term, no nth.
+func (p *Pattern) buildDirectAlgo(fuzzyAlgo algo.Algo) (algo.Algo, *term) {
+	if !p.extended || len(p.nth) > 0 {
+		return nil, nil
+	}
+	if len(p.termSets) == 1 && len(p.termSets[0]) == 1 {
+		t := &p.termSets[0][0]
+		if !t.inv && t.typ == termFuzzy {
+			return fuzzyAlgo, t
+		}
+	}
+	return nil, nil
+}
+
 // CacheKey is used to build string to be used as the key of result cache
 func (p *Pattern) CacheKey() string {
 	return p.cacheKey
@@ -312,18 +331,47 @@ func (p *Pattern) matchChunk(chunk *Chunk, space []Result, slab *util.Slab) []Re
 		}
 	}
 
-	if len(p.denylist) == 0 {
-		// Huge code duplication for minimizing unnecessary map lookups
+	// Fast path: single fuzzy term, no nth, no denylist.
+	// Calls the algo function directly, bypassing MatchItem/extendedMatch/iter
+	// and avoiding per-match []Offset heap allocation.
+	if p.directAlgo != nil && len(p.denylist) == 0 {
+		t := p.directTerm
 		if space == nil {
 			for idx := startIdx; idx < chunk.count; idx++ {
-				if match, _, _ := p.MatchItem(&chunk.items[idx], p.withPos, slab); match != nil {
-					matches = append(matches, *match)
+				res, _ := p.directAlgo(t.caseSensitive, t.normalize, p.forward,
+					&chunk.items[idx].text, t.text, p.withPos, slab)
+				if res.Start >= 0 {
+					matches = append(matches, buildResultFromBounds(
+						&chunk.items[idx], res.Score,
+						int(res.Start), int(res.End), int(res.End), true))
 				}
 			}
 		} else {
 			for _, result := range space {
-				if match, _, _ := p.MatchItem(result.item, p.withPos, slab); match != nil {
-					matches = append(matches, *match)
+				res, _ := p.directAlgo(t.caseSensitive, t.normalize, p.forward,
+					&result.item.text, t.text, p.withPos, slab)
+				if res.Start >= 0 {
+					matches = append(matches, buildResultFromBounds(
+						result.item, res.Score,
+						int(res.Start), int(res.End), int(res.End), true))
+				}
+			}
+		}
+		return matches
+	}
+
+	if len(p.denylist) == 0 {
+		// Huge code duplication for minimizing unnecessary map lookups
+		if space == nil {
+			for idx := startIdx; idx < chunk.count; idx++ {
+				if match, _, _ := p.MatchItem(&chunk.items[idx], p.withPos, slab); match.item != nil {
+					matches = append(matches, match)
+				}
+			}
+		} else {
+			for _, result := range space {
+				if match, _, _ := p.MatchItem(result.item, p.withPos, slab); match.item != nil {
+					matches = append(matches, match)
 				}
 			}
 		}
@@ -335,8 +383,8 @@ func (p *Pattern) matchChunk(chunk *Chunk, space []Result, slab *util.Slab) []Re
 			if _, prs := p.denylist[chunk.items[idx].Index()]; prs {
 				continue
 			}
-			if match, _, _ := p.MatchItem(&chunk.items[idx], p.withPos, slab); match != nil {
-				matches = append(matches, *match)
+			if match, _, _ := p.MatchItem(&chunk.items[idx], p.withPos, slab); match.item != nil {
+				matches = append(matches, match)
 			}
 		}
 	} else {
@@ -344,30 +392,29 @@ func (p *Pattern) matchChunk(chunk *Chunk, space []Result, slab *util.Slab) []Re
 			if _, prs := p.denylist[result.item.Index()]; prs {
 				continue
 			}
-			if match, _, _ := p.MatchItem(result.item, p.withPos, slab); match != nil {
-				matches = append(matches, *match)
+			if match, _, _ := p.MatchItem(result.item, p.withPos, slab); match.item != nil {
+				matches = append(matches, match)
 			}
 		}
 	}
 	return matches
 }
 
-// MatchItem returns true if the Item is a match
-func (p *Pattern) MatchItem(item *Item, withPos bool, slab *util.Slab) (*Result, []Offset, *[]int) {
+// MatchItem returns the match result if the Item is a match.
+// A zero-value Result (with item == nil) indicates no match.
+func (p *Pattern) MatchItem(item *Item, withPos bool, slab *util.Slab) (Result, []Offset, *[]int) {
 	if p.extended {
 		if offsets, bonus, pos := p.extendedMatch(item, withPos, slab); len(offsets) == len(p.termSets) {
-			result := buildResult(item, offsets, bonus)
-			return &result, offsets, pos
+			return buildResult(item, offsets, bonus), offsets, pos
 		}
-		return nil, nil, nil
+		return Result{}, nil, nil
 	}
 	offset, bonus, pos := p.basicMatch(item, withPos, slab)
 	if sidx := offset[0]; sidx >= 0 {
 		offsets := []Offset{offset}
-		result := buildResult(item, offsets, bonus)
-		return &result, offsets, pos
+		return buildResult(item, offsets, bonus), offsets, pos
 	}
-	return nil, nil, nil
+	return Result{}, nil, nil
 }
 
 func (p *Pattern) basicMatch(item *Item, withPos bool, slab *util.Slab) (Offset, int, *[]int) {

src/result.go

@@ -33,8 +33,6 @@ func buildResult(item *Item, offsets []Offset, score int) Result {
 		sort.Sort(ByOrder(offsets))
 	}
 
-	result := Result{item: item}
-	numChars := item.text.Length()
 	minBegin := math.MaxUint16
 	minEnd := math.MaxUint16
 	maxEnd := 0
@@ -49,6 +47,14 @@ func buildResult(item *Item, offsets []Offset, score int) Result {
 		}
 	}
 
+	return buildResultFromBounds(item, score, minBegin, minEnd, maxEnd, validOffsetFound)
+}
+
+// buildResultFromBounds builds a Result from pre-computed offset bounds.
+func buildResultFromBounds(item *Item, score int, minBegin, minEnd, maxEnd int, validOffsetFound bool) Result {
+	result := Result{item: item}
+	numChars := item.text.Length()
+
 	for idx, criterion := range sortCriteria {
 		val := uint16(math.MaxUint16)
 		switch criterion {
@@ -75,7 +81,6 @@ func buildResult(item *Item, offsets []Offset, score int) Result {
 			val = item.TrimLength()
 		case byPathname:
 			if validOffsetFound {
-				// lastDelim := strings.LastIndexByte(item.text.ToString(), '/')
 				lastDelim := -1
 				s := item.text.ToString()
 				for i := len(s) - 1; i >= 0; i-- {
@@ -123,7 +128,7 @@ func minRank() Result {
 	return Result{item: &minItem, points: [4]uint16{math.MaxUint16, 0, 0, 0}}
 }
 
-func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, theme *tui.ColorTheme, colBase tui.ColorPair, colMatch tui.ColorPair, attrNth tui.Attr, hidden bool) []colorOffset {
+func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, theme *tui.ColorTheme, colBase tui.ColorPair, colMatch tui.ColorPair, attrNth tui.Attr, nthOverlay tui.Attr, hidden bool) []colorOffset {
 	itemColors := result.item.Colors()
 
 	// No ANSI codes
@@ -208,6 +213,10 @@ func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, t
 		}
 		return tui.NewColorPair(fg, bg, ansi.color.attr).WithUl(ansi.color.ul).MergeAttr(base)
 	}
+	fgAttr := tui.ColNormal.Attr()
+	nthAttrFinal := fgAttr.Merge(attrNth).Merge(nthOverlay)
+	nthBase := colBase.WithNewAttr(nthAttrFinal)
+
 	var colors []colorOffset
 	add := func(idx int) {
 		if curr.fbg >= 0 {
@@ -221,7 +230,7 @@ func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, t
 			if curr.match {
 				var color tui.ColorPair
 				if curr.nth {
-					color = colBase.WithAttr(attrNth).Merge(colMatch)
+					color = nthBase.Merge(colMatch)
 				} else {
 					color = colBase.Merge(colMatch)
 				}
@@ -241,7 +250,7 @@ func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, t
 					if color.Fg().IsDefault() && origColor.HasBg() {
 						color = origColor
 						if curr.nth {
-							color = color.WithAttr(attrNth &^ tui.AttrRegular)
+							color = color.WithAttr((attrNth &^ tui.AttrRegular).Merge(nthOverlay))
 						}
 					} else {
 						color = origColor.MergeNonDefault(color)
@@ -253,7 +262,7 @@ func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, t
 				ansi := itemColors[curr.index]
 				base := colBase
 				if curr.nth {
-					base = base.WithAttr(attrNth)
+					base = nthBase
 				}
 				if hidden {
 					base = base.WithFg(theme.Nomatch)
@@ -265,7 +274,7 @@ func (result *Result) colorOffsets(matchOffsets []Offset, nthOffsets []Offset, t
 					match:  false,
 					url:    ansi.color.url})
 			} else {
-				color := colBase.WithAttr(attrNth)
+				color := nthBase
 				if hidden {
 					color = color.WithFg(theme.Nomatch)
 				}
@@ -334,3 +343,79 @@ func (a ByRelevanceTac) Swap(i, j int) {
 func (a ByRelevanceTac) Less(i, j int) bool {
 	return compareRanks(a[i], a[j], true)
 }
+
+// radixSortResults sorts Results by their points key using LSD radix sort.
+// O(n) time complexity vs O(n log n) for comparison sort.
+// The sort is stable, so equal-key items maintain original (item-index) order.
+// For tac mode, runs of equal keys are reversed after sorting.
+func radixSortResults(a []Result, tac bool, scratch []Result) []Result {
+	n := len(a)
+	if n < 128 {
+		if tac {
+			sort.Sort(ByRelevanceTac(a))
+		} else {
+			sort.Sort(ByRelevance(a))
+		}
+		return scratch[:0]
+	}
+
+	if cap(scratch) < n {
+		scratch = make([]Result, n)
+	}
+	buf := scratch[:n]
+	src, dst := a, buf
+	scattered := 0
+
+	for pass := range 8 {
+		shift := uint(pass) * 8
+
+		var count [256]int
+		for i := range src {
+			count[byte(sortKey(&src[i])>>shift)]++
+		}
+
+		// Skip if all items have the same byte value at this position
+		if count[byte(sortKey(&src[0])>>shift)] == n {
+			continue
+		}
+
+		var offset [256]int
+		for i := 1; i < 256; i++ {
+			offset[i] = offset[i-1] + count[i-1]
+		}
+
+		for i := range src {
+			b := byte(sortKey(&src[i]) >> shift)
+			dst[offset[b]] = src[i]
+			offset[b]++
+		}
+
+		src, dst = dst, src
+		scattered++
+	}
+
+	// If odd number of scatters, data is in buf, copy back to a
+	if scattered%2 == 1 {
+		copy(a, src)
+	}
+
+	// Handle tac: reverse runs of equal keys so equal-key items
+	// are in reverse item-index order
+	if tac {
+		i := 0
+		for i < n {
+			ki := sortKey(&a[i])
+			j := i + 1
+			for j < n && sortKey(&a[j]) == ki {
+				j++
+			}
+			if j-i > 1 {
+				for l, r := i, j-1; l < r; l, r = l+1, r-1 {
+					a[l], a[r] = a[r], a[l]
+				}
+			}
+			i = j
+		}
+	}
+	return scratch
+}

src/result_others.go

@@ -14,3 +14,7 @@ func compareRanks(irank Result, jrank Result, tac bool) bool {
 	}
 	return (irank.item.Index() <= jrank.item.Index()) != tac
 }
+
+func sortKey(r *Result) uint64 {
+	return uint64(r.points[0]) | uint64(r.points[1])<<16 | uint64(r.points[2])<<32 | uint64(r.points[3])<<48
+}

src/result_test.go

@@ -2,6 +2,7 @@ package fzf
 
 import (
 	"math"
+	"math/rand"
 	"sort"
 	"testing"
 
@@ -131,7 +132,7 @@ func TestColorOffset(t *testing.T) {
 
 	colBase := tui.NewColorPair(89, 189, tui.AttrUndefined)
 	colMatch := tui.NewColorPair(99, 199, tui.AttrUndefined)
-	colors := item.colorOffsets(offsets, nil, tui.Dark256, colBase, colMatch, tui.AttrUndefined, false)
+	colors := item.colorOffsets(offsets, nil, tui.Dark256, colBase, colMatch, tui.AttrUndefined, 0, false)
 	assert := func(idx int, b int32, e int32, c tui.ColorPair) {
 		o := colors[idx]
 		if o.offset[0] != b || o.offset[1] != e || o.color != c {
@@ -158,7 +159,7 @@ func TestColorOffset(t *testing.T) {
 
 	nthOffsets := []Offset{{37, 39}, {42, 45}}
 	for _, attr := range []tui.Attr{tui.AttrRegular, tui.StrikeThrough} {
-		colors = item.colorOffsets(offsets, nthOffsets, tui.Dark256, colRegular, colUnderline, attr, false)
+		colors = item.colorOffsets(offsets, nthOffsets, tui.Dark256, colRegular, colUnderline, attr, 0, false)
 
 		// [{[0 5] {1 5 0}} {[5 15] {1 5 8}} {[15 20] {1 5 0}}
 		//  {[22 25] {2 6 1}} {[25 27] {2 6 9}} {[27 30] {-1 -1 8}}
@@ -181,4 +182,92 @@ func TestColorOffset(t *testing.T) {
 		assert(10, 37, 39, tui.NewColorPair(4, 8, expected))
 		assert(11, 39, 40, tui.NewColorPair(4, 8, tui.Bold))
 	}
+
+	// Test nthOverlay: simulates nth:regular with current-fg:underline
+	// The overlay (underline) should survive even though nth:regular clears attrs.
+	// Precedence: fg < nth < current-fg
+	colors = item.colorOffsets(offsets, nthOffsets, tui.Dark256, colRegular, colUnderline, tui.AttrRegular, tui.Underline, false)
+
+	// nth regions should have Underline (from overlay), not cleared by AttrRegular
+	// Non-nth regions keep colBase attrs (AttrUndefined)
+	assert(0, 0, 5, tui.NewColorPair(1, 5, tui.AttrUndefined))
+	assert(1, 5, 15, tui.NewColorPair(1, 5, tui.Underline))
+	assert(2, 15, 20, tui.NewColorPair(1, 5, tui.AttrUndefined))
+	assert(3, 22, 25, tui.NewColorPair(2, 6, tui.Bold))
+	assert(4, 25, 27, tui.NewColorPair(2, 6, tui.Bold|tui.Underline))
+	assert(5, 27, 30, colUnderline)
+	assert(6, 30, 32, tui.NewColorPair(3, 7, tui.Underline))
+	assert(7, 32, 33, colUnderline)
+	assert(8, 33, 35, tui.NewColorPair(4, 8, tui.Bold|tui.Underline))
+	assert(9, 35, 37, tui.NewColorPair(4, 8, tui.Bold))
+	// nth region within ANSI bold: AttrRegular clears, overlay adds Underline back
+	assert(10, 37, 39, tui.NewColorPair(4, 8, tui.Bold|tui.Underline))
+	assert(11, 39, 40, tui.NewColorPair(4, 8, tui.Bold))
+
+	// Test nthOverlay with additive attrs: nth:strikethrough with selected-fg:bold
+	colors = item.colorOffsets(offsets, nthOffsets, tui.Dark256, colRegular, colUnderline, tui.StrikeThrough, tui.Bold, false)
+
+	// Non-nth entries unchanged from overlay=0 case
+	assert(0, 0, 5, tui.NewColorPair(1, 5, tui.AttrUndefined))
+	assert(5, 27, 30, colUnderline) // match only, no nth
+	assert(7, 32, 33, colUnderline) // match only, no nth
+	// nth region within ANSI bold: StrikeThrough|Bold merged with ANSI Bold
+	assert(10, 37, 39, tui.NewColorPair(4, 8, tui.Bold|tui.StrikeThrough))
+}
+
+func TestRadixSortResults(t *testing.T) {
+	sortCriteria = []criterion{byScore, byLength}
+
+	rng := rand.New(rand.NewSource(42))
+
+	for _, n := range []int{128, 256, 500, 1000} {
+		for _, tac := range []bool{false, true} {
+			// Build items with random points and indices
+			items := make([]*Item, n)
+			for i := range items {
+				items[i] = &Item{text: util.Chars{Index: int32(i)}}
+			}
+
+			results := make([]Result, n)
+			for i := range results {
+				results[i] = Result{
+					item: items[i],
+					points: [4]uint16{
+						uint16(rng.Intn(256)),
+						uint16(rng.Intn(256)),
+						uint16(rng.Intn(256)),
+						uint16(rng.Intn(256)),
+					},
+				}
+			}
+
+			// Make some duplicates to test stability
+			for i := 0; i < n/4; i++ {
+				j := rng.Intn(n)
+				k := rng.Intn(n)
+				results[j].points = results[k].points
+			}
+
+			// Copy for reference sort
+			expected := make([]Result, n)
+			copy(expected, results)
+			if tac {
+				sort.Sort(ByRelevanceTac(expected))
+			} else {
+				sort.Sort(ByRelevance(expected))
+			}
+
+			// Radix sort
+			var scratch []Result
+			scratch = radixSortResults(results, tac, scratch)
+
+			for i := range results {
+				if results[i] != expected[i] {
+					t.Errorf("n=%d tac=%v: mismatch at index %d: got item %d, want item %d",
+						n, tac, i, results[i].item.Index(), expected[i].item.Index())
+					break
+				}
+			}
+		}
+	}
 }

src/result_x86.go

@@ -14,3 +14,7 @@ func compareRanks(irank Result, jrank Result, tac bool) bool {
 	}
 	return (irank.item.Index() <= jrank.item.Index()) != tac
 }
+
+func sortKey(r *Result) uint64 {
+	return *(*uint64)(unsafe.Pointer(&r.points[0]))
+}

src/terminal.go

@@ -340,6 +340,9 @@ type Terminal struct {
 	nthAttr              tui.Attr
 	nth                  []Range
 	nthCurrent           []Range
+	withNthDefault       string
+	withNthExpr          string
+	withNthEnabled       bool
 	acceptNth            func([]Token, int32) string
 	tabstop              int
 	margin               [4]sizeSpec
@@ -384,6 +387,7 @@ type Terminal struct {
 	hasLoadActions       bool
 	hasResizeActions     bool
 	triggerLoad          bool
+	filterSelection      bool
 	reading              bool
 	running              *util.AtomicBool
 	failed               *string
@@ -551,6 +555,7 @@ const (
 	actChangeListLabel
 	actChangeMulti
 	actChangeNth
+	actChangeWithNth
 	actChangePointer
 	actChangePreview
 	actChangePreviewLabel
@@ -636,6 +641,7 @@ const (
 	actTransformInputLabel
 	actTransformListLabel
 	actTransformNth
+	actTransformWithNth
 	actTransformPointer
 	actTransformPreviewLabel
 	actTransformPrompt
@@ -655,6 +661,7 @@ const (
 	actBgTransformInputLabel
 	actBgTransformListLabel
 	actBgTransformNth
+	actBgTransformWithNth
 	actBgTransformPointer
 	actBgTransformPreviewLabel
 	actBgTransformPrompt
@@ -721,6 +728,7 @@ func processExecution(action actionType) bool {
 		actTransformInputLabel,
 		actTransformListLabel,
 		actTransformNth,
+		actTransformWithNth,
 		actTransformPointer,
 		actTransformPreviewLabel,
 		actTransformPrompt,
@@ -737,6 +745,7 @@ func processExecution(action actionType) bool {
 		actBgTransformInputLabel,
 		actBgTransformListLabel,
 		actBgTransformNth,
+		actBgTransformWithNth,
 		actBgTransformPointer,
 		actBgTransformPreviewLabel,
 		actBgTransformPrompt,
@@ -766,10 +775,15 @@ type placeholderFlags struct {
 	raw           bool
 }
 
+type withNthSpec struct {
+	fn func([]Token, int32) string // nil = clear (restore original)
+}
+
 type searchRequest struct {
 	sort        bool
 	sync        bool
 	nth         *[]Range
+	withNth     *withNthSpec
 	headerLines *int
 	command     *commandSpec
 	environ     []string
@@ -1080,6 +1094,9 @@ func NewTerminal(opts *Options, eventBox *util.EventBox, executor *util.Executor
 		nthAttr:            opts.Theme.Nth.Attr,
 		nth:                opts.Nth,
 		nthCurrent:         opts.Nth,
+		withNthDefault:     opts.WithNthExpr,
+		withNthExpr:        opts.WithNthExpr,
+		withNthEnabled:     opts.WithNth != nil,
 		tabstop:            opts.Tabstop,
 		raw:                opts.Raw,
 		hasStartActions:    false,
@@ -1351,6 +1368,9 @@ func (t *Terminal) environImpl(forPreview bool) []string {
 	if len(t.nthCurrent) > 0 {
 		env = append(env, "FZF_NTH="+RangesToString(t.nthCurrent))
 	}
+	if len(t.withNthExpr) > 0 {
+		env = append(env, "FZF_WITH_NTH="+t.withNthExpr)
+	}
 	if t.raw {
 		val := "0"
 		if t.isCurrentItemMatch() {
@@ -1534,7 +1554,7 @@ func (t *Terminal) ansiLabelPrinter(str string, color *tui.ColorPair, fill bool)
 	printFn := func(window tui.Window, limit int) {
 		if offsets == nil {
 			// tui.Col* are not initialized until renderer.Init()
-			offsets = result.colorOffsets(nil, nil, t.theme, *color, *color, t.nthAttr, false)
+			offsets = result.colorOffsets(nil, nil, t.theme, *color, *color, t.nthAttr, 0, false)
 		}
 		for limit > 0 {
 			if length > limit {
@@ -1597,7 +1617,7 @@ func (t *Terminal) parsePrompt(prompt string) (func(), int) {
 				return 1
 			}
 			t.printHighlighted(
-				Result{item: item}, tui.ColPrompt, tui.ColPrompt, false, false, false, line, line, true, preTask, nil)
+				Result{item: item}, tui.ColPrompt, tui.ColPrompt, false, false, false, line, line, true, preTask, nil, 0)
 		})
 		t.wrap = wrap
 	}
@@ -1720,6 +1740,17 @@ func (t *Terminal) Input() (bool, []rune) {
 	return paused, copySlice(src)
 }
 
+// PauseRendering blocks the terminal from reading items.
+// Must be paired with ResumeRendering.
+func (t *Terminal) PauseRendering() {
+	t.mutex.Lock()
+}
+
+// ResumeRendering releases the lock acquired by PauseRendering.
+func (t *Terminal) ResumeRendering() {
+	t.mutex.Unlock()
+}
+
 // UpdateCount updates the count information
 func (t *Terminal) UpdateCount(cnt int, final bool, failedCommand *string) {
 	t.mutex.Lock()
@@ -1842,6 +1873,21 @@ func (t *Terminal) UpdateList(result MatchResult) {
 		}
 		t.revision = newRevision
 		t.version++
+
+		// Filter out selections that no longer match after with-nth change.
+		// Must be inside the revision check so we don't consume the flag
+		// on a stale EvtSearchFin from a previous search.
+		if t.filterSelection && t.multi > 0 && len(t.selected) > 0 {
+			matchMap := t.resultMerger.ToMap()
+			filtered := make(map[int32]selectedItem)
+			for k, v := range t.selected {
+				if _, matched := matchMap[k]; matched {
+					filtered[k] = v
+				}
+			}
+			t.selected = filtered
+		}
+		t.filterSelection = false
 	}
 	if t.triggerLoad {
 		t.triggerLoad = false
@@ -3139,7 +3185,7 @@ func (t *Terminal) printFooter() {
 				func(markerClass) int {
 					t.footerWindow.Print(indent)
 					return indentSize
-				}, nil)
+				}, nil, 0)
 		}
 	})
 	t.wrap = wrap
@@ -3223,7 +3269,7 @@ func (t *Terminal) printHeaderImpl(window tui.Window, borderShape tui.BorderShap
 			func(markerClass) int {
 				t.window.Print(indent)
 				return indentSize
-			}, nil)
+			}, nil, 0)
 	}
 	t.wrap = wrap
 }
@@ -3461,7 +3507,14 @@ func (t *Terminal) printItem(result Result, line int, maxLine int, index int, cu
 			}
 			return indentSize
 		}
-		finalLineNum = t.printHighlighted(result, tui.ColCurrent, tui.ColCurrentMatch, true, true, !matched, line, maxLine, forceRedraw, preTask, postTask)
+		colCurrent := tui.ColCurrent
+		nthOverlay := t.theme.NthCurrentAttr
+		if selected {
+			nthOverlay = t.theme.NthSelectedAttr.Merge(t.theme.NthCurrentAttr)
+			baseAttr := tui.ColNormal.Attr().Merge(t.theme.NthSelectedAttr).Merge(t.theme.NthCurrentAttr)
+			colCurrent = colCurrent.WithNewAttr(baseAttr)
+		}
+		finalLineNum = t.printHighlighted(result, colCurrent, tui.ColCurrentMatch, true, true, !matched, line, maxLine, forceRedraw, preTask, postTask, nthOverlay)
 	} else {
 		preTask := func(marker markerClass) int {
 			w := t.window.Width() - t.pointerLen
@@ -3495,7 +3548,11 @@ func (t *Terminal) printItem(result Result, line int, maxLine int, index int, cu
 			base = base.WithBg(altBg)
 			match = match.WithBg(altBg)
 		}
-		finalLineNum = t.printHighlighted(result, base, match, false, true, !matched, line, maxLine, forceRedraw, preTask, postTask)
+		var nthOverlay tui.Attr
+		if selected {
+			nthOverlay = t.theme.NthSelectedAttr
+		}
+		finalLineNum = t.printHighlighted(result, base, match, false, true, !matched, line, maxLine, forceRedraw, preTask, postTask, nthOverlay)
 	}
 	for i := 0; i < t.gap && finalLineNum < maxLine; i++ {
 		finalLineNum++
@@ -3596,7 +3653,7 @@ func (t *Terminal) overflow(runes []rune, max int) bool {
 	return t.displayWidthWithLimit(runes, 0, max) > max
 }
 
-func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMatch tui.ColorPair, current bool, match bool, hidden bool, lineNum int, maxLineNum int, forceRedraw bool, preTask func(markerClass) int, postTask func(int, int, bool, bool, tui.ColorPair)) int {
+func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMatch tui.ColorPair, current bool, match bool, hidden bool, lineNum int, maxLineNum int, forceRedraw bool, preTask func(markerClass) int, postTask func(int, int, bool, bool, tui.ColorPair), nthOverlay tui.Attr) int {
 	var displayWidth int
 	item := result.item
 	matchOffsets := []Offset{}
@@ -3637,7 +3694,9 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 			// But if 'nth' is set to 'regular', it's a sign that you're applying
 			// a different style to the rest of the string. e.g. 'nth:regular,fg:dim'
 			// In this case, we still need to apply it to clear the style.
-			colBase = colBase.WithAttr(t.nthAttr)
+			fgAttr := tui.ColNormal.Attr()
+			nthAttrFinal := fgAttr.Merge(t.nthAttr).Merge(nthOverlay)
+			colBase = colBase.WithNewAttr(nthAttrFinal)
 		}
 		if !wholeCovered && t.nthAttr > 0 {
 			var tokens []Token
@@ -3656,7 +3715,7 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 			sort.Sort(ByOrder(nthOffsets))
 		}
 	}
-	allOffsets := result.colorOffsets(charOffsets, nthOffsets, t.theme, colBase, colMatch, t.nthAttr, hidden)
+	allOffsets := result.colorOffsets(charOffsets, nthOffsets, t.theme, colBase, colMatch, t.nthAttr, nthOverlay, hidden)
 
 	// Determine split offset for horizontal scrolling with freeze
 	splitOffset1 := -1
@@ -5922,6 +5981,7 @@ func (t *Terminal) Loop() error {
 	events := []util.EventType{}
 	changed := false
 	var newNth *[]Range
+	var newWithNth *withNthSpec
 	var newHeaderLines *int
 	req := func(evts ...util.EventType) {
 		for _, event := range evts {
@@ -5939,6 +5999,7 @@ func (t *Terminal) Loop() error {
 		events = []util.EventType{}
 		changed = false
 		newNth = nil
+		newWithNth = nil
 		newHeaderLines = nil
 		beof := false
 		queryChanged := false
@@ -6330,6 +6391,33 @@ func (t *Terminal) Loop() error {
 						t.forceRerenderList()
 					}
 				})
+			case actChangeWithNth, actTransformWithNth, actBgTransformWithNth:
+				if !t.withNthEnabled {
+					break Action
+				}
+				capture(true, func(expr string) {
+					tokens := strings.Split(expr, "|")
+					withNthExpr := tokens[0]
+					if len(tokens) > 1 {
+						a.a = strings.Join(append(tokens[1:], tokens[0]), "|")
+					}
+					// Empty value restores the default --with-nth
+					if len(withNthExpr) == 0 {
+						withNthExpr = t.withNthDefault
+					}
+					if withNthExpr != t.withNthExpr {
+						if factory, err := nthTransformer(withNthExpr); err == nil {
+							newWithNth = &withNthSpec{fn: factory(t.delimiter)}
+						} else {
+							return
+						}
+						t.withNthExpr = withNthExpr
+						t.filterSelection = true
+						changed = true
+						t.clearNumLinesCache()
+						t.forceRerenderList()
+					}
+				})
 			case actChangeQuery:
 				t.input = []rune(a.a)
 				t.cx = len(t.input)
@@ -7477,7 +7565,7 @@ func (t *Terminal) Loop() error {
 		reload := changed || newCommand != nil
 		var reloadRequest *searchRequest
 		if reload {
-			reloadRequest = &searchRequest{sort: t.sort, sync: reloadSync, nth: newNth, headerLines: newHeaderLines, command: newCommand, environ: t.environ(), changed: changed, denylist: denylist, revision: t.resultMerger.Revision()}
+			reloadRequest = &searchRequest{sort: t.sort, sync: reloadSync, nth: newNth, withNth: newWithNth, headerLines: newHeaderLines, command: newCommand, environ: t.environ(), changed: changed, denylist: denylist, revision: t.resultMerger.Revision()}
 		}
 
 		// Dispatch queued background requests

src/tui/tui.go

@@ -447,6 +447,12 @@ func (p ColorPair) WithAttr(attr Attr) ColorPair {
 	return dup
 }
 
+func (p ColorPair) WithNewAttr(attr Attr) ColorPair {
+	dup := p
+	dup.attr = attr
+	return dup
+}
+
 func (p ColorPair) WithFg(fg ColorAttr) ColorPair {
 	dup := p
 	fgPair := ColorPair{fg.Color, colUndefined, colUndefined, fg.Attr}
@@ -520,6 +526,8 @@ type ColorTheme struct {
 	ListLabel        ColorAttr
 	ListBorder       ColorAttr
 	GapLine          ColorAttr
+	NthCurrentAttr   Attr // raw current-fg attr (before fg merge) for nth overlay
+	NthSelectedAttr  Attr // raw selected-fg attr (before ListFg inherit) for nth overlay
 }
 
 type Event struct {
@@ -1199,13 +1207,19 @@ func InitTheme(theme *ColorTheme, baseTheme *ColorTheme, boldify bool, forceBlac
 		match.Attr = Underline
 	}
 	theme.Match = o(baseTheme.Match, match)
-	// Inherit from 'fg', so that we don't have to write 'current-fg:dim'
+	// These colors are not defined in the base themes.
+	// Resolve ListFg/ListBg early so Current and Selected can inherit from them.
+	theme.ListFg = o(theme.Fg, theme.ListFg)
+	theme.ListBg = o(theme.Bg, theme.ListBg)
+	// Inherit from 'list-fg', so that we don't have to write 'current-fg:dim'
 	// e.g. fzf --delimiter / --nth -1 --color fg:dim,nth:regular
 	current := theme.Current
 	if !baseTheme.Colored && current.IsUndefined() {
 		current.Attr |= Reverse
 	}
-	theme.Current = theme.Fg.Merge(o(baseTheme.Current, current))
+	resolvedCurrent := o(baseTheme.Current, current)
+	theme.NthCurrentAttr = resolvedCurrent.Attr
+	theme.Current = theme.ListFg.Merge(resolvedCurrent)
 	currentMatch := theme.CurrentMatch
 	if !baseTheme.Colored && currentMatch.IsUndefined() {
 		currentMatch.Attr |= Reverse | Underline
@@ -1230,10 +1244,8 @@ func InitTheme(theme *ColorTheme, baseTheme *ColorTheme, boldify bool, forceBlac
 	scrollbarDefined := theme.Scrollbar != undefined
 	previewBorderDefined := theme.PreviewBorder != undefined
 
-	// These colors are not defined in the base themes
-	theme.ListFg = o(theme.Fg, theme.ListFg)
-	theme.ListBg = o(theme.Bg, theme.ListBg)
-	theme.SelectedFg = o(theme.ListFg, theme.SelectedFg)
+	theme.NthSelectedAttr = theme.SelectedFg.Attr
+	theme.SelectedFg = theme.ListFg.Merge(theme.SelectedFg)
 	theme.SelectedBg = o(theme.ListBg, theme.SelectedBg)
 	theme.SelectedMatch = o(theme.Match, theme.SelectedMatch)
 

test/test_core.rb

@@ -1745,6 +1745,191 @@ class TestCore < TestInteractive
     end
   end
 
+  def test_change_with_nth
+    input = [
+      'foo bar baz',
+      'aaa bbb ccc',
+      'xxx yyy zzz'
+    ]
+    writelines(input)
+    # Start with field 1 only, cycle through fields, verify $FZF_WITH_NTH via prompt
+    tmux.send_keys %(#{FZF} --with-nth 1 --bind 'space:change-with-nth(2|3|1),result:transform-prompt:echo "[$FZF_WITH_NTH]> "' < #{tempname}), :Enter
+    tmux.until do |lines|
+      assert_equal 3, lines.item_count
+      assert lines.any_include?('[1]>')
+      assert lines.any_include?('foo')
+      refute lines.any_include?('bar')
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('[2]>')
+      assert lines.any_include?('bar')
+      refute lines.any_include?('foo')
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('[3]>')
+      assert lines.any_include?('baz')
+      refute lines.any_include?('bar')
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('[1]>')
+      assert lines.any_include?('foo')
+      refute lines.any_include?('bar')
+    end
+  end
+
+  def test_change_with_nth_default
+    # Empty value restores the default --with-nth
+    tmux.send_keys %(echo -e 'a b c\nd e f' | #{FZF} --with-nth 1 --bind 'space:change-with-nth(2|)'), :Enter
+    tmux.until do |lines|
+      assert_equal 2, lines.item_count
+      assert lines.any_include?('a')
+      refute lines.any_include?('b')
+    end
+    # Switch to field 2
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('b')
+      refute lines.any_include?('a')
+    end
+    # Empty restores default (field 1)
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('a')
+      refute lines.any_include?('b')
+    end
+  end
+
+  def test_transform_with_nth_search
+    input = [
+      'alpha bravo charlie',
+      'delta echo foxtrot',
+      'golf hotel india'
+    ]
+    writelines(input)
+    tmux.send_keys %(#{FZF} --with-nth 1 --bind 'space:transform-with-nth(echo 2)' -q '^bravo$' < #{tempname}), :Enter
+    tmux.until do |lines|
+      assert_equal 0, lines.match_count
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert_equal 1, lines.match_count
+    end
+  end
+
+  def test_bg_transform_with_nth_output
+    tmux.send_keys %(echo -e 'a b c\nd e f' | #{FZF} --with-nth 2 --bind 'space:bg-transform-with-nth(echo 3)'), :Enter
+    tmux.until do |lines|
+      assert_equal 2, lines.item_count
+      assert lines.any_include?('b')
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('c')
+      refute lines.any_include?('b')
+    end
+    tmux.send_keys :Enter
+    tmux.until { |lines| assert lines.any_include?('a b c') || lines.any_include?('d e f') }
+  end
+
+  def test_change_with_nth_search
+    input = [
+      'alpha bravo charlie',
+      'delta echo foxtrot',
+      'golf hotel india'
+    ]
+    writelines(input)
+    tmux.send_keys %(#{FZF} --with-nth 1 --bind 'space:change-with-nth(2)' -q '^bravo$' < #{tempname}), :Enter
+    tmux.until do |lines|
+      assert_equal 0, lines.match_count
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert_equal 1, lines.match_count
+    end
+  end
+
+  def test_change_with_nth_output
+    tmux.send_keys %(echo -e 'a b c\nd e f' | #{FZF} --with-nth 2 --bind 'space:change-with-nth(3)'), :Enter
+    tmux.until do |lines|
+      assert_equal 2, lines.item_count
+      assert lines.any_include?('b')
+    end
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('c')
+      refute lines.any_include?('b')
+    end
+    tmux.send_keys :Enter
+    tmux.until { |lines| assert lines.any_include?('a b c') || lines.any_include?('d e f') }
+  end
+
+  def test_change_with_nth_selection
+    # Items: field1 has unique values, field2 has 'match' or 'miss'
+    input = [
+      'one match x',
+      'two miss y',
+      'three match z'
+    ]
+    writelines(input)
+    # Start showing field 2 (match/miss), query 'match', select all matches, then switch to field 3
+    tmux.send_keys %(#{FZF} --with-nth 2 --multi --bind 'ctrl-a:select-all,space:change-with-nth(3)' -q match < #{tempname}), :Enter
+    tmux.until do |lines|
+      assert_equal 2, lines.match_count
+    end
+    # Select all matching items
+    tmux.send_keys 'C-a'
+    tmux.until do |lines|
+      assert lines.any_include?('(2)')
+    end
+    # Now change with-nth to field 3; 'x' and 'z' don't contain 'match'
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert_equal 0, lines.match_count
+      # Selections of non-matching items should be cleared
+      assert lines.any_include?('(0)')
+    end
+  end
+
+  def test_change_with_nth_multiline
+    # Each item has 3 lines: "N-a\nN-b\nN-c"
+    # --with-nth 1 shows 1 line per item, --with-nth 1..3 shows 3 lines per item
+    tmux.send_keys %(seq 20 | xargs -I{} printf '{}-a\\n{}-b\\n{}-c\\0' | #{FZF} --read0 --delimiter "\n" --with-nth 1 --bind 'space:change-with-nth(1..3|1)' --no-sort), :Enter
+    tmux.until do |lines|
+      assert_equal 20, lines.item_count
+      assert lines.any_include?('1-a')
+      refute lines.any_include?('1-b')
+    end
+    # Expand to 3 lines per item
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('1-a')
+      assert lines.any_include?('1-b')
+      assert lines.any_include?('1-c')
+    end
+    # Scroll down a few items
+    5.times { tmux.send_keys :Down }
+    tmux.until do |lines|
+      assert lines.any_include?('6-a')
+      assert lines.any_include?('6-b')
+      assert lines.any_include?('6-c')
+    end
+    # Collapse back to 1 line per item
+    tmux.send_keys :Space
+    tmux.until do |lines|
+      assert lines.any_include?('6-a')
+      refute lines.any_include?('6-b')
+    end
+    # Scroll down more after collapse
+    5.times { tmux.send_keys :Down }
+    tmux.until do |lines|
+      assert lines.any_include?('11-a')
+      refute lines.any_include?('11-b')
+    end
+  end
+
   def test_env_vars
     def env_vars
       return {} unless File.exist?(tempname)