diff --git a/invokeai/frontend/webv2/public/locales/en.json b/invokeai/frontend/webv2/public/locales/en.json
index 6681668ad15..f208c5e8787 100644
--- a/invokeai/frontend/webv2/public/locales/en.json
+++ b/invokeai/frontend/webv2/public/locales/en.json
@@ -3523,6 +3523,8 @@
       "lastFrameExtendHelp": "Optional destination: the extension ends on this image.",
       "lastFrameHelp": "Optional: the video ends on this image (interpolates from the first frame).",
       "removeClip": "Remove video",
+      "sampleLength": "Sample Length (Frames)",
+      "sampleLengthWithSeconds": "Sample Length · {{seconds}}s",
       "trim": "Trim",
       "trimEnd": "End Frame",
       "trimEndShort": "End",
diff --git a/invokeai/frontend/webv2/src/features/video/core/settings.test.ts b/invokeai/frontend/webv2/src/features/video/core/settings.test.ts
index 19f0ac57711..ca57edd3943 100644
--- a/invokeai/frontend/webv2/src/features/video/core/settings.test.ts
+++ b/invokeai/frontend/webv2/src/features/video/core/settings.test.ts
@@ -4,6 +4,8 @@ import type { VideoReferenceItem, VideoSettings } from './types';
 
 import { MINIMAX_H3_NUM_FRAMES_CHOICES } from './dimensions';
 import {
+  resizeReferenceSampleWindow,
+  slideReferenceSampleWindow,
   applyReferenceExtendSourceVideo,
   applyReferenceExtendNumFrames,
   canPlaceReferenceExtendAnchor,
@@ -869,3 +871,85 @@ describe('reference-extend linkage', () => {
     expect(applyReferenceExtendNumFrames(unlinked, 90)).toBe(unlinked);
   });
 });
+
+describe('reference sample window', () => {
+  const clip = (startFrame: number, endFrame: number, numFrames = 300) => ({
+    endFrame,
+    fps: 24,
+    height: 480,
+    numFrames,
+    startFrame,
+    video_name: 'clip.mp4',
+    width: 640,
+  });
+
+  describe('slideReferenceSampleWindow', () => {
+    it('slides an ordinary window at constant length', () => {
+      const next = slideReferenceSampleWindow(clip(0, 199), 50, false);
+      expect([next.startFrame, next.endFrame]).toEqual([50, 249]);
+    });
+
+    it('stops at the clip end instead of shrinking (no overshoot ratchet)', () => {
+      // Drag far past the wall, then back to 0: the length must survive the round trip.
+      const overshot = slideReferenceSampleWindow(clip(0, 199), 299, false);
+      expect([overshot.startFrame, overshot.endFrame]).toEqual([100, 299]);
+      const back = slideReferenceSampleWindow(overshot, 0, false);
+      expect([back.startFrame, back.endFrame]).toEqual([0, 199]);
+    });
+
+    it('keeps the extend anchor end pinned to the cutpoint', () => {
+      // The anchor's seam continuity depends on frames adjacent to its end frame.
+      const next = slideReferenceSampleWindow(clip(180, 298), 200, true);
+      expect([next.startFrame, next.endFrame]).toEqual([200, 298]);
+      const backAndForth = slideReferenceSampleWindow(slideReferenceSampleWindow(next, 250, true), 200, true);
+      expect([backAndForth.startFrame, backAndForth.endFrame]).toEqual([200, 298]);
+    });
+
+    it('clamps the anchor start to its pinned end', () => {
+      const next = slideReferenceSampleWindow(clip(180, 298), 500, true);
+      expect([next.startFrame, next.endFrame]).toEqual([298, 298]);
+    });
+
+    it('self-heals a corrupt persisted trim into bounds', () => {
+      // end < start and end beyond the clip must both come back as a valid window.
+      const inverted = slideReferenceSampleWindow(clip(10, 5, 20), 0, false);
+      expect(inverted.startFrame).toBeGreaterThanOrEqual(0);
+      expect(inverted.endFrame).toBeGreaterThanOrEqual(inverted.startFrame);
+      expect(inverted.endFrame).toBeLessThanOrEqual(19);
+      const oversized = slideReferenceSampleWindow(clip(0, 999, 20), 5, false);
+      expect([oversized.startFrame, oversized.endFrame]).toEqual([0, 19]);
+    });
+
+    it('handles a single-frame clip', () => {
+      const next = slideReferenceSampleWindow(clip(0, 0, 1), 5, false);
+      expect([next.startFrame, next.endFrame]).toEqual([0, 0]);
+    });
+  });
+
+  describe('resizeReferenceSampleWindow', () => {
+    it('grows an ordinary window forward from its start', () => {
+      const next = resizeReferenceSampleWindow(clip(50, 60), 100, false);
+      expect([next.startFrame, next.endFrame]).toEqual([50, 149]);
+    });
+
+    it('clamps the length to the clip end', () => {
+      const next = resizeReferenceSampleWindow(clip(250, 260), 100, false);
+      expect([next.startFrame, next.endFrame]).toEqual([250, 299]);
+    });
+
+    it('grows the extend anchor backward from its pinned end', () => {
+      const next = resizeReferenceSampleWindow(clip(280, 298), 100, true);
+      expect([next.startFrame, next.endFrame]).toEqual([199, 298]);
+    });
+
+    it('clamps the anchor lead-in at the clip start', () => {
+      const next = resizeReferenceSampleWindow(clip(280, 298), 1000, true);
+      expect([next.startFrame, next.endFrame]).toEqual([0, 298]);
+    });
+
+    it('never produces a window shorter than one frame', () => {
+      const next = resizeReferenceSampleWindow(clip(50, 199), -5, false);
+      expect([next.startFrame, next.endFrame]).toEqual([50, 50]);
+    });
+  });
+});
diff --git a/invokeai/frontend/webv2/src/features/video/core/settings.ts b/invokeai/frontend/webv2/src/features/video/core/settings.ts
index 4cbc9cd8558..2445a82563a 100644
--- a/invokeai/frontend/webv2/src/features/video/core/settings.ts
+++ b/invokeai/frontend/webv2/src/features/video/core/settings.ts
@@ -79,6 +79,73 @@ export const isVideoSourceClip = (value: unknown): value is VideoSourceClip =>
 export const VIDEO_REFERENCE_MAX_VIDEOS = 3;
 export const VIDEO_REFERENCE_MAX_IMAGES = 9;
 
+/**
+ * Default sample length (in frames) for a newly added video reference. Reference rows cost
+ * VRAM in every denoise step — the packed sequence grows with reference length — so the
+ * useful sample is a short window that captures the wanted visual/audio features, not the
+ * whole clip. 200 frames ≈ 8s at the models' native 24 fps.
+ */
+export const DEFAULT_REFERENCE_SAMPLE_FRAMES = 200;
+
+/**
+ * Move a reference clip's sample window to a new start frame.
+ *
+ * Ordinary references slide at CONSTANT length, stopping at the clip's end rather than
+ * shrinking — a transient overshoot during a drag must not ratchet the sample down. The
+ * reference-extend anchor (`pinEnd`) instead keeps its end frame pinned to the Initial
+ * Video cutpoint (seam continuity depends on the frames adjacent to it; see
+ * deriveReferenceExtendClip), so moving its start only adjusts the lead-in length.
+ *
+ * Self-healing by construction: the returned window always satisfies
+ * 0 <= start <= end <= numFrames - 1, even from a corrupt persisted trim.
+ */
+export const slideReferenceSampleWindow = (
+  clip: VideoSourceClip,
+  rawStart: number,
+  pinEnd: boolean
+): VideoSourceClip => {
+  const maxFrame = Math.max(0, clip.numFrames - 1);
+
+  if (pinEnd) {
+    const endFrame = Math.min(Math.max(0, clip.endFrame), maxFrame);
+    const startFrame = Math.min(Math.max(0, Math.round(rawStart)), endFrame);
+
+    return { ...clip, endFrame, startFrame };
+  }
+
+  const sampleFrames = Math.min(Math.max(1, clip.endFrame - clip.startFrame + 1), maxFrame + 1);
+  const startFrame = Math.min(Math.max(0, Math.round(rawStart)), maxFrame - (sampleFrames - 1));
+
+  return { ...clip, endFrame: startFrame + sampleFrames - 1, startFrame };
+};
+
+/**
+ * Resize a reference clip's sample window to a new length in frames.
+ *
+ * Ordinary references grow from the start frame (the end moves, clamped to the clip); the
+ * reference-extend anchor (`pinEnd`) grows backward from its pinned end (the start moves),
+ * since its end must stay on the Initial Video cutpoint. Same self-healing bounds as
+ * slideReferenceSampleWindow.
+ */
+export const resizeReferenceSampleWindow = (
+  clip: VideoSourceClip,
+  rawSampleFrames: number,
+  pinEnd: boolean
+): VideoSourceClip => {
+  const maxFrame = Math.max(0, clip.numFrames - 1);
+  const sampleFrames = Math.min(Math.max(1, Math.round(rawSampleFrames)), maxFrame + 1);
+
+  if (pinEnd) {
+    const endFrame = Math.min(Math.max(0, clip.endFrame), maxFrame);
+
+    return { ...clip, endFrame, startFrame: Math.max(0, endFrame - (sampleFrames - 1)) };
+  }
+
+  const startFrame = Math.min(Math.max(0, clip.startFrame), maxFrame);
+
+  return { ...clip, endFrame: Math.min(startFrame + sampleFrames - 1, maxFrame), startFrame };
+};
+
 const VIDEO_REFERENCE_CONDITIONINGS = ['video_audio', 'video', 'audio'] as const;
 const VIDEO_REFERENCE_IMAGE_DETAILS = ['max', 'match'] as const;
 
diff --git a/invokeai/frontend/webv2/src/features/video/ui/VideoReferenceListField.tsx b/invokeai/frontend/webv2/src/features/video/ui/VideoReferenceListField.tsx
index 0cb7091a1a8..53ac4f20a8d 100644
--- a/invokeai/frontend/webv2/src/features/video/ui/VideoReferenceListField.tsx
+++ b/invokeai/frontend/webv2/src/features/video/ui/VideoReferenceListField.tsx
@@ -13,7 +13,12 @@ import { useDndContext, useDndMonitor, useDroppable } from '@dnd-kit/core';
 import { galleryItems, galleryTransfers, toGalleryItemKey } from '@features/gallery';
 import { GalleryPickerPopover } from '@features/gallery/picker';
 import { galleryImageUrls, galleryVideoUrls, isGalleryItemDragData } from '@features/gallery/utility';
-import { createVideoSourceClip } from '@features/video/core/settings';
+import {
+  createVideoSourceClip,
+  DEFAULT_REFERENCE_SAMPLE_FRAMES,
+  resizeReferenceSampleWindow,
+  slideReferenceSampleWindow,
+} from '@features/video/core/settings';
 import {
   assertAccountScopeCurrent,
   captureAccountScope,
@@ -22,7 +27,7 @@ import {
 import { Button, IconButton } from '@platform/ui/Button';
 import { DropTargetOverlay } from '@platform/ui/DropTargetOverlay';
 import { DropZone } from '@platform/ui/DropZone';
-import { Field } from '@platform/ui/Field';
+import { Field, FieldLabel } from '@platform/ui/Field';
 import { MiddleTruncate } from '@platform/ui/MiddleTruncate';
 import { Select } from '@platform/ui/Select';
 import { SliderNumberField } from '@platform/ui/SliderNumberField';
@@ -109,28 +114,41 @@ const ReferenceCard = memo(function ReferenceCard({
     },
     [index, onUpdate, reference]
   );
+  // The trim is presented as a sliding sample window — start frame plus length — because
+  // what the user is choosing is "how much" (every reference frame costs denoise VRAM) and
+  // "from where". Storage stays startFrame/endFrame (the request contract); the window
+  // math (constant-length slide that stops at the clip's end, and the extend anchor's
+  // pinned-to-the-cutpoint end) lives in core/settings.
   const handleStartFrame = useCallback(
-    (startFrame: number) => {
+    (rawStart: number) => {
       if (reference.kind === 'video') {
         onUpdate(index, {
           ...reference,
-          clip: { ...reference.clip, endFrame: Math.max(startFrame, reference.clip.endFrame), startFrame },
+          clip: slideReferenceSampleWindow(reference.clip, rawStart, reference.fromSourceVideo === true),
         });
       }
     },
     [index, onUpdate, reference]
   );
-  const handleEndFrame = useCallback(
-    (endFrame: number) => {
+  const handleSampleFrames = useCallback(
+    (rawSampleFrames: number) => {
       if (reference.kind === 'video') {
         onUpdate(index, {
           ...reference,
-          clip: { ...reference.clip, endFrame, startFrame: Math.min(reference.clip.startFrame, endFrame) },
+          clip: resizeReferenceSampleWindow(reference.clip, rawSampleFrames, reference.fromSourceVideo === true),
         });
       }
     },
     [index, onUpdate, reference]
   );
+  // The window's length, and the seconds it represents — the label carries the seconds
+  // because the control is how a user hits a target sample duration (reference frames cost
+  // denoise VRAM every step), while its unit has to stay frames to match the trim contract.
+  const sampleFrames = reference.kind === 'video' ? reference.clip.endFrame - reference.clip.startFrame + 1 : 0;
+  const sampleSeconds =
+    reference.kind === 'video' && Number.isFinite(reference.clip.fps) && reference.clip.fps > 0
+      ? (sampleFrames / reference.clip.fps).toFixed(1)
+      : null;
   const handleMoveUp = useCallback(() => onMove(index, -1), [index, onMove]);
   const handleMoveDown = useCallback(() => onMove(index, 1), [index, onMove]);
   const handleRemove = useCallback(() => onRemove(index), [index, onRemove]);
@@ -163,9 +181,12 @@ const ReferenceCard = memo(function ReferenceCard({
             value={selectValue}
             onValueChange={handleSelect}
           />
-          {/* One row per trim bound: the bound's live frame at left, its slider at
-              right. The seeking thumbs replace the static gallery poster for video
-              references — the start-frame thumb is the card's visual identity. */}
+          {/* One row per window edge: the live frame at left, its control at right. The
+              seeking thumbs replace the static gallery poster for video references — the
+              start-frame thumb is the card's visual identity. The second row's SLIDER is
+              the sample length (the quantity that costs VRAM); its THUMB still shows the
+              resulting end frame, badged with that frame number since the number field
+              beside it shows the length, not the frame. */}
           {reference.kind === 'video' ? (
             <Stack gap="1">
               <HStack gap="2">
@@ -175,36 +196,50 @@ const ReferenceCard = memo(function ReferenceCard({
                   label={t('widgets.video.trimStartShort')}
                   src={galleryVideoUrls.full(name)}
                 />
-                <Box flex="1" minW="0">
+                <Stack flex="1" gap="0.5" minW="0">
+                  <FieldLabel>{t('widgets.video.trimStart')}</FieldLabel>
                   <SliderNumberField
                     ariaLabel={t('widgets.video.trimStart')}
                     disabled={disabled}
                     max={Math.max(0, reference.clip.numFrames - 1)}
                     min={0}
+                    showStepper
                     step={1}
                     value={reference.clip.startFrame}
                     onChange={handleStartFrame}
                   />
-                </Box>
+                </Stack>
               </HStack>
               <HStack gap="2">
                 <TrimBoundThumb
                   fps={reference.clip.fps}
                   frame={reference.clip.endFrame}
-                  label={t('widgets.video.trimEndShort')}
+                  label={`${t('widgets.video.trimEndShort')} · ${reference.clip.endFrame}`}
                   src={galleryVideoUrls.full(name)}
                 />
-                <Box flex="1" minW="0">
+                <Stack flex="1" gap="0.5" minW="0">
+                  <FieldLabel>
+                    {sampleSeconds === null
+                      ? t('widgets.video.sampleLength')
+                      : t('widgets.video.sampleLengthWithSeconds', { seconds: sampleSeconds })}
+                  </FieldLabel>
                   <SliderNumberField
-                    ariaLabel={t('widgets.video.trimEnd')}
+                    ariaLabel={t('widgets.video.sampleLength')}
                     disabled={disabled}
-                    max={Math.max(0, reference.clip.numFrames - 1)}
-                    min={0}
+                    // The anchor grows backward from its pinned end, so its ceiling is the
+                    // available lead-in; ordinary windows grow forward from their start.
+                    max={
+                      reference.fromSourceVideo === true
+                        ? Math.max(1, reference.clip.endFrame + 1)
+                        : Math.max(1, reference.clip.numFrames - reference.clip.startFrame)
+                    }
+                    min={1}
+                    showStepper
                     step={1}
-                    value={reference.clip.endFrame}
-                    onChange={handleEndFrame}
+                    value={sampleFrames}
+                    onChange={handleSampleFrames}
                   />
-                </Box>
+                </Stack>
               </HStack>
             </Stack>
           ) : null}
@@ -388,9 +423,15 @@ export const VideoReferenceListField = memo(function VideoReferenceListField({
         return [
           ...current,
           {
-            // References are truncated to the generated duration, not joined: default to
-            // the whole clip rather than the extend-mode 2-frame-tail trim.
-            clip: { ...clip, endFrame: Math.max(0, clip.numFrames - 1), startFrame: 0 },
+            // Default to a short sample window from the clip's start, not the whole
+            // clip: reference frames cost denoise VRAM every step, and a few seconds
+            // captures the wanted features. (Not the extend-mode 2-frame-tail trim
+            // either -- references are truncated to the generated duration, not joined.)
+            clip: {
+              ...clip,
+              endFrame: Math.max(0, Math.min(DEFAULT_REFERENCE_SAMPLE_FRAMES, clip.numFrames) - 1),
+              startFrame: 0,
+            },
             conditioning: 'video_audio',
             kind: 'video',
           },
diff --git a/invokeai/frontend/webv2/src/features/video/ui/VideoSourceClipField.tsx b/invokeai/frontend/webv2/src/features/video/ui/VideoSourceClipField.tsx
index 865d7efc78f..de197cd2813 100644
--- a/invokeai/frontend/webv2/src/features/video/ui/VideoSourceClipField.tsx
+++ b/invokeai/frontend/webv2/src/features/video/ui/VideoSourceClipField.tsx
@@ -324,6 +324,7 @@ export const VideoSourceClipField = memo(
                       disabled={disabled}
                       max={maxFrameIndex}
                       min={0}
+                      showStepper
                       step={1}
                       value={sourceVideo.startFrame}
                       onChange={setStartFrame}
@@ -343,6 +344,7 @@ export const VideoSourceClipField = memo(
                       disabled={disabled}
                       max={maxFrameIndex}
                       min={0}
+                      showStepper
                       step={1}
                       value={sourceVideo.endFrame}
                       onChange={setEndFrame}