feat(stories): per-clip volume control on the timeline

Each story item now carries a volume column (linear gain, default 1.0,
clamped 0.0–2.0 server-side). New PUT /stories/{}/items/{}/volume route
+ useUpdateStoryItemVolume hook + a Volume2 icon in the clip-edit
toolbar that opens a popover with a 0–200% slider. Local slider state
drives the visual during a drag; the persist fires once on
onValueCommit, mirroring the generation-page slider pattern.

Web Audio playback inserts a per-clip GainNode between source and
master so volume changes apply live without re-decoding the buffer
(source -> clipGain -> masterGain -> destination). Server-side
mixdown in export multiplies the trimmed clip by its volume before
summing into the timeline. Split + duplicate carry the volume forward
to the new clips so trimming a faded section keeps the level you set.

Migration adds the volume column with default 1.0 so existing rows
read as full volume.

app/src/components/StoriesTab/StoryTrackEditor.tsx

@@ -11,6 +11,8 @@ import {
   Scissors,
   Square,
   Trash2,
+  Volume2,
+  VolumeX,
 } from 'lucide-react';
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import WaveSurfer from 'wavesurfer.js';
@@ -21,6 +23,8 @@ import {
   DropdownMenuItem,
   DropdownMenuTrigger,
 } from '@/components/ui/dropdown-menu';
+import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
+import { Slider } from '@/components/ui/slider';
 import { useToast } from '@/components/ui/use-toast';
 import { apiClient } from '@/lib/api/client';
 import type { StoryItemDetail } from '@/lib/api/types';
@@ -31,6 +35,7 @@ import {
   useSetStoryItemVersion,
   useSplitStoryItem,
   useTrimStoryItem,
+  useUpdateStoryItemVolume,
 } from '@/lib/hooks/useStories';
 import { cn } from '@/lib/utils/cn';
 import { useGenerationStore } from '@/stores/generationStore';
@@ -120,6 +125,66 @@ function ClipWaveform({
   );
 }
 
+// Per-clip volume popover. Local state drives the slider during a drag so
+// each pointer-move pixel doesn't fire a PATCH; commits on release.
+function ClipVolumePopover({
+  storyId,
+  itemId,
+  volume,
+  onChange,
+}: {
+  storyId: string;
+  itemId: string;
+  volume: number;
+  onChange: (value: number) => void;
+}) {
+  const [localVolume, setLocalVolume] = useState(volume);
+  // Re-sync when the selected clip changes or the persisted value updates
+  // out-of-band (split/duplicate carry the value forward).
+  useEffect(() => {
+    setLocalVolume(volume);
+  }, [volume, itemId, storyId]);
+
+  const display = Math.round(localVolume * 100);
+  const Icon = localVolume === 0 ? VolumeX : Volume2;
+
+  return (
+    <Popover>
+      <PopoverTrigger asChild>
+        <Button
+          variant="ghost"
+          size="icon"
+          className="h-7 w-7"
+          title={`Volume — ${display}%`}
+          aria-label="Adjust clip volume"
+        >
+          <Icon className="h-4 w-4" />
+        </Button>
+      </PopoverTrigger>
+      <PopoverContent align="center" className="w-56 p-3">
+        <div className="flex items-center justify-between mb-2">
+          <span className="text-xs text-muted-foreground">Volume</span>
+          <span className="text-xs tabular-nums">{display}%</span>
+        </div>
+        <Slider
+          value={[localVolume * 100]}
+          onValueChange={([v]) => setLocalVolume(v / 100)}
+          onValueCommit={([v]) => onChange(v / 100)}
+          min={0}
+          max={200}
+          step={1}
+          aria-label="Clip volume"
+        />
+        <div className="flex justify-between mt-2 text-[10px] text-muted-foreground tabular-nums">
+          <span>0%</span>
+          <span>100%</span>
+          <span>200%</span>
+        </div>
+      </PopoverContent>
+    </Popover>
+  );
+}
+
 interface StoryTrackEditorProps {
   storyId: string;
   items: StoryItemDetail[];
@@ -157,6 +222,7 @@ export function StoryTrackEditor({ storyId, items }: StoryTrackEditorProps) {
   const duplicateItem = useDuplicateStoryItem();
   const removeItem = useRemoveStoryItem();
   const setItemVersion = useSetStoryItemVersion();
+  const updateVolume = useUpdateStoryItemVolume();
   const { toast } = useToast();
   const addPendingGeneration = useGenerationStore((s) => s.addPendingGeneration);
 
@@ -1045,6 +1111,31 @@ export function StoryTrackEditor({ storyId, items }: StoryTrackEditorProps) {
               >
                 <Copy className="h-4 w-4" />
               </Button>
+              {selectedItem && (
+                <ClipVolumePopover
+                  storyId={storyId}
+                  itemId={selectedItem.id}
+                  volume={selectedItem.volume}
+                  onChange={(value) =>
+                    updateVolume.mutate(
+                      {
+                        storyId,
+                        itemId: selectedItem.id,
+                        data: { volume: value },
+                      },
+                      {
+                        onError: (error) => {
+                          toast({
+                            title: 'Failed to update volume',
+                            description: error instanceof Error ? error.message : String(error),
+                            variant: 'destructive',
+                          });
+                        },
+                      },
+                    )
+                  }
+                />
+              )}
               <Button
                 variant="ghost"
                 size="icon"

app/src/lib/api/client.ts

@@ -30,6 +30,7 @@ import type {
   StoryItemSplit,
   StoryItemTrim,
   StoryItemVersionUpdate,
+  StoryItemVolumeUpdate,
   StoryResponse,
   TranscriptionResponse,
   VoiceProfileCreate,
@@ -770,6 +771,17 @@ class ApiClient {
     });
   }
 
+  async updateStoryItemVolume(
+    storyId: string,
+    itemId: string,
+    data: StoryItemVolumeUpdate,
+  ): Promise<StoryItemDetail> {
+    return this.request<StoryItemDetail>(`/stories/${storyId}/items/${itemId}/volume`, {
+      method: 'PUT',
+      body: JSON.stringify(data),
+    });
+  }
+
   async splitStoryItem(
     storyId: string,
     itemId: string,

app/src/lib/api/types.ts

@@ -392,11 +392,16 @@ export interface StoryItemDetail {
   seed?: number;
   instruct?: string;
   engine?: string;
+  volume: number;
   generation_created_at: string;
   versions?: GenerationVersionResponse[];
   active_version_id?: string;
 }
 
+export interface StoryItemVolumeUpdate {
+  volume: number;
+}
+
 export interface StoryItemVersionUpdate {
   version_id: string | null;
 }

app/src/lib/hooks/useStories.ts

@@ -9,6 +9,7 @@ import type {
   StoryItemSplit,
   StoryItemTrim,
   StoryItemVersionUpdate,
+  StoryItemVolumeUpdate,
 } from '@/lib/api/types';
 import { usePlatform } from '@/platform/PlatformContext';
 
@@ -154,6 +155,26 @@ export function useTrimStoryItem() {
   });
 }
 
+export function useUpdateStoryItemVolume() {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({
+      storyId,
+      itemId,
+      data,
+    }: {
+      storyId: string;
+      itemId: string;
+      data: StoryItemVolumeUpdate;
+    }) => apiClient.updateStoryItemVolume(storyId, itemId, data),
+    onSuccess: (_, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['stories'] });
+      queryClient.invalidateQueries({ queryKey: ['stories', variables.storyId] });
+    },
+  });
+}
+
 export function useSplitStoryItem() {
   const queryClient = useQueryClient();
 

app/src/lib/hooks/useStoryPlayback.ts

@@ -264,7 +264,13 @@ export function useStoryPlayback(items: StoryItemDetail[] | undefined) {
 
           const source = audioContext.createBufferSource();
           source.buffer = buffer;
-          source.connect(masterGainRef.current || audioContext.destination);
+          // Per-clip gain so each item can override its level independently
+          // of the master volume. Falls through 1.0 for any item without a
+          // saved value (older rows pre-migration).
+          const clipGain = audioContext.createGain();
+          clipGain.gain.value = typeof item.volume === 'number' ? item.volume : 1;
+          source.connect(clipGain);
+          clipGain.connect(masterGainRef.current || audioContext.destination);
 
           const activeSource: ActiveSource = {
             source,

backend/database/migrations.py

@@ -128,6 +128,8 @@ def _migrate_story_items(engine, inspector, tables: set[str]) -> None:
         _add_column(engine, "story_items", "trim_end_ms INTEGER NOT NULL DEFAULT 0", "trim_end_ms")
     if "version_id" not in columns:
         _add_column(engine, "story_items", "version_id VARCHAR", "version_id")
+    if "volume" not in columns:
+        _add_column(engine, "story_items", "volume FLOAT NOT NULL DEFAULT 1.0", "volume")
 
 
 def _migrate_profiles(engine, inspector, tables: set[str]) -> None:

backend/database/models.py

@@ -105,6 +105,7 @@ class StoryItem(Base):
     track = Column(Integer, nullable=False, default=0)
     trim_start_ms = Column(Integer, nullable=False, default=0)
     trim_end_ms = Column(Integer, nullable=False, default=0)
+    volume = Column(Float, nullable=False, default=1.0)
     created_at = Column(DateTime, default=datetime.utcnow)
 
 

backend/models.py

@@ -598,6 +598,7 @@ class StoryItemDetail(BaseModel):
     seed: Optional[int]
     instruct: Optional[str]
     engine: Optional[str] = None
+    volume: float = 1.0
     generation_created_at: datetime
     # Versions available for this generation
     versions: Optional[List["GenerationVersionResponse"]] = None
@@ -674,6 +675,17 @@ class StoryItemVersionUpdate(BaseModel):
     version_id: Optional[str] = None  # null = use generation default
 
 
+class StoryItemVolumeUpdate(BaseModel):
+    """Request model for adjusting a story item's playback volume.
+
+    Linear gain. ``1.0`` is the original level, ``0.0`` is silent. Capped
+    above 1.0 so a too-aggressive boost can't blow out the mix or clip
+    the export.
+    """
+
+    volume: float = Field(..., ge=0.0, le=2.0)
+
+
 class EffectConfig(BaseModel):
     """A single effect in an effects chain."""
 

backend/routes/stories.py

@@ -151,6 +151,20 @@ async def trim_story_item(
     return item
 
 
+@router.put("/stories/{story_id}/items/{item_id}/volume", response_model=models.StoryItemDetail)
+async def update_story_item_volume(
+    story_id: str,
+    item_id: str,
+    data: models.StoryItemVolumeUpdate,
+    db: Session = Depends(get_db),
+):
+    """Set a story item's per-clip volume (linear gain, 0.0–2.0)."""
+    item = await stories.update_story_item_volume(story_id, item_id, data, db)
+    if item is None:
+        raise HTTPException(status_code=404, detail="Story item not found")
+    return item
+
+
 @router.post("/stories/{story_id}/items/{item_id}/split", response_model=list[models.StoryItemDetail])
 async def split_story_item(
     story_id: str,

backend/services/stories.py

@@ -20,6 +20,7 @@ from ..models import (
     StoryItemBatchUpdate,
     StoryItemMove,
     StoryItemTrim,
+    StoryItemVolumeUpdate,
     StoryItemSplit,
     StoryItemVersionUpdate,
 )
@@ -70,6 +71,7 @@ def _build_item_detail(
         seed=generation.seed,
         instruct=generation.instruct,
         engine=generation.engine,
+        volume=getattr(item, "volume", 1.0),
         generation_created_at=generation.created_at,
         versions=versions,
         active_version_id=active_version_id,
@@ -467,6 +469,37 @@ async def trim_story_item(
     return _build_item_detail(item, generation, profile.name if profile else "Unknown", db)
 
 
+async def update_story_item_volume(
+    story_id: str,
+    item_id: str,
+    data: StoryItemVolumeUpdate,
+    db: Session,
+) -> Optional[StoryItemDetail]:
+    """Update a story item's playback volume (per-clip linear gain)."""
+    item = (
+        db.query(DBStoryItem)
+        .filter_by(id=item_id, story_id=story_id)
+        .first()
+    )
+    if not item:
+        return None
+    generation = db.query(DBGeneration).filter_by(id=item.generation_id).first()
+    if not generation:
+        return None
+
+    item.volume = data.volume
+
+    story = db.query(DBStory).filter_by(id=story_id).first()
+    if story:
+        story.updated_at = datetime.utcnow()
+
+    db.commit()
+    db.refresh(item)
+
+    profile = db.query(DBVoiceProfile).filter_by(id=generation.profile_id).first()
+    return _build_item_detail(item, generation, profile.name if profile else "Unknown", db)
+
+
 async def split_story_item(
     story_id: str,
     item_id: str,
@@ -530,6 +563,7 @@ async def split_story_item(
         track=item.track,
         trim_start_ms=absolute_split_ms,
         trim_end_ms=current_trim_end,
+        volume=getattr(item, "volume", 1.0),
         created_at=datetime.utcnow(),
     )
 
@@ -603,6 +637,7 @@ async def duplicate_story_item(
         track=original_item.track,
         trim_start_ms=current_trim_start,
         trim_end_ms=current_trim_end,
+        volume=getattr(original_item, "volume", 1.0),
         created_at=datetime.utcnow(),
     )
 
@@ -858,6 +893,11 @@ async def export_story_audio(
             else:
                 trimmed_audio = audio[trim_start_sample:]
 
+            # Apply per-clip volume to the export mix.
+            volume = float(getattr(item, "volume", 1.0) or 1.0)
+            if volume != 1.0:
+                trimmed_audio = trimmed_audio * volume
+
             # Store audio with its timecode info
             start_time_ms = item.start_time_ms